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Example diagnostic tool output End-to-end goal: 4 Mb/s over a 200 ms path including this section Tester at IP address: xxx.xxx.115.170 Target at IP address: xxx.xxx.247.109 Warning: TCP connection is not using SACK Fail: Received window scale is 0, it should be 2. Diagnosis: TCP on the test target is not properly configured for this path. > See TCP tuning instructions at http://www.psc.edu/networking/perf_tune.html Pass data rate check: maximum data rate was 4.784178 Mb/s Fail: loss event rate: 0.025248% (3960 pkts between loss events) Diagnosis: there is too much background (non-congested) packet loss. The events averaged 1.750000 losses each, for a total loss rate of 0.0441836% FYI: To get 4 Mb/s with a 1448 byte MSS on a 200 ms path the total end-to-end loss budget is 0.010274% (9733 pkts between losses). Warning: could not measure queue length due to previously reported bottlenecks Diagnosis: there is a bottleneck in the tester itself or test target (e.g insufficient buffer space or too much CPU load) > Correct previously identified TCP configuration problems > Localize all path problems by testing progressively smaller sections of the full path. FYI: This path may pass with a less strenuous application: Try rate=4 Mb/s, rtt=106 ms Or if you can raise the MTU: Try rate=4 Mb/s, rtt=662 ms, mtu=9000 Some events in this run were not completely diagnosed. |