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Measuring End-to-end Bandwidth with Iperf using Web100

This presentation explores the use of Iperf and Web100 for accurately measuring end-to-end bandwidth. It discusses the challenges and benefits of using these tools and presents a modified version of Iperf that detects the end of slow start. The results and potential future improvements are also discussed.

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Measuring End-to-end Bandwidth with Iperf using Web100

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  1. Measuring End-to-end Bandwidth with Iperf using Web100 Presented by Warren Matthews (SLAC) on behalf of Ajay Tirumala (U of Illinois), Les Cottrell (SLAC) and Tom Dunigan (ORNL).

  2. Jim said • Comments and criticisms of how easy it is to download, patch, etc. • Comment on the completeness of the documentation we have available. Internet2 Spring Members Meeting, April 9-11, 2003.

  3. Not Really Web100 Issues • Unix/Linux machines on the SLAC network are heavily taylored. Heavy reliance on AFS. • Problems with running customized kernels in taylored (considered secure) environment • Developers very responsive Internet2 Spring Members Meeting, April 9-11, 2003.

  4. SLAC and Web100 • Future of HENP depends on network performance • Genetics, Astronomy, VoD • Ability to monitor and tune TCP is essential • Web100/Net100 very useful tool Internet2 Spring Members Meeting, April 9-11, 2003.

  5. Abstract • Iperf considered accurate but intrusive • Use web100 to detect end of slow start • Measurement within 10% • Save 94% time, 92% traffic Internet2 Spring Members Meeting, April 9-11, 2003.

  6. Slow Start (Theory) Internet2 Spring Members Meeting, April 9-11, 2003.

  7. Standard Iperf • Tool of choice for many network admins • Errors due to long slow start • Typically run for 20 seconds (default is 10) Internet2 Spring Members Meeting, April 9-11, 2003.

  8. Typical Results Internet2 Spring Members Meeting, April 9-11, 2003.

  9. Non-Typical Results Internet2 Spring Members Meeting, April 9-11, 2003.

  10. Modified Iperf • Modify Iperf client • Web100 required on client only • Paper describes algorithm to detect end of slow start • Included in release Internet2 Spring Members Meeting, April 9-11, 2003.

  11. Comparison Internet2 Spring Members Meeting, April 9-11, 2003.

  12. Further Work • Test with new TCP stacks • Expect will work better • Test with faster links • GigE • 100 ms latency • Correlate congestion signals, loss and retransmission information with bandwidth achieved. Internet2 Spring Members Meeting, April 9-11, 2003.

  13. Further Information • Paper presented at PAM Internet2 Spring Members Meeting, April 9-11, 2003.

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