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BWdetail: A bandwidth tester with detailed reporting

BWdetail: A bandwidth tester with detailed reporting . Masters of Engineering Project Presentation Mark McGinley April 19, 2007 Advisor: Malathi Veeraraghavan

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BWdetail: A bandwidth tester with detailed reporting

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  1. BWdetail: A bandwidth tester with detailed reporting Masters of Engineering Project Presentation Mark McGinley April 19, 2007 Advisor: Malathi Veeraraghavan Acknowledgement: This work was carried out under the sponsorship of NSF ITR-0312376, NSF ANI-0335190, and DOE DE-FG02-04ER25640 grants.

  2. Outline • Problem Statement • Related Work • Overview of BWdetail • Features and Uses • Demonstration • Conclusion

  3. Problem Statement • Growing eScience traffic Terabytes / month ESnet Monthly Accepted Traffic, January, 2000 – June, 2006 Ref. 1

  4. Problem Statement • Scientific research efforts such as Atlas characterized by: • Large datasets • Geographically distributed collaborators • 1800 physicists, 150 universitiesand laboratories • Supporting high speed transfers of datasets often requires system tuning, diagnostics [2]

  5. Outline • Problem Statement • Related Work • Overview of BWdetail • Features and Uses • Demonstration • Conclusion

  6. Related Work • Iperf from NLANR • Successor to ttcp, similar to nttcp, nuttcp • Web100 • Host system software (autotuning) • Lack of instrumentation/tools for diagnosing performance issues • Iperf100 • Web100-based Iperf

  7. Related Work • Nettest • Incorporates Iperf • Net100 • Leverages Web100 to eliminate “wizard gap” with autotuning • tcpdump

  8. Related Work • Iperf

  9. Related Work • tcpdump

  10. Related Work • BWdetail

  11. Related Work

  12. Outline • Problem Statement • Related Work • Overview of BWdetail • Features and Uses • Demonstration • Conclusion

  13. Overview of BWdetail • Bandwidth estimation ability of Iperf • Instrumentation capabilities similar to Web100, without kernel modification

  14. Overview of BWdetail • Software architecture • C program • TCP_INFO struct associated with each socket • Kernel parameters read/written using getsockopt(), setsockopt(), sysctl(), system()

  15. Outline • Problem Statement • Related Work • Overview of BWdetail • Features and Uses • Demonstration • Conclusion

  16. Features and Uses • Data transfer for goodput estimation • Memory-to-memory is most common usage • Disk/memory-to-disk/memory • Memory transfer can either be a specific size or duration • Disk transfer using a file of specific size, to eliminate caching effects

  17. Features and Uses • Effect of caching • 1 GB disk-to-disk successive transfer

  18. Features and Uses • Multi-threaded client • Client uses separate threads to send data and monitor flow

  19. Features and Uses • Tunable parameters from command line • Socket buffer size • TCP congestion control algorithm • CTCP-enabled Web100 capable • SACK, Nagle, no metrics save

  20. Features and Uses • Adjustable reporting granularity • Client and server report goodput over some small, configurable interval (100ms) • Client reports cwnd, RTT, etc, every smaller, configurable interval (5ms)

  21. Features and Uses • Applications • Research regarding transport protocols • CTCP/Reno/BIC • Cwnd and RTT measurements • Improving performance on a path • Records relevant kernel parameters • Ongoing recording of cwnd, RTT, goodput • Change parameters, repeat

  22. Outline • Problem Statement • Related Work • Overview of BWdetail • Features and Uses • Demonstration • Conclusion

  23. Demonstration Results

  24. Outline • Problem Statement • Related Work • Overview of BWdetail • Features and Uses • Demonstration • Conclusion

  25. Conclusion • Available bandwidth estimation • Instrumentation such as cwnd without requiring kernel modification or privileged access

  26. Thank you Questions?

  27. References • [1] W.E. Johnston, ESnet4: Networking for the Future of DOE Science, http://www.es.net/ESnet4/ESnet4-Internet2Members-Dec-06-2006-1.ppt, Dec. 5, 2006 • [2] The Atlas Experiment, www.atlas.ch

  28. Limitations • Does not replace tcpdump • tcpdump handles content • Needed to detect retransmissions, Ethernet PAUSE frames, verification • Incorporation of libpcap capabilities would degrade the non-interference status of BWdetail • BWdetail is interested in statistics, not content

  29. Limitations • BWdetail does not replace an expert • Still requires knowledge to tune, does not provide autotuning • Use of TCP_INFO struct presents portability issues

  30. Impact of monitoring • Minimal, even at ~1 Gbps

  31. RTT

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