apetlund@simula.no a écrit :

quoted

Andreas Petlund a écrit :

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There should be a limit to linear timeouts, to say ... no more than 6

retransmits

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(eventually tunable), then switch to exponential backoff. Maybe your

patch

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already implement such heuristic ?

The limitation you suggest to the linear timeouts makes very good sense.
Our experiments performed on the Internet indicate that it is extremely
rare that more than 6 retransmissions are needed to recover. It is not
included in the current patch, so I will include this in the next
iteration.

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True link collapses do happen, it would be good if not all streams

wakeup

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in the same
second and make recovery very slow.

Each stream will have its own schedule for wakeup, so such events will
still be subject to coincidence. The timer granularity of the TCP wakeup
timer will also influence how many streams will wake at the same time. The
experiments we have performed on severely congested bottlenecks (link
above) indicate that the modifications will not create a large negative
effect. In fact, when goodput is drastically reduced due to severe
overload, regular TCP and the LT and dupACK modifications seem to perform
nearly identically. Other scenarios may exist where different effects can
be observed, and I am open to suggestions for further testing.

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Thats too easy to accept possibly dangerous features with the excuse of

saying

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"It wont be used very much", because you cannot predict the future.

I agree that it is no argument to say that it won't be used much; indeed,
my hope is that it will be used much. However, our experiments indicate no
negative effects while showing a large improvement on retransmission
latency for the scenario in question. I therefore think that the option
for such an improvement should be made available for time-dependent
thin-stream applications.

Thanks ! I must say I am very interested by these experiments, I am looking
forward your next iteration.