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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. Sumit Rangwala, Apoorva Jindal, Ki-Young Jang, Konstantinos Psounis, and Ramesh Govindan
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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 Sumit Rangwala, Apoorva Jindal, Ki-Young Jang, Konstantinos Psounis, and Ramesh Govindan 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 • Maximum RTT of all flows traversing a link neighborhood • End-to-end behavior • Reduce a flow’s rate if at least one of the traversed neighborhoods is congested • 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
