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Published 20 hours ago • verified publisher icon m-lab

MinRTT missing from a large fraction of Web100 data 2009-2017

Open mattmathis opened this issue 4 years ago • 3 comments

Diagnose root cause (which may be a bug in the underlying TCP implementation) and consider workarounds.

See OkRTT in mlab-sandbox.inspector.inspect_public_unified

mattmathis avatar Aug 17 '20 20:08 mattmathis

@mattmathis is this still happening?

laiyi-ohlsen avatar Sep 28 '20 16:09 laiyi-ohlsen

90+% of the tests 2009-2012 report suspect MinRTT 70+% of the tests 2013-2015 report suspect MinRTT 35% of 2016 and 14% of 2017 report suspect MinRTT Where suspect MinRTT means either 0 (e.g. missing) or greater than 500 mS (unlikely).

mattmathis avatar Sep 28 '20 17:09 mattmathis

One possible workaround would be to scan all web100 snaps and report the smallest non-zero value for MinRTT. Since the actual MinRTT is almost always seen at the beginning and the zero bug was caused by a bogus measurement later in the connection, most of the MinRTT measurements from the beginning of the test would be valid.

mattmathis avatar Sep 28 '20 18:09 mattmathis