MPhil Thesis Defence


"Active Queue Management Schemes Using A Capture-Recapture Model"

By

Mr. Ming-Kit Chan


Abstract

To provide fair bandwidth sharing for TCP flows, the Internet depends on
the cooperation between TCP sender and subnet routers to adjust source
data rates in the presence of network congestion. On the other hand,
Active Queue Management (AQM) schemes are used in the Internet routers to
protect TCP flows against non-responsive flows. As a result, one of the
major objectives for an Internet router is to allocate these flows in
order to achieve maximum fairness. However, most of the existing AQM
schemes cannot provide accurate fair bandwidth share.

In this thesis, we propose a new AQM scheme called CAP (CAPture-recapture
fair sharing) to solve this problem. The CAP algorithm estimates the
source data rates and the fair share by the random captures of the
incoming packets. The CAP algorithm is based on a capture-recapture (CR)
model, which was originally developed for estimating the size of animal
populations. Conceptually, the CR model depends on several key ideas:
animals are captured randomly, marked, released and then recaptured
randomly from the population. We have applied the same approach to the AQM
schemes by capturing packets in the buffer. The scheme is simple to
implement, robust, efficient, and does not require keeping per-flow
information. Using analysis and simulation, CAP is shown to provide highly
accurate fair bandwidth share under different network configurations. Our
experiments also show the CAP algorithm outperforming the existing
mechanisms. Finally, we implement our algorithm in a software router. The
results produced by using real network traffic conform to the simulation
results.


Date:			Monday, 26 August 2002

Time:			10:00a.m.-12:00noon

Venue:			Room 1505
			Lifts 25-26

Committee Members:		Dr. Mounir Hamdi (Supervisor)
			Dr. Brahim Bensaou (Chairman)
			Dr. Danny H.K. Tsang (ELEC)



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