On Congestion Control and Fair Bandwidth Allocation in the Internet

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


PhD Thesis Defence


Title: "On Congestion Control and Fair Bandwidth Allocation in the Internet"

By

Mr. Shan Chen


Abstract

The Internet has remarkably changed all aspects of our daily life, and while it 
has yet to reach its full potential, it unfortunately, relies on the TCP/IP 
architecture which has already shown its limitations. In the layered design of 
the TCP/IP architecture, the Network Layer only provides best-effort packet 
delivery service, while the efficiency and fairness are relinquished to the 
congestion control mechanism implemented in the Transport Layer of the end 
systems. The TCP congestion control algorithm originally designed for the 
homogenous wired network is facing great challenges in the ever changing and 
more heterogeneous Internet. For example, conventional TCP cannot perform well 
in networks with high bandwidth-delay product or in wireless networks with 
non-congestion-related packet losses. On the other hand, designed for packet 
routing, IP networks are vulnerable to misbehaving end systems. Quality of 
Service (QoS) enhancements on IP networks have been proposed for decades yet 
they still are not deployed widely due to their complexity. With the current 
scale of the Internet, any radical changes to the TCP/IP protocol stack are 
unlikely. Simple but effective enhancements involving modifications in only one 
part of the Internet, either the end systems or the intermediate routers, seem 
to be more practical.

This thesis focuses on congestion control and fair bandwidth allocation issues 
in the Internet and discusses how the intermediate routers or the end systems 
can be enhanced to adapt to the heterogeneous Internet. More specifically, we 
study the performance of TCP protocols in high-speed networks with the emphasis 
on how the synchronized loss effect affects the fairness principle achieved by 
many newly proposed TCP variants in high-speed networks. We also investigate 
the issue of taming misbehaving flows in the IP networks. We propose a new 
low-cost AQM scheme, SiFTM, to provide better intra-and inter-protocol fairness 
to support heterogeneous transmission protocols. SiFTM can prevent end users 
from acting intrusively thus promoting end-to-end congestion control 
mechanisms. Finally we study the TCP performance in IEEE 802.11 WLAN which is 
currently the most popular wireless network application in the Internet. We 
identify some  useful techniques that can improve the performance of TCP in 
such WLAN scenarios.


Date:			Friday, 3 July 2009

Time:			10:30am-12:30pm

Venue:			Room 3501
 			Lifts 25-26

Chairman:		Prof. Richard So (IELM)

Committee Members:	Prof. Brahim Bensaou (Supervisor)
 			Prof. Lei Chen
 			Prof. Jogesh Muppala
 			Prof. Danny Tsang (ECE)
 			Prof. Sammy Chan (Elec. Engg., City Univ.)


**** ALL are Welcome ****