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SubjectRe: [net-next PATCH v4 1/3] net: TCP thin-stream detection

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


as an netdev reader and TCPM member

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// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
// RWTH Aachen University
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