Understanding Congestion Control in Multi-hop Wireless Mesh Networks

1. 1 3 1 3 2 2 Link Neighborhood 4 5 6 4 5 6 9 1 8 8 7 9 7 9 18 18 7 2 17 17 23 23 10 10 24 24 16 16 5 6 SumitRangwala, ApoorvaJindal, Ki-Young Jang, KonstantinosPsounis, and RameshGovindan University of Southern California 22 22 Understanding Congestion Control in Multi-hop Wireless Mesh Networks 12 12 8 4 26 26 13 13 15 15 9 8 10 Problem Description: Congestion Control in 802.11x Wireless Networks 19 19 3 1 2 3 4 5 6 7 11 11 10 20 20 All incoming and outgoing links from the sender, receiver, all the neighbors of sender, and all the neighbors of receiver What is wrong with TCP? Congestion is a Neighborhood Phenomenon 11 14 14 Link ≡ sender-receiver pair Stack Topology TCP starves the middle flow Proposed Solution: Neighborhood-Centric Transport WCP: AIMD Based Transport Protocol WCPCap: Explicit Rate Control Protocol • Neighborhood congestion detection • Any link in the link neighborhood is congested • Neighborhood RTT • MaximumRTT of all flows traversing a link neighborhood • End-to-end behavior • Reduce a flow’s rate if at least one of the traversed neighborhoods iscongested • Use the maximum RTT among all traversed neighborhood RTTs to “clock” the rate changes • Neighborhood per flow rate • Calculates sustainable fair rate for each flow in a link neighborhood • Requires spare capacity calculation • End-to-end behavior • Flows send at a rate that is minimum of the rate assigned at each traversed neighborhood Evaluation: WCP fairer than TCP, WCPCap achieves max-min fairness Experimentation Setup • Simulation • Qualnet 3.9.5 • 802.11b with default parameters • 11Mbps , no rate adaptation, 512 byte data packet • Zero channel losses • Buffer size: 64 packets • Real World Experiments • Click modular router on Linux • Same code as in simulation Simulations: Diamond Topology Chain-cross Topology Simulations: Stack Topology Simulations: Chain-cross Topology Diamond Topology Arbitrary Topology Real-world Experiments: Arbitrary Topology Real-world Experiments: Stack Topology