33_5 - Inferring TCP Connection Characteristics Through...

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Unformatted text preview: Inferring TCP Connection Characteristics Through Passive Measurements Sharad Jaiswal , Gianluca Iannaccone , Christophe Diot , Jim Kurose , Don Towsley Computer Science Department Univ. of Massachusetts, Amherst { sharad,kurose,towsley } @cs.umass.edu Intel Research Cambridge, UK { gianluca.iannaccone,christophe.diot } @intel.com Abstract We propose a passive measurement methodology to infer and keep track of the values of two important variables as- sociated with a TCP connection: the senders congestion window (cwnd) and the connection round trip time (RTT). Together, these variables provide a valuable diagnostic of end-user-perceived network performance. Our methodology is validated via both simulation and concurrent active measurements, and is shown to be able to handle various flavors of TCP. Given our passive approach and measurement points within a Tier-1 network provider, we are able to analyze more than 10 million connections, with senders located in more than 45% of the autonomous systems in todays Internet. Our results indicate that sender throughput is frequently limited by a lack of data to send, that the TCP congestion control flavor often has minimal impact on throughput, and that the vast majority of connections do not experience significant variations in RTT during their lifetime. Index Terms Network Measurements, Traffic analysis, TCP I. INTRODUCTION TCP (Transmission Control Protocol) is the dominant end- to-end transport protocol currently deployed in the Internet, with a wide range of applications such as Web traffic, grid applications, and newly emerging peer-to-peer applications relying on TCPs transport services. Given this reliance on TCP, there is currently great interest in understanding TCPs performance and characterizing the factors (such as network congestion, sender/receiver buffer limits, and sender data- starvation) that can limit its behavior in practice. In this paper we present a passive measurement method- ology that observes the sender-to-receiver and receiver-to- sender segments in a TCP connection, and infers/tracks the time evolution of two critical sender variables: the senders congestion window ( cwnd ) and the connection round trip time ( RTT ). As we will see, with knowledge of these two values, many important characteristics of the sender, receiver, and the network path that connects them can be determined. For example, by comparing cwnd with the amount of data actually sent, one can determine when a TCP connection is starved for application-level data (i.e., that the connection could support a This work is supported by the National Science Foundation under grants EIA-0080119, ITR-0522631, and ANI- 0240487, and a gift from Sprint Corporation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Part of this work was carried out when S. Jaiswal, G. Iannaccone and C. Diot were at Sprint ATL,carried out when S....
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This note was uploaded on 12/08/2011 for the course CS 525 taught by Professor Gupta during the Spring '08 term at University of Illinois, Urbana Champaign.

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33_5 - Inferring TCP Connection Characteristics Through...

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