Date: Sun, 21 Feb 2010 11:21:03 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Andreas Petlund <apetlund@simula.no>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
       Ilpo J?rvinen <ilpo.jarvinen@helsinki.fi>,
       Eric Dumazet <eric.dumazet@gmail.com>,
       Arnd Hannemann <hannemann@nets.rwth-aachen.de>,
       LKML <linux-kernel@vger.kernel.org>, shemminger@vyatta.com,
       David Miller <davem@davemloft.net>, william.allen.simpson@gmail.com,
       damian@tvk.rwth-aachen.de, "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [net-next PATCH v4 1/3] net: TCP thin-stream detection
Message-ID: <20100221102102.GB1311@ucw.cz>
References: <4B7AAE60.3070305@simula.no>
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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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