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Proceedings Paper

Efficiency of TCP-friendly window adjustment strategies in wired/wireless networks
Author(s): Chi Zhang; Vassilis Tsaoussidis
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Paper Abstract

TCP(a,b) protocols parameterize the congestion window increase value and decrease ratio , motivated by the QoS requirements of multimedia applications for smooth rate adjustments. Based on a projection of the expected throughput of standard TCP(1,.5), modified versions of the protocol have been designed to generate smoother traffic patterns and to maintain a friendly behavior. In this paper, we study the design assumptions of TCP(a,b) and we discuss the impact of equation-based modulation of a and b on application efficiency. We confirm experimentally that, in general, smoothness and responsiveness constitute a tradeoff; however, we uncover undesirable dynamics of the protocols when the network is heterogeneous (wired/wireless) or the flow characteristics do not follow a prescribed and static behavior. For example, we show that smooth backward adjustments confine the protocol's capability to exploit resources that become available rapidly after a handoff in mobile network, and embarrass the fair and efficient growth of incoming flows. Furthermore, we show that in the context of wireless networks with high error rate, a low a dictates a conservative behavior that degrades the protocol performance with both best-effort and real-time applications; and in the context of high contention of heterogeneous flows, a low a does not contribute to efficiency and friendliness.

Paper Details

Date Published: 8 July 2002
PDF: 15 pages
Proc. SPIE 4868, Scalability and Traffic Control in IP Networks II, (8 July 2002); doi: 10.1117/12.475263
Show Author Affiliations
Chi Zhang, Northeastern Univ. (United States)
Vassilis Tsaoussidis, Northeastern Univ. (United States)

Published in SPIE Proceedings Vol. 4868:
Scalability and Traffic Control in IP Networks II
Victor Firoiu; Zhi-Li Zhang, Editor(s)

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