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Improving Restart of Idle TCP Connections

Vikram Visweswaraiah and John Heidemann
USC/Information Sciences Institute

Abstract

TCP congestion avoidance mechanisms are based on adjustments to the congestion-window size, triggered by the ACK clock. These mechanisms are not well matched to large but intermittent bursts of traffic, such as responses from a HTTP/1.1-based web server. Idle periods between bursts (web page replies) stop the ACK clock and hence disrupt even data flow. When restarting data flow after an idle period, current implementations either enforce slow start (SSR) or use the prior congestion window (NSSR). The former approach, while conservative, leads to low effective throughput in cases like P-HTTP. The latter case optimistically sends a large burst of back-to-back packets, risking router buffer overflow and subsequent packet loss. This paper proposes a third alternative: pacing some packets at a certain rate until the ACK clock can be restarted. We describe the motivation and implementation of this third alternative and present simulation results which show that it achieves the elapsed-time performance comparable to NSSR and loss behavior of SSR.

Availability

This paper is available in several formats: abstract web page with pointers and cites, gzip'ed postscript, PDF, paper copies can be obtained by mail to the authors. Copyright terms for this paper appear below.

Reference

Visweswaraiah97b: Vikram Visweswaraiah and John Heidemann. Improving Restart of Idle TCP Connections. Technical Report 97-661, University of Southern California, November, 1997. <http://www.isi.edu/~johnh/PAPERS/Visweswaraiah97b.html>.

@techreport{Visweswaraiah97b,
	author = "Vikram Visweswaraiah and John Heidemann",
	title = "Improving Restart of Idle {TCP} Connections",
	institution = "University of Southern California",
	year = "1997",
	number = "97-661",
	month = "November",
	keywords = "lsam, tcp del rey, rate-based pacing",
	url = "http://www.isi.edu/~johnh/PAPERS/Visweswaraiah97b.html",
	psurl = "http://www.isi.edu/~johnh/PAPERS/Visweswaraiah97b.ps.gz",
	pdfurl = "http://www.isi.edu/~johnh/PAPERS/Visweswaraiah97b.pdf",
	copyrightholder = "author",
}

Copyright

This paper is copyright © 1997 by its authors. Permission to make digital or hard copies of part or all of this work for personal use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that new copies bear this notice and the full citation on the first page. Abstracting with credit is permitted.

To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission of the authors.