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

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Message-ID: <20100221102102.GB1311@ucw.cz>
Date:	Sun, 21 Feb 2010 11:21:03 +0100
From:	Pavel Machek <pavel@....cz>
To:	Andreas Petlund <apetlund@...ula.no>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ilpo J?rvinen <ilpo.jarvinen@...sinki.fi>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Arnd Hannemann <hannemann@...s.rwth-aachen.de>,
	LKML <linux-kernel@...r.kernel.org>, shemminger@...tta.com,
	David Miller <davem@...emloft.net>,
	william.allen.simpson@...il.com, damian@....rwth-aachen.de,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [net-next PATCH v4 1/3] net: TCP thin-stream detection

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?


-- 
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