Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753515Ab0BUWg5 (ORCPT ); Sun, 21 Feb 2010 17:36:57 -0500 Received: from courier.cs.helsinki.fi ([128.214.9.1]:56672 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752039Ab0BUWgz (ORCPT ); Sun, 21 Feb 2010 17:36:55 -0500 Date: Mon, 22 Feb 2010 00:36:54 +0200 (EET) From: "=?ISO-8859-15?Q?Ilpo_J=E4rvinen?=" X-X-Sender: ijjarvin@melkinpaasi.cs.helsinki.fi To: Alexander Zimmermann cc: Pavel Machek , Andreas Petlund , lars.eggert@nokia.com, Netdev , Eric Dumazet , Arnd Hannemann , LKML , shemminger@vyatta.com, David Miller , william.allen.simpson@gmail.com, Lukowski Damian , "Eric W. Biederman" Subject: Re: [net-next PATCH v4 1/3] net: TCP thin-stream detection In-Reply-To: Message-ID: References: <4B7AAE60.3070305@simula.no> <20100221102102.GB1311@ucw.cz> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1617 Lines: 39 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/