[...]... 96 98 10 0 10 3 10 4 10 4 10 6 10 7 10 8 10 9 11 3 11 5 11 9 11 9 11 9 12 1 12 3 12 3 12 6 12 8 12 9 13 0 13 1 13 2 13 3 13 3 13 4 13 5 13 5 13 6 13 7 13 9 14 3 14 9 15 5 16 0 16 1 16 4 16 7 16 9 17 5 17 6 x CONTENTS 5 Internet traffic management – the ISP perspective 5 .1 The nature of Internet traffic 5.2 Traffic engineering 5.2 .1 A simple example 5.2.2 Multi-Protocol... CONTENTS 2 .11 .2 Other scalability hazards 2 .12 Explicit feedback 2 .12 .1 Explicit congestion notification 2 .12 .2 Precise feedback 2 .13 Special environments 2 .14 Congestion control and OSI layers 2 .14 .1 Circuits as a hindrance 2 .15 Multicast congestion control 2 .15 .1 Problems 2 .15 .2 Sender- and receiver-based schemes 2 .16 Incentive... 71 72 78 81 87 88 94 96 10 0 4 .1 4.2 4.3 4.4 A spurious timeout The congestion manager Connection splitting Pacing 11 0 12 0 12 4 12 7 11 12 12 17 18 20 20 22 25 25 33 35 35 41 48 50 xviii LIST OF FIGURES 4.5 Matching a fluctuating application stream onto a fluctuating congestion control. .. 5.3 .1 QoS building blocks 5.3.2 IntServ 5.3.3 RSVP 5.3.4 DiffServ 5.3.5 IntServ over DiffServ 5.4 Putting it all together 18 1 18 2 18 4 18 5 18 6 18 7 18 8 19 0 19 1 19 1 19 2 19 4 6 The future of Internet congestion. .. 19 9 200 2 01 203 205 206 209 211 212 214 214 215 A Teaching congestion control with tools A .1 CAVT A .1. 1 Writing scripts A .1. 2 Teaching with CAVT A .1. 3 Internals A.2 ns A.2 .1 Using ns for teaching: the problem A.2.2 Using ns for teaching: the solution... Concluding remarks about AQM 4.5 Congestion control for multimedia applications 4.5 .1 TCP-friendly congestion control mechanisms 4.5.2 The Datagram Congestion Control Protocol (DCCP) 4.5.3 Multicast congestion control 4.6 Better-than-TCP congestion control 4.6 .1 Changing the response function 4.6.2 Delay as a congestion measure 4.6.3... congestion control 6 .1 Small deltas or big ideas? 6 .1. 1 TCP-friendliness considerations 6 .1. 2 A more aggressive framework 6.2 Incentive issues 6.2 .1 The congestion response of UDP-based 6.2.2 Will VoIP cause congestion collapse? 6.2.3 DCCP deployment considerations 6.2.4 Congestion control and QoS 6.3 Tailor-made congestion control 6.3 .1 The Adaptation... receiver-based schemes 2 .16 Incentive issues 2 .16 .1 Tragedy of the commons 2 .16 .2 Game theory 2 .16 .3 Congestion pricing 2 .17 Fairness 2 .17 .1 Max–min fairness 2 .17 .2 Utility functions 2 .17 .3 Proportional fairness 2 .17 .4 TCP friendliness 2 .18 Conclusion 3 ... 4 .11 CADPC/PTP in action 14 3 15 3 16 0 16 8 17 3 5 .1 5.2 5.3 5.4 A traffic engineering problem A generic QoS router Leaky bucket and token bucket IntServ over DiffServ 18 5 18 8 18 9 19 3 6 .1 6.2 6.3 6.4 6.5 6.6 A vector diagram of TCP Reno The test bed that was used for... A.8 A screenshot of xgraph A.9 The congestion collapse scenario with 1 Mbps from source 1 to router 2 14 1 14 2 2 21 222 224 226 228 230 2 31 232 233 1 Introduction Congestion control is a topic that has been dealt with for a long time, and it has also become a facet of daily life for Internet users Most of us know the effect: downloading, say, a movie trailer . alt="" Network Congestion Control Managing Internet Traffic Michael Welzl Leopold Franzens University of Innsbruck Network Congestion Control Network Congestion Control Managing Internet Traffic Michael. . . . . . . . . . . 17 6 x CONTENTS 5 Internet traffic management – the ISP perspective 18 1 5 .1 ThenatureofInternettraffic 18 2 5.2 Trafficengineering 18 4 5.2 .1 Asimpleexample 18 5 5.2.2 Multi-Protocol. . . . . . 10 7 4 .1. 4 Robust ECN signalling . . . . . . . . . . . . . . . . . . . . . . . . . 10 8 4 .1. 5 Spurioustimeouts 10 9 4 .1. 6 Reordering 11 3 4 .1. 7 Corruption 11 5 4.2 Maintaining congestion