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/F0 10/Courier-Bold@0 SF(Internet Engineering Task Force)72 85 Q
(Sally Floyd)180 E 318(INTERNET-DRAFT ICIR)72 98 R 192
(draft-ietf-dccp-ccid2-05.ps Eddie)72 111 R(Kohler)6 E
(Expires: August 2004)72 124 Q(UCLA)288 E(16 February 2004)408 137 Q/F1
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(Internet-Drafts are draft documents v)100.8 295.8 Q
(alid for a maximum of six months and may be)-.275 E
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100.8 321.8 Q(ork in progress.")-.11 E
(The list of current Internet-Drafts can be accessed at http://www)100.8
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(Copyright Notice)72 407 Q F3(Cop)100.8 423.6 Q
(yright \(C\) The Internet Society \(2004\). All Rights Reserv)-.11 E
(ed.)-.165 E F2(Abstract)72 449.6 Q F3(This document contains the pro\
\214le for Congestion Control Identi\214er 2, TCP-lik)100.8 466.2 Q(e)
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G F2(5)11.5 E(3.2. Updates)115.8 158 Q F0 11(.......................)
5.18 G F2(6)11.5 E(4. Connection Establishment)100.8 170 Q F0 11
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85 Q/F2 14/Times-Bold@0 SF(Intr)5.5 E(oduction)-.252 E F0(This document\
 contains the pro\214le for Congestion Control Identi\214er 2, TCP-lik)
100.8 101.6 Q(e)-.11 E(Congestion Control, in the Datagram Congestion C\
ontrol Protocol \(DCCP\) [DCCP].)100.8 114.6 Q(DCCP uses Congestion Con\
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127.6 Q(mechanism in use on a half-connection.)100.8 140.6 Q
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(wn dynamics of TCP-lik)-.275 E 2.75(ec)-.11 G(ongestion control)-2.75 E
-.165(ove)100.8 721.2 S 2.75(rt).165 G(hat of ne)-2.75 E
(wer congestion control mechanisms that ha)-.275 E .33 -.165(ve n)-.22 H
(ot yet met the test of).165 E(Flo)72 769 Q(yd/K)-.11 E 284.171
(ohler Section)-.385 F 2.75(3. [P)2.75 F(age 4])-.165 E 0 Cg EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 72.802(-DRAFT Expires:)-1.012 F
(August 2004)2.75 E(February 2004)103.569 E(widespread deplo)100.8 85 Q
(yment in the Internet.)-.11 E/F1 11/Times-Bold@0 SF(3.1.)72 111 Q/F2 13
/Times-Bold@0 SF(Example Half-Connection)5.5 E F0(This e)100.8 127.6 Q
(xample sho)-.165 E
(ws the typical progress of a half-connection using TCP-lik)-.275 E 2.75
(eC)-.11 G(ongestion)-2.75 E(Control speci\214ed by CCID 2, not includi\
ng connection initiation and termination.)100.8 140.6 Q(Ag)5.5 E(ain,)
-.055 E(the "sender" is the HC-Sender)100.8 153.6 Q 2.75(,a)-.44 G
(nd the "recei)-2.75 E -.165(ve)-.275 G(r" is the HC-Recei).165 E -.165
(ve)-.275 G 3.96 -.605(r. T).165 H(he e).605 E(xample is)-.165 E
(informati)100.8 166.6 Q -.165(ve)-.275 G 2.75(,n).165 G(ot normati)
-2.75 E -.165(ve)-.275 G(.).165 E 13.224(\(1\) The)100.8 183.2 R
(sender sends DCCP-Data pack)2.75 E(ets, where the number of pack)-.11 E
(ets sent is go)-.11 E -.165(ve)-.165 G(rned).165 E
(by a congestion windo)129.6 196.2 Q 1.43 -.715(w, c)-.275 H
(wnd, as in TCP).715 E 5.5(.E)-1.221 G(ach DCCP-Data pack)-5.5 E
(et uses a sequence)-.11 E(number)129.6 209.2 Q 5.5(.T)-.605 G
(he sender also sends an Ack Ratio feature option specifying the number)
-5.5 E(of data pack)129.6 222.2 Q(ets to be co)-.11 E -.165(ve)-.165 G
(red by an Ack pack).165 E(et from the recei)-.11 E -.165(ve)-.275 G
-.605(r.).165 G(Assuming that the half-connection is Explicit Congestio\
n Noti\214cation \(ECN\))129.6 238.8 Q
(capable \(the ECN Capable feature is turned on---the def)129.6 251.8 Q
(ault\), each DCCP-Data)-.11 E(pack)129.6 264.8 Q(et is sent as ECN-Cap\
able with either the ECT\(0\) or the ECT\(1\) codepoint set,)-.11 E
(as described in [RFC 3540].)129.6 277.8 Q 13.224(\(2\) The)100.8 294.4
R(recei)2.75 E -.165(ve)-.275 G 2.75(rs).165 G(ends a DCCP-Ack pack)
-2.75 E(et ackno)-.11 E(wledging the data pack)-.275 E(ets for e)-.11 E
-.165(ve)-.275 G(ry).165 E(Ack Ratio data pack)129.6 307.4 Q
(ets transmitted by the sender)-.11 E 5.5(.E)-.605 G(ach DCCP-Ack pack)
-5.5 E(et uses a)-.11 E(sequence number and contains an Ack V)129.6
320.4 Q(ector)-1.221 E 5.5(.T)-.605 G(he sequence number ackno)-5.5 E
(wledged)-.275 E(in DCCP-Ack pack)129.6 333.4 Q
(ets is that of the recei)-.11 E -.165(ve)-.275 G 2.75(dp).165 G(ack)
-2.75 E(et with the highest sequence)-.11 E(number)129.6 346.4 Q 2.75
(,r)-.44 G(ather than a TCP-lik)-2.75 E 2.75(ec)-.11 G(umulati)-2.75 E
.33 -.165(ve a)-.275 H(ckno).165 E(wledgement.)-.275 E
(If the half-connection is ECN capable, the recei)129.6 363 Q -.165(ve)
-.275 G 2.75(rr).165 G(eturns the sum of recei)-2.75 E -.165(ve)-.275 G
2.75(dE).165 G(CN)-2.75 E(Nonces via Ack V)129.6 376 Q
(ector options, allo)-1.221 E(wing the sender to probabilistically v)
-.275 E(erify that)-.165 E(the recei)129.6 389 Q -.165(ve)-.275 G 2.75
(ri).165 G 2.75(sn)-2.75 G(ot misbeha)-2.75 E 2.75(ving. DCCP-Ack)-.22 F
(pack)2.75 E(ets from the recei)-.11 E -.165(ve)-.275 G 2.75(ra).165 G
(re also sent)-2.75 E
(as ECN-Capable, since the sender will control the ackno)129.6 402 Q
(wledgement rate in a)-.275 E(roughly TCP-friendly w)129.6 415 Q
(ay using the Ack Ratio feature.)-.11 E(There is little need for the)5.5
E(recei)129.6 428 Q -.165(ve)-.275 G 2.75(rt).165 G 2.75(ov)-2.75 G
(erify the nonces of its DCCP-Ack pack)-2.915 E
(ets, since the sender cannot get)-.11 E
(signi\214cant bene\214t from misreporting the ack mark rate.)129.6 441
Q 13.224(\(3\) The)100.8 457.6 R
(sender continues sending DCCP-Data pack)2.75 E
(ets as controlled by the congestion)-.11 E(windo)129.6 470.6 Q 4.18
-.715(w. U)-.275 H(pon recei).715 E(ving DCCP-Ack pack)-.275 E
(ets, the sender e)-.11 E(xamines their Ack V)-.165 E(ectors)-1.221 E
(to learn about mark)129.6 483.6 Q(ed or dropped data pack)-.11 E
(ets, and adjusts its congestion windo)-.11 E(w)-.275 E(accordingly)
129.6 496.6 Q 5.5(.B)-.715 G(ecause this is unreliable transfer)-5.5 E
2.75(,t)-.44 G(he sender does not retransmit)-2.75 E(dropped pack)129.6
509.6 Q(ets.)-.11 E 13.224(\(4\) DCCP-Ack)100.8 526.2 R(pack)2.75 E
(ets use sequence numbers, so the sender has direct information)-.11 E
(about the fraction of lost or mark)129.6 539.2 Q(ed DCCP-Ack pack)-.11
E 2.75(ets. The)-.11 F(sender responds to lost)2.75 E(or mark)129.6
552.2 Q(ed DCCP-Ack pack)-.11 E
(ets by modifying the Ack Ratio sent to the recei)-.11 E -.165(ve)-.275
G -.605(r.).165 G 13.224(\(5\) The)100.8 568.8 R(sender ackno)2.75 E
(wledges the recei)-.275 E -.165(ve)-.275 G(r').165 E 2.75(sa)-.605 G
(ckno)-2.75 E(wledgements at least once per)-.275 E(congestion windo)
129.6 581.8 Q 4.18 -.715(w. I)-.275 H 2.75(fb).715 G
(oth half-connections are acti)-2.75 E -.165(ve)-.275 G 2.75(,t).165 G
(he sender')-2.75 E(s)-.605 E(ackno)129.6 594.8 Q
(wledgement of the recei)-.275 E -.165(ve)-.275 G(r').165 E 2.75(sa)
-.605 G(ckno)-2.75 E(wledgements is included in the sender')-.275 E(s)
-.605 E(ackno)129.6 607.8 Q(wledgement of the recei)-.275 E -.165(ve)
-.275 G(r').165 E 2.75(sd)-.605 G(ata pack)-2.75 E 2.75(ets. If)-.11 F
(the re)2.75 E -.165(ve)-.275 G(rse-path half-connection).165 E
(is quiescent, the sender sends a DCCP-DataAck pack)129.6 620.8 Q
(et that includes an)-.11 E(Ackno)129.6 633.8 Q
(wledgement Number in the header)-.275 E(.)-.605 E 13.224(\(6\) The)
100.8 650.4 R(sender estimates round-trip times, either through k)2.75 E
(eeping track of)-.11 E(ackno)129.6 663.4 Q
(wledgement round-trip times as TCP does or through e)-.275 E(xplicit T)
-.165 E(imestamp)-.385 E(options, and calculates a T)129.6 676.4 Q
(imeOut \(T)-.385 E(O\) v)-.198 E(alue much as the R)-.275 E .396 -.198
(TO \()-.66 H(Retransmit).198 E -.385(Ti)129.6 689.4 S
(meout\) is calculated in TCP).385 E 5.5(.T)-1.221 G(he T)-5.5 E 2.75
(Oi)-.198 G 2.75(su)-2.75 G(sed to determine when a ne)-2.75 E 2.75(wD)
-.275 G(CCP-)-2.75 E(Data pack)129.6 702.4 Q(et can be transmitted when\
 the sender has been limited by the congestion)-.11 E(windo)129.6 715.4
Q 2.75(wa)-.275 G(nd no feedback has been recei)-2.75 E -.165(ve)-.275 G
2.75(df).165 G(rom the recei)-2.75 E -.165(ve)-.275 G -.605(r.).165 G
(Flo)72 769 Q(yd/K)-.11 E 275.921(ohler Section)-.385 F 2.75(3.1. [P)
2.75 F(age 5])-.165 E 0 Cg EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 72.802(-DRAFT Expires:)-1.012 F
(August 2004)2.75 E(February 2004)103.569 E/F1 11/Times-Bold@0 SF(3.2.)
72 85 Q/F2 13/Times-Bold@0 SF(Updates)5.5 E F0
(The congestion control mechanisms described here closely follo)100.8
101.6 Q 2.75(wm)-.275 G(echanisms)-2.75 E
(standardized by the IETF for use in SA)100.8 114.6 Q(CK-based TCP)-.44
E 2.75(,a)-1.221 G(nd we rely partially on e)-2.75 E(xisting)-.165 E(TC\
P documentation, such as [RFC 793], [RFC 3465], and [RFC 3517]. TCP con\
gestion)100.8 127.6 Q(control continues to e)100.8 140.6 Q -.22(vo)-.275
G(lv).22 E(e, b)-.165 E(ut conformant CCID 2 implementations SHOULD w)
-.22 E(ait for)-.11 E -.165(ex)100.8 153.6 S
(plicit updates to CCID 2, rather than tracking TCP').165 E 2.75(se)
-.605 G -.22(vo)-3.025 G(lution directly).22 E 5.5(.T)-.715 G(he dif)
-5.5 E(ferences)-.275 E(between CCID 2 and straight TCP include: CCID 2\
 de\214nes an additional mechanism not)100.8 166.6 Q
(currently standardized for use in TCP)100.8 179.6 Q 2.75(,n)-1.221 G
(amely congestion control on ackno)-2.75 E(wledgements as)-.275 E(achie)
100.8 192.6 Q -.165(ve)-.275 G 2.75(db).165 G 2.75(yt)-2.75 G
(he Ack Ratio.)-2.75 E(DCCP is a datagram protocol, so se)5.5 E -.165
(ve)-.275 G(ral parameters whose).165 E(units are bytes in TCP)100.8
205.6 Q 2.75(,s)-1.221 G(uch as the congestion windo)-2.75 E 2.75(wc)
-.275 G(wnd, ha)-2.75 E .33 -.165(ve u)-.22 H(nits of pack).165 E
(ets in)-.11 E(DCCP)100.8 218.6 Q 5.5(.U)-1.221 G
(nreliability also leads to dif)-5.5 E(ferences from TCP: DCCP ne)-.275
E -.165(ve)-.275 G 2.75(rr).165 G(etransmits a pack)-2.75 E(et,)-.11 E(\
so congestion control mechanisms that distinguish retransmissions from \
ne)100.8 231.6 Q 2.75(wp)-.275 G(ack)-2.75 E(ets need)-.11 E
(rethinking in the DCCP conte)100.8 244.6 Q(xt.)-.165 E F1(4.)72 270.6 Q
/F3 14/Times-Bold@0 SF(Connection Establishment)5.5 E F0
(Use of the Ack V)100.8 287.2 Q(ector is MAND)-1.221 E -.506 -1.221
(AT O)-.44 H 1.43 -.715(RY o)1.221 H 2.75(nC).715 G
(CID 2 half-connections, so the sender MUST)-2.75 E
(send a "Change R\(Use Ack V)100.8 300.2 Q(ector)-1.221 E 2.75(,1)-.44 G
(\)" option to the recei)-2.75 E -.165(ve)-.275 G 2.75(ra).165 G 2.75
(sp)-2.75 G(art of connection)-2.75 E 2.75(establishment. The)100.8
313.2 R(sender SHOULD NO)2.75 E 2.75(Ts)-.44 G
(end data until it has recei)-2.75 E -.165(ve)-.275 G 2.75(dt).165 G(he)
-2.75 E(corresponding "Con\214rm L\(Use Ack V)100.8 326.2 Q(ector)-1.221
E 2.75(,1)-.44 G(\)" from the recei)-2.75 E -.165(ve)-.275 G .88 -.44
(r, e).165 H(xcept for possible data).275 E
(included on the initial DCCP-Request pack)100.8 339.2 Q(et.)-.11 E
(CCID 2 requires only generic feedback, namely Ack V)100.8 355.8 Q
(ector)-1.221 E 5.5(.T)-.605 G(herefore, CCID 2 MA)-5.5 E(Y)-1.155 E
(masquerade as CCID 1 as long as the recei)100.8 368.8 Q -.165(ve)-.275
G(r').165 E 2.75(sU)-.605 G(se Ack V)-2.75 E(ector feature is set to 1.)
-1.221 E F1(5.)72 394.8 Q F3(Congestion Contr)5.5 E(ol on Data P)-.252 E
(ack)-.14 E(ets)-.14 E F0(CCID 2')100.8 411.4 Q 2.75(sc)-.605 G
(ongestion control mechanisms are based on those for SA)-2.75 E
(CK-based TCP [RFC)-.44 E(3517], since the Ack V)100.8 424.4 Q
(ector pro)-1.221 E
(vides all the information that might be transmitted in)-.165 E(SA)100.8
437.4 Q(CK options.)-.44 E 2.75(AC)100.8 454 S
(CID 2 data sender maintains three inte)-2.75 E(ger parameters.)-.165 E
(All of their units are pack)5.5 E(ets,)-.11 E(not bytes; for e)100.8
467 Q(xample, CCID 2 e)-.165 E(xpresses its windo)-.165 E 2.75(wi)-.275
G 2.75(nt)-2.75 G(erms of ho)-2.75 E 2.75(wm)-.275 G(an)-2.75 E 2.75(yp)
-.165 G(ack)-2.75 E(ets may)-.11 E(be sent.)100.8 480 Q 13.224
(\(1\) The)100.8 496.6 R(congestion windo)2.75 E 2.75(w")-.275 G
(cwnd", which equals the maximum number of data-)-2.75 E(carrying pack)
129.6 509.6 Q(ets allo)-.11 E(wed in the netw)-.275 E(ork at an)-.11 E
2.75(yt)-.165 G 2.75(ime. \("Data-carrying)-2.75 F(pack)2.75 E
(et" means)-.11 E(an)129.6 522.6 Q 2.75(yD)-.165 G(CCP pack)-2.75 E
(et that contains user data: DCCP-Data, DCCP-DataAck, and)-.11 E
(occasionally DCCP-Request, DCCP-Response, and DCCP-Mo)129.6 535.6 Q
-.165(ve)-.165 G(.\)).165 E 13.224(\(2\) The)100.8 552.2 R(slo)2.75 E
(w-start threshold "ssthresh", which controls adjustments to cwnd.)-.275
E 13.224(\(3\) The)100.8 568.8 R(pipe v)2.75 E
(alue "pipe", which is the sender')-.275 E 2.75(se)-.605 G
(stimate of the number of data-carrying)-2.75 E(pack)129.6 581.8 Q
(ets outstanding in the netw)-.11 E(ork.)-.11 E
(These parameters are manipulated, and their initial v)100.8 598.4 Q
(alues determined, according to SA)-.275 E(CK-)-.44 E(based TCP')100.8
611.4 Q 2.75(sb)-.605 G(eha)-2.75 E(vior)-.22 E 5.5(.T)-.605 G
(he rest of this section pro)-5.5 E(vides more speci\214c guidance.)
-.165 E(The sender MA)100.8 628 Q 2.75(Ys)-1.155 G
(end a data-carrying pack)-2.75 E(et only when pipe < cwnd.)-.11 E
(In particular)5.5 E 2.75(,i)-.44 G(t)-2.75 E(MUST NO)100.8 641 Q 2.75
(Ts)-.44 G(end a data-carrying pack)-2.75 E(et when pipe >= cwnd.)-.11 E
(Ev)5.5 E(ery data-carrying pack)-.165 E(et)-.11 E
(sent increases pipe by 1.)100.8 654 Q
(The sender reduces pipe as it infers that data-carrying pack)100.8
670.6 Q(ets ha)-.11 E .33 -.165(ve l)-.22 H(eft the netw).165 E
(ork, either)-.11 E(by being recei)100.8 683.6 Q -.165(ve)-.275 G 2.75
(do).165 G 2.75(rb)-2.75 G 2.75(yb)-2.75 G(eing dropped.)-2.75 E
(In particular:)5.5 E 13.224(\(1\) The)100.8 700.2 R
(sender reduces pipe by 1 for each pack)2.75 E(et ne)-.11 E(wly-ackno)
-.275 E(wledged as recei)-.275 E -.165(ve)-.275 G 2.75(d\().165 G(Ack)
-2.75 E -1.221(Ve)129.6 713.2 S
(ctor State 0 or State 1\) by some DCCP-Ack.)1.221 E(Flo)72 769 Q(yd/K)
-.11 E 284.171(ohler Section)-.385 F 2.75(5. [P)2.75 F(age 6])-.165 E 0
Cg EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 72.802(-DRAFT Expires:)-1.012 F
(August 2004)2.75 E(February 2004)103.569 E 13.224(\(2\) The)100.8 85 R
(sender reduces pipe by 1 for each pack)2.75 E
(et it can infer as lost due to the DCCP)-.11 E(equi)129.6 98 Q -.275
(va)-.275 G(lent of TCP').275 E 2.75(s")-.605 G(duplicate ackno)-2.75 E
2.75(wledgements". This)-.275 F(depends on TCP')2.75 E(s)-.605 E(NUMDUP)
129.6 111 Q -.44(AC)-1.012 G 2.75(Kp).44 G(arameter)-2.75 E 2.75(,t)-.44
G(he number of duplicate ackno)-2.75 E(wledgements TCP needs)-.275 E
(to infer a loss, which currently equals 3.)129.6 124 Q 2.75(Ap)5.5 G
(ack)-2.75 E(et P is inferred to be lost, rather than)-.11 E
(delayed, when at least NUMDUP)129.6 137 Q -.44(AC)-1.012 G 2.75(Kp).44
G(ack)-2.75 E(ets after P ha)-.11 E .33 -.165(ve b)-.22 H(een ackno).165
E(wledged as)-.275 E(recei)129.6 150 Q -.165(ve)-.275 G 2.75(d\().165 G
(Ack V)-2.75 E(ector State 0 or 1\) by the recei)-1.221 E -.165(ve)-.275
G 3.96 -.605(r. N).165 H(ote that these).605 E(ackno)129.6 163 Q
(wledgements are not duplicates, and that the ackno)-.275 E
(wledged pack)-.275 E(ets might)-.11 E(include DCCP-Ack pack)129.6 176 Q
(ets.)-.11 E 13.224(\(3\) Finally)100.8 192.6 R 2.75(,t)-.715 G
(he sender needs "retransmit" timeouts, handled lik)-2.75 E 2.75(eT)-.11
G(CP')-2.75 E 2.75(sr)-.605 G(etransmission)-2.75 E
(timeouts, in case an entire windo)129.6 205.6 Q 2.75(wo)-.275 G 2.75
(fp)-2.75 G(ack)-2.75 E(ets are lost.)-.11 E(The sender estimates the)
5.5 E(round-trip time at most once per windo)129.6 218.6 Q 2.75(wo)-.275
G 2.75(fd)-2.75 G(ata, and uses the TCP algorithms for)-2.75 E
(maintaining the a)129.6 231.6 Q -.165(ve)-.22 G
(rage round-trip time, mean de).165 E(viation, and timeout v)-.275 E
(alue.)-.275 E
(Because DCCP does not retransmit data, DCCP does not require TCP')129.6
244.6 Q(s)-.605 E(recommended minimum timeout of one second.)129.6 257.6
Q(The e)5.5 E(xponential back)-.165 E(of)-.11 E 2.75(fo)-.275 G 2.75(ft)
-2.75 G(he)-2.75 E(timer is e)129.6 270.6 Q(xactly as in TCP)-.165 E(.)
-1.221 E(When a "retransmit" timeout occurs, the sender sets pipe to 0.)
129.6 287.2 Q(The sender MUST NO)100.8 303.8 Q 2.75(Td)-.44 G
(ecrement pipe more than once for an)-2.75 E 2.75(yg)-.165 G -2.365
-.275(iv e)-2.75 H 2.75(np).275 G(ack)-2.75 E 2.75(et. T)-.11 F(rue)
-.385 E(duplicate ackno)100.8 316.8 Q(wledgements, for e)-.275 E
(xample, MUST not af)-.165 E(fect pipe.)-.275 E(Furthermore, the sender)
5.5 E(MUST NO)100.8 329.8 Q 2.75(Td)-.44 G
(ecrement pipe for non-data pack)-2.75 E(ets, such as DCCP-Acks, e)-.11
E -.165(ve)-.275 G 2.75(nt).165 G(hough the)-2.75 E(Ack V)100.8 342.8 Q
(ector will contain information about them.)-1.221 E(Congestion e)100.8
359.4 Q -.165(ve)-.275 G(nts, namely one or more pack).165 E
(ets lost or mark)-.11 E(ed from a windo)-.11 E 2.75(wo)-.275 G 2.75(fd)
-2.75 G(ata,)-2.75 E(cause CCID 2 to reduce its congestion windo)100.8
372.4 Q 4.18 -.715(w. F)-.275 H(or each congestion e).55 E -.165(ve)
-.275 G(nt, either indicated).165 E -.165(ex)100.8 385.4 S
(plicitly as an Ack V).165 E(ector State 1 \(ECN-mark)-1.221 E
(ed\) ackno)-.11 E(wledgement or inferred via)-.275 E("duplicate ackno)
100.8 398.4 Q(wledgements", cwnd is halv)-.275 E
(ed, then ssthresh is set to the ne)-.165 E 2.75(wc)-.275 G(wnd.)-2.75 E
(Cwnd is ne)100.8 411.4 Q -.165(ve)-.275 G 2.75(rr).165 G(educed belo)
-2.75 E 2.75(wo)-.275 G(ne pack)-2.75 E 2.75(et. After)-.11 F 2.75(at)
2.75 G(imeout, the slo)-2.75 E(w-start threshold is set to)-.275 E
(cwnd/2, then cwnd is set to one pack)100.8 424.4 Q 2.75(et. When)-.11 F
(halv)2.75 E(ed, cwnd and ssthresh ha)-.165 E .33 -.165(ve t)-.22 H
(heir v).165 E(alues)-.275 E(rounded do)100.8 437.4 Q(wn, e)-.275 E
(xcept that neither parameter is e)-.165 E -.165(ve)-.275 G 2.75(rl).165
G(ess than one.)-2.75 E
(When cwnd < ssthresh, meaning that the sender is in slo)100.8 454 Q
(w-start, the congestion windo)-.275 E 2.75(wi)-.275 G(s)-2.75 E
(increased by one pack)100.8 467 Q(et for e)-.11 E -.165(ve)-.275 G
(ry ne).165 E(wly ackno)-.275 E(wledged \(with Ack V)-.275 E
(ector State 0 or 1\) data-)-1.221 E(carrying pack)100.8 480 Q
(et, up to a maximum of Ack Ratio pack)-.11 E(ets per ackno)-.11 E 2.75
(wledgement. This)-.275 F(dif)100.8 493 Q(fers from TCP')-.275 E 2.75
(sh)-.605 G(istorical beha)-2.75 E(vior)-.22 E 2.75(,w)-.44 G
(hich \(in DCCP terms\) w)-2.75 E(ould increase cwnd by)-.11 E
(one per DCCP-Ack recei)100.8 506 Q -.165(ve)-.275 G
(d, not by one per pack).165 E(et ne)-.11 E(wly ackno)-.275 E
(wledged by some DCCP-)-.275 E(Ack; b)100.8 519 Q
(ut it is in line with TCP')-.22 E 2.75(sb)-.605 G(eha)-2.75 E
(vior with appropriate byte counting [RFC 3465].)-.22 E
(When cwnd >= ssthresh, the congestion windo)100.8 532 Q 2.75(wi)-.275 G
2.75(si)-2.75 G(ncreased by one pack)-2.75 E(et for e)-.11 E -.165(ve)
-.275 G(ry).165 E(windo)100.8 545 Q 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata ackno)-2.75 E(wledged without lost or mark)-.275 E(ed pack)-.11 E
2.75(ets. The)-.11 F(cwnd parameter is)2.75 E
(initialized to four for ne)100.8 558 Q 2.75(wc)-.275 G
(onnections [RFC 3390]; the ssthresh parameter is initialized to)-2.75 E
(an arbitrarily high v)100.8 571 Q(alue.)-.275 E/F1 11/Times-Bold@0 SF
(5.1.)72 597 Q/F2 13/Times-Bold@0 SF(Response to Data Dr)5.5 E(opped)
-.234 E F0(CCID 2 senders respond to pack)100.8 613.6 Q(ets ackno)-.11 E
(wledged as Data Dropped as described in)-.275 E([DCCP], with the follo)
100.8 626.6 Q(wing further clari\214cations.)-.275 E<83>100.8 643.2 Q F1
(Dr)7.15 E(op Code 2 \("r)-.198 E(ecei)-.198 E .22 -.11(ve b)-.11 H
(uffer dr)-.11 E(op"\).)-.198 E F0(The congestion windo)5.5 E 2.75(w")
-.275 G(cwnd" is reduced by)-2.75 E(one for each pack)111.8 656.2 Q
(et ne)-.11 E(wly ackno)-.275 E(wledged as Drop Code 2, e)-.275 E
(xcept that it is ne)-.165 E -.165(ve)-.275 G 2.75(rr).165 G(educed)
-2.75 E(belo)111.8 669.2 Q 2.75(wo)-.275 G(ne.)-2.75 E F1(5.2.)72 695.2
Q F2 -.13(Pa)5.5 G(ck).13 E(et Size)-.13 E F0
(CCID 2 is intended for applications that use a \214x)100.8 711.8 Q
(ed pack)-.165 E(et size, and that v)-.11 E(ary their sending)-.275 E
(rate in pack)100.8 724.8 Q(ets per second in response to congestion.)
-.11 E(CCID 2 is not appropriate for)5.5 E(Flo)72 769 Q(yd/K)-.11 E
275.921(ohler Section)-.385 F 2.75(5.2. [P)2.75 F(age 7])-.165 E 0 Cg EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 72.802(-DRAFT Expires:)-1.012 F
(August 2004)2.75 E(February 2004)103.569 E
(applications that require a \214x)100.8 85 Q(ed interv)-.165 E
(al of time between pack)-.275 E(ets, and v)-.11 E(ary their pack)-.275
E(et size)-.11 E(instead of their pack)100.8 98 Q
(et rate in response to congestion.)-.11 E(Ho)5.5 E(we)-.275 E -.165(ve)
-.275 G .88 -.44(r, s).165 H(ome attention might be).44 E
(required for applications using CCID 2 that v)100.8 111 Q
(ary their pack)-.275 E(et size not in response to)-.11 E(congestion, b)
100.8 124 Q(ut in response to other application-le)-.22 E -.165(ve)-.275
G 2.75(lr).165 G(equirements.)-2.75 E(CCID 2 implementations MA)100.8
140.6 Q 2.75(Yc)-1.155 G
(heck for applications that appear to be manipulating the)-2.75 E(pack)
100.8 153.6 Q(et size inappropriately)-.11 E 5.5(.F)-.715 G(or e)-5.665
E(xample, an application might send small pack)-.165 E(ets for a)-.11 E
(while, b)100.8 166.6 Q(uilding up a f)-.22 E
(ast rate, then switch to lar)-.11 E(ge pack)-.198 E(ets to tak)-.11 E
2.75(ea)-.11 G(dv)-2.75 E(antage of the f)-.275 E(ast rate.)-.11 E(Ho)
100.8 179.6 Q(we)-.275 E -.165(ve)-.275 G .88 -.44(r, p).165 H(relimina\
ry simulations indicate that applications may not be able to increase)
.44 E(their o)100.8 192.6 Q -.165(ve)-.165 G(rall transfer rates this w)
.165 E(ay)-.11 E 2.75(,s)-.715 G 2.75(oi)-2.75 G 2.75(ti)-2.75 G 2.75
(sn)-2.75 G(ot clear this manipulation will occur in)-2.75 E(practice.)
100.8 205.6 Q/F1 11/Times-Bold@0 SF(6.)72 231.6 Q/F2 14/Times-Bold@0 SF
(Ackno)5.5 E(wledgements)-.14 E F0(This section describes ho)100.8 248.2
Q 2.75(wt)-.275 G(he recei)-2.75 E -.165(ve)-.275 G 2.75(rr).165 G
(eports ackno)-2.75 E(wledgement information back to the)-.275 E(sender)
100.8 261.2 Q 5.5(.D)-.605 G(CCP-Ack pack)-5.5 E(ets from the recei)-.11
E -.165(ve)-.275 G 2.75(rM).165 G(UST include Ack V)-2.75 E
(ector options, as well)-1.221 E(as an Ackno)100.8 274.2 Q
(wledgement Number ackno)-.275 E(wledging the pack)-.275 E
(et with the lar)-.11 E(gest v)-.198 E(alid sequence)-.275 E
(number recei)100.8 287.2 Q -.165(ve)-.275 G 2.75(df).165 G
(rom the sender)-2.75 E 5.5(.A)-.605 G(ckno)-5.5 E
(wledgement data in the Ack V)-.275 E(ector options)-1.221 E
(SHOULD generally co)100.8 300.2 Q -.165(ve)-.165 G 2.75(rt).165 G
(he recei)-2.75 E -.165(ve)-.275 G(r').165 E 2.75(se)-.605 G
(ntire Ackno)-2.75 E(wledgement W)-.275 E(indo)-.44 E 1.43 -.715(w, a)
-.275 H 2.75(sd).715 G(escribed in)-2.75 E([DCCP].)100.8 313.2 Q F1
(6.1.)72 339.2 Q/F3 13/Times-Bold@0 SF(Congestion Contr)5.5 E
(ol on Ackno)-.234 E(wledgements)-.13 E F0(The ackno)100.8 355.8 Q
(wledgement sub\215o)-.275 E 2.75(wi)-.275 G 2.75(sl)-2.75 G
(oosely congestion-controlled by an Ack Ratio speci\214ed)-2.75 E
(by the sender)100.8 368.8 Q 5.5(.T)-.605 G(he recei)-5.5 E -.165(ve)
-.275 G 2.75(rs).165 G(ends approximately \(cwnd / Ack Ratio\) ackno)
-2.75 E(wledgement)-.275 E(pack)100.8 381.8 Q
(ets for each congestion windo)-.11 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata pack)-2.75 E 2.75(ets. When)-.11 F(the ackno)2.75 E
(wledgement stream)-.275 E
(is congested, the sender will increase the recei)100.8 394.8 Q -.165
(ve)-.275 G(r').165 E 2.75(sA)-.605 G(ck Ratio, limiting its)-2.75 E
(ackno)100.8 407.8 Q(wledgement rate.)-.275 E(This dif)5.5 E
(fers from TCP)-.275 E 2.75(,w)-1.221 G
(hich presently has no congestion control)-2.75 E(for pure ackno)100.8
420.8 Q(wledgement traf)-.275 E(\214c.)-.275 E
(In the absence of congestion on the ack stream, CCID 2 ackno)100.8
437.4 Q(wledgements will be sent in)-.275 E(roughly the same w)100.8
450.4 Q(ay as TCP ackno)-.11 E 2.75(wledgements. F)-.275 F
(or instance, the Ack Ratio will be set)-.165 E(to 2, leading to beha)
100.8 463.4 Q(vior lik)-.22 E 2.75(eT)-.11 G(CP')-2.75 E 2.75(sd)-.605 G
(elayed acks.)-2.75 E(When the ack stream is congested,)5.5 E
(CCID 2 does not try to be TCP-friendly)100.8 476.4 Q 2.75(,b)-.715 G
(ut just tries to a)-2.97 E -.22(vo)-.22 G
(id congestion collapse, and to).22 E(be some)100.8 489.4 Q
(what better than TCP in e)-.275 E
(xplicitly reducing the ack sending rate in the presence of)-.165 E 2.75
(ah)100.8 502.4 S(igh pack)-2.75 E
(et loss or marking rate on the return path.)-.11 E F1 2.75
(6.1.1. Sending)72 528.4 R(Ackno)2.75 E(wledgements)-.11 E F0 2.75(AC)
100.8 545 S(CID 2 recei)-2.75 E -.165(ve)-.275 G 2.75(rS).165 G
(HOULD send one ackno)-2.75 E(wledgement for e)-.275 E -.165(ve)-.275 G
(ry Ack Ratio data pack).165 E(ets)-.11 E(it recei)100.8 558 Q -.165(ve)
-.275 G(s.).165 E(This is only a rough guideline, ho)100.8 574.6 Q(we)
-.275 E -.165(ve)-.275 G 3.96 -.605(r. W).165 H 2.75(ei)-.275 G
(ntend CCID 2')-2.75 E 2.75(sa)-.605 G(ckno)-2.75 E(wledgement beha)
-.275 E(vior)-.22 E(to resemble TCP')100.8 587.6 Q 2.75(sw)-.605 G
(hen there is no ack-stream congestion, and to be some)-2.75 E
(what more)-.275 E(conserv)100.8 600.6 Q(ati)-.275 E .33 -.165(ve w)
-.275 H(hen there is ack-stream congestion; follo).165 E
(wing this intent is more important)-.275 E
(than implementing Ack Ratio precisely)100.8 613.6 Q 5.5(.S)-.715 G
(uggested v)-5.5 E(ariations from strict Ack Ratio)-.275 E
(compliance include:)100.8 626.6 Q 13.224(\(1\) If)100.8 643.2 R
(the HC-Recei)2.75 E -.165(ve)-.275 G .88 -.44(r, D).165 H
(CCP B, is not quiescent---it is acti).44 E -.165(ve)-.275 G
(ly sending data---then its).165 E(ackno)129.6 656.2 Q
(wledgements may be piggyback)-.275 E(ed on its data pack)-.11 E 2.75
(ets. It)-.11 F(is acceptable in this)2.75 E
(case to send more piggyback)129.6 669.2 Q(ed ackno)-.11 E
(wledgements than the Ack Ratio w)-.275 E(ould)-.11 E 2.75(suggest. If)
129.6 682.2 R(the data pack)2.75 E(ets are too big to carry ackno)-.11 E
(wledgement information, or)-.275 E(the data sending rate is too lo)
129.6 695.2 Q 1.43 -.715(w, t)-.275 H(hen DCCP B SHOULD send some pure)
.715 E(ackno)129.6 708.2 Q(wledgements as well as piggyback)-.275 E
(ed data-plus-ackno)-.11 E(wledgement pack)-.275 E(ets, to)-.11 E
(maintain the rate of one ackno)129.6 721.2 Q
(wledgement per Ack Ratio recei)-.275 E -.165(ve)-.275 G 2.75(dd).165 G
(ata pack)-2.75 E(ets.)-.11 E(Flo)72 769 Q(yd/K)-.11 E 267.671
(ohler Section)-.385 F 2.75(6.1.1. [P)2.75 F(age 8])-.165 E 0 Cg EP
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/F0 11/Times-Roman@0 SF(INTERNET)72 49 Q 72.802(-DRAFT Expires:)-1.012 F
(August 2004)2.75 E(February 2004)103.569 E 13.224(\(2\) The)100.8 85 R
(recei)2.75 E -.165(ve)-.275 G 2.75(rS).165 G
(HOULD implement an algorithm lik)-2.75 E 2.75(eT)-.11 G(CP')-2.75 E
2.75(sd)-.605 G(elayed)-2.75 E(ackno)129.6 98 Q(wledgements, whereby e)
-.275 E -.165(ve)-.275 G(ry data pack).165 E(et is ackno)-.11 E
(wledged within at most T)-.275 E(seconds of its receipt, re)129.6 111 Q
-.055(ga)-.165 G(rdless of Ack Ratio.).055 E(The delayed-ack timeout T)
5.5 E(SHOULD be set as for TCP---to 200 milliseconds, for e)129.6 124 Q
(xample.)-.165 E/F1 11/Times-Bold@0 SF 2.75(6.1.2. Setting)72 150 R
(Ack Ratio)2.75 E F0(There are three guidelines for setting Ack Ratio.)
100.8 166.6 Q(First, it is al)5.5 E -.11(wa)-.11 G(ys an inte).11 E(ger)
-.165 E 5.5(.S)-.605 G(econd, it)-5.5 E(should not e)100.8 179.6 Q
(xceed half the congestion windo)-.165 E 1.43 -.715(w, r)-.275 H
(ounded up \(e).715 E(xcept that Ack Ratio 2 is)-.165 E(al)100.8 192.6 Q
-.11(wa)-.11 G(ys acceptable\).).11 E(Third, it should be tw)5.5 E 2.75
(oo)-.11 G 2.75(rl)-2.75 G(ar)-2.75 E(ger for a congestion windo)-.198 E
2.75(wo)-.275 G 2.75(ff)-2.75 G(our or)-2.75 E(more pack)100.8 205.6 Q
(ets.)-.11 E(DCCP-Ack pack)100.8 222.2 Q(ets from the recei)-.11 E -.165
(ve)-.275 G 2.75(rc).165 G
(ontain sequence numbers, so the sender can infer)-2.75 E
(when DCCP-Ack pack)100.8 235.2 Q(ets are lost.)-.11 E
(The sender considers a DCCP-Ack pack)5.5 E(et lost if at least)-.11 E
(NUMDUP)100.8 248.2 Q -.44(AC)-1.012 G 2.75(Kp).44 G(ack)-2.75 E
(ets with higher sequence numbers ha)-.11 E .33 -.165(ve b)-.22 H
(een recei).165 E -.165(ve)-.275 G 2.75(df).165 G(rom the)-2.75 E(recei)
100.8 261.2 Q -.165(ve)-.275 G 3.96 -.605(r. \().165 H(Ag).605 E
(ain, NUMDUP)-.055 E -.44(AC)-1.012 G 2.75(Ke).44 G(quals 3.\))-2.75 E
(If DCCP-Ack pack)5.5 E(ets from the recei)-.11 E -.165(ve)-.275 G 2.75
(ra).165 G(re)-2.75 E(mark)100.8 274.2 Q(ed in the netw)-.11 E
(ork, the sender sees these marks directly)-.11 E(.)-.715 E
(DCCP responds to congestion e)100.8 290.8 Q -.165(ve)-.275 G
(nts on the return path by modifying the Ack Ratio,).165 E
(loosely emulating TCP)100.8 303.8 Q 5.5(.F)-1.221 G
(or each congestion windo)-5.665 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata with lost or mark)-2.75 E(ed DCCP-)-.11 E(Ack pack)100.8 316.8 Q
(ets, the Ack Ratio is doubled, subject to the constraints noted abo)
-.11 E -.165(ve)-.165 G 5.5(.S).165 G(imilarly)-5.5 E 2.75(,i)-.715 G(f)
-2.75 E(the Ack Ratio is R, then for each \(cwnd/\(R^2 - R\)\) congesti\
on windo)100.8 329.8 Q(ws of data with no lost)-.275 E(or mark)100.8
342.8 Q(ed DCCP-Ack pack)-.11 E
(ets, the Ack Ratio is decreased by 1, ag)-.11 E(ain subject to the)
-.055 E(constraints on the Ack Ratio.)100.8 355.8 Q
(See the section belo)5.5 E 2.75(wf)-.275 G(or the deri)-2.75 E -.275
(va)-.275 G 2.75(tion. F).275 F(or a constant)-.165 E(congestion windo)
100.8 368.8 Q 1.43 -.715(w, t)-.275 H(his gi).715 E -.165(ve)-.275 G
2.75(sa).165 G 2.75(nA)-2.75 G
(ck sending rate that is roughly TCP-friendly)-2.75 E(.)-.715 E
(The sender need not k)100.8 385.4 Q(eep the recei)-.11 E -.165(ve)-.275
G(r').165 E 2.75(sA)-.605 G(ck Ratio completely up to date.)-2.75 E
-.165(Fo)5.5 G 2.75(ri).165 G(nstance, it)-2.75 E(MA)100.8 398.4 Q 2.75
(Yr)-1.155 G(ate-limit Ack Ratio rene)-2.75 E(gotiations to once e)-.165
E -.165(ve)-.275 G(ry four or \214v).165 E 2.75(er)-.165 G
(ound-trip times, or to)-2.75 E(once e)100.8 411.4 Q -.165(ve)-.275 G
(ry second or tw).165 E 2.75(o. Additionally)-.11 F 2.75(,i)-.715 G 2.75
(tM)-2.75 G 2.31 -1.155(AY b)-2.75 H(ound Ack Ratio belo)1.155 E 2.75
(wb)-.275 G 2.75(yt)-2.75 G -.11(wo)-2.75 G 2.75(,o).11 G 2.75(ri)-2.75
G(t)-2.75 E(MA)100.8 424.4 Q 2.75(Ys)-1.155 G(et Ack Ratio to one for h\
alf-connections with persistent congestion windo)-2.75 E(ws of 1 or)
-.275 E 2.75(2p)100.8 437.4 S(ack)-2.75 E(ets.)-.11 E
(Since the sending rate for ackno)100.8 454 Q(wledgement pack)-.275 E
(ets changes as a function of both the Ack)-.11 E
(Ratio and the congestion windo)100.8 467 Q 1.43 -.715(w, t)-.275 H
(he dynamics will be rather comple).715 E(x, and this Ack)-.165 E
(congestion control mechanism is intended only to be v)100.8 480 Q
(ery roughly TCP-friendly)-.165 E(.)-.715 E
(As a result of the constraints gi)100.8 496.6 Q -.165(ve)-.275 G 2.75
(ne).165 G(arlier in this section, the recei)-2.75 E -.165(ve)-.275 G
2.75(ra).165 G -.11(lwa)-2.75 G(ys sends at least).11 E(one ack pack)
100.8 509.6 Q(et for a congestion windo)-.11 E 2.75(wo)-.275 G 2.75(fo)
-2.75 G(ne pack)-2.75 E(et, and the recei)-.11 E -.165(ve)-.275 G 2.75
(ra).165 G -.11(lwa)-2.75 G(ys sends at).11 E(least tw)100.8 522.6 Q
2.75(oa)-.11 G(ck pack)-2.75 E(ets per windo)-.11 E 2.75(wo)-.275 G 2.75
(fd)-2.75 G(ata otherwise.)-2.75 E(Thus, the recei)5.5 E -.165(ve)-.275
G 2.75(rc).165 G(ould be sending)-2.75 E(tw)100.8 535.6 Q 2.75(oa)-.11 G
(ck pack)-2.75 E(ets per windo)-.11 E 2.75(wo)-.275 G 2.75(fd)-2.75 G
(ata e)-2.75 E -.165(ve)-.275 G 2.75(ni).165 G 2.75(nt)-2.75 G(he f)
-2.75 E(ace of v)-.11 E(ery hea)-.165 E(vy congestion on the)-.22 E(re)
100.8 548.6 Q -.165(ve)-.275 G(rse path.).165 E 1.76 -.88(We w)5.5 H
(ould note, ho).77 E(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H
(hat if congestion is suf).44 E(\214ciently hea)-.275 E(vy that all of)
-.22 E(the ack pack)100.8 561.6 Q(ets are dropped, then the sender f)
-.11 E(alls back on a timeout, and the e)-.11 E(xponential)-.165 E(back)
100.8 574.6 Q(of)-.11 E 2.75(fo)-.275 G 2.75(ft)-2.75 G(he timer)-2.75 E
2.75(,a)-.44 G 2.75(si)-2.75 G 2.75(nT)-2.75 G(CP)-2.75 E 5.5(.T)-1.221
G(hus, if congestion is suf)-5.5 E(\214ciently hea)-.275 E(vy on the re)
-.22 E -.165(ve)-.275 G(rse).165 E
(path, then the sender reduces its sending rate on the forw)100.8 587.6
Q(ard path, which reduces the rate)-.11 E(on the re)100.8 600.6 Q -.165
(ve)-.275 G(rse path as well.).165 E(The sender sets the recei)100.8
617.2 Q -.165(ve)-.275 G(r').165 E 2.75(sA)-.605 G
(ck Ratio by sending "Change L\(Ack Ratio\)" options, either)-2.75 E
(on its data pack)100.8 630.2 Q(ets or on separate ackno)-.11 E
(wledgements.)-.275 E F1 2.75(6.1.3. Deri)72 656.2 R -.11(va)-.11 G
(tion of Ack Ratio Decr).11 E(ease)-.198 E F0(The congestion a)100.8
672.8 Q -.22(vo)-.22 G
(idance phase of TCP increases cwnd by one MSS for e).22 E -.165(ve)
-.275 G(ry congestion-).165 E(free windo)100.8 685.8 Q 4.18 -.715(w. A)
-.275 H(pplying this congestion a).715 E -.22(vo)-.22 G(idance beha).22
E(vior to the ack traf)-.22 E(\214c, this w)-.275 E(ould)-.11 E
(correspond to increasing the number of DCCP-Ack pack)100.8 698.8 Q
(ets per windo)-.11 E 2.75(wb)-.275 G 2.75(yo)-2.75 G(ne after e)-2.75 E
-.165(ve)-.275 G(ry).165 E(congestion-free windo)100.8 711.8 Q 2.75(wo)
-.275 G 2.75(fD)-2.75 G(CCP-Ack pack)-2.75 E 2.75(ets. W)-.11 F 2.75(ec)
-.88 G(annot achie)-2.75 E .33 -.165(ve t)-.275 H(his e).165 E
(xactly using the)-.165 E(Ack Ratio, since the Ack Ratio is an inte)
100.8 724.8 Q(ger)-.165 E 5.5(.I)-.605 G
(nstead, we must decrease the Ack Ratio by)-5.5 E(Flo)72 769 Q(yd/K)-.11
E 267.671(ohler Section)-.385 F 2.75(6.1.3. [P)2.75 F(age 9])-.165 E 0
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(August 2004)2.75 E(February 2004)103.569 E(one after K windo)100.8 85 Q
(ws ha)-.275 E .33 -.165(ve b)-.22 H(een sent without a congestion e)
.165 E -.165(ve)-.275 G(nt on the re).165 E -.165(ve)-.275 G
(rse path, where).165 E 2.75(Ki)100.8 98 S 2.75(sc)-2.75 G
(hosen so that the long-term number of DCCP-Ack pack)-2.75 E
(ets per congestion windo)-.11 E 2.75(wi)-.275 G(s)-2.75 E
(roughly TCP-friendly)100.8 111 Q 2.75(,f)-.715 G(ollo)-2.75 E
(wing AIMD congestion control.)-.275 E(In CCID 2, K = \(cwnd/\(R^2 - R\
\)\), where R is the current Ack Ratio. This result w)100.8 127.6 Q(as)
-.11 E(calculated as follo)100.8 140.6 Q(ws:)-.275 E/F1 11/Courier@0 SF
6.6(R=A)180 159.6 S(ck Ratio = # data packets / ack packets, and)-6.6 E
6.6(W=C)180 172.6 S(ongestion Window = # data packets / window, so)-6.6
E(W/R = # ack packets / window.)166.8 185.6 Q
(Requirement: Increase W/R by 1 per congestion-free window.)127.2 211.6
Q(But can only reduce R by increments of one.)127.2 224.6 Q
(Therefore, find K so that, after K congestion-free windows,)127.2 250.6
Q(the adjusted W/R would equal W/\(R-1\).)127.2 263.6 Q
(\(W/R\) + K = W/\(R-1\), so)127.2 289.6 Q 6.6(K=W)180 302.6 S
(/\(R-1\) - W/R = W/\(R^2 - R\).)-6.6 E/F2 11/Times-Bold@0 SF(6.2.)72
334.6 Q/F3 13/Times-Bold@0 SF(Quiescence)5.5 E F0(This section refers t\
o quiescence in the DCCP sense \(see section 8.1 of [DCCP]\): Ho)100.8
351.2 Q(w)-.275 E(does a CCID 2 recei)100.8 364.2 Q -.165(ve)-.275 G
2.75(rd).165 G(etermine that the corresponding sender is not sending an)
-2.75 E 2.75(yd)-.165 G(ata?)-2.75 E
(Let T equal the greater of 0.2 seconds and tw)100.8 380.8 Q 2.75(or)
-.11 G(ound-trip times.)-2.75 E(\(The recei)5.5 E -.165(ve)-.275 G 2.75
(rm).165 G(ay kno)-2.75 E(w)-.275 E(the round-trip time in its role as \
the sender for the other half-connection; or if it does not, it)100.8
393.8 Q(SHOULD use an estimated R)100.8 406.8 Q(TT of 0.2 seconds.\))
-.66 E(The recei)5.5 E -.165(ve)-.275 G 2.75(rd).165 G
(etects that the sender has)-2.75 E
(gone quiescent when at least T seconds ha)100.8 419.8 Q .33 -.165(ve p)
-.22 H(assed without recei).165 E(ving an)-.275 E 2.75(ya)-.165 G
(dditional data)-2.75 E(from the sender)100.8 432.8 Q 2.75(,a)-.44 G
(nd the sender has ackno)-2.75 E(wledged recei)-.275 E -.165(ve)-.275 G
2.75(rA).165 G(ck V)-2.75 E(ectors that co)-1.221 E -.165(ve)-.165 G
(red all).165 E(data pack)100.8 445.8 Q(ets sent.)-.11 E
(That is, once the sender ackno)5.5 E(wledges the recei)-.275 E -.165
(ve)-.275 G(r').165 E 2.75(sA)-.605 G(ck V)-2.75 E(ectors and)-1.221 E
(the sender has not sent additional data for at least T)100.8 458.8 Q
2.75(,t)-.814 G(he recei)-2.75 E -.165(ve)-.275 G 2.75(rc).165 G
(an determine that the)-2.75 E(sender is quiescent.)100.8 471.8 Q F2
(6.3.)72 497.8 Q F3(Ackno)5.5 E(wledgements of Ackno)-.13 E(wledgements)
-.13 E F0(The sender)100.8 514.4 Q 2.75(,D)-.44 G
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(automatically contained in A)100.8 566.4 Q 1.21 -.605('s a)-1.221 H
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100.8 703.6 Q(If ECN is)5.5 E
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100.8 716.6 Q(ets, follo)-.11 E(wing the)-.275 E(Flo)72 769 Q(yd/K)-.11
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([RFC 2581] discusses w)100.8 389 Q(ays that an attack)-.11 E
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(connection by dropping pack)100.8 402 Q(ets, or by for)-.11 E(ging e)
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-2.75 E F1(11.)72 496.6 Q F2(Thanks)5.5 E F0 1.76 -.88(We t)100.8 513.2
T(hank Mark Handle).88 E 2.75(ya)-.165 G(nd Jitendra P)-2.75 E(adh)-.165
E(ye for their help in de\214ning CCID 2.)-.055 E 1.76 -.88(We a)5.5 H
(lso).88 E(thank Gre)100.8 526.2 Q 2.75(gM)-.165 G(inshall and Arun V)
-2.75 E(enkataramani for feedback on this document.)-1.221 E F2(Normati)
72 552.2 Q .28 -.14(ve R)-.14 H(efer).14 E(ences)-.252 E F0([DCCP] E. K)
100.8 568.8 Q(ohler)-.385 E 2.75(,M)-.44 G 2.75(.H)-2.75 G(andle)-2.75 E
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(Congestion Control Protocol,)2.75 E(draft-ietf-dccp-spec-06.txt, w)
129.6 581.8 Q(ork in progress, February 2004.)-.11 E
([RFC 793] J. Postel, editor)100.8 598.4 Q 5.5(.T)-.605 G
(ransmission Control Protocol.)-5.885 E(RFC 793.)5.5 E
([RFC 2026] S. Bradner)100.8 615 Q 5.5(.T)-.605 G
(he Internet Standards Process -- Re)-5.5 E(vision 3.)-.275 E(RFC 2026.)
5.5 E([RFC 2119] S. Bradner)100.8 631.6 Q 5.5(.K)-.605 G .33 -.165(ey W)
-5.775 H(ords F)-.715 E(or Use in RFCs to Indicate Requirement Le)-.165
E -.165(ve)-.275 G(ls.).165 E(RFC 2119.)129.6 644.6 Q
([RFC 2581] M. Allman, V)100.8 661.2 Q 2.75(.P)-1.419 G(axson, and W)
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([RFC 3168] K.K. Ramakrishnan, S. Flo)100.8 677.8 Q(yd, and D. Black.)
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(yd, and C. P)-.11 E 2.75(artridge. Increasing)-.165 F(TCP')2.75 E 2.75
(sI)-.605 G(nitial W)-2.75 E(indo)-.44 E -.715(w.)-.275 G(RFC 3390.)
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ongestion Control with Appropriate Byte Counting \(ABC\).)100.8 85 Q
(RFC 3465.)129.6 98 Q([RFC 3517] E. Blanton, M. Allman, K. F)100.8 114.6
Q(all, and L. W)-.165 E 2.75(ang. A)-.88 F(Conserv)2.75 E(ati)-.275 E
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 users of this speci\214cation can be)100.8 527.4 Q
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(Full Copyright Statement)72 566.4 Q F0(Cop)100.8 583 Q
(yright \(C\) The Internet Society \(2004\).)-.11 E(All Rights Reserv)
5.5 E(ed.)-.165 E(This document and translations of it may be copied an\
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100.8 690.6 Q
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(This document and the information contained herein is pro)100.8 114.6 Q
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(THE INTERNET SOCIETY AND THE INTERNET ENGINEERING T)100.8 127.6 Q
(ASK FORCE)-1.023 E(DISCLAIMS ALL W)100.8 140.6 Q
(ARRANTIES, EXPRESS OR IMPLIED, INCLUDING B)-1.32 E(UT NO)-.11 E(T)-.44
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