Congestion Control for High Bandwidth-Delay Product NetworksMotivationDesign RationaleThe Protocol – XCP (1/2)The Protocol – XCP (2/2)Issues/DiscussionCongestion Control Congestion Control for High Bandwidth-Delay for High Bandwidth-Delay Product NetworksProduct NetworksAditya Umrani(aumrani)MotivationMotivationHigh Delay-Bandwidth Product Networks◦TCPOscillatory and InstableInefficient Gain limited to A.I.Short flows, slow startThroughput – inversely proportional to RTTRef: Analysis of Increase and Decrease Algorithms for Congestion Avoidance in Computer Networks – by Chiu & JainDesign RationaleDesign RationaleConservative Increase, Aggressive DecreasePacket Mark v/s Packet Loss◦Should signal degree of congestionSources must adapt to delay in feedback loopTraffic Dynamics – Independent of number of flows◦Decoupling efficiency control and fairness controlEfficiency – aggregate trafficFairness – relative throughput of flowsThe Protocol – XCP (1/2)The Protocol – XCP (1/2)Congestion Header3 entities◦XCP Sendercwnd = congestion window of outstanding packetsrtt = estimate of round trip times = packet sizecwnd = max(cwnd + H_feedback,s)The Protocol – XCP (2/2)The Protocol – XCP (2/2)XCP Receiver◦Copy congestion header from packet to its ACKXCP Router◦Efficiency Controller (MIMD)Maximize link utilizationMinimize drop rates and persistent queuesØ = α.d.S – β.Q◦Fairness Controller (AIMD)Allocate Ø proportional to current throughputsBandwidth ShufflingIssues/DiscussionIssues/DiscussionChanges in current routers◦Adv: No additional state◦Disadv: Deployment of a new protocolWireless Networks◦Any issue relates to the high loss.◦How does this affect
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