One document matched: draft-ietf-rmt-bb-webrc-04.ps

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/F0 10/Courier-Bold@0 SF(Internet Engineering Task Force)72 85 Q(RMT WG)
210 E 198(INTERNET-DRAFT M.)72 98 R(Luby/Digital Fountain)6 E 90
(draft-ietf-rmt-bb-webrc-04.ps V.)72 111 R 6(KG)6 G
(oyal/Digital Fountain)-6 E 6(9D)414 124 S(ecember 2002)-6 E
(Expires: June 2003)396 137 Q/F1 14/Times-Bold@0 SF -2.03 -.91(Wa v)
124.242 162 T 3.5(ea).77 G(nd Equation Based Rate Contr)-3.5 E(ol b)
-.252 E(uilding block)-.28 E/F2 11/Times-Bold@0 SF
(Status of this Document)72 207 Q/F3 11/Times-Roman@0 SF(This document \
is an Internet-Draft and is in full conformance with all pro)72 223.6 Q
(visions of Section 10 of)-.165 E(RFC2026.)72 236.6 Q
(Internet-Drafts are w)72 262.6 Q
(orking documents of the Internet Engineering T)-.11 E(ask F)-.88 E
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(Internet-Drafts are v)72 314.6 Q
(alid for a maximum of six months and may be updated, replaced, or)-.275
E(obsoleted by other documents at an)72 327.6 Q 2.75(yt)-.165 G 2.75
(ime. It)-2.75 F(is inappropriate to use Internet-Drafts as reference)
2.75 E(material or to cite them other than as a "w)72 340.6 Q
(ork in progress".)-.11 E
(The list of current Internet-Drafts can be accessed at http://www)72
366.6 Q(.ietf.or)-.715 E(g/ietf/1id-abstracts.txt)-.198 E 1.76 -.88
(To v)72 392.6 T(ie).88 E 2.75(wt)-.275 G(he list Internet-Draft Shado)
-2.75 E 2.75(wD)-.275 G(irectories, see http://www)-2.75 E(.ietf.or)
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(This document is a product of the IETF RMT WG.)72 418.6 Q
(Comments should be addressed to the)5.5 E(authors, or the WG')72 431.6
Q 2.75(sm)-.605 G(ailing list at rmt@lbl.go)-2.75 E -.715(v.)-.165 G F2
(Abstract)267.534 463.6 Q F3 -1.21 -.88(Wa v)97 486.2 T 2.75(ea).715 G
(nd Equation Based Rate Control pro)-2.75 E
(vides rate and congestion control for data)-.165 E(deli)97 499.2 Q
-.165(ve)-.275 G(ry).165 E 5.5(.W)-.715 G -2.475 -.22(av e)-6.38 H
(and Equation Based Rate Control is speci\214cally designed to support)
2.97 E(protocols using IP multicast.)97 512.2 Q(It pro)5.5 E
(vides multiple-rate, congestion-controlled deli)-.165 E -.165(ve)-.275
G(ry).165 E(to recei)97 525.2 Q -.165(ve)-.275 G(rs, i.e., dif).165 E
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538.2 Q(ets at dif)-.11 E
(ferent rates depending on the bandwidths of their indi)-.275 E
(vidual connections)-.275 E(to the sender and on competing traf)97 551.2
Q(\214c along these connections.)-.275 E -1.21 -.88(Wa v)5.5 H 2.75(ea)
.715 G(nd Equation)-2.75 E
(Based Rate Control requires no feedback from recei)97 564.2 Q -.165(ve)
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(completely recei)97 577.2 Q -.165(ve)-.275 G -.22(r-).165 G(dri).22 E
-.165(ve)-.275 G 2.75(nc).165 G(ongestion control protocol.)-2.75 E
(Thus, it is designed to scale)5.5 E(to potentially massi)97 590.2 Q .33
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(Furthermore, because each indi)97 603.2 Q(vidual recei)-.275 E -.165
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G .88 -.44(r, e).165 H -.165(ve).165 G 2.75(ni).165 G 2.75(nah)-2.75 G
(ighly)-2.75 E(heterogeneous netw)97 642.2 Q
(ork architecture, using a single sender)-.11 E(.)-.605 E(Luby/Go)72 769
Q 339.402(yal [P)-.11 F(age 1])-.165 E EP
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(1. Introduction)97 123 Q F0 11(......................)3.56 G F2(3)11.5
E(2. Rationale)97 135 Q F0 11(.......................).92 G F2(4)11.5 E
(3. Functionality)97 147 Q F0 11(.....................)13.41 G F2(5)11.5
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(..................)12.87 G F2(9)11.5 E(3.2.1. Recei)117 207 Q -.15(ve)
-.25 G 2.5(ri).15 G(nputs and initialization)-2.5 E F0 11(.............)
9.66 G F2(9)11.5 E(3.2.2. Recei)117 219 Q -.15(ve)-.25 G 2.5(rm).15 G
(easurements and calculations)-2.5 E F0 11(...........)7.19 G F2(10)6.5
E(3.2.2.1. A)127 231 Q -.15(ve)-.74 G(rage loss probability).15 E F0 11
(..............)13.07 G F2(10)6.5 E(3.2.2.2. A)127 243 Q -.15(ve)-.74 G
(rage round-trip time).15 E F0 11(...............).44 G F2(12)6.5 E
(3.2.2.3. Rate Equation)127 255 Q F0 11(.................)12.31 G F2(12)
6.5 E(3.2.2.4. Epochs)127 267 Q F0 11(...................)12.31 G F2(12)
6.5 E(3.2.2.5. A)127 279 Q -.15(ve)-.74 G(rage reception rate).15 E F0
11(...............)6.57 G F2(13)6.5 E(3.2.2.6. Slo)127 291 Q 2.5(ws)-.25
G(tart)-2.5 E F0 11(...................)1.72 G F2(14)6.5 E(3.2.2.7. T)
127 303 Q(ar)-.8 E(get rate)-.18 E F0 11(..................)12.89 G F2
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G F2(15)6.5 E(3.2.3.4. Loss e)127 363 Q -.15(ve)-.25 G(nt).15 E F0 11
(..................)12.85 G F2(15)6.5 E(3.2.3.5. Epoch change)127 375 Q
F0 11(.................)12.88 G F2(16)6.5 E(3.2.3.6. Join the ne)127 387
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(3.2.3.7. Join timeout)127 399 Q F0 11(..................)5.77 G F2(17)
6.5 E(3.2.3.8. Exceptional timeouts)127 411 Q F0 11(...............)
12.03 G F2(17)6.5 E(4. Applicability Statement)97 423 Q F0 11
(..................)12.72 G F2(17)6.5 E(4.1. En)107 435 Q
(vironmental Requirements and Considerations)-.4 E F0 11(..........)3.97
G F2(17)6.5 E(5. P)97 447 Q(ack)-.15 E(et Header Fields)-.1 E F0 11
(...................)9.52 G F2(19)6.5 E(5.1. Short F)107 459 Q
(ormat Congestion Control Information)-.15 E F0 11(...........)2.45 G F2
(19)6.5 E(5.2. Long F)107 471 Q(ormat Congestion Control Information)
-.15 E F0 11(...........)3.01 G F2(20)6.5 E
(6. Requirements From Other Building Blocks)97 483 Q F0 11
(.............)3.97 G F2(21)6.5 E(7. Security Considerations)97 495 Q F0
11(..................)12.17 G F2(21)6.5 E(8. IAN)97 507 Q 2.5(AC)-.35 G
(onsiderations)-2.5 E F0 11(...................)7.11 G F2(22)6.5 E
(9. Intellectual Property Issues)97 519 Q F0 11(.................)12.88
G F2(22)6.5 E(10. References)97 531 Q F0 11(......................)3.58
G F2(22)6.5 E(11. Authors' Addresses)97 543 Q F0 11(...................)
10.1 G F2(23)6.5 E(12. Full Cop)97 555 Q(yright Statement)-.1 E F0 11
(..................)1.42 G F2(24)6.5 E F0(Luby/Go)72 769 Q 339.402
(yal [P)-.11 F(age 2])-.165 E EP
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(This document speci\214es W)72 101.6 Q -2.475 -.22(av e)-.88 H
(and Equation Based Rate Control \(WEBRC\).)2.97 E(WEBRC is a)5.5 E
(congestion control b)72 114.6 Q
(uilding block that is designed to be massi)-.22 E -.165(ve)-.275 G
(ly scalable when used with the IP).165 E(multicast netw)72 127.6 Q
(ork service.)-.11 E
(WEBRC is also suitable as the basis for unicast congestion control,)5.5
E -.22(bu)72 140.6 S 2.75(tt).22 G
(his is outside the scope of this document.)-2.75 E
(WEBRC is designed to compete f)5.5 E(airly with TCP)-.11 E
(and similar congestion-controlled sessions.)72 153.6 Q
(WEBRC can be used as a congestion control protocol)5.5 E(for an)72
166.6 Q 2.75(yt)-.165 G(ype of data deli)-2.75 E -.165(ve)-.275 G(ry)
.165 E 2.75(,i)-.715 G(ncluding reliable content deli)-2.75 E -.165(ve)
-.275 G(ry and streaming deli).165 E -.165(ve)-.275 G(ry).165 E(.)-.715
E(WEBRC is a recei)72 192.6 Q -.165(ve)-.275 G -.22(r-).165 G(dri).22 E
-.165(ve)-.275 G 2.75(nc).165 G
(ongestion control protocol in the spirit of [3] and [18]. This means)
-2.75 E(that all measurements and decisions to raise or lo)72 205.6 Q
(wer the reception rate are made by each)-.275 E(indi)72 218.6 Q
(vidual recei)-.275 E -.165(ve)-.275 G .88 -.44(r, a).165 H
(nd these decisions are acted upon by sending join and lea).44 E .33
-.165(ve m)-.22 H(essages for).165 E(channels to the netw)72 231.6 Q
2.75(ork. A)-.11 F(recei)2.75 E -.165(ve)-.275 G 2.75(ru).165 G
(sing WEBRC adjusts its reception rate without re)-2.75 E -.055(ga)-.165
G(rd for).055 E(other concerns such as reliability)72 244.6 Q 5.5(.T)
-.715 G(his is dif)-5.5 E(ferent from TCP)-.275 E 2.75(,w)-1.221 G
(here the congestion control)-2.75 E
(protocol and the reliability protocol are intricately interw)72 257.6 Q
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(es the same basic equation-based approach as TFRC [7]. In particular)
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G 2.75(rm).165 G(easures parameters that are plugged into a TCP-lik)
-2.75 E 2.75(ee)-.11 G(quation to compute the recei)-2.75 E -.165(ve)
-.275 G(r).165 E(tar)72 309.6 Q
(get reception rate, and adjusts its reception rate up and do)-.198 E
(wn to closely approximate the tar)-.275 E(get)-.198 E(reception rate.)
72 322.6 Q(The sender sends pack)5.5 E
(ets to multiple channels; one channel is called the base)-.11 E
(channel and the remaining channels are called w)72 335.6 Q -2.475 -.22
(av e)-.11 H 2.75(channels. Each)2.97 F -.11(wa)2.75 G .33 -.165(ve c)
-.11 H(hannel follo).165 E(ws the)-.275 E(same pattern of pack)72 348.6
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G(qually spaced interv)-2.75 E(als of time.)-.275 E(The)5.5 E
(pattern of each w)72 361.6 Q -2.475 -.22(av e)-.11 H(is that it starts\
 at a high rate that decreases gradually and continually o)2.97 E -.165
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(ncreases its reception)-2.75 E(rate by joining the ne)72 387.6 Q(xt w)
-.165 E -2.475 -.22(av e)-.11 H(channel earlier in the descent of the w)
2.97 E -2.475 -.22(av e)-.11 H(than it joined the pre)2.97 E(vious)-.275
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-.275 E -2.475 -.22(av e)-.11 H(channel.)2.97 E(The w)72 439.6 Q -2.475
-.22(av e)-.11 H(channels are ordered at each point in time from a lo)
2.97 E(west layer to a highest layer)-.275 E 5.5(.A)-.605 G(t)-5.5 E
(each point in time, the lo)72 452.6 Q(west layer is the w)-.275 E
-2.475 -.22(av e)-.11 H
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(channel)2.97 E(is at which layer changes dynamically o)72 491.6 Q -.165
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(addition to being joined to the base channel,)2.75 E
(at each point in time a recei)72 504.6 Q -.165(ve)-.275 G 2.75(ri).165
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(et of layers starting at the lo).165 E(west layer)-.275 E
(and proceeding to)72 517.6 Q -.11(wa)-.275 G(rds the highest.).11 E
(WEBRC introduces a natural notion of a multicast round-trip time \(MR)
72 543.6 Q 2.75(TT\). An)-.66 F(MR)2.75 E(TT is)-.66 E(measured indi)72
556.6 Q(vidually by each recei)-.275 E -.165(ve)-.275 G 2.75(ra).165 G
(nd a)-2.75 E -.165(ve)-.22 G(raged as a substitute for con).165 E -.165
(ve)-.44 G(ntional unicast).165 E(round-trip time \(R)72 569.6 Q 2.75
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(the throughput of a TCP session depends strongly on R)2.75 E(TT)-.66 E
(,)-.814 E(ha)72 582.6 Q(ving some measure of R)-.22 E
(TT is essential in making the WEBRC equation-based rate control)-.66 E
(protocol `)72 595.6 Q(`TCP-friendly)-.814 E -.77(.')-.715 G 5.5('T)
-.044 G(he use of the MR)-5.5 E
(TT also helps to coordinate and equalize the)-.66 E
(reception rates of proximate recei)72 608.6 Q -.165(ve)-.275 G
(rs joined to a session behind a bottleneck link.).165 E(This implies)
5.5 E(that pack)72 621.6 Q(ets for the session that \215o)-.11 E 2.75
(wt)-.275 G(hrough the bottleneck link are on a)-2.75 E -.165(ve)-.22 G
(rage sent to almost all).165 E(do)72 634.6 Q(wnstream recei)-.275 E
-.165(ve)-.275 G(rs, and thus the ef).165 E
(\214ciencies of multicast are realized.)-.275 E(Furthermore, WEBRC)5.5
E(is designed to be massi)72 647.6 Q -.165(ve)-.275 G
(ly scalable in the sense that the sender is insensiti).165 E .33 -.165
(ve t)-.275 H 2.75(ot).165 G(he number of)-2.75 E(recei)72 660.6 Q -.165
(ve)-.275 G(rs joined to a multicast session.).165 E
(WEBRC is designed for applications that use a \214x)72 686.6 Q(ed pack)
-.165 E(et size and v)-.11 E(ary their pack)-.275 E(et reception)-.11 E
(rates in response to congestion.)72 699.6 Q
(WEBRC is designed to be reasonably f)5.5 E(air when competing for)-.11
E(bandwidth with TCP \215o)72 712.6 Q(ws, where a \215o)-.275 E 2.75(wi)
-.275 G 2.75(s`)-2.75 G(`reasonably f)-3.564 E(air')-.11 E 2.75('i)-.814
G 2.75(fi)-2.75 G(ts reception rate is generally)-2.75 E(within a f)72
725.6 Q(actor of tw)-.11 E 2.75(oo)-.11 G 2.75(ft)-2.75 G
(he reception rate of a TCP \215o)-2.75 E 2.75(wu)-.275 G
(nder the same conditions.)-2.75 E(Ho)5.5 E(we)-.275 E -.165(ve)-.275 G
(r).165 E(Luby/Go)72 769 Q 289.902(yal Section)-.11 F 2.75(1. [P)2.75 F
(age 3])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E(WEBRC has a much lo)72 85 Q
(wer v)-.275 E(ariation of throughput o)-.275 E -.165(ve)-.165 G 2.75
(rt).165 G(ime compared to TCP)-2.75 E 2.75(,w)-1.221 G(hich mak)-2.75 E
(es it)-.11 E(more suitable for applications such as telephon)72 98 Q
2.75(yo)-.165 G 2.75(rs)-2.75 G(treaming media where a relati)-2.75 E
-.165(ve)-.275 G(ly smooth).165 E(rate is of importance.)72 111 Q
(The penalty of ha)5.5 E
(ving smoother throughput than TCP while competing)-.22 E -.11(fa)72 124
S(irly for bandwidth is that WEBRC responds more slo).11 E
(wly than TCP to changes in a)-.275 E -.275(va)-.22 G(ilable).275 E
(bandwidth.)72 137 Q(The recei)72 163 Q -.165(ve)-.275 G 2.75(rm).165 G
(easures and performs the calculation of congestion control parameters \
\(e.g., the)-2.75 E -2.475 -.22(av e)72 176 T(rage loss probability).22
E 2.75(,t)-.715 G(he a)-2.75 E -.165(ve)-.22 G(rage MR).165 E
(TT\) and mak)-.66 E(es decisions on ho)-.11 E 2.75(wt)-.275 G 2.75(oi)
-2.75 G(ncrease or decrease)-2.75 E(its rate based on these parameters.)
72 189 Q(The recei)5.5 E -.165(ve)-.275 G -.22(r-).165 G
(based approach is well suited to an application).22 E
(where the sender is handling man)72 202 Q 2.75(yc)-.165 G
(oncurrent connections and therefore WEBRC is suitable as a)-2.75 E -.22
(bu)72 215 S(ilding block for multicast congestion control.).22 E
(The paper [15] and technical report [14] pro)72 241 Q
(vide much of the rationale and intuition for the)-.165 E
(WEBRC design and describe some preliminary simulations.)72 254 Q
(This document describes a b)72 280 Q
(uilding block as de\214ned in RFC3048 [19]. This document describes a)
-.22 E(congestion control b)72 293 Q(uilding block that conforms to RFC\
2357 [16]. This document is a product of)-.22 E
(the IETF RMT WG and follo)72 306 Q(ws the general guidelines pro)-.275
E(vided in RFC3269 [9].)-.165 E(The k)5.5 E .33 -.165(ey w)-.11 H(ords)
.055 E("MUST", "MUST NO)72 319 Q(T", "REQ)-.44 E
(UIRED", "SHALL", "SHALL NO)-.11 E(T", "SHOULD", "SHOULD)-.44 E(NO)72
332 Q(T", "RECOMMENDED", "MA)-.44 E(Y", and "OPTION)-1.155 E
(AL" in this document are to be interpreted)-.385 E
(as described in RFC2119 [2].)72 345 Q/F1 11/Times-Bold@0 SF(2.)72 374.6
Q/F2 14/Times-Bold@0 SF(Rationale)5.5 E F0(WEBRC pro)72 391.2 Q
(vides congestion control for massi)-.165 E -.165(ve)-.275 G
(ly scalable protocols using the IP multicast).165 E(netw)72 404.2 Q
(ork service.)-.11 E(The congestion control that WEBRC pro)5.5 E
(vides is common to a v)-.165 E(ariety of)-.275 E
(applications, including reliable content deli)72 417.2 Q -.165(ve)-.275
G(ry and streaming applications.).165 E(WEBRC is designed to pro)72
443.2 Q(vide congestion control for all pack)-.165 E
(ets that are sent to a session.)-.11 E(A)5.5 E(session comprises multi\
ple channels originating at a single sender that are used for some peri\
od)72 456.2 Q(of time to carry pack)72 469.2 Q(ets pertaining to the tr\
ansmission of one or more objects that can be of)-.11 E
(interest to recei)72 482.2 Q -.165(ve)-.275 G 2.75(rs. The).165 F(logi\
c behind de\214ning a session as originating from a single sender is)
2.75 E(that this is the right granularity to re)72 495.2 Q(gulate pack)
-.165 E(et traf)-.11 E(\214c via congestion control.)-.275 E
(The rationale for)5.5 E(pro)72 508.2 Q(viding congestion control that \
uses multiple channels within the same session is that this)-.165 E
(allo)72 521.2 Q
(ws the data on the channels to be layered, which in turn allo)-.275 E
(ws each recei)-.275 E -.165(ve)-.275 G 2.75(rt).165 G 2.75(oc)-2.75 G
(ontrol its)-2.75 E(reception rate by joining and lea)72 534.2 Q
(ving channels during its participation in the session.)-.22 E
(There are)5.5 E(adv)72 547.2 Q(antages to layered data for streaming, \
where the most important data can be sent to the lo)-.275 E(wer)-.275 E
(layers and incrementally v)72 560.2 Q
(aluable data to the higher layers.)-.275 E -.165(Fo)5.5 G 2.75(rr).165
G(eliable content deli)-2.75 E -.165(ve)-.275 G(ry).165 E 2.75(,a)-.715
G(s)-2.75 E(described in [12], an application can send in pack)72 573.2
Q(ets encoded data generated from an object in)-.11 E(such a w)72 586.2
Q(ay that the arri)-.11 E -.275(va)-.275 G 2.75(lo).275 G 2.75(fe)-2.75
G(nough pack)-2.75 E(ets by a recei)-.11 E -.165(ve)-.275 G 2.75(ri).165
G 2.75(ss)-2.75 G(uf)-2.75 E(\214cient to reliably reconstruct the)-.275
E(original object.)72 599.2 Q 2.75(Ap)5.5 G(rimary adv)-2.75 E
(antage of WEBRC is that each recei)-.275 E -.165(ve)-.275 G 2.75(rc)
.165 G(ontrols it reception rate)-2.75 E(independent of other recei)72
612.2 Q -.165(ve)-.275 G 2.75(rs. Thus,).165 F(for e)2.75 E
(xample, a recei)-.165 E -.165(ve)-.275 G 2.75(rw).165 G(ith a slo)-2.75
E 2.75(wc)-.275 G(onnection to the)-2.75 E(sender does not slo)72 625.2
Q 2.75(wd)-.275 G -.275(ow)-2.75 G 2.75(nt).275 G(he recei)-2.75 E -.165
(ve)-.275 G(rs with f).165 E(aster connections.)-.11 E
(There are coding techniques that pro)72 651.2 Q(vide massi)-.165 E
-.165(ve)-.275 G(ly scalable reliability and asynchronous deli).165 E
-.165(ve)-.275 G(ry).165 E(which are compatible with WEBRC, e.g., as de\
scribed in [10]. When combined the result is a)72 664.2 Q(massi)72 677.2
Q -.165(ve)-.275 G(ly scalable, reliable, asynchronous content deli).165
E -.165(ve)-.275 G(ry protocol that is netw).165 E(ork friendly)-.11 E
(.)-.715 E(WEBRC also pro)72 690.2 Q
(vides congestion control that is suitable for streaming applications.)
-.165 E(WEBRC a)72 716.2 Q -.22(vo)-.22 G
(ids using techniques that are not massi).22 E -.165(ve)-.275 G
(ly scalable.).165 E -.165(Fo)5.5 G 2.75(re).165 G
(xample, WEBRC does not)-2.915 E(Luby/Go)72 769 Q 289.902(yal Section)
-.11 F 2.75(2. [P)2.75 F(age 4])-.165 E EP
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(June 2003)2.75 E(December 2002)103.888 E(pro)72 85 Q(vide an)-.165 E
2.75(ym)-.165 G(echanisms for sending information from recei)-2.75 E
-.165(ve)-.275 G(rs to senders, although this does not).165 E(rule out \
protocols that both use WEBRC and that send information from recei)72 98
Q -.165(ve)-.275 G(rs to senders.).165 E(WEBRC pro)72 124 Q
(vides congestion control that can be tuned for dif)-.165 E
(ferent applications that may ha)-.275 E -.165(ve)-.22 G(dif)72 137 Q
(fering application requirements. F)-.275 E(or e)-.165 E
(xample, a content deli)-.165 E -.165(ve)-.275 G
(ry protocol may aggressi).165 E -.165(ve)-.275 G(ly).165 E(stri)72 150
Q .33 -.165(ve t)-.275 H 2.75(ou).165 G(se all a)-2.75 E -.275(va)-.22 G
(ilable bandwidth between recei).275 E -.165(ve)-.275 G
(rs and the sender).165 E 2.75(,a)-.44 G(nd thus to maintain)-2.75 E
-.11(fa)72 163 S(irness it must drastically reduce its rate when there \
is competing traf).11 E 2.75(\214c. On)-.275 F(the other hand, a)2.75 E
(streaming deli)72 176 Q -.165(ve)-.275 G(ry protocol may stri).165 E
.33 -.165(ve t)-.275 H 2.75(om).165 G
(aintain a constant rate instead of trying to use all)-2.75 E -.22(av)72
189 S(ailable bandwidth, and thus it may not reduce its rate as f)-.055
E(ast when there is competing traf)-.11 E(\214c.)-.275 E
(WEBRC does not pro)72 215 Q(vide an)-.165 E 2.75(ys)-.165 G(upport be)
-2.75 E(yond congestion control, and thus WEBRC is to be)-.165 E
(combined with other b)72 228 Q(uilding blocks to pro)-.22 E
(vide a complete protocol instantiation.)-.165 E -.165(Fo)5.5 G 2.75(re)
.165 G(xample,)-2.915 E(WEBRC does not pro)72 241 Q(vide an)-.165 E 2.75
(ym)-.165 G(eans that can be used to identify which session each recei)
-2.75 E -.165(ve)-.275 G(d).165 E(pack)72 254 Q(et belongs to.)-.11 E
(As another e)5.5 E(xample, WEBRC does not pro)-.165 E
(vide support for identifying which)-.165 E(object each pack)72 267 Q
(et is carrying information about.)-.11 E/F1 11/Times-Bold@0 SF(3.)72
309.6 Q/F2 14/Times-Bold@0 SF(Functionality)5.5 E F0 2.75(AW)72 326.2 S
(EBRC session comprises a logically related set of channels originating\
 from a single sender)-2.75 E
(that are used for some period of time to carry data pack)72 339.2 Q
(ets with a header carrying WEBRC)-.11 E
(Congestion Control Information.)72 352.2 Q(When pack)5.5 E
(ets are recei)-.11 E -.165(ve)-.275 G(d, the).165 E 2.75(ya)-.165 G
(re \214rst check)-2.75 E(ed to see that)-.11 E(the)72 365.2 Q 2.75(yb)
-.165 G(elong to the appropriate session before WEBRC is applied.)-2.75
E 2.75(As)5.5 G(ession label de\214ned by a)-2.75 E
(protocol instantiation may be carried in each pack)72 378.2 Q
(et to identify to which session the pack)-.11 E(et)-.11 E 2.75
(belongs. F)72 391.2 R(or e)-.165 E(xample, if LCT [11] is being used w\
ith the session, then the sender IP address)-.165 E(together with the T)
72 404.2 Q(ransport Session Identi\214er supported by LCT w)-.385 E
(ould be used to determine)-.11 E(which session a recei)72 417.2 Q -.165
(ve)-.275 G 2.75(dp).165 G(ack)-2.75 E(et belongs to.)-.11 E
(The particular details of ho)5.5 E 2.75(wt)-.275 G(his \214ltering is)
-2.75 E(performed it outside the scope of this document.)72 430.2 Q
(In the remainder of this document, references to)5.5 E(channels are al)
72 443.2 Q -.11(wa)-.11 G(ys within the scope of a single session.).11 E
2.75(Ac)72 469.2 S(hannel can be uniquely identi\214ed at the netw)-2.75
E(ork layer by a \(sender IP address, multicast group)-.11 E
(address\) pair)72 482.2 Q 2.75(,a)-.44 G
(nd this is the address to which the recei)-2.75 E -.165(ve)-.275 G 2.75
(rs).165 G(ends messages to join and lea)-2.75 E .33 -.165(ve t)-.22 H
(he).165 E 2.75(channel. The)72 495.2 R
(channels used by a WEBRC session are mapped uniquely to consecuti)2.75
E .33 -.165(ve c)-.275 H(hannel).165 E 2.75(numbers. In)72 508.2 R
(each pack)2.75 E(et sent to a channel, the channel number that corresp\
onds to the channel is)-.11 E
(carried in the WEBRC Congestion Control Information.)72 521.2 Q 2.75
(AW)5.5 G(EBRC recei)-2.75 E -.165(ve)-.275 G 2.75(ru).165 G
(ses the channel)-2.75 E
(number to determine which channel within a session a pack)72 534.2 Q
(et is recei)-.11 E -.165(ve)-.275 G 2.75(df).165 G(rom.)-2.75 E
(At the sender)72 560.2 Q 2.75(,t)-.44 G
(ime is partitioned into time slots, each of duration TSD seconds.)-2.75
E(There are a \214x)5.5 E(ed)-.165 E
(number T of time slot indices associated with a session.)72 573.2 Q
(As time progresses, the current time slot)5.5 E(inde)72 586.2 Q 2.75
(xi)-.165 G(ncreases by one modulo T each TSD seconds.)-2.75 E
(The current time slot inde)5.5 E 2.75(xC)-.165 G(TSI is carried)-2.75 E
(in the WEBRC Congestion Control Information.)72 599.2 Q(This allo)5.5 E
(ws recei)-.275 E -.165(ve)-.275 G(rs to perform v).165 E(ery coarse-)
-.165 E(grained synchronization within a session.)72 612.2 Q
(WEBRC congestion control is achie)72 638.2 Q -.165(ve)-.275 G 2.75(db)
.165 G 2.75(yh)-2.75 G -.22(av)-2.75 G(ing the sender send pack).22 E
(ets associated with a)-.11 E(gi)72 651.2 Q -.165(ve)-.275 G 2.75(ns)
.165 G(ession to se)-2.75 E -.165(ve)-.275 G(ral dif).165 E
(ferent channels.)-.275 E(Indi)5.5 E(vidual recei)-.275 E -.165(ve)-.275
G(rs dynamically join and lea).165 E .33 -.165(ve t)-.22 H(hese).165 E
(channels according to the netw)72 664.2 Q(ork congestion the)-.11 E
2.75(ye)-.165 G 2.75(xperience. These)-2.915 F(congestion control)2.75 E
(adjustments are performed at each recei)72 677.2 Q -.165(ve)-.275 G
2.75(ri).165 G(ndependently of all other recei)-2.75 E -.165(ve)-.275 G
(rs, without an).165 E(y)-.165 E(impact on the sender)72 690.2 Q 5.5(.A)
-.605 G(pack)-2.75 E
(et sequence number is carried in the WEBRC Congestion Control)-.11 E
2.75(Information. The)72 703.2 R(pack)2.75 E
(et sequence numbers are consecuti)-.11 E -.165(ve)-.275 G
(ly numbered per channel and are used).165 E(by recei)72 716.2 Q -.165
(ve)-.275 G(rs to measure pack).165 E(et loss.)-.11 E(Luby/Go)72 769 Q
289.902(yal Section)-.11 F 2.75(3. [P)2.75 F(age 5])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E(The channels associated with \
a session consist of one base channel and T w)72 85 Q -2.475 -.22(av e)
-.11 H 2.75(channels. The)2.97 F(pack)72 98 Q
(et rate for each channel v)-.11 E(aries o)-.275 E -.165(ve)-.165 G 2.75
(rt).165 G 2.75(ime. F)-2.75 F(or the base channel, pack)-.165 E
(ets are sent to the)-.11 E(channel at a lo)72 111 Q 2.75(wr)-.275 G
(ate BCR_P at the be)-2.75 E
(ginning of a time slot and this rate gradually decreases to)-.165 E(P*\
BCR_P at the end of the time slot, where P < 1 is a constant de\214ned \
later)72 124 Q 5.5(.T)-.605 G(his pattern for the)-5.5 E
(base channel repeats o)72 137 Q -.165(ve)-.165 G 2.75(re).165 G
(ach time slot.)-2.75 E -.165(Fo)5.5 G 2.75(re).165 G(ach w)-2.75 E
-2.475 -.22(av e)-.11 H(channel i, pack)2.97 E
(ets are sent to channel i at)-.11 E 2.75(ar)72 150 S
(ate that \214rst increases v)-2.75 E
(ery quickly to a high rate and then decreases o)-.165 E -.165(ve)-.165
G 2.75(rt).165 G(ime by a \214x)-2.75 E(ed)-.165 E(fraction P per time \
slot until a rate of BCR_P is reached at the end of time slot i.)72 163
Q(Then, for a)5.5 E(period of time called the quiescent period, no pack)
72 176 Q(ets are sent to w)-.11 E -2.475 -.22(av e)-.11 H
(channel i, and thereafter)2.97 E(the whole c)72 189 Q
(ycle repeats itself, where the duration of the c)-.165 E
(ycle is T*TSD seconds.)-.165 E(Thus, the w)5.5 E -2.475 -.22(av e)-.11
H(channels are going through the same c)72 202 Q(yclic pattern of pack)
-.165 E(et rate transmission spaced out e)-.11 E -.165(ve)-.275 G(nly)
.165 E(by TSD seconds.)72 215 Q(Before joining a session, the recei)72
241 Q -.165(ve)-.275 G
(rs MUST obtain enough of the session description to start the).165 E
2.75(session. This)72 254 R(MUST include the rele)2.75 E -.275(va)-.275
G(nt session parameters needed by a recei).275 E -.165(ve)-.275 G 2.75
(rt).165 G 2.75(op)-2.75 G(articipate)-2.75 E
(in the session and perform WEBRC congestion control.)72 267 Q
(The session description is determined by)5.5 E
(the sender and is typically communicated to the recei)72 280 Q -.165
(ve)-.275 G(rs out of band.).165 E(Ho)5.5 E 2.75(wr)-.275 G(ecei)-2.75 E
-.165(ve)-.275 G(rs obtain the).165 E
(session description is outside the scope of this document.)72 293 Q
(When a recei)72 319 Q -.165(ve)-.275 G 2.75(ri).165 G
(nitiates a session, it \214rst joins the base channel.)-2.75 E
(The pack)5.5 E(ets in the base channel)-.11 E(help the recei)72 332 Q
-.165(ve)-.275 G 2.75(ro).165 G
(rient itself in terms of what the current time slot inde)-2.75 E 2.75
(xi)-.165 G(s, which in turn allo)-2.75 E(ws)-.275 E(the recei)72 345 Q
-.165(ve)-.275 G 2.75(rt).165 G 2.75(ok)-2.75 G(no)-2.75 E 2.75(wt)-.275
G(he relati)-2.75 E .33 -.165(ve r)-.275 H(ates on the w).165 E -2.475
-.22(av e)-.11 H 2.75(channels. The)2.97 F(recei)2.75 E -.165(ve)-.275 G
2.75(rr).165 G(emains joined to the)-2.75 E
(base channel for the duration of its participation in the session.)72
358 Q(At each point in time the acti)72 384 Q .33 -.165(ve \()-.275 H
(non-quiescent\) w).165 E -2.475 -.22(av e)-.11 H
(channels are ordered into layers, where the)2.97 E(lo)72 397 Q
(west layer is the acti)-.275 E .33 -.165(ve w)-.275 H -2.475 -.22(av e)
.055 H(channel whose w)2.97 E -2.475 -.22(av e)-.11 H
(is nearest to completion and the highest layer)2.97 E(is the acti)72
410 Q .33 -.165(ve w)-.275 H -2.475 -.22(av e).055 H(channel whose w)
2.97 E -2.475 -.22(av e)-.11 H(is furthest from completion.)2.97 E
(\(This is almost the same as)5.5 E(saying that the lo)72 423 Q
(west layer has the lo)-.275 E
(west rate and the highest layer has the highest rate.)-.275 E(The)5.5 E
(possible de)72 436 Q(viation from this is due to the optional non-e)
-.275 E(xponential be)-.165 E(ginnings of the w)-.165 E -2.475 -.22
(av e)-.11 H 2.75(sa).22 G(s)-2.75 E(described in [6].\) Each time a w)
72 449 Q -2.475 -.22(av e)-.11 H(channel becomes acti)2.97 E -.165(ve)
-.275 G 2.75(,i).165 G 2.75(ti)-2.75 G 2.75(st)-2.75 G(he highest layer)
-2.75 E 5.5(.A)-.605 G 2.75(tt)-5.5 G(he end of)-2.75 E
(each time slot the lo)72 462 Q(west layer w)-.275 E -2.475 -.22(av e)
-.11 H(channel becomes quiescent, and thus all acti)2.97 E .33 -.165
(ve w)-.275 H -2.475 -.22(av e).055 H(channels mo)72 475 Q .33 -.165
(ve d)-.165 H -.275(ow).165 G 2.75(nal).275 G
(ayer at this point in time.)-2.75 E(At each point in time a recei)5.5 E
-.165(ve)-.275 G 2.75(ri).165 G 2.75(sj)-2.75 G(oined to the)-2.75 E
(base channel and a consecuti)72 488 Q .33 -.165(ve s)-.275 H
(et of layers starting with the lo).165 E 2.75(west. Each)-.275 F
(time a recei)2.75 E -.165(ve)-.275 G 2.75(rj).165 G(oins a)-2.75 E -.11
(wa)72 501 S .33 -.165(ve c)-.11 H(hannel it joins the lo).165 E
(west layer not yet joined.)-.275 E 2.75(Ar)5.5 G(ecei)-2.75 E -.165(ve)
-.275 G 2.75(ra).165 G -.11(lwa)-2.75 G(ys lea).11 E -.165(ve)-.22 G
2.75(st).165 G(he lo)-2.75 E(west layer)-.275 E
(when it becomes quiescent.)72 514 Q(After joining a session the recei)
72 540 Q -.165(ve)-.275 G 2.75(ra).165 G(djusts its rate upw)-2.75 E
(ards by joining w)-.11 E -2.475 -.22(av e)-.11 H(channels in sequence,)
2.97 E(starting with the lo)72 553 Q(west layer and mo)-.275 E(ving to)
-.165 E -.11(wa)-.275 G(rds the highest.).11 E(The rates on the acti)5.5
E .33 -.165(ve w)-.275 H -2.475 -.22(av e).055 H
(channels are decreasing with time, so the recei)72 566 Q -.165(ve)-.275
G 2.75(ra).165 G(djusts its rate do)-2.75 E(wnw)-.275 E
(ards simply by refraining)-.11 E(from joining additional w)72 579 Q
-2.475 -.22(av e)-.11 H 2.75(channels. Since)2.97 F
(the layer ordering among the channels changes)2.75 E(dynamically o)72
592 Q -.165(ve)-.165 G 2.75(rt).165 G
(ime depending on the current time slot inde)-2.75 E
(x, it is important that the recei)-.165 E -.165(ve)-.275 G(r).165 E
(continually monitor the current time slot inde)72 605 Q 2.75(xc)-.165 G
(ontained in recei)-2.75 E -.165(ve)-.275 G 2.75(dp).165 G(ack)-2.75 E
2.75(ets. The)-.11 F(reception rate)2.75 E(at the recei)72 618 Q -.165
(ve)-.275 G 2.75(ri).165 G 2.75(sd)-2.75 G(etermined by ho)-2.75 E 2.75
(we)-.275 G(arly each w)-2.75 E -2.475 -.22(av e)-.11 H
(channel is joined by the recei)2.97 E -.165(ve)-.275 G(r: the earlier)
.165 E(the recei)72 631 Q -.165(ve)-.275 G 2.75(rj).165 G
(oins a channel with respect to when its w)-2.75 E -2.475 -.22(av e)-.11
H(started, the higher the reception rate.)2.97 E(Once the recei)72 657 Q
-.165(ve)-.275 G 2.75(ri).165 G 2.75(sj)-2.75 G(oined to a w)-2.75 E
-2.475 -.22(av e)-.11 H(channel, the recei)2.97 E -.165(ve)-.275 G 2.75
(rr).165 G(emains joined to the w)-2.75 E -2.475 -.22(av e)-.11 H
(channel)2.97 E
(until the channel goes quiescent, at which point the recei)72 670 Q
-.165(ve)-.275 G 2.75(rM).165 G(UST lea)-2.75 E .33 -.165(ve t)-.22 H
(he channel.).165 E(The w)72 696 Q(ay the recei)-.11 E -.165(ve)-.275 G
2.75(ra).165 G
(djusts its reception rate is inspired by TFRC [7]. The recei)-2.75 E
-.165(ve)-.275 G 2.75(ra).165 G 2.75(ta)-2.75 G(ll points)-2.75 E
(in time maintains a tar)72 709 Q(get reception rate, and the recei)
-.198 E -.165(ve)-.275 G 2.75(ri).165 G 2.75(sa)-2.75 G(llo)-2.75 E
(wed to join the ne)-.275 E(xt w)-.165 E -2.475 -.22(av e)-.11 H
(channel)2.97 E(if after joining its anticipated reception rate from al\
l the layers it is joined to w)72 722 Q(ould be at most its)-.11 E
(Luby/Go)72 769 Q 289.902(yal Section)-.11 F 2.75(3. [P)2.75 F(age 6])
-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E(tar)72 85 Q
(get reception rate.)-.198 E(The tar)5.5 E
(get rate is continually updated based on a set of measured)-.198 E 2.75
(parameters. The)72 98 R
(primary parameters are an estimate LOSSP of the a)2.75 E -.165(ve)-.22
G(rage loss probability and).165 E(an estimate AR)72 111 Q(TT of the a)
-.66 E -.165(ve)-.22 G(rage multicast round-trip time.).165 E/F1 11
/Times-Bold@0 SF(3.1.)72 153.6 Q/F2 13/Times-Bold@0 SF(Sender Operation)
5.5 E F0(The sender operation is by design much simpler than the recei)
72 170.2 Q -.165(ve)-.275 G 2.75(ro).165 G(peration.)-2.75 E F1 2.75
(3.1.1. Sender)72 212.8 R(inputs and initialization)2.75 E F0
(The primary input to the sender for the session is SR_b)72 229.4 Q 5.5
(.S)-.44 G(R_b is an upper bound to the sender)-5.5 E
(transmission rate in bits per second at an)72 242.4 Q 2.75(yp)-.165 G
(oint in time \(with some reasonable granularity\) in)-2.75 E(aggre)72
255.4 Q -.055(ga)-.165 G(te to all channels.).055 E(Naturally)5.5 E 2.75
(,t)-.715 G(his is then also the maximum rate in bits per second that)
-2.75 E(an)72 268.4 Q 5.5(yr)-.165 G(ecei)-5.5 E -.165(ve)-.275 G 2.75
(rc).165 G(ould recei)-2.75 E .33 -.165(ve d)-.275 H
(ata from the session at an).165 E 2.75(yp)-.165 G(oint in time.)-2.75 E
(It is RECOMMENDED)5.5 E(that the sender transmission rate in aggre)72
281.4 Q -.055(ga)-.165 G
(te to all channels be made constant as described in [6].).055 E(It is \
also RECOMMENDED that the session description indicate whether the aggr\
e)72 294.4 Q -.055(ga)-.165 G(te).055 E
(transmission rate is constant, unless there is no ambiguity)72 307.4 Q
(.)-.715 E(The secondary inputs to the sender are listed belo)72 333.4 Q
4.18 -.715(w. T)-.275 H(hese inputs are secondary because their).715 E
-.275(va)72 346.4 S(lues will generally be \214x).275 E(ed to def)-.165
E(ault v)-.11 E(alues that will not change, because the)-.275 E 2.75(yw)
-.165 G(ill be deri)-2.75 E -.165(ve)-.275 G(d).165 E
(from SR_b, or because the)72 359.4 Q 2.75(ya)-.165 G
(re chosen based on non-WEBRC considerations.)-2.75 E 11(oL)77.5 376 S
(ENP_B is the length of pack)-11 E(ets in bytes sent to the session.)
-.11 E(The v)5.5 E(alue of LENP_B depends)-.275 E
(on the complete protocol, b)94 389 Q
(ut in general this SHOULD be set to as high a v)-.22 E
(alue as possible)-.275 E(without e)94 402 Q
(xceeding the MTU size for the netw)-.165 E(ork that w)-.11 E
(ould cause fragmentation.)-.11 E 11(oB)77.5 418.6 S
(CR_P is the transmission rate on the base channel at the be)-11 E
(ginning of a time slot in pack)-.165 E(ets)-.11 E(per second.)94 431.6
Q(The def)5.5 E(ault v)-.11 E(alue for BCR_P is 1.)-.275 E 11(oT)77.5
448.2 S(SD is the time slot duration measured in seconds.)-11 E
(The RECOMMENDED v)5.5 E(alue for TSD)-.275 E(is 10.)94 461.2 Q 11(oQ)
77.5 477.8 S 2.75(Di)-11 G 2.75(st)-2.75 G
(he minimum quiescent period duration measured in seconds.)-2.75 E(The)
5.5 E(RECOMMENDED v)94 490.8 Q(alue for QD is 300.)-.275 E 11(oP)77.5
507.4 S(is the multiplicati)-8.25 E .33 -.165(ve d)-.275 H(rop in e).165
E -.165(ve)-.275 G(ry channel rate o).165 E -.165(ve)-.165 G 2.75(re)
.165 G(ach time slot.)-2.75 E(The def)5.5 E(ault v)-.11 E(alue for P)
-.275 E(is 0.75.)94 520.4 Q 11(oN)77.5 537 S
(is the duration in time slots for each w)-8.25 E -2.475 -.22(av e)-.11
H 5.5(.N).22 G(is also the number of w)-2.75 E -2.475 -.22(av e)-.11 H
(channels acti)2.97 E -.165(ve)-.275 G(at an)94 550 Q 2.75(yt)-.165 G
2.75(ime. \(A)-2.75 F -.11(wa)2.75 G .33 -.165(ve c)-.11 H
(hannel is called acti).165 E .33 -.165(ve w)-.275 H
(hen it is not quiescent.\)).165 E 2.75(As)5.5 G(ender may)-2.75 E
(choose an)94 563 Q 2.75(yv)-.165 G(alue that allo)-3.025 E
(ws it to produce w)-.275 E -2.475 -.22(av e)-.11 H 2.75(st).22 G
(hat substantially follo)-2.75 E 2.75(wt)-.275 G(he required)-2.75 E
-.165(ex)94 576 S(ponential shape described in Section 3.1.2. A RECOMME\
NDED mechanism for relating).165 E 2.75(Nt)94 589 S 2.75(oS)-2.75 G
(R_b, BCR_P and P is described in [6].)-2.75 E
(From these inputs the follo)72 605.6 Q(wing \214x)-.275 E
(ed sender parameters can be deri)-.165 E -.165(ve)-.275 G 2.75(da).165
G 2.75(sf)-2.75 G(ollo)-2.75 E(ws.)-.275 E 11(oS)77.5 622.2 S
(R_P = SR_b/\(8*LENP_B\) is the sender transmission rate in pack)-11 E
(ets per second.)-.11 E 11(oB)77.5 638.8 S
(CR_b = 8*LENP_B*BCR_P is the rate of the base channel at the be)-11 E
(ginning of a time slot)-.165 E(in bits per second.)94 651.8 Q 11(oL)
77.5 668.4 S 2.75(=c)-8.25 G
(eil\(BCR_P*TSD*\(P-1\)/log\(P\)\) is the number of base channel pack)
-2.75 E(ets sent in each time)-.11 E(slot.)94 681.4 Q 11(oQ)77.5 698 S
2.75(=c)-8.25 G
(eil\(QD/TSD\) is the number of quiescent time slots per c)-2.75 E
(ycle for a w)-.165 E -2.475 -.22(av e)-.11 H(channel.)2.97 E(Luby/Go)72
769 Q 273.402(yal Section)-.11 F 2.75(3.1.1. [P)2.75 F(age 7])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E 11(oT)77.5 85 S 2.75(=N+Qi)
-8.25 G 2.75(st)-2.75 G(he total number of time slots in a c)-2.75 E
2.75(ycle. T)-.165 F(is also the total number of w)2.75 E -2.475 -.22
(av e)-.11 H(channels.)94 98 Q 11(oF)77.5 114.6 S
(or the base channel CN = T and for the w)-11.165 E -2.475 -.22(av e)
-.11 H(channels CN = 0,1,...,T)2.97 E 2.75(-1. The)-1.012 F
(sender has the)2.75 E(description of the channels assigned to the sess\
ion and the mapping between the channels)94 127.6 Q(and the CNs.)94
140.6 Q 11(oC)77.5 157.2 S 2.75(=T)-8.25 G
(SD*T is the total duration of a c)-2.75 E(ycle in seconds.)-.165 E/F1
11/Times-Bold@0 SF 2.75(3.1.2. Sending)72 199.8 R(pack)2.75 E
(ets to the session)-.11 E F0(The sender k)72 216.4 Q
(eeps track of the current time slot inde)-.11 E 2.75(xC)-.165 G 2.75
(TSI. The)-2.75 F -.275(va)2.75 G(lue of CTSI is incremented by).275 E
2.75(1m)72 229.4 S(odulo T each TSD seconds.)-2.75 E(The v)5.5 E
(alue of CTSI is placed into each pack)-.275 E(et in the format)-.11 E
(described in Section 5. F)72 242.4 Q(or each pack)-.165 E
(et sent to the session, the sender also places the channel)-.11 E
(number CN of the channel into the pack)72 255.4 Q
(ets in the format described in Section 5. Recall that CN =)-.11 E 2.75
(Tf)72 268.4 S(or the base channel and CN = 0,1,...,T)-2.75 E
(-1 for the w)-1.012 E -2.475 -.22(av e)-.11 H(channels.)2.97 E -.165
(Fo)72 285 S 2.75(re).165 G(ach pack)-2.75 E
(et sent to the session, the sender calculates a pack)-.11 E
(et sequence number PSN and)-.11 E(places it into the pack)72 298 Q 2.75
(et. The)-.11 F -.275(va)2.75 G(lue of PSN is scoped by CN, and the v)
.275 E(alue of PSN is)-.275 E(consecuti)72 311 Q -.165(ve)-.275 G
(ly increasing within each channel.).165 E(Furthermore, for each w)5.5 E
-2.475 -.22(av e)-.11 H(channel, the last)2.97 E(pack)72 324 Q
(et sent before the channel becomes quiescent must ha)-.11 E .33 -.165
(ve t)-.22 H(he maximum possible PSN v).165 E(alue.)-.275 E(When the sh\
ort format for Congestion Control Information is used \(see Section 5.1\
\), this implies)72 337 Q(that for an)72 350 Q 2.75(yw)-.165 G -2.475
-.22(av e)-2.86 H(channel the last PSN v)2.97 E
(alue sent to the channel just before the channel becomes)-.275 E
(quiescent is 2^16-1 = 65 535.)72 363 Q(Similarly)5.5 E 2.75(,w)-.715 G
(hen the long format for Congestion Control)-2.75 E
(Information is used \(see Section 5.2\), the PSN for the \214nal pack)
72 376 Q(et of an)-.11 E 2.75(yw)-.165 G -2.475 -.22(av e)-2.86 H
(is 2^32-1 = 4 294)2.97 E(967 295.)72 389 Q(The PSN of the initial pack)
5.5 E(et of a w)-.11 E -2.475 -.22(av e)-.11 H(thus depends on TSD, P)
2.97 E 2.75(,B)-1.221 G(CR_P and SR_P)-2.75 E(.)-1.221 E -.165(Fo)72 402
S 2.75(rt).165 G(he base channel, the \214rst pack)-2.75 E
(et of each time slot has a PSN congruent to zero modulo L.)-.11 E(Henc\
e, instead of 2^16 - 1 or 2^32 - 1 being the highest PSN used \(dependi\
ng on the choice of)72 415 Q(short format or long format Congestion Con\
trol Information\), the highest PSN is one less than the)72 428 Q(lar)72
441 Q(gest multiple of L that does not e)-.198 E
(xceed 2^16 \(short format\) or 2^32 \(long format\).)-.165 E
(The format)5.5 E(for the PSN within pack)72 454 Q
(ets is described in Section 5.)-.11 E(The rate at which pack)72 470.6 Q
(ets are sent to the base channel starts at BCR_P pack)-.11 E
(ets per second at the)-.11 E(be)72 483.6 Q
(ginning of each time slot and decreases e)-.165 E
(xponentially to P*BCR_P at the end of that time slot.)-.165 E(The pack)
72 513.2 Q(et rate for the w)-.11 E -2.475 -.22(av e)-.11 H
(channels is more complicated.)2.97 E(Each w)5.5 E -2.475 -.22(av e)-.11
H(channel carries a)2.97 E(sequence of w)72 526.2 Q -2.475 -.22(av e)
-.11 H 2.75(ss).22 G(eparated by quiescent periods.)-2.75 E(On each w)
5.5 E -2.475 -.22(av e)-.11 H(channel each w)2.97 E -2.475 -.22(av e)
-.11 H(is acti)2.97 E -.165(ve)-.275 G(during N time slots follo)72
539.2 Q(wed by a quiescent period of Q time slots.)-.275 E(The w)5.5 E
-2.475 -.22(av e)-.11 H 2.75(so).22 G 2.75(nw)-2.75 G -2.475 -.22(av e)
-2.86 H(channel i)2.97 E(end at the ends of time slots with CTSI i.)72
552.2 Q(Therefore w)5.5 E -2.475 -.22(av e)-.11 H(channel i is acti)2.97
E .33 -.165(ve d)-.275 H(uring time slots i-).165 E(N+1 modulo T)72
565.2 Q 2.75(,i)-.814 G(-N+2 modulo T)-2.75 E 2.75(,.)-.814 G
(.., i and is quiescent for time slots i+1 modulo T)-2.75 E 2.75(,i)
-.814 G(+2 modulo T)-2.75 E(,)-.814 E(..., i+Q modulo T)72 578.2 Q 5.5
(.W)-.814 G -2.475 -.22(av e)-6.38 H(channel i \214rst becomes acti)2.97
E .33 -.165(ve w)-.275 H(ithin time slot i-N+1 modulo T at a point).165
E(in time that may depend on the v)72 591.2 Q(alue of SR_b)-.275 E(.)
-.44 E -.165(Fo)72 620.8 S 2.75(ras).165 G
(ubstantial fraction of the duration of a w)-2.75 E -2.475 -.22(av e)
-.11 H(ending at the end of a w)2.97 E -2.475 -.22(av e)-.11 H 2.75(,t)
.22 G(he pack)-2.75 E(et rate)-.11 E(MUST decrease e)72 633.8 Q
(xponentially by a f)-.165 E
(actor of P per TSD seconds, with a rate of BCR_P at the end)-.11 E
(of the last acti)72 646.8 Q .33 -.165(ve t)-.275 H(ime slot.).165 E
(At the be)5.5 E(ginning of each w)-.165 E -2.475 -.22(av e)-.11 H 2.75
(,t).22 G(he rate MA)-2.75 E 2.75(Yd)-1.155 G -.275(ev)-2.75 G
(iate from this).275 E -.165(ex)72 659.8 S
(ponential form so that the total sending rate in aggre).165 E -.055(ga)
-.165 G(te to all of the channels is constant.).055 E(A)5.5 E
(RECOMMENDED design for the be)72 672.8 Q(ginnings of w)-.165 E -2.475
-.22(av e)-.11 H 2.75(st).22 G 2.75(oa)-2.75 G(chie)-2.75 E .33 -.165
(ve t)-.275 H(his goal is described in [6].).165 E(Luby/Go)72 769 Q
273.402(yal Section)-.11 F 2.75(3.1.2. [P)2.75 F(age 8])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E/F1 11/Times-Bold@0 SF(3.2.)72
85 Q/F2 13/Times-Bold@0 SF(Recei)5.5 E -.13(ve)-.13 G 3.25(rO).13 G
(peration)-3.25 E F0(The b)72 101.6 Q(ulk of the comple)-.22 E
(xity in WEBRC is in the recei)-.165 E -.165(ve)-.275 G 2.75(ro).165 G
2.75(peration. F)-2.75 F(or ease of e)-.165 E(xplanation,)-.165 E
(suppose for the moment that during the reception there is no pack)72
114.6 Q(et loss and pack)-.11 E(ets are arri)-.11 E(ving)-.275 E(at e)72
127.6 Q(xactly the rate at which the)-.165 E 2.75(yw)-.165 G(ere sent.)
-2.75 E(The sender transmission rate to the channels is)5.5 E
(designed so that the recei)72 140.6 Q -.165(ve)-.275 G 2.75(rr).165 G
(eception rate beha)-2.75 E -.165(ve)-.22 G 2.75(sa).165 G 2.75(sf)-2.75
G(ollo)-2.75 E(ws.)-.275 E(Upon entering a session, the recei)72 166.6 Q
-.165(ve)-.275 G 2.75(ri).165 G(mmediately joins the base channel.)-2.75
E(When the recei)5.5 E -.165(ve)-.275 G(r).165 E -.11(wa)72 179.6 S
(nts to increase its rate, it joins consecuti).11 E .33 -.165(ve l)-.275
H(ayers starting with the lo).165 E(west and mo)-.275 E(ving to)-.165 E
-.11(wa)-.275 G(rds).11 E
(the highest. \(Recall that the designations of lo)72 192.6 Q
(west to highest change as w)-.275 E -2.475 -.22(av e)-.11 H 2.75(sb).22
G(ecome acti)-2.75 E .33 -.165(ve a)-.275 H(nd).165 E 2.75
(quiescent.\) When)72 205.6 R(the recei)2.75 E -.165(ve)-.275 G 2.75(rw)
.165 G
(ants to maintain its current reception rate and it is already joined)
-2.86 E(to the lo)72 218.6 Q(west NWC layers, if the recei)-.275 E -.165
(ve)-.275 G 2.75(rj).165 G
(oins channel i-1+NWC modulo T sometime during)-2.75 E
(time slot i then the recei)72 231.6 Q -.165(ve)-.275 G 2.75(rj).165 G
(oins channel i+NWC modulo T TSD seconds later in time slot i+1.)-2.75 E
(When the lo)72 244.6 Q(west layer becomes quiescent the recei)-.275 E
-.165(ve)-.275 G 2.75(rl).165 G(ea)-2.75 E -.165(ve)-.22 G 2.75(st).165
G(he channel.)-2.75 E(Suppose the recei)72 270.6 Q -.165(ve)-.275 G 2.75
(rw).165 G
(ants to decrease its rate till it is joined to just the base channel.)
-2.86 E(Assume)5.5 E(that a recei)72 283.6 Q -.165(ve)-.275 G 2.75(ri)
.165 G 2.75(sj)-2.75 G(oined to the lo)-2.75 E
(west NWC < N-2 layers at the be)-.275 E
(ginning of time slot i, i.e., w)-.165 E -2.475 -.22(av e)-.11 H
(channels i, i+1 modulo T)72 296.6 Q(,..., i+NWC-1 modulo T)-.814 E 5.5
(.T)-.814 G(hen, the aggre)-5.5 E -.055(ga)-.165 G(te pack).055 E
(et reception rate of)-.11 E(the recei)72 309.6 Q -.165(ve)-.275 G 2.75
(ro).165 G -.165(ve)-2.915 G 2.75(rt).165 G(he ne)-2.75 E
(xt NWC time slots will beha)-.165 E .33 -.165(ve a)-.22 H 2.75(sf).165
G(ollo)-2.75 E(ws if the recei)-.275 E -.165(ve)-.275 G 2.75(rd).165 G
(oes not join an)-2.75 E(y)-.165 E -.11(wa)72 322.6 S .33 -.165(ve c)
-.11 H(hannels during this time.).165 E(At the be)5.5 E
(ginning of time slot i the recei)-.165 E -.165(ve)-.275 G 2.75(rr).165
G(eception rate is)-2.75 E
(BCR_P*\(1 + \(1/P\) + \(1/P\)^2 + ... + \(1/P\)^NWC\).)72 335.6 Q
(Then the recei)5.5 E -.165(ve)-.275 G 2.75(rr).165 G
(eception rate decreases by a)-2.75 E -.11(fa)72 348.6 S(ctor of P o).11
E -.165(ve)-.165 G 2.75(rt).165 G(he duration of each time slot, and at\
 the end of each time slot the reception rate)-2.75 E
(decreases by an additi)72 361.6 Q .33 -.165(ve a)-.275 H
(mount of P*BCR_P).165 E 5.5(.A)-1.221 G 2.75(tt)-5.5 G
(he end of time slot i+NWC-1 mod T)-2.75 E 2.75(,t)-.814 G(he)-2.75 E
(recei)72 374.6 Q -.165(ve)-.275 G 2.75(rr).165 G
(eception rate is BCR_P*\(1+P\), and at the be)-2.75 E
(ginning of time slot i+NWC mod T the)-.165 E(recei)72 387.6 Q -.165(ve)
-.275 G 2.75(ri).165 G 2.75(sj)-2.75 G
(oined only to the base channel and its reception rate is BCR_P)-2.75 E
(.)-1.221 E F1 2.75(3.2.1. Recei)72 430.2 R -.11(ve)-.11 G 2.75(ri).11 G
(nputs and initialization)-2.75 E F0(Before joining a session the recei)
72 446.8 Q -.165(ve)-.275 G 2.75(rM).165 G(UST kno)-2.75 E 2.75(wt)-.275
G(he mapping between the CNs and the)-2.75 E 2.75(channels. Upon)72
459.8 R(joining the session or shortly thereafter)2.75 E 2.75(,i)-.44 G
2.75(tS)-2.75 G(HOULD ha)-2.75 E .33 -.165(ve t)-.22 H(he v).165 E
(alues of)-.275 E(LENP_B, BCR_P)72 472.8 Q 2.75(,T)-1.221 G(SD, P)-2.75
E 2.75(,N)-1.221 G 2.75(,L)-2.75 G 2.75(,Qa)-2.75 G(nd T)-2.75 E 5.5(.S)
-.814 G(ome of these v)-5.5 E(alues may be computed or measured)-.275 E
(once the recei)72 485.8 Q -.165(ve)-.275 G 2.75(rh).165 G
(as joined the session.)-2.75 E -.165(Fo)5.5 G 2.75(re).165 G
(xample, the recei)-2.915 E -.165(ve)-.275 G 2.75(rM).165 G 2.31 -1.155
(AY o)-2.75 H(btain LENP_B and T)1.155 E(from the \214rst pack)72 498.8
Q(et recei)-.11 E -.165(ve)-.275 G 2.75(df).165 G
(rom the base channel, and the recei)-2.75 E -.165(ve)-.275 G 2.75(rM)
.165 G 2.31 -1.155(AY m)-2.75 H(easure BCR_P once)1.155 E
(it is joined to the base channel.)72 511.8 Q(The v)5.5 E(alues of P)
-.275 E 2.75(,Qa)-1.221 G(nd TSD MA)-2.75 E 2.75(Yb)-1.155 G 2.75<658c>
-2.75 G -.165(xe)-2.75 G 2.75(dt).165 G 2.75(od)-2.75 G(ef)-2.75 E
(ault v)-.11 E(alues b)-.275 E(uilt)-.22 E(into the recei)72 524.8 Q
-.165(ve)-.275 G 2.75(rt).165 G
(hat do not change from session to session, and the v)-2.75 E
(alue of N MA)-.275 E 2.75(Yb)-1.155 G(e)-2.75 E(computed as T)72 537.8
Q 2.75(-Q. The)-1.012 F(recei)2.75 E -.165(ve)-.275 G 2.75(rS).165 G
(HOULD kno)-2.75 E 2.75(ww)-.275 G(hether the sender is emplo)-2.75 E
(ying a technique to)-.11 E(produce constant aggre)72 550.8 Q -.055(ga)
-.165 G(te rate as described in [6].).055 E(When a recei)72 576.8 Q
-.165(ve)-.275 G 2.75<728c>.165 G(rst joins a session, it MUST \214rst \
join just the base channel and start recei)-2.75 E(ving)-.275 E(pack)72
589.8 Q(ets to determine the current time slot inde)-.11 E 2.75(x. If)
-.165 F(during the course of the session the recei)2.75 E -.165(ve)-.275
G(r).165 E(continually loses a high fraction of the pack)72 602.8 Q
(ets from the base channel e)-.11 E -.165(ve)-.275 G 2.75(nw).165 G
(hen the recei)-2.75 E -.165(ve)-.275 G 2.75(ri).165 G(s)-2.75 E
(only joined to the base channel, the recei)72 615.8 Q -.165(ve)-.275 G
2.75(rS).165 G(HOULD lea)-2.75 E .33 -.165(ve t)-.22 H(he session.).165
E(The recei)72 641.8 Q -.165(ve)-.275 G 2.75(rM).165 G 2.31 -1.155(AY a)
-2.75 H(lso ha)1.155 E .33 -.165(ve o)-.22 H(ther indi).165 E
(vidually set parameters that may be used to determine its)-.275 E(beha)
72 654.8 Q(vior)-.22 E 5.5(.O)-.605 G(ne such parameter is MRR_b:)-5.5 E
11(oM)77.5 671.4 S(RR_b is the maximum recei)-11 E -.165(ve)-.275 G 2.75
(rr).165 G(eception rate in bits per second.)-2.75 E
(This may be used to)5.5 E
(determine the maximum reception rate this recei)94 684.4 Q -.165(ve)
-.275 G 2.75(ri).165 G 2.75(sw)-2.75 G(illing to reach.)-2.75 E
(Thus, the maximum)5.5 E(reception rate that the recei)94 697.4 Q -.165
(ve)-.275 G 2.75(rc).165 G(an possibly achie)-2.75 E .33 -.165(ve i)
-.275 H 2.75(nt).165 G(he session is the minimum of SR_b)-2.75 E
(and MRR_b)94 710.4 Q 5.5(.A)-.44 G(recommended v)-2.75 E
(alue of MRR_b for a recei)-.275 E -.165(ve)-.275 G 2.75(ri).165 G 2.75
(st)-2.75 G(he bandwidth capacity of)-2.75 E(the last link to the recei)
94 723.4 Q -.165(ve)-.275 G 3.96 -.605(r. M).165 H
(RR_P is the maximum recei).605 E -.165(ve)-.275 G 2.75(rr).165 G
(eception rate in pack)-2.75 E(ets per)-.11 E(Luby/Go)72 769 Q 273.402
(yal Section)-.11 F 2.75(3.2.1. [P)2.75 F(age 9])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E
(second, i.e., MRR_P = MRR_b/\(8*LENP_B\).)94 85 Q/F1 11/Times-Bold@0 SF
2.75(3.2.2. Recei)72 127.6 R -.11(ve)-.11 G 2.75(rm).11 G(easur)-2.75 E
(ements and calculations)-.198 E F0
(As outlined in the introduction, the w)72 144.2 Q(ay a recei)-.11 E
-.165(ve)-.275 G 2.75(ra).165 G
(djusts its reception rate is inspired by TFRC)-2.75 E([7]. The recei)72
157.2 Q -.165(ve)-.275 G 2.75(ra).165 G 2.75(ta)-2.75 G
(ll points in time maintains a tar)-2.75 E
(get reception rate, and the recei)-.198 E -.165(ve)-.275 G 2.75(ri).165
G 2.75(sa)-2.75 G(llo)-2.75 E(wed)-.275 E(to join the ne)72 170.2 Q
(xt w)-.165 E -2.475 -.22(av e)-.11 H(channel if joining w)2.97 E
(ould increase its reception rate to at most its tar)-.11 E(get)-.198 E
(reception rate.)72 183.2 Q(The tar)5.5 E
(get rate is continually updated based on a set of measured parameters.)
-.198 E -1.1 -.88(Tw o)72 209.2 T
(primary parameters are the estimate LOSSP of the a)3.63 E -.165(ve)-.22
G(rage loss probability and the estimate).165 E(AR)72 222.2 Q
(TT of the a)-.66 E -.165(ve)-.22 G(rage MR).165 E(TT)-.66 E 5.5(.B)
-.814 G(oth LOSSP and AR)-5.5 E(TT are mo)-.66 E(ving a)-.165 E -.165
(ve)-.22 G(rages of measurements).165 E(based on discrete e)72 235.2 Q
-.165(ve)-.275 G 5.5(nts. F).165 F(or man)-.165 E 2.75(yo)-.165 G 2.75
(ft)-2.75 G(he other estimates calculated by WEBRC, using an)-2.75 E
-.165(ex)72 248.2 S(ponentially weighted mo).165 E(ving a)-.165 E -.165
(ve)-.22 G(rage \(EWMA\) with a \214x).165 E(ed a)-.165 E -.165(ve)-.22
G(raging fraction is suf).165 E(\214cient.)-.275 E(Ho)72 261.2 Q(we)
-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H
(he calculations of LOSSP and AR).44 E
(TT require a more general and sophisticated \214ltering)-.66 E
(approach.)72 274.2 Q F1 2.75(3.2.2.1. A)72 316.8 R -.11(ve)-1.1 G
(rage loss pr).11 E(obability)-.198 E F0
(The design of TFRC [7] re\215ects that, because the a)72 333.4 Q -.165
(ve)-.22 G(rage pack).165 E(et loss probability can v)-.11 E(ary by)
-.275 E(orders of magnitude, an)72 346.4 Q 2.75(ye)-.165 G
(stimate of the a)-2.75 E -.165(ve)-.22 G
(rage loss probability based on either a \214x).165 E(ed number)-.165 E
(of pack)72 359.4 Q(ets or on a \214x)-.11 E
(ed period of time with a \214x)-.165 E(ed a)-.165 E -.165(ve)-.22 G
(raging fraction will be poor).165 E 5.5(.I)-.605 G 2.75(nT)-5.5 G
(FRC the)-2.75 E -2.475 -.22(av e)72 372.4 T
(rage is estimated from the numbers of pack).22 E(ets between be)-.11 E
(ginnings of loss e)-.165 E -.165(ve)-.275 G(nts, and the).165 E
(number of loss e)72 385.4 Q -.165(ve)-.275 G(nts used is \214x).165 E
(ed.)-.165 E(The estimate LOSSP of the a)72 411.4 Q -.165(ve)-.22 G
(rage loss probability of the recei).165 E -.165(ve)-.275 G 2.75(ri).165
G 2.75(sm)-2.75 G(aintained in a manner)-2.75 E(some)72 424.4 Q
(what similar to that described in TFRC [7]. The WEBRC recei)-.275 E
-.165(ve)-.275 G 2.75(re).165 G(stimates the in)-2.75 E -.165(ve)-.44 G
(rse of).165 E(the a)72 437.4 Q -.165(ve)-.22 G
(rage loss probability by applying tw).165 E 2.75(oE)-.11 G
(WMA \214lters to the pack)-2.75 E(et reception measurements,)-.11 E
2.75(at)72 450.4 S(ime-based \214lter with smoothing constant 0 < Nu < \
1 and a loss-based \214lter with smoothing)-2.75 E
(constant 0 < Delta < 1.)72 463.4 Q(The recommended v)5.5 E
(alues for the smoothing constants are Nu = 0.3 and)-.275 E
(Delta = 0.3.)72 476.4 Q
(The reason for the time-based \214lter is that the loss e)5.5 E -.165
(ve)-.275 G(nts in WEBRC are b).165 E(ursty;)-.22 E(the)72 489.4 Q 2.75
(yt)-.165 G(ypically occur just after a ne)-2.75 E 2.75(ww)-.275 G
-2.475 -.22(av e)-2.86 H(has been joined.)2.97 E 1.76 -.88(To s)5.5 H
(mooth out this b).88 E(urstiness, the)-.22 E
(time-based \214lter is applied to the pack)72 502.4 Q
(et reception measurements at the end of each epoch to)-.11 E
(smooth out the b)72 515.4 Q(ursty loss e)-.22 E -.165(ve)-.275 G(nts o)
.165 E -.165(ve)-.165 G 2.75(raf).165 G .55 -.275(ew t)-2.75 H
(ime slot durations.).275 E(Intuiti)5.5 E -.165(ve)-.275 G(ly).165 E
2.75(,t)-.715 G(he time-based \214lter)-2.75 E -2.475 -.22(av e)72 528.4
T(rages pack).22 E(et reception e)-.11 E -.165(ve)-.275 G
(nts such that the e).165 E -.165(ve)-.275 G(nts are smoothed out o).165
E -.165(ve)-.165 G 2.75(ra).165 G 2.75(ni)-2.75 G(nterv)-2.75 E
(al of time)-.275 E(proportional to TSD/Nu seconds.)72 541.4 Q
(The loss-based \214lter)5.5 E 2.75(,s)-.44 G
(imilar to what is suggested in TFRC, is)-2.75 E(applied to the output \
of the time-based \214lter to produce the estimate of the in)72 554.4 Q
-.165(ve)-.44 G(rse of the a).165 E -.165(ve)-.22 G(rage).165 E
(loss probability)72 567.4 Q 5.5(.I)-.715 G(ntuiti)-5.5 E -.165(ve)-.275
G(ly).165 E 2.75(,t)-.715 G(he loss-based \214lter a)-2.75 E -.165(ve)
-.22 G(rages loss e).165 E -.165(ve)-.275 G(nts such that each loss e)
.165 E -.165(ve)-.275 G(nt is).165 E -2.475 -.22(av e)72 580.4 T
(raged in with weight Delta.).22 E(As described later)72 606.4 Q 2.75
(,L)-.44 G(OSSP is initialized at the end of slo)-2.75 E 2.75(ws)-.275 G
(tart and occasionally reset due to other)-2.75 E -2.365 -.275(ev e)72
619.4 T 2.75(nts. Let).275 F 2.75(Wa)2.75 G(nd X be counts of pack)-2.75
E(ets, let Y be a count of loss e)-.11 E -.165(ve)-.275 G
(nts and let Z be the long-).165 E(term estimate of the in)72 632.4 Q
-.165(ve)-.44 G(rse of the a).165 E -.165(ve)-.22 G
(rage loss probability).165 E 5.5(.W)-.715 G(hene)-5.5 E -.165(ve)-.275
G 2.75(rt).165 G(he v)-2.75 E(alue of LOSSP is)-.275 E
(initialized or reset, the v)72 645.4 Q(alues of W)-.275 E 2.75(,X)
-1.012 G 2.75(,Ya)-2.75 G(nd Z are also initialized or reset.)-2.75 E
(Recall that TSD is the duration of a time slot.)72 671.4 Q
(The epoch length EL is the duration of time)5.5 E
(between decisions to adjust the reception rate.)72 684.4 Q
(Generally EL is much smaller than TSD, and the)5.5 E(RECOMMENDED v)72
697.4 Q(alues are EL = 0.5 seconds and TSD = 10 seconds.)-.275 E(De\214\
ne G = Nu*EL/TSD as the amount of time-based smoothing to perform at th\
e end of each)72 723.4 Q(Luby/Go)72 769 Q 259.652(yal Section)-.11 F
2.75(3.2.2.1. [P)2.75 F(age 10])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E 2.75(epoch. The)72 85 R
(update rules for W)2.75 E 2.75(,Y)-1.012 G 2.75(,Za)-4.169 G
(nd LOSSP are the follo)-2.75 E(wing:)-.275 E 11(oA)77.5 114.6 S 2.75
(tt)-11 G
(he end of each epoch, adjust X, Y and Z and compute LOSSP as follo)
-2.75 E(ws:)-.275 E 2.75(Z=Z)116 131.2 S
(*\(1-Delta\)^\(G*Y\) + X/\(Y+1\)*\(1-\(1-Delta\)^\(Y+1\)\))-2.75 E 2.75
(X=X)116 147.8 S(*\(1-G\))-2.75 E 2.75(Y=Y)116 164.4 S(*\(1-G\))-2.75 E
(Z1 = Z*\(1-Delta\)^Y + X/\(Y+1\)*\(1-\(1-Delta\)^\(Y+1\)\))116 181 Q(Z\
2 = Z*\(1-Delta\)^\(Y+1\) + \(X+W+1\)/\(Y+2\)*\(1-\(1-Delta\)^\(Y+2\)\))
116 197.6 Q(LOSSP = 1/max{Z1,Z2,1})116 214.2 Q 11(oF)77.5 243.8 S
(or each pack)-11.165 E(et e)-.11 E -.165(ve)-.275 G
(nt \(whether it is a recei).165 E -.165(ve)-.275 G 2.75(dp).165 G(ack)
-2.75 E(et or a lost pack)-.11 E(et\), W = W + 1)-.11 E 11(oA)77.5 273.4
S 2.75(tt)-11 G(he be)-2.75 E(ginning of each loss e)-.165 E -.165(ve)
-.275 G(nt, update X, Y and Z as follo).165 E(ws:)-.275 E 2.75(X=X+W)116
290 S 2.75(W=0)116 306.6 S 2.75(Y=Y+1)116 323.2 S
(The intuition behind these update rules is the follo)72 352.8 Q 2.75
(wing. If)-.275 F(just loss-\214ltering were used to update)2.75 E
(Z, then Z w)72 365.8 Q(ould be decreased by a multiplicati)-.11 E .33
-.165(ve a)-.275 H(mount 1 - Delta for each loss e).165 E -.165(ve)-.275
G(nt and Z).165 E -.11(wo)72 378.8 S(uld be increased by an additi).11 E
.33 -.165(ve a)-.275 H(mount Delta for each pack).165 E 2.75(et. T)-.11
F 2.75(os)-.88 G(mooth out loss e)-2.75 E -.165(ve)-.275 G(nts o).165 E
-.165(ve)-.165 G(r).165 E
(more than one time slot, these adjustments are \214ltered into Z o)72
391.8 Q -.165(ve)-.165 G 2.75(rt).165 G
(ime, at the rate of a fraction G)-2.75 E(at the end of each epoch.)72
404.8 Q(Thus, the v)5.5 E
(ariables X and Y are counts of the portions of the pack)-.275 E(ets)
-.11 E(and loss e)72 417.8 Q -.165(ve)-.275 G(nts, respecti).165 E -.165
(ve)-.275 G(ly).165 E 2.75(,t)-.715 G(hat ha)-2.75 E .33 -.165(ve n)-.22
H(ot yet been \214ltered into the long-term memory Z.).165 E 2.75(Wi)5.5
G(s)-2.75 E(the count of pack)72 430.8 Q(ets since the last loss e)-.11
E -.165(ve)-.275 G(nt started.).165 E(This e)5.5 E(xplains wh)-.165 E
2.75(yWi)-.055 G 2.75(si)-2.75 G(ncreased by one for)-2.75 E(each pack)
72 443.8 Q(et and Y is increased by one for each loss e)-.11 E -.165(ve)
-.275 G 2.75(nt. At).165 F(the end of each epoch a fraction G)2.75 E(of\
 both X and Y are \214ltered into Z according to the loss-\214lter rule\
 described abo)72 456.8 Q -.165(ve)-.165 G 2.75(,a).165 G(nd then the)
-2.75 E(same fraction G is remo)72 469.8 Q -.165(ve)-.165 G 2.75(df).165
G(rom both X and Y to account for the f)-2.75 E
(act that this portion has been)-.11 E(\214ltered into Z.)72 482.8 Q(Th\
e LOSSP calculation combines the short-term history \(X,Y\) with the lo\
ng-term)5.5 E(history Z and also allo)72 495.8 Q(ws the arri)-.275 E
-.275(va)-.275 G(ls since the last loss W to ha).275 E .33 -.165(ve s)
-.22 H(ome in\215uence.).165 E(The v)5.5 E(alue of)-.275 E
(Z2 is what Z1 w)72 508.8 Q(ould become were the ne)-.11 E(xt pack)-.165
E(et to be lost.)-.11 E 1.76 -.88(To r)72 538.4 T
(eset the loss calculation to a v).88 E(alue LOSSP = a, the state v)
-.275 E(ariables are set as follo)-.275 E(ws:)-.275 E 2.75(W=0)116 555 S
2.75(X=0)116 571.6 S 2.75(Y=0)116 588.2 S 2.75(Z=1)116 604.8 S(/a)-2.75
E/F1 11/Times-Bold@0 SF 2.75(3.2.2.2. A)72 647.4 R -.11(ve)-1.1 G
(rage r).11 E(ound-trip time)-.198 E F0(The recei)72 664 Q -.165(ve)
-.275 G 2.75(rm).165 G(aintains an a)-2.75 E -.165(ve)-.22 G
(rage round-trip time, AR).165 E(TT)-.66 E 2.75(,a)-.814 G 2.75(sam)
-2.75 G(easurement-based \214lter of)-2.75 E(MR)72 677 Q
(TT measurements using a smoothing constant 0 < Alpha < 1.)-.66 E
(The RECOMMENDED v)5.5 E(alue)-.275 E(for Alpha is 0.25.)72 690 Q
(Each time the recei)72 716 Q -.165(ve)-.275 G 2.75(rj).165 G
(oins a channel \(either the base channel upon entering a session or w)
-2.75 E -2.475 -.22(av e)-.11 H(Luby/Go)72 769 Q 259.652(yal Section)
-.11 F 2.75(3.2.2.2. [P)2.75 F(age 11])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E
(channels continually\), it mak)72 85 Q
(es a measurement of the multicast round-trip time MR)-.11 E
(TT as follo)-.66 E(ws.)-.275 E(Let V be an auxiliary v)72 98 Q
(ariable that is used that k)-.275 E(eep track of the a)-.11 E -.165(ve)
-.22 G(rage of the square of the).165 E(MR)72 111 Q(TT measurements.)
-.66 E(When the recei)5.5 E -.165(ve)-.275 G 2.75(rs).165 G
(ends the join for the channel it records the current)-2.75 E
(time JoinT)72 124 Q(ime and sets a Boolean v)-.385 E
(ariable JOINING to true.)-.275 E(When the \214rst pack)5.5 E
(et is recei)-.11 E -.165(ve)-.275 G(d).165 E
(from the channel the recei)72 137 Q -.165(ve)-.275 G 2.75(rr).165 G
(ecords the current time FirstT)-2.75 E(ime and resets the v)-.385 E
(alue of JOINING)-.275 E(to f)72 150 Q 2.75(alse. If)-.11 F
(it is the base channel that has been joined, AR)2.75 E
(TT is set to FirstT)-.66 E(ime-JoinT)-.385 E(ime and V)-.385 E
(is set to AR)72 163 Q(TT*AR)-.66 E(TT)-.66 E 5.5(.O)-.814 G
(therwise, the v)-5.5 E(alue of MR)-.275 E(TT is set to \(FirstT)-.66 E
(ime - JoinT)-.385 E(ime\) -)-.385 E
(log\(1/P\)/2/\(1-P\)/BCR_P * P^NWC.)72 176 Q(\(Note that this v)5.5 E
(alue can be ne)-.275 E -.055(ga)-.165 G(ti).055 E -.165(ve)-.275 G 2.75
(.\) Then,).165 F(AR)2.75 E(TT is)-.66 E(updated as follo)72 189 Q 2.75
(ws. Let)-.275 F(Ome)2.75 E .11 -.055(ga = A)-.165 H(lpha*AR).055 E
(TT*AR)-.66 E(TT/V)-.66 E 2.75(,a)-1.419 G(nd at the Kth MR)-2.75 E
(TT measurement let)-.66 E(Rho = Ome)72 202 Q -.055(ga)-.165 G(/\(Ome)
.055 E -.055(ga)-.165 G(+\(1-Ome).055 E -.055(ga)-.165 G(\)*\(1-\(1-Ome)
.055 E -.055(ga)-.165 G 2.75(\)^K\)\). \(Note).055 F(that as K gro)2.75
E(ws Rho approaches)-.275 E(Ome)72 215 Q -.055(ga)-.165 G 2.75
(.\) Then,).055 F 2.75(Vi)2.75 G 2.75(su)-2.75 G
(pdated to \(1-Rho\)*V+Rho*MR)-2.75 E(TT*MR)-.66 E(TT and AR)-.66 E
(TT is updated to)-.66 E(max{P*AR)72 228 Q(TT)-.66 E(,\(1-Rho\)*AR)-.814
E(TT+Rho*MR)-.66 E(TT}.)-.66 E(Usually AR)72 254 Q
(TT is updated to the second term in the max, and in this case AR)-.66 E
(TT is the EWMA of)-.66 E(the pre)72 267 Q(vious v)-.275 E(alue of AR)
-.275 E(TT and the ne)-.66 E 2.75(wM)-.275 G -.66(RT)-2.75 G 1.628 -.814
(T, w).66 H(ith a weighting on the ne).814 E 2.75(wM)-.275 G -.66(RT)
-2.75 G 2.75(Tt).66 G(hat as K)-2.75 E(gro)72 280 Q
(ws is proportional to the square of the pre)-.275 E(vious AR)-.275 E
(TT di)-.66 E(vided by the pre)-.275 E(vious a)-.275 E -.165(ve)-.22 G
(rage V of).165 E(the square of the MR)72 293 Q(TT)-.66 E 5.5(.T)-.814 G
(hus, if there is not much v)-5.5 E(ariance in the pre)-.275 E(vious MR)
-.275 E(TTs relati)-.66 E .33 -.165(ve t)-.275 H(o).165 E
(the square of their a)72 306 Q -.165(ve)-.22 G(rage then the ne).165 E
2.75(wM)-.275 G -.66(RT)-2.75 G 2.75(Tw).66 G(ill be \214ltered into AR)
-2.75 E(TT with a high weight,)-.66 E 2.75(whereas if)72 319 R
(there is a lot of v)2.75 E(ariance in the pre)-.275 E(vious MR)-.275 E
(TTs relati)-.66 E .33 -.165(ve t)-.275 H 2.75(ot).165 G
(he square of their a)-2.75 E -.165(ve)-.22 G(rage).165 E(then the ne)72
332 Q 2.75(wM)-.275 G -.66(RT)-2.75 G 2.75(Tw).66 G
(ill be \214ltered into AR)-2.75 E(TT with a lo)-.66 E 2.75(ww)-.275 G
2.75(eight. The)-2.75 F(intuiti)2.75 E .33 -.165(ve r)-.275 H
(ationale for this).165 E(is that in general the number of measurements\
 needed to compute a meaningful a)72 345 Q -.165(ve)-.22 G(rage for a)
.165 E(random v)72 358 Q(ariable is proportional to its v)-.275 E
(ariance di)-.275 E(vided by the square of its a)-.275 E -.165(ve)-.22 G
(rage; see, e.g., [4].).165 E(By making the weight f)72 371 Q
(actor depend on pre)-.11 E(vious measurements in this w)-.275 E(ay)-.11
E 2.75(,t)-.715 G(he appropriate)-2.75 E(weight to use to a)72 384 Q
-.165(ve)-.22 G(rage the ne).165 E 2.75(wM)-.275 G -.66(RT)-2.75 G 2.75
(Ti).66 G(nto the AR)-2.75 E(TT self-adjusts automatically to the)-.66 E
-.275(va)72 397 S(riability in the measurements.).275 E/F1 11
/Times-Bold@0 SF 2.75(3.2.2.3. Rate)72 439.6 R(Equation)2.75 E F0
(The recei)72 456.2 Q -.165(ve)-.275 G 2.75(rc).165 G
(alculates the reception rate REQN based on the TCP equation as follo)
-2.75 E(ws: REQN =)-.275 E(1/\(AR)72 469.2 Q
(TT*sqrt{LOSSP}\(0.816 + 7.35*LOSSP*\(1+32*LOSSP^2\)\)\).)-.66 E
(This equation comes from)5.5 E(TFRC [7].)72 482.2 Q F1 2.75
(3.2.2.4. Epochs)72 511.8 R F0(The recei)72 528.4 Q -.165(ve)-.275 G
2.75(rm).165 G(ak)-2.75 E
(es decisions on whether or not to join another w)-.11 E -2.475 -.22
(av e)-.11 H(channel at equally spaced)2.97 E
(units of time called epochs.)72 541.4 Q
(The duration of an epoch in seconds, EL, is set to be a small fraction)
5.5 E(of TSD, so that decisions to join a channel can be made at a much\
 \214ner granularity than TSD.)72 554.4 Q(A)5.5 E
(standard setting is EL = TSD/20.)72 567.4 Q
(Thus, with the recommended setting of TSD = 10, it is)5.5 E
(RECOMMENDED that EL = 0.5.)72 580.4 Q F1 2.75(3.2.2.5. A)72 623 R -.11
(ve)-1.1 G(rage r).11 E(eception rate)-.198 E F0(There are tw)72 639.6 Q
2.75(oa)-.11 G -.165(ve)-2.97 G
(raged reception rates maintained by the recei).165 E -.165(ve)-.275 G
(r: TRR_P).165 E 2.75(,t)-1.221 G(he true reception rate,)-2.75 E
(and ARR_P)72 652.6 Q 2.75(,t)-1.221 G(he anticipated reception rate.)
-2.75 E(These are used for dif)5.5 E(ferent purposes and thus are)-.275
E(calculated quite dif)72 665.6 Q(ferently)-.275 E 5.5(.R)-.715 G
(ecommended v)-5.5 E
(alues for the \214ltering weights Beta and Zeta are)-.275 E(pro)72
678.6 Q(vided at the end of this subsection.)-.165 E(In start-up mode, \
the true reception rate TRR_P is used to ensure that the recei)72 704.6
Q -.165(ve)-.275 G 2.75(rd).165 G(oes not)-2.75 E
(increase its reception rate too quickly abo)72 717.6 Q .33 -.165(ve i)
-.165 H(ts current reception rate.).165 E(In the transition from start-)
5.5 E(Luby/Go)72 769 Q 259.652(yal Section)-.11 F 2.75(3.2.2.5. [P)2.75
F(age 12])-.165 E EP
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(June 2003)2.75 E(December 2002)103.888 E(up mode to normal operation a\
nd in normal operation, TRR_P is used in setting the slo)72 85 Q 2.75
(ws)-.275 G(tart)-2.75 E 2.75(rate. TRR_P)72 98 R
(is calculated based on the measurement of RR_P)2.75 E 2.75(,w)-1.221 G
(here RR_P is the recei)-2.75 E -.165(ve)-.275 G(r).165 E
(reception rate in pack)72 111 Q(ets per second measured at the be)-.11
E(ginning of an epoch a)-.165 E -.165(ve)-.22 G(raged o).165 E -.165(ve)
-.165 G 2.75(rt).165 G(he)-2.75 E(epoch that just ended.)72 124 Q
(TRR_P is initialized to BCR_P + k*log\(P\)/TSD when the \214rst base)
5.5 E(channel pack)72 137 Q(et of the session arri)-.11 E -.165(ve)-.275
G(s, where k is the PSN of the pack).165 E(et reduced modulo L.)-.11 E
(TRR_P is updated to \(1-Zeta\)*TRR_P + Zeta*RR_P at the be)72 150 Q
(ginning of each epoch after RR_P is)-.165 E(measured for the pre)72 163
Q(vious epoch.)-.275 E
(The anticipated reception rate ARR_P is the recei)72 189 Q -.165(ve)
-.275 G(r').165 E 2.75(se)-.605 G
(stimate of the total instantaneous rate of)-2.75 E
(the currently joined channels.)72 202 Q(It is used to compare ag)5.5 E
(ainst the tar)-.055 E(get rate to decide whether or)-.198 E
(not the recei)72 215 Q -.165(ve)-.275 G 2.75(rs).165 G
(hould increase its reception rate by joining the ne)-2.75 E
(xt higher unjoined layer)-.165 E(.)-.605 E(ARR_P is calculated based o\
n a measurement IRR_P and on the number of joined w)72 228 Q -2.475 -.22
(av e)-.11 H(channels)2.97 E 2.75(NWC. The)72 241 R
(ideal reception rate IRR_P is the reception rate in pack)2.75 E
(ets per second including both)-.11 E(recei)72 254 Q -.165(ve)-.275 G
2.75(da).165 G(nd lost pack)-2.75 E(ets; lik)-.11 E 2.75(eR)-.11 G(R_P)
-2.75 E 2.75(,i)-1.221 G 2.75(ti)-2.75 G 2.75(sm)-2.75 G
(easured at the be)-2.75 E(ginning of the epoch and a)-.165 E -.165(ve)
-.22 G(raged).165 E -.165(ove)72 267 S 2.75(rt).165 G(he pre)-2.75 E
(vious epoch.)-.275 E(ARR_P)5.5 E 2.75(,I)-1.221 G
(RR_P and NWC are updated as follo)-2.75 E(ws:)-.275 E 11(oN)77.5 283.6
S(WC is initialized to 0.)-11 E 11(oW)77.5 300.2 S
(hen the \214rst base channel pack)-11 E(et arri)-.11 E -.165(ve)-.275 G
(s, ARR_P is set to BCR_P + k*log\(P\)/TSD, where).165 E 2.75(ki)94
313.2 S 2.75(st)-2.75 G(he PSN of the pack)-2.75 E(et reduced modulo L.)
-.11 E 11(oA)77.5 329.8 S 2.75(tt)-11 G(he be)-2.75 E
(ginning of each epoch, IRR_P is measured o)-.165 E -.165(ve)-.165 G
2.75(rt).165 G(he pre)-2.75 E(vious epoch and then)-.275 E
(ARR_P is updated to P^\(EL/TSD\)*\(1-Beta\)*ARR_P + Beta*IRR_P)94 342.8
Q(.)-1.221 E 11(oW)77.5 359.4 S(hen a join is made to the ne)-11 E
(xt higher unjoined layer)-.165 E 2.75(,N)-.44 G
(WC is updated to NWC+1 and then)-2.75 E(ARR_P is multiplicati)94 372.4
Q -.165(ve)-.275 G(ly increased by the f).165 E
(actor \(\(1/P\)^\(NWC+1\)-1\)/\(\(1/P\)^NWC-1\).)-.11 E(\(Joins happen\
 at epoch boundaries; this adjustment is in addition to the adjustment \
abo)94 385.4 Q -.165(ve)-.165 G(.\)).165 E 11(oE)77.5 402 S
(ach time a ne)-11 E(xt time slot inde)-.165 E 2.75(xi)-.165 G 2.75(sd)
-2.75 G(etected, ARR_P is additi)-2.75 E -.165(ve)-.275 G
(ly increased by \(1-P\)*BCR_P).165 E
(to account for the change in rate on the base channel.)94 415 Q
(In addition, the bottom layer in the)5.5 E(pre)94 428 Q
(vious time slot has just gone quiescent and thus a message to lea)-.275
E .33 -.165(ve t)-.22 H(his layer has been).165 E(sent, ARR_P is additi)
94 441 Q -.165(ve)-.275 G
(ly decreased by BCR_P and NWC is decremented by 1.).165 E(Consider for\
 the moment what happens if Beta = 0 and ARR_P is an accurate estimate \
of the total)72 457.6 Q(rate of the joined channels.)72 470.6 Q
(The adjustments to ARR_P upon joining and lea)5.5 E(ving w)-.22 E
-2.475 -.22(av e)-.11 H(channels,)2.97 E(with the passage of epochs, an\
d with the detection of time slot changes will then cause ARR_P to)72
483.6 Q(remain an accurate estimate.)72 496.6 Q
(In practice, Beta MUST be positi)5.5 E -.165(ve)-.275 G 2.75(;a).165 G
(llo)-2.75 E(wing an in\215uence of IRR_P)-.275 E(pre)72 509.6 Q -.165
(ve)-.275 G(nts ARR_P from drifting a).165 E -.11(wa)-.165 G 2.75(yf).11
G(rom being an accurate estimate of the total joined rate.)-2.75 E
(The moti)72 535.6 Q -.275(va)-.275 G
(tion for separate estimates TRR_P and ARR_P is as follo).275 E 2.75
(ws. ARR_P)-.275 F(is needed for)2.75 E
(comparison with the TFRC-inspired tar)72 548.6 Q
(get rate because there is no lag before it re\215ects the)-.198 E
(potential rate increase resulting from joining the ne)72 561.6 Q
(xt higher layer and because it measures the)-.165 E
(total possible impact on the netw)72 574.6 Q
(ork since it also includes lost pack)-.11 E 2.75(ets. TRR_P)-.11 F
(is needed because)2.75 E(it re\215ects the rate of data arri)72 587.6 Q
(ving at the recei)-.275 E -.165(ve)-.275 G 2.75(ra).165 G
(nd this is used to ensure that there is not a lar)-2.75 E(ge)-.198 E
-.055(ga)72 600.6 S 2.75(pb).055 G(etween the joined rate and the recei)
-2.75 E(ving rate.)-.275 E(The recommended v)72 626.6 Q
(alues for Beta and Zeta depend on whether the recei)-.275 E -.165(ve)
-.275 G 2.75(ri).165 G 2.75(si)-2.75 G 2.75(ns)-2.75 G(tart-up mode)
-2.75 E(\(SSR_P = in\214nity\).)72 639.6 Q(In start-up mode, it is RECO\
MMENDED that Beta = \(1 - P^\(0.25\)\)/2 and)5.5 E
(Zeta = sqrt\(P\)/\(1 + sqrt\(P\)\).)72 652.6 Q
(In normal operation, it is RECOMMENDED that Beta = 1 -)5.5 E
(\(P/\(1+P\)\)^\(EL/TSD\) and Zeta = 2*EL/\(4+TSD\).)72 665.6 Q(Luby/Go)
72 769 Q 259.652(yal Section)-.11 F 2.75(3.2.2.5. [P)2.75 F(age 13])
-.165 E EP
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(June 2003)2.75 E(December 2002)103.888 E/F1 11/Times-Bold@0 SF 2.75
(3.2.2.6. Slo)72 85 R 2.75(ws)-.11 G(tart)-2.75 E F0(WEBRC uses a slo)72
101.6 Q 2.75(ws)-.275 G
(tart mechanism to quickly ramp up its rate at both the be)-2.75 E
(ginning of the)-.165 E(session and in the middle of a session when the\
 rate drops precipitously)72 114.6 Q 5.5(.T)-.715 G 2.75(oe)-6.38 G
(nact this, the)-2.75 E(recei)72 127.6 Q -.165(ve)-.275 G 2.75(rm).165 G
(aintains the follo)-2.75 E(wing parameters:)-.275 E 11(oS)77.5 144.2 S
(SMINR_P is the minimum allo)-11 E(wed slo)-.275 E 2.75(ws)-.275 G
(tart threshold rate in pack)-2.75 E(ets per second.)-.11 E(The)5.5 E
(recommended v)94 157.2 Q(alue for SSMINR_P is BCR_P*\(1+1/P+1/P^2\).)
-.275 E 11(oS)77.5 173.8 S(SR_P is the slo)-11 E 2.75(ws)-.275 G
(tart threshold rate in pack)-2.75 E(ets per second.)-.11 E
(It is adjusted at the be)5.5 E(ginning)-.165 E(of loss e)94 186.8 Q
-.165(ve)-.275 G(nts as described in Section 3.2.3.4. SSR_P is initiali\
zed to in\214nity and is \214rst set).165 E(to a \214nite v)94 199.8 Q
(alue when the recei)-.275 E -.165(ve)-.275 G 2.75(rl).165 G(ea)-2.75 E
-.165(ve)-.22 G 2.75(st).165 G
(he initial start-up period as described belo)-2.75 E -.715(w.)-.275 G
(At the be)72 216.4 Q(ginning of a session, the recei)-.165 E -.165(ve)
-.275 G 2.75(rc).165 G(annot compute a meaningful tar)-2.75 E
(get rate from its)-.198 E 2.75(measurements. Thus,)72 229.4 R
(it uses SSR_P = in\214nity until one of the follo)2.75 E(wing e)-.275 E
-.165(ve)-.275 G(nts causes an end to).165 E(this start-up mode:)72
242.4 Q 11(oA)77.5 259 S(pack)-8.25 E(et loss is detected.)-.11 E
(In this case the v)5.5 E(alue of SSR_P is updated to max{SSMINR_P)-.275
E(,)-1.221 E(P*TRR_P} as with the be)94 272 Q(ginning of an)-.165 E 2.75
(yo)-.165 G(ther loss e)-2.75 E -.165(ve)-.275 G(nt.).165 E 11(oA)77.5
288.6 S(sharp increase in MR)-8.25 E(TT is detected.)-.66 E
(While SSR_P = in\214nity the recei)5.5 E -.165(ve)-.275 G 2.75(rM).165
G(UST compute,)-2.75 E(in the notation of Section 3.2.2.2, dif)94 301.6
Q(ferences in successi)-.275 E .33 -.165(ve m)-.275 H
(easurements of \(FirstT).165 E(ime-)-.385 E(JoinT)94 314.6 Q
(ime\) from successi)-.385 E .33 -.165(ve w)-.275 H -2.475 -.22(av e)
.055 H 2.75(sa).22 G(nd MUST set SSR_P to max{SSMINR_P)-2.75 E 2.75(,P)
-1.221 G(*TRR_P})-2.75 E(when a lar)94 327.6 Q(ge increase in \(FirstT)
-.198 E(ime-JoinT)-.385 E(ime\) is observ)-.385 E 2.75(ed. It)-.165 F
(is RECOMMENDED that an)2.75 E(increase in \(FirstT)94 340.6 Q
(ime-JoinT)-.385 E(ime\) be considered lar)-.385 E(ge if it e)-.198 E
(xceeds)-.165 E(\(1-P^\(NWC+1\)\)/\(P*log\(P\)\) / ARR_P)94 353.6 Q(.)
-1.221 E 11(oT)77.5 370.2 S(he maximum reception rate is reached.)-11 E
(When SSR_P = in\214nity)5.5 E 2.75(,i)-.715 G(f)-2.75 E
(\(P^\(-NWC-2\)-1\)/\(P^\(-NWC-1\)-1\)*ARR_P e)94 383.2 Q
(xceeds MRR_P or SR_P)-.165 E 2.75(,t)-1.221 G(he recei)-2.75 E -.165
(ve)-.275 G 2.75(rM).165 G(UST set)-2.75 E(SSR_P to max{SSMINR_P)94
396.2 Q 2.75(,T)-1.221 G(RR_P}.)-2.75 E 11(oT)77.5 412.8 S
(RR_P is not increasing consistent with the last join of a w)-11 E
-2.475 -.22(av e)-.11 H 2.75(channel. While)2.97 F(SSR_P =)2.75 E
(in\214nity)94 425.8 Q 2.75(,i)-.715 G 2.75(ti)-2.75 G 2.75(sR)-2.75 G
(ECOMMENDED that the recei)-2.75 E -.165(ve)-.275 G 2.75(rw).165 G
(ait at least one full epoch after the \214rst)-2.86 E(pack)94 438.8 Q
(et of a w)-.11 E -2.475 -.22(av e)-.11 H(is recei)2.97 E -.165(ve)-.275
G 2.75(db).165 G(efore joining the ne)-2.75 E(xt w)-.165 E -2.475 -.22
(av e)-.11 H 5.5(.I).22 G 2.75(ft)-5.5 G(he TRR_P after that full epoch)
-2.75 E(is greatly belo)94 451.8 Q 2.75(wA)-.275 G(RR_P the recei)-2.75
E -.165(ve)-.275 G 2.75(rS).165 G(HOULD NO)-2.75 E 2.75(Tj)-.44 G
(oin and SHOULD then set SSR_P to)-2.75 E(max{SSMINR_P)94 464.8 Q 2.75
(,T)-1.221 G 2.75(RR_P}. It)-2.75 F
(is RECOMMENDED that TRR_P be considered greatly)2.75 E(belo)94 477.8 Q
2.75(wA)-.275 G(RR_P if TRR_P < c * ARR_P - 2/EL, where c = Zeta +)-2.75
E(\(1-Zeta\)*\(P^\(-EL/TSD\)\)*\(Zeta + \(1-Zeta\)*sqrt\(P\)*\(P^\(-EL/\
TSD\)\)\)/g with g =)94 490.8 Q(\(P^\(-NWC-1\)-1\)/\(P^\(-NWC\)-1\).)94
503.8 Q(In an)72 520.4 Q 2.75(yo)-.165 G 2.75(ft)-2.75 G
(hese four cases, the v)-2.75 E
(ariables associated with LOSSP are reset to mak)-.275 E 2.75(eR)-.11 G
(EQN,)-2.75 E(calculated as in Section 3.2.2.3 with the current v)72
533.4 Q(alue of AR)-.275 E(TT)-.66 E 2.75(,e)-.814 G(qual TRR_P)-2.75 E
(.)-1.221 E F1 2.75(3.2.2.7. T)72 576 R(ar)-1.012 E(get rate)-.11 E F0
(In typical operation, SSR_P has a \214nite v)72 592.6 Q
(alue and the tar)-.275 E(get rate TRA)-.198 E(TE is computed as TRA)
-1.221 E(TE)-1.221 E 2.75(=m)72 605.6 S(in{max{SSR_P)-2.75 E 2.75(,R)
-1.221 G(EQN}, MRR_P}.)-2.75 E(When SSR_P = in\214nity)5.5 E 2.75(,T)
-.715 G(RA)-2.75 E(TE is computed as TRA)-1.221 E(TE)-1.221 E 2.75(=m)72
618.6 S(in{4*TRR_P)-2.75 E 2.75(,M)-1.221 G(RR_P}.)-2.75 E F1 2.75
(3.2.3. Recei)72 661.2 R -.11(ve)-.11 G 2.75(re).11 G -.11(ve)-2.915 G
(nts).11 E F0(There are v)72 677.8 Q(arious recei)-.275 E -.165(ve)-.275
G 2.75(re).165 G -.165(ve)-3.025 G
(nts, some of which are triggered by the passing of time on the).165 E
(recei)72 690.8 Q -.165(ve)-.275 G .88 -.44(r, a).165 H(nd others by e)
.44 E -.165(ve)-.275 G(nts such as pack).165 E
(et reception, detection of pack)-.11 E(et loss, reception of a)-.11 E
(\214rst pack)72 703.8 Q(et from a channel, and e)-.11 E
(xceptional time-outs.)-.165 E(Luby/Go)72 769 Q 267.902(yal Section)-.11
F 2.75(3.2.3. [P)2.75 F(age 14])-.165 E EP
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(3.2.3.1. P)72 85 R(ack)-.11 E(et r)-.11 E(eception)-.198 E F0
(Most pack)72 101.6 Q(et reception e)-.11 E -.165(ve)-.275 G
(nts require the recei).165 E -.165(ve)-.275 G 2.75(rt).165 G 2.75(om)
-2.75 G(erely re)-2.75 E(gister the reception for later)-.165 E(calcula\
tion of RR_P and IRR_P \(see Section 3.2.2.5\) and increment W for late\
r calculation of)72 114.6 Q(LOSSP \(see Section 3.2.2.1\). Additional a\
ctions, described in the follo)72 127.6 Q(wing three subsections, are)
-.275 E(required if the pack)72 140.6 Q(et is the \214rst pack)-.11 E
(et recei)-.11 E -.165(ve)-.275 G 2.75(di).165 G 2.75(nr)-2.75 G
(esponse to a join operation, the CTSI of the)-2.75 E(pack)72 153.6 Q
(et indicates a time slot change, or the CN and PSN of the pack)-.11 E
(et indicate a pack)-.11 E(et loss.)-.11 E F1 2.75(3.2.3.2. First)72
196.2 R(pack)2.75 E(et after join)-.11 E F0
(When channel i is the most recently joined channel and the Boolean v)72
212.8 Q(ariable JOINING is true,)-.275 E(the reception of a pack)72
225.8 Q(et with PSN = i is a special e)-.11 E -.165(ve)-.275 G
(nt because it is the \214rst pack).165 E(et recei)-.11 E -.165(ve)-.275
G 2.75(di).165 G(n)-2.75 E(response to the most recent join.)72 238.8 Q
(MR)5.5 E(TT is calculated and AR)-.66 E
(TT and V are updated as described)-.66 E
(in Section 3.2.2.2, and JOINING is set to f)72 251.8 Q 2.75(alse. The)
-.11 F(\214rst recei)2.75 E -.165(ve)-.275 G 2.75(dp).165 G(ack)-2.75 E
(et of the session)-.11 E(furthermore necessitates initialization of AR\
R_P and TRR_P as described in Section 3.2.2.5.)72 264.8 Q F1 2.75
(3.2.3.3. T)72 294.4 R(ime slot change)-.198 E F0(This is an e)72 311 Q
-.165(ve)-.275 G(nt that is triggered by the reception of a pack).165 E
(et with a CTSI v)-.11 E(alue that is one lar)-.275 E(ger)-.198 E
(modulo T than the pre)72 324 Q(vious CTSI v)-.275 E 2.75(alue. When)
-.275 F 2.75(ap)2.75 G(ack)-2.75 E(et with a ne)-.11 E 2.75(wC)-.275 G
(TSI = i is recei)-2.75 E -.165(ve)-.275 G(d, a lea).165 E -.165(ve)-.22
G(is sent for the lo)72 337 Q(west layer in the pre)-.275 E
(vious time slot, i.e., w)-.275 E -2.475 -.22(av e)-.11 H
(channel i-1 modulo T)2.97 E 2.75(,N)-.814 G(WC is)-2.75 E(updated to N\
WC-1, and ARR_P is updated to ARR_P - P*BCR_P as described in Section)72
350 Q(3.2.2.5. If the channel for which the lea)72 363 Q .33 -.165(ve i)
-.22 H 2.75(ss).165 G(ent is also the most recently joined w)-2.75 E
-2.475 -.22(av e)-.11 H(channel)2.97 E
(and JOINING is true, then JOINING is set to f)72 376 Q(alse.)-.11 E
(It is possible due to pack)72 402 Q(et reordering for some pack)-.11 E
(ets from the pre)-.11 E(vious time slot to be recei)-.275 E -.165(ve)
-.275 G(d).165 E(after pack)72 415 Q(ets from the current time slot.)
-.11 E(It is RECOMMENDED that measures be put into place)5.5 E
(to handle this situation appropriately)72 428 Q 2.75(,i)-.715 G
(.e., to not trigger a time slot change in this situation.)-2.75 E(One)
5.5 E(simple mechanism for this is as follo)72 441 Q
(ws: Compute the dif)-.275 E(ference i-j modulo T)-.275 E 2.75(,w)-.814
G(here i is the CTSI)-2.75 E(of the recei)72 454 Q -.165(ve)-.275 G 2.75
(dp).165 G(ack)-2.75 E(et and j is the current CTSI of the recei)-.11 E
-.165(ve)-.275 G 3.96 -.605(r. A).165 H(dif)3.355 E
(ference of zero is, of course,)-.275 E(not a time slot change.)72 467 Q
(In addition, a v)5.5 E(ery lar)-.165 E(ge dif)-.198 E(ference, for e)
-.275 E(xample a dif)-.165 E(ference lar)-.275 E(ger than)-.198 E -1.012
(T-)72 480 S(Q/2, should also not trigger a time slot change.)1.012 E F1
2.75(3.2.3.4. Loss)72 522.6 R -2.53 -.165(ev e)2.75 H(nt).165 E F0
(Each time the recei)72 539.2 Q -.165(ve)-.275 G 2.75(rd).165 G
(etects a lost pack)-2.75 E
(et \(based on the sequence numbers in the pack)-.11 E(ets scoped)-.11 E
(by the channel number\), the recei)72 552.2 Q -.165(ve)-.275 G 2.75(rr)
.165 G(ecords the start of a ne)-2.75 E 2.75(wl)-.275 G(oss e)-2.75 E
-.165(ve)-.275 G(nt, and sets a Boolean).165 E -.275(va)72 565.2 S
(riable LOSS_EVENT to true that will automatically reset to f).275 E
(alse after AR)-.11 E(TT seconds.)-.66 E(All)5.5 E(subsequent pack)72
578.2 Q(et loss for a period of AR)-.11 E
(TT seconds is considered as part of the same loss e)-.66 E -.165(ve)
-.275 G(nt.).165 E(When a start of a loss e)72 591.2 Q -.165(ve)-.275 G
(nt is detected, the v).165 E(alue of SSR_P is updated to max{SSMINR_P)
-.275 E(,)-1.221 E(P*TRR_P}.)72 604.2 Q
(It is RECOMMENDED that the recei)72 630.2 Q -.165(ve)-.275 G 2.75(ra)
.165 G(ccount for simple misordering of pack)-2.75 E(ets without)-.11 E
(inferring a loss.)72 643.2 Q F1 2.75(3.2.3.5. Epoch)72 685.8 R(change)
2.75 E F0(This is an e)72 702.4 Q -.165(ve)-.275 G
(nt that is triggered by the passage of time at the recei).165 E -.165
(ve)-.275 G .88 -.44(r, w).165 H(hich occurs each EL).44 E 2.75
(seconds. When)72 715.4 R(this happens, TRR_P and ARR_P are computed as\
 described in Section 3.2.2.5.)2.75 E(Luby/Go)72 769 Q 259.652
(yal Section)-.11 F 2.75(3.2.3.5. [P)2.75 F(age 15])-.165 E EP
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(June 2003)2.75 E(December 2002)103.888 E(Immediately after these updat\
es, a decision is made about whether to join the ne)72 85 Q
(xt higher layer as)-.165 E(described in Section 3.2.3.6.)72 98 Q/F1 11
/Times-Bold@0 SF 2.75(3.2.3.6. J)72 127.6 R(oin the next higher lay)
-.165 E(er)-.11 E F0(At the be)72 144.2 Q
(ginning of each epoch, after updating the v)-.165 E
(alues of ARR_P and TRR_P as described in)-.275 E
(Section 3.2.2.5, the recei)72 157.2 Q -.165(ve)-.275 G 2.75(rd).165 G
(ecides whether or not to join the ne)-2.75 E(xt higher layer as follo)
-.165 E(ws:)-.275 E 11(oI)77.5 173.8 S 2.75(ft)-11 G
(he \214rst base channel pack)-2.75 E(et has not yet arri)-.11 E -.165
(ve)-.275 G 2.75(dt).165 G(he recei)-2.75 E -.165(ve)-.275 G 2.75(rd)
.165 G(oes not join.)-2.75 E 11(oI)77.5 190.4 S 2.75(ft)-11 G
(here is a loss e)-2.75 E -.165(ve)-.275 G
(nt in progress \(LOSS_EVENT = true\) the recei).165 E -.165(ve)-.275 G
2.75(rd).165 G(oes not join.)-2.75 E 11(oI)77.5 207 S 2.75(faj)-11 G
(oin of a channel is in progress \(JOINING = true\), the recei)-2.75 E
-.165(ve)-.275 G 2.75(rd).165 G(oes not join.)-2.75 E 11(oI)77.5 223.6 S
2.75(fN)-11 G(WC = N the recei)-2.75 E -.165(ve)-.275 G 2.75(rd).165 G
(oes not join.)-2.75 E 11(oI)77.5 240.2 S 2.75(ft)-11 G(he recei)-2.75 E
-.165(ve)-.275 G 2.75(ri).165 G 2.75(se)-2.75 G(mplo)-2.75 E
(ying the OPTION)-.11 E(AL rule described in Section 3.2.2.6, SSR_P =)
-.385 E(in\214nity)94 253.2 Q 2.75(,a)-.715 G
(nd a full epoch has not passed since the \214rst pack)-2.75 E(et arri)
-.11 E -.275(va)-.275 G 2.75(lo).275 G 2.75(nt)-2.75 G(he most recently)
-2.75 E(joined w)94 266.2 Q -2.475 -.22(av e)-.11 H
(channel then the recei)2.97 E -.165(ve)-.275 G 2.75(rd).165 G
(oes not join.)-2.75 E 11(oI)77.5 282.8 S 2.75(ft)-11 G(he recei)-2.75 E
-.165(ve)-.275 G 2.75(ri).165 G 2.75(se)-2.75 G(mplo)-2.75 E
(ying the OPTION)-.11 E(AL rule described in Section 3.2.2.6, SSR_P =)
-.385 E(in\214nity)94 295.8 Q 2.75(,a)-.715 G
(nd a full epoch has passed since the \214rst pack)-2.75 E(et arri)-.11
E -.275(va)-.275 G 2.75(lo).275 G 2.75(nt)-2.75 G
(he most recently joined)-2.75 E -.11(wa)94 308.8 S .33 -.165(ve c)-.11
H(hannel, then the recei).165 E -.165(ve)-.275 G 2.75(rc).165 G
(hecks if TRR_P is greatly belo)-2.75 E 2.75(wA)-.275 G
(RR_P as described in)-2.75 E(Section 3.2.2.6. If TRR_P is greatly belo)
94 321.8 Q 2.75(wA)-.275 G(RR_P the recei)-2.75 E -.165(ve)-.275 G 2.75
(rd).165 G(oes not join.)-2.75 E 11(oT)77.5 338.4 S(he recei)-11 E -.165
(ve)-.275 G 2.75(rc).165 G
(alculates REQN as described in Section 3.2.2.3.)-2.75 E 11(oT)77.5 355
S(he recei)-11 E -.165(ve)-.275 G 2.75(rc).165 G(alculates TRA)-2.75 E
(TE as described in Section 3.2.2.7.)-1.221 E 11(oI)77.5 371.6 S 2.75
(ft)-11 G(he sender is not sending at constant aggre)-2.75 E -.055(ga)
-.165 G(te rate and TRA).055 E(TE <)-1.221 E
(ARR_P*\(\(1/P\)^{NWC+2}-1\)/\(\(1/P\)^{NWC+1}-1\), the recei)94 384.6 Q
-.165(ve)-.275 G 2.75(rd).165 G(oes not join.)-2.75 E(If the sender)5.5
E(is sending at constant aggre)94 397.6 Q -.055(ga)-.165 G
(te rate and neither TRA).055 E(TE >=)-1.221 E
(ARR_P*\(\(1/P\)^{NWC+2}-1\)/\(\(1/P\)^{NWC+1}-1\) nor TRA)94 410.6 Q
(TE >= SR_P is true, the recei)-1.221 E -.165(ve)-.275 G(r).165 E
(does not join.)94 423.6 Q 11(oI)77.5 440.2 S 2.75(ft)-11 G
(he sender is producing constant aggre)-2.75 E -.055(ga)-.165 G
(te rate and TRA).055 E(TE >= SR_P)-1.221 E 2.75(,t)-1.221 G(he recei)
-2.75 E -.165(ve)-.275 G 2.75(rj).165 G(oins)-2.75 E(the ne)94 453.2 Q
(xt w)-.165 E -2.475 -.22(av e)-.11 H 2.75(channel. Otherwise)2.97 F
(if SSR_P is \214nite the recei)2.75 E -.165(ve)-.275 G 2.75(rM).165 G
2.31 -1.155(AY a)-2.75 H(pply one additional)1.155 E(OPTION)94 466.2 Q
(AL check before deciding to join.)-.385 E
(It is RECOMMENDED that the recei)94 492.2 Q -.165(ve)-.275 G 2.75(rn)
.165 G(ot join if the v)-2.75 E(alue of RR_P is not suf)-.275 E
(\214ciently)-.275 E(lo)94 505.2 Q(wer than the maximum v)-.275 E
(alue of RR_P observ)-.275 E(ed since the last join.)-.165 E(It is)5.5 E
(RECOMMENDED that RR_P is suf)94 518.2 Q(\214ciently lo)-.275 E 2.75(wt)
-.275 G 2.75(oa)-2.75 G(llo)-2.75 E 2.75(waj)-.275 G(oin if RR_P <=)
-2.75 E(max{RRmax-2/EL,P*RRmax}, where RRmax is the maximum measured RR\
_P since the)94 531.2 Q(last join.)94 544.2 Q(If the recei)94 570.2 Q
-.165(ve)-.275 G 2.75(rd).165 G(oes not join because RR_P is not suf)
-2.75 E(\214ciently small then a v)-.275 E(alue of LOSSP is)-.275 E
(calculated so as to mak)94 583.2 Q 2.75(et)-.11 G(he v)-2.75 E
(alue of the REQN equation gi)-.275 E -.165(ve)-.275 G 2.75(ni).165 G
2.75(nS)-2.75 G(ection 3.2.2.3 e)-2.75 E -.275(va)-.275 G(luate to).275
E(ARR_P*\(\(1/P\)^\(NWC+2\)-1\)/\(\(1/P\)^\(NWC+1\)-1\) with respect to\
 the current v)94 596.2 Q(alue of)-.275 E(ARR_P)94 609.2 Q 5.5(.T)-1.221
G(hen, the v)-5.5 E
(ariables associated with LOSSP are reset based on this calculated v)
-.275 E(alue)-.275 E
(of LOSSP as described at the end of Section 3.2.2.1.)94 622.2 Q
(Suppose the recei)72 638.8 Q -.165(ve)-.275 G 2.75(rh).165 G
(as decided to join and CTSI = i.)-2.75 E(The recei)5.5 E -.165(ve)-.275
G 2.75(rj).165 G(oins the ne)-2.75 E(xt higher w)-.165 E -2.475 -.22
(av e)-.11 H(channel, i.e., the w)72 651.8 Q -2.475 -.22(av e)-.11 H
(channel with CN = i+NWC modulo T)2.97 E 2.75(,i)-.814 G
(ncrements NWC by 1, and then)-2.75 E(updates ARR to ARR_P*\(\(1/P\)^{N\
WC+1}-1\)/\(\(1/P\)^NWC-1\) as described in Section 3.2.2.5.)72 664.8 Q
(The time of the join is recorded for use in updating AR)72 677.8 Q
(TT as described in Section 3.2.2.2.)-.66 E(Luby/Go)72 769 Q 259.652
(yal Section)-.11 F 2.75(3.2.3.6. [P)2.75 F(age 16])-.165 E EP
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(June 2003)2.75 E(December 2002)103.888 E/F1 11/Times-Bold@0 SF 2.75
(3.2.3.7. J)72 85 R(oin timeout)-.165 E F0(When no pack)72 101.6 Q
(et arri)-.11 E -.165(ve)-.275 G 2.75(si).165 G 2.75(nr)-2.75 G(esponse\
 to the join of channel for a long period of time, the join times)-2.75
E 2.75(out. The)72 114.6 R(recei)2.75 E -.165(ve)-.275 G 2.75(rs).165 G
(ets JOINING to f)-2.75 E(alse, updates ARR to)-.11 E(ARR_P*\(\(1/P\)^N\
WC-1\)/\(\(1/P\)^{NWC+1}-1\), and then decrements NWC by 1.)72 127.6 Q
(The RECOMMENDED threshold for a join timeout is max{2*V/AR)72 153.6 Q
(TT)-.66 E(,10*AR)-.814 E(TT} seconds.)-.66 E F1 2.75
(3.2.3.8. Exceptional)72 196.2 R(timeouts)2.75 E F0
(These are timeouts when the pack)72 212.8 Q(et reception beha)-.11 E
(vior is f)-.22 E(ar from what it should be and these)-.11 E
(MUST trigger the recei)72 225.8 Q -.165(ve)-.275 G 2.75(rt).165 G 2.75
(ol)-2.75 G(ea)-2.75 E .33 -.165(ve t)-.22 H(he session.).165 E
(Exceptional timeouts include)5.5 E 11(oN)77.5 242.4 S 2.75(op)-11 G
(ack)-2.75 E(ets are recei)-.11 E -.165(ve)-.275 G 2.75(df).165 G
(or a long period.)-2.75 E 2.75(AR)5.5 G
(ECOMMENDED threshold is max{10,TSD})-2.75 E(seconds.)94 255.4 Q 11(oT)
77.5 272 S(here is no change in time slot inde)-11 E 2.75(xf)-.165 G
(or a long period.)-2.75 E 2.75(AR)5.5 G(ECOMMENDED threshold is)-2.75 E
(max{20,2*TSD} seconds.)94 285 Q F1(4.)72 327.6 Q/F2 14/Times-Bold@0 SF
-.35(Ap)5.5 G(plicability Statement).35 E F0(WEBRC is intended to be a \
congestion control scheme that can be used in a complete protocol)72
344.2 Q(instantiation that deli)72 357.2 Q -.165(ve)-.275 G
(rs objects and streams \(both reliable content deli).165 E -.165(ve)
-.275 G(ry and streaming of).165 E(multimedia information\).)72 370.2 Q
(WEBRC is most applicable for deli)5.5 E -.165(ve)-.275 G
(ry of objects or streams of).165 E(substantial length, i.e., objects o\
r streams that range in length from hundreds of kilobytes to man)72
383.2 Q(y)-.165 E(gig)72 396.2 Q(abytes, and whose transfer time is on \
the order of tens of seconds or more.)-.055 E F1(4.1.)72 435.2 Q/F3 13
/Times-Bold@0 SF(En)5.5 E(vir)-.52 E(onmental Requir)-.234 E
(ements and Considerations)-.234 E F0
(WEBRC can be used with both multicast and unicast netw)72 464.8 Q 2.75
(orks. Ho)-.11 F(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H
(he scope of this).44 E(document is limited to multicast.)72 477.8 Q
(WEBRC requires connecti)5.5 E(vity between a sender and recei)-.275 E
-.165(ve)-.275 G(rs,).165 E -.22(bu)72 490.8 S 2.75(td).22 G
(oes not require connecti)-2.75 E(vity from recei)-.275 E -.165(ve)-.275
G(rs to the sender).165 E(.)-.605 E(WEBRC inherently w)72 516.8 Q
(orks with all types of netw)-.11 E(orks, including LANs, W)-.11 E
(ANs, Intranets, the)-1.32 E(Internet, asymmetric netw)72 529.8 Q
(orks, wireless netw)-.11 E(orks, and satellite netw)-.11 E 2.75
(orks. Thus,)-.11 F(the inherent ra)2.75 E(w)-.165 E
(scalability of WEBRC is unlimited.)72 542.8 Q(Ho)5.5 E(we)-.275 E -.165
(ve)-.275 G .88 -.44(r, i).165 H 2.75(ns).44 G(ome netw)-2.75 E(ork en)
-.11 E(vironments v)-.44 E(arying reception)-.275 E(rates to recei)72
555.8 Q -.165(ve)-.275 G(rs may not be adv).165 E 2.75(antageous. F)
-.275 F(or e)-.165 E(xample, the netw)-.165 E(ork may ha)-.11 E .33
-.165(ve a d)-.22 H(edicated \214x).165 E(ed)-.165 E
(amount of bandwidth allocated to the session and there may be no ef)72
568.8 Q(fecti)-.275 E .33 -.165(ve w)-.275 H(ay for recei).055 E -.165
(ve)-.275 G(rs to).165 E(dynamically v)72 581.8 Q
(ary the set of channels the)-.275 E 2.75(ya)-.165 G
(re joined to, e.g., in a satellite netw)-2.75 E(ork.)-.11 E(Recei)72
607.8 Q -.165(ve)-.275 G(rs join and lea).165 E .33 -.165(ve c)-.22 H
(hannels using the appropriate multicast join and lea).165 E .33 -.165
(ve m)-.22 H 2.75(essages. F).165 F(or)-.165 E
(IPv4 multicast, IGMP messages are used by recei)72 620.8 Q -.165(ve)
-.275 G(rs to join and lea).165 E .33 -.165(ve c)-.22 H 2.75(hannels. F)
.165 F(or IPv6,)-.165 E(MLDv2 messages are used by recei)72 633.8 Q
-.165(ve)-.275 G(rs to join and lea).165 E .33 -.165(ve c)-.22 H 2.75
(hannels. This).165 F(is the only dependenc)2.75 E(y)-.165 E
(of WEBRC on the IP v)72 646.8 Q(ersion.)-.165 E(WEBRC requires recei)72
672.8 Q -.165(ve)-.275 G
(rs to be able to uniquely identify and demultiple).165 E 2.75(xp)-.165
G(ack)-2.75 E(ets associated)-.11 E(with a session in order to ef)72
685.8 Q(fecti)-.275 E -.165(ve)-.275 G(ly perform congestion control o)
.165 E -.165(ve)-.165 G 2.75(ra).165 G(ll pack)-2.75 E
(ets associated with)-.11 E(the session.)72 698.8 Q(Ho)5.5 E 2.75(wr)
-.275 G(ecei)-2.75 E -.165(ve)-.275 G(rs achie).165 E .33 -.165(ve t)
-.275 H(his is outside the scope of this document.).165 E
(WEBRC is presumed to be used with an underlying netw)72 724.8 Q
(ork or transport service that is a `)-.11 E(`best)-.814 E(Luby/Go)72
769 Q 276.152(yal Section)-.11 F 2.75(4.1. [P)2.75 F(age 17])-.165 E EP
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(June 2003)2.75 E(December 2002)103.888 E(ef)72 85 Q(fort')-.275 E 2.75
('s)-.814 G(ervice that does not guarantee pack)-2.75 E
(et reception, pack)-.11 E(et reception order)-.11 E 2.75(,a)-.44 G
(nd which does)-2.75 E(not ha)72 98 Q .33 -.165(ve a)-.22 H .33 -.165
(ny s).165 H(upport for \215o).165 E 2.75(wo)-.275 G 2.75(rc)-2.75 G
(ongestion control.)-2.75 E -.165(Fo)5.5 G 2.75(re).165 G
(xample, the An)-2.915 E(y-Source Multicast)-.165 E(\(ASM\) model of IP\
 multicast as de\214ned in RFC1112 [5] is such a best ef)72 111 Q
(fort netw)-.275 E(ork service.)-.11 E(While the basic service pro)72
124 Q(vided by RFC1112 is lar)-.165 E(gely scalable, pro)-.198 E
(viding congestion control or)-.165 E
(reliability should be done carefully to a)72 137 Q -.22(vo)-.22 G
(id se).22 E -.165(ve)-.275 G
(re scalability limitations, especially in the).165 E
(presence of heterogeneous sets of recei)72 150 Q -.165(ve)-.275 G(rs.)
.165 E(There are currently tw)72 176 Q 2.75(om)-.11 G
(odels of multicast deli)-2.75 E -.165(ve)-.275 G(ry).165 E 2.75(,t)
-.715 G(he An)-2.75 E(y-Source Multicast \(ASM\) model as)-.165 E(de\
\214ned in RFC1112 [5] and the Source-Speci\214c Multicast \(SSM\) mode\
l as de\214ned in [8].)72 189 Q(WEBRC w)72 202 Q
(orks with both multicast models, b)-.11 E(ut in a slightly dif)-.22 E
(ferent w)-.275 E(ay with some)-.11 E(what)-.275 E(dif)72 215 Q
(ferent en)-.275 E(vironmental concerns.)-.44 E
(When using ASM, a sender S sends pack)5.5 E(ets to a multicast)-.11 E(\
group G, and the WEBRC channel address consists of the pair \(S,G\), wh\
ere S is the IP address of)72 228 Q
(the sender and G is a multicast group address.)72 241 Q
(When using SSM, a sender S sends pack)5.5 E(ets to an)-.11 E(SSM chann\
el \(S,G\), and the WEBRC channel address coincides with the SSM channe\
l address.)72 254 Q 2.75(As)72 280 S
(ender can locally allocate unique SSM channel addresses, and this mak)
-2.75 E(es allocation of)-.11 E(channel addresses easy with SSM.)72 293
Q 1.76 -.88(To a)5.5 H
(llocate channel addresses using ASM, the sender must).88 E(uniquely ch\
ose the ASM multicast group address across the scope of the group, and \
this mak)72 306 Q(es)-.11 E
(allocation of WEBRC channel addresses more dif)72 319 Q
(\214cult with ASM.)-.275 E(This is an issue for WEBRC)5.5 E(because se)
72 332 Q -.165(ve)-.275 G(ral channels are used per session.).165 E
(WEBRC channels and SSM channels coincide, and thus the recei)72 358 Q
-.165(ve)-.275 G 2.75(rw).165 G(ill only recei)-2.75 E .33 -.165(ve p)
-.275 H(ack).165 E(ets)-.11 E(sent to the requested WEBRC channel.)72
371 Q -.44(Wi)5.5 G(th ASM, the recei).44 E -.165(ve)-.275 G 2.75(rj)
.165 G(oins a channel by joining a)-2.75 E
(multicast group G, and all pack)72 384 Q(ets sent to G, re)-.11 E -.055
(ga)-.165 G(rdless of the sender).055 E 2.75(,m)-.44 G(ay be recei)-2.75
E -.165(ve)-.275 G 2.75(db).165 G 2.75(yt)-2.75 G(he)-2.75 E(recei)72
397 Q -.165(ve)-.275 G 3.96 -.605(r. T).165 H
(hus, SSM has compelling security adv).605 E(antages o)-.275 E -.165(ve)
-.165 G 2.75(rA).165 G(SM for pre)-2.75 E -.165(ve)-.275 G
(ntion of denial of).165 E(service attacks.)72 410 Q
(In either case, recei)5.5 E -.165(ve)-.275 G
(rs SHOULD use mechanisms to \214lter out pack).165 E(ets from)-.11 E
(unw)72 423 Q(anted sources.)-.11 E(WEBRC assumes that the pack)72 449 Q
(et route between the sender and a particular recei)-.11 E -.165(ve)
-.275 G 2.75(ri).165 G 2.75(st)-2.75 G(he same)-2.75 E
(for all channels associated with a session.)72 462 Q -.165(Fo)5.5 G
2.75(rS).165 G(SM this assumption is true because the multicast)-2.75 E
(tree is a shortest path tree from each recei)72 475 Q -.165(ve)-.275 G
2.75(rt).165 G 2.75(ot)-2.75 G
(he sender and generally this path changes)-2.75 E(infrequently)72 488 Q
5.5(.F)-.715 G
(or ASM there are some issues that if not properly considered may in)
-5.665 E -.275(va)-.44 G(lidate this).275 E 2.75(assumption. W)72 501 R
(ith ASM, the pack)-.44 E(et route between the sender and recei)-.11 E
-.165(ve)-.275 G(rs may initially be).165 E(through the Rendezv)72 514 Q
(ous Point \(RP\) and then switch o)-.22 E -.165(ve)-.165 G 2.75(rt).165
G 2.75(ot)-2.75 G(he shortest path to the sender as)-2.75 E(pack)72 527
Q(ets start \215o)-.11 E(wing in a channel.)-.275 E
(The \214rst issue is that the RP may not be the same for all)5.5 E
(channels associated with a session, and thus the \214rst pack)72 540 Q
(ets sent to the channels may follo)-.11 E 2.75(wa)-.275 G
(route that depends on the RP of the channel.)72 553 Q
(This depends on the RP con\214guration for the sender)5.5 E(.)-.605 E
(If the sender re)72 566 Q(gisters all channels associated with the ses\
sion with the same RP then the)-.165 E(assumption is true, b)72 579 Q
(ut if the sender re)-.22 E(gisters dif)-.165 E
(ferent channels with dif)-.275 E(ferent RPs then the)-.275 E
(assumption may not be true.)72 592 Q
(Thus, it is RECOMMENDED that the sender re)5.5 E(gister all channels)
-.165 E(associated with a session with the same RP)72 605 Q 5.5(.A)
-1.221 G(nother issue is that when the channel switches o)-5.5 E -.165
(ve)-.165 G(r).165 E(from the RP to the sender)72 618 Q
(-based tree then the route to the recei)-.22 E -.165(ve)-.275 G
(rs may v).165 E(ary within a channel.)-.275 E
(Furthermore, this may cause either the receipt of duplicate pack)72 631
Q(ets at recei)-.11 E -.165(ve)-.275 G(rs or loss of pack).165 E(ets)
-.11 E(depending on the smoothness of the switcho)72 644 Q -.165(ve)
-.165 G 3.96 -.605(r. T).165 H(hus, it is RECOMMENDED that the RP be)
.605 E(placed as close as possible to the sender)72 657 Q 5.5(.T)-.605 G
(he best location for the RP is that it be the \214rst-hop)-5.5 E
(router closest to the sender)72 670 Q 2.75(,i)-.44 G 2.75(nw)-2.75 G
(hich case the path to the sender and the path to the RP is the same)
-2.75 E(for each recei)72 683 Q -.165(ve)-.275 G 2.75(ra).165 G
(nd the problems mentioned abo)-2.75 E .33 -.165(ve a)-.165 H
(re eliminated.).165 E(The consequences of this)5.5 E
(assumption not being true are that the recei)72 696 Q -.165(ve)-.275 G
2.75(rr).165 G(eaction to congestion may not be appropriate.)-2.75 E
(Generally)72 709 Q 2.75(,t)-.715 G(he WEBRC recei)-2.75 E -.165(ve)
-.275 G 2.75(rw).165 G(ill act conserv)-2.75 E(ati)-.275 E -.165(ve)
-.275 G(ly and reduce its reception rate too much if).165 E
(this assumption is not true, b)72 722 Q
(ut there can be cases where the recei)-.22 E -.165(ve)-.275 G
(rs will act inappropriately).165 E(.)-.715 E(Luby/Go)72 769 Q 276.152
(yal Section)-.11 F 2.75(4.1. [P)2.75 F(age 18])-.165 E EP
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(June 2003)2.75 E(December 2002)103.888 E/F1 11/Times-Bold@0 SF(5.)72 85
Q/F2 14/Times-Bold@0 SF -.14(Pa)5.5 G(ck).14 E(et Header Fields)-.14 E
F0 -.165(Pa)72 101.6 S(ck).165 E(ets sent to a session using WEBRC MUST\
 include Congestion Control Information \214elds as)-.11 E(speci\214ed \
in this section. This document speci\214es short and long formats for t\
he Congestion)72 114.6 Q(Control Information, and it is RECOMMENDED tha\
t protocol instantiations use one of these tw)72 127.6 Q(o)-.11 E 2.75
(formats. Other)72 140.6 R
(formats for the Congestion Control Information \214elds MA)2.75 E 2.75
(Yb)-1.155 G 2.75(eu)-2.75 G(sed by protocol)-2.75 E(instantiations, b)
72 153.6 Q(ut all protocol instantiations are REQ)-.22 E
(UIRED to use these \214elds in a format that is)-.11 E
(compatible with the interpretations of these \214elds.)72 166.6 Q
(Thus, if a protocol does use a dif)5.5 E(ferent format)-.275 E(for the\
 \214elds in the Congestion Control Information then it MUST specify th\
e lengths and)72 179.6 Q(positions of these \214elds within the pack)72
192.6 Q(et header)-.11 E(.)-.605 E(All inte)72 218.6 Q
(ger \214elds are carried in "big-endian" or "netw)-.165 E
(ork order" format, that is, most signi\214cant)-.11 E
(byte \(octet\) \214rst.)72 231.6 Q
(All constants, unless otherwise speci\214ed, are e)5.5 E
(xpressed in base ten.)-.165 E F1(5.1.)72 274.2 Q/F3 13/Times-Bold@0 SF
(Short F)5.5 E(ormat Congestion Contr)-.325 E(ol Inf)-.234 E(ormation)
-.325 E F0
(The short format for the Congestion Control Information is sho)72 290.8
Q(wn in Fig. 1.)-.275 E(The total length of)5.5 E
(the short format is 32-bits.)72 303.8 Q/F4 8/Courier@0 SF 91.2(0123)
81.6 342.8 S 4.8(01234567890123456789012345678901)81.6 355.8 S
(+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+)76.8
368.8 Q 28.8(|C)76.8 381.8 S 19.2(TSI |)-28.8 F(Channel Number|)4.8 E
(Packet Sequence Number)19.2 E(|)24 E
(+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+)76.8
394.8 Q/F5 10/Times-Roman@0 SF
(Fig. 1 - Short format for Congestion Control Information)72 433.8 Q F0
(The function of each \214eld in the Congestion Control Information is \
the follo)72 463.4 Q(wing.)-.275 E(Current T)83 493 Q(ime Slot Inde)
-.385 E 2.75(x\()-.165 G(CTSI\): 8 bits)-2.75 E(CTSI indicates the inde)
105 509.6 Q 2.75(xo)-.165 G 2.75(ft)-2.75 G(he current time slot.)-2.75
E(This must be sent in each pack)5.5 E(et within)-.11 E(the session.)105
522.6 Q(The Current T)5.5 E(ime Slot Inde)-.385 E 2.75(xi)-.165 G
(ncreases by one modulo T each TSD seconds)-2.75 E(at the sender)105
535.6 Q 2.75(,w)-.44 G(here T is the number of time slots associated wi\
th the session and TSD is)-2.75 E(the time slot duration.)105 548.6 Q
(Note that T is also the number of w)5.5 E -2.475 -.22(av e)-.11 H
(channels associated with)2.97 E
(the session, and thus T MUST be at most 255.)105 561.6 Q
(Channel Number \(CN\): 8 bits)83 591.2 Q
(CN is the channel number that this pack)105 607.8 Q(et belongs to.)-.11
E(CN for the base channel is T)5.5 E 2.75(,a)-.814 G(nd)-2.75 E
(the CNs for the w)105 620.8 Q -2.475 -.22(av e)-.11 H
(channels are 0 through T)2.97 E 2.75(-1. Thus,)-1.012 F
(T+1 channels in total are used,)2.75 E(and thus T MUST be at most 255.)
105 633.8 Q -.165(Pa)83 663.4 S(ck).165 E
(et Sequence Number \(PSN\): 16 bits)-.11 E(The PSN of each pack)105 680
Q(et is scoped by its CN v)-.11 E 2.75(alue. The)-.275 F
(sequence numbers of consecuti)2.75 E -.165(ve)-.275 G(pack)105 693 Q
(ets sent to the base channel are numbered consecuti)-.11 E -.165(ve)
-.275 G(ly modulo 2^16.).165 E(The same)5.5 E
(sequence of PSNs are used for each w)105 706 Q -2.475 -.22(av e)-.11 H
(channel in each c)2.97 E 2.75(ycle. The)-.165 F(sequence numbers)2.75 E
(of consecuti)105 719 Q .33 -.165(ve p)-.275 H(ack).165 E
(ets sent to a w)-.11 E -2.475 -.22(av e)-.11 H
(channel are numbered consecuti)2.97 E -.165(ve)-.275 G(ly modulo 2^16)
.165 E(Luby/Go)72 769 Q 276.152(yal Section)-.11 F 2.75(5.1. [P)2.75 F
(age 19])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E(within each c)105 85 Q
(ycle, ending with the last pack)-.165 E
(et sent to the channel before the channel goes)-.11 E
(quiescent with PSN = 2^16-1.)105 98 Q/F1 11/Times-Bold@0 SF(5.2.)72
140.6 Q/F2 13/Times-Bold@0 SF(Long F)5.5 E(ormat Congestion Contr)-.325
E(ol Inf)-.234 E(ormation)-.325 E F0
(The long format for the Congestion Control Information is sho)72 157.2
Q(wn in Fig. 2.)-.275 E(The total length of)5.5 E
(the long format is 64-bits.)72 170.2 Q/F3 8/Courier@0 SF 91.2(0123)81.6
209.2 S 4.8(01234567890123456789012345678901)81.6 222.2 S
(+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+)76.8
235.2 Q 62.4(|C)76.8 248.2 S 62.4(TSI |)-62.4 F(Channel Number)38.4 E(|)
43.2 E
(+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+)76.8
261.2 Q 100.8(|P)76.8 274.2 S(acket Sequence Number)-100.8 E(|)96 E
(+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+)76.8
287.2 Q/F4 10/Times-Roman@0 SF
(Fig. 2 - Long format for Congestion Control Information)72 326.2 Q F0(\
The meaning of each \214eld for the long format is the same as for the \
short format, the only)72 355.8 Q(dif)72 368.8 Q
(ference is that each \214eld is twice as long.)-.275 E(Current T)83
398.4 Q(ime Slot Inde)-.385 E 2.75(x\()-.165 G(CTSI\): 16 bits)-2.75 E
(CTSI indicates the inde)105 415 Q 2.75(xo)-.165 G 2.75(ft)-2.75 G
(he current time slot.)-2.75 E(This must be sent in each pack)5.5 E
(et within)-.11 E(the session.)105 428 Q(The Current T)5.5 E
(ime Slot Inde)-.385 E 2.75(xi)-.165 G
(ncreases by one modulo T each TSD seconds)-2.75 E(at the sender)105 441
Q 2.75(,w)-.44 G(here T is the number of time slots associated with the\
 session and TSD is)-2.75 E(the time slot duration.)105 454 Q
(Note that T is also the number of w)5.5 E -2.475 -.22(av e)-.11 H
(channels associated with)2.97 E
(the session, and thus T MUST be at most 65 535.)105 467 Q
(Channel Number \(CN\): 16 bits)83 496.6 Q
(CN is the channel number that this pack)105 513.2 Q(et belongs to.)-.11
E(CN for the base channel is T)5.5 E 2.75(,a)-.814 G(nd)-2.75 E
(the CNs for the w)105 526.2 Q -2.475 -.22(av e)-.11 H
(channels are 0 through T)2.97 E 2.75(-1. Thus,)-1.012 F
(T+1 channels in total are used,)2.75 E
(and thus T MUST be at most 65 535.)105 539.2 Q -.165(Pa)83 568.8 S(ck)
.165 E(et Sequence Number \(PSN\): 32 bits)-.11 E(The PSN of each pack)
105 585.4 Q(et is scoped by its CN v)-.11 E 2.75(alue. The)-.275 F
(sequence numbers of consecuti)2.75 E -.165(ve)-.275 G(pack)105 598.4 Q
(ets sent to the base channel are numbered consecuti)-.11 E -.165(ve)
-.275 G(ly modulo 2^32.).165 E(The same)5.5 E
(sequence of PSNs are used for each w)105 611.4 Q -2.475 -.22(av e)-.11
H(channel in each c)2.97 E 2.75(ycle. The)-.165 F(sequence numbers)2.75
E(of consecuti)105 624.4 Q .33 -.165(ve p)-.275 H(ack).165 E
(ets sent to a w)-.11 E -2.475 -.22(av e)-.11 H
(channel are numbered consecuti)2.97 E -.165(ve)-.275 G(ly modulo 2^32)
.165 E(within each c)105 637.4 Q(ycle, ending with the last pack)-.165 E
(et sent to the channel before the channel goes)-.11 E
(quiescent with PSN = 2^32-1.)105 650.4 Q F1(6.)72 693 Q/F5 14
/Times-Bold@0 SF(Requir)5.5 E(ements Fr)-.252 E
(om Other Building Blocks)-.252 E F0
(As described in RFC3048 [19], WEBRC is a b)72 709.6 Q
(uilding block that is intended to be used, in)-.22 E
(conjunction with other b)72 722.6 Q
(uilding blocks, to help specify a protocol instantiation.)-.22 E
(Luby/Go)72 769 Q 284.402(yal Section)-.11 F 2.75(6. [P)2.75 F(age 20])
-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E(WEBRC does not pro)72 85 Q
(vide higher le)-.165 E -.165(ve)-.275 G 2.75(ls).165 G
(ession support, e.g., ho)-2.75 E 2.75(wr)-.275 G(ecei)-2.75 E -.165(ve)
-.275 G(rs obtain the necessary).165 E(session description and ho)72 98
Q 2.75(wt)-.275 G(he recei)-2.75 E -.165(ve)-.275 G(rs demultiple).165 E
2.75(xr)-.165 G(ecei)-2.75 E -.165(ve)-.275 G 2.75(dp).165 G(ack)-2.75 E
(ets based on their session.)-.11 E(There is support pro)72 111 Q
(vided by other b)-.165 E
(uilding blocks that can be used in conjunction with WEBRC)-.22 E
(to pro)72 124 Q(vide some of this support.)-.165 E -.165(Fo)5.5 G 2.75
(re).165 G(xample, LCT [11] can pro)-2.915 E(vide some of the higher le)
-.165 E -.165(ve)-.275 G 2.75(li).165 G(n-)-2.75 E
(band session support that may be needed by recei)72 137 Q -.165(ve)
-.275 G(rs, and the WEBRC Congestion Control).165 E
(Information \(CCI\) required in each pack)72 150 Q
(et can be carried in the CCI \214eld of the LCT header [11].)-.11 E
(WEBRC does not pro)72 166.6 Q(vide an)-.165 E 2.75(yt)-.165 G
(ype of reliability)-2.75 E 2.75(,a)-.715 G
(nd in particular does not pro)-2.75 E(vide support for)-.165 E
(retransmission of loss pack)72 179.6 Q 2.75(ets. Reliability)-.11 F
(can be added by independent means, such as by the)2.75 E
(use of FEC codes as described in [12] and speci\214ed in the FEC b)72
192.6 Q(uilding block [13].)-.22 E/F1 11/Times-Bold@0 SF(7.)72 222.2 Q
/F2 14/Times-Bold@0 SF(Security Considerations)5.5 E F0
(WEBRC can be subject to denial-of-service attacks by attack)72 238.8 Q
(ers that try to confuse the congestion)-.11 E
(control mechanism for recei)72 251.8 Q -.165(ve)-.275 G
(rs by injecting for).165 E(ged pack)-.198 E
(ets into the multicast stream.)-.11 E(This attack)5.5 E(most adv)72
264.8 Q(ersely af)-.165 E(fects netw)-.275 E(ork elements and recei)-.11
E -.165(ve)-.275 G(rs do).165 E(wnstream of the attack, and much less)
-.275 E(signi\214cantly the rest of the netw)72 277.8 Q
(ork and other recei)-.11 E -.165(ve)-.275 G 2.75(rs. Because).165 F
(of this and because of the)2.75 E
(potential attacks due to the use of FEC described abo)72 290.8 Q -.165
(ve)-.165 G 2.75(,i).165 G 2.75(ti)-2.75 G 2.75(sR)-2.75 G
(ECOMMENDED that Re)-2.75 E -.165(ve)-.275 G(rse).165 E -.165(Pa)72
303.8 S(th F).165 E(orw)-.165 E(arding checks be enabled in all netw)
-.11 E(ork routers and switches along the path from the)-.11 E
(sender to recei)72 316.8 Q -.165(ve)-.275 G
(rs to limit the possibility of a bad agent injecting for).165 E
(ged pack)-.198 E(ets into the)-.11 E(multicast tree data path.)72 329.8
Q(It is also RECOMMENDED that pack)72 355.8 Q
(et authentication be used to authenticate each pack)-.11 E(et)-.11 E
(immediately upon receipt before the recei)72 368.8 Q -.165(ve)-.275 G
2.75(rp).165 G(erforms an)-2.75 E 2.75(yW)-.165 G
(EBRC actions based upon its)-2.75 E 2.75(receipt. Unfortunately)72
381.8 R 2.75(,t)-.715 G(here are currently no practical multicast pack)
-2.75 E(et authentication schemes)-.11 E(that of)72 394.8 Q
(fer instant pack)-.275 E(et authentication upon receipt.)-.11 E(Ho)5.5
E(we)-.275 E -.165(ve)-.275 G .88 -.44(r, T).165 H
(ESLA [17] can be used to).44 E(authenticate each pack)72 407.8 Q
(et a fe)-.11 E 2.75(ws)-.275 G(econds after receipt.)-2.75 E
(Thus, TESLA could be used in conjunction)5.5 E
(with WEBRC to authenticate pack)72 420.8 Q(ets and for e)-.11 E
(xample terminate the session upon detection of a)-.165 E(for)72 433.8 Q
(ged pack)-.198 E 2.75(et. Ho)-.11 F(we)-.275 E -.165(ve)-.275 G .88
-.44(r, i).165 H 2.75(ti).44 G 2.75(sR)-2.75 G
(ECOMMENDED that the normal WEBRC recei)-2.75 E -.165(ve)-.275 G 2.75
(rr).165 G(esponses to)-2.75 E(recei)72 446.8 Q -.165(ve)-.275 G 2.75
(dp).165 G(ack)-2.75 E(ets are allo)-.11 E
(wed to occur immediately and are not delayed by the TESLA)-.275 E
(authentication process.)72 459.8 Q(This is because the o)5.5 E -.165
(ve)-.165 G(rall WEBRC performance w).165 E(ould be greatly)-.11 E(de)72
472.8 Q(graded if the recei)-.165 E -.165(ve)-.275 G 2.75(rd).165 G
(elayed its WEBRC response to pack)-2.75 E(et receipt for se)-.11 E
-.165(ve)-.275 G(ral seconds.).165 E 2.75(Ar)72 498.8 S(ecei)-2.75 E
-.165(ve)-.275 G 2.75(rw).165 G
(ith an incorrect or corrupted implementation of WEBRC may af)-2.75 E
(fect health of the)-.275 E(netw)72 511.8 Q
(ork in the path between the sender and the recei)-.11 E -.165(ve)-.275
G .88 -.44(r, a).165 H(nd may also af).44 E(fect the reception rates of)
-.275 E(other recei)72 524.8 Q -.165(ve)-.275 G
(rs joined to the session.).165 E
(It is therefore RECOMMENDED that recei)5.5 E -.165(ve)-.275 G
(rs be required).165 E(to identify themselv)72 537.8 Q(es as le)-.165 E
(gitimate before the)-.165 E 2.75(yr)-.165 G(ecei)-2.75 E .33 -.165
(ve t)-.275 H(he session description needed to join the).165 E(session.)
72 550.8 Q(Another vulnerability of WEBRC is the potential of recei)72
576.8 Q -.165(ve)-.275 G(rs obtaining an incorrect session).165 E
(description for the session.)72 589.8 Q
(The consequences of this could be that le)5.5 E(gitimate recei)-.165 E
-.165(ve)-.275 G(rs with the).165 E
(wrong session description are unable to correctly recei)72 602.8 Q .33
-.165(ve t)-.275 H(he session content, or that recei).165 E -.165(ve)
-.275 G(rs).165 E(inadv)72 615.8 Q(ertently try to recei)-.165 E .33
-.165(ve a)-.275 H 2.75(tam).165 G(uch higher rate than the)-2.75 E 2.75
(ya)-.165 G(re capable of, thereby disrupting)-2.75 E(traf)72 628.8 Q
(\214c in portions of the netw)-.275 E 2.75(ork. T)-.11 F 2.75(oa)-.88 G
-.22(vo)-2.97 G(id these problems, it is RECOMMENDED that measures).22 E
(be tak)72 641.8 Q(en to pre)-.11 E -.165(ve)-.275 G(nt recei).165 E
-.165(ve)-.275 G(rs from accepting incorrect session descriptions, e.g.\
, by using source).165 E(authentication to ensure that recei)72 654.8 Q
-.165(ve)-.275 G(rs only accept le).165 E
(gitimate session descriptions from authorized)-.165 E(senders.)72 667.8
Q(Luby/Go)72 769 Q 284.402(yal Section)-.11 F 2.75(7. [P)2.75 F(age 21])
-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E/F1 11/Times-Bold@0 SF(8.)72 85
Q/F2 14/Times-Bold@0 SF(IAN)5.5 E 3.5(AC)-.28 G(onsiderations)-3.5 E F0
(No information in this speci\214cation is subject to IAN)72 101.6 Q
2.75(Ar)-.385 G -.165(eg)-2.75 G(istration.).165 E F1(9.)72 144.2 Q F2
(Intellectual Pr)5.5 E(operty Issues)-.252 E F0(The IETF has been noti\
\214ed of intellectual property rights claimed in re)72 160.8 Q -.055
(ga)-.165 G(rd to some or all of the).055 E
(speci\214cation contained in this document.)72 173.8 Q -.165(Fo)5.5 G
2.75(rm).165 G(ore information consult the online list of claimed)-2.75
E(rights.)72 186.8 Q F1(10.)72 229.4 Q F2(Refer)5.5 E(ences)-.252 E F0
([1] S. Bradner)72 259 Q 2.75(,`)-.44 G
(`The Internet Standards Process -- Re)-3.564 E(vision 3,)-.275 E 1.628
-.814('' R)-.77 H(FC2026, October 1996.).814 E([2] S. Bradner)72 285 Q
2.75(,`)-.44 G(`K)-3.564 E .33 -.165(ey w)-.275 H
(ords for use in RFCs to Indicate Requirement Le).055 E -.165(ve)-.275 G
(ls,).165 E 1.628 -.814('' R)-.77 H(FC2119, March).814 E(1997.)72 298 Q
([3] J.W)72 324 Q 2.75(.B)-1.012 G(yers, G. Horn, M. Luby)-2.75 E 2.75
(,M)-.715 G 2.75(.M)-2.75 G(itzenmacher)-2.75 E 2.75(,W)-.44 G 2.75(.S)
-3.762 G(ha)-2.75 E -.165(ve)-.22 G 3.96 -.605(r. `).165 H
(`FLID-DL: Congestion control)-.209 E(for layered multicast,)72 337 Q
1.628 -.814('' I)-.77 H
(EEE J. on Selected Areas in Communications, Special Issue on Netw).814
E(ork)-.11 E(Support for Multicast Communication, V)72 350 Q
(ol. 20, No. 8, October 2002, pp. 1558-1570.)-1.419 E([4] P)72 376 Q
2.75(.D)-1.221 G(agum, R. Karp, M. Luby)-2.75 E 2.75(,a)-.715 G
(nd S. Ross, `)-2.75 E -.88(`A)-.814 G 2.75(no).88 G
(ptimal algorithm for Monte Carlo)-2.75 E(estimation,)72 389 Q 1.628
-.814('' S)-.77 H(IAM J. Comput., 29\(5\):1484-1496, April 2000.).814 E
([5] S. Deering, `)72 415 Q(`Host Extensions for IP Multicasting,)-.814
E 1.628 -.814('' R)-.77 H(FC1112, August 1989.).814 E([6] V)72 441 Q
2.75(.KG)-1.419 G -.11(oy)-2.75 G(al, `).11 E(`On WEBRC W)-.814 E -2.475
-.22(av e)-.88 H(Design and Serv)2.97 E(er Implementation,)-.165 E 1.628
-.814('' D)-.77 H(igital F).814 E(ountain)-.165 E -.77(Te)72 454 S
(chnical Report no. DF2002-09-001, September 2002, a).77 E -.275(va)-.22
G(ilable at).275 E(http://www)72 467 Q
(.digitalfountain.com/technology/.)-.715 E([7] M. Handle)72 493 Q 1.43
-.715(y, J)-.165 H 2.75(.P).715 G(adh)-2.915 E(ye, S. Flo)-.055 E
(yd, and J. W)-.11 E(idmer)-.44 E 2.75(,`)-.44 G
(`TCP Friendly Rate Control \(TFRC\):)-3.564 E
(Protocol Speci\214cation,)72 506 Q 1.628 -.814('' I)-.77 H
(nternet Draft draft-ietf-tsvwg-tfrc-05, October 2002, a w).814 E
(ork in progress.)-.11 E([8] H. W)72 532 Q 2.75(.H)-1.012 G(olbrook, `)
-2.75 E 1.76 -.88(`A C)-.814 H(hannel Model for Multicast,).88 E 1.628
-.814('' P)-.77 H(h.D. Dissertation, Stanford Uni).814 E -.165(ve)-.275
G(rsity).165 E(,)-.715 E
(Department of Computer Science, Stanford, California, August 2001.)72
545 Q([9] R. K)72 571 Q(ermode and L. V)-.275 E(icisano, `)-.66 E -.88
(`A)-.814 G(uthor Guidelines for Reliable Multicast T).88 E
(ransport \(RMT\))-.385 E
(Building Blocks and Protocol Instantiation documents')72 584 Q
(', RFC3269, April 2002.)-.814 E([10] M. Luby)72 610 Q 2.75(,J)-.715 G
2.75(.G)-2.75 G(emmell, L. V)-2.75 E(icisano, L. Rizzo, and J. Cro)-.66
E(wcroft, `)-.275 E -.88(`A)-.814 G(synchronous Layered).88 E
(Coding protocol instantiation,)72 623 Q 1.628 -.814('' I)-.77 H
(nternet Draft draft-ietf-rmt-pi-alc-08, April 2002, a w).814 E(ork in)
-.11 E(progress.)72 636 Q([11] M. Luby)72 662 Q 2.75(,J)-.715 G 2.75(.G)
-2.75 G(emmell, L. V)-2.75 E(icisano, L. Rizzo, M. Handle)-.66 E 1.43
-.715(y, a)-.165 H(nd J. Cro).715 E(wcroft, `)-.275 E(`Layered)-.814 E
(Coding T)72 675 Q(ransport b)-.385 E(uilding block,)-.22 E 1.628 -.814
('' I)-.77 H
(nternet Draft draft-ietf-rmt-bb-lct-04.txt, February 2002, a).814 E
-.11(wo)72 688 S(rk in progress.).11 E([12] M. Luby)72 714 Q 2.75(,J)
-.715 G 2.75(.G)-2.75 G(emmell, L. V)-2.75 E
(icisano, L. Rizzo, M. Handle)-.66 E 1.43 -.715(y, a)-.165 H(nd J. Cro)
.715 E(wcroft, `)-.275 E(`The Use of)-.814 E(Luby/Go)72 769 Q 278.902
(yal Section)-.11 F 2.75(10. [P)2.75 F(age 22])-.165 E EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 78.61(-DRAFT Expires:)-1.012 F
(June 2003)2.75 E(December 2002)103.888 E -.165(Fo)72 85 S(rw).165 E
(ard Error Correction in Reliable Multicast,)-.11 E 1.628 -.814('' I)
-.77 H(nternet Draft draft-ietf-rmt-info-fec-03.txt,).814 E
(September 2002, a w)72 98 Q(ork in progress.)-.11 E([13] M. Luby)72 124
Q 2.75(,J)-.715 G 2.75(.G)-2.75 G(emmell, L. V)-2.75 E
(icisano, L. Rizzo, M. Handle)-.66 E 1.43 -.715(y, a)-.165 H(nd J. Cro)
.715 E(wcroft, `)-.275 E(`F)-.814 E(orw)-.165 E(ard Error)-.11 E
(Correction b)72 137 Q(uilding block,)-.22 E 1.628 -.814('' I)-.77 H
(nternet Draft draft-ietf-rmt-bb-fec-07.txt, September 2002, a w).814 E
(ork in)-.11 E(progress.)72 150 Q([14] M. Luby and V)72 176 Q 2.75(.KG)
-1.419 G -.11(oy)-2.75 G(al, `).11 E(`W)-.814 E -2.475 -.22(av e)-.88 H
(and Equation Based Rate Control Using Multicast Round)2.97 E -.385(Tr)
72 189 S(ip T).385 E(ime: Extended Report,)-.385 E 1.628 -.814('' D)-.77
H(igital F).814 E(ountain T)-.165 E
(echnical Report no. DF2002-07-001, September)-.77 E(2002, a)72 202 Q
-.275(va)-.22 G(ilable at http://www).275 E
(.digitalfountain.com/technology/.)-.715 E([15] M. Luby)72 228 Q 2.75
(,V)-.715 G 2.75(.KG)-4.169 G -.11(oy)-2.75 G
(al, S. Skaria, and G. B. Horn, `).11 E(`W)-.814 E -2.475 -.22(av e)-.88
H(and Equation Based Rate Control)2.97 E(Using Multicast Round T)72 241
Q(rip T)-.385 E(ime,)-.385 E 1.628 -.814('' P)-.77 H(roc. A).814 E
(CM SIGCOMM 2002, Pittsb)-.44 E(ur)-.22 E(gh, P)-.198 E 2.75(A, August)
-1.012 F(2002,)2.75 E(pp. 191-214.)72 254 Q([16] A. Mankin, A. Romano)72
280 Q 1.43 -.715(w, S)-.275 H 2.75(.B).715 G(radner)-2.75 E 2.75(,a)-.44
G(nd V)-2.75 E 2.75(.P)-1.419 G(axson, `)-2.915 E(`IETF Criteria for Ev)
-.814 E(aluating Reliable)-.275 E(Multicast T)72 293 Q
(ransport and Application Protocols,)-.385 E 1.628 -.814('' R)-.77 H
(FC2357, June 1998.).814 E
([17] A. Perrig, R. Canetti, D. Song, and J. D. T)72 319 Q(yg)-.88 E(ar)
-.055 E 2.75(,`)-.44 G(`Ef)-3.564 E
(\214cient and Secure Source Authentication)-.275 E(for Multicast,)72
332 Q 1.628 -.814('' N)-.77 H(etw).814 E(ork and Distrib)-.11 E
(uted System Security Symposium, NDSS 2001, pp. 35-46,)-.22 E
(February 2001.)72 345 Q([18] L. V)72 371 Q
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