One document matched: draft-ietf-dccp-ccid2-01.ps

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/F0 10/Courier-Bold@0 SF(Internet Engineering Task Force)72 85 Q 276
(INTERNET-DRAFT Sally)72 98 R(Floyd)6 E 192
(draft-ietf-dccp-ccid2-01.ps Eddie)72 111 R(Kohler)6 E(ICIR)480 124 Q 6
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(or DCCP Congestion Contr)-.35 E(ol ID 2:)-.252 E(TCP-lik)200.696 188 Q
3.5(eC)-.14 G(ongestion Contr)-3.5 E(ol)-.252 E/F2 11/Times-Bold@0 SF
(Status of this Document)72 233 Q/F3 11/Times-Roman@0 SF(This document \
is an Internet-Draft and is in full conformance with all pro)100.8 249.6
Q(visions of Section)-.165 E(10 of [RFC 2026].)100.8 262.6 Q
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.11 E(Internet-Drafts are draft documents v)100.8 314.6 Q
(alid for a maximum of six months and may be)-.275 E
(updated, replaced, or obsoleted by other documents at an)100.8 327.6 Q
2.75(yt)-.165 G(ime. It is inappropriate to use)-2.75 E
(Internet-Drafts as reference material or to cite them other than as "w)
100.8 340.6 Q(ork in progress.")-.11 E
(The list of current Internet-Drafts can be accessed at http://www)100.8
366.6 Q(.ietf.or)-.715 E(g/ietf/1id-)-.198 E(abstracts.txt)100.8 379.6 Q
(The list of Internet-Draft Shado)100.8 405.6 Q 2.75(wD)-.275 G
(irectories can be accessed at)-2.75 E(http://www)100.8 418.6 Q
(.ietf.or)-.715 E(g/shado)-.198 E -.715(w.)-.275 G(html.).715 E F2
(Abstract)267.534 437.6 Q F3(This document contains the pro\214le for C\
ongestion Control Identi\214er 2, TCP-lik)97 460.2 Q(e)-.11 E(Congestio\
n Control, in the Datagram Congestion Control Protocol \(DCCP\) [DCCP].)
97 473.2 Q(DCCP implements a congestion-controlled, unreliable \215o)97
486.2 Q 2.75(wo)-.275 G 2.75(fd)-2.75 G(atagrams suitable for)-2.75 E
(use by applications such as streaming media. The TCP-lik)97 499.2 Q
2.75(eC)-.11 G(ongestion Control CCID)-2.75 E(is used by senders who ar\
e able to adapt to the abrupt changes in the congestion)97 512.2 Q
(windo)97 525.2 Q 2.75(wt)-.275 G(ypical of the AIMD \(Additi)-2.75 E
.33 -.165(ve I)-.275 H(ncrease Multiplicati).165 E .33 -.165(ve D)-.275
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(ongestion Control is particularly useful for senders who)-2.75 E -.11
(wo)97 551.2 S(uld lik).11 E 2.75(et)-.11 G 2.75(ot)-2.75 G(ak)-2.75 E
2.75(ea)-.11 G(dv)-2.75 E(antage of the a)-.275 E -.275(va)-.22 G
(ilable bandwidth in an en).275 E(vironment with)-.44 E
(rapidly changing conditions.)97 564.2 Q .396 -.198(TO B)97 590.2 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-ietf-dccp-ccid2-00.txt:)97 616.2 Q 2.75(*S)
97 642.2 S(aid that the Ackno)-2.75 E(wledgement Number reports the lar)
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(the most recent pack)97 655.2 Q(et, for consistenc)-.11 E 2.75(yw)-.165
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(Ta)239.126 85 S(ble of Contents)1.196 E/F2 10/Times-Roman@0 SF
(1. Introduction)97 123 Q F0 11(......................)3.56 G F2(3)11.5
E(1.1. Usage Scenario)107 135 Q F0 11(....................).52 G F2(3)
11.5 E(1.2. Example Half-Connection)107 147 Q F0 11(................)
12.74 G F2(3)11.5 E(2. Connection Establishment)97 159 Q F0 11
(..................)2.72 G F2(4)11.5 E(3. Congestion Control on Data P)
97 171 Q(ack)-.15 E(ets)-.1 E F0 11(...............)3.95 G F2(4)11.5 E
(4. Ackno)97 183 Q(wledgements)-.25 E F0 11(....................)1.32 G
F2(5)11.5 E(4.1. Congestion Control on Ackno)107 195 Q(wledgements)-.25
E F0 11(............).2 G F2(5)11.5 E(4.1.1. Deri)117 207 Q -.25(va)-.25
G(tion of Ack Ratio Decrease).25 E F0 11(.............)6.18 G F2(6)11.5
E(4.2. Quiescence)107 219 Q F0 11(.....................)3.16 G F2(7)11.5
E(4.3. Ackno)107 231 Q(wledgements of Ackno)-.25 E(wledgements)-.25 E F0
11(............)1.31 G F2(7)11.5 E
(5. Explicit Congestion Noti\214cation)97 243 Q F0 11(................)
5.49 G F2(7)11.5 E(6. Rele)97 255 Q -.25(va)-.25 G
(nt Options and Features).25 E F0 11(................)12.96 G F2(8)11.5
E(7. Application Requirements)97 267 Q F0 11(..................)2.73 G
F2(8)11.5 E(8. Thanks)97 279 Q F0 11(.......................)9.81 G F2
(8)11.5 E(9. References)97 291 Q F0 11(......................)8.58 G F2
(8)11.5 E(10. Authors' Addresses)97 303 Q F0 11(...................)10.1
G F2(8)11.5 E F0(Flo)72 769 Q(yd/K)-.11 E 333.671(ohler [P)-.385 F
(age 2])-.165 E EP
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85 Q/F2 14/Times-Bold@0 SF(Intr)5.5 E(oduction)-.252 E F0(This document\
 contains the pro\214le for Congestion Control Identi\214er 2, TCP-lik)
100.8 101.6 Q(e)-.11 E(Congestion Control, in the Datagram Congestion C\
ontrol Protocol \(DCCP\).)100.8 114.6 Q(DCCP uses Congestion Control Id\
enti\214ers, or CCIDs, to specify the congestion control)100.8 131.2 Q(\
mechanism in use on a half-connection. \(A half-connection might consis\
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(sent from DCCP A to DCCP B, plus ackno)100.8 157.2 Q
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(congestion windo)129.6 264.8 Q 4.18 -.715(w. I)-.275 H 2.75(fb).715 G
(oth half-connections are acti)-2.75 E -.165(ve)-.275 G 2.75(,t).165 G
(he sender')-2.75 E(s)-.605 E(ackno)129.6 277.8 Q
(wledgement of the recei)-.275 E -.165(ve)-.275 G(r').165 E 2.75(sa)
-.605 G(ckno)-2.75 E(wledgements is included in the sender')-.275 E(s)
-.605 E(ackno)129.6 290.8 Q(wledgement of the recei)-.275 E -.165(ve)
-.275 G(r').165 E 2.75(sd)-.605 G(ata pack)-2.75 E 2.75(ets. If)-.11 F
(the re)2.75 E -.165(ve)-.275 G(rse-path half-connection).165 E
(is quiescent, the sender sends a DCCP-DataAck pack)129.6 303.8 Q
(et that includes an)-.11 E(Ackno)129.6 316.8 Q
(wledgement Number in the header)-.275 E(.)-.605 E 13.224(\(6\) The)
100.8 333.4 R(sender estimates round-trip times and calculates a T)2.75
E(imeOut \(T)-.385 E(O\) v)-.198 E(alue much as)-.275 E(the R)129.6
346.4 Q .396 -.198(TO \()-.66 H(Retransmit T).198 E
(imeout\) is calculated in TCP)-.385 E 5.5(.T)-1.221 G(he T)-5.5 E 2.75
(Oi)-.198 G 2.75(su)-2.75 G(sed to determine)-2.75 E(when a ne)129.6
359.4 Q 2.75(wD)-.275 G(CCP-Data pack)-2.75 E
(et can be transmitted when the sender has been limited)-.11 E
(by the congestion windo)129.6 372.4 Q 2.75(wa)-.275 G
(nd no feedback has been recei)-2.75 E -.165(ve)-.275 G 2.75(df).165 G
(rom the recei)-2.75 E -.165(ve)-.275 G -.605(r.).165 G 13.224
(\(7\) Assuming)100.8 389 R
(that the half-connection is ECN capable \(the ECN Capable feature is)
2.75 E(turned on---the def)129.6 402 Q(ault\), each DCCP-Data pack)-.11
E(et is sent as ECN-Capable with either)-.11 E(the ECT\(0\) or the ECT\
\(1\) codepoint set, as described in [ECN NONCE]. The)129.6 415 Q(recei)
129.6 428 Q -.165(ve)-.275 G 2.75(rr).165 G(eturns the sum of recei)
-2.75 E -.165(ve)-.275 G 2.75(dE).165 G(CN nonces via Ack V)-2.75 E
(ector options, allo)-1.221 E(wing)-.275 E
(the sender to probabilistically v)129.6 441 Q(erify that the recei)
-.165 E -.165(ve)-.275 G 2.75(ri).165 G 2.75(sn)-2.75 G(ot misbeha)-2.75
E 2.75(ving. DCCP-)-.22 F(Ack pack)129.6 454 Q(ets from the recei)-.11 E
-.165(ve)-.275 G 2.75(ra).165 G(re also sent as ECN-Capable, b)-2.75 E
(ut there is no need to)-.22 E -.165(ve)129.6 467 S(rify the nonces.)
.165 E/F1 11/Times-Bold@0 SF(2.)72 493 Q/F2 14/Times-Bold@0 SF
(Connection Establishment)5.5 E F0(Use of the Ack V)100.8 509.6 Q
(ector is MAND)-1.221 E -.506 -1.221(AT O)-.44 H 1.43 -.715(RY o)1.221 H
2.75(nC).715 G(CID 2 half-connections, so the sender MUST)-2.75 E
(send a `Change\(Use Ack V)100.8 522.6 Q(ector)-1.221 E 2.75(,1)-.44 G
(\)' option to the recei)-2.75 E -.165(ve)-.275 G 2.75(ra).165 G 2.75
(sp)-2.75 G(art of connection)-2.75 E
(establishment. The sender SHOULD NO)100.8 535.6 Q 2.75(Ts)-.44 G
(end data until it has recei)-2.75 E -.165(ve)-.275 G 2.75(dt).165 G
(he corresponding)-2.75 E(`Con\214rm\(Use Ack V)100.8 548.6 Q(ector)
-1.221 E 2.75(,1)-.44 G(\)' from the recei)-2.75 E -.165(ve)-.275 G
-.605(r.).165 G F1(3.)72 574.6 Q F2(Congestion Contr)5.5 E(ol on Data P)
-.252 E(ack)-.14 E(ets)-.14 E F0
(The data sender uses the congestion windo)100.8 591.2 Q 2.75(wc)-.275 G
(wnd to control the sending of pack)-2.75 E(ets, and)-.11 E
(uses the slo)100.8 604.2 Q
(w-start threshold ssthresh to control adjustments to cwnd.)-.275 E
(These inte)5.5 E(ger)-.165 E(parameters ha)100.8 617.2 Q .33 -.165
(ve u)-.22 H(nits measured in pack).165 E(ets. When halv)-.11 E
(ed, their v)-.165 E(alues are rounded do)-.275 E(wn,)-.275 E -.165(ex)
100.8 630.2 S(cept that neither parameter is e).165 E -.165(ve)-.275 G
2.75(rl).165 G(ess than one.)-2.75 E(The cwnd and ssthresh v)5.5 E
(ariables are)-.275 E(modi\214ed as in TCP)100.8 643.2 Q 5.5(.T)-1.221 G
(he initial windo)-5.5 E 2.75(wi)-.275 G 2.75(sd)-2.75 G
(etermined using the speci\214cation for TCP)-2.75 E 5.5(.T)-1.221 G(he)
-5.5 E(equi)100.8 656.2 Q -.275(va)-.275 G
(lent of a TCP MSS is simply one pack).275 E(et.)-.11 E
(The sender uses the information in Ack V)100.8 672.8 Q
(ectors to infer a lost pack)-1.221 E 2.75(et. Ack)-.11 F -1.221(Ve)2.75
G(ctors)1.221 E -.165(ex)100.8 685.8 S(plicitly declare which pack).165
E(ets ha)-.11 E .33 -.165(ve n)-.22 H(ot yet been recei).165 E -.165(ve)
-.275 G 2.75(d. One).165 F(of these pack)2.75 E(ets, P)-.11 E 2.75(,i)
-1.221 G(s)-2.75 E
(inferred to be lost \(rather than delayed\) when at least NUMDUP)100.8
698.8 Q -.44(AC)-1.012 G 2.75(Kp).44 G(ack)-2.75 E(ets after pack)-.11 E
(et)-.11 E 2.75(Ph)100.8 711.8 S -2.475 -.22(av e)-2.75 H(been ackno)
2.97 E(wledged by the recei)-.275 E -.165(ve)-.275 G 3.96 -.605(r. T)
.165 H(he NUMDUP).605 E -.44(AC)-1.012 G 2.75(Kp).44 G
(arameter equals 3, the)-2.75 E(number of duplicate ackno)100.8 724.8 Q
(wledgements TCP requires to infer a loss.)-.275 E 2.75(Ac)5.5 G
(ongestion e)-2.75 E -.165(ve)-.275 G(nt is).165 E(Flo)72 769 Q(yd/K)
-.11 E 284.171(ohler Section)-.385 F 2.75(3. [P)2.75 F(age 4])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 65.168(-DRAFT Expires:)-1.012 F
(September 2003)2.75 E(March 2003)106.935 E
(de\214ned as one or more pack)100.8 85 Q(ets lost or mark)-.11 E
(ed from a windo)-.11 E 2.75(wo)-.275 G 2.75(fd)-2.75 G 2.75(ata. F)
-2.75 F(or each congestion)-.165 E -2.365 -.275(ev e)100.8 98 T
(nt, cwnd is halv).275 E(ed, then ssthresh is set to the ne)-.165 E 2.75
(wc)-.275 G 2.75(wnd. Cwnd)-2.75 F(is ne)2.75 E -.165(ve)-.275 G 2.75
(rr).165 G(educed belo)-2.75 E(w)-.275 E(one pack)100.8 111 Q(et.)-.11 E
(When cwnd < ssthresh, meaning that the sender is in slo)100.8 127.6 Q
(w-start, the congestion windo)-.275 E 2.75(wi)-.275 G(s)-2.75 E
(increased by one pack)100.8 140.6 Q(et for e)-.11 E -.165(ve)-.275 G
(ry DCCP-Ack pack).165 E(et recei)-.11 E -.165(ve)-.275 G 2.75(da).165 G
(ckno)-2.75 E(wledging a ne)-.275 E(w)-.275 E(DCCP-Data pack)100.8 153.6
Q(et from the sender)-.11 E 5.5(.N)-.605 G
(ote that cwnd is increased by one per DCCP-Ack)-5.5 E(recei)100.8 166.6
Q -.165(ve)-.275 G(d, not by one per pack).165 E(et ackno)-.11 E
(wledged by the DCCP-Ack; this follo)-.275 E(ws TCP')-.275 E(s)-.605 E
(beha)100.8 179.6 Q(vior)-.22 E 5.5(.W)-.605 G
(hen cwnd >= ssthresh, the congestion windo)-5.5 E 2.75(wi)-.275 G 2.75
(si)-2.75 G(ncreased by one pack)-2.75 E(et for)-.11 E -2.365 -.275
(ev e)100.8 192.6 T(ry windo).275 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata ackno)-2.75 E(wledged without lost or mark)-.275 E(ed pack)-.11 E
(ets.)-.11 E(If all of the data pack)100.8 209.2 Q(ets from a windo)-.11
E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata are lost, the sender needs timeouts to kno)-2.75 E(w)-.275 E
(when to send a ne)100.8 222.2 Q 2.75(wd)-.275 G(ata pack)-2.75 E 2.75
(et. The)-.11 F(sender estimates the round-trip time at most once per)
2.75 E(windo)100.8 235.2 Q 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata, and uses the TCP algorithms for maintaining the a)-2.75 E -.165
(ve)-.22 G(rage round-trip time,).165 E(mean de)100.8 248.2 Q
(viation, and timeout v)-.275 E 2.75(alue. Because)-.275 F
(DCCP does not retransmit data, DCCP does)2.75 E(not require TCP')100.8
261.2 Q 2.75(sr)-.605 G(ecommended minimum timeout of one second.)-2.75
E(After a timeout, the)5.5 E(slo)100.8 274.2 Q
(w-start threshold is set to cwnd/2, then cwnd is set to one pack)-.275
E(et, and a ne)-.11 E 2.75(wp)-.275 G(ack)-2.75 E(et is)-.11 E
(transmitted \(thus using up cwnd\).)100.8 287.2 Q(The e)5.5 E
(xponential back)-.165 E(of)-.11 E 2.75(fo)-.275 G 2.75(ft)-2.75 G
(he timer is used e)-2.75 E(xactly as)-.165 E(in TCP)100.8 300.2 Q(.)
-1.221 E/F1 11/Times-Bold@0 SF(4.)72 326.2 Q/F2 14/Times-Bold@0 SF
(Ackno)5.5 E(wledgements)-.14 E F0(This section describes ho)100.8 342.8
Q 2.75(wt)-.275 G(he recei)-2.75 E -.165(ve)-.275 G 2.75(rr).165 G
(eports ackno)-2.75 E(wledgement information back to the)-.275 E(sender)
100.8 355.8 Q 5.5(.D)-.605 G(CCP-Ack pack)-5.5 E(ets from the recei)-.11
E -.165(ve)-.275 G 2.75(rM).165 G(UST include Ack V)-2.75 E
(ector options, as well)-1.221 E(as an Ackno)100.8 368.8 Q
(wledgement Number ackno)-.275 E(wledging the pack)-.275 E
(et with the lar)-.11 E(gest v)-.198 E(alid sequence)-.275 E
(number recei)100.8 381.8 Q -.165(ve)-.275 G 2.75(df).165 G
(rom the sender)-2.75 E 5.5(.\()-.605 G(Note that a pack)-5.5 E
(et is not "recei)-.11 E -.165(ve)-.275 G(d" until its data is).165 E(u\
nder application control, meaning that the data will not be dropped wit\
hout application)100.8 394.8 Q(interv)100.8 407.8 Q
(ention. See Section 5.5 of [DCCP] for further discussion.\))-.165 E
(Ackno)5.5 E(wledgement data in)-.275 E(the Ack V)100.8 420.8 Q
(ector options SHOULD generally co)-1.221 E -.165(ve)-.165 G 2.75(rt)
.165 G(he recei)-2.75 E -.165(ve)-.275 G(r').165 E 2.75(se)-.605 G
(ntire Unackno)-2.75 E(wledged)-.275 E -.44(Wi)100.8 433.8 S(ndo).44 E
1.43 -.715(w, a)-.275 H 2.75(sd).715 G(escribed in [DCCP].)-2.75 E
(The sender speci\214es the Ack Ratio to be used by the recei)100.8
450.4 Q -.165(ve)-.275 G 3.96 -.605(r. I).165 H 2.75(nt).605 G
(he absence of congestion)-2.75 E(on the re)100.8 463.4 Q -.165(ve)-.275
G(rse path, the Ack Ratio is set to tw).165 E 2.75(oi)-.11 G 2.75(ft)
-2.75 G(he congestion windo)-2.75 E 2.75(wi)-.275 G 2.75(st)-2.75 G
(hree or more)-2.75 E(pack)100.8 476.4 Q
(ets, and is set to one otherwise.)-.11 E(The recei)5.5 E -.165(ve)-.275
G 2.75(rs).165 G(ends a DCCP-Ack pack)-2.75 E(et for e)-.11 E -.165(ve)
-.275 G(ry Ack).165 E(Ratio pack)100.8 489.4 Q(ets sent by the sender)
-.11 E(.)-.605 E F1(4.1.)72 515.4 Q/F3 13/Times-Bold@0 SF
(Congestion Contr)5.5 E(ol on Ackno)-.234 E(wledgements)-.13 E F0
(In CCID 2, the ackno)100.8 532 Q(wledgement sub\215o)-.275 E 2.75(wi)
-.275 G 2.75(sl)-2.75 G(oosely congestion-controlled by the Ack)-2.75 E
(Ratio speci\214ed by the sender)100.8 545 Q 5.5(.T)-.605 G(he recei)
-5.5 E -.165(ve)-.275 G 2.75(rs).165 G(ends \(cwnd / Ack Ratio\) ackno)
-2.75 E(wledgement)-.275 E(pack)100.8 558 Q
(ets for each congestion windo)-.11 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata pack)-2.75 E 2.75(ets. W)-.11 F 2.75(en)-.88 G(ote that CCID 2 dif)
-2.75 E(fers from)-.275 E(TCP)100.8 571 Q 2.75(,w)-1.221 G
(hich presently has no congestion control for pure ackno)-2.75 E
(wledgement traf)-.275 E 2.75(\214c. F)-.275 F(or)-.165 E(congestion co\
ntrol for the pure ack stream, DCCP does not try to be TCP-friendly)
100.8 584 Q 2.75(,b)-.715 G(ut just)-2.97 E(tries to a)100.8 597 Q -.22
(vo)-.22 G(id congestion collapse, and to be some).22 E
(what better than TCP)-.275 E 2.75(,i)-1.221 G 2.75(ne)-2.75 G
(xplicitly)-2.915 E
(reducing the ack sending rate in the presence of a high pack)100.8 610
Q(et loss or marking rate on the)-.11 E(return path.)100.8 623 Q
(If DCCP B, the HC-Recei)100.8 639.6 Q -.165(ve)-.275 G .88 -.44(r, i)
.165 H 2.75(sa).44 G(cti)-2.75 E -.165(ve)-.275 G
(ly sending data---it is not quiescent---then required).165 E(ackno)
100.8 652.6 Q(wledgements may be piggyback)-.275 E(ed on DCCP B')-.11 E
2.75(sd)-.605 G(ata pack)-2.75 E(ets. In this situation,)-.11 E
(DCCP B MA)100.8 665.6 Q 2.75(Ys)-1.155 G(end more piggyback)-2.75 E
(ed ackno)-.11 E(wledgements than the Ack Ratio w)-.275 E(ould)-.11 E
(allo)100.8 678.6 Q(w; b)-.275 E(ut it MUST send at least as man)-.22 E
2.75(ya)-.165 G(ckno)-2.75 E(wledgements as the Ack Ratio requires.)
-.275 E(Concei)100.8 691.6 Q -.275(va)-.275 G(bly).275 E 2.75(,t)-.715 G
(he CCID in use for the B-to-A half-connection might limit DCCP B')-2.75
E(s)-.605 E(sending rate to less than the ackno)100.8 704.6 Q
(wledgement rate required for the A-to-B half-)-.275 E 2.75
(connection. DCCP)100.8 717.6 R 2.75(BM)2.75 G(UST follo)-2.75 E 2.75
(wb)-.275 G(oth constraints. In practice, this means that DCCP B)-2.75 E
(Flo)72 769 Q(yd/K)-.11 E 275.921(ohler Section)-.385 F 2.75(4.1. [P)
2.75 F(age 5])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 65.168(-DRAFT Expires:)-1.012 F
(September 2003)2.75 E(March 2003)106.935 E
(will not piggyback data on e)100.8 85 Q -.165(ve)-.275 G(ry ackno).165
E(wledgement.)-.275 E(There are three constraints on the Ack Ratio.)
100.8 101.6 Q(First, it is al)5.5 E -.11(wa)-.11 G(ys an inte).11 E(ger)
-.165 E 5.5(.S)-.605 G(econd, it is)-5.5 E(ne)100.8 114.6 Q -.165(ve)
-.275 G 2.75(rg).165 G(reater than half the congestion windo)-2.75 E
2.75(w\()-.275 G(with fractions rounded up\).)-2.75 E(Third, it is at)
5.5 E(least tw)100.8 127.6 Q 2.75(of)-.11 G(or a congestion windo)-2.75
E 2.75(wo)-.275 G 2.75(ff)-2.75 G(our or more pack)-2.75 E(ets.)-.11 E
(DCCP-Ack pack)100.8 144.2 Q(ets from the recei)-.11 E -.165(ve)-.275 G
2.75(rc).165 G(ontain sequence numbers, so the sender can infer)-2.75 E
(when DCCP-Ack pack)100.8 157.2 Q(ets are lost.)-.11 E
(The sender considers a DCCP-Ack pack)5.5 E(et lost if at least)-.11 E
(NUMDUP)100.8 170.2 Q -.44(AC)-1.012 G 2.75(Kp).44 G(ack)-2.75 E
(ets with higher sequence numbers ha)-.11 E .33 -.165(ve b)-.22 H
(een recei).165 E -.165(ve)-.275 G 2.75(df).165 G(rom the)-2.75 E(recei)
100.8 183.2 Q -.165(ve)-.275 G 1.21 -.605(r. \().165 H(Ag).605 E
(ain, NUMDUP)-.055 E -.44(AC)-1.012 G 2.75(Ke).44 G(quals 3.\))-2.75 E
(If DCCP-Ack pack)5.5 E(ets from the recei)-.11 E -.165(ve)-.275 G 2.75
(ra).165 G(re)-2.75 E(mark)100.8 196.2 Q(ed in the netw)-.11 E
(ork, the sender sees these marks directly)-.11 E(.)-.715 E
(DCCP responds to congestion e)100.8 212.8 Q -.165(ve)-.275 G
(nts on the return path by modifying the Ack Ratio,).165 E
(loosely emulating TCP)100.8 225.8 Q 5.5(.F)-1.221 G
(or each congestion windo)-5.665 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata with lost or mark)-2.75 E(ed DCCP-)-.11 E(Ack pack)100.8 238.8 Q
(ets, the Ack Ratio is doubled, subject to the constraints noted abo)
-.11 E -.165(ve)-.165 G 5.5(.S).165 G(imilarly)-5.5 E 2.75(,i)-.715 G(f)
-2.75 E(the Ack Ratio is R, then for each \(cwnd/\(R^2 - R\)\) congesti\
on windo)100.8 251.8 Q(ws of data with no lost)-.275 E(or mark)100.8
264.8 Q(ed DCCP-Ack pack)-.11 E
(ets, the Ack Ratio is decreased by 1, ag)-.11 E(ain subject to the)
-.055 E(constraints on the Ack Ratio. See the section belo)100.8 277.8 Q
2.75(wf)-.275 G(or the deri)-2.75 E -.275(va)-.275 G 2.75(tion. F).275 F
(or a constant)-.165 E(congestion windo)100.8 290.8 Q 1.43 -.715(w, t)
-.275 H(his gi).715 E -.165(ve)-.275 G 2.75(sa).165 G 2.75(nA)-2.75 G
(ck sending rate that is roughly TCP-friendly)-2.75 E 5.5(.W)-.715 G
2.75(en)-6.38 G(ote)-2.75 E
(that, because the sending rate for the ackno)100.8 303.8 Q
(wledgement pack)-.275 E(ets changes as a function of)-.11 E
(both the Ack Ratio and the congestion windo)100.8 316.8 Q 1.43 -.715
(w, t)-.275 H(he dynamics will be rather comple).715 E(x, and)-.165 E
(this Ack congestion control mechanism is intended only to be v)100.8
329.8 Q(ery roughly TCP-friendly)-.165 E(.)-.715 E
(As a result of the constraints gi)100.8 346.4 Q -.165(ve)-.275 G 2.75
(ne).165 G(arlier in this section, the recei)-2.75 E -.165(ve)-.275 G
2.75(ra).165 G -.11(lwa)-2.75 G(ys sends at least).11 E(one ack pack)
100.8 359.4 Q(et for a congestion windo)-.11 E 2.75(wo)-.275 G 2.75(fo)
-2.75 G(ne pack)-2.75 E(et, and the recei)-.11 E -.165(ve)-.275 G 2.75
(ra).165 G -.11(lwa)-2.75 G(ys sends at).11 E(least tw)100.8 372.4 Q
2.75(oa)-.11 G(ck pack)-2.75 E(ets per windo)-.11 E 2.75(wo)-.275 G 2.75
(fd)-2.75 G(ata otherwise.)-2.75 E(Thus, the recei)5.5 E -.165(ve)-.275
G 2.75(rc).165 G(ould be sending)-2.75 E(tw)100.8 385.4 Q 2.75(oa)-.11 G
(ck pack)-2.75 E(ets per windo)-.11 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata e)-2.75 E -.165(ve)-.275 G 2.75(ni).165 G 2.75(nt)-2.75 G(he f)
-2.75 E(ace of v)-.11 E(ery hea)-.165 E(vy congestion on the)-.22 E(re)
100.8 398.4 Q -.165(ve)-.275 G(rse path.).165 E 1.76 -.88(We w)5.5 H
(ould note, ho).77 E(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H
(hat if congestion is suf).44 E(\214ciently hea)-.275 E(vy that all of)
-.22 E(the ack pack)100.8 411.4 Q(ets are dropped, then the sender f)
-.11 E(alls back on a timeout, and the e)-.11 E(xponential)-.165 E(back)
100.8 424.4 Q(of)-.11 E 2.75(fo)-.275 G 2.75(ft)-2.75 G(he timer)-2.75 E
2.75(,a)-.44 G 2.75(si)-2.75 G 2.75(nT)-2.75 G(CP)-2.75 E 5.5(.T)-1.221
G(hus, if congestion is suf)-5.5 E(\214ciently hea)-.275 E(vy on the re)
-.22 E -.165(ve)-.275 G(rse).165 E
(path, then the sender reduces its sending rate on the forw)100.8 437.4
Q(ard path, which reduces the rate)-.11 E(on the re)100.8 450.4 Q -.165
(ve)-.275 G(rse path as well.).165 E/F1 11/Times-Bold@0 SF 2.75
(4.1.1. Deri)72 476.4 R -.11(va)-.11 G(tion of Ack Ratio Decr).11 E
(ease)-.198 E F0(The congestion a)100.8 493 Q -.22(vo)-.22 G
(idance phase of TCP increases cwnd by one MSS for e).22 E -.165(ve)
-.275 G(ry congestion-).165 E(free windo)100.8 506 Q 6.93 -.715(w. A)
-.275 H(pplying this congestion a).715 E -.22(vo)-.22 G(idance beha).22
E(vior to the ack traf)-.22 E(\214c, this w)-.275 E(ould)-.11 E
(correspond to increasing the number of DCCP-Ack pack)100.8 519 Q
(ets per windo)-.11 E 2.75(wb)-.275 G 2.75(yo)-2.75 G(ne after e)-2.75 E
-.165(ve)-.275 G(ry).165 E(congestion-free windo)100.8 532 Q 2.75(wo)
-.275 G 2.75(fD)-2.75 G(CCP-Ack pack)-2.75 E(ets. W)-.11 E 2.75(ec)-.88
G(annot achie)-2.75 E .33 -.165(ve t)-.275 H(his e).165 E
(xactly using the)-.165 E(Ack Ratio, since the Ack Ratio is an inte)
100.8 545 Q(ger)-.165 E 5.5(.I)-.605 G
(nstead, we must decrease the Ack Ratio by)-5.5 E(one after K windo)
100.8 558 Q(ws ha)-.275 E .33 -.165(ve b)-.22 H
(een sent without a congestion e).165 E -.165(ve)-.275 G(nt on the re)
.165 E -.165(ve)-.275 G(rse path, where).165 E 2.75(Ki)100.8 571 S 2.75
(sc)-2.75 G(hosen so that the long-term number of DCCP-Ack pack)-2.75 E
(ets per congestion windo)-.11 E 2.75(wi)-.275 G(s)-2.75 E
(roughly TCP-friendly)100.8 584 Q 2.75(,f)-.715 G(ollo)-2.75 E
(wing AIMD congestion control.)-.275 E(In CCID 2, K = \(cwnd/\(R^2 - R\
\)\), where R is the current Ack Ratio. This result w)100.8 600.6 Q(as)
-.11 E(calculated as follo)100.8 613.6 Q(ws:)-.275 E(Flo)72 769 Q(yd/K)
-.11 E 267.671(ohler Section)-.385 F 2.75(4.1.1. [P)2.75 F(age 6])-.165
E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 65.168(-DRAFT Expires:)-1.012 F
(September 2003)2.75 E(March 2003)106.935 E/F1 11/Courier@0 SF 6.6(R=A)
180 85 S(ck Ratio = # data packets / ack packets, and)-6.6 E 6.6(W=C)180
98 S(ongestion Window = # data packets / window, so)-6.6 E
(W/R = # ack packets / window.)166.8 111 Q
(Requirement: Increase W/R by 1 per congestion-free window.)127.2 137 Q
(But can only reduce R by increments of one.)127.2 150 Q
(Therefore, find K so that, after K congestion-free windows,)127.2 176 Q
(the adjusted W/R would equal W/\(R-1\).)127.2 189 Q
(\(W/R\) + K = W/\(R-1\), so)127.2 215 Q 6.6(K=W)180 228 S
(/\(R-1\) - W/R = W/\(R^2 - R\).)-6.6 E/F2 11/Times-Bold@0 SF(4.2.)72
260 Q/F3 13/Times-Bold@0 SF(Quiescence)5.5 E F0(This section refers to \
quiescence in the DCCP sense \(see section 8.1 of [DCCP]\): Ho)100.8
276.6 Q(w)-.275 E(does a CCID 2 recei)100.8 289.6 Q -.165(ve)-.275 G
2.75(rd).165 G(etermine that the corresponding sender is not sending an)
-2.75 E 2.75(yd)-.165 G(ata?)-2.75 E(The recei)100.8 306.2 Q -.165(ve)
-.275 G 2.75(rd).165 G
(etects that the sender has gone quiescent after tw)-2.75 E 2.75(oo)-.11
G 2.75(fi)-2.75 G(ts Ack V)-2.75 E(ectors are)-1.221 E(ackno)100.8 319.2
Q(wledged without recei)-.275 E(ving an)-.275 E 2.75(ya)-.165 G
(dditional data. That is, once the sender)-2.75 E(ackno)100.8 332.2 Q
(wledges tw)-.275 E 2.75(oo)-.11 G 2.75(ft)-2.75 G(he recei)-2.75 E
-.165(ve)-.275 G(r').165 E 2.75(sA)-.605 G(ck V)-2.75 E
(ectors without sending additional data, the)-1.221 E(recei)100.8 345.2
Q -.165(ve)-.275 G 2.75(rc).165 G
(an determine that the sender is quiescent.)-2.75 E F2(4.3.)72 371.2 Q
F3(Ackno)5.5 E(wledgements of Ackno)-.13 E(wledgements)-.13 E F0
(The sender)100.8 387.8 Q 2.75(,D)-.44 G(CCP A, must occasionally ackno)
-2.75 E(wledge the recei)-.275 E -.165(ve)-.275 G(r').165 E 2.75(sa)
-.605 G(ckno)-2.75 E(wledgements, so)-.275 E(that the recei)100.8 400.8
Q -.165(ve)-.275 G 2.75(rc).165 G(an free up Ack V)-2.75 E(ector state.)
-1.221 E(The sender can also send ackno)5.5 E(wledgements)-.275 E
(to mak)100.8 413.8 Q 2.75(ec)-.11 G(hanges to the Ack Ratio. W)-2.75 E
2.75(ea)-.88 G(ssume that DCCP A manages the Ack Ratio)-2.75 E(proacti)
100.8 426.8 Q -.165(ve)-.275 G(ly).165 E 2.75(,s)-.715 G
(ending Change\(Ack Ratio\) options whene)-2.75 E -.165(ve)-.275 G 2.75
(rr).165 G(equired. T)-2.75 E 2.75(ol)-.88 G(et the recei)-2.75 E -.165
(ve)-.275 G 2.75(rf).165 G(ree)-2.75 E(Ack V)100.8 439.8 Q
(ector state, DCCP A must occasionally ackno)-1.221 E
(wledge that it has recei)-.275 E -.165(ve)-.275 G 2.75(do).165 G(ne of)
-2.75 E(DCCP B')100.8 452.8 Q 2.75(sa)-.605 G(ckno)-2.75 E
(wledgements. When both half-connections are acti)-.275 E -.165(ve)-.275
G 2.75(,t).165 G(his information is)-2.75 E
(automatically contained in A)100.8 465.8 Q 1.21 -.605('s a)-1.221 H
(ckno).605 E(wledgements to B')-.275 E 2.75(sd)-.605 G
(ata. If the B-to-A half-)-2.75 E(connection goes quiescent, ho)100.8
478.8 Q(we)-.275 E -.165(ve)-.275 G .88 -.44(r, D).165 H
(CCP A must do it proacti).44 E -.165(ve)-.275 G(ly).165 E(.)-.715 E
(In particular)100.8 495.4 Q 2.75(,a)-.44 G 2.75(na)-2.75 G(cti)-2.75 E
.33 -.165(ve s)-.275 H(ender MUST occasionally ackno).165 E
(wledge the recei)-.275 E -.165(ve)-.275 G(r').165 E(s)-.605 E(ackno)
100.8 508.4 Q(wledgements, probably by encapsulating a datagram in a DC\
CP-DataAck pack)-.275 E(et. No)-.11 E(ackno)100.8 521.4 Q
(wledgement options are necessary)-.275 E 2.75(,j)-.715 G(ust the rele)
-2.75 E -.275(va)-.275 G(nt Ackno).275 E(wledgement Number in the)-.275
E(DCCP-DataAck header)100.8 534.4 Q 2.75(.T)-.605 G
(he sender SHOULD ackno)-2.75 E(wledge approximately one of the)-.275 E
(recei)100.8 547.4 Q -.165(ve)-.275 G(r').165 E 2.75(sa)-.605 G(ckno)
-2.75 E(wledgements per congestion windo)-.275 E 1.43 -.715(w. O)-.275 H
2.75(fc).715 G(ourse, the sender')-2.75 E 2.75(sa)-.605 G(pplication)
-2.75 E(might f)100.8 560.4 Q(all silent.)-.11 E
(This is no problem; when neither side is sending data, a sender can w)
5.5 E(ait)-.11 E(arbitrarily long before sending an ack.)100.8 573.4 Q
F2(5.)72 599.4 Q/F4 14/Times-Bold@0 SF
(Explicit Congestion Noti\214cation)5.5 E F0
(ECN may be used with CCID 2.)100.8 616 Q
(If ECN is used, then the ECN Nonce will automatically)5.5 E
(be used for the data pack)100.8 629 Q(ets, follo)-.11 E
(wing the speci\214cation for the ECN Nonce in TCP in)-.275 E
([ECN NONCE]. F)100.8 642 Q(or the data sub\215o)-.165 E 1.43 -.715
(w, t)-.275 H(he sender sets either the ECT\(0\) or ECT\(1\)).715 E
(codepoint on DCCP-Data pack)100.8 655 Q 2.75(ets. Information)-.11 F
(about mark)2.75 E(ed pack)-.11 E(ets is returned in the)-.11 E(Ack V)
100.8 668 Q(ector)-1.221 E 5.5(.B)-.605 G
(ecause the information in the Ack V)-5.5 E
(ector is reliably transferred, DCCP does)-1.221 E
(not need the TCP \215ags of ECN-Echo and Congestion W)100.8 681 Q(indo)
-.44 E 2.75(wR)-.275 G(educed.)-2.75 E -.165(Fo)100.8 697.6 S 2.75(ru)
.165 G(nmark)-2.75 E(ed data pack)-.11 E(ets, the recei)-.11 E -.165(ve)
-.275 G 2.75(rc).165 G(omputes the ECN Nonce as in [ECN NONCE],)-2.75 E
(and returns the ECN Nonce in DCCP-Ack pack)100.8 710.6 Q 2.75(ets. The)
-.11 F(sender uses the ECN Nonce to)2.75 E(protect ag)100.8 723.6 Q
(ainst the accidental or malicious concealment of mark)-.055 E(ed pack)
-.11 E(ets.)-.11 E(Flo)72 769 Q(yd/K)-.11 E 284.171(ohler Section)-.385
F 2.75(5. [P)2.75 F(age 7])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 65.168(-DRAFT Expires:)-1.012 F
(September 2003)2.75 E(March 2003)106.935 E(Because the ack sub\215o)
100.8 85 Q 2.75(wi)-.275 G 2.75(sc)-2.75 G
(ongestion-controlled, ECN can also be used for DCCP-Ack)-2.75 E(pack)
100.8 98 Q 2.75(ets. In)-.11 F(this case we do not mak)2.75 E 2.75(eu)
-.11 G(se of the ECN Nonce, because it w)-2.75 E(ould not be easy)-.11 E
(to pro)100.8 111 Q(vide protection ag)-.165 E
(ainst the concealment of mark)-.055 E(ed ack pack)-.11 E
(ets by the sender)-.11 E 2.75(,a)-.44 G(nd)-2.75 E
(because the sender does not ha)100.8 124 Q .33 -.165(ve a)-.22 H 2.75
(sm).165 G(uch moti)-2.75 E -.275(va)-.275 G
(tion for lying about the mark rate on).275 E(ackno)100.8 137 Q
(wledgements.)-.275 E/F1 11/Times-Bold@0 SF(6.)72 163 Q/F2 14
/Times-Bold@0 SF(Rele)5.5 E -.14(va)-.21 G(nt Options and F).14 E(eatur)
-.35 E(es)-.252 E F0(DCCP')100.8 179.6 Q 2.75(sA)-.605 G(ck V)-2.75 E
(ector option and Ack Ratio and Use Ack V)-1.221 E
(ector features are rele)-1.221 E -.275(va)-.275 G(nt for).275 E
(CCID 2.)100.8 192.6 Q F1(7.)72 218.6 Q F2 -.35(Ap)5.5 G
(plication Requir).35 E(ements)-.252 E F0
(There are no speci\214c application requirements for TCP-lik)100.8
235.2 Q 2.75(eC)-.11 G(ongestion Control.)-2.75 E F1(8.)72 261.2 Q F2
(Thanks)5.5 E F0 1.76 -.88(We t)100.8 277.8 T(hank Mark Handle).88 E
2.75(ya)-.165 G(nd Jitendra P)-2.75 E(adh)-.165 E
(ye for their help in de\214ning CCID 2.)-.055 E F1(9.)72 303.8 Q F2
(Refer)5.5 E(ences)-.252 E F0([DCCP] E. K)100.8 320.4 Q(ohler)-.385 E
2.75(,M)-.44 G 2.75(.H)-2.75 G(andle)-2.75 E 1.43 -.715(y, S)-.165 H
2.75(.F).715 G(lo)-2.75 E(yd, and J. P)-.11 E(adh)-.165 E 2.75
(ye. Datagram)-.055 F(Congestion Control)2.75 E
(Protocol, draft-ietf-dccp-spec-01.txt, w)129.6 333.4 Q
(ork in progress, March 2003.)-.11 E([ECN NONCE] Neil Spring, Da)100.8
350 Q(vid W)-.22 E(etherall, and Da)-.88 E(vid Ely)-.22 E 5.5(.R)-.715 G
(ob)-5.5 E(ust ECN Signaling with)-.22 E
(Nonces, draft-ietf-tsvwg-tcp-nonce-04.txt, w)129.6 363 Q
(ork in progress, October 2002.)-.11 E([RFC 2026] S. Bradner)100.8 379.6
Q 2.75(.T)-.605 G(he Internet Standards Process -- Re)-2.75 E
(vision 3. RFC 2026.)-.275 E([RFC 2861] M. Handle)100.8 396.2 Q 1.43
-.715(y, J)-.165 H 2.75(.P).715 G(adh)-2.915 E(ye, and S. Flo)-.055 E
(yd. TCP Congestion W)-.11 E(indo)-.44 E 2.75(wV)-.275 G(alidation.)
-3.971 E(RFC 2861.)129.6 409.2 Q F1(10.)72 435.2 Q F2 -.7(Au)5.5 G
(thors' Addr).7 E(esses)-.252 E F0(Sally Flo)100.8 454.2 Q(yd <\215o)
-.11 E(yd@icir)-.11 E(.or)-.605 E(g>)-.198 E(Eddie K)100.8 467.2 Q
(ohler <k)-.385 E(ohler@icir)-.11 E(.or)-.605 E(g>)-.198 E
(ICSI Center for Internet Research,)100.8 493.2 Q
(1947 Center Street, Suite 600)100.8 506.2 Q(Berk)100.8 519.2 Q(ele)-.11
E 1.43 -.715(y, C)-.165 H 2.75(A9).715 G(4704.)-2.75 E(Flo)72 769 Q
(yd/K)-.11 E 278.671(ohler Section)-.385 F 2.75(10. [P)2.75 F(age 8])
-.165 E EP
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