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Fixed Point Approximations for TCP Behavior in an AQM Network. Tian Bu Don Towsley U. Massachusetts. Challenge. explore alternate network configurations prior to deployment/reconfiguration explore alternate active queue management (AQM), congestion control designs Parameter space:
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Fixed Point Approximations for TCP Behavior in an AQM Network Tian Bu Don Towsley U. Massachusetts
Challenge • explore alternate network configurations prior to deployment/reconfiguration • explore alternate active queue management (AQM), congestion controldesigns Parameter space: • 100s - 1000s network elements • 10,000s - 100,000s of flows (TCP, UDP, NG)
TCP throughput New Ideas • use of fixed point methods for on-line evaluation of steady-state behavior of large networks handling responsive flows (e.g., TCP) avg. queue length • can also account for • ECN • non-responsive flows (e.g., UDP). • finite duration flows
N TCP flows throughputs {Bi} V bottlenecked RED routers capacities {Cv } avg. queue lengths {xv } discard prob. {pv (xv )} TCP model: Bi({pv }) bottleneck router model iBi({xv}) = Cv , v =1,…,V V equations, V unknowns Fixed Point Approach TCP flow Bi RED router Cv, pv(xv)
Results: single RED router • Scale the RED parameters with N TCP flows N = 20,40,60, 80
Results: tandem network End-to-end loss probability
Future Research • derive the existence and uniqueness • account for imperfect feedback • account for finite duration flow of non-poisson arrival and non-exponentially distributed transfer size