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

[Alexander Zimmermann]

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

Alex,

as an netdev reader and TCPM member

> 
> 
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

//
// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
// RWTH Aachen University
// Ahornstr. 55, 52056 Aachen, Germany
// phone: (49-241) 80-21422, fax: (49-241) 80-22220
// email: zimmermann@xxxxxxxxxxxxxxxxx
// web: http://www.umic-mesh.net
//

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/