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SubjectRe: [net-next PATCH v4 1/3] net: TCP thin-stream detection
On Sun, 21 Feb 2010, Alexander Zimmermann wrote:

>
> Am 21.02.2010 um 11:21 schrieb Pavel Machek:
>
> > Hi!
> >
> >> +After analysing a large number of time-dependent interactive
> >> +applications, we have seen that they often produce thin streams
> >> +and also stay with this traffic pattern throughout its entire
> >> +lifespan. The combination of time-dependency and the fact that the
> >> +streams provoke high latencies when using TCP is unfortunate.
> >> +
> >> +In order to reduce application-layer latency when packets are lost,
> >> +a set of mechanisms has been made, which address these latency issues
> >> +for thin streams. In short, if the kernel detects a thin stream,
> >> +the retransmission mechanisms are modified in the following manner:
> >> +
> >> +1) If the stream is thin, fast retransmit on the first dupACK.
> >> +2) If the stream is thin, do not apply exponential backoff.
> >
> > 2) seems very dangerous/unfair. If network congestion is caused just
> > by thin streams, will the network just fall apart?
>
> and 1) can also be dangerous if we have reordering on the path.
>
> I strongly suggest that we discuss Andreas' idea on IETF TCPM *before*
> we integrate it in the kernel and enable it for everyone

What difference you see with 1) and early rexmit when cwnd = 2, the latter
being afaict "discussed already" on TCPM?

--
i.


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