Router-Assisted Congestion Control for Wired and Wireless High-Speed Networks

The Hong Kong University of Science and Technology
Department of Computer Science and Engineering


PhD Thesis Defence


Title: "Router-Assisted Congestion Control for Wired and Wireless High-Speed Networks"

By

Mr. Jian PU


Abstract

The resource management mechanisms such as congestion control protocols and 
flow rate adaptation algorithms are critically important to make the Internet 
work efficiently and stably. As more and more high-speed links, lossy links, 
long-delay links and variable-delay links are widely deployed in the Internet, 
traditional end-to-end congestion control schemes exhibit several shortcomings, 
such as poor utilization of high-speed links, unfair bandwidth allocation among 
flows with different round-trip times (RTTs), incorrect interpretation of 
bit-error packet loss as congestion, and slow responsiveness to fast-changing 
physical conditions of mobile nodes. To address these problems, we develop 
flexible and adaptive cross-layer schemes that optimize the performance 
(throughput, latency, fairness, etc.) of the whole networking system. We 
propose Quick Flow Control Protocol (QFCP) as a router-assisted congestion 
control protocol for high bandwidth-delay product networks. It allows flows to 
start with high initial sending rates indicated by routers along the path and 
to converge to the fair-share sending rate quickly based on feedbacks from 
routers. We next extend QFCP to wireless networks so that it can distinguish 
bit-error loss from congestion loss and can probe the unknown bandwidth 
capacity of wireless links to calculate the router feedback. Time-constraint 
flows are very common in vehicular communications. They have fixed start and 
stop times and try to maximize the transferred data volume during the limited 
connection time. We find that the traditional fairness concept solely based on 
instantaneous flow rates is not suitable for this scenario. Therefore, we 
propose new practical bandwidth sharing schemes for transferring data with 
fast-moving wireless nodes such as vehicles based on the utility fairness. We 
also validate and evaluate our developed schemes under various environments and 
conditions comparing with other existing protocols. Performance evaluation is 
presented here and the results of our protocols are promising.


Date:			Wednesday, 23 June 2010

Time:			10:00am – 12:00noon

Venue:			Room 3501
 			Lifts 25/26

Chairman:		Prof. Amine Bermak (ECE)

Committee Members:	Prof. Mounir Hamdi (Supervisor)
 			Prof. Gary Chan
 			Prof. Jogesh Muppala
                      	Prof. Ross Murch (ECE)
                         Prof. Hussein Mouftah (Inf. Tech. & Engg.,
 						Univ. of Ottawa)


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