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).

Internet2 Spring Members Meeting, April 9-11, 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, 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, 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, AbstractAbstract 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, Slow Start (Theory)

Internet2 Spring Members Meeting, April 9-11, 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, Typical Results

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

Internet2 Spring Members Meeting, April 9-11, 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, ComparisonComparison

Internet2 Spring Members Meeting, April 9-11, 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, Further Information Paper presented at PAM