Introduction
In response to a reported performance problem between SSRL and ANL reported by Brian Kobilka's group, Phil Reese of Stanford campus looked at the perfSONAR Bwctl (iperf) plots shown below.
Stanford to ESnet at Sunnyvale |
Denver/ESnet to Stanford |
Chicago/Esnet to Stanford |
ANL/ESnet to Stanford |
|---|---|---|---|
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It is seen that as the distance from source to Destination increases, the asymmetry between the two directions also increases. This could be due to loss in one of the paths (the one to Stanford). Any loss can dramatically degrade performance. See for example:
- http://fasterdata.es.net/performance-testing/perfsonar/troubleshooting/packet-loss/
- http://staff.psc.edu/mathis/papers/JTechs200105/mgp00020.html
- The following graph might be useful: it shows the random loss rate affect on tcp flavors across a dummynet on a 250mbps link (this was before gig-e was common place). 162ms. Single tcp flow. The full analysis available at http://www.slac.stanford.edu/~ytl/thesis.pdf (~pp152). warning: long and arduous content!
