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Congestion Control for High Bandwidth-Delay Product Networks

Congestion Control for High Bandwidth-Delay Product Networks. Aditya Umrani(aumrani). Motivation. High Delay-Bandwidth Product Networks TCP Oscillatory and Instable Inefficient Gain limited to A.I. Short flows, slow start Throughput – inversely proportional to RTT.

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Congestion Control for High Bandwidth-Delay Product Networks

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  1. Congestion Control for High Bandwidth-Delay Product Networks Aditya Umrani(aumrani)

  2. Motivation • High Delay-Bandwidth Product Networks • TCP • Oscillatory and Instable • Inefficient • Gain limited to A.I. • Short flows, slow start • Throughput – inversely proportional to RTT Ref: Analysis of Increase and Decrease Algorithms for Congestion Avoidance in Computer Networks – by Chiu & Jain

  3. Design Rationale • Conservative Increase, Aggressive Decrease • Packet Mark v/s Packet Loss • Should signal degree of congestion • Sources must adapt to delay in feedback loop • Traffic Dynamics – Independent of number of flows • Decoupling efficiency control and fairness control • Efficiency – aggregate traffic • Fairness – relative throughput of flows

  4. The Protocol – XCP (1/2) • Congestion Header • 3 entities • XCP Sender • cwnd = congestion window of outstanding packets • rtt = estimate of round trip time • s = packet size • cwnd = max(cwnd + H_feedback,s)

  5. The Protocol – XCP (2/2) • XCP Receiver • Copy congestion header from packet to its ACK • XCP Router • Efficiency Controller (MIMD) • Maximize link utilization • Minimize drop rates and persistent queues • Ø = α.d.S – β.Q • Fairness Controller (AIMD) • Allocate Ø proportional to current throughputs • Bandwidth Shuffling

  6. Issues/Discussion • Changes in current routers • Adv: No additional state • Disadv: Deployment of a new protocol • Wireless Networks • Any issue relates to the high loss. • How does this affect XCP?

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