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How to Identify the Speed Limiting Factor of a TCP Flow E2EMON 2006 Vancouver Mark Timmer. April 3, 2006. Co-authors: Pieter-Tjerk de Boer and Aiko Pras. E2EMON, April 3, 2006. How to Identify the Speed Limiting Factor of a TCP Flow. Contents. Motivation Related work Possible factors
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How to Identifythe Speed Limiting Factorof a TCP FlowE2EMON 2006VancouverMark Timmer April 3, 2006 Co-authors: Pieter-Tjerk de Boer and Aiko Pras
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Contents • Motivation • Related work • Possible factors • Overview: identifying the limiting factors • One factor in-depth • Measurement results • Conclusions
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Motivation • Surfnet: 1 Gbit 10 Gbit • Upgrades still useful? • Approach: Identify speed limiting factor
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Related work • Y. Zhang, L. Breslau, V. Paxson, and S. Shenker, “On the characteristics and origins of internet flow rates”, Proceedings of SIGCOMM’02 • M. Siekkinen, G. Urvoy-Keller, E.W. Biersack, and T. En-Najjary, “Root cause analysis for long-lived tcp connections”, Proceedings of CoNEXT’05
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Speed limiting factors of a TCP flow
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Overview: identifying the limiting factors Data repository of packet traces • Information directly available: • Arrival time • IP header (source, destination) • TCP header (port numbers, sequence number, acknowledgment number, size of receive window) • Information calculated: • Number of outstanding bytes • Achieved throughput
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Application layer limitations (1) Slow sender limitation Identification • Measure idle period percentage • Careful when receive window is empty Note: We only consider flows measured at the sending side
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Application layer limitations (2) Slow receiver limitation Identification • Measure how often the receive window decreases
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Application layer limitations (3) Application protocol limitation Identification • Measure how often an ACK contains data Note: We only consider flows sending data one-way
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Network limitation (1) Limited by loss / retransmission • ‘TCP Friendly formula’
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Network limitation (2) Limited by delay • Large buffers • Entire receive window stored • Injecting more packets more delay
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow TCP buffers limitations The receive buffer limitation The send buffer limitation
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow In-depth: the receive window limitation • Peaks
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Measurement results
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Conclusions • Upgrading network still useful • However, many flows limited by buffers • Recommentations: • Perform statistical analyses • Develop tool to ‘fix’ TCP-buffer limited flows • Detect changes of limiting factor in time
E2EMON, April 3, 2006 How to Identify the Speed Limiting Factor of a TCP Flow Questions?