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/F0 10/Courier-Bold@0 SF(Internet Engineering Task Force)72 85 Q
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179.998(draft-ietf-tsvwg-quickstart-00.ps S.)72 111 R(Floyd)6 E
(Expires: November 2005)72 124 Q(M. Allman)245.998 E(ICIR)479.998 137 Q
(P. Sarolahti)431.998 150 Q(Nokia Research Center)377.998 163 Q
(31 May 2005)437.998 176 Q/F1 14/Times-Bold@0 SF(Quick-Start f)204.175
201 Q(or TCP and IP)-.35 E/F2 11/Times-Bold@0 SF(Status of this Memo)72
233 Q/F3 11/Times-Roman@0 SF
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492.2 Q(yright \(C\) The Internet Society \(2005\). All Rights Reserv)
-.11 E(ed.)-.165 E F2(Abstract)72 518.2 Q F3(This document speci\214es \
an optional Quick-Start mechanism for transport protocols, in)100.8
544.2 Q(cooperation with routers, to determine an allo)100.8 557.2 Q
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(hile Quick-Start is designed to be used by a range of)-5.5 E
(transport protocols, in this document we describe its use with TCP)
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-.198(TO B)100.8 85 T 2.75(ED).198 G(ELETED BY THE RFC EDIT)-2.75 E
(OR UPON PUBLICA)-.198 E(TION:)-1.221 E
(Changes from draft-amit-quick-start-04.txt:)103.55 98 Q 2.75(*As)103.55
111 S(igni\214cant amount of general editing.)-2.75 E 2.75(*B)103.55 124
S(ecause the Rate Request \214eld only uses four bits, speci\214ed)-2.75
E(that the other four bits are reserv)109.05 137 Q(ed, and talk)-.165 E
(ed about a)-.11 E(possible use for them.)109.05 150 Q
(This is discussed in a ne)5.5 E 2.75(ws)-.275 G(ection on)-2.75 E
("A Rate-Reduced Nonce?")109.05 163 Q 2.75(*S)103.55 176 S
(peci\214ed that a Quick-Start-capable router den)-2.75 E
(ying a request)-.165 E
(SHOULD delete the Quick-Start option, and if this is not)109.05 189 Q
(possible, SHOULD zero the QS TTL and the Rate Request \214elds.)109.05
202 Q 2.75(*M)103.55 215 S(ade the follo)-2.75 E(wing change:)-.275 E
(If the Quick-Start Response is lost)5.5 E(in the netw)109.05 228 Q
(ork, it is not retransmitted.)-.11 E 2.75(*F)103.55 241 S
(or PMTUD, in Section 4.6, added a suggestion to send one lar)-2.915 E
(ge)-.198 E(pack)109.05 254 Q(et in the initial windo)-.11 E 2.75(wf)
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(ets at 576 bytes.)-.11 E 2.75(*A)103.55 280 S
(dded a paragraph to Section 4.6.3 on retransmitted SYN pack)-2.75 E
(ets,)-.11 E(saying the)109.05 293 Q 2.75(ys)-.165 G(hould use an R)
-2.75 E .396 -.198(TO o)-.66 H 2.75(ft).198 G(hree seconds and a ne)
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2.75(Tu)-.44 G(se Quick-Start" after an)-2.75 E
(application-limited period at this time, in Section 4.1, in)109.05 332
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109.05 345 Q(and in)109.05 358 Q -.165(ve)-.44 G(stig).165 E(ation".)
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(dded an appendix on "Possible Router Algorithm".)-2.75 E 2.75(*M)103.55
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(he section on "Quick-Start with DCCP" to the appendix.)-2.75 E 2.75(*N)
103.55 397 S(ame changed from draft-amit-quick-start-04.txt to)-2.75 E
(draft-tsvwg-quickstart-00.txt.)109.05 410 Q
(Changes from draft-amit-quick-start-03.txt:)103.55 436 Q 2.75(*A)103.55
449 S(dded a citation to the paper on "Ev)-2.75 E
(aluating Quick-Start for)-.275 E(TCP", and added pointers to the w)
109.05 462 Q(ork in that paper)-.11 E(.)-.605 E(This w)109.05 475 Q
(ork includes:)-.11 E 2.75(-D)109.05 488 S
(iscussions of router algorithms.)-2.75 E 2.75(-D)109.05 501 S
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(dded sections on "Misbeha)-2.75 E(ving Middlebox)-.22 E
(es", and on "Attacks on)-.165 E(Quick-Start".)109.05 527 Q
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2.75(Connection. The)109.05 579 R(request w)2.75 E
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592 Q 2.75(*C)103.55 605 S
(hanged name "Initial Rate" to "Rate Request", and changed)-2.75 E
(the units from pack)109.05 618 Q(ets per second to bytes per second.)
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(CP: A Quick-Start Request after an Idle Period)-2.75 E 2.75(-T)109.05
722 S(he Quick-Start Mechanisms in DCCP and other T)-2.75 E(ransport)
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(Protocols)114.55 85 Q 2.75(-Q)109.05 98 S(uick-Start with DCCP)-2.75 E
2.75(-I)109.05 111 S(mplementation and Deplo)-2.75 E(yment Issues)-.11 E
2.75(-D)109.05 124 S(esign Decisions)-2.75 E 2.75(*A)103.55 137 S
(dded a discussion of K)-2.75 E(unniyur')-.165 E 2.75(sA)-.605 G
(nti-ECN proposal.)-2.75 E 2.75(*A)103.55 150 S
(dded a section on simulations, with a brief discussion of the)-2.75 E
(simulations by Srikanth Sundarrajan.)109.05 163 Q
(Changes from draft-amit-quick-start-01.txt:)103.55 189 Q 2.75(*A)103.55
202 S(dded a discussion in the related w)-2.75 E(ork section about the)
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(ge initial windo)-.198 E -.715(w,)-.275 G(without e)109.05 228 Q
(xplicit permission of routers.)-.165 E 2.75(*A)103.55 241 S
(dded a discussion in the related w)-2.75 E(ork section about the)-.11 E
(tradeof)109.05 254 Q(fs of XCP vs. Quick-Start.)-.275 E 2.75(*A)103.55
267 S(dded a section on "The Quick-Start Request: P)-2.75 E(ack)-.165 E
(ets or Bytes?")-.11 E(Changes from draft-amit-quick-start-00.txt:)
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 13
/Times-Bold@0 SF -1.196(Ta)253.526 85 S(ble of Contents)1.196 E/F2 10
/Times-Roman@0 SF(1. Introduction)100.8 110 Q F0 11
(.......................)11.01 G F2(7)11.5 E
(2. Assumptions and General Principles)100.8 122 Q F0 11
(................)10.88 G F2(8)11.5 E(2.1. Ov)115.8 134 Q(ervie)-.15 E
2.5(wo)-.25 G 2.5(fQ)-2.5 G(uick-Start)-2.5 E F0 11(..................)
7.68 G F2(9)11.5 E(3. The Quick-Start Request in IP)100.8 146 Q F0 11
(..................)8.1 G F2(11)6.5 E
(3.1. The Quick-Start Request Option for IPv4)115.8 158 Q F0 11
(.............)10.19 G F2(11)6.5 E
(3.2. The Quick-Start Request Option for IPv6)115.8 170 Q F0 11
(.............)10.19 G F2(13)6.5 E
(3.3. Processing the Quick-Start Request at Routers)115.8 182 Q F0 11
(............)3.94 G F2(13)6.5 E
(3.4. Deciding the Permitted Rate Request at a Router)115.8 194 Q F0 11
(...........)8.25 G F2(14)6.5 E(3.5. Quick-Start in IP T)115.8 206 Q
(unnels)-.45 E F0 11(..................)4.1 G F2(15)6.5 E
(3.6. A Rate-Reduced Nonce?)115.8 218 Q F0 11(..................)7.29 G
F2(16)6.5 E(4. The Quick-Start Mechanisms in TCP)100.8 230 Q F0 11
(................)7.82 G F2(17)6.5 E(4.1. When to Use Quick-Start)115.8
242 Q F0 11(..................)5.33 G F2(18)6.5 E
(4.2. The Quick-Start Response Option in the TCP header)115.8 254 Q F0
11(..........)5.89 G F2(19)6.5 E
(4.3. TCP: Sending the Quick-Start Response)115.8 266 Q F0 11
(..............).59 G F2(19)6.5 E(4.4. TCP: Recei)115.8 278 Q
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(4.6.1. Determining the Rate to Request)130.8 314 Q F0 11
(..............)8.1 G F2(21)6.5 E(4.6.2. Interactions with P)130.8 326 Q
(ath MTU Disco)-.15 E -.15(ve)-.15 G(ry).15 E F0 11(............)11.06 G
F2(22)6.5 E(4.6.3. Quick-Start Request P)130.8 338 Q(ack)-.15 E
(ets that are Discarded by Middlebox)-.1 E(es)-.15 E F0 11(.....)6.45 G
F2(22)6.5 E(4.7. TCP: A Quick-Start Request in the Middle of Connection)
115.8 350 Q F0 11(........)13.65 G F2(23)6.5 E
(4.8. An Example Quick-Start Scenario with TCP)115.8 362 Q F0 11
(............)11.16 G F2(24)6.5 E
(5. The Quick-Start Mechanism in other T)100.8 374 Q(ransport Protocols)
-.35 E F0 11(..........)10.69 G F2(24)6.5 E(6. Ev)100.8 386 Q
(aluation of Quick-Start)-.25 E F0 11(...................)12.38 G F2(25)
6.5 E(6.1. Bene\214ts of Quick-Start)115.8 398 Q F0 11
(...................).18 G F2(25)6.5 E(6.2. Costs of Quick-Start)115.8
410 Q F0 11(...................)10.73 G F2(25)6.5 E(6.3. Protection ag)
115.8 422 Q(ainst Misbeha)-.05 E(ving Nodes)-.2 E F0 11(..............)
7.24 G F2(27)6.5 E(6.3.1. Recei)130.8 434 Q -.15(ve)-.25 G(rs L).15 E
(ying about Whether the Request w)-.55 E(as Appro)-.1 E -.15(ve)-.15 G
(d).15 E F0 11(......)13.1 G F2(27)6.5 E(6.3.2. Recei)130.8 446 Q -.15
(ve)-.25 G(rs L).15 E(ying about the Appro)-.55 E -.15(ve)-.15 G 2.5(dR)
.15 G(ate)-2.5 E F0 11(...........)13.12 G F2(27)6.5 E
(6.3.3. Collusion between Misbeha)130.8 458 Q(ving Routers)-.2 E F0 11
(............)3.85 G F2(28)6.5 E(6.3.4. Misbeha)130.8 470 Q
(ving Middlebox)-.2 E(es and the IP TTL)-.15 E F0 11(...........)9.98 G
F2(29)6.5 E(6.4. Quick-Start with QoS-enabled T)115.8 482 Q(raf)-.35 E
<8c63>-.25 E F0 11(..............)10.94 G F2(29)6.5 E
(6.5. Limitations of Quick-Start)115.8 494 Q F0 11(..................)
.59 G F2(29)6.5 E(6.6. Attacks on Quick-Start)115.8 506 Q F0 11
(...................).74 G F2(30)6.5 E
(6.7. Simulations with Quick-Start)115.8 518 Q F0 11(.................)
3.22 G F2(30)6.5 E(7. Related W)100.8 530 Q(ork)-.8 E F0 11
(.......................)5.43 G F2(31)6.5 E(7.1. F)115.8 542 Q
(ast Start-ups without Explicit Information from Routers)-.15 E F0 11
(.........)2.27 G F2(31)6.5 E
(7.2. Optimistic Sending without Explicit Information from Routers)115.8
554 Q F0 11(.......)7.39 G F2(32)6.5 E(7.3. F)115.8 566 Q
(ast Start-ups with other Information from Routers)-.15 E F0 11
(..........)12.42 G F2(32)6.5 E(7.4. F)115.8 578 Q
(ast Start-ups with more Fine-Grained Feedback from Routers)-.15 E F0 11
(.......)7.3 G F2(33)6.5 E(8. Implementation and Deplo)100.8 590 Q
(yment Issues)-.1 E F0 11(...............)11.4 G F2(33)6.5 E
(8.1. Implementation Issues for Sending Quick-Start Requests)115.8 602 Q
F0 11(.........)2.97 G F2(33)6.5 E
(8.2. Implementation Issues for Processing Quick-Start Requests)115.8
614 Q F0 11(........)6.17 G F2(34)6.5 E(8.3. Possible Deplo)115.8 626 Q
(yment Scenarios)-.1 E F0 11(................)7.64 G F2(34)6.5 E(8.4. W)
115.8 638 Q(ould QuickStart pack)-.8 E(ets tak)-.1 E 2.5(et)-.1 G
(he slo)-2.5 E 2.5(wp)-.25 G(ath in routers?)-2.5 E F0 11(.........)6.18
G F2(35)6.5 E(8.5. A Comparison with the Deplo)115.8 650 Q
(yment Problems of ECN)-.1 E F0 11(.........)11.39 G F2(35)6.5 E
(9. Security Considerations)100.8 662 Q F0 11(....................)5.87
G F2(36)6.5 E(10. Conclusions)100.8 674 Q F0 11(.......................)
6 G F2(36)6.5 E(11. Ackno)100.8 686 Q(wledgements)-.25 E F0 11
(.....................)3.77 G F2(36)6.5 E(A. Design Decisions)100.8 698
Q F0 11(......................)1.71 G F2(36)6.5 E
(A.1. Alternate Mechanisms for the Quick-Start Request: ICMP and RSVP)
115.8 710 Q F0 11(.....)6.03 G F2(37)6.5 E(A.1.1. ICMP)130.8 722 Q F0 11
(......................)2.53 G F2(37)6.5 E F0(Jain/Flo)72 769 Q 267.275
(yd/Allman/Sarolahti [P)-.11 F(age 5])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 10
/Times-Roman@0 SF(A.1.2. RSVP)130.8 84 Q F0 11(......................)
1.97 G F1(38)6.5 E(A.2. Alternate Encoding Functions)115.8 96 Q F0 11
(................)11.99 G F1(38)6.5 E(A.3. The Quick-Start Request: P)
115.8 108 Q(ack)-.15 E(ets or Bytes?)-.1 E F0 11(............)11.42 G F1
(39)6.5 E(A.4. Quick-Start Semantics: T)115.8 120 Q
(otal Rate or Additional Rate?)-.8 E F0 11(.........)10.16 G F1(40)6.5 E
(A.5. Alternate Responses to the Loss of a Quick-Start P)115.8 132 Q
(ack)-.15 E(et)-.1 E F0 11(.........)4.07 G F1(41)6.5 E(A.6. Wh)115.8
144 Q 2.5(yN)-.05 G(ot Include More Functionality?)-2.5 E F0 11
(..............)5.66 G F1(42)6.5 E(A.7. The Earlier QuickStart Nonce)
115.8 156 Q F0 11(................)12.29 G F1(44)6.5 E
(B. Quick-Start with DCCP)100.8 168 Q F0 11(....................)4.47 G
F1(45)6.5 E(C. Possible Router Algorithm)100.8 180 Q F0 11
(...................)6.55 G F1(46)6.5 E(Normati)100.8 192 Q .3 -.15
(ve R)-.25 H(eferences).15 E F0 11(.....................)8.66 G F1(48)
6.5 E(Informati)100.8 204 Q .3 -.15(ve R)-.25 H(eferences).15 E F0 11
(.....................)4.22 G F1(48)6.5 E(IAN)100.8 216 Q 2.5(AC)-.35 G
(onsiderations)-2.5 E F0 11(.....................)10.81 G F1(51)6.5 E
(IP Option)100.8 228 Q F0 11(.........................)3.78 G F1(51)6.5
E(TCP Option)100.8 240 Q F0 11(........................)8.08 G F1(51)6.5
E -.55(AU)100.8 252 S(THORS' ADDRESSES).55 E F0 11(....................)
1.97 G F1(51)6.5 E(Full Cop)100.8 264 Q(yright Statement)-.1 E F0 11
(....................)10.12 G F1(52)6.5 E(Intellectual Property)100.8
276 Q F0 11(......................)2.27 G F1(52)6.5 E F0(Jain/Flo)72 769
Q 267.275(yd/Allman/Sarolahti [P)-.11 F(age 6])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Times-Bold@0 SF(1.)72 85 Q/F2 14/Times-Bold@0 SF(Intr)5.5 E(oduction)
-.252 E F0(Each TCP connection be)100.8 111 Q
(gins with a question: "What is the appropriate sending rate for the)
-.165 E(current netw)100.8 124 Q(ork path?")-.11 E
(The question is not answered e)5.5 E(xplicitly for TCP)-.165 E 2.75(,b)
-1.221 G(ut each TCP)-2.97 E
(connection determines the sending rate by probing the netw)100.8 137 Q
(ork path and altering the)-.11 E(congestion windo)100.8 150 Q 2.75(w\()
-.275 G(cwnd\) based on percei)-2.75 E -.165(ve)-.275 G 2.75(dc).165 G
2.75(ongestion. Each)-2.75 F(connection starts with a)2.75 E
(pre-con\214gured initial congestion windo)100.8 163 Q 2.75(w\()-.275 G
2.75(ICW\). Currently)-2.75 F 2.75(,T)-.715 G(CP allo)-2.75 E
(ws an initial windo)-.275 E(w)-.275 E
(of between one and four MSS-sized se)100.8 176 Q
(gments [RFC2581,RFC3390].)-.165 E(The TCP connection)5.5 E
(then probes the netw)100.8 189 Q(ork for a)-.11 E -.275(va)-.22 G
(ilable bandwidth using the slo).275 E(w-start procedure)-.275 E([Jac88\
,RFC2581], doubling cwnd during each congestion-free round-trip time \(\
R)100.8 202 Q(TT\).)-.66 E(The slo)100.8 228 Q
(w-start algorithm can be time-consuming --- especially o)-.275 E -.165
(ve)-.165 G 2.75(rn).165 G(etw)-2.75 E(orks with lar)-.11 E(ge)-.198 E
(bandwidth or long delays.)100.8 241 Q(It may tak)5.5 E 2.75(ean)-.11 G
(umber of R)-2.75 E(TTs in slo)-.66 E(w-start before the TCP)-.275 E
(connection be)100.8 254 Q(gins to fully use the a)-.165 E -.275(va)-.22
G(ilable bandwidth of the netw).275 E 2.75(ork. F)-.11 F
(or instance, it)-.165 E(tak)100.8 267 Q
(es log_2\(N\) - 2 round-trip times to b)-.11 E(uild cwnd up to N se)
-.22 E(gments, assuming an initial)-.165 E(congestion windo)100.8 280 Q
2.75(wo)-.275 G 2.75(f4s)-2.75 G -.165(eg)-2.75 G 2.75(ments. This).165
F(time in slo)2.75 E(w-start is not a problem for lar)-.275 E(ge \214le)
-.198 E(transfers, where the slo)100.8 293 Q
(w-start stage is only a fraction of the total transfer time.)-.275 E
(Ho)5.5 E(we)-.275 E -.165(ve)-.275 G -.44(r,).165 G(in the case of mod\
erate-sized transfers the connection might carry out its entire transfe\
r in)100.8 306 Q(the slo)100.8 319 Q(w-start phase, taking man)-.275 E
2.75(yr)-.165 G(ound-trip times, where one or tw)-2.75 E 2.75(oR)-.11 G
(TTs might ha)-3.41 E -.165(ve)-.22 G
(been appropriate in the current netw)100.8 332 Q(ork conditions.)-.11 E
2.75(Af)100.8 358 S(air amount of w)-2.86 E
(ork has already been done to address the issue of choosing the initial)
-.11 E(congestion windo)100.8 371 Q 2.75(wf)-.275 G(or TCP)-2.75 E 2.75
(,w)-1.221 G(ith RFC 3390 allo)-2.75 E(wing an initial windo)-.275 E
2.75(wo)-.275 G 2.75(fu)-2.75 G 2.75(pt)-2.75 G 2.75(of)-2.75 G(our)
-2.75 E(se)100.8 384 Q
(gments based on the MSS used by the connection [RFC3390].)-.165 E
(Our underlying premise)5.5 E(is that e)100.8 397 Q
(xplicit feedback from all of the routers along the path w)-.165 E
(ould be required, in the)-.11 E(current architecture, for best-ef)100.8
410 Q(fort connections to use initial windo)-.275 E
(ws signi\214cantly lar)-.275 E(ger)-.198 E(than those allo)100.8 423 Q
(wed by [RFC3390], in the absence of other information about the path.)
-.275 E(The Congestion Manager [RFC3124] and TCP control block sharing \
[RFC2140] both)100.8 449 Q(propose sharing congestion information among\
 multiple TCP connections with the same)100.8 462 Q 2.75(endpoints. W)
100.8 475 R(ith the Congestion Manager)-.44 E 2.75(,an)-.44 G .55 -.275
(ew T)-2.75 H(CP connection could start with a high).275 E
(initial cwnd if it w)100.8 488 Q
(as sharing the path and the cwnd with a pre-e)-.11 E
(xisting TCP connection to)-.165 E
(the same destination that had already obtained a high congestion windo)
100.8 501 Q 4.18 -.715(w. R)-.275 H(FC 2140).715 E
(discusses ensemble sharing, where an established connection')100.8 514
Q 2.75(sc)-.605 G(ongestion windo)-2.75 E 2.75(wc)-.275 G(ould)-2.75 E
(be `di)100.8 527 Q(vided up' to be shared with a ne)-.275 E 2.75(wc)
-.275 G(onnection to the same host.)-2.75 E(Ho)5.5 E(we)-.275 E -.165
(ve)-.275 G .88 -.44(r, n).165 H(either of).44 E
(these approaches addresses the case of a connection to a ne)100.8 540 Q
2.75(wd)-.275 G(estination, with no e)-2.75 E(xisting)-.165 E(or recent\
 connection \(and therefore congestion control state\) to that destinat\
ion.)100.8 553 Q(Quick-Start w)100.8 579 Q
(ould not be the \214rst mechanism for e)-.11 E
(xplicit communication from routers to)-.165 E
(transport protocols about sending rates.)100.8 592 Q
(Explicit Congestion Noti\214cation \(ECN\) gi)5.5 E -.165(ve)-.275 G(s)
.165 E -.165(ex)100.8 605 S(plicit congestion control feedback from rou\
ters to transport protocols, based on the).165 E
(router detecting congestion before b)100.8 618 Q(uf)-.22 E(fer o)-.275
E -.165(ve)-.165 G(r\215o).165 E 2.75(w[)-.275 G 2.75(RFC3168]. In)-2.75
F(contrast, routers w)2.75 E(ould)-.11 E
(not use Quick-Start to get congestion information, b)100.8 631 Q
(ut instead w)-.22 E(ould use Quick-Start as an)-.11 E
(optional mechanism to gi)100.8 644 Q .33 -.165(ve p)-.275 H
(ermission to transport protocols to use higher sending rates,).165 E(b\
ased on the ability of all the routers along the path to determine if t\
heir respecti)100.8 657 Q .33 -.165(ve o)-.275 H(utput).165 E
(links are signi\214cantly underutilized.)100.8 670 Q(Jain/Flo)72 769 Q
217.775(yd/Allman/Sarolahti Section)-.11 F 2.75(1. [P)2.75 F(age 7])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Times-Bold@0 SF(2.)72 85 Q/F2 14/Times-Bold@0 SF
(Assumptions and General Principles)5.5 E F0(This section describes the\
 assumptions and general principles behind the design of the)100.8 111 Q
(Quick-Start mechanism.)100.8 124 Q(Assumptions:)100.8 150 Q 2.75(*T)
100.8 176 S(he data transfer in the tw)-2.75 E 2.75(od)-.11 G
(irections of a connection tra)-2.75 E -.165(ve)-.22 G(rses dif).165 E
(ferent queues, and)-.275 E(possibly e)100.8 189 Q -.165(ve)-.275 G 2.75
(nd).165 G(if)-2.75 E(ferent routers.)-.275 E(Thus, an)5.5 E 2.75(ym)
-.165 G(echanism for determining the allo)-2.75 E(wed sending)-.275 E
(rate w)100.8 202 Q(ould ha)-.11 E .33 -.165(ve t)-.22 H 2.75(ob).165 G
2.75(eu)-2.75 G(sed independently for each direction.)-2.75 E 2.75(*T)
100.8 228 S(he path between the tw)-2.75 E 2.75(oe)-.11 G
(ndpoints is relati)-2.75 E -.165(ve)-.275 G
(ly stable, such that the path used by the).165 E(Quick-Start request i\
s generally the same path used by the Quick-Start pack)100.8 241 Q
(ets one round-)-.11 E(trip time later)100.8 254 Q 5.5(.[)-.605 G
(ZPS00] sho)-5.5 E(ws this assumption should be generally v)-.275 E
(alid.)-.275 E 2.75(*A)100.8 280 S .33 -.165(ny n)-2.75 H .55 -.275
(ew m).165 H(echanism must be incrementally deplo).275 E
(yable, and might not be supported by)-.11 E
(all of the routers and/or end-hosts.)100.8 293 Q(Thus, an)5.5 E 2.75
(yn)-.165 G .55 -.275(ew m)-2.75 H(echanism must be able to).275 E(acco\
mmodate non-supporting routers or end-hosts without disturbing the curr\
ent Internet)100.8 306 Q(semantics.)100.8 319 Q(General Principles:)
100.8 345 Q 2.75(*O)100.8 371 S(ur underlying premise is that e)-2.75 E
(xplicit feedback from all of the routers along the path)-.165 E -.11
(wo)100.8 384 S
(uld be required, in the current architecture, for best-ef).11 E
(fort connections to use initial)-.275 E(windo)100.8 397 Q
(ws signi\214cantly lar)-.275 E(ger than those allo)-.198 E
(wed by [RFC3390], in the absence of other)-.275 E
(information about the path.)100.8 410 Q 2.75(*Ar)100.8 436 S
(outer should only appro)-2.75 E .33 -.165(ve a r)-.165 H
(equest for a higher sending rate if the output link is).165 E 2.75
(underutilized. An)100.8 449 R 2.75(yo)-.165 G
(ther approach will result in either per)-2.75 E(-\215o)-.22 E 2.75(ws)
-.275 G(tate at the router)-2.75 E 2.75(,o)-.44 G 2.75(rt)-2.75 G(he)
-2.75 E(possibility of a \(possibly transient\) queue at the router)
100.8 462 Q(.)-.605 E 2.75(*N)100.8 488 S 2.75(op)-2.75 G(er)-2.75 E
(-\215o)-.22 E 2.75(ws)-.275 G(tate should be required at the router)
-2.75 E 5.5(.N)-.605 G(ote that while per)-5.5 E(-\215o)-.22 E 2.75(ws)
-.275 G(tate is not)-2.75 E
(required we also do not preclude a router from storing per)100.8 501 Q
(-\215o)-.22 E 2.75(ws)-.275 G(tate for making Quick-)-2.75 E
(Start decisions.)100.8 514 Q(There are also a number of questions re)
100.8 540 Q -.055(ga)-.165 G(rding the Quick-Start mechanism that are)
.055 E(discussed later in this document.)100.8 553 Q(Open Questions:)
100.8 579 Q 2.75(*W)100.8 605 S
(ould the bene\214ts of the Quick-Start mechanism be w)-3.63 E
(orth the added comple)-.11 E(xity?)-.165 E(The bene\214ts and dra)100.8
631 Q
(wbacks of Quick-Start are discussed in more detail in Section 6 on)
-.165 E("Ev)100.8 644 Q(aluation of Quick-Start".)-.275 E 2.75(*O)100.8
670 S(ne practical consideration is that pack)-2.75 E(ets with kno)-.11
E(wn and unkno)-.275 E(wn IP options are often)-.275 E
(dropped in the current Internet [MAF04].)100.8 683 Q
(This does not preclude using Quick-Start in Intranets.)100.8 709 Q
(Further)5.5 E 2.75(,[)-.44 G(MAF04] also sho)-2.75 E(ws that)-.275 E
-.165(ove)100.8 722 S 2.75(rt).165 G(ime the blocking of pack)-2.75 E
(ets ne)-.11 E(gotiating ECN has become less common, and therefore)-.165
E(Jain/Flo)72 769 Q 217.775(yd/Allman/Sarolahti Section)-.11 F 2.75
(2. [P)2.75 F(age 8])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(an incremental deplo)100.8 85 Q
(yment story for Quick-Start based on IP Options is not out of the)-.11
E 2.75(question. Appendix)100.8 98 R
(A.1 on "Alternate Mechanisms for the Quick-Start Request" discusses)
2.75 E(the possibility of using RSVP or ICMP instead of IP Options for \
carrying Quick-Start)100.8 111 Q(Requests to routers.)100.8 124 Q 2.75
(*As)100.8 150 S(econd practical consideration is that pack)-2.75 E
(ets could be dropped at non-IP queues along)-.11 E(the path.)100.8 163
Q(This is discussed in more detail in Section 6.2.)100.8 189 Q 2.75(*A)
5.5 G(part from the merits and shortcomings)-2.75 E
(of the Quick-Start mechanism, is there lik)100.8 202 Q
(ely to be a compelling need to add e)-.11 E(xplicit)-.165 E
(congestion-related feedback from routers o)100.8 215 Q -.165(ve)-.165 G
2.75(ra).165 G(nd abo)-2.75 E .33 -.165(ve t)-.165 H
(he one-bit feedback from ECN?).165 E(If the answer to the question abo)
100.8 241 Q .33 -.165(ve i)-.165 H 2.75(sy).165 G
(es, should we be considering w)-2.75 E(ays to incorporate)-.11 E
(Quick-Start in mechanisms that, while more comple)100.8 254 Q
(x, are also suf)-.165 E(\214ciently more po)-.275 E(werful)-.275 E(tha\
n Quick-Start, or should Quick-Start be considered as orthogonal to suc\
h mechanisms?)100.8 267 Q
(This is discussed further in Appendix A.6 on "Wh)100.8 280 Q 2.75(yN)
-.055 G(ot Include More Functionality".)-2.75 E/F1 11/Times-Bold@0 SF
(2.1.)72 319 Q/F2 13/Times-Bold@0 SF(Ov)5.5 E(er)-.13 E
(view of Quick-Start)-.13 E F0(In this section we gi)100.8 345 Q .33
-.165(ve a)-.275 H 2.75(no).165 G -.165(ve)-2.915 G(rvie).165 E 2.75(wo)
-.275 G 2.75(ft)-2.75 G(he use of Quick-Start with TCP)-2.75 E 2.75(,t)
-1.221 G 2.75(or)-2.75 G(equest a higher)-2.75 E(congestion windo)100.8
358 Q 4.18 -.715(w. T)-.275 H
(he description in this section is non-normati).715 E -.165(ve)-.275 G
2.75(;t).165 G(he normati)-2.75 E -.165(ve)-.275 G
(description of Quick-Start with IP and TCP follo)100.8 371 Q
(ws in Sections 3 and 4. Quick-Start can be)-.275 E(used in the middle \
of a connection, e.g., after an idle or underutilized period, as well a\
s for)100.8 384 Q(the initial sending rate; these uses of Quick-Start a\
re discussed later in the document.)100.8 397 Q
(Quick-Start requires end-points and routers to w)100.8 423 Q
(ork together)-.11 E 2.75(,w)-.44 G(ith end-points requesting a)-2.75 E
(higher sending rate in the Quick-Start Request \(QSR\) option in IP)
100.8 436 Q 2.75(,a)-1.221 G(nd routers along the)-2.75 E(path appro)
100.8 449 Q
(ving, modifying, discarding or ignoring \(and therefore disallo)-.165 E
(wing\) the Quick-)-.275 E(Start Request.)100.8 462 Q(The recei)5.5 E
-.165(ve)-.275 G 2.75(ru).165 G(ses reliable, transport-le)-2.75 E -.165
(ve)-.275 G 2.75(lm).165 G(echanisms to inform the sender)-2.75 E
(of the status of the Quick-Start Request.)100.8 475 Q
(In addition, Quick-Start assumes a unicast,)5.5 E(congestion-controlle\
d transport protocol; we do not consider the use of Quick-Start for)
100.8 488 Q(multicast traf)100.8 501 Q(\214c.)-.275 E(The Quick-Start R\
equest Option includes a request for a sending rate in bytes per second\
,)100.8 527 Q(and a Quick-Start TTL \(QS TTL\) to be decremented by e)
100.8 540 Q -.165(ve)-.275 G(ry router along the path that).165 E
(understands the option and appro)100.8 553 Q -.165(ve)-.165 G 2.75(st)
.165 G(he request.)-2.75 E(The Quick-Start TTL is initialized by the)5.5
E(sender to a random v)100.8 566 Q 2.75(alue. The)-.275 F
(transport recei)2.75 E -.165(ve)-.275 G 2.75(rr).165 G
(eturns the rate and information about the)-2.75 E
(TTL to the sender using transport-le)100.8 579 Q -.165(ve)-.275 G 2.75
(lm).165 G 2.75(echanisms. In)-2.75 F(particular)2.75 E 2.75(,t)-.44 G
(he recei)-2.75 E -.165(ve)-.275 G 2.75(rc).165 G(omputes)-2.75 E
(the dif)100.8 592 Q(ference between the Quick-Start TTL and the IP TTL\
 \(the TTL in the IP header\) of)-.275 E(the Quick-Start request pack)
100.8 605 Q(et, and returns this in the Quick-Start response.)-.11 E
(The sender)5.5 E(uses this information to determine if all of the rout\
ers along the path decremented the)100.8 618 Q(Quick-Start TTL, appro)
100.8 631 Q(ving the Quick-Start Request.)-.165 E
(If the request is appro)100.8 657 Q -.165(ve)-.165 G 2.75(db).165 G
2.75(ya)-2.75 G(ll of the routers along the path, then the TCP sender)
-2.75 E(combines this allo)100.8 670 Q
(wed rate with the measurement of the round-trip time, and ends up with)
-.275 E(an allo)100.8 683 Q(wed TCP congestion windo)-.275 E 4.18 -.715
(w. T)-.275 H(his windo).715 E 2.75(wi)-.275 G 2.75(ss)-2.75 G
(ent rate-paced o)-2.75 E -.165(ve)-.165 G 2.75(rt).165 G(he ne)-2.75 E
(xt round-)-.165 E(trip time, or until an A)100.8 696 Q(CK pack)-.44 E
(et is recei)-.11 E -.165(ve)-.275 G(d.).165 E(Figure 1 sho)100.8 722 Q
(ws a successful use of Quick-Start, with both routers along the path a\
ppro)-.275 E(ving)-.165 E(Jain/Flo)72 769 Q 209.525
(yd/Allman/Sarolahti Section)-.11 F 2.75(2.1. [P)2.75 F(age 9])-.165 E 0
Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(the Quick-Start Request.)100.8 85 Q(In this e)5.5 E
(xample, Quick-Start is used by TCP to establish the)-.165 E
(initial congestion windo)100.8 98 Q -.715(w.)-.275 G/F1 11/Courier@0 SF
46.2(Sender Router)120.6 130 R 46.2(1R)6.6 G(outer 2)-46.2 E(Receiver)66
E 46.2(------ --------)120.6 143 R 59.4(-------- --------)46.2 F 6.6(|<)
107.4 156 S(IP TTL: 63>)-6.6 E 6.6(|<)107.4 169 S(QS TTL: 91>)-6.6 E 6.6
(|<)107.4 182 S(TTL Diff: 28>)-6.6 E 6.6(|Q)107.4 195 S
(uick-Start Request)-6.6 E 6.6(|i)107.4 208 S 6.6(nS)-6.6 G
(YN or SYN/ACK -->)-6.6 E(|)107.4 221 Q 99(|D)107.4 234 S(ecrement)-99 E
99(|Q)107.4 247 S 6.6(ST)-99 G(TL)-6.6 E 99(|t)107.4 260 S 6.6(oa)-99 G
(pprove)-6.6 E 99(|r)107.4 273 S(equest -->)-99 E(|)107.4 286 Q 198(|D)
107.4 299 S(ecrement)-198 E 198(|Q)107.4 312 S 6.6(ST)-198 G(TL)-6.6 E
198(|t)107.4 325 S 6.6(oa)-198 G(pprove)-6.6 E 198(|r)107.4 338 S
(equest -->)-198 E(|)107.4 351 Q 283.8(|<)107.4 364 S(IP TTL: 61>)-283.8
E 283.8(|<)107.4 377 S(QS TTL: 89>)-283.8 E 283.8(|<)107.4 390 S
(TTL Diff: 28>)-283.8 E 283.8(|R)107.4 403 S(eturn Quick-Start)-283.8 E
290.4(|i)107.4 416 S(nfo to sender in)-290.4 E 277.2(|<)107.4 429 S
(-- TCP ACK packet.)-277.2 E(|)107.4 442 Q 6.6(|<)107.4 455 S
(TTL Diff: 28>)-6.6 E 6.6(|Q)107.4 468 S(uick-Start approved,)-6.6 E 6.6
(|t)107.4 481 S(ranslate to cwnd.)-6.6 E 6.6(VS)107.4 494 S
(end cwnd paced over one RTT. -->)-6.6 E
(Figure 1: A successful Quick-Start Request.)173.4 520 Q F0
(Figure 2 sho)100.8 552 Q(ws an unsuccessful use of Quick-Start, with o\
ne of the routers along the path)-.275 E(not appro)100.8 565 Q
(ving the Quick-Start Request.)-.165 E
(If the Quick-Start Request is not appro)5.5 E -.165(ve)-.165 G(d, then)
.165 E(the sender uses the def)100.8 578 Q
(ault congestion control mechanisms for that transport protocol,)-.11 E
(including the def)100.8 591 Q(ault initial congestion windo)-.11 E 1.43
-.715(w, r)-.275 H(esponse to idle periods, etc.).715 E(Jain/Flo)72 769
Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75(2.1. [P)2.75 F
(age 10])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Courier@0 SF 46.2(Sender Router)120.6 85 R 46.2(1R)6.6 G(outer 2)-46.2
E(Receiver)66 E 46.2(------ --------)120.6 98 R 59.4(-------- --------)
46.2 F 6.6(|<)107.4 111 S(IP TTL: 63>)-6.6 E 6.6(|<)107.4 124 S
(QS TTL: 91>)-6.6 E 6.6(|<)107.4 137 S(TTL Diff: 28>)-6.6 E 6.6(|Q)107.4
150 S(uick-Start Request)-6.6 E 6.6(|i)107.4 163 S 6.6(nS)-6.6 G
(YN or SYN/ACK -->)-6.6 E(|)107.4 176 Q 99(|D)107.4 189 S(ecrement)-99 E
99(|Q)107.4 202 S 6.6(ST)-99 G(TL)-6.6 E 99(|t)107.4 215 S 6.6(oa)-99 G
(pprove)-6.6 E 99(|r)107.4 228 S(equest -->)-99 E(|)107.4 241 Q 198(|F)
107.4 254 S(orward packet)-198 E 198(|w)107.4 267 S(ithout modifying)
-198 E 198(|Q)107.4 280 S(uick-Start Option. -->)-198 E(|)107.4 293 Q
283.8(|<)107.4 306 S(IP TTL: 61>)-283.8 E 283.8(|<)107.4 319 S
(QS TTL: 90>)-283.8 E 283.8(|<)107.4 332 S(TTL Diff: 29>)-283.8 E 283.8
(|R)107.4 345 S(eturn Quick-Start)-283.8 E 290.4(|i)107.4 358 S
(nfo to sender in)-290.4 E 277.2(|<)107.4 371 S(-- TCP ACK packet.)
-277.2 E(|)107.4 384 Q 6.6(|<)107.4 397 S(TTL Diff: 29>)-6.6 E 6.6(|Q)
107.4 410 S(uick-Start not approved.)-6.6 E 6.6(VU)107.4 423 S
(se default initial cwnd. -->)-6.6 E
(Figure 2: An unsuccessful Quick-Start Request.)173.4 449 Q/F2 11
/Times-Bold@0 SF(3.)72 494 Q/F3 14/Times-Bold@0 SF
(The Quick-Start Request in IP)5.5 E F2(3.1.)72 533 Q/F4 13/Times-Bold@0
SF(The Quick-Start Request Option f)5.5 E(or IPv4)-.325 E F0
(The Quick-Start Request for IPv4 is de\214ned as follo)100.8 559 Q(ws:)
-.275 E F1 92.4(0123)166.8 591 S
(+--------------+--------------+--------------+--------------+)120.6 604
Q 6.6(|O)120.6 617 S 39.6(ption |)-6.6 F 26.4(Length=4 |)6.6 F(QS TTL)
13.2 E(|Resv. |Rate)39.6 E(|)19.8 E 92.4(||||)120.6 630 S(|Request|)
-52.8 E(+--------------+--------------+--------------+--------------+)
120.6 643 Q(Figure 3.)120.6 669 Q
(The Quick-Start Request Option for IPv4.)13.2 E F0(The \214rst byte co\
ntains the option \214eld, which includes the one-bit cop)100.8 701 Q
2.75<798d>-.11 G(ag, the 2-bit class)-2.75 E
(\214eld, and the 5-bit option number \(to be assigned by IAN)100.8 714
Q(A\).)-.385 E(Jain/Flo)72 769 Q 204.025(yd/Allman/Sarolahti Section)
-.11 F 2.75(3.1. [P)2.75 F(age 11])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(The sec\
ond byte contains the length \214eld, indicating an option length of fo\
ur bytes.)100.8 85 Q
(The third byte contains the Quick-Start TTL \(QS TTL\) \214eld.)100.8
111 Q(The sender MUST set the QS)5.5 E(TTL \214eld to a random v)100.8
124 Q 2.75(alue. Routers)-.275 F(that appro)2.75 E .33 -.165(ve t)-.165
H(he Quick-Start Request decrement the).165 E(QS TTL \(mod 256\).)100.8
137 Q
(The QS TTL is used by the sender to detect if all of the routers along)
5.5 E(the path understood and appro)100.8 150 Q -.165(ve)-.165 G 2.75
(dt).165 G(he Quick-Start option.)-2.75 E
(The transport sender MUST calculate and store the TTL Dif)100.8 176 Q
(f, the dif)-.275 E(ference between the IP)-.275 E(TTL v)100.8 189 Q
(alue and the QS TTL v)-.275 E(alue in the Quick-Start request pack)
-.275 E(et, as follo)-.11 E(ws:)-.275 E(TTL Dif)100.8 215 Q 2.75(f=\(I)
-.275 G 2.75(PT)-2.75 G(TL - QS TTL \) mod 256)-2.75 E(\(1\))68.75 E
(The fourth byte includes a four)100.8 241 Q(-bit Reserv)-.22 E
(ed \214eld, and a four)-.165 E(-bit Rate Request \214eld.)-.22 E(The)
5.5 E(sender initializes the Rate Request to the desired sending rate, \
including an estimate of the)100.8 254 Q(transport and IP header o)100.8
267 Q -.165(ve)-.165 G(rhead.).165 E(The encoding function for the Rate\
 Request sets the request rate to K*2^N bps, for N the)100.8 293 Q -.275
(va)100.8 306 S
(lue in the Rate Request \214eld, and for K set to 40,000.).275 E -.165
(Fo)5.5 G 2.75(rN).165 G(=0, the rate request w)-2.75 E(ould be)-.11 E
(set to zero, re)100.8 319 Q -.055(ga)-.165 G
(rdless of the encoding function.).055 E(This is illustrated in T)5.5 E
(able 1 belo)-.88 E 4.18 -.715(w. F)-.275 H(or).55 E(the four)100.8 332
Q(-bit Rate Request \214eld, the request range is from 80 Kbps to 1.3 G\
bps.)-.22 E(Alternate)5.5 E
(encodings that were considered for the Rate Request are gi)100.8 345 Q
-.165(ve)-.275 G 2.75(ni).165 G 2.75(nA)-2.75 G(ppendix A.2.)-2.75 E/F1
11/Courier@0 SF 33(NR)107.4 364 S(ate Request \(in Kbps\))-33 E 19.8
(--- -------------------)100.8 377 R 79.2(00)107.4 390 S 72.6(18)107.4
403 S(0)-72.6 E 66(21)107.4 416 S(60)-66 E 66(33)107.4 429 S(20)-66 E 66
(46)107.4 442 S(40)-66 E 52.8(51)107.4 455 S(,280)-52.8 E 52.8(62)107.4
468 S(,560)-52.8 E 52.8(75)107.4 481 S(,120)-52.8 E 46.2(81)107.4 494 S
(0,240)-46.2 E 46.2(92)107.4 507 S(0,480)-46.2 E 39.6(10 40,960)100.8
520 R 39.6(11 81,920)100.8 533 R 33(12 163,840)100.8 546 R 33
(13 327,680)100.8 559 R 33(14 655,360)100.8 572 R 19.8(15 1,310,720)
100.8 585 R(Table 1: Mapping from the Rate Request field to the rate re\
quest in Kbps.)100.8 611 Q F0(Routers can appro)100.8 643 Q .33 -.165
(ve t)-.165 H(he Quick-Start Request for a lo).165 E
(wer rate by decreasing the Rate)-.275 E
(Request in the Quick-Start Request.)100.8 656 Q 1.76 -.88(We n)100.8
682 T(ote that unlik).88 E 2.75(eaQ)-.11 G
(uick-Start Request sent at the be)-2.75 E
(ginning of a connection, when a)-.165 E(Quick-Start Request is sent in\
 the middle of a connection, the connection could already)100.8 695 Q
(ha)100.8 708 Q .33 -.165(ve a)-.22 H 2.75(ne).165 G
(stablished congestion windo)-2.75 E 2.75(wo)-.275 G 2.75(rs)-2.75 G
(ending rate.)-2.75 E(The Rate Request is the requested)5.5 E(total rat\
e for the connection, including the current rate of the connection; the\
 Rate Request)100.8 721 Q(Jain/Flo)72 769 Q 204.025
(yd/Allman/Sarolahti Section)-.11 F 2.75(3.1. [P)2.75 F(age 12])-.165 E
0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(is *not* a request for an additional sending rate o)100.8 85 Q -.165
(ve)-.165 G 2.75(ra).165 G(nd abo)-2.75 E .33 -.165(ve t)-.165 H
(he current sending rate.).165 E(If)5.5 E
(the Rate Request is denied, or lo)100.8 98 Q(wered to a v)-.275 E
(alue belo)-.275 E 2.75(wt)-.275 G(he connection')-2.75 E 2.75(sc)-.605
G(urrent sending)-2.75 E
(rate, then the sender ignores the request, and re)100.8 111 Q -.165(ve)
-.275 G(rts to the def).165 E(ault congestion control)-.11 E
(mechanisms of the transport protocol.)100.8 124 Q(In IPv4, a change in\
 IP options at routers requires recalculating the IP header checksum.)
100.8 150 Q/F1 11/Times-Bold@0 SF(3.2.)72 189 Q/F2 13/Times-Bold@0 SF
(The Quick-Start Request Option f)5.5 E(or IPv6)-.325 E F0(The Quick-St\
art Request Option for IPv6 is placed in the Hop-by-Hop Options e)100.8
215 Q(xtension)-.165 E(header that is processed at e)100.8 228 Q -.165
(ve)-.275 G(ry netw).165 E
(ork node along the communication path [RFC 2460].)-.11 E
(The option format follo)100.8 241 Q
(wing the generic Hop-by-Hop Options header is similar to the IPv4)-.275
E(format with the e)100.8 254 Q
(xception that the Length \214eld should e)-.165 E
(xclude the common type and length)-.165 E
(\214elds in the option format and be set to 2.)100.8 267 Q/F3 11
/Courier@0 SF 92.4(0123)166.8 299 S
(+--------------+--------------+--------------+--------------+)120.6 312
Q 6.6(|O)120.6 325 S 39.6(ption |)-6.6 F 26.4(Length=2 |)6.6 F(QS TTL)
13.2 E(|Resv. |Rate)39.6 E(|)19.8 E 92.4(||||)120.6 338 S(|Request|)
-52.8 E(+--------------+--------------+--------------+--------------+)
120.6 351 Q(Figure 4.)120.6 377 Q
(The Quick-Start Request Option for IPv6.)13.2 E F0(The transport recei)
100.8 409 Q -.165(ve)-.275 G 2.75(rc).165 G
(ompares the Quick-Start TTL with the IPv6 Hop Limit \214eld in)-2.75 E
(order to calculate the TTL Dif)100.8 422 Q 2.75(f. \(The)-.275 F
(Hop Limit in IPv6 is the equi)2.75 E -.275(va)-.275 G
(lent of the TTL in).275 E 2.75(IPv4.\) That)100.8 435 R(is, TTL Dif)
2.75 E 2.75(fM)-.275 G(UST be calculated and stored as follo)-2.75 E
(ws:)-.275 E(TTL Dif)100.8 461 Q 2.75(f=\(I)-.275 G
(Pv6 Hop Limit - QS TTL \) mod 256)-2.75 E(\(2\))49.5 E(Unlik)100.8 487
Q 2.75(eI)-.11 G(Pv4, modifying or deleting the Quick-Start Request IPv\
6 Option does not require)-2.75 E
(checksum re-calculation, because the IPv6 header does not ha)100.8 500
Q .33 -.165(ve a c)-.22 H(hecksum \214eld, and).165 E(modifying the Qui\
ck-Start Request in the IPv6 Hop-by-Hop options header does not af)100.8
513 Q(fect)-.275 E(the IPv6 pseudo-header checksum used in upper)100.8
526 Q(-layer checksum calculations.)-.22 E
(Note that [RFC2460] speci\214es that when a speci\214c \215o)100.8 552
Q 2.75(wl)-.275 G(abel has been assigned to pack)-2.75 E(ets,)-.11 E
(the contents of the Hop-by-Hop options, e)100.8 565 Q(xcluding the ne)
-.165 E(xt header \214eld, must originate)-.165 E
(with the same contents throughout the IP \215o)100.8 578 Q 2.75(wl)
-.275 G 2.75(ifetime. This)-2.75 F(requirement w)2.75 E(ould ha)-.11 E
.33 -.165(ve t)-.22 H 2.75(ob).165 G(e)-2.75 E(modi\214ed to implement \
Quick-Start on an IPv6 implementation that uses \215o)100.8 591 Q 2.75
(wl)-.275 G(abels,)-2.75 E(because the Quick-Start Request option w)
100.8 604 Q(ould be included in only a small fraction of the)-.11 E
(pack)100.8 617 Q(ets during a \215o)-.11 E 2.75(wl)-.275 G(ifetime.)
-2.75 E F1(3.3.)72 656 Q F2(Pr)5.5 E
(ocessing the Quick-Start Request at Routers)-.234 E F0
(Each participating router can either terminate or appro)100.8 682 Q .33
-.165(ve t)-.165 H(he Quick-Start Request.).165 E(The)5.5 E(router term\
inates the Quick-Start Request if the router is not underutilized, and \
therefore)100.8 695 Q(has decided not to grant the Quick-Start Request.)
100.8 708 Q(Jain/Flo)72 769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F
2.75(3.3. [P)2.75 F(age 13])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E 2.75(Ar)
100.8 85 S(outer that wishes to terminate the Quick-Start Request SHOUL\
D delete the Quick-Start)-2.75 E(Request from the IP header)100.8 98 Q
5.5(.T)-.605 G(his sa)-5.5 E -.165(ve)-.22 G 2.75(sr).165 G
(esources as do)-2.75 E(wnstream routers will ha)-.275 E .33 -.165(ve n)
-.22 H(o).165 E(option to process.)100.8 111 Q
(If a Quick-Start-capable router wishes to den)5.5 E 2.75(yt)-.165 G
(he request b)-2.75 E(ut doesn')-.22 E(t)-.198 E
(delete the Quick-Start Request from the IP header)100.8 124 Q 2.75(,t)
-.44 G(hen the router SHOULD zero the QS)-2.75 E
(TTL and the Rate Request \214elds.)100.8 137 Q(This may be more ef)5.5
E(\214cient for routers to implement than)-.275 E
(deleting the Quick-Start option.)100.8 150 Q 2.75(Ar)5.5 G
(outer that doesn')-2.75 E 2.75(tu)-.198 G
(nderstand the Quick-Start option)-2.75 E(will of course simply forw)
100.8 163 Q(ard the pack)-.11 E
(et with the Quick-Start Request unchanged.)-.11 E
(If the participating router has decided to appro)100.8 189 Q .33 -.165
(ve t)-.165 H(he Quick-Start Request, it does the).165 E(follo)100.8 202
Q(wing:)-.275 E 2.75(*T)100.8 228 S
(he router MUST decrements the QS TTL by one.)-2.75 E 2.75(*I)100.8 254
S 2.75(ft)-2.75 G(he router is only willing to appro)-2.75 E .33 -.165
(ve a)-.165 H 2.75(nR).165 G
(ate Request less than that in the Quick-Start)-2.75 E
(Request, then the router replaces the Rate Request with a smaller v)
100.8 267 Q 2.75(alue. The)-.275 F(router MUST)2.75 E(NO)100.8 280 Q
2.75(Ti)-.44 G(ncrease the Rate Request in the Quick-Start Request.)
-2.75 E 2.75(*I)100.8 306 S 2.75(nI)-2.75 G
(Pv4, the router MUST update the IP header checksum.)-2.75 E 2.75(An)
100.8 332 S(on-participating router forw)-2.75 E
(ards the Quick-Start Request unchanged, without)-.11 E
(decrementing the QS TTL.)100.8 345 Q
(Of course, the non-participating router still decrements the)5.5 E
(TTL \214eld in the IP header)100.8 358 Q 2.75(,a)-.44 G 2.75(si)-2.75 G
2.75(sr)-2.75 G(equired for all routers [RFC1812].)-2.75 E
(As a result, the sender)5.5 E(will be able to detect that the Quick-St\
art Request had not been understood or appro)100.8 371 Q -.165(ve)-.165
G 2.75(db).165 G(y)-2.75 E(all of the routers along the path.)100.8 384
Q 2.75(Ar)100.8 410 S(outer that modi\214es or deletes the Quick-Start \
Request in the IPv4 header also MUST)-2.75 E
(update the IPv4 Header checksum.)100.8 423 Q -.165(Fo)5.5 G 2.75(rI)
.165 G(Pv6, no checksum updates are needed.)-2.75 E/F1 11/Times-Bold@0
SF(3.4.)72 462 Q/F2 13/Times-Bold@0 SF(Deciding the P)5.5 E
(ermitted Rate Request at a Router)-.26 E F0
(In this section we brie\215y outline ho)100.8 488 Q 2.75(war)-.275 G
(outer might decide whether or not to appro)-2.75 E .33 -.165(ve a)-.165
H(Quick-Start Request.)100.8 501 Q(As an e)5.5 E
(xample, the router could ask the follo)-.165 E(wing questions:)-.275 E
2.75(*H)100.8 527 S(as the router')-2.75 E 2.75(so)-.605 G
(utput link been underutilized for some time \(e.g., se)-2.75 E -.165
(ve)-.275 G(ral seconds\).).165 E 2.75(*W)100.8 553 S
(ould the output link remain underutilized if the arri)-3.63 E -.275(va)
-.275 G 2.75(lr).275 G(ate w)-2.75 E(as to increase by the)-.11 E(aggre)
100.8 566 Q -.055(ga)-.165 G(te rate requests that the router has appro)
.055 E -.165(ve)-.165 G 2.75(do).165 G -.165(ve)-2.915 G 2.75(rt).165 G
(he last fraction of a second?)-2.75 E
(In order to answer this question, the router must ha)100.8 592 Q .33
-.165(ve s)-.22 H(ome kno).165 E(wledge of the a)-.275 E -.275(va)-.22 G
(ilable).275 E(bandwidth on the output link and of the Quick-Start band\
width that could arri)100.8 605 Q .33 -.165(ve d)-.275 H(ue to).165 E
(recently-appro)100.8 618 Q -.165(ve)-.165 G 2.75(dQ).165 G
(uick-Start Requests.)-2.75 E(In this w)5.5 E(ay)-.11 E 2.75(,i)-.715 G
2.75(fa)-2.75 G 2.75(nu)-2.75 G(nderutilized router e)-2.75 E
(xperiences)-.165 E 2.75<618d>100.8 631 S
(ood of Quick-Start requests, the router can be)-2.75 E(gin to den)-.165
E 2.75(yQ)-.165 G(uick-Start requests while the)-2.75 E
(output link is still underutilized.)100.8 644 Q 2.75(As)100.8 670 S
(imple w)-2.75 E(ay for the router to k)-.11 E
(eep track of the potential bandwidth from recently-)-.11 E(appro)100.8
683 Q -.165(ve)-.165 G 2.75(dr).165 G(equests is to maintain tw)-2.75 E
2.75(oc)-.11 G(ounters, one for the total aggre)-2.75 E -.055(ga)-.165 G
(te Rate Requests).055 E(that ha)100.8 696 Q .33 -.165(ve b)-.22 H
(een appro).165 E -.165(ve)-.165 G 2.75(di).165 G 2.75(nt)-2.75 G
(he current time interv)-2.75 E
(al [T1, T2], for the current time between)-.275 E
(T1 and T2, and one for the total aggre)100.8 709 Q -.055(ga)-.165 G
(te Rate Requests appro).055 E -.165(ve)-.165 G 2.75(do).165 G -.165(ve)
-2.915 G 2.75(rap).165 G(re)-2.75 E(vious time)-.275 E(interv)100.8 722
Q(al [T0, T1].)-.275 E(Ho)5.5 E(we)-.275 E -.165(ve)-.275 G .88 -.44
(r, t).165 H(his document doesn').44 E 2.75(ts)-.198 G
(pecify router algorithms for appro)-2.75 E(ving)-.165 E(Jain/Flo)72 769
Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75(3.4. [P)2.75 F
(age 14])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(Quick-Start requests, or mak)100.8 85 Q 2.75(er)-.11 G
(equirements for the appropriate time interv)-2.75 E(als for)-.275 E
(remembering the aggre)100.8 98 Q -.055(ga)-.165 G(te appro).055 E -.165
(ve)-.165 G 2.75(dQ).165 G(uick-Start bandwidth.)-2.75 E 2.75(Ap)5.5 G
(ossible router algorithm)-2.75 E(is gi)100.8 111 Q -.165(ve)-.275 G
2.75(ni).165 G 2.75(nA)-2.75 G
(ppendix C, and more discussion of these issues is a)-2.75 E -.275(va)
-.22 G(ilable in [SAF05].\)).275 E 2.75(*I)100.8 137 S 2.75(ft)-2.75 G
(he router')-2.75 E 2.75(so)-.605 G
(utput link has been underutilized and the aggre)-2.75 E -.055(ga)-.165
G(te Quick Start Request).055 E(Rate options granted is lo)100.8 150 Q
2.75(we)-.275 G(nough to pre)-2.75 E -.165(ve)-.275 G(nt a near).165 E
(-term bandwidth shortage, then the)-.22 E(router could appro)100.8 163
Q .33 -.165(ve t)-.165 H(he Quick-Start Request.).165 E(Section 8.2 dis\
cusses some of the implementation issues in processing Quick-Start requ\
ests)100.8 189 Q(at routers.)100.8 202 Q([SAF05] discusses the range of\
 possible Quick-Start algorithms at the router for)5.5 E
(deciding whether to appro)100.8 215 Q .33 -.165(ve a Q)-.165 H
(uick-Start request.).165 E(In order to e)5.5 E
(xplore the limits of the)-.165 E(possible functionality at routers, [S\
AF05] also discusses Extreme Quick-Start mechanisms)100.8 228 Q
(at routers, where the router w)100.8 241 Q(ould k)-.11 E(eep per)-.11 E
(-\215o)-.22 E 2.75(ws)-.275 G(tate concerning appro)-2.75 E -.165(ve)
-.165 G 2.75(dQ).165 G(uick-Start)-2.75 E(requests.)100.8 254 Q/F1 11
/Times-Bold@0 SF(3.5.)72 293 Q/F2 13/Times-Bold@0 SF
(Quick-Start in IP T)5.5 E(unnels)-1.196 E F0
(In this section we consider the ef)100.8 319 Q
(fect of IP tunnels on Quick-Start.)-.275 E(In the discussion, we)5.5 E
(use TTL Dif)100.8 332 Q(f, de\214ned earlier as the dif)-.275 E
(ference between the IP TTL and the Quick-Start)-.275 E(TTL, mod 256.)
100.8 345 Q
(Recall that the sender considers the Quick-Start request appro)5.5 E
-.165(ve)-.165 G 2.75(di).165 G 2.75(ft)-2.75 G(he)-2.75 E -.275(va)
100.8 358 S(lue of TTL Dif).275 E 2.75(ff)-.275 G(or the pack)-2.75 E
(et entering the netw)-.11 E(ork is the same as the v)-.11 E
(alue of TTL Dif)-.275 E(f)-.275 E(for the pack)100.8 371 Q(et e)-.11 E
(xiting the netw)-.165 E(ork.)-.11 E(There are tw)100.8 397 Q 2.75(ol)
-.11 G -.165(eg)-2.75 G(itimate w).165 E
(ays for handling the Quick-Start Request with IP tunnels:)-.11 E(\(1\)\
 The tunnel ingress node does not support Quick-Start, or does not appr\
o)100.8 423 Q .33 -.165(ve t)-.165 H(he Quick-).165 E(Start request. Th\
e node could strip the Quick-Start Request option from the IP header)
100.8 436 Q(before encapsulation.)100.8 449 Q(Alternately)5.5 E 2.75(,t)
-.715 G(he ingress node can decrement the IP TTL before)-2.75 E
(encapsulation, while lea)100.8 462 Q
(ving the Quick-Start TTL unchanged, thereby changing TTL Dif)-.22 E(f.)
-.275 E(This is the assumed beha)100.8 475 Q
(vior of current IP tunnels that are not a)-.22 E -.11(wa)-.165 G
(re of Quick-Start.).11 E -.165(Fo)100.8 501 S 2.75(rat).165 G(unnel in\
gress node that does not support Quick-Start, problems with a Quick-Sta\
rt)-2.75 E
(Request could still occur if a tunnel discards the outer header at e)
100.8 514 Q(gress and does not)-.165 E
(decrement the inner IP TTL at the ingress.)100.8 527 Q
(In this case, if both the inner IP TTL and the)5.5 E
(Quick-Start TTL are decremented after decapsulation at a Quick-Start-a)
100.8 540 Q -.11(wa)-.165 G(re e).11 E(gress, or if)-.165 E
(neither is decremented at the e)100.8 553 Q(gress, then TTL Dif)-.165 E
2.75(fw)-.275 G(ould be the same after e)-2.86 E(gress as it w)-.165 E
(as)-.11 E(before ingress, so that it w)100.8 566 Q
(ould wrongly appear that all the routers in the tunnel had)-.11 E
(appro)100.8 579 Q -.165(ve)-.165 G 2.75(dt).165 G
(he Quick-Start request.)-2.75 E -.165(Fo)5.5 G(rtunately).165 E 2.75
(,w)-.715 G 2.75(ea)-2.75 G(re not a)-2.75 E -.11(wa)-.165 G
(re of tunnel technologies).11 E(that operate this w)100.8 592 Q
(ay; to the best of our kno)-.11 E
(wledge, all tunnels decrement the IP TTL either)-.275 E
(at the ingress before encapsulation, or at the e)100.8 605 Q
(gress router after decapsulation, thus)-.165 E(changing TTL Dif)100.8
618 Q(f.)-.275 E(Ev)100.8 644 Q(en the e)-.165 E(xtreme case when the t\
unnel ingress is at the TCP sender and the tunnel e)-.165 E(gress is)
-.165 E(at the TCP recei)100.8 657 Q -.165(ve)-.275 G .88 -.44(r, o).165
H(ur assumption is that the IP TTL will be decremented either at the).44
E(tunnel ingress or at the tunnel e)100.8 670 Q(gress, changing TTL Dif)
-.165 E 2.75(fa)-.275 G(nd pre)-2.75 E -.165(ve)-.275 G
(nting the end-nodes).165 E
(from wrongly inferring that the Quick-Start Request w)100.8 683 Q
(as appro)-.11 E -.165(ve)-.165 G 2.75(db).165 G 2.75(ya)-2.75 G
(ll of the routers)-2.75 E(along the path.)100.8 696 Q(If there are tun\
nels where the IP TTL in not decremented, perhaps for PPP)5.5 E -.165
(ove)100.8 709 S 2.75(rS).165 G(SH, then additional attention will ha)
-2.75 E .33 -.165(ve t)-.22 H 2.75(ob).165 G 2.75(ep)-2.75 G
(aid to the rob)-2.75 E(ustness of Quick-Start in)-.22 E(these en)100.8
722 Q(vironments.)-.44 E(Jain/Flo)72 769 Q 204.025
(yd/Allman/Sarolahti Section)-.11 F 2.75(3.5. [P)2.75 F(age 15])-.165 E
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E 2.75(AQ)
100.8 85 S(uick-Start-a)-2.75 E -.11(wa)-.165 G(re e).11 E
(gress must also mak)-.165 E 2.75(es)-.11 G
(ure that the Quick-Start Request is not)-2.75 E(appro)100.8 98 Q -.165
(ve)-.165 G 2.75(di).165 G 2.75(ff)-2.75 G(or some reason the inner hea\
der includes the Quick-Start Request option, the)-2.75 E
(outer header does not, and the Quick-Start TTL and IP TTL ha)100.8 111
Q .33 -.165(ve b)-.22 H(een decremented in a).165 E -.11(fa)100.8 124 S
(shion that mak).11 E(es it appear as if the request has been appro)-.11
E -.165(ve)-.165 G 2.75(d. If).165 F(the Quick-Start)2.75 E
(Request doesn')100.8 137 Q 2.75(ta)-.198 G(ppear in the outer header)
-2.75 E 2.75(,t)-.44 G(hen the e)-2.75 E(gress node should remo)-.165 E
.33 -.165(ve t)-.165 H(he Quick-).165 E
(Start Request option from the inner header after decapsulation.)100.8
150 Q(Alternately)5.5 E 2.75(,t)-.715 G(he e)-2.75 E(gress)-.165 E(node\
 could decrement the Rate Request in the Quick-Start Request option to \
zero.)100.8 163 Q(\(2\) The tunnel ingress node may choose to support Q\
uick-Start, and locally appro)100.8 189 Q .33 -.165(ve t)-.165 H(he).165
E(Quick-Start Request.)100.8 202 Q
(In this case the IP TTL and Quick-Start option MUST be copied)5.5 E(fr\
om the inner IP header to the outer header at the tunnel ingress. Upon \
decapsulation, the)100.8 215 Q(IP TTL and the Quick-Start option in the\
 outer IP header MUST be copied back to the)100.8 228 Q(inner header)
100.8 241 Q 5.5(.I)-.605 G 2.75(ft)-5.5 G
(he ingress router decrements the IP TTL in the inner header before)
-2.75 E(encapsulation, or in the outer header after encapsulation, then\
 if the ingress router wishes)100.8 254 Q(to appro)100.8 267 Q .33 -.165
(ve t)-.165 H(he Quick-Start request, it MUST decrement the Quick-Start\
 TTL at the same).165 E(time, so as not to change TTL Dif)100.8 280 Q
2.75(f. Similarly)-.275 F 2.75(,i)-.715 G 2.75(ft)-2.75 G(he e)-2.75 E
(gress router wishes to appro)-.165 E .33 -.165(ve t)-.165 H(he).165 E(\
Quick-Start request, then when it decrements the IP TTL in the outer he\
ader before)100.8 293 Q(decapsulation, or in the inner header after dec\
apsulation, it MUST decrement the Quick-)100.8 306 Q
(Start TTL at the same time.)100.8 319 Q 2.75(At)100.8 345 S
(unnel ingress node can support a Quick-Start request without e)-2.75 E
(xplicitly v)-.165 E(erifying that)-.165 E(the tunnel e)100.8 358 Q
(gress also supports Quick-Start.)-.165 E
(All that the ingress node has to do is to)5.5 E
(decrement the IP TTL, b)100.8 371 Q
(ut not the Quick-Start TTL, in the inner header after)-.22 E 2.75
(encapsulation. In)100.8 384 R(this case, if the e)2.75 E
(gress node simply discards the outer header at the e)-.165 E(gress)
-.165 E(point, TTL Dif)100.8 397 Q 2.75(fw)-.275 G(ill be dif)-2.75 E
(ferent after the tunnel e)-.275 E(gress than it w)-.165 E
(as at the tunnel ingress,)-.11 E
(and the Quick-Start will not be considered by the end-nodes as ha)100.8
410 Q(ving been appro)-.22 E -.165(ve)-.165 G 2.75(di).165 G 2.75(nt)
-2.75 G(he)-2.75 E(netw)100.8 423 Q 2.75(ork. Thus,)-.11 F
(the tunnel ingress node on its o)2.75 E(wn can pro)-.275 E
(vide protection ag)-.165 E(ainst e)-.055 E(gress)-.165 E
(nodes that might discard the outer header at the e)100.8 436 Q
(gress point.)-.165 E/F1 11/Times-Bold@0 SF(3.6.)72 475 Q/F2 13
/Times-Bold@0 SF 3.25(AR)5.5 G(ate-Reduced Nonce?)-3.25 E F0
(One possibility for the Reserv)100.8 501 Q(ed Field, for further in)
-.165 E -.165(ve)-.44 G(stig).165 E
(ation, is to use the four bits for a)-.055 E(four)100.8 514 Q
(-bit Rate-Reduced Nonce.)-.22 E(The goal of the Rate-Reduced Nonce w)
5.5 E(ould be to gi)-.11 E .33 -.165(ve t)-.275 H(he).165 E
(Quick-Start sender some protection ag)100.8 527 Q(ainst recei)-.055 E
-.165(ve)-.275 G(rs lying about the v).165 E(alue of the recei)-.275 E
-.165(ve)-.275 G(d).165 E(Rate Request.)100.8 540 Q
(The Rate-Reduced Nonce w)5.5 E
(ould be initialized by the sender to a random)-.11 E -.275(va)100.8 553
S 2.75(lue. When).275 F 2.75(ar)2.75 G(outer appro)-2.75 E -.165(ve)
-.165 G 2.75(st).165 G(he Quick-Start request b)-2.75 E
(ut reduces the Rate Request \214eld,)-.22 E
(the router resets the Rate-Reduced Nonce to a ne)100.8 566 Q 2.75(wr)
-.275 G(andom v)-2.75 E 2.75(alue. When)-.275 F 2.75(aQ)2.75 G
(uick-Start-)-2.75 E(capable router denies the Quick-Start request, the\
 router either deletes the Quick-Start)100.8 579 Q(Option, or zeroes th\
e Rate-Reduced Nonce when zeroing the Rate Request and the QS)100.8 592
Q 2.75(TTL. The)100.8 605 R(recei)2.75 E -.165(ve)-.275 G 2.75(rr).165 G
(eports the v)-2.75 E(alue of the Rate-Reduced Nonce back to the sender)
-.275 E(.)-.605 E(The Rate-Reduced Nonce w)100.8 631 Q
(ould be of use in cases where the recei)-.11 E -.165(ve)-.275 G 2.75
(rk).165 G(no)-2.75 E(ws the original)-.275 E
(Rate Request R sent by the sender \(e.g., because the sender al)100.8
644 Q -.11(wa)-.11 G(ys uses the same Rate).11 E(Request\), b)100.8 657
Q(ut the Rate Request has been decremented by routers along the path.)
-.22 E(What)5.5 E(pre)100.8 670 Q -.165(ve)-.275 G(nts the recei).165 E
-.165(ve)-.275 G 2.75(rf).165 G
(rom reporting back to the sender a Rate Request of R, when the)-2.75 E
(recei)100.8 683 Q -.165(ve)-.275 G 2.75(dR).165 G(ate Request w)-2.75 E
(as in f)-.11 E(act less than R?)-.11 E(If the Rate Request w)5.5 E
(as not decremented in)-.11 E(the netw)100.8 696 Q
(ork, then the Rate-Reduced Nonce should ha)-.11 E .33 -.165(ve i)-.22 H
(ts original v).165 E 2.75(alue. If)-.275 F(the Rate)2.75 E(Request *w)
100.8 709 Q(as* decremented in the netw)-.11 E
(ork, then the probability that the Rate-Reduced)-.11 E
(Nonce still has its original v)100.8 722 Q(alue is 1/16.)-.275 E
(Similarly)5.5 E 2.75(,i)-.715 G 2.75(ft)-2.75 G(he Rate Request w)-2.75
E(as decremented in)-.11 E(Jain/Flo)72 769 Q 204.025
(yd/Allman/Sarolahti Section)-.11 F 2.75(3.6. [P)2.75 F(age 16])-.165 E
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(the netw)100.8 85 Q(ork, the chance that the recei)-.11 E -.165(ve)
-.275 G 2.75(rc).165 G(an guess the original v)-2.75 E
(alue of the Rate-Reduced)-.275 E(Nonce is 1/16.)100.8 98 Q
(Thus, if the recei)100.8 124 Q -.165(ve)-.275 G 2.75(rr).165 G
(eports back to the sender the original v)-2.75 E
(alues for the Rate Request and)-.275 E
(the Rate-Reduced Nonce, and the correct v)100.8 137 Q
(alue for the TTL Dif)-.275 E(f, then it is lik)-.275 E(ely that the)
-.11 E(Quick-Start Request w)100.8 150 Q(as in f)-.11 E(act appro)-.11 E
-.165(ve)-.165 G 2.75(da).165 G 2.75(ti)-2.75 G(ts original v)-2.75 E
(alue by the routers along the path,)-.275 E
(in particular by all of the Quick-Start-capable routers.)100.8 163 Q
(The Rate-Reduced Nonce w)5.5 E(ould)-.11 E(mak)100.8 176 Q 2.75(ei)-.11
G 2.75(tm)-2.75 G(ore dif)-2.75 E(\214cult for the recei)-.275 E -.165
(ve)-.275 G 2.75(rt).165 G 2.75(or)-2.75 G
(eport that the Rate Request w)-2.75 E(as recei)-.11 E -.165(ve)-.275 G
2.75(da).165 G 2.75(ti)-2.75 G(ts)-2.75 E(original v)100.8 189 Q
(alue, when in f)-.275 E(act the recei)-.11 E -.165(ve)-.275 G 2.75(dR)
.165 G(ate Request w)-2.75 E(as less than its original v)-.11 E(alue.)
-.275 E 1.76 -.88(We n)100.8 215 T(ote, ho).88 E(we)-.275 E -.165(ve)
-.275 G .88 -.44(r, t).165 H(hat the Rate-Reduced Nonce doesn').44 E
2.75(tp)-.198 G(ro)-2.75 E(vide protection ag)-.165 E(ainst)-.055 E
(recei)100.8 228 Q -.165(ve)-.275 G
(rs reporting that the Rate Request w).165 E
(as decremented by only one step, when it f)-.11 E(act it)-.11 E -.11
(wa)100.8 241 S 2.75(sd).11 G(ecremented by man)-2.75 E 2.75(ys)-.165 G
(teps in the netw)-2.75 E 2.75(ork. This,)-.11 F(if the recei)2.75 E
-.165(ve)-.275 G 2.75(rk).165 G(no)-2.75 E(ws the original)-.275 E
(Rate Request from the sender)100.8 254 Q 2.75(,a)-.44 G(nd the recei)
-2.75 E -.165(ve)-.275 G 2.75(dr).165 G
(ate request is considerably less than the)-2.75 E
(original request, then the recei)100.8 267 Q -.165(ve)-.275 G 2.75(rc)
.165 G(ould report a recei)-2.75 E -.165(ve)-.275 G 2.75(dr).165 G
(ate request just one step smaller)-2.75 E
(than the original request, and the Rate-Reduced Nonce w)100.8 280 Q
(ouldn')-.11 E 2.75(tp)-.198 G(ro)-2.75 E(vide an)-.165 E 2.75(yp)-.165
G(rotection)-2.75 E(ag)100.8 293 Q(ainst this.)-.055 E
(Section 6.3 also considers issues of recei)100.8 319 Q -.165(ve)-.275 G
2.75(rc).165 G(heating in more detail.)-2.75 E/F1 11/Times-Bold@0 SF(4.)
72 358 Q/F2 14/Times-Bold@0 SF(The Quick-Start Mechanisms in TCP)5.5 E
F0(This section describes ho)100.8 384 Q 2.75(wt)-.275 G
(he Quick-Start mechanism w)-2.75 E(ould be used in TCP)-.11 E 5.5(.W)
-1.221 G 2.75<658c>-6.38 G(rst)-2.75 E(sk)100.8 397 Q(etch the procedur\
e and then tightly de\214ne it in the subsequent subsections.)-.11 E
(If a TCP sender)100.8 423 Q 2.75(,s)-.44 G(ay host A, w)-2.75 E
(ould lik)-.11 E 2.75(et)-.11 G 2.75(ou)-2.75 G
(se Quick-Start, the TCP sender puts the)-2.75 E(requested sending rate\
 in bytes per second, appropriately formatted, in the Quick-Start)100.8
436 Q(Request option in the IP header of the TCP pack)100.8 449 Q
(et, called the Quick-Start request pack)-.11 E(et.)-.11 E(\(W)100.8 462
Q 2.75(ew)-.88 G(ill be some)-2.75 E(what loose in our use of "pack)
-.275 E(et" vs. "se)-.11 E(gment" in this section.\))-.165 E(When)5.5 E
(used for initial start-up, the Quick-Start request pack)100.8 475 Q
(et can be either the SYN or SYN/A)-.11 E(CK)-.44 E(pack)100.8 488 Q
(et, as described abo)-.11 E -.165(ve)-.165 G 5.5(.T).165 G
(he requested rate includes an estimate for the transport and IP)-5.5 E
(header o)100.8 501 Q -.165(ve)-.165 G 2.75(rhead. The).165 F(TCP recei)
2.75 E -.165(ve)-.275 G .88 -.44(r, s).165 H
(ay host B, returns the Quick-Start Response option in).44 E
(the TCP header in the responding SYN/A)100.8 514 Q(CK pack)-.44 E
(et or A)-.11 E(CK pack)-.44 E(et, called the Quick-Start)-.11 E
(response pack)100.8 527 Q
(et, informing host A of the results of their request.)-.11 E
(If the ackno)100.8 553 Q(wledging pack)-.275 E
(et does not contain a Quick-Start Response, or contains a Quick-)-.11 E
(Start Response with the wrong v)100.8 566 Q(alue for the TTL Dif)-.275
E(f, then host A MUST assume that its)-.275 E(Quick-Start request f)
100.8 579 Q 2.75(ailed. In)-.11 F(this case, host A uses TCP')2.75 E
2.75(sd)-.605 G(ef)-2.75 E(ault congestion control)-.11 E 2.75
(procedure. F)100.8 592 R(or initial start-up, host A uses the def)-.165
E(ault initial congestion windo)-.11 E -.715(w.)-.275 G
(If the returning pack)100.8 618 Q(et contains a v)-.11 E
(alid Quick-Start Response, then host A uses the)-.275 E(information in\
 the response, along with its measurement of the round-trip time, to)
100.8 631 Q(determine the Quick-Start congestion windo)100.8 644 Q 2.75
(w\()-.275 G 2.75(QS-cwnd\). Quick-Start)-2.75 F(pack)2.75 E
(ets are de\214ned)-.11 E(as pack)100.8 657 Q(ets sent as the result of\
 a successful Quick-Start request, up to the time when the)-.11 E
(\214rst Quick-Start pack)100.8 670 Q(et is ackno)-.11 E 2.75
(wledged. In)-.275 F(order to use Quick-Start, the TCP host MUST)2.75 E
(use rate-based pacing to transmit Quick-Start pack)100.8 683 Q
(ets at the rate indicated in the Quick-)-.11 E
(Start Response, at the le)100.8 696 Q -.165(ve)-.275 G 2.75(lo).165 G
2.75(fg)-2.75 G(ranularity possible by the sending host.)-2.75 E 1.76
-.88(We n)5.5 H(ote that the).88 E(limitations of interrupt timing on c\
omputers can limit the ability of the TCP host in rate-)100.8 709 Q
(pacing the outgoing pack)100.8 722 Q(ets.)-.11 E(Jain/Flo)72 769 Q
212.275(yd/Allman/Sarolahti Section)-.11 F 2.75(4. [P)2.75 F(age 17])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(The tw)
100.8 85 Q 2.75(oT)-.11 G
(CP end-hosts can independently decide whether to request Quick-Start.)
-2.75 E -.165(Fo)5.5 G(r).165 E -.165(ex)100.8 98 S
(ample, host A could sent a Quick-Start Request in the SYN pack).165 E
(et, and host B could also)-.11 E
(send a Quick-Start Request in the SYN/A)100.8 111 Q(CK pack)-.44 E(et.)
-.11 E/F1 11/Times-Bold@0 SF(4.1.)72 150 Q/F2 13/Times-Bold@0 SF
(When to Use Quick-Start)5.5 E F0(In addition to the use of Quick-Start\
 when a connection is established, there are se)100.8 176 Q -.165(ve)
-.275 G(ral).165 E
(additional points in a connection when a transport protocol may w)100.8
189 Q(ant to issue a Rate)-.11 E 2.75(Request. W)100.8 202 R 2.75<658c>
-.88 G(rst re-iterate the notion that Quick-Start is a coarse-grained m\
echanism.)-2.75 E(That is, Quick-Start')100.8 215 Q 2.75(sR)-.605 G
(ate Requests are not meant to be used for \214ne-grained control of)
-2.75 E(the transport')100.8 228 Q 2.75(ss)-.605 G(ending rate.)-2.75 E
(Rather)5.5 E 2.75(,t)-.44 G(he transport MA)-2.75 E 2.75(Yi)-1.155 G
(ssue a Rate Request when no)-2.75 E
(information about the appropriate sending rate is a)100.8 241 Q -.275
(va)-.22 G(ilable, and the def).275 E(ault congestion)-.11 E(control me\
chanisms might be signi\214cantly underestimating the appropriate sendi\
ng rate.)100.8 254 Q(The follo)100.8 280 Q
(wing are potential points where Quick-Start may be useful:)-.275 E(\(1\
\) At connection initiation when the transport has no idea of the capac\
ity of the)129.6 309.6 Q(netw)129.6 322.6 Q(ork, as discussed abo)-.11 E
-.165(ve)-.165 G 5.5(.\().165 G 2.75(At)-5.5 G
(ransport that uses TCP Control Block sharing, the)-2.75 E
(Congestion Manager)129.6 335.6 Q 2.75(,o)-.44 G 2.75(rt)-2.75 G(he lik)
-2.75 E 2.75(em)-.11 G(ay not need Quick-Start to determine an)-2.75 E
(appropriate rate.\))129.6 348.6 Q
(\(2\) After an idle period when the transport no longer has a v)129.6
378.2 Q(alidated estimate of the)-.275 E -.22(av)129.6 391.2 S
(ailable bandwidth for this \215o)-.055 E 4.18 -.715(w. \()-.275 H(An e)
.715 E(xample could be a persistent-HTTP)-.165 E(connection when a ne)
129.6 404.2 Q 2.75(wH)-.275 G(TTP request is recei)-2.75 E -.165(ve)
-.275 G 2.75(da).165 G(fter an idle period.\))-2.75 E
(\(3\) After a host has recei)129.6 433.8 Q -.165(ve)-.275 G 2.75(de)
.165 G(xplicit indications that one of the endpoints has mo)-2.915 E
-.165(ve)-.165 G(d).165 E(its point of netw)129.6 446.8 Q
(ork attachment.)-.11 E(This can happen due to some underlying mobility)
5.5 E(mechanism lik)129.6 459.8 Q 2.75(eM)-.11 G
(obile IP [RFC3344,RFC3775].)-2.75 E(Some transports, such as SCTP)5.5 E
([RFC2960], may associate with multiple IP addresses and can switch add\
resses \(and,)129.6 472.8 Q(therefore netw)129.6 485.8 Q
(ork paths\) in mid-connection.)-.11 E
(If the transport has concrete kno)5.5 E(wledge)-.275 E
(of a changing netw)129.6 498.8 Q
(ork path then the current sending rate may not be appropriate and)-.11
E(the transport sender may use Quick-Start to probe the netw)129.6 511.8
Q(ork for the appropriate)-.11 E(rate at which to send.)129.6 524.8 Q
(\(Alternati)5.5 E -.165(ve)-.275 G(ly).165 E 2.75(,t)-.715 G
(raditional slo)-2.75 E(w-start should be used in this)-.275 E
(case when Quick-Start is not a)129.6 537.8 Q -.275(va)-.22 G(ilable.\))
.275 E(\(4\) After an application-limited period when the sender has be\
en using only a small)129.6 567.4 Q
(amount of its appropriate share of the netw)129.6 580.4 Q(ork capacity)
-.11 E 2.75(,a)-.715 G(nd has no v)-2.75 E(alid estimate for)-.275 E
(its f)129.6 593.4 Q(air share.)-.11 E
(In this case, Quick-Start may be an appropriate mechanism to assess)5.5
E(the a)129.6 606.4 Q -.275(va)-.22 G(ilable capacity on the netw).275 E
(ork path.)-.11 E -.165(Fo)5.5 G 2.75(ri).165 G
(nstance, consider an application that)-2.75 E(steadily e)129.6 619.4 Q
(xchanges lo)-.165 E
(w-rate control messages and suddenly needs to transmit a lar)-.275 E
(ge)-.198 E(amount of data.)129.6 632.4 Q(Of the abo)100.8 662 Q -.165
(ve)-.165 G 2.75(,t).165 G(his document recommends that a TCP sender MA)
-2.75 E 2.75(Ya)-1.155 G(ttempt to use Quick-)-2.75 E
(Start in cases \(1\) and \(2\).)100.8 675 Q
(It is not recommended that a TCP sender use Quick-Start for)5.5 E
(case \(3\) at the current time.)100.8 688 Q(Case \(3\) requires e)5.5 E
(xternal noti\214cations not presently de\214ned)-.165 E
(for TCP or other transport protocols.)100.8 701 Q(Finally)5.5 E 2.75
(,aT)-.715 G(CP SHOULD NO)-2.75 E 2.75(Tu)-.44 G(se Quick-Start for)
-2.75 E(case \(4\) at the current time.)100.8 714 Q
(Case \(4\) requires further thought and in)5.5 E -.165(ve)-.44 G(stig)
.165 E(ation with re)-.055 E -.055(ga)-.165 G(rd).055 E(Jain/Flo)72 769
Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75(4.1. [P)2.75 F
(age 18])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(to ho)
100.8 85 Q 2.75(wt)-.275 G(he transport protocol could determine it w)
-2.75 E(as in a situation that w)-.11 E(ould w)-.11 E(arrant)-.11 E
(transmitting a Quick-Start Rate Request.)100.8 98 Q(Section 4.6 discus\
ses some of the issues of using Quick-Start at connection initiation, a\
nd)100.8 124 Q(Section 4.7 discusses issues that arise when Quick-Start\
 is used to request a lar)100.8 137 Q(ger sending)-.198 E
(rate after an idle period.)100.8 150 Q/F1 11/Times-Bold@0 SF(4.2.)72
189 Q/F2 13/Times-Bold@0 SF
(The Quick-Start Response Option in the TCP header)5.5 E F0(TCP')100.8
215 Q 2.75(sQ)-.605 G(uick-Start Response option is de\214ned as follo)
-2.75 E(ws:)-.275 E/F3 11/Courier@0 SF 66(0123)153.6 247 S
(+----------+----------+----------+----------+)120.6 260 Q 13.2(|K)120.6
273 S 19.8(ind |)-13.2 F(Length=4 |)6.6 E 19.8(Rate |)13.2 F 19.8(TTL |)
19.8 F 66(|||)120.6 286 S 6.6(Request |)-59.4 F 13.2(Diff |)19.8 F
(+----------+----------+----------+----------+)120.6 299 Q(Figure 5.)
120.6 325 Q(The Quick-Start Response option in the TCP header.)13.2 E F0
(The \214rst byte of the Quick-Start Response option contains the optio\
n kind, identifying the)100.8 357 Q(TCP option \(to be assigned by IAN)
100.8 370 Q(A\).)-.385 E(The second byte of the Quick-Start Response op\
tion contains the option length in bytes.)100.8 396 Q
(The length \214eld MUST be set to four bytes.)100.8 409 Q
(The third byte of the Quick-Start Response option contains the allo)
100.8 435 Q(wed Rate Request,)-.275 E
(formatted as in the Quick-Start Request option.)100.8 448 Q
(The fourth byte of the TCP option contains the TTL Dif)100.8 474 Q 2.75
(f. The)-.275 F(TTL Dif)2.75 E 2.75(fc)-.275 G(ontains the)-2.75 E(dif)
100.8 487 Q(ference between the IP TTL and QS TTL \214elds in the recei)
-.275 E -.165(ve)-.275 G 2.75(dQ).165 G(uick-Start request)-2.75 E(pack)
100.8 500 Q(et, as calculated in equations \(1\) or \(2\) \(depending o\
n whether IPv4 or IPv6 is used\).)-.11 E F1(4.3.)72 539 Q F2
(TCP: Sending the Quick-Start Response)5.5 E F0
(An end host, say host B, that recei)100.8 565 Q -.165(ve)-.275 G 2.75
(sa).165 G 2.75(nI)-2.75 G 2.75(Pp)-2.75 G(ack)-2.75 E
(et containing a Quick-Start Request passes)-.11 E
(the Quick-Start Request, along with the v)100.8 578 Q
(alue in the IP TTL \214eld, to the recei)-.275 E(ving TCP)-.275 E
(layer)100.8 591 Q(.)-.605 E(If the TCP host is willing to permit the Q\
uick-Start Request, then a Quick-Start Response)100.8 617 Q
(option is included in the TCP header of the corresponding ackno)100.8
630 Q(wledgement pack)-.275 E 2.75(et. The)-.11 F
(Rate Request in the Quick-Start Response option is set to the recei)
100.8 643 Q -.165(ve)-.275 G 2.75(dv).165 G(alue of the Rate)-3.025 E
(Request in the Quick-Start Request option, or to a lo)100.8 656 Q
(wer v)-.275 E(alue if the TCP recei)-.275 E -.165(ve)-.275 G 2.75(ri)
.165 G 2.75(so)-2.75 G(nly)-2.75 E(willing to allo)100.8 669 Q 2.75(wal)
-.275 G -.275(ow)-2.75 G(er Rate Request.).275 E(The TTL Dif)5.5 E 2.75
(fi)-.275 G 2.75(nt)-2.75 G(he Quick-Start Response is set to)-2.75 E
(the dif)100.8 682 Q(ference between the IP TTL v)-.275 E
(alue and the QS TTL v)-.275 E(alue as gi)-.275 E -.165(ve)-.275 G 2.75
(ni).165 G 2.75(ne)-2.75 G(quation \(1\) or)-2.75 E
(\(2\) \(depending on whether IPv4 or IPv6 is used\).)100.8 695 Q
(The Quick-Start Response will not be resent if it is lost in the netw)
100.8 721 Q(ork. P)-.11 E(ack)-.165 E(et loss is an)-.11 E(Jain/Flo)72
769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75(4.3. [P)2.75 F
(age 19])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(indicat\
ion of congestion on the return path, in which case it is better not to\
 appro)100.8 85 Q .33 -.165(ve t)-.165 H(he).165 E(Quick-Start Request.)
100.8 98 Q/F1 11/Times-Bold@0 SF(4.4.)72 137 Q/F2 13/Times-Bold@0 SF
(TCP: Recei)5.5 E(ving and Using the Quick-Start Response P)-.13 E(ack)
-.13 E(et)-.13 E F0 2.75(AT)100.8 163 S
(CP host, say TCP host A, that sent a Quick-Start Request and recei)
-2.75 E -.165(ve)-.275 G 2.75(saQ).165 G(uick-Start)-2.75 E
(Response in an ackno)100.8 176 Q
(wledgement \214rst checks that the Quick-Start Response is v)-.275 E
2.75(alid. The)-.275 F(Quick-Start Response is v)100.8 189 Q
(alid if it contains the correct v)-.275 E(alue for the TTL Dif)-.275 E
(f, and an equal)-.275 E(or lesser v)100.8 202 Q(alue for the Rate Requ\
est than that transmitted in the Quick-Start Request.)-.275 E(If)5.5 E
(this check is not successful, then the Quick-Start request f)100.8 215
Q(ailed, and the TCP host MUST)-.11 E(use the def)100.8 228 Q
(ault TCP congestion windo)-.11 E 2.75(wt)-.275 G(hat it w)-2.75 E
(ould ha)-.11 E .33 -.165(ve u)-.22 H(sed without Quick-Start.).165 E
(If the checks of the TTL Dif)100.8 254 Q 2.75(fa)-.275 G
(nd the Rate Request are successful, then the TCP host sets)-2.75 E
(its Quick-Start congestion windo)100.8 267 Q 2.75(w\()-.275 G
(in terms of MSS-sized se)-2.75 E(gments\), QS-cwnd, as)-.165 E(follo)
100.8 280 Q(ws:)-.275 E(QS-cwnd = \(R * T\) / \(MSS + H\))100.8 306 Q
(\(3\))88 E(where R the Rate Request in bytes per second, T the measure\
d round-trip time in seconds,)100.8 332 Q
(and H the estimated TCP/IP header size in bytes \(e.g., 40 bytes\).)
100.8 345 Q(Deri)100.8 371 Q -.275(va)-.275 G(tion: the sender is allo)
.275 E(wed to transmit at R bytes per second including pack)-.275 E(et)
-.11 E(headers, b)100.8 384 Q
(ut only R*MSS/\(MSS+H\) bytes per second, or equi)-.22 E -.275(va)-.275
G(lently R*T*MSS/\(MSS+H\)).275 E
(bytes per round-trip time, of application data.)100.8 397 Q
(The TCP host SHOULD set its congestion windo)100.8 423 Q 2.75(wc)-.275
G(wnd to QS-cwnd only if QS-cwnd is)-2.75 E
(greater than cwnd; otherwise QS-cwnd is ignored.)100.8 436 Q
(If QS-cwnd is used, the TCP host sets a)5.5 E(\215ag that it is in Qui\
ck-Start mode, and while in Quick-Start mode the TCP sender MUST)100.8
449 Q(use rate-based pacing to pace out Quick-Start pack)100.8 462 Q
(ets at the speci\214ed Rate Request.)-.11 E
(Quick-Start mode ends when the TCP host recei)100.8 475 Q -.165(ve)
-.275 G 2.75(sa).165 G 2.75(nA)-2.75 G(CK for one of the Quick-Start)
-3.19 E(pack)100.8 488 Q(ets.)-.11 E(If the congestion windo)100.8 514 Q
2.75(wh)-.275 G(as not been fully used when the \214rst ack arri)-2.75 E
-.165(ve)-.275 G 2.75(se).165 G(nding the)-2.75 E
(Quick-Start mode, then the congestion windo)100.8 527 Q 2.75(wi)-.275 G
2.75(sd)-2.75 G(ecreased to the amount that has actually)-2.75 E
(been used so f)100.8 540 Q(ar)-.11 E 5.5(.T)-.605 G
(his addresses the problem of an o)-5.5 E -.165(ve)-.165 G(rly-lar).165
E(ge congestion windo)-.198 E 2.75(wf)-.275 G(rom)-2.75 E(an o)100.8 553
Q -.165(ve)-.165 G(rly-lar).165 E
(ge measurement of the round-trip time.)-.198 E
(If the Quick-Start mode ends with all Quick-Start pack)100.8 579 Q
(ets being successfully)-.11 E(ackno)100.8 592 Q
(wledged, the TCP sender returns to using the def)-.275 E
(ault congestion control mechanisms.)-.11 E(After all the pack)100.8 605
Q(ets are ackno)-.11 E
(wledged from a Quick-Start request for an initial windo)-.275 E -.715
(w,)-.275 G(for e)100.8 618 Q(xample, the TCP sender remains in slo)
-.165 E(w-start, if permitted by ssthresh, continuing to)-.275 E
(increase its congestion windo)100.8 631 Q 2.75(wr)-.275 G
(ather aggressi)-2.75 E -.165(ve)-.275 G
(ly from one round-trip time to the ne).165 E(xt.)-.165 E 1.76 -.88
(To a)100.8 644 T(dd rob).88 E
(ustness, the TCP sender MUST use Limited Slo)-.22 E
(w-Start [RFC3742] along with)-.275 E 2.75(Quick-Start. W)100.8 657 R
(ith Limited Slo)-.44 E
(w-Start, the TCP sender limits the number of pack)-.275 E(ets by)-.11 E
(which the congestion windo)100.8 670 Q 2.75(wi)-.275 G 2.75(si)-2.75 G
(ncreased for one windo)-2.75 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata during slo)-2.75 E(w-start.)-.275 E(Jain/Flo)72 769 Q 204.025
(yd/Allman/Sarolahti Section)-.11 F 2.75(4.4. [P)2.75 F(age 20])-.165 E
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Times-Bold@0 SF(4.5.)72 85 Q/F2 13/Times-Bold@0 SF
(TCP: Responding to a Loss of a Quick-Start P)5.5 E(ack)-.13 E(et)-.13 E
F0 -.165(Fo)100.8 111 S 2.75(rT).165 G(CP)-2.75 E 2.75(,w)-1.221 G 2.75
(eh)-2.75 G -2.475 -.22(av e)-2.75 H(de\214ned a `)2.97 E
(`Quick-Start pack)-.814 E(et')-.11 E 2.75('a)-.814 G 2.75(so)-2.75 G
(ne of the pack)-2.75 E(ets sent in the windo)-.11 E(w)-.275 E
(immediately follo)100.8 124 Q(wing a successful Quick-Start request.)
-.275 E(After detecting the loss of a)5.5 E(Quick-Start pack)100.8 137 Q
(et, TCP MUST re)-.11 E -.165(ve)-.275 G(rt to the def).165 E
(ault congestion control procedures that)-.11 E -.11(wo)100.8 150 S
(uld ha).11 E .33 -.165(ve b)-.22 H
(een used if the Quick-Start request had not been appro).165 E -.165(ve)
-.165 G 2.75(d. F).165 F(or e)-.165 E(xample, if)-.165 E
(Quick-Start is used for setting the initial windo)100.8 163 Q 1.43
-.715(w, a)-.275 H(nd a pack).715 E(et from the initial windo)-.11 E
2.75(wi)-.275 G(s)-2.75 E(lost, then the TCP sender MUST then slo)100.8
176 Q(w-start with the def)-.275 E(ault initial windo)-.11 E 2.75(wt)
-.275 G(hat w)-2.75 E(ould)-.11 E(ha)100.8 189 Q .33 -.165(ve b)-.22 H
(een used if Quick-Start had not been used.).165 E(In addition to re)5.5
E -.165(ve)-.275 G(rting to the def).165 E(ault)-.11 E
(congestion control mechanisms, the sender must tak)100.8 202 Q 2.75(ei)
-.11 G(nto account that the Quick-Start)-2.75 E(congestion windo)100.8
215 Q 2.75(ww)-.275 G(as too lar)-2.86 E 2.75(ge. Thus,)-.198 F
(the sender should decrease ssthresh to at most)2.75 E
(half the number of Quick-Start pack)100.8 228 Q
(ets that were successfully transmitted.)-.11 E(Section A.5)5.5 E
(discusses possible alternati)100.8 241 Q -.165(ve)-.275 G 2.75(si).165
G 2.75(nr)-2.75 G(esponding to the loss of a Quick-Start pack)-2.75 E
(et.)-.11 E 1.76 -.88(We n)100.8 267 T
(ote that ECN [RFC3168] can be used with Quick-Start.).88 E(As is al)5.5
E -.11(wa)-.11 G(ys the case with).11 E(ECN, the sender')100.8 280 Q
2.75(sc)-.605 G(ongestion control response to an ECN-mark)-2.75 E
(ed Quick-Start pack)-.11 E(et is the)-.11 E
(same as the response to a dropped Quick-Start pack)100.8 293 Q
(et, thus re)-.11 E -.165(ve)-.275 G(rting to slo).165 E 2.75(ws)-.275 G
(tart in the)-2.75 E(case of Quick-Start pack)100.8 306 Q(ets mark)-.11
E(ed as e)-.11 E(xperiencing congestion.)-.165 E F1(4.6.)72 345 Q F2
(TCP: A Quick-Start Request f)5.5 E(or a Lar)-.325 E(ger Initial W)-.13
E(indo)-.234 E(w)-.13 E F0(Some of the issues of using Quick-Start are \
related to the speci\214c scenario in which Quick-)100.8 371 Q
(Start is used.)100.8 384 Q(This section discusses the follo)5.5 E
(wing issues that arise when Quick-Start is)-.275 E
(used by TCP to request a lar)100.8 397 Q(ger initial windo)-.198 E
(w: \(1\) determining the rate to request; \(2\))-.275 E
(interactions with P)100.8 410 Q(ath MTU Disco)-.165 E -.165(ve)-.165 G
(ry; and \(3\) Quick-Start request pack).165 E(ets that are)-.11 E
(discarded by middlebox)100.8 423 Q(es.)-.165 E F1 2.75
(4.6.1. Determining)72 462 R(the Rate to Request)2.75 E F0
(As discussed in [SAF05], the data sender does not necessarily ha)100.8
488 Q .33 -.165(ve i)-.22 H(nformation about the).165 E
(size of the data transfer at connection initiation; for e)100.8 501 Q
(xample, in request-response protocols)-.165 E(such as HTTP)100.8 514 Q
2.75(,t)-1.221 G(he serv)-2.75 E(er doesn')-.165 E 2.75(tk)-.198 G(no)
-2.75 E 2.75(wt)-.275 G(he size or name of the requested object during)
-2.75 E(connection initiation.)100.8 527 Q([SAF05] e)5.5 E
(xplores some of the performance implications of o)-.165 E -.165(ve)
-.165 G(rly-).165 E(lar)100.8 540 Q(ge Quick-Start requests, and discus\
ses heuristics that end-nodes could use to size their)-.198 E
(requests appropriately)100.8 553 Q 5.5(.F)-.715 G(or e)-5.665 E
(xample, the sender might ha)-.165 E .33 -.165(ve i)-.22 H
(nformation about the).165 E
(bandwidth of the last-mile hop, the size of the local sock)100.8 566 Q
(et b)-.11 E(uf)-.22 E(fer)-.275 E 2.75(,o)-.44 G 2.75(ro)-2.75 G 2.75
(ft)-2.75 G(he TCP recei)-2.75 E -.165(ve)-.275 G(windo)100.8 579 Q 1.43
-.715(w, a)-.275 H
(nd could use this information in determining the rate to request.).715
E -.88(We)5.5 G 2.75(bs).88 G(erv)-2.75 E(ers)-.165 E(that mostly ha)
100.8 592 Q .33 -.165(ve s)-.22 H(mall objects to transfer might decide\
 not to use Quick-Start at all, since).165 E(Quick-Start w)100.8 605 Q
(ould be of little bene\214t to them.)-.11 E
(In the absence of other information, there could be a con\214gured v)
100.8 631 Q(alue for the Quick-Start)-.275 E(Rate Request.)100.8 644 Q
(Quick-Start will be more ef)5.5 E(fecti)-.275 E .33 -.165(ve i)-.275 H
2.75(fQ).165 G(uick-Start requests are not lar)-2.75 E(ger than)-.198 E
2.75(necessary; e)100.8 657 R -.165(ve)-.275 G
(ry Quick-Start request that is appro).165 E -.165(ve)-.165 G 2.75(db)
.165 G(ut not used \(or not fully used\) tak)-2.97 E(es)-.11 E -2.53
-.165(aw a)100.8 670 T 2.75(yf).165 G(rom the bandwidth pool a)-2.75 E
-.275(va)-.22 G(ilable for granting successi).275 E .33 -.165(ve Q)-.275
H(uick-Start requests.).165 E(Therefore, it is recommended that the req\
uest for the initial sending rate be some)100.8 683 Q(what)-.275 E
(conserv)100.8 696 Q(ati)-.275 E -.165(ve)-.275 G 2.75(,i).165 G 2.75
(no)-2.75 G(rder to impro)-2.75 E .33 -.165(ve t)-.165 H
(he chances for more Quick-Start requests to be).165 E(appro)100.8 709 Q
-.165(ve)-.165 G(d.).165 E(Jain/Flo)72 769 Q 195.775
(yd/Allman/Sarolahti Section)-.11 F 2.75(4.6.1. [P)2.75 F(age 21])-.165
E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Times-Bold@0 SF 2.75(4.6.2. Interactions)72 85 R(with P)2.75 E
(ath MTU Disco)-.11 E -.11(ve)-.11 G(ry).11 E F0 2.75(As)100.8 111 S
(econd issue when Quick-Start is used to request a lar)-2.75 E
(ge initial windo)-.198 E 2.75(wc)-.275 G(oncerns the)-2.75 E
(interactions between the lar)100.8 124 Q(ge initial windo)-.198 E 2.75
(wa)-.275 G(nd P)-2.75 E(ath MTU Disco)-.165 E -.165(ve)-.165 G(ry).165
E 5.5(.S)-.715 G(ome of the issues)-5.5 E(are discussed in RFC 3390:)
100.8 137 Q("When lar)129.6 153.6 Q(ger initial windo)-.198 E
(ws are implemented along with P)-.275 E(ath MTU Disco)-.165 E -.165(ve)
-.165 G(ry).165 E([RFC1191], alternati)129.6 166.6 Q -.165(ve)-.275 G
2.75(sa).165 G(re to set the "Don')-2.75 E 2.75(tF)-.198 G
(ragment" \(DF\) bit in all se)-2.75 E(gments in)-.165 E
(the initial windo)129.6 179.6 Q 1.43 -.715(w, o)-.275 H 2.75(rt).715 G
2.75(os)-2.75 G(et the "Don')-2.75 E 2.75(tF)-.198 G
(ragment" \(DF\) bit in one of the se)-2.75 E 2.75(gments. It)-.165 F
(is an open question as to which of these tw)129.6 192.6 Q 2.75(oa)-.11
G(lternati)-2.75 E -.165(ve)-.275 G 2.75(si).165 G 2.75(sb)-2.75 G
(est.")-2.75 E(Unfortunately)100.8 209.2 Q 2.75(,t)-.715 G
(he sender doesn')-2.75 E 2.75(tn)-.198 G(ecessarily kno)-2.75 E 2.75
(wt)-.275 G(he P)-2.75 E(ath MTU when it sends pack)-.165 E(ets in)-.11
E(the initial windo)100.8 222.2 Q 4.18 -.715(w. T)-.275 H
(he sender should be conserv).715 E(ati)-.275 E .33 -.165(ve i)-.275 H
2.75(nt).165 G(he pack)-2.75 E(et size used.)-.11 E(Sending a)5.5 E(lar)
100.8 235.2 Q(ge number of o)-.198 E -.165(ve)-.165 G(rly-lar).165 E
(ge pack)-.198 E(ets with the DF bit set is not desirable, b)-.11 E
(ut sending a)-.22 E(lar)100.8 248.2 Q(ge number of pack)-.198 E
(ets that are fragmented in the netw)-.11 E
(ork can be equally undesirable.)-.11 E(One possibility w)100.8 274.2 Q
(ould be for the sender to send one lar)-.11 E(ge pack)-.198 E
(et in the initial windo)-.11 E 2.75(ww)-.275 G(ith)-2.75 E
(the DF bit set, and to send the remaining pack)100.8 287.2 Q
(ets in the initial windo)-.11 E 2.75(ww)-.275 G(ith a smaller MTU)-2.75
E(of 576 bytes \(or 1280 bytes with IPv6\).)100.8 300.2 Q 2.75(As)100.8
326.2 S(econd possibility w)-2.75 E
(ould be for the sender to delay sending the Quick-Start Request for)
-.11 E(one round-trip time, sending the Quick-Start Request with the \
\214rst windo)100.8 339.2 Q 2.75(wo)-.275 G 2.75(fd)-2.75 G(ata while)
-2.75 E(also doing P)100.8 352.2 Q(ath MTU Disco)-.165 E -.165(ve)-.165
G(ry).165 E(.)-.715 E
(In the future, it might be possible for the TCP SYN pack)100.8 378.2 Q
(et to do a probe about the P)-.11 E(ath)-.165 E 2.75(MTU. F)100.8 391.2
R(or e)-.165 E(xample, [W03] has proposed an IP Option that queries rou\
ters for their MTU)-.165 E(before starting a P)100.8 404.2 Q
(ath MTU Disco)-.165 E -.165(ve)-.165 G(ry process.).165 E F1 2.75
(4.6.3. Quick-Start)72 443.2 R(Request P)2.75 E(ack)-.11 E(ets that ar)
-.11 E 2.75(eD)-.198 G(iscarded by Middleboxes)-2.75 E F0(It is al)100.8
469.2 Q -.11(wa)-.11 G(ys possible for a TCP SYN pack).11 E
(et carrying a Quick-Start request to be dropped in)-.11 E(the netw)
100.8 482.2 Q(ork due to congestion, or to be block)-.11 E
(ed due to interactions with middlebox)-.11 E(es.)-.165 E(Measurement s\
tudies of interactions between transport protocols and middlebox)100.8
495.2 Q(es)-.165 E([MAF04] sho)100.8 508.2 Q 2.75(wt)-.275 G
(hat for 70% of the web serv)-2.75 E(ers in)-.165 E -.165(ve)-.44 G
(stig).165 E(ated, no connection is established if)-.055 E
(the TCP SYN pack)100.8 521.2 Q(et contains an unkno)-.11 E
(wn IP option \(and for 43% of the web serv)-.275 E(ers, no)-.165 E
(connection is established if the TCP SYN pack)100.8 534.2 Q
(et contains an IP T)-.11 E(imeStamp Option\).)-.385 E(In)5.5 E
(both cases, this is presumably due to middlebox)100.8 547.2 Q
(es along that path.)-.165 E(If the TCP sender doesn')100.8 573.2 Q 2.75
(tr)-.198 G(ecei)-2.75 E .33 -.165(ve a r)-.275 H
(esponse to the SYN or SYN/A).165 E(CK pack)-.44 E(et containing)-.11 E
(the Quick-Start Request, then the TCP sender SHOULD resend the SYN or \
SYN/A)100.8 586.2 Q(CK)-.44 E(pack)100.8 599.2 Q
(et without the Quick-Start Request.)-.11 E(Similarly)5.5 E 2.75(,i)
-.715 G 2.75(ft)-2.75 G(he TCP sender recei)-2.75 E -.165(ve)-.275 G
2.75(saT).165 G(CP reset)-2.75 E(in response to the SYN or SYN/A)100.8
612.2 Q(CK pack)-.44 E(et containing the Quick-Start Request, then the)
-.11 E(TCP sender SHOULD resend the SYN or SYN/A)100.8 625.2 Q(CK pack)
-.44 E(et without the Quick-Start)-.11 E(Request [RFC3360].)100.8 638.2
Q(While RFC 1122 and 2988 recommend that the sender should set the init\
ial R)100.8 664.2 Q .396 -.198(TO t)-.66 H 2.75(ot).198 G(hree)-2.75 E
(seconds, man)100.8 677.2 Q 2.75(yT)-.165 G
(CP implementations set the initial R)-2.75 E .396 -.198(TO t)-.66 H
2.75(oo).198 G(ne second.)-2.75 E -.165(Fo)5.5 G 2.75(raT).165 G(CP SYN)
-2.75 E(pack)100.8 690.2 Q
(et sent with a Quick-Start request, we RECOMMEND an R)-.11 E .396 -.198
(TO o)-.66 H 2.75(fo).198 G(ne second, so that)-2.75 E
(the sender can retransmit the SYN pack)100.8 703.2 Q
(et reasonably promptly if the original TCP SYN)-.11 E(pack)100.8 716.2
Q(et is dropped by a middlebox in the netw)-.11 E(ork.)-.11 E(Jain/Flo)
72 769 Q 195.775(yd/Allman/Sarolahti Section)-.11 F 2.75(4.6.3. [P)2.75
F(age 22])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(In the \
case of a retransmission, in addition to resending the SYN or SYN/A)
100.8 85 Q(CK pack)-.44 E(et)-.11 E
(without the Quick-Start Request, the TCP sender SHOULD use an R)100.8
98 Q .396 -.198(TO o)-.66 H 2.75(ft).198 G(hree seconds)-2.75 E
(and a dif)100.8 111 Q(ferent Initial Sequence Number)-.275 E 5.5(.U)
-.605 G(sing this scheme the TCP sender MUST k)-5.5 E(eep)-.11 E
(track of when each of the SYN \(or SYN/A)100.8 124 Q(CKs\) w)-.44 E
(as transmitted.)-.11 E(In this w)5.5 E(ay)-.11 E 2.75(,a)-.715 G(n)
-2.75 E(ackno)100.8 137 Q(wledgement for the retransmitted SYN or SYN/A)
-.275 E(CK pack)-.44 E(et can be matched with the)-.11 E(SYN or SYN/A)
100.8 150 Q(CK being ackno)-.44 E
(wledged, and the transmission time of the SYN \(or)-.275 E(SYN/A)100.8
163 Q(CK\) being ackno)-.44 E(wledged can be used for an R)-.275 E
(TT measurement to seed the R)-.66 E -.198(TO)-.66 G 5.5(.I).198 G(f)
-5.5 E(only the retransmitted SYN or SYN/A)100.8 176 Q(CK is ackno)-.44
E(wledged, the TCP sender can reasonably)-.275 E
(assume that the earlier SYN or SYN/A)100.8 189 Q
(CK with the Quick-Start option w)-.44 E(as dropped by the)-.11 E(netw)
100.8 202 Q(ork because of the option and not because of congestion.)
-.11 E(In this case, the TCP sender)5.5 E
(can refrain from performing TCP')100.8 215 Q 2.75(ss)-.605 G
(tandard congestion control state changes.)-2.75 E 1.76 -.88(We n)100.8
241 T(ote that if the TCP SYN pack).88 E
(et is using the IP Quick-Start Option for a Quick-Start)-.11 E
(request, and it is also using bits in the TCP header to ne)100.8 254 Q
(gotiate ECN-capability with the)-.165 E
(TCP host at the other end, then the drop of a TCP SYN pack)100.8 267 Q
(et could be due to congestion,)-.11 E(to a middlebox dropping the pack)
100.8 280 Q(et because of the IP Option, or because of a middlebox)-.11
E(dropping the pack)100.8 293 Q
(et because of the information in the TCP header ne)-.11 E
(gotiating ECN.)-.165 E(In this)5.5 E
(case, the sender could resend the dropped pack)100.8 306 Q
(et without either the Quick-Start or the ECN)-.11 E 2.75
(requests. Alternately)100.8 319 R 2.75(,t)-.715 G
(he sender could resend the dropped pack)-2.75 E(et with only the ECN)
-.11 E(request in the TCP header)100.8 332 Q 2.75(,r)-.44 G
(esending the TCP SYN pack)-2.75 E(et without either the Quick-Start)
-.11 E(or the ECN requests if the second TCP SYN pack)100.8 345 Q
(et is dropped.)-.11 E(The second choice seems)5.5 E(reasonable, gi)
100.8 358 Q -.165(ve)-.275 G 2.75(nt).165 G(hat a TCP SYN pack)-2.75 E
(et today is more lik)-.11 E(ely to be block)-.11 E(ed due to IP)-.11 E
(Options than due to an ECN request in the TCP header [MAF04].)100.8 371
Q/F1 11/Times-Bold@0 SF(4.7.)72 410 Q/F2 13/Times-Bold@0 SF
(TCP: A Quick-Start Request in the Middle of Connection)5.5 E F0
(This section discusses the follo)100.8 436 Q
(wing issues that arise when Quick-Start is used by TCP to)-.275 E
(request a lar)100.8 449 Q(ger windo)-.198 E 2.75(wi)-.275 G 2.75(nt)
-2.75 G(he middle of connection, for e)-2.75 E
(xample after an idle period: \(1\))-.165 E(determining the rate to req\
uest; and \(2\) the response if Quick-Start pack)100.8 462 Q
(ets are dropped;)-.11 E(\(1\) Determining the rate to request:)100.8
488 Q(In the middle of connection, an easy rule of thumb w)100.8 501 Q
(ould be for the TCP sender to)-.11 E(determine the lar)100.8 514 Q
(gest congestion windo)-.198 E 2.75(wt)-.275 G
(hat the TCP connection achie)-2.75 E -.165(ve)-.275 G 2.75(ds).165 G
(ince the last)-2.75 E(pack)100.8 527 Q
(et drop, to translate this congestion windo)-.11 E 2.75(wt)-.275 G 2.75
(oas)-2.75 G(ending rate, and use this rate in the)-2.75 E
(Quick-Start request.)100.8 540 Q(If the request is granted, then the s\
ender essentially restarts with its)5.5 E(old congestion windo)100.8 553
Q 2.75(wf)-.275 G(rom before it w)-2.75 E(as reduced, for e)-.11 E
(xample during an idle period.)-.165 E
(In the case of an idle period, the sender SHOULD NO)100.8 579 Q 2.75
(Tu)-.44 G(se Quick-Start if the idle period)-2.75 E
(has been less than an R)100.8 592 Q -.198(TO)-.66 G 2.75(,a).198 G
(nd the congestion windo)-2.75 E 2.75(wh)-.275 G(as not decayed do)-2.75
E(wn to less than)-.275 E(half of its v)100.8 605 Q
(alue at the start of the idle period.)-.275 E
(Such a use of Quick-Start requires further)5.5 E(in)100.8 618 Q -.165
(ve)-.44 G(stig).165 E(ation.)-.055 E
(\(2\) Response if Quick-Start pack)100.8 644 Q(ets are dropped:)-.11 E
(If Quick-Start pack)100.8 657 Q
(ets are dropped in the middle of connection, then the sender MUST)-.11
E(re)100.8 670 Q -.165(ve)-.275 G(rt to half of the Quick-Start windo)
.165 E 1.43 -.715(w, o)-.275 H 2.75(rt).715 G 2.75(ot)-2.75 G
(he congestion windo)-2.75 E 2.75(wt)-.275 G(hat the sender)-2.75 E -.11
(wo)100.8 683 S(uld ha).11 E .33 -.165(ve u)-.22 H
(sed if the Quick-Start request had not been appro).165 E -.165(ve)-.165
G(d, whiche).165 E -.165(ve)-.275 G 2.75(ri).165 G 2.75(ss)-2.75 G
(maller)-2.75 E(.)-.605 E 1.76 -.88(We n)100.8 709 T(ote that a pack).88
E(et in the middle of a connection carrying a Quick-Start Request might)
-.11 E(or might not carry a data payload.)100.8 722 Q -.165(Fo)5.5 G
2.75(re).165 G(xample, for TCP)-2.915 E 2.75(,t)-1.221 G
(he Quick-Start Request could be)-2.75 E(Jain/Flo)72 769 Q 204.025
(yd/Allman/Sarolahti Section)-.11 F 2.75(4.7. [P)2.75 F(age 23])-.165 E
0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(carried by a data pack)100.8 85 Q(et, or by a pure ackno)-.11 E
(wledgement pack)-.275 E(et.)-.11 E/F1 11/Times-Bold@0 SF(4.8.)72 124 Q
/F2 13/Times-Bold@0 SF(An Example Quick-Start Scenario with TCP)5.5 E F0
(The follo)100.8 150 Q(wing is an e)-.275 E
(xample scenario in the case when both hosts request Quick-Start for)
-.165 E(setting their initial windo)100.8 163 Q(ws:)-.275 E 2.75(*T)
100.8 189 S(he TCP SYN pack)-2.75 E
(et from Host A contains a Quick-Start Request in the IP header)-.11 E
(.)-.605 E 2.75(*R)100.8 215 S(outers along the forw)-2.75 E
(ard path modify the Quick-Start Request as appropriate.)-.11 E 2.75(*H)
100.8 241 S(ost B recei)-2.75 E -.165(ve)-.275 G 2.75(st).165 G
(he Quick-Start Request in the SYN pack)-2.75 E
(et, and calculates the TTL Dif)-.11 E(f.)-.275 E(If Host B appro)100.8
254 Q -.165(ve)-.165 G 2.75(st).165 G
(he Quick-Start Request, then Host B sends a Quick-Start Response in)
-2.75 E(the TCP header of the SYN/A)100.8 267 Q(CK pack)-.44 E 2.75
(et. Host)-.11 F 2.75(Ba)2.75 G(lso sends a Quick-Start Request in the)
-2.75 E(IP header of the SYN/A)100.8 280 Q(CK pack)-.44 E(et.)-.11 E
2.75(*R)100.8 306 S(outers along the re)-2.75 E -.165(ve)-.275 G
(rse path modify the Quick-Start Request as appropriate.).165 E 2.75(*H)
100.8 332 S(ost A recei)-2.75 E -.165(ve)-.275 G 2.75(st).165 G
(he Quick-Start Response in the SYN/A)-2.75 E(CK pack)-.44 E
(et, and checks the TTL)-.11 E(Dif)100.8 345 Q 2.75(fa)-.275 G
(nd Rate Request for v)-2.75 E(alidity)-.275 E 5.5(.I)-.715 G 2.75(ft)
-5.5 G(he)-2.75 E 2.75(ya)-.165 G(re v)-2.75 E
(alid, then Host A sets its initial congestion)-.275 E(windo)100.8 358 Q
2.75(wa)-.275 G(ppropriately)-2.75 E 2.75(,a)-.715 G
(nd sets up rate-based pacing to be used with the initial windo)-2.75 E
4.18 -.715(w. I)-.275 H(f).715 E(the Quick-Start Response is not v)100.8
371 Q(alid, then Host A uses TCP')-.275 E 2.75(sd)-.605 G(ef)-2.75 E
(ault initial windo)-.11 E -.715(w.)-.275 G
(Host A also calculates the TTL Dif)100.8 397 Q 2.75(ff)-.275 G
(or the Quick-Start Request in the incoming)-2.75 E(SYN/A)100.8 410 Q
(CK pack)-.44 E
(et, and sends a Quick-Start Response in the TCP header of the A)-.11 E
(CK)-.44 E(pack)100.8 423 Q(et.)-.11 E 2.75(*H)100.8 449 S(ost B recei)
-2.75 E -.165(ve)-.275 G 2.75(st).165 G(he Quick-Start Response in an A)
-2.75 E(CK pack)-.44 E(et, and checks the TTL Dif)-.11 E(f)-.275 E
(and Rate Request for v)100.8 462 Q(alidity)-.275 E 5.5(.I)-.715 G 2.75
(ft)-5.5 G(he Quick-Start Response is v)-2.75 E
(alid, then Host B sets its)-.275 E(initial congestion windo)100.8 475 Q
2.75(wa)-.275 G(ppropriately)-2.75 E 2.75(,a)-.715 G
(nd sets up rate-based pacing to be used with its)-2.75 E(initial windo)
100.8 488 Q 4.18 -.715(w. I)-.275 H 2.75(ft).715 G
(he Quick-Start Response is not v)-2.75 E(alid, then Host B uses TCP')
-.275 E 2.75(sd)-.605 G(ef)-2.75 E(ault)-.11 E(initial windo)100.8 501 Q
-.715(w.)-.275 G F1(5.)72 540 Q/F3 14/Times-Bold@0 SF
(The Quick-Start Mechanism in other T)5.5 E(ransport Pr)-1.036 E
(otocols)-.252 E F0
(The section earlier speci\214ed the use of Quick-Start in TCP)100.8 566
Q 5.5(.I)-1.221 G 2.75(nt)-5.5 G(his section, we generalize)-2.75 E
(this to gi)100.8 579 Q .33 -.165(ve g)-.275 H
(uidelines for the use of Quick-Start with other transport protocols.)
.165 E 1.76 -.88(We a)5.5 H(lso).88 E(discuss brie\215y ho)100.8 592 Q
2.75(wQ)-.275 G
(uick-Start could be speci\214ed for other transport protocols.)-2.75 E
(The general guidelines for Quick-Start in transport protocols are as f\
ollo)100.8 618 Q(ws:)-.275 E 2.75(*Q)100.8 644 S(uick-Start is only spe\
ci\214ed for unicast transport protocols with appropriate congestion)
-2.75 E(control mechanisms.)100.8 657 Q
(Note: Quick-Start is not a replacement for standard congestion)5.5 E
(control techniques, b)100.8 670 Q(ut meant to augment their operation.)
-.22 E 2.75(*At)100.8 696 S(ransport-le)-2.75 E -.165(ve)-.275 G 2.75
(lm).165 G
(echanism is needed for the Quick-Start response from the recei)-2.75 E
-.165(ve)-.275 G 2.75(rt).165 G(o)-2.75 E(the sender)100.8 709 Q 5.5(.T)
-.605 G(his response contains the Rate Request and the TTL Dif)-5.5 E
(f.)-.275 E(Jain/Flo)72 769 Q 212.275(yd/Allman/Sarolahti Section)-.11 F
2.75(5. [P)2.75 F(age 24])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E 2.75(*T)
100.8 85 S(he sender checks the v)-2.75 E
(alidity of the Quick-Start response.)-.275 E 2.75(*T)100.8 111 S(he se\
nder has an estimate of the round-trip time, and translates the Quick-S\
tart response)-2.75 E(into an allo)100.8 124 Q(wed windo)-.275 E 2.75
(wo)-.275 G 2.75(ra)-2.75 G(llo)-2.75 E(wed sending rate.)-.275 E
(The sender starts sending Quick-Start)5.5 E(pack)100.8 137 Q
(ets, rate-paced out at the appro)-.11 E -.165(ve)-.165 G 2.75(ds).165 G
(ending rate.)-2.75 E 2.75(*A)100.8 163 S(fter the sender recei)-2.75 E
-.165(ve)-.275 G 2.75(st).165 G(he \214rst ackno)-2.75 E
(wledgement pack)-.275 E(et for a Quick-Start pack)-.11 E(et, no)-.11 E
(more Quick-Start pack)100.8 176 Q(ets are sent.)-.11 E
(The sender adjusts its current congestion windo)5.5 E 2.75(wo)-.275 G
(r)-2.75 E
(sending rate to be consistent with the actual amount of data that w)
100.8 189 Q(as transmitted in that)-.11 E(round-trip time.)100.8 202 Q
2.75(*W)100.8 228 S(hen the last Quick-Start pack)-2.75 E(et is ackno)
-.11 E(wledged, the sender continues using the)-.275 E
(standard congestion control mechanisms of that protocol.)100.8 241 Q
2.75(*I)100.8 267 S 2.75(fo)-2.75 G(ne of the Quick-Start pack)-2.75 E
(ets is lost, then the sender re)-.11 E -.165(ve)-.275 G
(rts to the standard congestion).165 E
(control method of that protocol that w)100.8 280 Q(ould ha)-.11 E .33
-.165(ve b)-.22 H(een used if the Quick-Start request had).165 E
(not been appro)100.8 293 Q -.165(ve)-.165 G 2.75(d. In).165 F
(addition, the sender tak)2.75 E
(es into account the information that the)-.11 E
(Quick-Start congestion windo)100.8 306 Q 2.75(ww)-.275 G(as too lar)
-2.86 E(ge \(e.g., by decreasing ssthresh in TCP\).)-.198 E/F1 11
/Times-Bold@0 SF(6.)72 345 Q/F2 14/Times-Bold@0 SF(Ev)5.5 E
(aluation of Quick-Start)-.14 E F1(6.1.)72 384 Q/F3 13/Times-Bold@0 SF
(Bene\214ts of Quick-Start)5.5 E F0
(The main bene\214t of Quick-Start is the f)100.8 410 Q
(aster start-up for the transport connection itself.)-.11 E -.165(Fo)5.5
G(r).165 E 2.75(as)100.8 423 S(mall TCP transfer of one to \214v)-2.75 E
2.75(ep)-.165 G(ack)-2.75 E(ets, Quick-Start is probably of v)-.11 E
(ery little bene\214t;)-.165 E(at)5.5 E
(best, it might shorten the connection lifetime from three to tw)100.8
436 Q 2.75(or)-.11 G(ound-trip times \(including)-2.75 E
(the round-trip time for connection establishment\).)100.8 449 Q
(Similarly)5.5 E 2.75(,f)-.715 G(or a v)-2.75 E(ery lar)-.165 E
(ge transfer)-.198 E(,)-.44 E(where the slo)100.8 462 Q(w-start phase w)
-.275 E(ould ha)-.11 E .33 -.165(ve b)-.22 H
(een only a small fraction of the connection).165 E
(lifetime, Quick-Start w)100.8 475 Q(ould be of limited bene\214t.)-.11
E(Quick-Start w)5.5 E(ould not signi\214cantly)-.11 E
(shorten the connection lifetime, b)100.8 488 Q
(ut it might eliminate or at least shorten the start-up phase.)-.22 E
(Ho)100.8 501 Q(we)-.275 E -.165(ve)-.275 G .88 -.44(r, f).165 H
(or moderate-sized connections in a well-pro).44 E(visioned en)-.165 E
(vironment, Quick-Start)-.44 E(could possibly allo)100.8 514 Q 2.75(wt)
-.275 G(he entire transfer of M pack)-2.75 E
(ets to be completed in one round-trip)-.11 E
(time \(after the initial round-trip time for the SYN e)100.8 527 Q
(xchange\), instead of the log_2\(M\)-2)-.165 E
(round-trip times that it w)100.8 540 Q(ould normally tak)-.11 E 2.75
(ef)-.11 G(or the data transfer)-2.75 E 2.75(,i)-.44 G 2.75(na)-2.75 G
2.75(nu)-2.75 G(ncongested)-2.75 E(en)100.8 553 Q
(vironments \(assuming an initial windo)-.44 E 2.75(wo)-.275 G 2.75(ff)
-2.75 G(our pack)-2.75 E(ets\).)-.11 E F1(6.2.)72 592 Q F3
(Costs of Quick-Start)5.5 E F0(This section discusses the costs of Quic\
k-Start for the connection and for the routers along)100.8 618 Q
(the path.)100.8 631 Q(The cost of ha)100.8 657 Q
(ving a Quick-Start pack)-.22 E(et dropped:)-.11 E -.165(Fo)100.8 670 S
2.75(rt).165 G(he sender the biggest risk in using Quick-Start lies in \
the possibility of suf)-2.75 E(fering from)-.275 E
(congestion-related losses of the Quick-Start pack)100.8 683 Q 2.75
(ets. This)-.11 F(should be an unlik)2.75 E(ely situation)-.11 E
(because routers are e)100.8 696 Q(xpected to appro)-.165 E .33 -.165
(ve Q)-.165 H(uick-Start Requests only when the).165 E 2.75(ya)-.165 G
(re)-2.75 E(signi\214cantly underutilized. Ho)100.8 709 Q(we)-.275 E
-.165(ve)-.275 G .88 -.44(r, a t).165 H(ransient increase in cross-traf)
.44 E(\214c in one of the)-.275 E(routers, a sudden decrease in a)100.8
722 Q -.275(va)-.22 G
(ilable bandwidth on one of the links, or congestion at a).275 E
(Jain/Flo)72 769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75
(6.2. [P)2.75 F(age 25])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(non-IP queue could result in pack)100.8 85 Q(et losses e)-.11 E -.165
(ve)-.275 G 2.75(nw).165 G(hen the Quick-Start Request w)-2.75 E(as)-.11
E(appro)100.8 98 Q -.165(ve)-.165 G 2.75(db).165 G 2.75(ya)-2.75 G
(ll of the routers along the path.)-2.75 E(If a Quick-Start pack)5.5 E
(et is dropped, then the)-.11 E(sender re)100.8 111 Q -.165(ve)-.275 G
(rts to the congestion control mechanisms it w).165 E(ould ha)-.11 E .33
-.165(ve u)-.22 H(sed if the Quick-Start).165 E
(request has not been appro)100.8 124 Q -.165(ve)-.165 G
(d, so the performance cost to the connection of ha).165 E(ving a)-.22 E
(Quick-Start pack)100.8 137 Q
(et dropped is small, compared to the performance without Quick-Start.)
-.11 E(\(On the other hand, the performance dif)100.8 150 Q
(ference between Quick-Start with a Quick-Start)-.275 E(pack)100.8 163 Q
(et dropped and Quick-Start with no Quick-Start pack)-.11 E
(et dropped can be considerable.\))-.11 E(Added comple)100.8 189 Q
(xity at routers:)-.165 E(The main cost of Quick-Start at routers conce\
rns the costs of added comple)100.8 202 Q(xity)-.165 E 5.5(.T)-.715 G
(he added)-5.5 E(comple)100.8 215 Q(xity at the end-points is moderate,\
 and might easily be outweighed by the bene\214t of)-.165 E
(Quick-Start to the end hosts.)100.8 228 Q(The added comple)5.5 E
(xity at the routers is also some)-.165 E(what)-.275 E(moderate; it in)
100.8 241 Q -.22(vo)-.44 G(lv).22 E
(es estimating the unused bandwidth on the output link o)-.165 E -.165
(ve)-.165 G 2.75(rt).165 G(he last)-2.75 E(se)100.8 254 Q -.165(ve)-.275
G(ral seconds, processing the Quick-Start request, and k).165 E
(eeping a counter of the aggre)-.11 E -.055(ga)-.165 G(te).055 E
(Quick-Start rate appro)100.8 267 Q -.165(ve)-.165 G 2.75(do).165 G
-.165(ve)-2.915 G 2.75(rt).165 G(he last fraction of a second.)-2.75 E
(Ho)5.5 E(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H(his added).44
E(comple)100.8 280 Q(xity at routers adds to the de)-.165 E -.165(ve)
-.275 G(lopment c).165 E(ycle, and could pre)-.165 E -.165(ve)-.275 G
(nt the addition of).165 E(other competing functionality to routers.)
100.8 293 Q(Thus, careful thought w)5.5 E(ould ha)-.11 E .33 -.165(ve t)
-.22 H 2.75(ob).165 G 2.75(eg)-2.75 G -2.365 -.275(iv e)-2.75 H 2.75(nt)
.275 G(o)-2.75 E(the addition of Quick-Start to IP)100.8 306 Q(.)-1.221
E(The slo)100.8 332 Q 2.75(wp)-.275 G(ath in routers:)-2.75 E
(Another dra)100.8 345 Q(wback of Quick-Start is that pack)-.165 E
(ets containing the Quick-Start Request)-.11 E(message might not tak)
100.8 358 Q 2.75(et)-.11 G(he f)-2.75 E
(ast path in routers, particularly in the be)-.11 E(ginning of Quick-)
-.165 E(Start')100.8 371 Q 2.75(sd)-.605 G(eplo)-2.75 E
(yment in the Internet.)-.11 E(This w)5.5 E(ould mean some e)-.11 E
(xtra delay for the end hosts,)-.165 E(and e)100.8 384 Q
(xtra processing b)-.165 E(urden for the routers.)-.22 E(Ho)5.5 E(we)
-.275 E -.165(ve)-.275 G .88 -.44(r, a).165 H 2.75(sd).44 G
(iscussed in Sections 4.1 and 4.6,)-2.75 E(not all pack)100.8 397 Q
(ets w)-.11 E(ould carry the Quick-Start Request option.)-.11 E
(In addition, for the)5.5 E
(underutilized links where Quick-Start Requests could actually be appro)
100.8 410 Q -.165(ve)-.165 G(d, or in typical).165 E(en)100.8 423 Q
(vironments where most of the pack)-.44 E(ets belong to lar)-.11 E
(ge \215o)-.198 E(ws, the b)-.275 E(urden of the Quick-)-.22 E
(Start Option on routers w)100.8 436 Q(ould be considerably reduced.)
-.11 E(Ne)5.5 E -.165(ve)-.275 G(rtheless, it is still).165 E(concei)
100.8 449 Q -.275(va)-.275 G(ble, in the w).275 E(orst case, that man)
-.11 E 2.75(yp)-.165 G(ack)-2.75 E(ets w)-.11 E
(ould carry Quick-Start requests; this)-.11 E(could slo)100.8 462 Q 2.75
(wd)-.275 G -.275(ow)-2.75 G 2.75(nt).275 G
(he processing of Quick-Start pack)-2.75 E(ets in routers considerably)
-.11 E 5.5(.A)-.715 G(s)-5.5 E
(discussed in Section 6.6, routers can easily protect ag)100.8 475 Q
(ainst this by enforcing a limit on the)-.055 E
(rate at which Quick-Start requests will be considered.)100.8 488 Q
(Multiple paths:)100.8 514 Q
(One limitation of Quick-Start is that it presumes that the data pack)
100.8 527 Q(ets of a connection will)-.11 E(follo)100.8 540 Q 2.75(wt)
-.275 G(he same path as the Quick-Start request pack)-2.75 E 2.75
(et. If)-.11 F(this is not the case, then the)2.75 E
(connection could be sending the Quick-Start pack)100.8 553 Q
(ets, at the appro)-.11 E -.165(ve)-.165 G 2.75(dr).165 G
(ate, along a path that)-2.75 E -.11(wa)100.8 566 S 2.75(sa).11 G(lread\
y congested, or that became congested as a result of this connection.)
-2.75 E(This is,)5.5 E(ho)100.8 579 Q(we)-.275 E -.165(ve)-.275 G .88
-.44(r, s).165 H(imilar to what w).44 E(ould happen if the connection')
-.11 E 2.75(sp)-.605 G(ath w)-2.75 E(as changed in the middle)-.11 E(of\
 the connection, when the connection had already established the allo)
100.8 592 Q(wed initial rate.)-.275 E(Non-IP queues:)100.8 618 Q 2.75
(Ap)100.8 631 S(roblem of an)-2.75 E 2.75(ym)-.165 G
(echanism for feedback from routers at the IP le)-2.75 E -.165(ve)-.275
G 2.75(li).165 G 2.75(st)-2.75 G(hat there can be)-2.75 E
(queues and bottlenecks in the end-to-end path that are not in IP-le)
100.8 644 Q -.165(ve)-.275 G 2.75(lr).165 G 2.75(outers. As)-2.75 F(an)
2.75 E -.165(ex)100.8 657 S(ample, these include queues in layer).165 E
(-tw)-.22 E 2.75(oE)-.11 G(thernet or A)-2.75 E(TM netw)-1.221 E 2.75
(orks. One)-.11 F(possibility)2.75 E -.11(wo)100.8 670 S
(uld be that an IP-le).11 E -.165(ve)-.275 G 2.75(lr).165 G
(outer adjacent to such a non-IP queue or bottleneck w)-2.75 E(ould be)
-.11 E(con\214gured to reject Quick-Start requests if that w)100.8 683 Q
(as appropriate.)-.11 E(One w)5.5 E(ould hope that in)-.11 E
(general, IP netw)100.8 696 Q(orks are con\214gured so that non-IP queu\
es between IP routers do not end up)-.11 E
(being the congested bottlenecks.)100.8 709 Q(Jain/Flo)72 769 Q 204.025
(yd/Allman/Sarolahti Section)-.11 F 2.75(6.2. [P)2.75 F(age 26])-.165 E
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Times-Bold@0 SF(6.3.)72 85 Q/F2 13/Times-Bold@0 SF(Pr)5.5 E
(otection against Misbeha)-.234 E(ving Nodes)-.325 E F0
(In this section we discuss the protection ag)100.8 111 Q(ainst recei)
-.055 E -.165(ve)-.275 G(rs or colluding middlebox).165 E(es lying)-.165
E(about the Quick-Start Request.)100.8 124 Q
(First, we note that it is not necessarily in the recei)5.5 E -.165(ve)
-.275 G(r').165 E(s)-.605 E
(interest to lie about the Quick-Start Request.)100.8 137 Q
(If the sender sends at too-high of an initial)5.5 E
(rate, and has a pack)100.8 150 Q
(et dropped, this does not necessarily impro)-.11 E .33 -.165(ve t)-.165
H(he performance of the).165 E(connection, relati)100.8 163 Q .33 -.165
(ve t)-.275 H 2.75(ot).165 G(he case when the Quick-Start Request w)
-2.75 E(as not appro)-.11 E -.165(ve)-.165 G(d.).165 E F1 2.75
(6.3.1. Recei)72 202 R -.11(ve)-.11 G(rs L).11 E
(ying about Whether the Request was A)-.605 E(ppr)-.275 E -.11(ove)-.198
G(d).11 E F0(One form of misbeha)100.8 228 Q(vior w)-.22 E
(ould be for the recei)-.11 E -.165(ve)-.275 G 2.75(rt).165 G 2.75(ol)
-2.75 G(ie to the sender about whether the)-2.75 E
(Quick-Start Request w)100.8 241 Q(as appro)-.11 E -.165(ve)-.165 G
(d, by f).165 E(alsely reporting the TTL Dif)-.11 E 2.75(f. If)-.275 F
2.75(ar)2.75 G(outer that)-2.75 E(understands the Quick-Start Request d\
enies the request by deleting the request or by)100.8 254 Q
(zeroing the QS TTL, then the recei)100.8 267 Q -.165(ve)-.275 G 2.75
(rc).165 G(an `)-2.75 E(`lie" about whether the request w)-.814 E
(as appro)-.11 E -.165(ve)-.165 G(d).165 E
(only by successfully guessing the v)100.8 280 Q(alue of the TTL Dif)
-.275 E 2.75(ft)-.275 G 2.75(or)-2.75 G 2.75(eport. The)-2.75 F
(chance of the)2.75 E(recei)100.8 293 Q -.165(ve)-.275 G 2.75(rs).165 G
(uccessfully guessing the correct v)-2.75 E(alue for the TTL Dif)-.275 E
2.75(fi)-.275 G 2.75(s1)-2.75 G(/256.)-2.75 E(Ho)100.8 319 Q(we)-.275 E
-.165(ve)-.275 G .88 -.44(r, i).165 H 2.75(ft).44 G(he Quick-Start requ\
est is denied only by a non-Quick-Start-capable router)-2.75 E 2.75(,o)
-.44 G(r)-2.75 E
(by a router that is unable to zero the QS TTL \214eld, the the recei)
100.8 332 Q -.165(ve)-.275 G 2.75(rc).165 G(ould lie about whether)-2.75
E(the Quick-Start Requests were appro)100.8 345 Q -.165(ve)-.165 G 2.75
(db).165 G 2.75(ym)-2.75 G(odifying the QS TTL in successi)-2.75 E .33
-.165(ve r)-.275 H(equests).165 E(recei)100.8 358 Q -.165(ve)-.275 G
2.75(df).165 G(rom the same host.)-2.75 E(In particular)5.5 E 2.75(,i)
-.44 G 2.75(ft)-2.75 G(he sender does not act on a Quick-Start)-2.75 E
(Request, then the recei)100.8 371 Q -.165(ve)-.275 G 2.75(rc).165 G
(ould decrement the QS TTL by one in the ne)-2.75 E(xt request recei)
-.165 E -.165(ve)-.275 G(d).165 E
(from that host before calculating the TTL Dif)100.8 384 Q
(f, and decrement the QS TTL by tw)-.275 E 2.75(oi)-.11 G 2.75(nt)-2.75
G(he)-2.75 E(follo)100.8 397 Q(wing recei)-.275 E -.165(ve)-.275 G 2.75
(dr).165 G
(equest, until the sender acts on one of the Quick-Start Requests.)-2.75
E(Unfortunately)100.8 423 Q 2.75(,i)-.715 G 2.75(far)-2.75 G
(outer doesn')-2.75 E 2.75(tu)-.198 G
(nderstand Quick-Start, then it is not possible for that)-2.75 E
(router to tak)100.8 436 Q 2.75(ea)-.11 G 2.75(na)-2.75 G(cti)-2.75 E
.33 -.165(ve s)-.275 H(tep such as zeroing a TTL \214eld to den).165 E
2.75(yar)-.165 G 2.75(equest. As)-2.75 F 2.75(ar)2.75 G(esult, the)-2.75
E(QS TTL is not a f)100.8 449 Q(ail-safe mechanism for pre)-.11 E -.165
(ve)-.275 G(nting lying by recei).165 E -.165(ve)-.275 G
(rs in the case of non-).165 E(Quick-Start-capable routers.)100.8 462 Q
F1 2.75(6.3.2. Recei)72 501 R -.11(ve)-.11 G(rs L).11 E
(ying about the A)-.605 E(ppr)-.275 E -.11(ove)-.198 G 2.75(dR).11 G
(ate)-2.75 E F0 2.75(As)100.8 527 S(econd form of misbeha)-2.75 E
(vior w)-.22 E(ould be for the recei)-.11 E -.165(ve)-.275 G 2.75(rt)
.165 G 2.75(ol)-2.75 G(ie to the sender about the Rate)-2.75 E
(Request for an appro)100.8 540 Q -.165(ve)-.165 G 2.75(dQ).165 G
(uick-Start Request, by increasing the v)-2.75 E
(alue of the Rate Request)-.275 E 2.75(\214eld. Ho)100.8 553 R(we)-.275
E -.165(ve)-.275 G .88 -.44(r, t).165 H(he recei).44 E -.165(ve)-.275 G
2.75(rg).165 G(enerally doesn')-2.75 E 2.75(tk)-.198 G(no)-2.75 E 2.75
(wt)-.275 G(he Rate Request in the original)-2.75 E
(Quick-Start Request sent by the sender)100.8 566 Q 2.75(,a)-.44 G
(nd a higher Rate Request reported by the recei)-2.75 E -.165(ve)-.275 G
(r).165 E(will only be considered v)100.8 579 Q
(alid by the sender if it is no higher than the Rate Request)-.275 E
(originally requested by the sender)100.8 592 Q 5.5(.T)-.605 G
(his limits the ability of the recei)-5.5 E -.165(ve)-.275 G 2.75(rt)
.165 G 2.75(oc)-2.75 G 2.75(heat. F)-2.75 F(or)-.165 E -.165(ex)100.8
605 S(ample, if the sender sends a Quick-Start Request with an Rate Req\
uest of X, and the).165 E(recei)100.8 618 Q -.165(ve)-.275 G 2.75(rr)
.165 G(eports recei)-2.75 E
(ving a Quick-Start Request with an Rate Request of Y > X, then the)
-.275 E(sender kno)100.8 631 Q(ws that either some router along the pat\
h malfunctioned \(increasing the Rate)-.275 E
(Request inappropriately\), or the recei)100.8 644 Q -.165(ve)-.275 G
2.75(ri).165 G 2.75(sl)-2.75 G(ying about the Rate Request in the recei)
-2.75 E -.165(ve)-.275 G(d).165 E(pack)100.8 657 Q(et.)-.11 E(Ho)100.8
683 Q(we)-.275 E -.165(ve)-.275 G .88 -.44(r, i).165 H 2.75(ft).44 G(he\
 sender sends a Quick-Start Request with an Rate Request of Z, the rece\
i)-2.75 E -.165(ve)-.275 G(r).165 E(recei)100.8 696 Q -.165(ve)-.275 G
2.75(st).165 G(he Quick-Start Request with an appro)-2.75 E -.165(ve)
-.165 G 2.75(dR).165 G(ate Request of X, and reports an Rate)-2.75 E
(Request of Y)100.8 709 Q 2.75(,f)-1.419 G
(or X < Y <= Z, then the recei)-2.75 E -.165(ve)-.275 G 2.75(rs).165 G
(ucceeds in lying to the sender about the)-2.75 E(appro)100.8 722 Q
-.165(ve)-.165 G 2.75(dr).165 G(ate.)-2.75 E(Jain/Flo)72 769 Q 195.775
(yd/Allman/Sarolahti Section)-.11 F 2.75(6.3.2. [P)2.75 F(age 27])-.165
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(If senders often use a con\214gured def)100.8 85 Q(ault v)-.11 E
(alue for the Rate Request, then recei)-.275 E -.165(ve)-.275 G(rs w)
.165 E(ould)-.11 E
(often be able to guess the original Rate Request, and this w)100.8 98 Q
(ould mak)-.11 E 2.75(ei)-.11 G 2.75(te)-2.75 G(asier for the)-2.75 E
(recei)100.8 111 Q -.165(ve)-.275 G 2.75(rt).165 G 2.75(ol)-2.75 G
(ie about the v)-2.75 E(alue of the Rate Request \214eld.)-.275 E
(Similarly)5.5 E 2.75(,i)-.715 G 2.75(ft)-2.75 G(he recei)-2.75 E -.165
(ve)-.275 G 2.75(ro).165 G(ften)-2.75 E
(communicates with a particular sender)100.8 124 Q 2.75(,a)-.44 G
(nd the sender al)-2.75 E -.11(wa)-.11 G(ys uses the same Rate Request)
.11 E(for that recei)100.8 137 Q -.165(ve)-.275 G .88 -.44(r, t).165 H
(hen the recei).44 E -.165(ve)-.275 G 2.75(rm).165 G(ight o)-2.75 E
-.165(ve)-.165 G 2.75(rt).165 G(ime be able to infer the original Rate)
-2.75 E(Request used by the sender)100.8 150 Q(.)-.605 E(There are se)
100.8 176 Q -.165(ve)-.275 G(ral possible forms of protection ag).165 E
(ainst recei)-.055 E -.165(ve)-.275 G(rs lying about the v).165 E
(alue of the)-.275 E(Rate Request.)100.8 189 Q(One form of protection w)
5.5 E(ould be the Rate-Reduced Nonce discussed earlier)-.11 E(,)-.44 E
(where the recei)100.8 202 Q -.165(ve)-.275 G 2.75(rw).165 G(ould ha)
-2.86 E .33 -.165(ve t)-.22 H 2.75(or).165 G(eport the original v)-2.75
E(alue of the nonce if the recei)-.275 E -.165(ve)-.275 G(r).165 E
(reported that the original rate request w)100.8 215 Q(as appro)-.11 E
-.165(ve)-.165 G(d.).165 E 2.75(As)100.8 241 S
(econd possible protection w)-2.75 E
(ould be for a router decreasing a Rate Request in a Quick-)-.11 E
(Start Request to report the decrease directly to the sender)100.8 254 Q
5.5(.H)-.605 G -.275(ow)-5.5 G -2.365 -.275(ev e).275 H .88 -.44(r, t)
.275 H(his could lead to).44 E(man)100.8 267 Q 2.75(yr)-.165 G(eports b\
ack to the sender for a single request, and could also be used in addre\
ss-)-2.75 E(spoo\214ng attacks.)100.8 280 Q 2.75(At)100.8 306 S
(hird limited form of protection w)-2.75 E
(ould be for senders to use some de)-.11 E(gree of)-.165 E
(randomization in the requested Rate Request, so that it is dif)100.8
319 Q(\214cult for recei)-.275 E -.165(ve)-.275 G(rs to guess the).165 E
(original v)100.8 332 Q(alue for the Rate Request.)-.275 E(Ho)5.5 E(we)
-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H(his is dif).44 E
(\214cult because there is a f)-.275 E(airly)-.11 E
(coarse granularity in the set of rate requests a)100.8 345 Q -.275(va)
-.22 G(ilable to the sender).275 E 2.75(,a)-.44 G(nd randomizing the)
-2.75 E(initial request only of)100.8 358 Q
(fers limited protection in an)-.275 E 2.75(yc)-.165 G(ase.)-2.75 E/F1
11/Times-Bold@0 SF 2.75(6.3.3. Collusion)72 397 R(between Misbeha)2.75 E
(ving Routers)-.275 E F0(In addition to protecting ag)100.8 423 Q
(ainst misbeha)-.055 E(ving recei)-.22 E -.165(ve)-.275 G
(rs, it is necessary also to protect).165 E(ag)100.8 436 Q
(ainst misbeha)-.055 E(ving routers.)-.22 E
(Consider collusion between an ingress router and an e)5.5 E(gress)-.165
E(router belonging to the same Intranet.)100.8 449 Q
(The ingress router could decrement the Rate)5.5 E
(Request at the ingress, with the e)100.8 462 Q
(gress router increasing it ag)-.165 E(ain at the e)-.055 E 2.75
(gress. The)-.165 F(routers)2.75 E(between the ingress and e)100.8 475 Q
(gress that appro)-.165 E -.165(ve)-.165 G 2.75(dt).165 G
(he decremented rate request might not ha)-2.75 E -.165(ve)-.22 G
(been willing to appro)100.8 488 Q .33 -.165(ve t)-.165 H(he lar).165 E
(ger)-.198 E 2.75(,o)-.44 G(riginal request.)-2.75 E
(Another form of collusion w)100.8 514 Q
(ould be for the ingress router to inform the e)-.11 E
(gress router out-)-.165 E(of-band of the TTL Dif)100.8 527 Q 2.75(ff)
-.275 G(or the request pack)-2.75 E(et at the ingress.)-.11 E(This w)5.5
E(ould enable the e)-.11 E(gress)-.165 E(router to modify the QS TTL so\
 that it appeared that all of the routers along the path had)100.8 540 Q
(appro)100.8 553 Q -.165(ve)-.165 G 2.75(dt).165 G(he request.)-2.75 E
(There does not appear to be an)5.5 E 2.75(yp)-.165 G(rotection ag)-2.75
E(ainst a colluding)-.055 E(ingress and e)100.8 566 Q(gress router)-.165
E 5.5(.E)-.605 G -.165(ve)-5.5 G 2.75(ni).165 G 2.75(fa)-2.75 G 2.75(ni)
-2.75 G(ntermediate router had deleted the Quick-Start)-2.75 E
(Request Option from the pack)100.8 579 Q
(et, the ingress router could ha)-.11 E .33 -.165(ve s)-.22 H
(ent the Quick-Start Request).165 E(Option to the e)100.8 592 Q
(gress router out-of-band, with the e)-.165 E
(gress router inserting the Quick-Start)-.165 E
(Request Option, with a modi\214ed QS TTL \214eld, back in the pack)
100.8 605 Q(et.)-.11 E(Ho)100.8 631 Q(we)-.275 E -.165(ve)-.275 G .88
-.44(r, u).165 H(nlik).44 E 2.75(eE)-.11 G(CN, there is some)-2.75 E
(what less incenti)-.275 E .33 -.165(ve f)-.275 H
(or cooperating ingress and e).165 E(gress)-.165 E
(routers to collude to f)100.8 644 Q
(alsely modify the Quick-Start Request so that it appears to ha)-.11 E
.33 -.165(ve b)-.22 H(een).165 E(appro)100.8 657 Q -.165(ve)-.165 G 2.75
(db).165 G 2.75(ya)-2.75 G(ll of the routers along the path.)-2.75 E
-.44(Wi)5.5 G(th ECN, a colluding ingress router could).44 E -.11(fa)
100.8 670 S(lsely mark a pack).11 E
(et as ECN-capable, with the colluding e)-.11 E
(gress router returning the ECN)-.165 E(\214eld in the IP header to its\
 original non-ECN-capable codepoint, and congested routers)100.8 683 Q
(along the path could ha)100.8 696 Q .33 -.165(ve b)-.22 H
(een fooled into not dropping that pack).165 E 2.75(et. This)-.11 F
(collusion w)2.75 E(ould)-.11 E(gi)100.8 709 Q .33 -.165(ve a)-.275 H
2.75(nu).165 G(nf)-2.75 E(air competiti)-.11 E .33 -.165(ve a)-.275 H
(dv).165 E(antage to the traf)-.275 E
(\214c protected by the colluding ingress and)-.275 E -.165(eg)100.8 722
S(ress routers.).165 E(Jain/Flo)72 769 Q 195.775
(yd/Allman/Sarolahti Section)-.11 F 2.75(6.3.3. [P)2.75 F(age 28])-.165
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(In contrast, with Quick-Start, the collusion of the ingress and e)100.8
85 Q(gress routers to mak)-.165 E 2.75(ei)-.11 G(t)-2.75 E -.11(fa)100.8
98 S(lsely appear that a Quick-Start request w).11 E(as appro)-.11 E
-.165(ve)-.165 G 2.75(dd).165 G(oes not necessarily gi)-2.75 E .33 -.165
(ve a)-.275 H(n).165 E(adv)100.8 111 Q(antage to the traf)-.275 E
(\214c co)-.275 E -.165(ve)-.165 G(red by that collusion.).165 E
(If some router along the path really does)5.5 E(not ha)100.8 124 Q .33
-.165(ve e)-.22 H(nough a).165 E -.275(va)-.22 G
(ilable bandwidth to appro).275 E .33 -.165(ve t)-.165 H
(he Quick-Start request, then the Quick-).165 E(Start pack)100.8 137 Q
(ets sent as a result of the f)-.11 E(alsely-appro)-.11 E -.165(ve)-.165
G 2.75(dr).165 G(equest could be dropped in the)-2.75 E(netw)100.8 150 Q
(ork, to the resulting disadv)-.11 E(antage of the connection.)-.275 E
(Thus, while the ingress and)5.5 E -.165(eg)100.8 163 S
(ress routers could collude to pre).165 E -.165(ve)-.275 G
(nt intermediate routers from den).165 E(ying a Quick-Start)-.165 E
(request, it w)100.8 176 Q(ould not necessarily be to the connection')
-.11 E 2.75(sa)-.605 G(dv)-2.75 E(antage for this to happen.)-.275 E(In)
5.5 E(addition, the router between the ingress and e)100.8 189 Q
(gress nodes that denied the request could be)-.165 E
(monitoring connection performance, acti)100.8 202 Q -.165(ve)-.275 G
(ly penalizing nodes that seem to be using).165 E
(Quick-Start after a Quick-Start request w)100.8 215 Q(as denied.)-.11 E
(If the congested router w)100.8 241 Q
(as ECN-capable, and the colluding ingress and e)-.11 E
(gress routers were)-.165 E(lying about ECN-capability as well as about\
 Quick-Start, then the result could be that the)100.8 254 Q
(Quick-Start request f)100.8 267 Q(alsely appears to the sender to ha)
-.11 E .33 -.165(ve b)-.22 H(een appro).165 E -.165(ve)-.165 G
(d, and the Quick-).165 E(Start pack)100.8 280 Q(ets f)-.11 E
(alsely appear to the congested router to be ECN-capable.)-.11 E
(In this case, the)5.5 E(colluding routers might succeed in gi)100.8 293
Q(ving a competiti)-.275 E .33 -.165(ve a)-.275 H(dv).165 E
(antage to the traf)-.275 E(\214c protected)-.275 E(by their collusion \
\(if no intermediate router is monitoring to catch such misbeha)100.8
306 Q(vior\).)-.22 E/F1 11/Times-Bold@0 SF 2.75(6.3.4. Misbeha)72 345 R
(ving Middleboxes and the IP TTL)-.275 E F0 2.75(As)100.8 371 S
(eparate possibility is that of traf)-2.75 E
(\214c normalizers [HKP01] or other middlebox)-.275 E(es along)-.165 E(\
that path that re-write IP TTLs, in order to foil other kinds of attack\
s in the netw)100.8 384 Q 2.75(ork. If)-.11 F(such a traf)100.8 397 Q
(\214c normalizer re-wrote the IP TTL, b)-.275 E
(ut did not adjust the Quick-Start TTL by)-.22 E
(the same amount, then the sender')100.8 410 Q 2.75(sm)-.605 G
(echanism for determining if the request w)-2.75 E(as appro)-.11 E -.165
(ve)-.165 G(d).165 E(by all routers along the path w)100.8 423 Q
(ould no longer be reliable.)-.11 E(Re-writing the IP TTL could)5.5 E
(result in f)100.8 436 Q(alse positi)-.11 E -.165(ve)-.275 G 2.75(s\()
.165 G(with the sender incorrectly belie)-2.75 E
(ving that the Quick-Start request)-.275 E -.11(wa)100.8 449 S 2.75(sa)
.11 G(ppro)-2.75 E -.165(ve)-.165 G(d\) as well as f).165 E(alse ne)-.11
E -.055(ga)-.165 G(ti).055 E -.165(ve)-.275 G 2.75(s\().165 G
(with the sender incorrectly belie)-2.75 E(ving that the)-.275 E
(Quick-Start request w)100.8 462 Q(as denied\).)-.11 E F1(6.4.)72 501 Q
/F2 13/Times-Bold@0 SF(Quick-Start with QoS-enabled T)5.5 E(raf\214c)
-.962 E F0(The discussion in this document has lar)100.8 527 Q
(gely been of Quick-Start with def)-.198 E(ault, best-ef)-.11 E(fort)
-.275 E(traf)100.8 540 Q 2.75(\214c. Ho)-.275 F(we)-.275 E -.165(ve)
-.275 G .88 -.44(r, Q).165 H(uick-Start could also be used by traf).44 E
(\214c using some form of)-.275 E(dif)100.8 553 Q
(ferentiated services, and routers could tak)-.275 E 2.75(et)-.11 G
(he traf)-2.75 E(\214c class into account when deciding)-.275 E
(whether or not to grant the Quick-Start request.)100.8 566 Q 1.76 -.88
(We d)5.5 H(on').88 E 2.75(ta)-.198 G(ddress this conte)-2.75 E
(xt further in)-.165 E(this paper)100.8 579 Q 2.75(,s)-.44 G
(ince it is orthogonal to the speci\214cation of Quick-Start.)-2.75 E
(Ho)5.5 E(we)-.275 E -.165(ve)-.275 G .88 -.44(r, w).165 H 2.75(en).44 G
(ote that)-2.75 E(routers should be discouraged from granting Quick-Sta\
rt requests for higher)100.8 592 Q(-priority traf)-.22 E<8c63>-.275 E
(when this is lik)100.8 605 Q(ely to result in signi\214cant pack)-.11 E
(et loss for lo)-.11 E(wer)-.275 E(-priority traf)-.22 E(\214c.)-.275 E
F1(6.5.)72 644 Q F2(Limitations of Quick-Start)5.5 E F0
(The Quick-Start proposal, tak)100.8 670 Q
(en together with HighSpeed TCP [F03], could go a)-.11 E
(signi\214cant w)100.8 683 Q(ay to)-.11 E -.11(wa)-.275 G(rds e).11 E
(xtending the range of performance for best-ef)-.165 E(fort traf)-.275 E
(\214c in the)-.275 E 2.75(Internet. Ho)100.8 696 R(we)-.275 E -.165(ve)
-.275 G .88 -.44(r, t).165 H(here are man).44 E 2.75(yt)-.165 G
(hings that the Quick-Start proposal w)-2.75 E(ould not)-.11 E 2.75
(accomplish. Quick-Start)100.8 709 R
(is not a congestion control mechanism, and w)2.75 E(ould not help in)
-.11 E(making more precise use of the a)100.8 722 Q -.275(va)-.22 G
(ilable bandwidth, that is, of achie).275 E(ving the goal of high)-.275
E(Jain/Flo)72 769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75
(6.5. [P)2.75 F(age 29])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(throughput with lo)100.8 85 Q 2.75(wd)-.275 G(elay and lo)-2.75 E 2.75
(wp)-.275 G(ack)-2.75 E(et loss rates.)-.11 E(Quick-Start w)5.5 E
(ould not gi)-.11 E .33 -.165(ve r)-.275 H(outers).165 E(more control o)
100.8 98 Q -.165(ve)-.165 G 2.75(rt).165 G(he decrease rates of acti)
-2.75 E .33 -.165(ve c)-.275 H 2.75(onnections. One).165 F
(of the open questions)2.75 E(addressed later in this document is wheth\
er the limited capabilities of Quick-Start are)100.8 111 Q(suf)100.8 124
Q(\214cient to w)-.275 E(arrant standardization and deplo)-.11 E
(yment, or whether more w)-.11 E(ork is needed \214rst)-.11 E(to e)100.8
137 Q(xplore the space of potential mechanisms.)-.165 E/F1 11
/Times-Bold@0 SF(6.6.)72 176 Q/F2 13/Times-Bold@0 SF
(Attacks on Quick-Start)5.5 E F0
(As discussed in [SAF05], Quick-Start is vulnerable to tw)100.8 202 Q
2.75(ok)-.11 G(inds of Quick-Start attacks:)-2.75 E(\(1\) attacks to in\
crease the routers' processing and state load; and \(2\) attacks with b\
ogus)100.8 215 Q(Quick-Start requests to temporarily tie up a)100.8 228
Q -.275(va)-.22 G(ilable Quick-Start bandwidth, pre).275 E -.165(ve)
-.275 G(nting).165 E(routers from appro)100.8 241 Q
(ving Quick-Start requests from other connections.)-.165 E
(Routers can protect)5.5 E(ag)100.8 254 Q(ainst the \214rst kind of att\
ack by applying a simple limit on the rate at which Quick-Start)-.055 E
(requests will be considered by the router)100.8 267 Q(.)-.605 E
(The second kind of attack, attacks to tie up the a)100.8 293 Q -.275
(va)-.22 G(ilable Quick-Start bandwidth, is more).275 E(dif)100.8 306 Q
(\214cult to defend ag)-.275 E 2.75(ainst. As)-.055 F
(discussed in [SAF05]. Quick-Start Requests that are not)2.75 E
(going to be used, either because the)100.8 319 Q 2.75(ya)-.165 G
(re from malicious attack)-2.75 E(ers or because the)-.11 E 2.75(ya)
-.165 G(re)-2.75 E(denied by routers do)100.8 332 Q
(wnstream, can result in `w)-.275 E
(asting' potential Quick-Start bandwidth,)-.11 E
(resulting in routers den)100.8 345 Q
(ying subsequent Quick-Start Requests that if appro)-.165 E -.165(ve)
-.165 G 2.75(dw).165 G(ould in f)-2.86 E(act)-.11 E(ha)100.8 358 Q .33
-.165(ve b)-.22 H(een used.).165 E 1.76 -.88(We n)5.5 H
(ote that the lik).88 E(elihood of malicious attacks w)-.11 E
(ould be minimized)-.11 E(signi\214cantly when Quick-Start w)100.8 371 Q
(as deplo)-.11 E(yed in a controlled en)-.11 E(vironment such as an)-.44
E(Intranet, where there w)100.8 384 Q
(as some form of centralized control o)-.11 E -.165(ve)-.165 G 2.75(rt)
.165 G(he users in the system.)-2.75 E 1.76 -.88(We a)100.8 397 T
(lso note that this form of attack could potentially mak).88 E 2.75(eQ)
-.11 G(uick-Start unusable, b)-2.75 E(ut it)-.22 E -.11(wo)100.8 410 S
(uld not do an).11 E 2.75(yf)-.165 G(urther damage; in the w)-2.75 E
(orst case, the netw)-.11 E(ork w)-.11 E(ould function as a)-.11 E(netw)
100.8 423 Q(ork without Quick-Start.)-.11 E([SAF05] considers the poten\
tial of Extreme Quick-Start algorithms at routers, which k)100.8 449 Q
(eep)-.11 E(per)100.8 462 Q(-\215o)-.22 E 2.75(ws)-.275 G
(tate for Quick-Start connections, in protecting the a)-2.75 E -.275(va)
-.22 G(ilability of Quick-Start).275 E(bandwidth in the f)100.8 475 Q
(ace of frequent o)-.11 E -.165(ve)-.165 G
(rly-larqe Quick-Start requests.).165 E F1(6.7.)72 514 Q F2
(Simulations with Quick-Start)5.5 E F0(Quick-Start w)100.8 540 Q(as add\
ed to the NS simulator [SH02] by Srikanth Sundarrajan, and additional)
-.11 E(functionality w)100.8 553 Q(as added by P)-.11 E(asi Sarolahti.)
-.165 E(The v)5.5 E(alidation test is at `test-all-quickstart' in)-.275
E(the `tcl/test' directory in NS.)100.8 566 Q
(The initial simulation studies from [SH02] sho)5.5 E 2.75(was)-.275 G
(igni\214cant)-2.75 E(performance impro)100.8 579 Q -.165(ve)-.165 G
(ment using Quick-Start for moderate-sized \215o).165 E
(ws \(between 4KB and)-.275 E(128KB\) in under)100.8 592 Q(-utilized en)
-.22 E 2.75(vironments. These)-.44 F
(studies are of \214le transfers, with the)2.75 E(impro)100.8 605 Q
-.165(ve)-.165 G(ment measured as the relati).165 E .33 -.165(ve i)-.275
H(ncrease in the o).165 E -.165(ve)-.165 G
(rall throughput for the \214le).165 E(transfer)100.8 618 Q 5.5(.T)-.605
G(he study sho)-5.5 E(ws that potential impro)-.275 E -.165(ve)-.165 G
(ment from Quick-Start is proportional to).165 E
(the delay-bandwidth product of the path.)100.8 631 Q
(The Quick-Start simulations in [SAF05] e)100.8 657 Q(xplore the follo)
-.165 E(wing: the potential bene\214t of)-.275 E
(Quick-Start for the connection; the relati)100.8 670 Q .33 -.165(ve b)
-.275 H(ene\214ts of dif).165 E(ferent router)-.275 E
(-based algorithms for)-.22 E(appro)100.8 683 Q
(ving Quick-Start requests; and the ef)-.165 E(fecti)-.275 E -.165(ve)
-.275 G(ness of Quick-Start as a function of the).165 E
(senders' algorithms for choosing the size of the rate request.)100.8
696 Q(Jain/Flo)72 769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75
(6.7. [P)2.75 F(age 30])-.165 E 0 Cg EP
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/Times-Bold@0 SF(7.)72 85 Q/F2 14/Times-Bold@0 SF(Related W)5.5 E(ork)
-1.05 E F0(An)100.8 111 Q 2.75(ye)-.165 G -.275(va)-3.025 G
(luation of Quick-Start must include a discussion of the relati).275 E
.33 -.165(ve b)-.275 H(ene\214ts of).165 E(approaches that use no e)
100.8 124 Q
(xplicit information from routers, and of approaches that use more)-.165
E(\214ne-grained feedback from routers as part of a lar)100.8 137 Q
(ger congestion control mechanism.)-.198 E -.88(We)5.5 G
(discuss three classes of proposals \(no e)100.8 150 Q
(xplicit feedback from routers; e)-.165 E(xplicit feedback)-.165 E(abou\
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the sections belo)100.8 163 Q -.715(w.)-.275 G F1(7.1.)72 202 Q/F3 13
/Times-Bold@0 SF -.325(Fa)5.5 G(st Start-ups without Explicit Inf).325 E
(ormation fr)-.325 E(om Routers)-.234 E F0(One possibility w)100.8 228 Q
(ould be for senders to use information from the pack)-.11 E
(et streams to learn)-.11 E(about the a)100.8 241 Q -.275(va)-.22 G
(ilable bandwidth, without e).275 E(xplicit information from routers.)
-.165 E(These techniques)5.5 E -.11(wo)100.8 254 S(uld not allo).11 E
2.75(was)-.275 G(tart-up as f)-2.75 E(ast as that a)-.11 E -.275(va)-.22
G(ilable from Quick-Start in an underutilized).275 E(en)100.8 267 Q 2.75
(vironment; one)-.44 F(has to ha)2.75 E .33 -.165(ve s)-.22 H
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(et stream to learn)-.11 E(about a)100.8 280 Q -.275(va)-.22 G
(ilable bandwidth.).275 E(Ho)5.5 E(we)-.275 E -.165(ve)-.275 G .88 -.44
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(tart-up considerably)-2.75 E -.11(fa)100.8 293 S
(ster than the current slo).11 E 2.75(w-start. While)-.275 F
(it seems clear that approaches *without* e)2.75 E(xplicit)-.165 E
(feedback from the routers will be strictly less po)100.8 306 Q
(werful that is possible *with* e)-.275 E(xplicit)-.165 E
(feedback, it is also possible that approaches that are more aggressi)
100.8 319 Q .33 -.165(ve t)-.275 H(han slo).165 E(w-start are)-.275 E
(possible without e)100.8 332 Q(xplicit feedback from routers.)-.165 E
(Periodic pack)100.8 358 Q(et streams:)-.11 E([JD02] e)100.8 371 Q
(xplores the use of periodic pack)-.165 E(et streams to estimate the a)
-.11 E -.275(va)-.22 G(ilable bandwidth).275 E(along a path.)100.8 384 Q
(The idea is that the one-w)5.5 E(ay delays of a periodic pack)-.11 E
(et stream sho)-.11 E 2.75(wa)-.275 G(n)-2.75 E
(increasing trend when the stream')100.8 397 Q 2.75(sr)-.605 G
(ate is higher than the a)-2.75 E -.275(va)-.22 G(ilable bandwidth.).275
E(While)5.5 E([JD02] states that the proposed mechanism does not cause \
signi\214cant increases in netw)100.8 410 Q(ork)-.11 E
(utilization, losses, or delays when done by one \215o)100.8 423 Q 2.75
(wa)-.275 G 2.75(tat)-2.75 G(ime, the approach could be)-2.75 E
(problematic if conducted concurrently by a number of \215o)100.8 436 Q
2.75(ws. [JD02])-.275 F(also gi)2.75 E -.165(ve)-.275 G 2.75(sa).165 G
(n)-2.75 E -.165(ove)100.8 449 S(rvie).165 E 2.75(wo)-.275 G 2.75(fs)
-2.75 G(ome of the earlier w)-2.75 E(ork on inferring the a)-.11 E -.275
(va)-.22 G(ilable bandwidth from pack).275 E(et)-.11 E(trains.)100.8 462
Q(Swift-Start:)100.8 488 Q
(The Swift Start proposal from [PRAKS02] combines pack)100.8 501 Q
(et-pair and pack)-.11 E(et-pacing)-.11 E 2.75(techniques. An)100.8 514
R(initial congestion windo)2.75 E 2.75(wo)-.275 G 2.75(ff)-2.75 G
(our se)-2.75 E(gments is used to estimate the)-.165 E -.22(av)100.8 527
S(ailable bandwidth along the path.)-.055 E
(This estimate is then used to dramatically increase the)5.5 E
(congestion windo)100.8 540 Q 2.75(wd)-.275 G(uring the second R)-2.75 E
(TT of data transmission.)-.66 E(While continued research on the limits\
 of the ability of TCP and other transport protocols)100.8 566 Q
(to learn of a)100.8 579 Q -.275(va)-.22 G(ilable bandwidth without e)
.275 E(xplicit feedback from the router seems useful, we)-.165 E
(note that there are se)100.8 592 Q -.165(ve)-.275 G
(ral fundamental adv).165 E(antages of e)-.275 E
(xplicit feedback from routers.)-.165 E(\(1\) Explicit feedback is f)
100.8 618 Q(aster than implicit feedback:)-.11 E(One adv)100.8 631 Q
(antage of e)-.275 E(xplicit feedback from the routers is that it allo)
-.165 E(ws the transport sender to)-.275 E(reliably learn of a)100.8 644
Q -.275(va)-.22 G(ilable bandwidth in one round-trip time.).275 E
(\(2\) Explicit feedback is more reliable than implicit feedback:)100.8
670 Q 2.75(As)100.8 683 S(econd adv)-2.75 E(antage of e)-.275 E
(xplicit feedback from the routers is that the a)-.165 E -.275(va)-.22 G
(ilable bandwidth).275 E
(along the path does not necessarily map to the allo)100.8 696 Q
(wed sending rate for an indi)-.275 E(vidual \215o)-.275 E -.715(w.)
-.275 G(As an e)100.8 709 Q(xample, if the TCP sender sends four pack)
-.165 E(ets back-to-back in the initial windo)-.11 E -.715(w,)-.275 G
(and the TCP recei)100.8 722 Q -.165(ve)-.275 G 2.75(rr).165 G
(eports that the data pack)-2.75 E(ets were recei)-.11 E -.165(ve)-.275
G 2.75(dw).165 G(ith roughly the same)-2.75 E(Jain/Flo)72 769 Q 204.025
(yd/Allman/Sarolahti Section)-.11 F 2.75(7.1. [P)2.75 F(age 31])-.165 E
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(spacing as the)100.8 85 Q 2.75(yw)-.165 G
(ere transmitted, does this mean that the \215o)-2.75 E 2.75(wc)-.275 G
(an infer an underutilized)-2.75 E 2.75(path? And)100.8 98 R(ho)2.75 E
2.75(wf)-.275 G(ast can the \215o)-2.86 E 2.75(ws)-.275 G(end in the ne)
-2.75 E(xt round-trip time?)-.165 E(Do the results depend)5.5 E
(on the le)100.8 111 Q -.165(ve)-.275 G 2.75(lo).165 G 2.75(fs)-2.75 G
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E(attempting a f)100.8 124 Q(aster start-up at the same time?)-.11 E/F1
11/Times-Bold@0 SF(7.2.)72 163 Q/F2 13/Times-Bold@0 SF
(Optimistic Sending without Explicit Inf)5.5 E(ormation fr)-.325 E
(om Routers)-.234 E F0(Another possibility that has been suggested [S02\
] is for the sender to start with a lar)100.8 189 Q(ge)-.198 E
(initial windo)100.8 202 Q 2.75(ww)-.275 G(ithout e)-2.75 E
(xplicit permission from the routers and without bandwidth)-.165 E
(estimation techniques, and for the \214rst pack)100.8 215 Q
(et of the initial windo)-.11 E 2.75(wt)-.275 G 2.75(oc)-2.75 G
(ontain information)-2.75 E
(such as the size or sending rate of the initial windo)100.8 228 Q 4.18
-.715(w. T)-.275 H(he proposal w).715 E(ould be that)-.11 E
(congested routers w)100.8 241 Q
(ould use this information in the \214rst data pack)-.11 E
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(ptimistically-lar)-2.75 E(ge)-.198 E(initial windo)100.8 267 Q 2.75(ww)
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(ets from competing \215o)-.11 E(ws in the)-.275 E(netw)100.8 280 Q 2.75
(ork. Such)-.11 F(an approach w)2.75 E
(ould seem to require some mechanism for the sender to)-.11 E(ensure th\
at the routers along the path understood the mechanism for marking the \
\214rst)100.8 293 Q(pack)100.8 306 Q(et of a lar)-.11 E
(ge initial windo)-.198 E -.715(w.)-.275 G(Ob)100.8 332 Q
(viously there w)-.165 E
(ould be a number of questions to consider about an approach of)-.11 E
(optimistic sending.)100.8 345 Q(\(1\) Incremental deplo)100.8 371 Q
(yment:)-.11 E(One question w)100.8 384 Q
(ould be the potential complications of incremental deplo)-.11 E
(yment, where some)-.11 E
(of the routers along the path might not understand the pack)100.8 397 Q
(et information describing the)-.11 E(initial windo)100.8 410 Q -.715
(w.)-.275 G(\(2\) Congestion collapse:)100.8 436 Q
(There could also be concerns about congestion collapse if man)100.8 449
Q 2.75<798d>-.165 G -.275(ow)-2.75 G 2.75(su).275 G(sed lar)-2.75 E
(ge initial)-.198 E(windo)100.8 462 Q(ws, man)-.275 E 2.75(yp)-.165 G
(ack)-2.75 E(ets were dropped from optimistic initial windo)-.11 E
(ws, and man)-.275 E(y)-.165 E(congested links ended up carrying pack)
100.8 475 Q(ets that are only going to be dropped do)-.11 E(wnstream.)
-.275 E(\(3\) Distrib)100.8 501 Q(uted Denial of Service attacks:)-.22 E
2.75(At)100.8 514 S(hird k)-2.75 E .33 -.165(ey q)-.11 H(uestion w).165
E(ould be the potential role of optimistic senders in amplifying the)
-.11 E(damage done by a Distrib)100.8 527 Q
(uted Denial of Service \(DDoS\) attack.)-.22 E
(\(4\) Performance hits if a pack)100.8 553 Q(et is dropped:)-.11 E 2.75
(Af)100.8 566 S(ourth issue w)-2.75 E
(ould be to quantify the performance hit to the connection when a pack)
-.11 E(et is)-.11 E(dropped from one of the initial windo)100.8 579 Q
(ws.)-.275 E F1(7.3.)72 618 Q F2 -.325(Fa)5.5 G
(st Start-ups with other Inf).325 E(ormation fr)-.325 E(om Routers)-.234
E F0(There ha)100.8 644 Q .33 -.165(ve b)-.22 H(een se).165 E -.165(ve)
-.275 G(ral proposals some).165 E
(what similar to Quick-Start, where the transport)-.275 E
(protocol collects e)100.8 657 Q
(xplicit information from the routers along the path.)-.165 E
(An IP Option about the free b)100.8 683 Q(uf)-.22 E(fer size:)-.275 E
(In related w)100.8 696 Q(ork, [P00] in)-.11 E -.165(ve)-.44 G(stig).165
E(ates the use of a slightly dif)-.055 E(ferent IP option for TCP)-.275
E(connections to disco)100.8 709 Q -.165(ve)-.165 G 2.75(rt).165 G(he a)
-2.75 E -.275(va)-.22 G(ilable bandwidth along the path.).275 E
(In that proposal, the IP)5.5 E(option w)100.8 722 Q
(ould query the routers along the path about the smallest a)-.11 E -.275
(va)-.22 G(ilable free b).275 E(uf)-.22 E(fer size.)-.275 E(Jain/Flo)72
769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75(7.3. [P)2.75 F
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
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(sender already had an estimate of the round-trip time.)100.8 98 Q
(The Performance T)100.8 124 Q(ransparenc)-.385 E 2.75(yP)-.165 G
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-2.75 E(et)-.11 E(that w)100.8 150 Q(ould collect information from rout\
ers along the path from the sender to the recei)-.11 E -.165(ve)-.275 G
(r).165 E 2.75([W00]. F)100.8 163 R(or e)-.165 E
(xample, a single PTP pack)-.165 E
(et could be used to determine the bottleneck)-.11 E
(bandwidth along a path.)100.8 176 Q(ETEN:)100.8 202 Q
(Additional proposals for end nodes to collect e)100.8 215 Q
(xplicit information from routers include)-.165 E(Explicit T)100.8 228 Q
(ransport Error Noti\214cation \(ETEN\), which includes a cumulati)-.385
E .33 -.165(ve m)-.275 H(echanism to).165 E(notify endpoints of aggre)
100.8 241 Q -.055(ga)-.165 G
(te congestion statistics along the path [KAPS02].).055 E/F1 11
/Times-Bold@0 SF(7.4.)72 280 Q/F2 13/Times-Bold@0 SF -.325(Fa)5.5 G
(st Start-ups with mor).325 E 3.25(eF)-.234 G(ine-Grained F)-3.25 E
(eedback fr)-.325 E(om Routers)-.234 E F0(Proposals for more \214ne-gra\
ined congestion-related feedback from routers include XCP)100.8 306 Q
([KHR02], MaxNet [MaxNet], and AntiECN marking [K03].)100.8 319 Q
(Section A.6 discusses in)5.5 E(more detail the relationship between Qu\
ick-Start and proposals for more \214ne-grained per)100.8 332 Q(-)-.22 E
(pack)100.8 345 Q(et feedback from routers.)-.11 E(XCP:)100.8 371 Q
(Proposals such as XCP for ne)100.8 384 Q 2.75(wc)-.275 G
(ongestion control mechanisms based on more feedback)-2.75 E
(from routers are more po)100.8 397 Q(werful than Quick-Start, b)-.275 E
(ut also are more comple)-.22 E 2.75(xt)-.165 G 2.75(ou)-2.75 G
(nderstand)-2.75 E(and more dif)100.8 410 Q(\214cult to deplo)-.275 E
4.18 -.715(y. X)-.11 H(CP routers maintain no per).715 E(-\215o)-.22 E
2.75(ws)-.275 G(tate, b)-2.75 E(ut pro)-.22 E(vide more)-.165 E(\214ne-\
grained feedback to end-nodes than the one-bit congestion feedback of E\
CN.)100.8 423 Q(The per)5.5 E(-)-.22 E(pack)100.8 436 Q
(et feedback from XCP can be positi)-.11 E .33 -.165(ve o)-.275 H 2.75
(rn).165 G -2.475 -.165(eg a)-2.75 H(ti).165 E -.165(ve)-.275 G 2.75(,a)
.165 G(nd speci\214es the increase or)-2.75 E(decrease in the sender')
100.8 449 Q 2.75(sc)-.605 G(ongestion windo)-2.75 E 2.75(ww)-.275 G
(hen this pack)-2.75 E(et is ackno)-.11 E(wledged.)-.275 E(AntiECN:)
100.8 475 Q(The AntiECN proposal is for a single bit in the pack)100.8
488 Q(et header that routers could set to)-.11 E(indicate that the)100.8
501 Q 2.75(ya)-.165 G(re underutilized.)-2.75 E -.165(Fo)5.5 G 2.75(re)
.165 G(ach TCP A)-2.75 E(CK arri)-.44 E(ving at the sender indicating)
-.275 E(that a pack)100.8 514 Q(et has been recei)-.11 E -.165(ve)-.275
G 2.75(dw).165 G(ith the Anti-ECN bit set, the sender w)-2.75 E
(ould be able to)-.11 E(increase its congestion windo)100.8 527 Q 2.75
(wb)-.275 G 2.75(yo)-2.75 G(ne pack)-2.75 E(et, as it w)-.11 E
(ould during slo)-.11 E(w-start.)-.275 E F1(8.)72 566 Q/F3 14
/Times-Bold@0 SF(Implementation and Deployment Issues)5.5 E F0(This sec\
tion discusses some of the implementation issues with Quick-Start.)100.8
592 Q(This section)8.25 E(also discusses some of the k)100.8 605 Q .33
-.165(ey d)-.11 H(eplo).165 E(yment issues, such as the chick)-.11 E
(en-and-e)-.11 E(gg deplo)-.165 E(yment)-.11 E
(problems of mechanisms that ha)100.8 618 Q .33 -.165(ve t)-.22 H 2.75
(ob).165 G 2.75(ed)-2.75 G(eplo)-2.75 E
(yed in both routers and end nodes in order to)-.11 E -.11(wo)100.8 631
S(rk, and the problems posed by the wide deplo).11 E(yment of middlebox)
-.11 E(es today that block the)-.165 E(use of kno)100.8 644 Q
(wn or unkno)-.275 E(wn IP Options.)-.275 E F1(8.1.)72 683 Q F2
(Implementation Issues f)5.5 E(or Sending Quick-Start Requests)-.325 E
F0(Section 4.6 discusses some of the issues with deciding the initial s\
ending rate to request.)100.8 709 Q(Quick-Start raises additional issue\
s about the communication between the transport)100.8 722 Q(Jain/Flo)72
769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75(8.1. [P)2.75 F
(age 33])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(protoco\
l and the application, and about the use of the past history with Quick\
-Start in the)100.8 85 Q(end node.)100.8 98 Q
(One possibility is that a protocol implementation could pro)100.8 124 Q
(vide an API for applications to)-.165 E(indicate when the)100.8 137 Q
2.75(yw)-.165 G(ant to request Quick-Start, and what rate the)-2.86 E
2.75(yw)-.165 G(ould lik)-2.86 E 2.75(et)-.11 G 2.75(or)-2.75 G(equest.)
-2.75 E(In the con)100.8 150 Q -.165(ve)-.44 G(ntional sock).165 E
(et API this could be a sock)-.11 E
(et option that is set before a connection)-.11 E(is established.)100.8
163 Q(Some applications, such those that use TCP for b)5.5 E
(ulk transfers, do not ha)-.22 E -.165(ve)-.22 G
(interest in the transmission rate, b)100.8 176 Q(ut the)-.22 E 2.75(ym)
-.165 G(ight kno)-2.75 E 2.75(wt)-.275 G
(he amount of data that can be sent)-2.75 E(immediately)100.8 189 Q 2.75
(.B)-.715 G(ased on this, the sender implementation could decide whethe\
r Quick-Start)-2.75 E -.11(wo)100.8 202 S
(uld be useful, and what rate should be requested.).11 E
(Datagram-based real-time streaming)5.5 E
(applications, on the other hand, may ha)100.8 215 Q .33 -.165(ve a s)
-.22 H(peci\214c preference on the transmission rate and).165 E(the)
100.8 228 Q 2.75(yc)-.165 G(ould indicate the required rate e)-2.75 E
(xplicitly to the transport protocol to be used in the)-.165 E
(Quick-Start Request.)100.8 241 Q 1.76 -.88(We n)100.8 267 T(ote that w\
hen Quick-Start is used, the TCP sender is required to implement an).88
E(additional timer for the paced transmission of Quick-Start pack)100.8
280 Q(ets.)-.11 E/F1 11/Times-Bold@0 SF(8.2.)72 319 Q/F2 13/Times-Bold@0
SF(Implementation Issues f)5.5 E(or Pr)-.325 E
(ocessing Quick-Start Requests)-.234 E F0 2.75(Ar)100.8 345 S
(outer or other netw)-2.75 E
(ork host must be able to determine the approximate bandwidth of its)
-.11 E(outbound netw)100.8 358 Q(ork interf)-.11 E
(aces in order to process incoming Quick-Start rate requests,)-.11 E
(including those that originate from the host itself.)100.8 371 Q
(One possibility w)5.5 E(ould be for hosts to)-.11 E(rely on con\214gur\
ation information to determine link bandwidths; this has the dra)100.8
384 Q(wback of)-.165 E(not being rob)100.8 397 Q
(ust to errors in con\214guration.)-.22 E(Another possibility w)5.5 E
(ould be for netw)-.11 E(ork)-.11 E(de)100.8 410 Q(vice dri)-.275 E
-.165(ve)-.275 G(rs to infer the bandwidth for the interf).165 E
(ace and to communicate this to the IP)-.11 E(layer)100.8 423 Q(.)-.605
E -.165(Pa)100.8 449 S
(rticular issues will arise for wireless links with v).165 E
(ariable bandwidth, where decisions will)-.275 E(ha)100.8 462 Q .33
-.165(ve t)-.22 H 2.75(ob).165 G 2.75(em)-2.75 G(ade about ho)-2.75 E
2.75(wf)-.275 G(requently the netw)-2.75 E
(ork host gets updates of the changing)-.11 E 2.75(bandwidth. It)100.8
475 R(seems appropriate that Quick-Start Requests w)2.75 E
(ould be handled particularly)-.11 E(conserv)100.8 488 Q(ati)-.275 E
-.165(ve)-.275 G(ly for links with v).165 E(ariable bandwidth, to a)
-.275 E -.22(vo)-.22 G(id cases where Quick-Start).22 E
(Requests are appro)100.8 501 Q -.165(ve)-.165 G
(d, the link bandwidth is reduced, and the data pack).165 E
(ets that are send)-.11 E(end up being dropped.)100.8 514 Q F1(8.3.)72
553 Q F2 -.26(Po)5.5 G(ssible Deployment Scenarios).26 E F0
(Because of possible problems discussed abo)100.8 579 Q .33 -.165(ve c)
-.165 H(oncerning using Quick-Start o).165 E -.165(ve)-.165 G 2.75(rs)
.165 G(ome)-2.75 E(netw)100.8 592 Q
(ork paths, the most realistic initial deplo)-.11 E
(yment of Quick-Start w)-.11 E(ould lik)-.11 E(ely to tak)-.11 E(e)-.11
E(place in Intranets and other controlled en)100.8 605 Q 2.75
(vironments. Quick-Start)-.44 F(is most useful on high)2.75 E(bandwidth\
-delay paths that are signi\214cantly underutilized. The primary initia\
l users of)100.8 618 Q(Quick-Start w)100.8 631 Q(ould lik)-.11 E
(ely be in or)-.11 E -.055(ga)-.198 G(nizations that pro).055 E
(vide netw)-.165 E(ork services to their users)-.11 E(and also ha)100.8
644 Q .33 -.165(ve c)-.22 H(ontrol o).165 E -.165(ve)-.165 G 2.75(ral)
.165 G(ar)-2.75 E(ge portion of the netw)-.198 E(ork path.)-.11 E(Belo)
100.8 670 Q 2.75(wa)-.275 G(re a fe)-2.75 E 2.75(we)-.275 G
(xamples of netw)-2.915 E(orking en)-.11 E
(vironments where Quick-Start w)-.44 E(ould)-.11 E
(potentially be useful.)100.8 683 Q(These are the en)5.5 E
(vironments that might consider an initial deplo)-.44 E(yment)-.11 E
(of Quick-Start in the routers and end-nodes, where the incenti)100.8
696 Q -.165(ve)-.275 G 2.75(sf).165 G(or routers to deplo)-2.75 E(y)-.11
E(Quick-Start might be the most clear)100.8 709 Q(.)-.605 E(Jain/Flo)72
769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75(8.3. [P)2.75 F
(age 34])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E 2.75(*C)
100.8 85 S(entrally-administrated or)-2.75 E -.055(ga)-.198 G
(nizational Intranets often ha).055 E .33 -.165(ve l)-.22 H(ar).165 E
(ge netw)-.198 E(ork capacity and)-.11 E(the netw)100.8 98 Q
(orks are underutilized for most of the time.)-.11 E
(Such Intranets might also include)5.5 E
(high-bandwidth and high-delay paths to remote sites.)100.8 111 Q
(In such an en)5.5 E(vironment, Quick-Start)-.44 E -.11(wo)100.8 124 S
(uld be of bene\214t to users, and there w).11 E
(ould be a clear incenti)-.11 E .33 -.165(ve f)-.275 H(or the deplo).165
E(yment of)-.11 E(Quick-Start in routers.)100.8 137 Q -.165(Fo)5.5 G
2.75(re).165 G
(xample, Quick-Start could be quite useful in high-bandwidth)-2.915 E
(netw)100.8 150 Q(orks used for scienti\214c computing.)-.11 E 2.75(*Q)
100.8 176 S(uick-Start could also be useful in high-delay en)-2.75 E
(vironments of Cellular W)-.44 E(ide-Area)-.44 E -.44(Wi)100.8 189 S
(reless Netw).44 E
(orks such as the GPRS [BW97] and their enhancements and ne)-.11 E(xt)
-.165 E(generations. F)100.8 202 Q(or e)-.165 E
(xample, GPRS EDGE \(Enhanced Data for GSM Ev)-.165 E(olution\) is e)
-.22 E(xpected)-.165 E(to pro)100.8 215 Q
(vide wireless bandwidth of up to 384 Kbps \(roughly 32 1500-byte pack)
-.165 E(ets per)-.11 E(second\) while the GPRS round-trip times are typ\
ically up to one second e)100.8 228 Q(xcluding an)-.165 E(y)-.165 E
(possible queueing delays in the netw)100.8 241 Q(ork [GP)-.11 E
(AR02]. In addition, these netw)-1.012 E(orks sometimes)-.11 E(ha)100.8
254 Q .33 -.165(ve v)-.22 H
(ariable additional delays due to resource allocation that could be a)
-.11 E -.22(vo)-.22 G(ided by k).22 E(eeping)-.11 E
(the connection path constantly utilized, starting from initial slo)
100.8 267 Q 2.75(w-start. Thus,)-.275 F(Quick-Start)2.75 E
(could be of signi\214cant bene\214t to users in these en)100.8 280 Q
(vironments.)-.44 E 2.75(*G)100.8 306 S
(eostationary Orbit \(GEO\) satellite links ha)-2.75 E .33 -.165(ve o)
-.22 H(ne-w).165 E(ay propag)-.11 E(ation delays on the order)-.055 E
(of 250 ms while the bandwidth can be measured in me)100.8 319 Q -.055
(ga)-.165 G(bits per second [RFC2488].).055 E
(Because of the considerable bandwidth-delay product on the link, TCP')
100.8 332 Q 2.75(ss)-.605 G(lo)-2.75 E(w-start is a)-.275 E
(major performance limitation in the be)100.8 345 Q
(ginning of the connection.)-.165 E 2.75(Al)5.5 G(ar)-2.75 E
(ge initial congestion)-.198 E(windo)100.8 358 Q 2.75(ww)-.275 G
(ould be useful to users of such satellite links.)-2.86 E/F1 11
/Times-Bold@0 SF(8.4.)72 397 Q/F2 13/Times-Bold@0 SF -.975(Wo)5.5 G
(uld QuickStart pack).975 E(ets tak)-.13 E 3.25(et)-.13 G(he slo)-3.25 E
3.25(wp)-.13 G(ath in r)-3.25 E(outers?)-.234 E F0(Ho)100.8 423 Q 2.75
(wm)-.275 G(uch delay w)-2.75 E(ould the slo)-.11 E 2.75(wp)-.275 G
(ath add to the processing time for this pack)-2.75 E(et?)-.11 E
(Similarly)100.8 436 Q 2.75(,i)-.715 G 2.75(fQ)-2.75 G(uickStart pack)
-2.75 E(ets took the slo)-.11 E 2.75(wp)-.275 G(ath, ho)-2.75 E 2.75(wm)
-.275 G(uch stress w)-2.75 E(ould it add to routers)-.11 E
(for there to be man)100.8 449 Q 2.75(ym)-.165 G(ore pack)-2.75 E
(ets on the slo)-.11 E 2.75(wp)-.275 G
(ath, because of the number of pack)-2.75 E(ets)-.11 E
(using QuickStart?)100.8 462 Q(These are both questions to be e)5.5 E
(xplored while e)-.165 E(xperimenting with)-.165 E
(Quick-Start in the Internet.)100.8 475 Q F1(8.5.)72 514 Q F2 3.25(AC)
5.5 G(omparison with the Deployment Pr)-3.25 E(oblems of ECN)-.234 E F0
(Gi)100.8 540 Q -.165(ve)-.275 G 2.75(nt).165 G(he glacially slo)-2.75 E
2.75(wr)-.275 G(ate of deplo)-2.75 E
(yment of ECN in the Internet to date [MAF05], it is)-.11 E
(disconcerting to note that some of the deplo)100.8 553 Q
(yment problems of Quick-Start are e)-.11 E -.165(ve)-.275 G 2.75(ng)
.165 G(reater)-2.75 E(than those of ECN.)100.8 566 Q(First, unlik)5.5 E
2.75(eE)-.11 G(CN, which can be of bene\214t e)-2.75 E -.165(ve)-.275 G
2.75(ni).165 G 2.75(fi)-2.75 G 2.75(ti)-2.75 G 2.75(so)-2.75 G
(nly deplo)-2.75 E(yed)-.11 E
(on one of the routers along the end-to-end path, a connection')100.8
579 Q 2.75(su)-.605 G(se of Quick-Start requires)-2.75 E(its deplo)100.8
592 Q(yment on all of the routers along the end-to-end path.)-.11 E
(Second, unlik)5.5 E 2.75(eE)-.11 G(CN, which)-2.75 E
(uses an allocated \214eld in the IP header)100.8 605 Q 2.75(,Q)-.44 G
(uick-Start requires the e)-2.75 E(xtra complications of an)-.165 E
(IP Option.)100.8 618 Q(Ho)100.8 644 Q(we)-.275 E -.165(ve)-.275 G .88
-.44(r, i).165 H 2.75(ns).44 G
(pite of these issues, there is some hope for the deplo)-2.75 E
(yment of Quick-Start, at)-.11 E(least in protected corners of the Inte\
rnet, because the potential bene\214ts of Quick-Start to)100.8 657 Q
(the user are considerably more dramatic than those of ECN.)100.8 670 Q
(Rather than simply replacing)5.5 E(the occasional dropped pack)100.8
683 Q(et by an ECN-mark)-.11 E(ed pack)-.11 E
(et, Quick-Start is capable of)-.11 E(dramatically increasing the throu\
ghput of connections in underutilized en)100.8 696 Q(vironments.)-.44 E
(Jain/Flo)72 769 Q 204.025(yd/Allman/Sarolahti Section)-.11 F 2.75
(8.5. [P)2.75 F(age 35])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Times-Bold@0 SF(9.)72 85 Q/F2 14/Times-Bold@0 SF
(Security Considerations)5.5 E F0(Sections 6.3 and 6.6 discuss the secu\
rity considerations related to Quick-Start.)100.8 111 Q(Section 6.3)5.5
E(discusses the potential ab)100.8 124 Q(use of Quick-Start of recei)
-.22 E -.165(ve)-.275 G(rs lying about whether the request).165 E -.11
(wa)100.8 137 S 2.75(sa).11 G(ppro)-2.75 E -.165(ve)-.165 G 2.75(do).165
G 2.75(ra)-2.75 G(bout the appro)-2.75 E -.165(ve)-.165 G 2.75(dr).165 G
(ate; of routers in collusion to misuse Quick-Start; and)-2.75 E
(of potential problems with traf)100.8 150 Q(\214c normalizers that re)
-.275 E(write IP TTLs in pack)-.275 E(et headers.)-.11 E(All)5.5 E(of t\
hese problems could result in the sender using an Rate Request that w)
100.8 163 Q(as inappropriately)-.11 E(lar)100.8 176 Q
(ge, or thinking that a request w)-.198 E(as appro)-.11 E -.165(ve)-.165
G 2.75(dw).165 G(hen it w)-2.75 E(as in f)-.11 E
(act denied by at least one)-.11 E(router along the path.)100.8 189 Q
(This inappropriate use of Quick-Start w)5.5 E
(ould result in congestion and)-.11 E(an unacceptable le)100.8 202 Q
-.165(ve)-.275 G 2.75(lo).165 G 2.75(fp)-2.75 G(ack)-2.75 E
(et drops along the path, Such congestion could also be part of)-.11 E
2.75(aD)100.8 215 S(enial of Service attack.)-2.75 E(Section 6.6 discus\
ses a potential attack on the routers' processing and state load from a\
n)100.8 241 Q(attack of Quick-Start Requests.)100.8 254 Q
(Section 6.6 also discusses a potential attack on the)5.5 E -.22(av)
100.8 267 S(ailable Quick-Start bandwidth by sending bogus Quick-Start \
requests for bandwidth that)-.055 E(will not in f)100.8 280 Q
(act be used.)-.11 E
(Section 4.6.3 discusses the potential problem of pack)100.8 306 Q
(ets with Quick-Start Requests)-.11 E(dropped by middlebox)100.8 319 Q
(es along the path.)-.165 E F1(10.)72 358 Q F2(Conclusions)5.5 E F0 1.76
-.88(We a)100.8 384 T(re presenting the Quick-Start mechanism as a prop\
osal for a simple, understandable,).88 E(and incrementally-deplo)100.8
397 Q(yable mechanism that w)-.11 E(ould be suf)-.11 E
(\214cient to allo)-.275 E 2.75(wc)-.275 G(onnections to)-2.75 E
(start up with lar)100.8 410 Q(ge initial rates, or lar)-.198 E
(ge initial congestion windo)-.198 E(ws, in o)-.275 E -.165(ve)-.165 G
(rpro).165 E(visioned,)-.165 E(high-bandwidth en)100.8 423 Q 2.75
(vironments. W)-.44 F 2.75(ee)-.88 G
(xpect there will be an increasing number of)-2.915 E -.165(ove)100.8
436 S(rpro).165 E(visioned, high-bandwidth en)-.165 E
(vironments where the Quick-Start mechanism, or)-.44 E
(another mechanism of similar po)100.8 449 Q(wer)-.275 E 2.75(,c)-.44 G
(ould be of signi\214cant bene\214t to a wide range of)-2.75 E(traf)
100.8 462 Q 2.75(\214c. W)-.275 F 2.75(ea)-.88 G(re presenting the Quic\
k-Start mechanism as a request for the community to)-2.75 E(pro)100.8
475 Q(vide feedback and e)-.165 E
(xperimentation on issues relating to Quick-Start.)-.165 E F1(11.)72 514
Q F2(Ackno)5.5 E(wledgements)-.14 E F0
(The authors wish to thank Mark Handle)100.8 540 Q 2.75(yf)-.165 G
(or discussions of these issues.)-2.75 E(The authors also)5.5 E
(thank the End-to-End Research Group, the T)100.8 553 Q
(ransport Services W)-.385 E(orking Group, and)-.88 E(members of IP)
100.8 566 Q(AM')-1.012 E 2.75(sp)-.605 G(rogram on Lar)-2.75 E
(ge Scale Communication Netw)-.198 E(orks for both positi)-.11 E -.165
(ve)-.275 G(and ne)100.8 579 Q -.055(ga)-.165 G(ti).055 E .33 -.165
(ve f)-.275 H(eedback on this proposal.).165 E 1.76 -.88(We t)5.5 H
(hank Srikanth Sundarrajan for the initial).88 E
(implementation of Quick-Start in the NS simulator)100.8 592 Q 2.75(,a)
-.44 G(nd for the initial simulation study)-2.75 E 5.5(.W)-.715 G(e)
-6.38 E(also thank Mohammed Ashraf, John Border)100.8 605 Q 2.75(,T)-.44
G(om Dunig)-3.63 E(an, John Heidemann, P)-.055 E(aul Hyder)-.165 E(,)
-.44 E(Dina Katabi, and V)100.8 618 Q(ern P)-1.221 E
(axson for feedback.)-.165 E(This draft b)5.5 E
(uilds upon the concepts described)-.22 E
(in [RFC3390], [AHO98], [RFC2415], and [RFC3168].)100.8 631 Q(This is a\
 modi\214cation of a draft originally by Amit Jain for Initial W)100.8
657 Q(indo)-.44 E 2.75(wD)-.275 G(isco)-2.75 E -.165(ve)-.165 G(ry).165
E(.)-.715 E F1(A.)72 696 Q F2(Design Decisions)5.5 E F0(Jain/Flo)72 769
Q 209.833(yd/Allman/Sarolahti Section)-.11 F 2.75(A. [P)2.75 F(age 36])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Times-Bold@0 SF(A.1.)72 85 Q/F2 13/Times-Bold@0 SF(Alter)5.5 E
(nate Mechanisms f)-.195 E(or the Quick-Start Request: ICMP and RSVP)
-.325 E F0(This document has proposed using an IP Option for the Quick-\
Start Request from the)100.8 111 Q(sender to the recei)100.8 124 Q -.165
(ve)-.275 G .88 -.44(r, a).165 H
(nd using transport mechanisms for the Quick-Start Response from).44 E
(the recei)100.8 137 Q -.165(ve)-.275 G 2.75(rb).165 G
(ack to the sender)-2.75 E 5.5(.I)-.605 G 2.75(nt)-5.5 G
(his section we discuss alternate mechanisms, and)-2.75 E(consider whet\
her ICMP [RFC792, RFC2463] or RSVP [RFC2205] protocols could be used)
100.8 150 Q(for deli)100.8 163 Q -.165(ve)-.275 G
(ring the Quick-Start Request.).165 E F1 2.75(A.1.1. ICMP)72 202 R F0
(Being a control protocol used between Internet nodes, one could ar)
100.8 228 Q(gue that ICMP is the)-.198 E
(ideal method for requesting a permission for f)100.8 241 Q
(aster startup from routers.)-.11 E(The ICMP header)5.5 E(is abo)100.8
254 Q .33 -.165(ve t)-.165 H(he IP header).165 E 5.5(.Q)-.605 G
(uick-Start could be accomplished with ICMP as follo)-5.5 E(ws: If the)
-.275 E(ICMP protocol is used to implement Quick-Start, the equi)100.8
267 Q -.275(va)-.275 G(lent of the Quick-Start IP).275 E(option w)100.8
280 Q
(ould be carried in the ICMP header of the ICMP Quick-Start Request.)
-.11 E(The ICMP)5.5 E(Quick-Start Request w)100.8 293 Q(ould ha)-.11 E
.33 -.165(ve t)-.22 H 2.75(op).165 G
(ass by the routers on the path to the recei)-2.75 E -.165(ve)-.275 G
(r; for no).165 E -.715(w,)-.275 G(we don')100.8 306 Q 2.75(ta)-.198 G
(ddress the mechanisms that w)-2.75 E
(ould be needed to accomplish this task.)-.11 E 2.75(Ar)5.5 G(outer)
-2.75 E(that appro)100.8 319 Q -.165(ve)-.165 G 2.75(st).165 G
(he Quick-Start Request w)-2.75 E(ould tak)-.11 E 2.75(et)-.11 G
(he same actions as in the case with the)-2.75 E
(Quick-Start IP Option, and forw)100.8 332 Q(ard the pack)-.11 E
(et to the ne)-.11 E(xt router along the path.)-.165 E 2.75(Ar)5.5 G
(outer)-2.75 E(that does not appro)100.8 345 Q .33 -.165(ve t)-.165 H
(he Quick-Start Request, e).165 E -.165(ve)-.275 G 2.75(nw).165 G
(ith a decreased v)-2.75 E(alue for the)-.275 E(Requested Rate, w)100.8
358 Q
(ould delete the ICMP Quick-Start Request, and send an ICMP Reply to)
-.11 E(the sender that the request w)100.8 371 Q(as not appro)-.11 E
-.165(ve)-.165 G 2.75(d. If).165 F(the ICMP Reply w)2.75 E
(as dropped in the)-.11 E(netw)100.8 384 Q
(ork, and did not reach the recei)-.11 E -.165(ve)-.275 G .88 -.44(r, t)
.165 H(he sender w).44 E(ould still kno)-.11 E 2.75(wt)-.275 G
(hat the request w)-2.75 E(as)-.11 E(not appro)100.8 397 Q -.165(ve)
-.165 G 2.75(df).165 G(rom the absence of feedback from the recei)-2.75
E -.165(ve)-.275 G 3.96 -.605(r. I).165 H 2.75(ft).605 G
(he ICMP Quick-Start)-2.75 E(request w)100.8 410 Q
(as dropped in the netw)-.11 E(ork due to congestion, the sender w)-.11
E(ould assume that the)-.11 E(request w)100.8 423 Q(as not appro)-.11 E
-.165(ve)-.165 G 2.75(d. If).165 F
(the ICMP Quick-Start Request reached the recei)2.75 E -.165(ve)-.275 G
.88 -.44(r, t).165 H(he).44 E(recei)100.8 436 Q -.165(ve)-.275 G 2.75
(rw).165 G(ould use transport-le)-2.86 E -.165(ve)-.275 G 2.75(lm).165 G
(echanisms to send a response to the sender)-2.75 E 2.75(,e)-.44 G
(xactly as)-2.915 E(with the IP Option.)100.8 449 Q
(One bene\214t of using ICMP w)100.8 475 Q(ould be that the deli)-.11 E
-.165(ve)-.275 G(ry of the TCP SYN pack).165 E(et or other)-.11 E
(initial pack)100.8 488 Q(et w)-.11 E
(ould not be delayed by IP option processing at routers.)-.11 E 2.75(Ag)
5.5 G(reater adv)-2.75 E(antage)-.275 E(is that if middlebox)100.8 501 Q
(es were blocking pack)-.165 E
(ets with Quick-Start Requests, using the Quick-)-.11 E
(Start Request in a separate ICMP pack)100.8 514 Q(et w)-.11 E
(ould mean that the middlebox beha)-.11 E(vior w)-.22 E(ould)-.11 E
(not af)100.8 527 Q(fect the connection as a whole.)-.275 E(\(T)5.5 E
2.75(og)-.88 G(et this rob)-2.75 E(ustness to middlebox)-.22 E
(es with TCP)-.165 E(using an IP Quick-Start Option, one w)100.8 540 Q
(ould ha)-.11 E .33 -.165(ve t)-.22 H 2.75(oh).165 G -2.475 -.22(av e)
-2.75 H 2.75(aT)2.97 G(CP-le)-2.75 E -.165(ve)-.275 G 2.75(lQ).165 G
(uick-Start Request)-2.75 E(pack)100.8 553 Q(et that w)-.11 E
(as sent concurrently b)-.11 E(ut separately from the TCP SYN pack)-.22
E(et.\))-.11 E(Ho)100.8 579 Q(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t)
.165 H(here are a number of disadv).44 E(antages to using ICMP)-.275 E
5.5(.S)-1.221 G(ome \214re)-5.5 E -.11(wa)-.275 G(lls and).11 E
(middlebox)100.8 592 Q(es may not forw)-.165 E
(ard the ICMP Quick-Start Request pack)-.11 E 2.75(ets. \(If)-.11 F
(an ICMP Reply)2.75 E(pack)100.8 605 Q
(et from a router to the sender is dropped in the netw)-.11 E
(ork, the sender w)-.11 E(ould still kno)-.11 E(w)-.275 E
(that the request w)100.8 618 Q(as not appro)-.11 E -.165(ve)-.165 G
(d, as stated earlier).165 E 2.75(,s)-.44 G 2.75(ot)-2.75 G(his w)-2.75
E(ould not be a problem.\))-.11 E(In)5.5 E(addition, it w)100.8 631 Q
(ould be dif)-.11 E(\214cult, if not impossible, for a router in the mi\
ddle of an IP tunnel to)-.275 E(deli)100.8 644 Q -.165(ve)-.275 G 2.75
(ra).165 G 2.75(nI)-2.75 G(CMP Reply pack)-2.75 E
(et to the actual source, for e)-.11 E
(xample when the inner IP header is)-.165 E
(encrypted as in IPsec tunnel mode [RFC2401].)100.8 657 Q(Ag)5.5 E
(ain, ho)-.055 E(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H
(he ICMP Reply pack).44 E(et)-.11 E -.11(wo)100.8 670 S
(uld not be essential to the correct operation of ICMP Quick-Start.).11
E(Unauthenticated out-of-band ICMP messages could enable some types of \
attacks by third-)100.8 696 Q(party malicious hosts that are not possib\
le when the control information is carried in-band)100.8 709 Q
(with the IP pack)100.8 722 Q(ets that can only be altered by the route\
rs on the connection path. Finally)-.11 E(,)-.715 E(Jain/Flo)72 769 Q
193.333(yd/Allman/Sarolahti Section)-.11 F 2.75(A.1.1. [P)2.75 F
(age 37])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(as a minor concern, using ICMP w)100.8 85 Q
(ould cause a small amount of additional traf)-.11 E(\214c in the)-.275
E(netw)100.8 98 Q(ork, which is not the case when using IP options.)-.11
E/F1 11/Times-Bold@0 SF 2.75(A.1.2. RSVP)72 137 R F0 -.44(Wi)100.8 163 S
(th some modi\214cations RSVP [RFC2205] could be used as a bearer proto\
col for carrying).44 E(the Quick-Start Requests. Because routers are e)
100.8 176 Q(xpected to process RSVP pack)-.165 E(ets more)-.11 E -.165
(ex)100.8 189 S(tensi).165 E -.165(ve)-.275 G
(ly than the normal transport protocol IP pack).165 E(ets, deli)-.11 E
-.165(ve)-.275 G(ring a Quick-Start rate).165 E
(request using an RSVP pack)100.8 202 Q(et w)-.11 E
(ould seem an appealing choice. Ho)-.11 E(we)-.275 E -.165(ve)-.275 G
.88 -.44(r, Q).165 H(uick-Start with).44 E(RSVP w)100.8 215 Q
(ould require a fe)-.11 E 2.75(wd)-.275 G(if)-2.75 E
(ferences from the con)-.275 E -.165(ve)-.44 G(ntional usage of RSVP)
.165 E 2.75(.Q)-1.221 G(uick-Start)-2.75 E -.11(wo)100.8 228 S(uld not \
require periodical refreshing of soft state, because Quick-Start does n\
ot require).11 E(per)100.8 241 Q(-connection state in routers.)-.22 E
(Quick-Start Requests w)5.5 E(ould be transmitted do)-.11 E(wnstream)
-.275 E(from the sender to recei)100.8 254 Q -.165(ve)-.275 G 2.75(ri)
.165 G 2.75(nt)-2.75 G(he RSVP P)-2.75 E(ath messages, which is dif)
-.165 E(ferent from the)-.275 E(con)100.8 267 Q -.165(ve)-.44 G
(ntional RSVP model where the reserv).165 E
(ations originate from the recei)-.275 E -.165(ve)-.275 G 1.21 -.605
(r. F).165 H(urthermore,).605 E(the Quick-Start Response w)100.8 280 Q
(ould be sent using the transport-le)-.11 E -.165(ve)-.275 G 2.75(lm)
.165 G(echanisms instead of)-2.75 E(using the RSVP Resv message.)100.8
293 Q(If RSVP w)100.8 319 Q
(as used for carrying a Quick-Start Request, a ne)-.11 E 2.75(w")-.275 G
(Quick-Start Request" class)-2.75 E(object w)100.8 332 Q
(ould be included in the RSVP P)-.11 E
(ath message that is sent from the sender to)-.165 E(recei)100.8 345 Q
-.165(ve)-.275 G 1.21 -.605(r. T).165 H(he object w).605 E
(ould contain the rate request \214eld in addition to the common length)
-.11 E(and type \214elds. The Send_TTL \214eld in the RSVP common heade\
r could be used as the)100.8 358 Q(equi)100.8 371 Q -.275(va)-.275 G
(lent of the QS TTL \214eld.).275 E
(The Quick-Start capable routers along the path w)5.5 E(ould)-.11 E
(inspect the Quick-Start Request object in the RSVP P)100.8 384 Q
(ath message, decrement Send_TTL)-.165 E(and adjust the rate request \
\214eld if needed. If an RSVP router did not understand the Quick-)100.8
397 Q(Start Request object, it w)100.8 410 Q
(ould reject the entire RSVP message and send an RSVP P)-.11 E(athErr)
-.165 E(message back to the sender)100.8 423 Q 5.5(.W)-.605 G
(hen an RSVP message with the Quick-Start Request object)-5.5 E
(reaches the recei)100.8 436 Q -.165(ve)-.275 G .88 -.44(r, t).165 H
(he recei).44 E -.165(ve)-.275 G 2.75(rs).165 G
(ends a Quick-Start Reply message in the corresponding)-2.75 E
(transport protocol header in the same w)100.8 449 Q
(ay as described in the conte)-.11 E(xt of IP options earlier)-.165 E(.)
-.605 E(If the RSVP message with the Quick-Start Request object w)100.8
462 Q(as dropped along the path, the)-.11 E(transport sender w)100.8 475
Q(ould simply proceed with the normal congestion control procedures.)
-.11 E(Much of the discussion about bene\214ts and dra)100.8 501 Q
(wbacks of using ICMP for making the)-.165 E(Quick-Start Request also a\
pplies to the RSVP case. If the Quick-Start Request w)100.8 514 Q(as)
-.11 E(transmitted in a separate pack)100.8 527 Q
(et instead of as an IP option, the transport protocol pack)-.11 E(et)
-.11 E(deli)100.8 540 Q -.165(ve)-.275 G(ry w).165 E(ould not be delaye\
d due to IP option processing at the routers, and the initial)-.11 E
(transport pack)100.8 553 Q(ets w)-.11 E
(ould reach their destination more reliably)-.11 E 2.75(.T)-.715 G
(he possible disadv)-2.75 E(antages)-.275 E
(of using ICMP and RSVP are also e)100.8 566 Q
(xpected to be similar: middlebox)-.165 E(es in the netw)-.165 E
(ork may)-.11 E(not be able to forw)100.8 579 Q
(ard the Quick-Start Request messages, and the IP tunnels might cause)
-.11 E(problems for processing the Quick-Start Requests.)100.8 592 Q F1
(A.2.)72 631 Q/F2 13/Times-Bold@0 SF(Alter)5.5 E
(nate Encoding Functions)-.195 E F0(In this section we look at alternat\
e encoding functions for the Rate Request \214eld in the)100.8 657 Q
(Quick-Start Request.)100.8 670 Q
(The main requirements for this function is that it should ha)5.5 E .33
-.165(ve a)-.22 H(suf)100.8 683 Q
(\214ciently wide range for the requested rate.)-.275 E
(There is no need for o)5.5 E -.165(ve)-.165 G(rly-\214ne-grained).165 E
(precision in the requested rate.)100.8 696 Q(Similarly)5.5 E 2.75(,w)
-.715 G(hile it w)-2.75 E(ould be attracti)-.11 E .33 -.165(ve f)-.275 H
(or the encoding).165 E(function to be easily computable, it is also po\
ssible for end-nodes and routers to simply)100.8 709 Q
(store the table gi)100.8 722 Q(ving the mapping between the v)-.275 E
(alue N in the Rate Request \214eld, and the)-.275 E(Jain/Flo)72 769 Q
201.583(yd/Allman/Sarolahti Section)-.11 F 2.75(A.2. [P)2.75 F(age 38])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(actual rate request f\(N\).)100.8 85 Q
(In this section we consider both four)5.5 E(-bit and eight-bit Rate)
-.22 E(Request \214elds.)100.8 98 Q(Linear functions:)100.8 124 Q(The Q\
uick-Start Request contains an 8-bit \214eld for the Rate Request.)100.8
137 Q(One possible)5.5 E(proposal w)100.8 150 Q(ould be for this \214el\
d to be formatted in bits per second, scaled so that one unit)-.11 E
(equals 80 Kbps.)100.8 163 Q(Thus, for the v)5.5 E
(alue N in the Rate Request \214eld, the requested rate is)-.275 E
(80,000*N bps.)100.8 176 Q(This gi)5.5 E -.165(ve)-.275 G 2.75(sar).165
G(equest range between 80 Kbps and 20.48 Mbps.)-2.75 E -.165(Fo)5.5 G(r)
.165 E(1500-byte pack)100.8 189 Q
(ets, this corresponds to a request range between 6 and 1706 pack)-.11 E
(ets per)-.11 E(second.)100.8 202 Q(Po)100.8 228 Q(wers of tw)-.275 E
(o:)-.11 E(If a granularity of f)100.8 241 Q(actors of tw)-.11 E 2.75
(oi)-.11 G 2.75(ss)-2.75 G(uf)-2.75 E
(\214cient for the Rate Request, then the encoding)-.275 E
(function with the most range w)100.8 254 Q
(ould be for the requested rate to be K*2^N, for N the v)-.11 E(alue)
-.275 E(in the Rate Request \214eld, and for K some constant.)100.8 267
Q -.165(Fo)5.5 G 2.75(rN).165 G(=0, the rate request w)-2.75 E
(ould be set)-.11 E(to zero, re)100.8 280 Q -.055(ga)-.165 G
(rdless of the encoding function.).055 E -.165(Fo)5.5 G 2.75(re).165 G
(xample, for K=40,000, the request range)-2.915 E -.11(wo)100.8 293 S
(uld be from 80 Kbps to 40*2^256 Kbps.).11 E(This clearly w)5.5 E
(ould be an unnecessarily lar)-.11 E(ge)-.198 E(request range.)100.8 306
Q -.165(Fo)100.8 332 S 2.75(raf).165 G(our)-2.75 E(-bit Rate Request \
\214eld, the upper limit on the rate request is 1.3 Gbps.)-.22 E(It is)
5.5 E(possible that an upper limit of 1.3 Gbps w)100.8 345 Q
(ould be \214ne for the Quick-Start rate request, and)-.11 E(that conne\
ctions wishing to start up with a higher initial sending rate should be\
 encouraged)100.8 358 Q(to use other mechanisms, such as the e)100.8 371
Q(xplicit reserv)-.165 E(ation of bandwidth.)-.275 E
(If an upper limit of)5.5 E(1.3 Gbps is not acceptable, then \214v)100.8
384 Q 2.75(eb)-.165 G(its could be used for the Rate Request \214eld.)
-2.75 E(If the granularity of f)100.8 410 Q(actors of tw)-.11 E 2.75(oi)
-.11 G 2.75(st)-2.75 G
(oo coarse, then the encoding function could use a)-2.75 E
(base less than tw)100.8 423 Q 2.75(o. An)-.11 F
(alternate form for the encoding function w)2.75 E(ould be to use a h)
-.11 E(ybrid)-.055 E(of linear and e)100.8 436 Q(xponential functions.)
-.165 E 1.76 -.88(We n)100.8 462 T(ote that the Rate Request also has t\
o be constrained by the abilities of the transport).88 E 2.75
(protocol. F)100.8 475 R(or e)-.165 E(xample, for TCP with W)-.165 E
(indo)-.44 E 2.75(wS)-.275 G(caling, the maximum windo)-2.75 E 2.75(wi)
-.275 G 2.75(sa)-2.75 G 2.75(tm)-2.75 G(ost)-2.75 E(2**30 bytes.)100.8
488 Q -.165(Fo)5.5 G 2.75(raT).165 G
(CP connection with a long, 1 second round-trip time, this w)-2.75 E
(ould gi)-.11 E -.165(ve)-.275 G 2.75(am)100.8 501 S
(aximum sending rate of 1.07 Gbps.)-2.75 E/F1 11/Times-Bold@0 SF(A.3.)72
540 Q/F2 13/Times-Bold@0 SF(The Quick-Start Request: P)5.5 E(ack)-.13 E
(ets or Bytes?)-.13 E F0(One of the design questions is whether the Rat\
e Request \214eld should be in bytes per second)100.8 566 Q(or in pack)
100.8 579 Q(ets per second.)-.11 E 1.76 -.88(We w)5.5 H
(ill discuss this separately from the perspecti).88 E .33 -.165(ve o)
-.275 H 2.75(ft).165 G(he)-2.75 E(transport, and from the perspecti)
100.8 592 Q .33 -.165(ve o)-.275 H 2.75(ft).165 G(he router)-2.75 E(.)
-.605 E -.165(Fo)100.8 618 S 2.75(rT).165 G(CP)-2.75 E 2.75(,t)-1.221 G
(he results from the Quick-Start Request are translated into a congesti\
on windo)-2.75 E(w)-.275 E
(in bytes, using the measured round-trip time and the MSS.)100.8 631 Q
(This windo)5.5 E 2.75(wa)-.275 G(pplies only to)-2.75 E(the bytes of d\
ata payload, and does not include the bytes in the TCP or IP pack)100.8
644 Q(et headers.)-.11 E(Other transport protocols w)100.8 657 Q
(ould concei)-.11 E -.275(va)-.275 G
(bly use the Quick-Start Request directly in).275 E(pack)100.8 670 Q(et\
s per second, or could translate the Quick-Start Request to a congestio\
n windo)-.11 E 2.75(wi)-.275 G(n)-2.75 E(pack)100.8 683 Q(ets.)-.11 E
(The assumption of this draft is that the router only appro)100.8 709 Q
-.165(ve)-.165 G 2.75(st).165 G(he Quick-Start Request when)-2.75 E
(the output link is signi\214cantly underutilized.)100.8 722 Q -.165(Fo)
5.5 G 2.75(rt).165 G(his, the router could measure the)-2.75 E(Jain/Flo)
72 769 Q 201.583(yd/Allman/Sarolahti Section)-.11 F 2.75(A.3. [P)2.75 F
(age 39])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E -.22(av)
100.8 85 S(ailable bandwidth in bytes per second, or could con)-.055 E
-.165(ve)-.44 G(rt between pack).165 E(ets and bytes by)-.11 E
(some mechanism.)100.8 98 Q(If the Quick-Start Request w)100.8 124 Q
(as in bytes per second, and applied only to the data payload,)-.11 E
(then the router w)100.8 137 Q(ould ha)-.11 E .33 -.165(ve t)-.22 H 2.75
(oc).165 G(on)-2.75 E -.165(ve)-.44 G
(rt from bytes per second of data payload, to bytes per).165 E
(second of pack)100.8 150 Q(ets on the wire.)-.11 E
(If the Rate Request \214eld w)5.5 E(as in bytes per second and the)-.11
E(sender ended up using v)100.8 163 Q(ery small pack)-.165 E
(ets, this could translate to a signi\214cantly lar)-.11 E(ger)-.198 E
(number in terms of bytes per second on the wire.)100.8 176 Q
(Therefore, for a Quick-Start Request in)5.5 E(bytes per second, it mak)
100.8 189 Q
(es most sense for this to include the transport and IP headers as)-.11
E(well as the data payload.)100.8 202 Q
(Of course, this will be at best a rough approximation on the part)5.5 E
(of the sender; the transport-le)100.8 215 Q -.165(ve)-.275 G 2.75(ls)
.165 G(ender might not kno)-2.75 E 2.75(wt)-.275 G
(he size of the transport and IP)-2.75 E
(headers in bytes, and might kno)100.8 228 Q 2.75(wn)-.275 G
(othing at all about the separate headers added in IP)-2.75 E
(tunnels do)100.8 241 Q 2.75(wnstream. This)-.275 F
(rough estimate seems suf)2.75 E(\214cient, ho)-.275 E(we)-.275 E -.165
(ve)-.275 G .88 -.44(r, g).165 H -2.365 -.275(iv e).44 H 2.75(nt).275 G
(he o)-2.75 E -.165(ve)-.165 G(rall lack).165 E
(of \214ne precision in Quick-Start functionality)100.8 254 Q(.)-.715 E
(It has been suggested that the router could possibly use information f\
rom the MSS option)100.8 280 Q(in the TCP pack)100.8 293 Q
(et header of the SYN pack)-.11 E(et to con)-.11 E -.165(ve)-.44 G
(rt the Quick-Start Request from).165 E(pack)100.8 306 Q
(ets per second to bytes per second, or vice v)-.11 E 2.75(ersa. The)
-.165 F(MSS option is de\214ned as the)2.75 E
(maximum MSS that the TCP sender e)100.8 319 Q(xpects to recei)-.165 E
-.165(ve)-.275 G 2.75(,n).165 G(ot the maximum MSS that the)-2.75 E
(TCP sender plans to send [RFC793].)100.8 332 Q(Ho)5.5 E(we)-.275 E
-.165(ve)-.275 G .88 -.44(r, i).165 H 2.75(ti).44 G 2.75(sp)-2.75 G
(robably often the case that this MSS)-2.75 E(also applies as an upper \
bound on the MSS used by the TCP sender in sending.)100.8 345 Q 1.76
-.88(We n)100.8 371 T(ote that the sender does not necessarily kno).88 E
2.75(wt)-.275 G(he P)-2.75 E(ath MTU when the Quick-Start)-.165 E
(Request is sent, or when the initial windo)100.8 384 Q 2.75(wo)-.275 G
2.75(fd)-2.75 G(ata is sent.)-2.75 E(Thus, with IPv4, pack)5.5 E
(ets from)-.11 E(the initial windo)100.8 397 Q 2.75(wc)-.275 G
(ould end up being fragmented in the netw)-2.75 E(ork if the "Don')-.11
E 2.75(tF)-.198 G(ragment")-2.75 E(\(DF\) bit is not set [RFC1191].)
100.8 410 Q 2.75(AR)5.5 G
(ate Request in bytes per second is reasonably rob)-2.75 E(ust to)-.22 E
2.75(fragmentation. Clearly)100.8 423 R 2.75(aR)2.75 G
(ate Request in pack)-2.75 E(ets per second is less rob)-.11 E
(ust in the presence)-.22 E(of fragmentation.)100.8 436 Q
(Interactions between lar)5.5 E(ger initial windo)-.198 E(ws and P)-.275
E(ath MTU Disco)-.165 E -.165(ve)-.165 G(ry).165 E
(are discussed in more detail in RFC 3390 [RFC3390].)100.8 449 Q -.165
(Fo)100.8 475 S 2.75(raQ).165 G
(uick-Start Request in bytes per second, the transport senders w)-2.75 E
(ould ha)-.11 E .33 -.165(ve t)-.22 H(he).165 E(additional complication\
 of estimating the bandwidth usage added by the pack)100.8 488 Q
(et headers.)-.11 E 1.76 -.88(We h)100.8 514 T -2.475 -.22(av e).88 H
(chosen an Rate Request \214eld in bytes per second rather than in pack)
2.97 E(ets per second)-.11 E(because it seems some)100.8 527 Q
(what more rob)-.275 E(ust, particularly to routers.)-.22 E/F1 11
/Times-Bold@0 SF(A.4.)72 566 Q/F2 13/Times-Bold@0 SF
(Quick-Start Semantics: T)5.5 E(otal Rate or Additional Rate?)-1.196 E
F0 -.165(Fo)100.8 592 S 2.75(raQ).165 G
(uick-Start Request sent in the middle of a connection, there are tw)
-2.75 E 2.75(op)-.11 G(ossible)-2.75 E
(semantics for the Rate Request \214eld, as follo)100.8 605 Q(ws:)-.275
E(\(1\) T)100.8 631 Q(otal Rate: The requested Rate Request is the requ\
ested total rate for the connection,)-.88 E
(including the current rate; or)100.8 644 Q(\(2\) Additional Rate: The \
requested Rate Request is the requested increase in the total rate)100.8
670 Q(for that connection, o)100.8 683 Q -.165(ve)-.165 G 2.75(ra).165 G
(nd abo)-2.75 E .33 -.165(ve t)-.165 H(he current sending rate.).165 E(\
When the Quick-Start Request is sent after an idle period, the current \
sending rate is zero,)100.8 709 Q(and there is no dif)100.8 722 Q
(ference between \(1\) and \(2\) abo)-.275 E -.165(ve)-.165 G 5.5(.H)
.165 G -.275(ow)-5.5 G -2.365 -.275(ev e).275 H .88 -.44(r, a Q).275 H
(uick-Start Request can).44 E(Jain/Flo)72 769 Q 201.583
(yd/Allman/Sarolahti Section)-.11 F 2.75(A.4. [P)2.75 F(age 40])-.165 E
0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(also be\
 sent in the middle of a connection that has not been idle, e.g., after\
 a mobility e)100.8 85 Q -.165(ve)-.275 G(nt,).165 E(or after an applic\
ation-limited period when the sender is suddenly ready to send at a muc\
h)100.8 98 Q(higher rate.)100.8 111 Q
(In this case, there can be a signi\214cant dif)5.5 E
(ference between \(1\) and \(2\) abo)-.275 E -.165(ve)-.165 G 5.5(.I)
.165 G(n)-5.5 E(this section we consider brie\215y the tradeof)100.8 124
Q(fs between these tw)-.275 E 2.75(oo)-.11 G(ptions, and e)-2.75 E
(xplain wh)-.165 E(y)-.055 E(we ha)100.8 137 Q .33 -.165(ve c)-.22 H
(hosen the `T).165 E(otal Rate' semantics.)-.88 E(The T)100.8 163 Q
(otal Rate semantics mak)-.88 E(es it easier for routers to `)-.11 E
(`allocate')-.814 E 2.75('t)-.814 G(he same rate to all)-2.75 E 2.75
(connections. This)100.8 176 R(lends itself to f)2.75 E
(airness, and impro)-.11 E -.165(ve)-.165 G 2.75(sc).165 G(on)-2.75 E
-.165(ve)-.44 G -.198(rg).165 G(ence times between old and).198 E(ne)
100.8 189 Q 2.75(wc)-.275 G 2.75(onnections. W)-2.75 F
(ith the Additional Rate semantics, the router w)-.44 E
(ould not necessarily)-.11 E(kno)100.8 202 Q 2.75(wt)-.275 G
(he current sending rates of the \215o)-2.75 E
(ws requesting additional rates, and therefore w)-.275 E(ould)-.11 E
(not ha)100.8 215 Q .33 -.165(ve s)-.22 H(uf).165 E
(\214cient information to use f)-.275 E
(airness as a metric in granting rate requests.)-.11 E -.44(Wi)5.5 G(th)
.44 E(the T)100.8 228 Q(otal Rate semantics, the f)-.88 E
(airness is automatic; the router is not granting rate requests)-.11 E
(for *additional* bandwidth without kno)100.8 241 Q
(wing the current sending rates of the dif)-.275 E(ferent)-.275 E<8d6f>
100.8 254 Q(ws.)-.275 E
(The Additional Rate semantics also lends itself to g)100.8 280 Q
(aming by the connection, with senders)-.055 E
(sending frequent Quick-Start Requests in the hope of g)100.8 293 Q
(aining a higher rate.)-.055 E(If the router is)5.5 E(granting the same\
 maximum rate for all rate requests, then there is little bene\214t to \
a)100.8 306 Q(connection of sending a rate request o)100.8 319 Q -.165
(ve)-.165 G 2.75(ra).165 G(nd o)-2.75 E -.165(ve)-.165 G 2.75(ra).165 G
-.055(ga)-2.75 G 2.75(in. Ho).055 F(we)-.275 E -.165(ve)-.275 G .88 -.44
(r, i).165 H 2.75(ft).44 G(he router is granting)-2.75 E
(an *additional* rate with each rate request, o)100.8 332 Q -.165(ve)
-.165 G 2.75(ra).165 G(nd abo)-2.75 E .33 -.165(ve t)-.165 H
(he current sending rate, then it).165 E(is in a connection')100.8 345 Q
2.75(si)-.605 G(nterest to send as man)-2.75 E 2.75(yr)-.165 G
(ate requests as possible, e)-2.75 E -.165(ve)-.275 G 2.75(ni).165 G
2.75(fv)-2.75 G(ery fe)-2.915 E 2.75(wo)-.275 G(f)-2.75 E(them are in f)
100.8 358 Q(act granted.)-.11 E -.165(Fo)100.8 384 S 2.75(re).165 G
(ither of these alternati)-2.75 E -.165(ve)-.275 G(s, there w).165 E
(ould not be room to report the current sending rate)-.11 E(in the Quic\
k-Start Option using the current minimal format for the Quick-Start Req\
uest.)100.8 397 Q(Thus, either the Quick-Start Option w)100.8 410 Q
(ould ha)-.11 E .33 -.165(ve t)-.22 H 2.75(ot).165 G(ak)-2.75 E 2.75(em)
-.11 G(ore than four bytes to include a)-2.75 E
(report of the current sending rate, or the current sending rate w)100.8
423 Q(ould not be reported to the)-.11 E(routers.)100.8 436 Q/F1 11
/Times-Bold@0 SF(A.5.)72 475 Q/F2 13/Times-Bold@0 SF(Alter)5.5 E
(nate Responses to the Loss of a Quick-Start P)-.195 E(ack)-.13 E(et)
-.13 E F0(Section 4.5 discusses TCP')100.8 501 Q 2.75(sr)-.605 G
(esponse to the loss of a Quick-Start pack)-2.75 E(et in the initial)
-.11 E(windo)100.8 514 Q 4.18 -.715(w. T)-.275 H
(his section discusses se).715 E -.165(ve)-.275 G
(ral alternate responses.).165 E(One possible alternati)100.8 540 Q .33
-.165(ve t)-.275 H 2.75(or).165 G -2.365 -.275(ev e)-2.75 H
(rting to the def).275 E(ault slo)-.11 E
(w-start after the loss of a Quick-Start)-.275 E(pack)100.8 553 Q
(et from the initial windo)-.11 E 2.75(ww)-.275 G(ould ha)-2.86 E .33
-.165(ve b)-.22 H(een to halv).165 E 2.75(et)-.165 G
(he congestion windo)-2.75 E 2.75(wa)-.275 G(nd)-2.75 E
(continue in congestion a)100.8 566 Q -.22(vo)-.22 G 2.75(idance. Ho).22
F(we)-.275 E -.165(ve)-.275 G .88 -.44(r, w).165 H 2.75(en).44 G
(ote that this w)-2.75 E(ould not ha)-.11 E .33 -.165(ve b)-.22 H(een a)
.165 E(desirable response for either the connection or for the netw)
100.8 579 Q(ork as a whole.)-.11 E(The pack)5.5 E(et loss)-.11 E
(in the initial windo)100.8 592 Q 2.75(wi)-.275 G
(ndicates that Quick-Start f)-2.75 E
(ailed in \214nding an appropriate congestion)-.11 E(windo)100.8 605 Q
1.43 -.715(w, m)-.275 H(eaning that the congestion windo).715 E 2.75(wa)
-.275 G(fter halving may easily also be wrong.)-2.75 E 2.75(Am)100.8 631
S(ore moderate alternate w)-2.75 E(ould be to continue in congestion a)
-.11 E -.22(vo)-.22 G(idance from a windo).22 E 2.75(wo)-.275 G(f)-2.75
E(\(W)100.8 644 Q(-D\)/2, where W is the Quick-Start congestion windo)
-.715 E 1.43 -.715(w, a)-.275 H(nd D is the number of pack).715 E(ets)
-.11 E(dropped or mark)100.8 657 Q(ed from that windo)-.11 E 4.18 -.715
(w. H)-.275 H -.275(ow).715 G -2.365 -.275(ev e).275 H .88 -.44(r, s)
.275 H(uch an approach w).44 E(ould implicitly)-.11 E
(assume that the number of Quick-Start pack)100.8 670 Q(ets deli)-.11 E
-.165(ve)-.275 G(red is a good indication of the).165 E(appropriate a)
100.8 683 Q -.275(va)-.22 G(ilable bandwidth for that \215o).275 E 1.43
-.715(w, e)-.275 H -.165(ve).44 G 2.75(nt).165 G(hough other pack)-2.75
E(ets from that windo)-.11 E(w)-.275 E(were dropped in the netw)100.8
696 Q 2.75(ork. W)-.11 F 2.75(eb)-.88 G(elie)-2.75 E .33 -.165(ve t)
-.275 H(hat such an assumption w).165 E(ould require more)-.11 E
(analysis at this point, particularly in a netw)100.8 709 Q
(ork with a range of pack)-.11 E(et dropping)-.11 E
(mechanisms at the router)100.8 722 Q 2.75(,a)-.44 G
(nd we cannot recommend it at this time.)-2.75 E(Jain/Flo)72 769 Q
201.583(yd/Allman/Sarolahti Section)-.11 F 2.75(A.5. [P)2.75 F(age 41])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(Another dra)100.8 85 Q(wback of approaches that don')-.165 E 2.75(tr)
-.198 G -2.365 -.275(ev e)-2.75 H(rt back to slo).275 E
(w-start when a Quick-Start)-.275 E(pack)100.8 98 Q
(et in the initial windo)-.11 E 2.75(wi)-.275 G 2.75(sd)-2.75 G
(ropped is that an)-2.75 E 2.75(ys)-.165 G(uch approaches could gi)-2.75
E .33 -.165(ve t)-.275 H(he TCP).165 E(recei)100.8 111 Q -.165(ve)-.275
G 2.75(ra).165 G 2.75(ni)-2.75 G(ncenti)-2.75 E .33 -.165(ve t)-.275 H
2.75(ol).165 G(ie about the Quick-Start request.)-2.75 E
(That is, if the sender re)5.5 E -.165(ve)-.275 G(rts to).165 E(slo)
100.8 124 Q(w-start when a Quick-Start pack)-.275 E
(et is dropped, then it is generally not to the recei)-.11 E -.165(ve)
-.275 G(r').165 E(s)-.605 E(adv)100.8 137 Q(antage to report a lar)-.275
E(ger rate request than w)-.198 E(as actually appro)-.11 E -.165(ve)
-.165 G 2.75(di).165 G 2.75(ft)-2.75 G(he result is going to)-2.75 E
(be a Quick-Start pack)100.8 150 Q(et dropped in the netw)-.11 E 2.75
(ork. Ho)-.11 F(we)-.275 E -.165(ve)-.275 G .88 -.44(r, i).165 H 2.75
(ft).44 G(he recei)-2.75 E -.165(ve)-.275 G 2.75(rb).165 G
(ene\214ts from a)-2.75 E(lar)100.8 163 Q(ger Quick-Start windo)-.198 E
2.75(we)-.275 G -.165(ve)-3.025 G 2.75(nw).165 G(hen the lar)-2.75 E
(ger windo)-.198 E 2.75(wr)-.275 G(esults in Quick-Start pack)-2.75 E
(ets)-.11 E(dropped in the netw)100.8 176 Q(ork, then the recei)-.11 E
-.165(ve)-.275 G 2.75(rh).165 G(as a greater incenti)-2.75 E .33 -.165
(ve t)-.275 H 2.75(ol).165 G(ie about the recei)-2.75 E -.165(ve)-.275 G
(d).165 E(rate request, in an ef)100.8 189 Q
(fort to get the sender to use a lar)-.275 E(ger initial sending rate.)
-.198 E/F1 11/Times-Bold@0 SF(A.6.)72 228 Q/F2 13/Times-Bold@0 SF(Wh)5.5
E 3.25(yN)-.195 G(ot Include Mor)-3.25 E 3.25(eF)-.234 G(unctionality?)
-3.25 E F0(As Section 6.5 discussed, this proposal for Quick-Start is a\
 rather coarse-grained)100.8 254 Q(mechanism that w)100.8 267 Q
(ould allo)-.11 E 2.75(wc)-.275 G
(onnections to use higher sending rates along underutilized)-2.75 E
(paths, b)100.8 280 Q(ut that does not attempt to pro)-.22 E(vide a ne)
-.165 E(xt-generation transport protocol, and does)-.165 E
(not attempt the goal of pro)100.8 293 Q(viding v)-.165 E
(ery high throughput with v)-.165 E(ery lo)-.165 E 2.75(wd)-.275 G(elay)
-2.75 E 5.5(.A)-.715 G 2.75(sS)-5.5 G(ection 7.4)-2.75 E
(discusses, there are a number of proposals such as XCP)100.8 306 Q 2.75
(,M)-1.221 G(axNet, and AntiECN for more)-2.75 E(\214ne-grained per)
100.8 319 Q(-pack)-.22 E
(et feedback from routers that the current congestion control)-.11 E
(mechanisms, that do attempt these more ambitious goals.)100.8 332 Q
(Compared to proposals such as XCP and AntiECN, Quick-Start of)100.8 358
Q(fers much less control.)-.275 E(Quick-Start does not attempt to pro)
100.8 371 Q(vide a ne)-.165 E 2.75(wc)-.275 G
(ongestion control mechanism, b)-2.75 E(ut simply)-.22 E(to get permiss\
ion from routers for a higher sending rate at start-up, or after an idl\
e period.)100.8 384 Q(Quick-Start can be thought of as an "anti-congest\
ion-control" mechanism, that is only of)100.8 397 Q(an)100.8 410 Q 2.75
(yu)-.165 G
(se when all of the routers along the path are signi\214cantly under)
-2.75 E 2.75(-utilized. Thus,)-.22 F(Quick-Start is of no use to)100.8
423 Q -.11(wa)-.275 G(rds a tar).11 E
(get of high link utilization, or f)-.198 E(airness in a high-)-.11 E(u\
tilization scenario, or controlling queueing delay during high-utilizat\
ion, or an)100.8 436 Q(ything of)-.165 E(the lik)100.8 449 Q(e.)-.11 E
(At the same time, Quick-Start w)100.8 475 Q(ould allo)-.11 E 2.75(wl)
-.275 G(ar)-2.75 E(ger initial windo)-.198 E(ws than w)-.275 E
(ould proposals)-.11 E
(such as AntiECN, requires less input to routers than XCP)100.8 488 Q
2.75(,a)-1.221 G(nd w)-2.75 E(ould require less frequent)-.11 E
(feedback from routers than an)100.8 501 Q 2.75(yn)-.165 G .55 -.275
(ew c)-2.75 H(ongestion control mechanism.).275 E(Thus, Quick-Start is)
5.5 E(signi\214cantly less po)100.8 514 Q(werful than proposals for ne)
-.275 E 2.75(wc)-.275 G(ongestion control mechanisms such as)-2.75 E
(XCP and AntiECN, b)100.8 527 Q(ut as po)-.22 E(werful or more po)-.275
E(werful in terms of the speci\214c issue of)-.275 E(allo)100.8 540 Q
(wing lar)-.275 E(ger initial windo)-.198 E
(ws, and \(we think\) more amenable to incremental deplo)-.275 E(yment)
-.11 E(in the current Internet.)100.8 553 Q 1.76 -.88(We d)100.8 579 T
2.75(on).88 G(ot discuss proposals such as XCP in detail, b)-2.75 E
(ut simply note that there are a number)-.22 E(of open questions.)100.8
592 Q(One question concerns whether there is a pressing need for more)
5.5 E(sophisticated congestion control mechanisms such as XCP in the In\
ternet.)100.8 605 Q(Quick-Start is)5.5 E
(inherently a rather crude tool that does not deli)100.8 618 Q -.165(ve)
-.275 G 2.75(ra).165 G(ssurances about maintaining high link)-2.75 E
(utilization and lo)100.8 631 Q 2.75(wq)-.275 G(ueueing delay;)-2.75 E
(Quick-Start is designed for use in en)5.5 E(vironments that)-.44 E(are\
 signi\214cantly underutilized, and addresses the single question of wh\
ether a higher)100.8 644 Q(sending rate is allo)100.8 657 Q 2.75
(wed. Ne)-.275 F 2.75(wc)-.275 G
(ongestion control mechanisms with more \214ne-grained)-2.75 E
(feedback from routers could allo)100.8 670 Q 2.75(wf)-.275 G
(aster startups e)-2.86 E -.165(ve)-.275 G 2.75(ni).165 G 2.75(ne)-2.75
G -.44(nv)-2.75 G(ironments with rather high).44 E(link utilization.)
100.8 683 Q(Is this a pressing requirement?)5.5 E
(Are the other bene\214ts of more \214ne-grained)5.5 E
(congestion control feedback from routers a pressing requirement?)100.8
696 Q 1.76 -.88(We w)100.8 722 T(ould ar).77 E(gue that e)-.198 E -.165
(ve)-.275 G 2.75(ni).165 G 2.75(fm)-2.75 G(ore \214ne-grained per)-2.75
E(-pack)-.22 E(et feedback from routers w)-.11 E(as)-.11 E(Jain/Flo)72
769 Q 201.583(yd/Allman/Sarolahti Section)-.11 F 2.75(A.6. [P)2.75 F
(age 42])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(implemented, it is reasonable to ha)100.8 85 Q .33 -.165(ve a s)-.22 H
(eparate mechanism such as Quick-Start for).165 E(indicating an allo)
100.8 98 Q(wed initial sending rate, or an allo)-.275 E
(wed total sending rate after an idle or)-.275 E(underutilized period.)
100.8 111 Q(One dif)100.8 137 Q(ference between Quick-Start and current\
 proposals for \214ne-grained per)-.275 E(-pack)-.22 E(et)-.11 E
(feedback such as XCP is that XCP is designed to gi)100.8 150 Q .33
-.165(ve r)-.275 H(ob).165 E(ust performance e)-.22 E -.165(ve)-.275 G
2.75(ni).165 G 2.75(nt)-2.75 G(he case)-2.75 E(where dif)100.8 163 Q
(ferent pack)-.275 E(ets within a connection routinely follo)-.11 E 2.75
(wd)-.275 G(if)-2.75 E(ferent paths.)-.275 E(XCP achie)5.5 E -.165(ve)
-.275 G(s).165 E(relati)100.8 176 Q -.165(ve)-.275 G(ly rob).165 E
(ust performance in the presence of multi-path routing by using per)-.22
E(-pack)-.22 E(et)-.11 E
(feedback, where the feedback carried in a single pack)100.8 189 Q
(et is about the relati)-.11 E .33 -.165(ve i)-.275 H(ncrease or).165 E
(decrease in the rate or windo)100.8 202 Q 2.75(wt)-.275 G 2.75(ot)-2.75
G(ak)-2.75 E 2.75(ee)-.11 G -.275(ff)-2.75 G
(ect when that particular pack).275 E(et is ackno)-.11 E(wledged,)-.275
E(not about the allo)100.8 215 Q
(wed sending rate for the connection as a whole.)-.275 E(In contrast, Q\
uick-Start sends a single Quick-Start request, and the answer to that r\
equest)100.8 241 Q(gi)100.8 254 Q -.165(ve)-.275 G 2.75(st).165 G
(he allo)-2.75 E(wed sending rate for an entire windo)-.275 E 2.75(wo)
-.275 G 2.75(fd)-2.75 G 2.75(ata. As)-2.75 F 2.75(ar)2.75 G
(esult, Quick-Start could)-2.75 E(be problematic in an en)100.8 267 Q
(vironment where some fraction of the pack)-.44 E(ets in a windo)-.11 E
2.75(wo)-.275 G 2.75(fd)-2.75 G(ata)-2.75 E(tak)100.8 280 Q 2.75(ep)-.11
G(ath A, and the rest of the pack)-2.75 E(ets tak)-.11 E 2.75(ep)-.11 G
(ath B;)-2.75 E(for e)5.5 E(xample, the Quick-Start Request)-.165 E
(could ha)100.8 293 Q .33 -.165(ve t)-.22 H(ra).165 E -.165(ve)-.22 G
(lled on path A, while half of the Quick-Start pack).165 E
(ets sent in the succeeding)-.11 E
(round-trip time are routed on path B.)100.8 306 Q(There are also dif)
100.8 332 Q
(ferences between Quick-Start and some of the proposals for per)-.275 E
(-pack)-.22 E(et)-.11 E(feedback in terms of the number of bits of feed\
back required from the routers to the end-)100.8 345 Q 2.75
(nodes. Quick-Start)100.8 358 R
(uses four bits of feedback in the rate request \214eld to indicate the)
2.75 E(allo)100.8 371 Q(wed sending rate.)-.275 E
(XCP allocates a byte for per)5.5 E(-pack)-.22 E
(et feedback, though there has been)-.11 E(discussion of v)100.8 384 Q
(ariants of XCP with less per)-.275 E(-pack)-.22 E(et feedback.)-.11 E
(This w)5.5 E(ould be more lik)-.11 E(e)-.11 E(other proposals such as \
anti-ECN that use a single bit of feedback from routers to indicate)
100.8 397 Q(that the sender can increase as f)100.8 410 Q(ast as slo)
-.11 E(w-starting, in response to this particular pack)-.275 E(et)-.11 E
(ackno)100.8 423 Q 2.75(wledgement. In)-.275 F
(general, there is probably considerable po)2.75 E
(wer in \214ne-grained)-.275 E(proposals with only tw)100.8 436 Q 2.75
(ob)-.11 G(its of feedback, indicating that the sender should decrease,)
-2.75 E(maintain, or increase the sending rate or windo)100.8 449 Q 2.75
(ww)-.275 G(hen this pack)-2.75 E(et is ackno)-.11 E(wledged.)-.275 E
(Ho)100.8 462 Q(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H(he po)
.44 E(wer of Quick-Start w)-.275 E(ould be considerably limited if it w)
-.11 E(as restricted to)-.11 E(only tw)100.8 475 Q 2.75(ob)-.11 G
(its of feedback; it seems lik)-2.75 E
(ely that determining the initial sending rate)-.11 E(fundamentally req\
uires more bits of feedback from routers than does the steady-state, pe\
r)100.8 488 Q(-)-.22 E(pack)100.8 501 Q
(et feedback to increase or decrease the sending rate.)-.11 E
(On a more practical le)100.8 527 Q -.165(ve)-.275 G(l, one dif).165 E
(ference between Quick-Start and proposals for per)-.275 E(-pack)-.22 E
(et)-.11 E(feedback is that there are fe)100.8 540 Q
(wer open issues with Quick-Start than there w)-.275 E(ould be with a)
-.11 E(ne)100.8 553 Q 2.75(wc)-.275 G(ongestion control mechanism.)-2.75
E -.165(Fo)5.5 G 2.75(re).165 G
(xample, for a mechanism for requesting a initial)-2.915 E
(sending rate in an underutilized en)100.8 566 Q(vironment, the f)-.44 E
(airness issues of a general congestion)-.11 E(control mechanism go a)
100.8 579 Q -.11(wa)-.165 G 1.43 -.715(y, a).11 H
(nd there is no need for the end nodes to tell the routers the).715 E
(round-trip time and congestion windo)100.8 592 Q 1.43 -.715(w, a)-.275
H 2.75(si).715 G 2.75(sd)-2.75 G
(one in XCP; all that is needed is for the end)-2.75 E
(nodes to report the requested sending rate.)100.8 605 Q -.88(Ta)100.8
631 S(ble 2 pro).88 E(vides a summary of the dif)-.165 E
(ferences between Quick-Start and proposals for per)-.275 E(-)-.22 E
(pack)100.8 644 Q(et congestion control feedback.)-.11 E(Jain/Flo)72 769
Q 201.583(yd/Allman/Sarolahti Section)-.11 F 2.75(A.6. [P)2.75 F
(age 43])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E/F1 11
/Courier@0 SF(Proposals for)391.2 85 Q 66(Quick-Start Per-Packet)246 98
R(Feedback)6.6 E
(+------------------+----------------------+----------------------+)
100.8 111 Q 46.2(Semantics: |)107.4 124 R
(Allowed sending rate | Change in rate/window,)6.6 E 13.2(|p)226.2 137 S
(er connection.)-13.2 E 13.2(|p)33 G(er-packet.)-13.2 E
(+------------------+----------------------+----------------------+)
100.8 150 Q(Relationship to)107.4 163 Q 6.6(|I)19.8 G 6.6(na)-6.6 G 52.8
(ddition. |)-6.6 F(Replacement.)6.6 E(congestion ctrl:)107.4 176 Q 145.2
(||)13.2 G
(+------------------+----------------------+----------------------+)
100.8 189 Q 46.2(Frequency: |)107.4 202 R(Start-up, or after)6.6 E 6.6
(|E)19.8 G(very packet.)-6.6 E 13.2(|a)226.2 215 S 6.6(ni)-13.2 G
(dle period.)-6.6 E(|)33 E
(+------------------+----------------------+----------------------+)
100.8 228 Q 33(Limitations: |)107.4 241 R(Only useful on)6.6 E 6.6(|G)
46.2 G(eneral congestion)-6.6 E 13.2(|u)226.2 254 S
(nderutilized paths.|)-13.2 E(control mechanism.)13.2 E
(+------------------+----------------------+----------------------+)
100.8 267 Q(Input to routers: | Rate request.)107.4 280 Q 6.6(|R)52.8 G
(TT, cwnd, request \(XCP\).)-6.6 E 145.2(||)226.2 293 S
(None \(Anti-ECN\).)-138.6 E
(+------------------+----------------------+----------------------+)
100.8 306 Q(Bits of feedback: | Four bits for)107.4 319 Q 6.6(|Af)52.8 G
(ew bits would)-6.6 E 19.8(|r)226.2 332 S(ate request.)-19.8 E 13.2(|s)
39.6 G(uffice?)-13.2 E
(+------------------+----------------------+----------------------+)
100.8 345 Q(Table 2: Differences between Quick-Start and Proposals for)
114 371 Q(Fine-Grained Per-Packet Feedback.)127.2 384 Q F0 2.75(As)100.8
416 S(eparate question concerns whether mechanisms such as Quick-Start,\
 in combination)-2.75 E
(with HighSpeed TCP and other changes in progress, w)100.8 429 Q
(ould mak)-.11 E 2.75(eas)-.11 G(igni\214cant contrib)-2.75 E(ution)-.22
E(to)100.8 442 Q -.11(wa)-.275 G(rds meeting some of these needs for ne)
.11 E 2.75(wc)-.275 G(ongestion control mechanisms.)-2.75 E(This could)
5.5 E(be vie)100.8 455 Q(wed as a positi)-.275 E .33 -.165(ve s)-.275 H
(tep of meeting some of the current needs with a simple and).165 E
(reasonably deplo)100.8 468 Q(yable mechanism, or alternately)-.11 E
2.75(,a)-.715 G 2.75(san)-2.75 G -2.475 -.165(eg a)-2.75 H(ti).165 E .33
-.165(ve s)-.275 H(tep of unnecessarily).165 E
(delaying more fundamental changes.)100.8 481 Q -.44(Wi)5.5 G
(thout answering this question, we w).44 E(ould note that)-.11 E(our o)
100.8 494 Q(wn approach tends to f)-.275 E -.22(avo)-.11 G 2.75(rt).22 G
(he incremental deplo)-2.75 E(yment of relati)-.11 E -.165(ve)-.275 G
(ly simple).165 E(mechanisms, as long as the simple mechanisms are not \
short-term hacks b)100.8 507 Q(ut mechanisms)-.22 E(that lead the o)
100.8 520 Q -.165(ve)-.165 G
(rall architecture in the fundamentally correct direction.).165 E/F2 11
/Times-Bold@0 SF(A.7.)72 559 Q/F3 13/Times-Bold@0 SF
(The Earlier QuickStart Nonce)5.5 E F0(An earlier v)100.8 585 Q
(ersion of this document included a Request-Appro)-.165 E -.165(ve)-.165
G 2.75(dQ).165 G(uickStart Nonce \(QS)-2.75 E(Nonce\) that w)100.8 598 Q
(as initialized by the sender to a non-zero, `random' eight-bit number)
-.11 E 2.75(,a)-.44 G(long)-2.75 E(with a QS TTL that w)100.8 611 Q
(as initialized to the same v)-.11 E(alue as the TTL in the IP header)
-.275 E 5.5(.T)-.605 G(he)-5.5 E(Request-Appro)100.8 624 Q -.165(ve)
-.165 G 2.75(dQ).165 G(uickStart Nonce w)-2.75 E(ould ha)-.11 E .33
-.165(ve b)-.22 H(een returned by the TCP recei).165 E -.165(ve)-.275 G
2.75(rt).165 G 2.75(ot)-2.75 G(he)-2.75 E
(TCP sender in the Quick-Start Response.)100.8 637 Q 2.75(Ar)5.5 G
(outer could den)-2.75 E 2.75(yt)-.165 G(he Quick-Start request by)-2.75
E -.11(fa)100.8 650 S(iling to decrement the QS TTL \214eld, by zeroing\
 the QS Nonce \214eld, or by deleting the).11 E
(Quick-Start Request from the pack)100.8 663 Q(et header)-.11 E 5.5(.T)
-.605 G(he QS Nonce w)-5.5 E(as included to pro)-.11 E(vide some)-.165 E
(protection ag)100.8 676 Q(ainst brok)-.055 E(en do)-.11 E
(wnstream routers, or ag)-.275 E(ainst misbeha)-.055 E(ving TCP recei)
-.22 E -.165(ve)-.275 G(rs that).165 E
(might be inclined to lie about whether the Rate Request w)100.8 689 Q
(as appro)-.11 E -.165(ve)-.165 G 2.75(d. This).165 F(protection is)2.75
E(no)100.8 702 Q 2.75(wp)-.275 G(ro)-2.75 E
(vided by the use of a random initial v)-.165 E
(alue for the QS TTL \214eld, and by Quick-)-.275 E(Start-capable route\
rs hopefully either deleting the Quick-Start Option or zeroing the QS)
100.8 715 Q(Jain/Flo)72 769 Q 201.583(yd/Allman/Sarolahti Section)-.11 F
2.75(A.7. [P)2.75 F(age 44])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(TTL \214eld when the)100.8 85 Q 2.75(yd)-.165 G(en)-2.75 E 2.75(yar)
-.165 G(equest.)-2.75 E -.44(Wi)100.8 111 S(th the old Request-Appro).44
E -.165(ve)-.165 G 2.75(dQ).165 G
(uickStart Nonce, along with the QS TTL \214eld set to the)-2.75 E
(same v)100.8 124 Q(alue as the TTL \214eld in the IP header)-.275 E
2.75(,t)-.44 G(he Quick-Start Request mechanism w)-2.75 E(ould)-.11 E
(ha)100.8 137 Q .33 -.165(ve b)-.22 H
(een self-terminating; the Quick-Start Request w).165 E
(ould terminate at the \214rst)-.11 E(participating router after a non-\
participating router had been encountered on the path.)100.8 150 Q(This)
5.5 E(minimizes unnecessary o)100.8 163 Q -.165(ve)-.165 G
(rhead incurred by routers because of option processing for the).165 E
(Quick-Start Request.)100.8 176 Q
(In the current speci\214cation, this "self-terminating" property is)5.5
E(pro)100.8 189 Q(vided by Quick-Start-capable routers hopefully either\
 deleting the Quick-Start Option)-.165 E
(or zeroing the Rate Request \214eld when the)100.8 202 Q 2.75(yd)-.165
G(en)-2.75 E 2.75(yar)-.165 G 2.75(equest. Because)-2.75 F(the current)
2.75 E(speci\214cation uses a random initial v)100.8 215 Q
(alue for the QS TTL, Quick-Start-capable routers can')-.275 E(t)-.198 E
(tell if the Quick-Start Request is in)100.8 228 Q -.275(va)-.44 G
(lid because of non-Quick-Start-capable routers).275 E 2.75
(upstream. This)100.8 241 R
(is the cost of using a single \214eld for the QS TTL, instead of tw)
2.75 E 2.75<6f8c>-.11 G(elds, one)-2.75 E
(for the QS TTL and another for a QS-Appro)100.8 254 Q -.165(ve)-.165 G
2.75(dN).165 G(once.)-2.75 E(The Quick-Start Nonce has been resurrected\
 in the current proposal for a Rate-Reduced)100.8 280 Q(Nonce gi)100.8
293 Q -.165(ve)-.275 G 2.75(ni).165 G 2.75(nS)-2.75 G
(ection 3.6. This proposal w)-2.75 E(ould pro)-.11 E
(vide speci\214c protection ag)-.165 E(ainst)-.055 E(recei)100.8 306 Q
-.165(ve)-.275 G(rs lying about whether the rate request w).165 E
(as decremented by routers along the path.)-.11 E
(In this proposal, the Rate-Reduced Nonce w)100.8 319 Q
(ould be reset to a ne)-.11 E 2.75(wr)-.275 G(andom v)-2.75 E
(alue by routers)-.275 E(that appro)100.8 332 Q .33 -.165(ve t)-.165 H
(he request b).165 E(ut decrement the v)-.22 E
(alue of the Rate Request.)-.275 E(Thus, if the original)5.5 E -.275(va)
100.8 345 S
(lue for the Rate-Reduced Nonce is reported back by the recei).275 E
-.165(ve)-.275 G 2.75(rt).165 G 2.75(ot)-2.75 G(he sender)-2.75 E 2.75
(,t)-.44 G(hen it is)-2.75 E(lik)100.8 358 Q
(ely that the Rate Request w)-.11 E
(as not decremented or denied by Quick-Start-capable routers)-.11 E
(along the path.)100.8 371 Q/F1 11/Times-Bold@0 SF(B.)72 410 Q/F2 14
/Times-Bold@0 SF(Quick-Start with DCCP)5.5 E F0(DCCP is a ne)100.8 436 Q
2.75(wt)-.275 G
(ransport protocol for congestion-controlled, unreliable datagrams,)
-2.75 E
(intended for applications such as streaming media, Internet telephon)
100.8 449 Q 1.43 -.715(y, a)-.165 H(nd on-line g).715 E(ames.)-.055 E
(In DCCP)100.8 462 Q 2.75(,t)-1.221 G
(he application has a choice of congestion control mechanisms, with the)
-2.75 E(currently-speci\214ed Congestion Control Identi\214ers \(CCIDs\
\) being CCID 2 for TCP-lik)100.8 475 Q(e)-.11 E(congestion control, an\
d CCID 3 for TFRC, an equation-based form of congestion control.)100.8
488 Q 1.76 -.88(We r)100.8 501 T
(efer the reader to [KHF05] for a more detailed description of DCCP).88
E 2.75(,a)-1.221 G(nd of the)-2.75 E(congestion control mechanisms.)
100.8 514 Q(Because CCID 3 uses a rate-based congestion control mechani\
sm, it raises some ne)100.8 540 Q(w)-.275 E
(issues about the use of Quick-Start with transport protocols.)100.8 553
Q(In this document we don')5.5 E(t)-.198 E
(attempt to specify the use of Quick-Start with DCCP)100.8 566 Q 5.5(.H)
-1.221 G -.275(ow)-5.5 G -2.365 -.275(ev e).275 H .88 -.44(r, w).275 H
2.75(ed).44 G 2.75(od)-2.75 G(iscuss some of the)-2.75 E
(issues that might arise.)100.8 579 Q(In considering the use of Quick-S\
tart with CCID 3 for requesting a higher initial sending)100.8 605 Q
(rate, the follo)100.8 618 Q(wing questions arise: \(1\) ho)-.275 E 2.75
(wd)-.275 G(oes the sender respond if a Quick-Start pack)-2.75 E(et)-.11
E(is dropped; and \(2\) when does the sender determine that there has b\
een no feedback from)100.8 631 Q(the recei)100.8 644 Q -.165(ve)-.275 G
.88 -.44(r, a).165 H(nd reduce the sending rate?).44 E(\(1\) Ho)100.8
670 Q 2.75(wd)-.275 G(oes the sender respond if a Quick-Start pack)-2.75
E(et is dropped:)-.11 E(As in TCP)100.8 683 Q 2.75(,i)-1.221 G 2.75(fa)
-2.75 G 2.75(ni)-2.75 G(nitial Quick-Start pack)-2.75 E
(et is dropped, the CCID 3 sender should re)-.11 E -.165(ve)-.275 G
(rt to).165 E(the congestion control mechanisms it w)100.8 696 Q
(ould ha)-.11 E .33 -.165(ve u)-.22 H
(sed if the Quick-Start request had not).165 E(been appro)100.8 709 Q
-.165(ve)-.165 G(d.).165 E(Jain/Flo)72 769 Q 210.438
(yd/Allman/Sarolahti Section)-.11 F 2.75(B. [P)2.75 F(age 45])-.165 E 0
Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E(\(2\) W\
hen does the sender decide there has been no feedback from the recei)
100.8 85 Q -.165(ve)-.275 G(r:).165 E(Unlik)100.8 98 Q 2.75(eT)-.11 G
(CP)-2.75 E 2.75(,C)-1.221 G(CID 3 does not use ackno)-2.75 E
(wledgements for e)-.275 E -.165(ve)-.275 G(ry pack).165 E(et, or for e)
-.11 E -.165(ve)-.275 G(ry other).165 E(pack)100.8 111 Q 2.75(et. In)
-.11 F(contrast, the CCID 3 recei)2.75 E -.165(ve)-.275 G 2.75(rs).165 G
(ends feedback to the sender roughly once per)-2.75 E(round-trip time.)
100.8 124 Q(In CCID 3, the allo)5.5 E(wed sending rate is halv)-.275 E
(ed if no feedback is recei)-.165 E -.165(ve)-.275 G(d).165 E
(from the recei)100.8 137 Q -.165(ve)-.275 G 2.75(ri).165 G 2.75(na)
-2.75 G 2.75(tl)-2.75 G
(east four round-trip times \(when the sender is sending at least one)
-2.75 E(pack)100.8 150 Q(et e)-.11 E -.165(ve)-.275 G(ry tw).165 E 2.75
(or)-.11 G(ound-trip times\).)-2.75 E
(When a Quick-Start request is used, it w)5.5 E(ould seem)-.11 E
(prudent to use a smaller time interv)100.8 163 Q
(al, e.g., to reduce the sending rate if no feedback is)-.275 E(recei)
100.8 176 Q -.165(ve)-.275 G 2.75(df).165 G(rom the recei)-2.75 E -.165
(ve)-.275 G 2.75(ri).165 G 2.75(na)-2.75 G 2.75(tl)-2.75 G(east tw)-2.75
E 2.75(or)-.11 G(ound-trip times.)-2.75 E
(The question also arises of ho)100.8 202 Q 2.75(wt)-.275 G
(he sending rate should be reduced after a period of no)-2.75 E
(feedback from the recei)100.8 215 Q -.165(ve)-.275 G 3.96 -.605(r. A)
.165 H 2.75(sw).605 G(ith TCP)-2.75 E 2.75(,t)-1.221 G(he def)-2.75 E
(ault CCID 3 response of halving the)-.11 E
(sending rate is not necessarily suf)100.8 228 Q
(\214cient; an alternati)-.275 E .33 -.165(ve i)-.275 H 2.75(st).165 G
2.75(or)-2.75 G(educe the sending rate to the)-2.75 E
(sending rate that w)100.8 241 Q(ould ha)-.11 E .33 -.165(ve b)-.22 H
(een used if no Quick-Start request had been appro).165 E -.165(ve)-.165
G 2.75(d. That).165 F(is, if a CCID 3 sender uses a Quick-Start request\
, special rules might be required to handle)100.8 254 Q(the sender')
100.8 267 Q 2.75(sr)-.605 G
(esponse to a period of no feedback from the recei)-2.75 E -.165(ve)
-.275 G 2.75(rr).165 G -2.475 -.165(eg a)-2.75 H(rding the Quick-).165 E
(Start pack)100.8 280 Q(ets.)-.11 E(Similarly)100.8 306 Q 2.75(,i)-.715
G 2.75(nc)-2.75 G
(onsidering the use of Quick-Start with CCID 3 for requesting a higher)
-2.75 E(sending rate after an idle period, the follo)100.8 319 Q
(wing questions arise: \(1\) what rate does the)-.275 E(sender request;\
 \(2\) what is the response to a loss; and \(3\) when does the sender d\
etermine)100.8 332 Q(that there has been no feedback from the recei)
100.8 345 Q -.165(ve)-.275 G .88 -.44(r, a).165 H
(nd the sending rate must be reduced?).44 E
(\(1\) What rate does the sender request:)100.8 371 Q(As in TCP)100.8
384 Q 2.75(,t)-1.221 G(here is a straightforw)-2.75 E
(ard answer to the rate request that the CCID 3 sender)-.11 E
(should use in requesting a higher sending rate after an idle period.)
100.8 397 Q(The sender kno)5.5 E(ws the)-.275 E(current loss e)100.8 410
Q -.165(ve)-.275 G(nt rate, either from its o).165 E
(wn calculations or from feedback from the recei)-.275 E -.165(ve)-.275
G -.44(r,).165 G(and can determine the sending rate allo)100.8 423 Q
(wed by that loss e)-.275 E -.165(ve)-.275 G(nt rate.).165 E
(This is the upper bound)5.5 E
(on the sending rate that should be requested by the CCID 3 sender)100.8
436 Q 5.5(.A)-.605 G(Quick-Start request)-2.75 E(is useful with CCID 3 \
when the sender is coming out of an idle or underutilized period,)100.8
449 Q(because in standard operation CCID 3 does not allo)100.8 462 Q
2.75(wt)-.275 G(he sender to send more that twice as)-2.75 E -.11(fa)
100.8 475 S(st as the recei).11 E -.165(ve)-.275 G 2.75(rh).165 G
(as reported recei)-2.75 E -.165(ve)-.275 G 2.75(di).165 G 2.75(nt)-2.75
G(he most recent feedback message.)-2.75 E
(\(2\) What is the response to loss:)100.8 501 Q
(The response to the loss of Quick-Start pack)100.8 514 Q
(ets should be to return to the sending rate that)-.11 E -.11(wo)100.8
527 S(uld ha).11 E .33 -.165(ve b)-.22 H
(een used if Quick-Start had not been requested.).165 E(\(3\) When does\
 the sender decide there has been no feedback from the recei)100.8 553 Q
-.165(ve)-.275 G(r:).165 E
(As in the case of the initial sending rate, it w)100.8 566 Q
(ould seem prudent to reduce the sending rate if)-.11 E
(no feedback is recei)100.8 579 Q -.165(ve)-.275 G 2.75(df).165 G
(rom the recei)-2.75 E -.165(ve)-.275 G 2.75(ri).165 G 2.75(na)-2.75 G
2.75(tl)-2.75 G(east tw)-2.75 E 2.75(or)-.11 G(ound-trip times.)-2.75 E
(It seems lik)5.5 E(ely)-.11 E(that in this case, the sending rate shou\
ld be reduced to the sending rate that w)100.8 592 Q(ould ha)-.11 E
-.165(ve)-.22 G(been used if no Quick-Start request had been appro)100.8
605 Q -.165(ve)-.165 G(d.).165 E/F1 11/Times-Bold@0 SF(C.)72 644 Q/F2 14
/Times-Bold@0 SF -.28(Po)5.5 G(ssible Router Algorithm).28 E F0(This sp\
eci\214cation does not tightly de\214ne the algorithm a router uses whe\
n deciding)100.8 670 Q(whether to appro)100.8 683 Q .33 -.165(ve a Q)
-.165 H(uick-Start Rate Request or whether and ho).165 E 2.75(wt)-.275 G
2.75(or)-2.75 G(educe a Rate)-2.75 E 2.75(Request. A)100.8 696 R
(range of algorithms is lik)2.75 E
(ely useful in this space and we consider the algorithm)-.11 E 2.75(ap)
100.8 709 S(articular router uses to be a local polic)-2.75 E 2.75(yd)
-.165 G 2.75(ecision. In)-2.75 F(addition, we belie)2.75 E .33 -.165
(ve t)-.275 H(hat additional).165 E -.165(ex)100.8 722 S
(perimentation with router algorithms is necessary to ha).165 E .33
-.165(ve a s)-.22 H(olid understanding of the).165 E(Jain/Flo)72 769 Q
210.438(yd/Allman/Sarolahti Section)-.11 F 2.75(C. [P)2.75 F(age 46])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(dynamics v)100.8 85 Q(arious algorithms impose.)-.275 E(Ho)5.5 E(we)
-.275 E -.165(ve)-.275 G .88 -.44(r, w).165 H 2.75(ep).44 G(ro)-2.75 E
(vide one particular algorithm in this)-.165 E(appendix as an e)100.8 98
Q(xample and as a frame)-.165 E -.11(wo)-.275 G
(rk for thinking about additional mechanisms.).11 E([SAF05] pro)100.8
124 Q(vides se)-.165 E -.165(ve)-.275 G
(ral algorithms routers can use to consider incoming Rate Requests.).165
E(The decision process in)100.8 137 Q -.22(vo)-.44 G(lv).22 E(es tw)
-.165 E 2.75(oa)-.11 G 2.75(lgorithms. First,)-2.75 F
(the router needs to track the link)2.75 E(utilization o)100.8 150 Q
-.165(ve)-.165 G 2.75(rt).165 G(he recent past.)-2.75 E
(Second, this utilization needs to be updated by the)5.5 E(potential ne)
100.8 163 Q 2.75(wb)-.275 G(andwidth from recent Quick-Start appro)-2.75
E -.275(va)-.165 G(ls, and then compared with the).275 E(router')100.8
176 Q 2.75(sn)-.605 G(otion of when it is underutilized enough to appro)
-2.75 E .33 -.165(ve Q)-.165 H(uick-Start requests \(of some).165 E
(size\).)100.8 189 Q(First, we de\214ne the "peak utilization" estimati\
on technique \(from [SAF05]\).)100.8 215 Q(This)5.5 E
(mechanism records the utilization of the link e)100.8 228 Q -.165(ve)
-.275 G(ry S seconds and stores the most recent N).165 E
(of these measurements.)100.8 241 Q(The utilization is then tak)5.5 E
(en as the highest utilization of the N)-.11 E 2.75(samples. This)100.8
254 R(method, therefore, k)2.75 E(eeps N*S seconds of history)-.11 E 5.5
(.T)-.715 G(his algorithm reacts)-5.5 E
(rapidly to increases in the link utilization.)100.8 267 Q
(In [SAF05] S is set to 0.15 seconds, and)5.5 E -.165(ex)100.8 280 S
(periments use v).165 E(alues for N ranging from 3 to 20.)-.275 E
(Second, we de\214ne the "tar)100.8 306 Q
(get" algorithm for processing incoming Quick-Start Rate)-.198 E
(Requests \(also from [SAF05]\).)100.8 319 Q
(The algorithm relies on kno)5.5 E(wing the bandwidth of the)-.275 E
(outgoing link \(which in man)100.8 332 Q 2.75(yc)-.165 G
(ases can be easily con\214gured\), the utilization of the)-2.75 E
(outgoing link \(from an estimation technique such as gi)100.8 345 Q
-.165(ve)-.275 G 2.75(na).165 G(bo)-2.75 E -.165(ve)-.165 G 2.75(\)a)
.165 G(nd an estimate of the)-2.75 E
(potential bandwidth from recent Quick-Start appro)100.8 358 Q -.275(va)
-.165 G(ls.).275 E -.385(Tr)100.8 384 S
(acking the potential bandwidth from recent Quick-Start appro).385 E
-.275(va)-.165 G(ls is another case where).275 E(local polic)100.8 397 Q
2.75(yd)-.165 G(ictates ho)-2.75 E 2.75(wi)-.275 G 2.75(ts)-2.75 G
(hould be done.)-2.75 E(The simpliest method, outlined in Section 3.4,)
5.5 E(is for the router to k)100.8 410 Q(eep track of the aggre)-.11 E
-.055(ga)-.165 G(te Quick-Start rate requests appro).055 E -.165(ve)
-.165 G 2.75(di).165 G 2.75(nt)-2.75 G(he)-2.75 E(most recent tw)100.8
423 Q 2.75(oo)-.11 G 2.75(rm)-2.75 G(ore time interv)-2.75 E
(als, including the current time interv)-.275 E(al, and to use the)-.275
E(sum of the aggre)100.8 436 Q -.055(ga)-.165 G(te rate requests o).055
E -.165(ve)-.165 G 2.75(rt).165 G(hese time interv)-2.75 E
(als as the estimate of the appro)-.275 E -.165(ve)-.165 G(d).165 E
(Rate Requests.)100.8 449 Q(The e)5.5 E(xperiments in [SAF05] k)-.165 E
(eep track of the aggre)-.11 E -.055(ga)-.165 G(te appro).055 E -.165
(ve)-.165 G 2.75(dR).165 G(ate)-2.75 E(Requests o)100.8 462 Q -.165(ve)
-.165 G 2.75(rt).165 G(he most recent tw)-2.75 E 2.75(ot)-.11 G
(ime interv)-2.75 E(als, for interv)-.275 E(als of 150~msec.)-.275 E
(The tar)100.8 488 Q(get algorithm also depends on a threshold \(qs_thr\
esh\) that is the fraction of the)-.198 E
(outgoing link bandwidth that represents the router')100.8 501 Q 2.75
(sn)-.605 G(otion of "signi\214cantly underutilized".)-2.75 E(If the ut\
ilization, augmented by the potential bandwidth from recent Quick-Start\
 appro)100.8 514 Q -.275(va)-.165 G(ls,).275 E(is abo)100.8 527 Q .33
-.165(ve t)-.165 H
(his threshold then no Quick-Start Rate Requests will be appro).165 E
-.165(ve)-.165 G 2.75(d. If).165 F(the)2.75 E(utilization is less than \
the threshold then Rate Requests will be appro)100.8 540 Q -.165(ve)
-.165 G 2.75(d. The).165 F(Rate)2.75 E
(Requests will be reduced such that the bandwidth allocated w)100.8 553
Q(ould not dri)-.11 E .33 -.165(ve t)-.275 H(he utilization).165 E
(to more than the gi)100.8 566 Q -.165(ve)-.275 G 2.75(nt).165 G 2.75
(hreshold. The)-2.75 F(algorithm is:)2.75 E
(util_bw = bandwidth * utilization;)106.3 592 Q
(util_bw = util_bw + recent_qs_appro)106.3 605 Q -.275(va)-.165 G(ls;)
.275 E(if \(util_bw < \(qs_thresh * bandwidth\)\))106.3 618 Q({)106.3
631 Q(appro)117.3 644 Q -.165(ve)-.165 G 2.75(d=\().165 G
(qs_thresh * bandwidth\) - util_bw;)-2.75 E(if \(rate_request < appro)
117.3 657 Q -.165(ve)-.165 G(d\)).165 E(appro)128.3 670 Q -.165(ve)-.165
G 2.75(d=r).165 G(ate_request;)-2.75 E(appro)117.3 683 Q -.165(ve)-.165
G 2.75(d=r).165 G(ound_do)-2.75 E(wn \(appro)-.275 E -.165(ve)-.165 G
(d\);).165 E(recent_qs_appro)117.3 696 Q -.275(va)-.165 G(ls += appro)
.275 E -.165(ve)-.165 G(d;).165 E(})106.3 709 Q(Jain/Flo)72 769 Q
210.438(yd/Allman/Sarolahti Section)-.11 F 2.75(C. [P)2.75 F(age 47])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(Also note that gi)100.8 85 Q -.165(ve)-.275 G 2.75(nt).165 G
(hat Rate Requests are f)-2.75 E(airly gross the appro)-.11 E -.165(ve)
-.165 G 2.75(dr).165 G(ate should be)-2.75 E(rounded do)100.8 98 Q
(wn when it does not f)-.275 E(all e)-.11 E
(xactly on one of the rates allo)-.165 E(wed by the encoding)-.275 E
(scheme.)100.8 111 Q/F1 14/Times-Bold@0 SF(Normati)72 150 Q .28 -.14
(ve R)-.14 H(efer).14 E(ences)-.252 E F0([RFC793] J. Postel, T)100.8 176
Q(ransmission Control Protocol, RFC 793, September 1981.)-.385 E
([RFC1191] Mogul, J. and S. Deering, P)100.8 202 Q(ath MTU Disco)-.165 E
-.165(ve)-.165 G(ry).165 E 2.75(,R)-.715 G(FC 1191, No)-2.75 E -.165(ve)
-.165 G(mber 1990.).165 E
([RFC2460] S. Deering and R. Hinden. Internet Protocol, V)100.8 228 Q
(ersion 6 \(IPv6\) Speci\214cation.)-1.221 E(RFC 2460, December 1998.)
100.8 241 Q([RFC2581] M. Allman, V)100.8 267 Q 2.75(.P)-1.419 G
(axson, and W)-2.915 E 2.75(.S)-1.012 G(te)-2.75 E -.165(ve)-.275 G
(ns. TCP Congestion Control.).165 E(RFC 2581.)5.5 E(April 1999.)100.8
280 Q([RFC3168] Ramakrishnan, K.K., Flo)100.8 306 Q
(yd, S., and Black, D.)-.11 E(The Addition of Explicit)5.5 E
(Congestion Noti\214cation \(ECN\) to IP)100.8 319 Q 5.5(.R)-1.221 G
(FC 3168, Proposed Standard, September 2001.)-5.5 E
([RFC3390] M. Allman, S. Flo)100.8 345 Q(yd, and C. P)-.11 E
(artridge. Increasing TCP')-.165 E 2.75(sI)-.605 G(nitial W)-2.75 E
(indo)-.44 E 1.43 -.715(w. R)-.275 H(FC).715 E(3390, October 2002.)100.8
358 Q([RFC3742] Flo)100.8 384 Q(yd, S., Limited Slo)-.11 E
(w-Start for TCP with Lar)-.275 E(ge Congestion W)-.198 E(indo)-.44 E
(ws, RFC)-.275 E(3742, Experimental, March 2004.)100.8 397 Q F1(Inf)72
436 Q(ormati)-.35 E .28 -.14(ve R)-.14 H(efer).14 E(ences)-.252 E F0([R\
FC792] J. Postel. Internet Control Message Protocol. RFC 792, September\
 1981.)100.8 462 Q([RFC1812] F)100.8 488 Q 2.75(.B)-.88 G(ak)-2.75 E
(er \(ed.\). Requirements for IP V)-.11 E
(ersion 4 Routers. RFC 1812, June 1995.)-1.221 E([RFC2140] J. T)100.8
514 Q(ouch. TCP Control Block Interdependence.)-.88 E
(RFC 2140. April 1997.)5.5 E
([RFC2205] R. Braden, et al. Resource ReSerV)100.8 540 Q
(ation Protocol \(RSVP\) -- V)-1.221 E(ersion 1)-1.221 E
(Functional Speci\214cation. RFC 2205, September 1997.)100.8 553 Q
([RFC2309] B. Braden, D. Clark, J. Cro)100.8 579 Q(wcroft, B. Da)-.275 E
(vie, S. Deering, D. Estrin, S. Flo)-.22 E(yd, V)-.11 E(.)-1.419 E
(Jacobson, G. Minshall, C. P)100.8 592 Q(artridge, L. Peterson, K.)-.165
E(Ramakrishnan, S. Shenk)5.5 E(er)-.11 E 2.75(,J)-.44 G(.)-2.75 E
(Wrocla)100.8 605 Q
(wski, L. Zhang, Recommendations on Queue Management and Congestion)
-.165 E -1.342 -.814(Av o)100.8 618 T
(idance in the Internet, RFC 2309, April 1998.).814 E([RFC2401] S. K)
100.8 644 Q(ent and R. Atkinson. Security Architecture for the Internet\
 Protocol. RFC)-.275 E(2401, No)100.8 657 Q -.165(ve)-.165 G(mber 1998.)
.165 E([RFC2415] K. Poduri and K. Nichols. Simulation Studies of Increa\
sed Initial TCP W)100.8 683 Q(indo)-.44 E(w)-.275 E
(Size. RFC 2415. September 1998.)100.8 696 Q([RFC2416] T)100.8 722 Q
2.75(.S)-.814 G(hepard and C. P)-2.75 E 2.75(artridge. When)-.165 F
(TCP Starts Up W)2.75 E(ith F)-.44 E(our P)-.165 E(ack)-.165 E(ets Into)
-.11 E(Jain/Flo)72 769 Q 261.775(yd/Allman/Sarolahti [P)-.11 F(age 48])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(Only Three Buf)100.8 85 Q 2.75(fers. RFC)-.275 F(2416. September 1998.)
2.75 E([RFC2463] A. Conta and S. Deering. Internet Control Message Prot\
ocol \(ICMPv6\) for the)100.8 111 Q(Internet Protocol V)100.8 124 Q
(ersion 6 \(IPv6\) Speci\214cation. RFC 2463, December 1998.)-1.221 E
([RFC2488] M. Allman, D. Glo)100.8 150 Q -.165(ve)-.165 G .88 -.44(r, a)
.165 H(nd L. Sanchez. Enhancing TCP Ov).44 E(er Satellite)-.165 E
(Channels using Standard Mechanisms. RFC 2488. January 1999.)100.8 163 Q
([RFC2960] R. Ste)100.8 189 Q -.11(wa)-.275 G
(rt, et. al. Stream Control T).11 E
(ransmission Protocol. RFC 2960, October)-.385 E(2000.)100.8 202 Q
([RFC3124] H. Balakrishnan and S. Seshan. The Congestion Manager)100.8
228 Q 2.75(.R)-.605 G(FC 3124. June)-2.75 E(2001.)100.8 241 Q([RFC3344]\
 C. Perkins \(ed.\). IP Mobility Support for IPv4. RFC 3344, August 200\
2.)100.8 267 Q([RFC3360] S. Flo)100.8 293 Q 2.75(yd. Inappropriate)-.11
F(TCP Resets Considered Harmful.)2.75 E(RFC 3360, August)5.5 E(2002.)
100.8 306 Q([RFC3775] D. Johnson, C. Perkins, and J. Arkk)100.8 332 Q
(o. Mobility Support in IPv6. RFC 3775,)-.11 E(June 2004.)100.8 345 Q
([AHO98] M. Allman, C. Hayes and S. Ostermann. An e)100.8 371 Q -.275
(va)-.275 G(luation of TCP with Lar).275 E(ger)-.198 E(Initial W)100.8
384 Q(indo)-.44 E(ws. A)-.275 E(CM Computer Communication Re)-.44 E(vie)
-.275 E 1.43 -.715(w, J)-.275 H(uly 1998.).715 E
([BW97] G. Brasche and B. W)100.8 410 Q(alk)-.88 E
(e. Concepts, Services and Protocols of the ne)-.11 E 2.75(wG)-.275 G
(SM)-2.75 E(Phase 2+ General P)100.8 423 Q(ack)-.165 E
(et Radio Service. IEEE Communications Mag)-.11 E(azine, pages 94--104,)
-.055 E(August 1997.)100.8 436 Q([FF99] Flo)100.8 462 Q(yd, S., and F)
-.11 E
(all, K., Promoting the Use of End-to-End Congestion Control in the)
-.165 E(Internet, IEEE/A)100.8 475 Q(CM T)-.44 E(ransactions on Netw)
-.385 E(orking, August 1999.)-.11 E([F03] Flo)100.8 501 Q
(yd, S., HighSpeed TCP for Lar)-.11 E(ge Congestion W)-.198 E(indo)-.44
E(ws, RFC 3649, December)-.275 E(2003.)100.8 514 Q([GP)100.8 540 Q
(AR02] A. Gurto)-1.012 E 1.43 -.715(v, M)-.165 H 2.75(.P).715 G
(assoja, O. Aalto, and M. Raitola. Multi-Layer Protocol T)-2.915 E
(racing)-.385 E(in a GPRS Netw)100.8 553 Q
(ork. In Proceedings of the IEEE V)-.11 E(ehicular T)-1.221 E
(echnology Conference \(F)-.77 E(all)-.165 E(VTC2002\), V)100.8 566 Q
(ancouv)-1.221 E(er)-.165 E 2.75(,C)-.44 G(anada, September 2002.)-2.75
E([HKP01] M. Handle)100.8 592 Q 1.43 -.715(y, C)-.165 H 2.75(.K).715 G
(reibich and V)-2.75 E 2.75(.P)-1.419 G(axson, Netw)-2.915 E
(ork Intrusion Detection: Ev)-.11 E(asion,)-.275 E -.385(Tr)100.8 605 S
(af).385 E(\214c Normalization, and End-to-End Protocol Semantics, Proc\
. USENIX Security)-.275 E(Symposium 2001.)100.8 618 Q([Jac88] V)100.8
644 Q 2.75(.J)-1.419 G(acobson, Congestion A)-2.75 E -.22(vo)-.814 G
(idance and Control, A).22 E(CM SIGCOMM)-.44 E
([JD02] Manish Jain, Constantinos Do)100.8 670 Q(vrolis, End-to-End A)
-.165 E -.275(va)-.814 G(ilable Bandwidth:).275 E
(Measurement Methodology)100.8 683 Q 2.75(,D)-.715 G
(ynamics, and Relation with TCP Throughput, SIGCOMM)-2.75 E(2002.)100.8
696 Q([KHR02] Dina Katabi, Mark Handle)100.8 722 Q 1.43 -.715(y, a)-.165
H(nd Charles Rohrs, Internet Congestion Control for).715 E(Jain/Flo)72
769 Q 261.775(yd/Allman/Sarolahti [P)-.11 F(age 49])-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
(Future High Bandwidth-Delay Product En)100.8 85 Q(vironments. A)-.44 E
(CM Sigcomm 2002, August 2002.)-.44 E
(URL "http://ana.lcs.mit.edu/dina/XCP/".)100.8 98 Q([KHF05] E. K)100.8
124 Q(ohler)-.385 E 2.75(,M)-.44 G 2.75(.H)-2.75 G(andle)-2.75 E 1.43
-.715(y, a)-.165 H(nd S. Flo).715 E
(yd, Datagram Congestion Control Protocol)-.11 E
(\(DCCP\), internet draft draft-ietf-dccp-spec-11.txt, w)100.8 137 Q
(ork in progress, March 2005.)-.11 E([K03] S. K)100.8 163 Q(unniyur)
-.165 E 2.75(,")-.44 G
(AntiECN Marking: A Marking Scheme for High Bandwidth Delay)-2.75 E
(Connections", Proceedings, IEEE ICC '03, May 2003.)100.8 176 Q(URL)5.5
E("http://www)100.8 189 Q(.seas.upenn.edu/~kunniyur/".)-.715 E
([KAPS02] Rajesh Krishnan, Mark Allman, Craig P)100.8 215 Q
(artridge, James P)-.165 E 2.75(.G. Sterbenz.)-1.221 F(Explicit)2.75 E
-.385(Tr)100.8 228 S(ansport Error Noti\214cation \(ETEN\) for Error)
.385 E(-Prone W)-.22 E(ireless and Satellite Netw)-.44 E(orks.)-.11 E
-.77(Te)100.8 241 S(chnical Report No. 8333, BBN T).77 E
(echnologies, March 2002.)-.77 E(URL)5.5 E("http://www)100.8 254 Q
(.icir)-.715 E(.or)-.605 E(g/mallman/papers/".)-.198 E
([MAF04] Alberto Medina, Mark Allman, and Sally Flo)100.8 280 Q
(yd, Measuring Interactions)-.11 E(Between T)100.8 293 Q
(ransport Protocols and Middlebox)-.385 E
(es, Internet Measurement Conference 2004,)-.165 E(August 2004.)100.8
306 Q(URL "http://www)5.5 E(.icir)-.715 E(.or)-.605 E(g/tbit/".)-.198 E
([MAF05] Alberto Medina, Mark Allman, and Sally Flo)100.8 332 Q 2.75
(yd. Measuring)-.11 F(the Ev)2.75 E(olution of)-.22 E -.385(Tr)100.8 345
S(ansport Protocols in the Internet.).385 E 1.76 -.88(To a)5.5 H
(ppear in Computer Communications Re).88 E(vie)-.275 E 1.43 -.715(w, A)
-.275 H(pril).715 E(2004.)100.8 358 Q([MaxNet] MaxNet Home P)100.8 384 Q
(age, URL "http://netlab)-.165 E(.caltech.edu/~bartek/maxnet.htm".)-.44
E([PK98] V)100.8 410 Q(enkata N. P)-1.221 E
(admanabhan and Randy H. Katz, TCP F)-.165 E(ast Start: A T)-.165 E
(echnique F)-.77 E(or)-.165 E(Speeding Up W)100.8 423 Q(eb T)-.88 E
(ransfers, IEEE GLOBECOM '98, No)-.385 E -.165(ve)-.165 G(mber 1998.)
.165 E([P00] Joon-Sang P)100.8 449 Q(ark, Bandwidth Disco)-.165 E -.165
(ve)-.165 G(ry of a TCP Connection, report to John).165 E
(Jeidemann, 2000, pri)100.8 462 Q -.275(va)-.275 G(te communication.)
.275 E(Citation for ackno)5.5 E(wledgement purposes only)-.275 E(.)-.715
E([PRAKS02] Craig P)100.8 488 Q
(artridge, Dennis Rockwell, Mark Allman, Rajesh Krishnan, James P)-.165
E(.G.)-1.221 E(Sterbenz. A Swifter Start for TCP)100.8 501 Q 2.75(.T)
-1.221 G(echnical Report No. 8339, BBN T)-3.52 E(echnologies, March)-.77
E 2.75(2002. URL)100.8 514 R("http://www)2.75 E(.icir)-.715 E(.or)-.605
E(g/mallman/papers/".)-.198 E([S02] Ion Stoica, pri)100.8 540 Q -.275
(va)-.275 G(te communication, 2002.).275 E(Citation for ackno)5.5 E
(wledgement purposes)-.275 E(only)100.8 553 Q(.)-.715 E([SAF05] P)100.8
579 Q(asi Sarolahti, Mark Allman, and Sally Flo)-.165 E 2.75(yd. Ev)-.11
F(aluating Quick-Start for TCP)-.275 E(.)-1.221 E
(Under submission, May 2005.)100.8 592 Q(URL "http://www)5.5 E(.icir)
-.715 E(.or)-.605 E(g/\215o)-.198 E(yd/quickstart.html".)-.11 E
([SH02] Srikanth Sundarrajan and John Heidemann.)100.8 618 Q
(Study of TCP Quick Start with NS-2.)5.5 E
(Class Project, December 2002.)100.8 631 Q(Not publically a)5.5 E -.275
(va)-.22 G(ilable; citation for ackno).275 E(wledgement)-.275 E
(purposes only)100.8 644 Q(.)-.715 E([W00] Michael W)100.8 670 Q
(elzl: PTP: Better Feedback for Adapti)-.88 E .33 -.165(ve D)-.275 H
(istrib).165 E(uted Multimedia)-.22 E(Applications on the Internet, IPC\
CC 2000 \(19th IEEE International Performance,)100.8 683 Q(Computing, A\
nd Communications Conference\), Phoenix, Arizona, USA, 20-22 February)
100.8 696 Q 2.75(2000. URL)100.8 709 R
("http://informatik.uibk.ac.at/users/c70370/research/publications/".)
2.75 E(Jain/Flo)72 769 Q 261.775(yd/Allman/Sarolahti [P)-.11 F(age 50])
-.165 E 0 Cg EP
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E
([W03] Michael W)100.8 85 Q(elzl, PMTU-Options: P)-.88 E(ath MTU Disco)
-.165 E -.165(ve)-.165 G(ry Using Options, e).165 E(xpired)-.165 E
(internet-draft draft-welzl-pmtud-options-01.txt, w)100.8 98 Q 2.75
(ork-in-progress. February)-.11 F(2003.)2.75 E([ZPS00] Y)100.8 124 Q
2.75(.Z)-1.419 G(hang, V)-2.75 E 2.75(.P)-1.419 G(axson, and S. Shenk)
-2.915 E(er)-.11 E 5.5(,T)-.44 G(he Stationarity of Internet P)-5.5 E
(ath Properties:)-.165 E(Routing, Loss, and Throughput, A)100.8 137 Q
(CIRI T)-.44 E(echnical Report, May 2000.)-.77 E/F1 14/Times-Bold@0 SF
(IAN)72 176 Q 3.5(AC)-.28 G(onsiderations)-3.5 E F0
(Quick-Start requires an IP Option and a TCP Option.)100.8 202 Q/F2 13
/Times-Bold@0 SF(IP Option)72 241 Q F0
(Quick-Start requires an IP Option Number to be allocated.)100.8 267 Q
(The IP Option w)5.5 E(ould ha)-.11 E .33 -.165(ve a)-.22 H
(copied \215ag of 0, a class \214eld of 00, and the assigned \214v)100.8
280 Q(e-bit option number)-.165 E 5.5(.T)-.605 G(he name of)-5.5 E
(the option w)100.8 293 Q(ould be "QSR - Quick-Start Request", with thi\
s document as the reference)-.11 E(document.)100.8 306 Q F2(TCP Option)
72 345 Q F0
(Quick-Start also requires that a TCP Option Number be allocated.)100.8
371 Q(The Length w)5.5 E(ould be 4,)-.11 E(and the Meaning w)100.8 384 Q
(ould be "Quick-Start Request", with this document as the reference)-.11
E(document.)100.8 397 Q F1 -.7(AU)72 436 S(THORS' ADDRESSES).7 E F0
(Amit Jain)100.8 475 Q(F5 Netw)100.8 488 Q(orks)-.11 E
(Email : a.jain@f5.com)100.8 501 Q(Sally Flo)100.8 527 Q(yd)-.11 E
(Phone: +1 \(510\) 666-2989)100.8 540 Q
(ICIR \(ICSI Center for Internet Research\))100.8 553 Q(Email: \215o)
100.8 566 Q(yd@icir)-.11 E(.or)-.605 E(g)-.198 E(URL: http://www)100.8
579 Q(.icir)-.715 E(.or)-.605 E(g/\215o)-.198 E(yd/)-.11 E(Mark Allman)
100.8 605 Q(ICSI Center for Internet Research)100.8 618 Q
(1947 Center Street, Suite 600)100.8 631 Q(Berk)100.8 644 Q(ele)-.11 E
1.43 -.715(y, C)-.165 H 2.75(A9).715 G(4704-1198)-2.75 E
(Phone: \(440\) 243-7361)100.8 657 Q(Email: mallman@icir)100.8 670 Q
(.or)-.605 E(g)-.198 E(URL: http://www)100.8 683 Q(.icir)-.715 E(.or)
-.605 E(g/mallman/)-.198 E(Jain/Flo)72 769 Q 261.775
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(No)2.75 E -.165(ve)-.165 G(mber 2005).165 E(May 2005)115.955 E -.165
(Pa)100.8 85 S(si Sarolahti).165 E(Nokia Research Center)100.8 98 Q
-1.221(P.)100.8 111 S(O. Box 407)1.221 E(FI-00045 NOKIA GR)100.8 124 Q
(OUP)-.44 E(Finland)100.8 137 Q(Phone: +358 50 4876607)100.8 150 Q
(Email: pasi.sarolahti@iki.\214)100.8 163 Q/F1 14/Times-Bold@0 SF
(Full Copyright Statement)72 202 Q F0(Cop)100.8 228 Q
(yright \(C\) The Internet Society 2005.)-.11 E
(This document is subject to the rights, licenses)5.5 E
(and restrictions contained in BCP 78, and e)100.8 241 Q
(xcept as set forth therein, the authors retain all)-.165 E
(their rights.)100.8 254 Q
(This document and the information contained herein are pro)100.8 280 Q
(vided on an "AS IS" basis and)-.165 E(THE CONTRIB)100.8 293 Q(UT)-.11 E
(OR, THE ORGANIZA)-.198 E(TION HE/SHE REPRESENTS OR IS)-1.221 E
(SPONSORED BY \(IF ANY\), THE INTERNET SOCIETY AND THE INTERNET)100.8
306 Q(ENGINEERING T)100.8 319 Q(ASK FORCE DISCLAIM ALL W)-1.023 E
(ARRANTIES, EXPRESS OR)-1.32 E(IMPLIED, INCLUDING B)100.8 332 Q(UT NO)
-.11 E 2.75(TL)-.44 G(IMITED T)-2.75 E 2.75(OA)-.198 G(NY W)-2.75 E
(ARRANTY THA)-1.32 E 2.75(TT)-1.221 G(HE USE)-2.75 E(OF THE INFORMA)
100.8 345 Q(TION HEREIN WILL NO)-1.221 E 2.75(TI)-.44 G
(NFRINGE ANY RIGHTS OR ANY)-2.75 E(IMPLIED W)100.8 358 Q
(ARRANTIES OF MERCHANT)-1.32 E(ABILITY OR FITNESS FOR A)-1.023 E -1.012
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(Intellectual Pr)72 410 Q(operty)-.252 E F0(The IETF tak)100.8 436 Q
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(alidity or scope of an)-.275 E 2.75(yI)-.165 G(ntellectual Property)
-2.75 E(Rights or other rights that might be claimed to pertain to the \
implementation or use of the)100.8 449 Q
(technology described in this document or the e)100.8 462 Q
(xtent to which an)-.165 E 2.75(yl)-.165 G(icense under such rights)
-2.75 E(might or might not be a)100.8 475 Q -.275(va)-.22 G
(ilable; nor does it represent that it has made an).275 E 2.75(yi)-.165
G(ndependent)-2.75 E(ef)100.8 488 Q(fort to identify an)-.275 E 2.75(ys)
-.165 G(uch rights.)-2.75 E
(Information on the procedures with respect to rights in)5.5 E
(RFC documents can be found in BCP 78 and BCP 79.)100.8 501 Q
(Copies of IPR disclosures made to the IETF Secretariat and an)100.8 527
Q 2.75(ya)-.165 G(ssurances of licenses to)-2.75 E(be made a)100.8 540 Q
-.275(va)-.22 G(ilable, or the result of an attempt made to obtain a ge\
neral license or).275 E(permission for the use of such proprietary righ\
ts by implementers or users of this)100.8 553 Q(speci\214cation can be \
obtained from the IETF on-line IPR repository at)100.8 566 Q(http://www)
100.8 579 Q(.ietf.or)-.715 E(g/ipr)-.198 E(.)-.605 E(The IETF in)100.8
605 Q(vites an)-.44 E 2.75(yi)-.165 G
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(op)-2.75 E(yrights, patents or)-.11 E
(patent applications, or other proprietary rights that may co)100.8 618
Q -.165(ve)-.165 G 2.75(rt).165 G(echnology that may be)-2.75 E
(required to implement this standard.)100.8 631 Q
(Please address the information to the IETF at ietf-)5.5 E(ipr@ietf.or)
100.8 644 Q(g.)-.198 E(Jain/Flo)72 769 Q 261.775(yd/Allman/Sarolahti [P)
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