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/F0 10/Courier-Bold@0 SF(Internet Engineering Task Force)72 85 Q 258
(INTERNET-DRAFT Damon)72 98 R(Lanphear)6 E 138
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(25 October 2002)414 124 Q(Expires: April 2003)390 137 Q/F1 14
/Times-Bold@0 SF(Datagram Congestion Contr)109.003 162 Q(ol Pr)-.252 E
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is an Internet-Draft and is in full conformance with all pro)100.8 223.6
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E(Congestion Control Protocol \(DCCP\) and its interf)97 447.2 Q
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(1. Introduction)97 123 Q F0 11(......................)3.56 G F2(4)11.5
E(2. Considerations for T)97 135 Q(ar)-.8 E(get Applications)-.18 E F0
11(..............)7.61 G F2(4)11.5 E(2.1. Real T)107 147 Q
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(2.1.1. The Post Netw)117 159 Q(ork Buf)-.1 E(fer and Rate Control)-.25
E F0 11(..........)11.15 G F2(5)11.5 E
(2.1.2. Decode Costs and Media Adaptation)117 171 Q F0 11(............)
8.3 G F2(5)11.5 E(2.1.3. Selecti)117 183 Q .3 -.15(ve T)-.25 H
(ransmission and Retransmission)-.2 E F0 11(..........)9.59 G F2(5)11.5
E(2.1.4. Latenc)117 195 Q 2.5(yR)-.15 G(equirements)-2.5 E F0 11
(................)10.39 G F2(6)11.5 E(2.1.5. R)117 207 Q(TP/R)-.6 E(TCP)
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(elephon)-.7 E(y)-.15 E F0 11(...................)5.94 G F2(7)11.5 E
(2.1.7. V)117 231 Q(ideo T)-.6 E(eleconferencing)-.7 E F0 11
(................)4.89 G F2(7)11.5 E
(2.1.8. Multi-Player Game Applications)117 243 Q F0 11(.............)
10.65 G F2(7)11.5 E(2.2. Cross Application Issues)107 255 Q F0 11
(.................)4.81 G F2(7)11.5 E(2.2.1. Loss Signaling)117 267 Q F0
11(..................)13.27 G F2(7)11.5 E(2.2.2. Drop Preference)117 279
Q F0 11(..................)7.2 G F2(7)11.5 E(2.2.3. Mobility)117 291 Q
F0 11(....................)10.49 G F2(7)11.5 E
(2.2.4. Send Option on Option Change W)117 303 Q(ith or W)-.4 E
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(2.2.5. Protocol Information Shared with Ov)117 315 Q(erlying Layers)
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(3. API and Con\214guration Considerations)97 327 Q F0 11
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(....................)7.44 G F2(8)11.5 E(3.1.1. Con\214gurable V)117 351
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(ariables Speci\214c to an API Implementation)-1.11 E F0 11(......)4.69
G F2(9)11.5 E(3.1.2.1. Feature Ne)127 375 Q(gotiation Limit)-.15 E F0 11
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(3.1.2.6. Buf)127 435 Q(fer Close Drop Noti\214cation)-.25 E F0 11
(............)13.54 G F2(10)6.5 E(3.1.2.7. Drop Preference)127 447 Q F0
11(.................)3.45 G F2(10)6.5 E(3.1.2.8. Mobile Recei)127 459 Q
-.15(ve)-.25 G 2.5(rD).15 G(rop Beha)-2.5 E(vior Preference)-.2 E F0 11
(.........)5.46 G F2(10)6.5 E(3.1.2.9. Use Service Name)127 471 Q F0 11
(................)8.58 G F2(10)6.5 E(3.1.2.10. Minimal Buf)127 483 Q
(fering Option)-.25 E F0 11(.............)13.39 G F2(10)6.5 E
(3.1.2.11. PMTU Change Beha)127 495 Q(vior)-.2 E F0 11(..............)
5.71 G F2(11)6.5 E(3.2. Connection Establishment and T)107 507 Q
(ermination)-.7 E F0 11(...........)13.29 G F2(11)6.5 E
(3.2.1. Connection Establishment)117 519 Q F0 11(...............)8.97 G
F2(11)6.5 E(3.2.2. Data Piggybacking)117 531 Q F0 11(.................)
10.37 G F2(11)6.5 E(3.2.3. Connection T)117 543 Q(ermination)-.7 E F0 11
(................)3.15 G F2(11)6.5 E(3.3. Feature Ne)107 555 Q
(gotiation)-.15 E F0 11(..................)10.94 G F2(11)6.5 E
(3.3.1. Ne)117 567 Q(gotiable Features)-.15 E F0 11(.................)
6.64 G F2(11)6.5 E(3.3.2. Impact on Con\214guration Interf)117 579 Q
(aces)-.1 E F0 11(.............)1.6 G F2(12)6.5 E
(3.3.3. Feature options with data)117 591 Q F0 11(...............)12.87
G F2(12)6.5 E(3.3.4. Impact of feature ne)117 603 Q
(gotiation on I/O semantics)-.15 E F0 11(.........)10.27 G F2(12)6.5 E
(3.4. Error Codes)107 615 Q F0 11(.....................).65 G F2(12)6.5
E(3.5. Statistics)107 627 Q F0 11(.....................)13.13 G F2(13)
6.5 E(4. Implementation Considerations)97 639 Q F0 11(................)
9.67 G F2(13)6.5 E(4.1. Connection State)107 651 Q F0 11
(...................)8.14 G F2(13)6.5 E(4.2. Pro)107 663 Q
(vision of sequence number)-.15 E 2.5(,a)-.4 G
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(4.3. Probabilistic V)107 675 Q
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-2.75 E(wer le)-.275 E -.165(ve)-.275 G 2.75(ls).165 G(ervice be)-2.75 E
(gs the)-.165 E(question of an API speci\214cation.)100.8 196.2 Q
(This te)5.5 E(xt does not assume a speci\214c API paradigm.)-.165 E
(Rather)100.8 209.2 Q 2.75(,A)-.44 G
(PI issues are discussed in the abstract.)-2.75 E
(The purpose of which is to allo)5.5 E 2.75(wt)-.275 G(he)-2.75 E(reade\
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scussion to a)100.8 222.2 Q(particular problem domain. An e)100.8 235.2
Q(xample implementation using a speci\214c API is presented,)-.165 E(ho)
100.8 248.2 Q(we)-.275 E -.165(ve)-.275 G .88 -.44(r, a).165 H 2.75(sam)
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-2.75 E(terms.)100.8 261.2 Q
(DCCP presents a set of unique challenges to the pro)100.8 277.8 Q
(vision of an application interf)-.165 E(ace.)-.11 E
(These challenges are compounded by the f)100.8 290.8 Q(act that man)
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100.8 303.8 Q(ernel space.)-.11 E
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(\214cient for the most complete e)-.275 E(xposure of DCCP')-.165 E 2.75
(ss)-.605 G 2.75(ervices. Mitig)-2.75 F(ating the trade of)-.055 E(f)
-.275 E(between DCCP functionality muted by an API and pro)100.8 329.8 Q
(viding a suf)-.165 E(\214ciently \215e)-.275 E(xible API)-.165 E
(considered throughout this document.)100.8 342.8 Q(The reader')100.8
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(wledge of DCCP and its design rationale are assumed.)-.275 E(Re)5.5 E
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100.8 372.4 Q(OBLEM] before)-.44 E
(reading this document is therefore suggested.)100.8 385.4 Q F1(2.)72
411.4 Q F2(Considerations f)5.5 E(or T)-.35 E(ar)-1.288 E(get A)-.14 E
(pplications)-.35 E F0(DCCP speci\214cally tar)100.8 428 Q
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 needs of the)100.8 454 Q(application. Examples of such needs are:)100.8
467 Q 13.224(\(1\) Startup)100.8 483.6 R
(Delay: Applications may wish to a)2.75 E -.22(vo)-.22 G
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13.224(\(3\) T)100.8 529.8 R(rading of Reliability ag)-.385 E(ainst T)
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129.6 555.8 Q(TTs\) then the data will not be useful at the recei)-.66 E
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(2.1.1. The)72 150 R -.22(Po)2.75 G(st Netw).22 E
(ork Buffer and Rate Contr)-.11 E(ol)-.198 E F0
(Real time media applications typically emplo)100.8 166.6 Q 2.75(yap)
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(the media transmission are absorbed by the play out b)100.8 192.6 Q(uf)
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(will attempt to maintain a certain de)100.8 205.6 Q
(gree of occupation of the post netw)-.165 E(ork b)-.11 E(uf)-.22 E(fer)
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100.8 244.6 Q(uf)-.22 E(fer)-.275 E 5.5(.T)-.605 G
(his is an undesirable)-5.5 E(state since it implies a g)100.8 257.6 Q
(ap in the continuity of the media e)-.055 E(xperienced by the user)
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E(uf)-.22 E(fer introduce a set of requirements to rate control that)
-.275 E -.165(ex)100.8 287.2 S
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(Real time media applications may)5.5 E
(attempt to manage the occupation of the post netw)100.8 300.2 Q(ork b)
-.11 E(uf)-.22 E(fer by asking the serv)-.275 E(er to either)-.165 E(se\
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(fa)5.5 G(lls).11 E(outside of the purvie)100.8 339.2 Q 2.75(wo)-.275 G
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-2.75 E .33 -.165(ve i)-.22 H(mplications on DCCPs congestion control)
.165 E(processing.)100.8 352.2 Q(In DCCP congestion control processing \
is particular to the CCID selected by the user of a)100.8 368.8 Q(gi)
100.8 381.8 Q -.165(ve)-.275 G 2.75(nD).165 G(CCP)-2.75 E 5.5(.I)-1.221
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interact with the speci\214ed congestion control algorithms.)100.8 394.8
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(it may be appropriate for the congestion control scheme to re)100.8
407.8 Q -.055(ga)-.165 G(rd application cues in the).055 E(same w)100.8
420.8 Q(ay as it w)-.11 E(ould congestion cues from the netw)-.11 E
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(hrough the)-2.75 E(use of DCCP')100.8 433.8 Q 2.75(ss)-.605 G(lo)-2.75
E 2.75(wr)-.275 G(ecei)-2.75 E -.165(ve)-.275 G 2.75(rn).165 G
(oti\214cation.)-2.75 E 2.75([DCCP] articulates)100.8 450.4 R 2.75(as)
2.75 G(peci\214c interpretation of Slo)-2.75 E 2.75(wR)-.275 G(ecei)
-2.75 E -.165(ve)-.275 G 2.75(ro).165 G(ptions, that DCCP will not)-2.75
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-.814 G 2.75(na)-5.5 G(pplication, ho)-2.75 E(we)-.275 E -.165(ve)-.275
G .88 -.44(r, m).165 H(ay need to alter its).44 E(beha)100.8 476.4 Q
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(ay that is independent from DCCP')-.11 E(s)-.605 E(response. As such, \
it may be useful for an API to specify to the application that a Slo)
100.8 489.4 Q(w)-.275 E(Recei)100.8 502.4 Q -.165(ve)-.275 G 2.75(rs)
.165 G(ignal has been recei)-2.75 E -.165(ve)-.275 G 2.75(d. In).165 F
(this w)2.75 E(ay the application can more tightly inte)-.11 E
(grate its)-.165 E<8d6f>100.8 515.4 Q 2.75(wc)-.275 G
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-2.75 E 2.75(,a)-1.221 G -.22(vo)-2.97 G(iding).22 E(redundant w)100.8
528.4 Q(ork and unintended side ef)-.11 E
(fects of interactions between application and)-.275 E
(transport layer \215o)100.8 541.4 Q 2.75(wc)-.275 G(ontrol.)-2.75 E F1
2.75(2.1.2. Decode)72 567.4 R(Costs and Media Adaptation)2.75 E F0(TBD)
100.8 584 Q F1 2.75(2.1.3. Selecti)72 610 R .22 -.11(ve T)-.11 H
(ransmission and Retransmission)-.704 E F0
(Real time media applications ha)100.8 626.6 Q .33 -.165(ve s)-.22 H
(peci\214c deli).165 E -.165(ve)-.275 G(ry latenc).165 E 2.75(yr)-.165 G
2.75(equirements. A)-2.75 F(media pack)2.75 E(et)-.11 E(must arri)100.8
639.6 Q .33 -.165(ve a)-.275 H 2.75(tt).165 G(he the recei)-2.75 E -.165
(ve)-.275 G 2.75(rw).165 G
(ithin a certain period of time in order for the the pack)-2.75 E(et to)
-.11 E(ha)100.8 652.6 Q .33 -.165(ve r)-.22 H(ele).165 E -.275(va)-.275
G(nce in the decoded media stream.).275 E
(This requirement has an impact both on)5.5 E(transmission polic)100.8
665.6 Q 2.75(ya)-.165 G(nd on retransmission polic)-2.75 E -.715(y.)
-.165 G(DCCP')100.8 682.2 Q 2.75(su)-.605 G(nreliable data \215o)-2.75 E
(ws, which defer implementation of ARQ to the application,)-.275 E(pro)
100.8 695.2 Q(vide a clear adv)-.165 E(antage o)-.275 E -.165(ve)-.165 G
2.75(rT).165 G(CP')-2.75 E 2.75(sr)-.605 G
(equirement that all data be presented to the)-2.75 E
(application in order and without loss.)100.8 708.2 Q
(By deferring retransmission to the application, the)5.5 E(application \
can enforce retransmission policies that suit its presentation requirem\
ents.)100.8 721.2 Q(A)5.5 E 284.919(Lanphear Section)72 769 R 2.75
(2.1.3. [P)2.75 F(age 5])-.165 E EP
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(Lik)5.5 E -.275(ew)-.11 G(ise, the utility of retransmitting a gi).275
E -.165(ve)-.275 G 2.75(np).165 G(ack)-2.75 E(et as a function)-.11 E
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100.8 111 Q 2.75(yo)-.165 G(ther pack)-2.75 E(et in the)-.11 E 2.75
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(act that the frequenc)-.11 E 2.75(yo)-.165 G 2.75(fr)-2.75 G
(etransmitted)-2.75 E(pack)100.8 137 Q(ets may impact the a)-.11 E -.275
(va)-.22 G(ilable throughput for more current or rele).275 E -.275(va)
-.275 G(nt data.).275 E
(DCCP has information about the loss and transmission latenc)100.8 153.6
Q 2.75(yt)-.165 G(hat may af)-2.75 E(fect an)-.275 E(application')100.8
166.6 Q 2.75(sa)-.605 G(bility to mak)-2.75 E 2.75(ead)-.11 G
(ecision about selecti)-2.75 E .33 -.165(ve r)-.275 H
(etransmission requests.).165 E(Pro)5.5 E(viding)-.165 E
(this information to an application in an ele)100.8 179.6 Q -.055(ga)
-.165 G(nt and suf).055 E(\214ciently \215e)-.275 E(xible w)-.165 E
(ay is a challenge)-.11 E(for the API design.)100.8 192.6 Q -.165(Fo)5.5
G 2.75(rc).165 G(ertain API paradigms it may not be ef)-2.75 E
(\214cient to represent to the)-.275 E
(application layer the identity of pack)100.8 205.6 Q
(ets that are lost. In such cases informing an application)-.11 E(of wh)
100.8 218.6 Q 2.75(yp)-.055 G(ack)-2.75 E
(ets are lost and the opportunity for successful retransmission o)-.11 E
-.165(ve)-.165 G 2.75(rag).165 G -2.365 -.275(iv e)-2.75 H(n).275 E
(windo)100.8 231.6 Q 2.75(wo)-.275 G 2.75(ft)-2.75 G
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.165 G(er pack)-2.75 E(et loss data.)-.11 E(Some media applications may\
 wish to set transmission policies based on the lik)100.8 248.2 Q
(elihood that)-.11 E 2.75(ap)100.8 261.2 S(ack)-2.75 E(et will be recei)
-.11 E -.165(ve)-.275 G 2.75(do).165 G 2.75(nt)-2.75 G 2.75
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(re that the current).11 E(transmission rate is suf)100.8 274.2 Q
(\214cient for the codec to decode the media stream continuously)-.275 E
2.75(,i)-.715 G(t)-2.75 E(may not be a)100.8 287.2 Q -.11(wa)-.165 G
(re that the dynamics of the send and recei).11 E .33 -.165(ve b)-.275 H
(uf)-.055 E(fers in the DCCP are)-.275 E(inducing a latenc)100.8 300.2 Q
2.75(yt)-.165 G(hat pre)-2.75 E -.165(ve)-.275 G(nts the timely deli)
.165 E -.165(ve)-.275 G(ry of data.).165 E(This issue becomes a)5.5 E
(particular problem during the synchronization of tw)100.8 313.2 Q 2.75
(od)-.11 G(istinct streams at the client.)-2.75 E(It will)5.5 E
(therefore be useful for an application to ha)100.8 326.2 Q .33 -.165
(ve i)-.22 H(nformation about the delay induced by send).165 E
(and recei)100.8 339.2 Q .33 -.165(ve b)-.275 H(uf)-.055 E(fers.)-.275 E
(Presentation of delay information from DCCP to the application should \
be achie)100.8 355.8 Q -.165(ve)-.275 G(d).165 E
(through a representation of a compound of tw)100.8 368.8 Q 2.75(om)-.11
G(etrics, the estimated R)-2.75 E(TT and the)-.66 E(estimated b)100.8
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(TT is not necessarily representati)-.66 E .33 -.165(ve o)-.275 H 2.75
(ft).165 G(he)-2.75 E(forw)100.8 394.8 Q(ard propag)-.11 E(ation delay)
-.055 E 2.75(,i)-.715 G 2.75(td)-2.75 G(oes pro)-2.75 E
(vide an indication of the e)-.165 E(xtent of delay induced by)-.165 E
(the netw)100.8 407.8 Q 2.75(ork. The)-.11 F(number of b)2.75 E(uf)-.22
E(fers in the send queue may also be used by the application)-.275 E(to\
 determine the amount of delay the sending DCCP may add to the propag)
100.8 420.8 Q(ation of the)-.055 E(transmission of a gi)100.8 433.8 Q
-.165(ve)-.275 G 2.75(nd).165 G 2.75(atagram. Pro)-2.75 F
(viding such metrics to the application is a matter of)-.165 E
(maintaining these metrics, and pro)100.8 446.8 Q
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2.75(2.1.4. Latency)72 472.8 R(Requir)2.75 E(ements)-.198 E F0 -.44(Wi)
100.8 489.4 S(thin the domain of real time media applications e).44 E
(xists a subset of broadcast applications)-.165 E(which ha)100.8 502.4 Q
.33 -.165(ve a v)-.22 H(arying latenc)-.11 E 2.75(yr)-.165 G 2.75
(equirements. In)-2.75 F(instances, it may be permissible to ha)2.75 E
-.165(ve)-.22 G(arbitrary latenc)100.8 515.4 Q 2.75(yb)-.165 G(etween t\
he real time encoding source and the recipients of that source.)-2.75 E
(Such cases instances include broadcast media scenarios in which there \
is no reference point)100.8 528.4 Q(ag)100.8 541.4 Q
(ainst which to ascertain the e)-.055 E(xtent to which the recei)-.165 E
-.165(ve)-.275 G 2.75(dm).165 G(edia is synchronized with w)-2.75 E(all)
-.11 E(clock time.)100.8 554.4 Q(Lik)5.5 E -.275(ew)-.11 G
(ise, there are instances in which such synchronization is absolutely)
.275 E(essential to the success of the application.)100.8 567.4 Q -.165
(Fo)5.5 G 2.75(re).165 G(xample, broadcast sessions that are used)-2.915
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g should be done in such as)100.8 610 Q -.11(wa)100.8 623 S 2.75(ya).11
G 2.75(st)-2.75 G 2.75(oa)-2.75 G -.11(lwa)-2.75 G(ys minimize propag)
.11 E(ation delay)-.055 E 5.5(.T)-.715 G(he application should be pro)
-5.5 E(vided with a)-.165 E(mechanism to inform an)100.8 636 Q 2.75(yt)
-.165 G(rade of)-2.75 E(fs between propag)-.275 E
(ation delay and DCCP functionality)-.055 E(.)-.715 E(DCCP feature ne)
100.8 649 Q(gotiation, for e)-.165 E
(xample, may cost a delay in the stream while a gi)-.165 E -.165(ve)
-.275 G(n).165 E(feature is agreed upon.)100.8 662 Q
(An implementation of DCCP may w)5.5 E(ant to allo)-.11 E 2.75(wt)-.275
G(he application to)-2.75 E(con\214gure def)100.8 675 Q
(ault responses that can foreshorten feature ne)-.11 E
(gotiation requests.)-.165 E(This will)5.5 E(allo)100.8 688 Q 2.75(wm)
-.275 G(itig)-2.75 E(ation of e)-.055 E -.165(ve)-.275 G
(nts that may otherwise stall the session until feature ne).165 E
(gotiation)-.165 E(completes.)100.8 701 Q 284.919(Lanphear Section)72
769 R 2.75(2.1.4. [P)2.75 F(age 6])-.165 E EP
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2.75(,f)-.715 G(or e)-2.75 E(xample, allo)-.165 E 2.75(wt)-.275 G
(he application to specify preferences for)-2.75 E(ne)100.8 98 Q
(gotiable features prior to the initiation of the session.)-.165 E
(This will allo)5.5 E 2.75(wD)-.275 G(CCP to perform)-2.75 E(feature ne)
100.8 111 Q(gotiation as per application preferences without e)-.165 E
(xplicit interaction with the)-.165 E 2.75(application. The)100.8 124 R
(same API may also accommodate the case where the application needs a)
2.75 E(more dynamic presence in the DCCP feature ne)100.8 137 Q
(gotiation process.)-.165 E/F1 11/Times-Bold@0 SF 2.75(2.1.5. R)72 163 R
(TP/R)-.44 E(TCP)-.44 E F0(TBD)100.8 179.6 Q F1 2.75(2.1.6. IP)72 205.6
R -1.012(Te)2.75 G(lephony)1.012 E F0(TBD)100.8 222.2 Q F1 2.75
(2.1.7. V)72 248.2 R(ideo T)-.407 E(eleconfer)-1.012 E(encing)-.198 E F0
(TBD)100.8 264.8 Q F1 2.75(2.1.8. Multi-Play)72 290.8 R(er Game A)-.11 E
(pplications)-.275 E F0(TBD)100.8 307.4 Q F1(2.2.)72 333.4 Q/F2 13
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2.75(2.2.1. Loss)72 359.4 R(Signaling)2.75 E F0(Although DCCP does pro)
100.8 376 Q(vide unreliable deli)-.165 E -.165(ve)-.275 G
(ry of data, it does ha).165 E .33 -.165(ve a n)-.22 H(otion of which)
.165 E(datagrams where dropped, and a limited notion of wh)100.8 389 Q
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Q 2.75(eo)-.11 G(ther adapti)-2.75 E .33 -.165(ve m)-.275 H(easures.)
.165 E(The pro)100.8 415 Q(vision of such information to the applicatio\
n may blur the separation of)-.165 E
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(implementation that pro)100.8 441 Q(vides e)-.165 E
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(may be both inef)100.8 454 Q
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(2.2.2. Dr)72 480 R(op Pr)-.198 E(efer)-.198 E(ence)-.198 E F0
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E -.165(ve)-.275 G(ry of pack).165 E(ets.)-.11 E(Unreliable deli)100.8
509.6 Q -.165(ve)-.275 G(ry allo).165 E
(ws an application to enforce retransmission policies, for e)-.275 E
(xample,)-.165 E(since not all pack)100.8 522.6 Q(ets need to be re)-.11
E -.055(ga)-.165 G(rded with equal rele).055 E -.275(va)-.275 G
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(.T)-1.221 G(his)-5.5 E(paradigm can be e)100.8 535.6 Q
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(ets when resources)-.11 E(become scarce.)100.8 548.6 Q(In the e)100.8
565.2 Q -.165(ve)-.275 G(nt that DCCP must drop a pack).165 E
(et due to b)-.11 E(uf)-.22 E(fer o)-.275 E -.165(ve)-.165 G(r\215o).165
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(as to which pack)100.8 578.2 Q(et to drop.)-.11 E
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(place preference on ne)100.8 591.2 Q 2.75(wd)-.275 G(ata v)-2.75 E
(ersus old data within a gi)-.165 E -.165(ve)-.275 G 2.75(nq).165 G 2.75
(ueue. As)-2.75 F(such, a DCCP)2.75 E(implementation may w)100.8 604.2 Q
(ant to pro)-.11 E
(vide the application with the ability to specify a drop)-.165 E
(semantic to follo)100.8 617.2 Q -.715(w.)-.275 G F1 2.75
(2.2.3. Mobility)72 643.2 R F0(Mobile capability in DCCP presents a set\
 of problems to applications that transmit a)100.8 659.8 Q
(continuous stream of data.)100.8 672.8 Q
(Such applications include a certain subset of real time media)5.5 E
(applications and g)100.8 685.8 Q(aming applications.)-.055 E(In the e)
5.5 E -.165(ve)-.275 G(nt that a mobile enabled DCCP initiates a).165 E
(mo)100.8 698.8 Q -.165(ve)-.165 G 2.75(,t).165 G
(he transmission of data must stop until the mo)-2.75 E .33 -.165(ve c)
-.165 H(ompletes successfully).165 E 5.5(.T)-.715 G(he API)-5.5 E
(semantics of handling this e)100.8 711.8 Q -.165(ve)-.275 G
(nt may be as simple as responding to write requests with a).165 E -.11
(fa)100.8 724.8 S(ilure code indicating that a mo).11 E .33 -.165(ve e)
-.165 H -.165(ve)-.11 G(nt is occurring.).165 E(It is critical, ho)5.5 E
(we)-.275 E -.165(ve)-.275 G .88 -.44(r, t).165 H(hat the).44 E 284.919
(Lanphear Section)72 769 R 2.75(2.2.3. [P)2.75 F(age 7])-.165 E EP
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(April 2003)2.75 E(October 2002)112.127 E(application be af)100.8 85 Q
(forded an opportunity to mak)-.275 E 2.75(ea)-.11 G 2.75(na)-2.75 G
(dapti)-2.75 E .33 -.165(ve d)-.275 H(ecision in the presence of g).165
E(aps)-.055 E(in service induced by a mo)100.8 98 Q .33 -.165(ve e)-.165
H -.165(ve)-.11 G(nt.).165 E(DCCP speci\214es that a recei)100.8 114.6 Q
(ving DCCP HC may drop all data from a the old IP address/port)-.275 E
(pair in response to a successful mo)100.8 127.6 Q .33 -.165(ve e)-.165
H -.165(ve)-.11 G(nt, or follo).165 E 2.75(wa)-.275 G 2.75(na)-2.75 G
(lternate route of accepting a loss)-2.75 E(windo)100.8 140.6 Q(w')-.275
E 2.75(sw)-.605 G(orth of data.)-2.86 E(The semantics chosen for this e)
5.5 E -.165(ve)-.275 G(nt should be con\214gurable by the).165 E
(application.)100.8 153.6 Q(Since session attrib)100.8 170.2 Q
(utes may ha)-.22 E .33 -.165(ve c)-.22 H(hanged as a result of a Mo)
.165 E .33 -.165(ve e)-.165 H -.165(ve)-.11 G(nt, it may be useful to)
.165 E(inform the application of the successful completion of a mo)100.8
183.2 Q .33 -.165(ve e)-.165 H -.165(ve)-.11 G(nt so it can reset state)
.165 E(contingent upon such attrib)100.8 196.2 Q 2.75(utes. P)-.22 F
(ath MTU is an e)-.165 E(xample of such an attrib)-.165 E(ute that af)
-.22 E(fects)-.275 E(application beha)100.8 209.2 Q(vior)-.22 E 2.75(,a)
-.44 G(nd is susceptible to change as a result of a Mo)-2.75 E .33 -.165
(ve e)-.165 H -.165(ve)-.11 G(nt.).165 E/F1 11/Times-Bold@0 SF 2.75
(2.2.4. Send)72 235.2 R(Option on Option Change W)2.75 E(ith or W)-.198
E(ithout Data)-.198 E F0
([DCCP] indicates that options may be sent either with or without data.)
100.8 251.8 Q(Sending options)5.5 E
(with data may require that the DCCP w)100.8 264.8 Q
(ait to send the option until the application has more)-.11 E
(data to send.)100.8 277.8 Q(This may not be a desired beha)5.5 E
(vior for an application.)-.22 E(Lik)5.5 E -.275(ew)-.11 G(ise and).275
E(application may w)100.8 290.8 Q
(ant to piggyback options onto data for purposes of ef)-.11 E(\214cienc)
-.275 E 1.43 -.715(y. D)-.165 H(CCP).715 E(applications may be af)100.8
303.8 Q(forded the opportunity to inform DCCP that an option change)
-.275 E(request should be sent immediately rather than after some amoun\
t of data has been written)100.8 316.8 Q(to the DCCP)100.8 329.8 Q 5.5
(.T)-1.221 G(his can be achie)-5.5 E -.165(ve)-.275 G 2.75(dt).165 G
(hrough a \215ag sent with the options change request.)-2.75 E F1 2.75
(2.2.5. Pr)72 355.8 R(otocol Inf)-.198 E(ormation Shar)-.275 E
(ed with Ov)-.198 E(erlying Lay)-.11 E(ers)-.11 E F0
(Application layer framing protocols, such a R)100.8 372.4 Q(TP)-.66 E
2.75(,m)-1.221 G(ay represent session information that is)-2.75 E
(redundant with that used by DCCP)100.8 385.4 Q 2.75(.E)-1.221 G
(xamples of such data include sequence numbering)-2.75 E(and latenc)
100.8 398.4 Q 2.75(yc)-.165 G
(alculations. A DCCP implementation may pro)-2.75 E(vide a w)-.165 E
(ay to share information)-.11 E(with the o)100.8 411.4 Q -.165(ve)-.165
G(rlying protocol in an ef).165 E(fort to minimize redundanc)-.275 E
-.715(y.)-.165 G(Such a model, ho)100.8 428 Q(we)-.275 E -.165(ve)-.275
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(ay neither be feasible nor appropriate for certain e).44 E(xisting k)
-.165 E(ernel)-.11 E(API paradigms such as BSD sock)100.8 441 Q 2.75
(ets. In)-.11 F 2.75(ac)2.75 G(lean design, DCCP need not ha)-2.75 E .33
-.165(ve k)-.22 H(no).165 E(wledge of)-.275 E
(the header information added by the o)100.8 454 Q -.165(ve)-.165 G
(rlying protocol.).165 E 2.75(At)5.5 G(rade of)-2.75 E 2.75(fm)-.275 G
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(PI with added comple)-2.75 E(xity)-.165 E 2.75(,a)-.715 G(nd)-2.75 E
(coping with the o)100.8 480 Q -.165(ve)-.165 G
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(API and Con\214guration Considerations)5.5 E F0(DCCP semantics and fun\
ctionality must be rendered meaningfully to the application layer)100.8
539.2 Q(through an API.)100.8 552.2 Q
(This section collects the semantical issues of DCCP that ha)5.5 E .33
-.165(ve a)-.22 H 2.75(ni).165 G(mpact)-2.75 E(on an API to DCCP)100.8
565.2 Q(.)-1.221 E F1(3.1.)72 591.2 Q/F3 13/Times-Bold@0 SF
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(ariability of DCCP')-.275 E 2.75(ss)-.605 G(emantics. Those)-2.75 E
(areas in which DCCP')100.8 620.8 Q 2.75(ss)-.605 G(emantics may v)-2.75
E(ary as per the needs of the application are)-.275 E
(represented here as a collection of con\214guration v)100.8 633.8 Q
(ariables which an API designer may tak)-.275 E(e)-.11 E
(into account when e)100.8 646.8 Q(xposing DCCP')-.165 E 2.75(sf)-.605 G
(unctionality)-2.75 E(.)-.715 E(Con\214gurable v)100.8 663.4 Q
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(ate)-2.75 E 2.75(gories. Either)-.165 F(con\214gurable)2.75 E -.275(va)
100.8 676.4 S(riable may be for an option pro).275 E
(vided in [DCCP] , or an option may be e)-.165 E(xposed pro)-.165 E
(vided)-.165 E(by the semantics of a particular implementation.)100.8
689.4 Q 293.169(Lanphear Section)72 769 R 2.75(3.1. [P)2.75 F(age 8])
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Q(xt and precise meaning of the con\214gurable options is found in [DCC\
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E(ault con\214guration, in others no def)-.11 E(ault is)-.11 E 2.75
(speci\214ed. Those)100.8 127.6 R(options with a speci\214ed def)2.75 E
(ault are indicated with a *. Otherwise the)-.11 E(def)100.8 140.6 Q
(ault v)-.11 E(alue indicated is a suggested v)-.275 E(alue.)-.275 E
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306.2 Q 52.25(ectors 0)-1.221 F(*)2.75 E(Service Name)136.8 319.2 Q(n/a)
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5.5 E(xpose these options)-.165 E(in cases where an implementation w)
100.8 393.8 Q(ants to allo)-.11 E 2.75(wd)-.275 G(ef)-2.75 E
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(eatur)-.275 E 2.75(eN)-.198 G(egotiation Limit)-2.75 E F0
(Section 5.3 of [DCCP] discusses Feature Ne)100.8 449.4 Q
(gotiation. It is possible for DCCP')-.165 E 2.75(sF)-.605 G(eature)
-2.75 E(Ne)100.8 462.4 Q(gotiation to enter an ambiguous state if a gi)
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(gotiate for a)-.165 E
(speci\214c option which the remote end point does not prefer)100.8
475.4 Q 5.5(.I)-.605 G 2.75(nt)-5.5 G(his case, it may be useful)-2.75 E
(for the application to specify the number of f)100.8 488.4 Q
(ailed change requests before the connection is)-.11 E 2.75
(aborted. The)100.8 501.4 R(def)2.75 E(ault v)-.11 E(alue should be 3.)
-.275 E F1 2.75(3.1.2.2. Pr)72 527.4 R(eferr)-.198 E(ed F)-.198 E(eatur)
-.275 E 2.75(eP)-.198 G(riorities, Exclusions and Inclusions)-2.75 E F0
(An application may w)100.8 544 Q
(ant to specify a set of preferred options with which to ne)-.11 E
(gotiate)-.165 E(ag)100.8 557 Q(ainst a remote end point.)-.055 E
(The utility of doing so is to allo)5.5 E 2.75(waD)-.275 G
(CCP to try a number of)-2.75 E
(application speci\214ed options before f)100.8 570 Q
(ailing a connection, or feature change attempt.)-.11 E(This)5.5 E
(semantics mitig)100.8 583 Q(ates the cost of forcing DCCP to ne)-.055 E
(gotiate through the application layer for)-.165 E(each f)100.8 596 Q
(ailed option change.)-.11 E(An implementation of DCCP may also pro)
100.8 612.6 Q(vide the application with the ability to indicate)-.165 E
(certain features that it prefers to use or nor to use.)100.8 625.6 Q
(The inclusion or e)5.5 E(xclusion of ne)-.165 E(gotiable)-.165 E
(features for a DCCP allo)100.8 638.6 Q 2.75(wt)-.275 G
(hat DCCP to indicate application preferences during feature)-2.75 E(ne)
100.8 651.6 Q(gotiation)-.165 E F1 2.75(3.1.2.3. Loss)72 677.6 R -.198
(Wi)2.75 G(ndo).198 E 2.75(wR)-.11 G(atio)-2.75 E F0(The Loss W)100.8
694.2 Q(indo)-.44 E 2.75(wf)-.275 G
(eature, described in section 5.9 of [DCCP])-2.75 E 2.75(,d)5.5 G
(etermines the windo)-2.75 E(w)-.275 E -.165(ove)100.8 707.2 S 2.75(rw)
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-.165(ve)-.275 G 2.75(dd).165 G(atagrams as v)-2.75 E 2.75(alid. Since)
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(round the most recent sequence number seen, this v)-2.75 E(ariable)
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-2.75 E(ws the underlying DCCP to send)-.275 E(Slo)100.8 300.2 Q 2.75
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(pack)100.8 355.8 Q(ets are being dropped at the remote end point, and \
therefore stop sending data to the)-.11 E
(underlying DCCP for transmission. The def)100.8 368.8 Q(ault v)-.11 E
(alue for this option 1.)-.275 E F1 2.75(3.1.2.7. Dr)72 394.8 R(op Pr)
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(An application may wish to specify the w)100.8 411.4 Q
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100.8 424.4 S 2.75(re).165 G(xample, certain real time applications ha)
-2.915 E .33 -.165(ve a p)-.22 H(reference for the most recent data o)
.165 E -.165(ve)-.165 G(r).165 E(the oldest data in the queue.)100.8
437.4 Q(This option may be articulated as a boolean which indicates)5.5
E(that the DCCP should drop-head \(1\) or drop-tail \(0\).)100.8 450.4 Q
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(Section 9.4 of [DCCP])100.8 493 Q
(discusses indicates that a DCCP recei)5.5 E -.165(ve)-.275 G 2.75(rm)
.165 G(ay drop all data)-2.75 E(recei)100.8 506 Q -.165(ve)-.275 G 2.75
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-.165 H(as completed successfully).165 E 2.75(,o)-.715 G 2.75(ri)-2.75 G
2.75(tm)-2.75 G(ay)-2.75 E(accept one Loss W)100.8 519 Q(indo)-.44 E(w')
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(This option lets the application determine the)5.5 E(beha)100.8 532 Q
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100.8 545 Q -.165(ve)-.165 G 2.75(,a).165 G(nd a v)-2.75 E
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(vice Name)-.11 E F0
(The Service Name is discussed in section 4.5 of [DCCP].)100.8 600.6 Q
(If this option is set to 1 then)5.5 E(DCCP must force e)100.8 613.6 Q
-.165(ve)-.275 G(ry sock).165 E(et to specify a Service Name. The def)
-.11 E(ault v)-.11 E(alue should be 1.)-.275 E F1 2.75
(3.1.2.10. Minimal)72 639.6 R(Buffering Option)2.75 E F0
(An implementation may wish to allo)100.8 656.2 Q 2.75(wa)-.275 G
(pplications to specify the amount of b)-2.75 E(uf)-.22 E(fering that)
-.275 E(the DCCP will do on the sender side.)100.8 669.2 Q(So, for e)5.5
E(xample, a sending DCCP may support a)-.165 E
(semantic such that the DCCP does not mak)100.8 682.2 Q 2.75(ei)-.11 G
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101.6 Q(xceed the sizes of the)-.165 E(pending datagrams, then those da\
tagrams may either be dropped or transmitted with the DF)100.8 114.6 Q
(bit cleared.)100.8 127.6 Q(This beha)5.5 E
(vior should be con\214gurable by the application.)-.22 E F1(3.2.)72
153.6 Q/F2 13/Times-Bold@0 SF(Connection Establishment and T)5.5 E
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2.75 E F0(Due to Feature Ne)100.8 196.2 Q
(gotiation, it is typical that a DCCP connection attempt will not be)
-.165 E(completed immediately)100.8 209.2 Q 5.5(.A)-.715 G 2.75(nA)-5.5
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(determine if a connection attempt is in progress, has f)100.8 235.2 Q
(ailed, or has completed.)-.11 E F1 2.75(3.2.2. Data)72 261.2 R
(Piggybacking)2.75 E F0
([DCCP] permits data piggybacking onto connection requests.)100.8 277.8
Q(An API need not support)5.5 E 2.75(this. An)100.8 290.8 R
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(vide queuing of transmitted data in the)-.165 E
(DCCP prior to connection establishment to mitig)100.8 303.8 Q
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(connection realization and the initiation of data \215o)100.8 316.8 Q
1.43 -.715(w. I)-.275 H(mplementation of data piggybacking).715 E
(on a connection request may ha)100.8 329.8 Q .33 -.165(ve a)-.22 H 2.75
(ni).165 G(mpact on the non-blocking interf)-2.75 E(ace semantics of a)
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(CCP must close both of its half connections as a pair)-2.75 E 5.5(.I)
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(ve)-.275 G 2.75(sn).165 G(oti\214cation of a recei)-2.75 E .33 -.165
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(re that the recei).11 E(ving half connection can no)-.275 E
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-.165 G(rded as a terminal state for that half connection prior).055 E
(to closing the full DCCP connection.)100.8 535.6 Q
(That is, the half connection may not return from a)5.5 E -.22(bu)100.8
548.6 S -.275(ff).22 G(er closed state to a state in which it can recei)
.275 E .33 -.165(ve m)-.275 H(ore data without opening a ne).165 E(w)
-.275 E(DCCP session.)100.8 561.6 Q F1(3.3.)72 587.6 Q F2 -.325(Fe)5.5 G
(atur).325 E 3.25(eN)-.234 G(egotiation)-3.25 E F1 2.75
(3.3.1. Negotiable)72 613.6 R -.275(Fe)2.75 G(atur).275 E(es)-.198 E F0
(The follo)100.8 630.2 Q(wing features require ne)-.275 E
(gotiation with the remote DCCP:)-.165 E 7.15<8343>100.8 650.4 S
(ongestion Control \(CC\))-7.15 E 7.15<8345>100.8 667 S(CN Capable)-7.15
E 7.15<8355>100.8 683.6 S(se Ack V)-7.15 E(ector)-1.221 E 7.15<834d>
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(he cases in which an options change request may be handled)-5.5 E
(immediately are:)100.8 166.6 Q 13.224(\(1\) The)100.8 183.2 R
(DCCP is not in connected, and therefore will not ne)2.75 E
(gotiate a feature change)-.165 E(until a connection is initiated.)129.6
196.2 Q 13.224(\(2\) The)100.8 212.8 R(requested feature is non ne)2.75
E(gotiable.)-.165 E(An implementation may chose to pro)100.8 229.4 Q
(vide non-blocking semantics that parallel the)-.165 E(semantics for a \
connect attempt. A request to perform an operation on a DCCP that is in\
 an)100.8 242.4 Q(unkno)100.8 255.4 Q
(wn state due to a pending feature ne)-.275 E
(gotiation may result in the return of an error code)-.165 E
(that indicates a feature change is in progress. The API may then pro)
100.8 268.4 Q(vide a mechanism for)-.165 E(asynchronous noti\214cation \
or polling of the status of the pending or completed feature)100.8 281.4
Q(change.)100.8 294.4 Q F1 2.75(3.3.3. F)72 320.4 R(eatur)-.275 E 2.75
(eo)-.198 G(ptions with data)-2.75 E F0(DCCP does allo)100.8 337 Q 2.75
(wo)-.275 G(ption change requests to contain application data that is s\
cheduled to be)-2.75 E 2.75(transmitted. An)100.8 350 R
(implementation of DCCP may present a feature change mode where the)2.75
E(feature change does not be)100.8 363 Q
(gin until there is user data to transmit along with the feature)-.165 E
(change request.)100.8 376 Q(The ca)5.5 E -.165(ve)-.22 G
(at for such a feature is that feature changes may suf).165 E(fer from)
-.275 E(undue latenc)100.8 389 Q 2.75(yi)-.165 G 2.75(ft)-2.75 G
(he time between application write requests is long.)-2.75 E F1 2.75
(3.3.4. Impact)72 415 R(of featur)2.75 E 2.75(en)-.198 G
(egotiation on I/O semantics)-2.75 E F0
(The report of the success of a feature ne)100.8 431.6 Q
(gotiation may depend on more than just the)-.165 E
(acceptable completion of the ne)100.8 444.6 Q(gotiation e)-.165 E 2.75
(xchange. Outstanding)-.165 F(data in the DCCP may)2.75 E
(need to be processed under the pre)100.8 457.6 Q
(vious feature parameters before ne)-.275 E 2.75(wd)-.275 G(ata may be)
-2.75 E
(accepted from the application. This semantic is particularly rele)100.8
470.6 Q -.275(va)-.275 G(nt for CCID changes, in).275 E(which the appli\
cation may reasonably assume that all data sent prior to a CCID change \
will)100.8 483.6 Q(be sent according to the prior CCID.)100.8 496.6 Q
(This issue will ultimately the determine the timing of)5.5 E
(reporting the completion of a feature ne)100.8 509.6 Q
(gotiation to the application.)-.165 E F1(3.4.)72 535.6 Q/F2 13
/Times-Bold@0 SF(Err)5.5 E(or Codes)-.234 E F0
(An API to DCCP may wish to e)100.8 552.2 Q
(xpose error codes that represent the follo)-.165 E(wing conditions:)
-.275 E(Connection In Progress)100.8 568.8 Q 7.15<8346>100.8 585.4 S
(eature Change In Progress)-7.15 E 7.15<8346>100.8 602 S
(eature Change T)-7.15 E(imed Out)-.385 E 7.15<8346>100.8 618.6 S
(eature Change f)-7.15 E(ailed due to lack of agreement)-.11 E 7.15
<8352>100.8 635.2 S(emote Buf)-7.15 E(fer Closed)-.275 E 7.15<8352>100.8
651.8 S(ecei)-7.15 E .33 -.165(ve B)-.275 H(uf).165 E(fer Empty)-.275 E
7.15<834d>100.8 668.4 S(obile Location Change F)-7.15 E(ailed)-.165 E
7.15<8343>100.8 685 S(onnection Proof F)-7.15 E(ailed)-.165 E 7.15<8344>
100.8 701.6 S(atagram T)-7.15 E(oo Lar)-.88 E(ge for MTU)-.198 E 287.669
(Lanphear Section)72 769 R 2.75(3.4. [P)2.75 F(age 12])-.165 E EP
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2.75(AD)100.8 127.6 S(CCP implementation may maintain the follo)-2.75 E
(wing statistics for e)-.275 E(xposure for use by the)-.165 E
(application:)100.8 140.6 Q 7.15<8350>100.8 160.8 S(MTU)-7.15 E 7.15
<8345>100.8 177.4 S(stimated R)-7.15 E(TT)-.66 E 7.15<8345>100.8 194 S
(stimated Buf)-7.15 E(fer Depth)-.275 E 7.15<8345>100.8 210.6 S
(stimated inter arri)-7.15 E -.275(va)-.275 G 2.75(lt).275 G
(ime of datagrams)-2.75 E 7.15<8345>100.8 227.2 S(stimated inter retrie)
-7.15 E -.275(va)-.275 G 2.75(lt).275 G(ime of datagrams)-2.75 E 7.15
<8345>100.8 243.8 S(stimated loss metric)-7.15 E 7.15<8345>100.8 260.4 S
(stimated congestion controlled data rate)-7.15 E 7.15<834f>100.8 277 S
(utstanding un-Ack)-7.15 E(ed data)-.11 E F1(4.)72 303 Q/F3 14
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(DCCP implementations will confront a number of common design choices.)
100.8 319.6 Q(This section)5.5 E(identi\214es and outlines those choice\
s along with possible solution paths.)100.8 332.6 Q F1(4.1.)72 358.6 Q
F2(Connection State)5.5 E F0(DCCP pro)100.8 375.2 Q
(vides a mechanism to support common connection semantics, while relie)
-.165 E(ving the)-.275 E(serv)100.8 388.2 Q(er of the need to k)-.165 E
(eep state.)-.11 E(This is achie)5.5 E -.165(ve)-.275 G 2.75(dt).165 G
(hrough an Init Cookie, which the serv)-2.75 E(er)-.165 E(uses to encap\
sulate the original connection request, along with its response.)100.8
401.2 Q(The echo of)5.5 E(this data upon completion of the three w)100.8
414.2 Q(ay hand shak)-.11 E 2.75(ea)-.11 G(llo)-2.75 E(ws the serv)-.275
E(er to establish the)-.165 E(connection with the correct parameters wi\
thout holding state throughout the processing of)100.8 427.2 Q
(the connection.)100.8 440.2 Q(If the serv)100.8 456.8 Q(er wishes to a)
-.165 E -.22(vo)-.22 G
(id holding state during connection processing, then it also must).22 E
(be able to reject data payloads piggyback)100.8 469.8 Q
(ed with a DCCP-Request pack)-.11 E(et. Otherwise the)-.11 E(serv)100.8
482.8 Q(er w)-.165 E(ould ha)-.11 E .33 -.165(ve t)-.22 H 2.75(oa).165 G
(llocate the requisite structures to manage the pending user data until)
-2.75 E(the connection is established. These semantics lea)100.8 495.8 Q
.33 -.165(ve o)-.22 H(pen the issues of the w).165 E(ay in which)-.11 E
(the Init Cookie ought to be implemented, and the w)100.8 508.8 Q
(ay in which a client copes with a data)-.11 E(discard e)100.8 521.8 Q
-.165(ve)-.275 G(nt.).165 E(DCCPs which allo)100.8 538.4 Q 2.75(wt)-.275
G(he application to piggyback data on to connection requests may ha)
-2.75 E -.165(ve)-.22 G(to handle cases where the serv)100.8 551.4 Q
(er discards the piggyback)-.165 E(ed data because it does not w)-.11 E
(ant to)-.11 E(hold state.)100.8 564.4 Q(This scenario may be quite com\
mon, since the stateless connection feature of)5.5 E
(DCCP may be widely implemented and used by applications.)100.8 577.4 Q
(DCCPs may support the)5.5 E(retransmission of data piggyback)100.8
590.4 Q(ed on a DCCP-Request pack)-.11 E(et in a subsequent DCCP-)-.11 E
(Data pack)100.8 603.4 Q(et once the connection is established.)-.11 E
(The concept of such retransmission,)5.5 E(ho)100.8 616.4 Q(we)-.275 E
-.165(ve)-.275 G .88 -.44(r, i).165 H 2.75(sc).44 G
(ontrary to DCCPs design as an unreliable protocol.)-2.75 E 2.75(Am)5.5
G(ore appropriate)-2.75 E(implementation may pro)100.8 629.4 Q(vide a w)
-.165 E(ay to notify the application that a retransmit is required.)-.11
E F1(4.2.)72 655.4 Q F2(Pr)5.5 E -.13(ov)-.234 G
(ision of sequence number).13 E 3.25(,a)-1.196 G
(nd loss data to application)-3.25 E F0(DCCP')100.8 672 Q 2.75(sm)-.605
G(aintenance of a sequence number space and a)-2.75 E -.11(wa)-.165 G
(reness of lost data may lea).11 E -.165(ve)-.22 G
(room for optimizations with protocols that operate at layers abo)100.8
685 Q .33 -.165(ve D)-.165 H(CCP).165 E 5.5(.C)-1.221 G(ertain)-5.5 E
(application layer protocols, for e)100.8 698 Q
(xample, may require an a)-.165 E -.11(wa)-.165 G
(reness of lost data that is).11 E
(congruent with that maintained by DCCP and may desire to share DCCP')
100.8 711 Q 2.75(sr)-.605 G(epresentation)-2.75 E(of this information.)
100.8 724 Q 287.669(Lanphear Section)72 769 R 2.75(4.2. [P)2.75 F
(age 13])-.165 E EP
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(April 2003)2.75 E(October 2002)112.127 E(There are, ho)100.8 85 Q(we)
-.275 E -.165(ve)-.275 G .88 -.44(r, c).165 H
(oncerns with this approach.).44 E -.165(Fa)5.5 G(ilure to observ).165 E
2.75(et)-.165 G(he layering of)-2.75 E
(protocols may introduce semantical comple)100.8 98 Q
(xities to the API that could otherwise be)-.165 E -.22(avo)100.8 111 S
(ided. Gi).22 E -.165(ve)-.275 G 2.75(nt).165 G
(hat most DCCP implementations will be in k)-2.75 E
(ernel space, the frequenc)-.11 E(y)-.165 E(with which loss data or seq\
uence number representation must be communicated across the)100.8 124 Q
-.11(ke)100.8 137 S
(rnel/user boundary becomes a reasonable consideration for scalability)
.11 E 5.5(.T)-.715 G(he trade of)-5.5 E 2.75(ff)-.275 G(or)-2.75 E(the \
elimination of redundant maintenance of sequence numbers is therefore n\
ot necessarily)100.8 150 Q 2.75(useful. Application)100.8 163 R
(layer implementations of DCCP may)2.75 E 2.75(,h)-.715 G -.275(ow)-2.75
G -2.365 -.275(ev e).275 H .88 -.44(r, \214).275 H
(nd an approach to the).44 E
(sharing of sequence information to be viable.)100.8 176 Q/F1 11
/Times-Bold@0 SF(4.3.)72 202 Q/F2 13/Times-Bold@0 SF(Pr)5.5 E
(obabilistic V)-.234 E(eri\214cation of Loss Rate using ECN f)-1.3 E
(or TFRC)-.325 E F0(TBD)100.8 218.6 Q F1(4.4.)72 244.6 Q F2
(Supporting A)5.5 E(pplication F)-.325 E(eatur)-.325 E 3.25(eP)-.234 G
-.234(re)-3.25 G(fer).234 E(ence)-.234 E F0 2.75(Af)100.8 261.2 S
(ull featured DCCP implementation may pro)-2.75 E(vide a set of ne)-.165
E(gotiable features to the)-.165 E
(remote DCCP that the application may not wish to present.)100.8 274.2 Q
(In such cases it will be useful)5.5 E(for an DCCP implementation to ma\
intain a table of features permitted by the application as)100.8 287.2 Q
(per the application')100.8 300.2 Q 2.75(sc)-.605 G
(on\214guration input.)-2.75 E
(This table should then be consulted in response)5.5 E(to DCCP feature \
change requests when a feature preference must be indicated.)100.8 313.2
Q F1(4.5.)72 339.2 Q F2(Slo)5.5 E 3.25(wR)-.13 G(ecei)-3.25 E -.13(ve)
-.13 G 3.25(rI).13 G(nter)-3.25 E(pr)-.13 E(etation and Noti\214cation)
-.234 E F0 2.75(AD)100.8 355.8 S(CCP recei)-2.75 E -.165(ve)-.275 G 2.75
(rm).165 G(ay notify its sender that the o)-2.75 E -.165(ve)-.165 G
(rlying application k).165 E(eeping up with the)-.11 E
(inbound data rate.)100.8 368.8 Q(In order to relie)5.5 E .33 -.165
(ve t)-.275 H(he application of ha).165 E(ving to e)-.22 E
(xplicitly specify Slo)-.165 E(w)-.275 E(Recei)100.8 381.8 Q -.165(ve)
-.275 G 2.75(rt).165 G 2.75(oD)-2.75 G(CCP)-2.75 E 2.75(,a)-1.221 G 2.75
(ni)-2.75 G(mplementation may pro)-2.75 E
(vide a heuristic to determine when to send)-.165 E(Slo)100.8 394.8 Q
2.75(wR)-.275 G(ecei)-2.75 E -.165(ve)-.275 G 2.75(ri).165 G(tself.)
-2.75 E 2.75(As)100.8 411.4 S(imple heuristic w)-2.75 E(ould in)-.11 E
-.22(vo)-.44 G(lv).22 E 2.75(es)-.165 G(ending Slo)-2.75 E 2.75(wR)-.275
G(ecei)-2.75 E -.165(ve)-.275 G 2.75(ro).165 G(nce the DCCP')-2.75 E
2.75(sr)-.605 G(ecei)-2.75 E .33 -.165(ve b)-.275 H(uf)-.055 E(fer is)
-.275 E(within some speci\214ed number of bytes of being full.)100.8
424.4 Q(The problem with this approach is)5.5 E
(that such a condition could represent a steady state beha)100.8 437.4 Q
(vior for the recei)-.22 E .33 -.165(ve q)-.275 H(ueue that is).165 E
(acceptable to the application.)100.8 450.4 Q(Ho)100.8 467 Q 2.75(was)
-.275 G(ender reacts to a slo)-2.75 E 2.75(wr)-.275 G(ecei)-2.75 E -.165
(ve)-.275 G 2.75(rn).165 G(oti\214cation will depend lar)-2.75 E
(gely on beha)-.198 E(vior required)-.22 E(by the application.)100.8 480
Q -.165(Fo)5.5 G 2.75(rt).165 G
(his reason, an implementation should emplo)-2.75 E 2.75(yam)-.11 G
(echanism to)-2.75 E(inform the application that the sender is slo)100.8
493 Q 2.75(wa)-.275 G(nd for the application to indicate a course of)
-2.75 E(action for the sending DCCP to follo)100.8 506 Q 4.18 -.715
(w. T)-.275 H(here should be no def).715 E(ault beha)-.11 E
(vior for the)-.22 E(sender')100.8 519 Q 2.75(sr)-.605 G
(esponse to a Slo)-2.75 E 2.75(wR)-.275 G(ecei)-2.75 E -.165(ve)-.275 G
2.75(rn).165 G(oti\214cation, since an appropriate response is not)-2.75
E(dependent on information that is maintained by the transport layer)
100.8 532 Q(.)-.605 E F1(5.)72 558 Q/F3 14/Times-Bold@0 SF
(Security Considerations)5.5 E F0(TBD)100.8 574.6 Q F1(6.)72 600.6 Q F3
(IAN)5.5 E 3.5(AC)-.28 G(onsiderations)-3.5 E F0
(This document does not introduce an)100.8 617.2 Q 2.75(yn)-.165 G
(umbers for consideration by IAN)-2.75 E(A.)-.385 E F1(7.)72 643.2 Q F3
(Refer)5.5 E(ences)-.252 E F0([DCCP] Eddie K)100.8 659.8 Q(ohler)-.385 E
2.75(,M)-.44 G(ark Handle)-2.75 E 1.43 -.715(y, S)-.165 H(ally Flo).715
E(yd, and Jitendra P)-.11 E(adh)-.165 E 2.75(ye. Datagram)-.055 F
(Congestion Control Protocol \(DCCP\). W)129.6 672.8 Q(ork in progress.)
-.88 E([DCCP-PR)100.8 689.4 Q(OBLEM] Sally Flo)-.44 E(yd, Mark Handle)
-.11 E 1.43 -.715(y, E)-.165 H(ddie K).715 E(ohler)-.385 E 5.5(.P)-.605
G(roblem Statment for)-5.5 E(DCCP)129.6 702.4 Q 2.75(.W)-1.221 G
(ork in progress.)-3.63 E 295.919(Lanphear Section)72 769 R 2.75(7. [P)
2.75 F(age 14])-.165 E EP
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(April 2003)2.75 E(October 2002)112.127 E([RFC 2026] S. Bradner)100.8 85
Q 2.75(.T)-.605 G(he Internet Standards Process---Re)-2.75 E
(vision 3. RFC 2026.)-.275 E/F1 11/Times-Bold@0 SF(8.)72 114.6 Q/F2 14
/Times-Bold@0 SF -.7(Au)5.5 G(thor').7 E 3.5(sA)-.518 G(ddr)-3.5 E(ess)
-.252 E F0(Damon Lanphear <damonlan@real.com>)100.8 133.6 Q
(Media Systems De)100.8 159.6 Q -.165(ve)-.275 G(lopment).165 E
(RealNetw)100.8 172.6 Q(orks, Inc.)-.11 E(PO Box 91123)100.8 185.6 Q
(Seattle, W)100.8 198.6 Q 2.75(A9)-1.32 G(8111-91123)-2.75 E(USA)100.8
211.6 Q 295.919(Lanphear Section)72 769 R 2.75(8. [P)2.75 F(age 15])
-.165 E EP
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