Proposed Solution: Proposed Solution: Neighborhood-Centric TransportNeighborhood-Centric Transport

Evaluation: Evaluation: WCP fairer than TCP, WCPCap achieves max-min fairnessWCP fairer than TCP, WCPCap achieves max-min fairness

Understanding Congestion Control in Multi-hop Understanding Congestion Control in Multi-hop Wireless Mesh NetworksWireless Mesh Networks

Sumit Rangwala, Apoorva Jindal, Ki-Young Jang, Konstantinos Psounis, and Ramesh GovindanUniversity of Southern California

What is wrong with TCP? Congestion is a Neighborhood Phenomenon

WCP: AIMD Based Transport Protocol WCPCap: Explicit Rate Control Protocol

TCP starves the middle flow

All incoming and outgoing links from the sender, receiver, all the neighbors of sender, and all the neighbors of receiver

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Link Neighborhood

Problem Description: Problem Description: Congestion Control in 802.11x Wireless NetworksCongestion Control in 802.11x Wireless Networks

Stack Topology

Diamond Topology

Chain-cross Topology Simulations: Chain-cross Topology

Simulations: Diamond Topology

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Arbitrary Topology Real-world Experiments: Arbitrary Topology

Simulations: Stack Topology

Real-world Experiments: Stack Topology

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

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

Link ≡ sender-receiver pair