Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751724Ab0BULX7 (ORCPT ); Sun, 21 Feb 2010 06:23:59 -0500 Received: from mta-1.ms.rz.RWTH-Aachen.DE ([134.130.7.72]:59237 "EHLO mta-1.ms.rz.rwth-aachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751398Ab0BULX5 (ORCPT ); Sun, 21 Feb 2010 06:23:57 -0500 MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=us-ascii X-IronPort-AV: E=Sophos;i="4.49,511,1262559600"; d="scan'208";a="45849912" Subject: Re: [net-next PATCH v4 1/3] net: TCP thin-stream detection From: Alexander Zimmermann In-reply-to: <20100221102102.GB1311@ucw.cz> Date: Sun, 21 Feb 2010 12:23:55 +0100 Cc: netdev@vger.kernel.org, Ilpo J?rvinen , Eric Dumazet , Arnd Hannemann , LKML , shemminger@vyatta.com, David Miller , william.allen.simpson@gmail.com, Lukowski Damian , "Eric W. Biederman" Message-id: References: <4B7AAE60.3070305@simula.no> <20100221102102.GB1311@ucw.cz> To: Pavel Machek , Andreas Petlund , lars.eggert@nokia.com X-Mailer: Apple Mail (2.1077) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2061 Lines: 56 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@vger.kernel.org > 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@cs.rwth-aachen.de // 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/