Re: [tcpm] taking RFC 2861 (Congestion Window Validation) to Proposed Standard?

>> I understand that bursty applications would often rather not reduce
>> cwnd after an idle or application-limited periiod.  (It *might* be
>> in their own interests, if it helps the flow to avoid unnecessary
>> packet drops, but it *might not* be in their own interests, e.g.,
>> if that flow doesn't receive any packet drops when bursting after
>> an idle period.
>> But the following question also matters:
>> (1) What about when there are N possibly-bursty flows sharing the
>> same congested link?  Are there any reports about whether the *N
>> flows* do better when all flows use CWV, or whether they do better
>> when none of them use CWV, and none of them reduce cwnd after an
>> idle period?
>> (If there is no congestion, I would expect that the N flows do
>> better without CWV.   If there *is* congestion, I would expect that
>> the N flows in general do better *with* CWV, as opposed to not
>> reducing cwnd after idle periods.  But it is not something that one
>> could tell from reports from individual users...)
>
>
> This agrees with my intuition, for what it's worth. :)  I'm not aware 
> of any experiments along these lines.  I'm also really interested in 
> how much difference pacing out bursts after an idle period might make.

Many thanks.

I assume that pacing would be a big win, with or without Congestion
Window Validation.  (With CWV, the window is not set right away to
the initial window, but is halved each RTO.)

RFC 2861 also has a paragraph at the end of Section 2 arguing that
pacing by itself would not be sufficient, without *some* reduction
of cwnd after a long idle period.  (Would one really want connections
with a cwnd of 1000 packets or more to start up with that cwnd after
an idle period of an hour?  With or pacing?  Even though there very
well *might* not be any congestion after the hour-long idle period?)

- Sally
http://www.icir.org/floyd/

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