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Author Topic: Upstream combined performance deficit (again) - run out of ideas  (Read 114 times)


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Upstream combined performance deficit (again) - run out of ideas
« on: September 10, 2019, 02:57:13 AM »

Iíve tried to think of everything but I donít understand it. The combined upstream throughput measured by two differed speed testers is at least 250k down compared to what it should be. Iím getting speed tester upstream combined results of 1.25Mbps - 1.3Mbps instead of an earlier 1.56 Mbps (guessing that means TCP payload). Iíve allowed for TCP headersí overheads in those expectations and in any case this is comparing speed tester results with others from the same tester earlier when things were good.

Some while back, when this happened before, I put it down to packet corruption causing drops and TCP retx. There was evidence of errors in the DSL stats relating to one line, line 3 iirc. Curing the errors fixed the combined performance so that gave support to the theory. So I need to look for bad stats again.

Perhaps I also need to look at the wrong direction. Look for errors in downstream, not in upstream, in case downstream TCP ACKs are getting dropped due to corruption. Perhaps I am stupid to think about looking at upstream?

If not that, then what? Just unfortunate packet recording which upsets TCP ? And doesnít give a good combination of aggregate speeds?

I can see 54 ES per day on line 1 upstream, 37 on line 2, 11 on line 3 and 7 on line 4  - any of those enough?

*The speed testers were and the upload test at and both were consistent. The former is better for me in theory because it is close, being at my ISP, whilst the latter is convenient because it allows an upload-only test and the size of the test transmission is controllable.

See also attached PDF of spreadsheet with test results over recent months.
« Last Edit: September 10, 2019, 04:27:23 AM by Weaver »