Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751500AbWCQJN0 (ORCPT ); Fri, 17 Mar 2006 04:13:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752577AbWCQJN0 (ORCPT ); Fri, 17 Mar 2006 04:13:26 -0500 Received: from embla.aitel.hist.no ([158.38.50.22]:42710 "HELO embla.aitel.hist.no") by vger.kernel.org with SMTP id S1751500AbWCQJN0 (ORCPT ); Fri, 17 Mar 2006 04:13:26 -0500 Message-ID: <441A7DA5.7070303@aitel.hist.no> Date: Fri, 17 Mar 2006 10:13:09 +0100 From: Helge Hafting User-Agent: Debian Thunderbird 1.0.7 (X11/20051017) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Bret Towe CC: Neil Brown , Jan Engelhardt , linux-kernel Subject: Re: nfs udp 1000/100baseT issue References: <17434.7434.626268.71114@cse.unsw.edu.au> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1627 Lines: 53 Bret Towe wrote: >On 3/16/06, Neil Brown wrote: > > >>There is no flow control in UDP >> >> > >is this a linux design flaw or just nature of udp? > > That has nothing to do with linux at all. "Now flow control in udp" is a udp design issue. And it is not a flaw either - the rule is simple: If you need flow control - use tcp. If you don't need flow control, and don't want the overhead of flow control - use udp. Udp is for those cases where flow control is consideres a waste of time. Now, the original decision to base early NFS on udp, that was a design mistake. Again, not a linux problem but a nfs problem. Fortunately, today a solution for this exists and is implemented in linux - and it is nfs over tcp. >>. If anything gets lots, the client >>has to resend the request, and the server then has to respond again. >>If the respond is large (e.g. a read) and gets fragmented (if > 1500bytes) >>then there is a good chance that one or more fragments of a reply will >>get lots in the switch stepping down from 1G to 100M. Every time. >> >>Your options include: >> >> - use tcp >> >> > >im wondering why this isnt the default to begin with > > Hard to say. I guess someone thought they could get better performance with udp - it has less overhead., Then didn't bother testing this idea with a somewhat congested network? Helge Hafting - 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/