From owner-freebsd-net@FreeBSD.ORG Sat Jul 21 08:04:29 2007 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5C5C316A418 for ; Sat, 21 Jul 2007 08:04:29 +0000 (UTC) (envelope-from artem@aws-net.org.ua) Received: from alf.aws-net.org.ua (alf.aws-net.org.ua [85.90.196.192]) by mx1.freebsd.org (Postfix) with ESMTP id A907D13C459 for ; Sat, 21 Jul 2007 08:04:26 +0000 (UTC) (envelope-from artem@aws-net.org.ua) Received: from [192.168.32.4] (aviko.aws-net.org.ua [192.168.32.4]) by alf.aws-net.org.ua (8.13.8/8.13.8) with ESMTP id l6L83gs0063517 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Sat, 21 Jul 2007 11:03:47 +0300 (EEST) (envelope-from artem@aws-net.org.ua) Message-ID: <46A1BDDE.5080403@aws-net.org.ua> Date: Sat, 21 Jul 2007 11:03:42 +0300 From: Artyom Viklenko Organization: Art&Co. User-Agent: Thunderbird 2.0.0.5 (Windows/20070716) MIME-Version: 1.0 To: Artem Belevich References: <200707150237.l6F2bAgZ011098@redrock.karels.net> <469E0FFF.8070802@seclark.us> <20070720172021.8EA3D13C4B3@mx1.freebsd.org> <46A10063.9010902@elischer.org> <46A10860.50804@es.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded STARTTLS authentication, not delayed by milter-greylist-3.0 (alf.aws-net.org.ua [192.168.32.253]); Sat, 21 Jul 2007 11:03:52 +0300 (EEST) X-Virus-Scanned: ClamAV version 0.90.3, clamav-milter version 0.90.3 on localhost X-Virus-Status: Clean Cc: freebsd-net@freebsd.org, Julian Elischer Subject: Re: 6.2 mtu now limits size of incomming packet X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 21 Jul 2007 08:04:29 -0000 Artem Belevich wrote: > Here's one example where MTU!=MRU would be useful. > > Think of asymmetric bandwith-limited ADSL links. Lower MTU would allow > lower TX latency for high priority packets when upstream is saturated, > yet large MRU on the downstream would be great for downloads. > > Right now with 6.2 one has to trade off lower latency for faster download. > > --Artem You can prioritize small packets with ACKs, for example, by other techniques - ALTQ one of them. Unconditional lovering MTU even on ADSL tend to loss throughtput. And let's think about TCP MSS. When TCP connection establishes, TCP stack uses MTU as measure to choose MSS. Any two hosts, connected to single Layer2 network MUST use same MTU. Any other cases lead to hard-to-solve problems. This is all IMHO. But I would not like to see different MTU and MRU on my Ethernet interfaces! :) -- Sincerely yours, Artyom Viklenko. ------------------------------------------------------- artem@aws-net.org.ua | http://www.aws-net.org.ua/~artem FreeBSD: The Power to Serve - http://www.freebsd.org