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


PhD Thesis Defence


"Alleviating Problems due to Resource Constraints in Computer
Networks Using Additional Information"

By

Mr. Lei Zhang


Abstract

Motivated and driven by the development of real-time multimedia
applications, Quality of Service (QoS) has been a hot research area in
computer networks for quite a long time.

However, providing QoS in computer networks always faces network resource
constraints: bandwidth, delay, and etc. Therefore, in this thesis, we try
to alleviate these problems using additional information. To make it easy
for presentation, we first propose a multi-layer model for the problems
and then study different problems in each layer. They are: online QoS
routing problems in the routing layer, VPN provisioning problems and
location management problems in mobile ad-hoc networks in the network
layer, and cooperative downloading schedule problem in peer-to-peer
networks in the application layer. In each of these problems, we are
facing the same problem of limited network resources, and we make use of
different additional information to alleviate the problem.

In the routing layer, we consider the online QoS routing. The objective is
to minimize the call blocking probability due to insufficient network
resources to support the required quality of service. A scheme is proposed
to protect those critical links/paths that are crucial for future
requests. In this problem, the network resource constraint is the limited
network routing ability and the information we made use of is the
co-relationship among the network paths/links which can reflect link
criticality.

In the network layer, we are mainly concerned about those supporting
technologies which can provide underlying systems or service models for
the upper routing layer. Two problems are studied. The first problem is
the provisioning problem with enhanced Hose model in Virtual Private
Networks (VPN). We enhanced the hose model specification to support delay
requirements at the VPN endpoints. In this problem, the network resource
constraint is the limited link bandwidth available for provisioning. We
exploit the additional information of delay and the concept of tree
diameter to alleviate the problem. The second problem is the location
management problem in Mobile Ad-hoc Networks (MANET). We proposed an
integrated location management and location-aided routing system which
uses location information as a guidance in QoS routing.

In the application layer, we study the downloading problem of large-scale
files in P2P networks. In P2P networks, limited downloading and uploading
bandwidth is restricting the performance of the system, which results in
long downloading time of the files. Proximity is introduced to minimize
the average downloading time and to maximize uploading link capacities.


Date:			Friday, 18 August 2006

Time:			2:30p.m.-4:30p.m.

Venue:			Room 5510
			Lifts 25-26

Chairman:		Prof. Zikang Tang (PHYS)

Committee Members:	Prof. Jogesh Muppala (Supervisor)
			Prof. Gary Chan
			Prof. Qian Zhang
			Prof. Danny Tsang (ECE)
			Prof. Dah Ming Chiu (Information Engg., CUHK)


**** ALL are Welcome ****