Re: interop problems with getaddrinfo() address selection

Tony Finch <dot@dotat.at> Fri, 07 December 2007 17:46 UTC

Return-path: <discuss-bounces@apps.ietf.org>
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1J0hH6-0003Gb-Qs; Fri, 07 Dec 2007 12:46:08 -0500
Received: from discuss by megatron.ietf.org with local (Exim 4.43) id 1J0hH6-0003GS-3i for discuss-confirm+ok@megatron.ietf.org; Fri, 07 Dec 2007 12:46:08 -0500
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1J0hH5-0003GK-QW for discuss@apps.ietf.org; Fri, 07 Dec 2007 12:46:07 -0500
Received: from ppsw-6.csi.cam.ac.uk ([131.111.8.136]) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1J0hH4-0005F5-Co for discuss@apps.ietf.org; Fri, 07 Dec 2007 12:46:07 -0500
X-Cam-SpamDetails: Not scanned
X-Cam-AntiVirus: No virus found
X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/
Received: from hermes-1.csi.cam.ac.uk ([131.111.8.51]:49231) by ppsw-6.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.156]:25) with esmtpa (EXTERNAL:fanf2) id 1J0hGz-0005bZ-MW (Exim 4.67) (return-path <fanf2@hermes.cam.ac.uk>); Fri, 07 Dec 2007 17:46:01 +0000
Received: from fanf2 (helo=localhost) by hermes-1.csi.cam.ac.uk (hermes.cam.ac.uk) with local-esmtp id 1J0hGz-0005mj-VE (Exim 4.67) (return-path <fanf2@hermes.cam.ac.uk>); Fri, 07 Dec 2007 17:46:01 +0000
Date: Fri, 07 Dec 2007 17:46:01 +0000
From: Tony Finch <dot@dotat.at>
X-X-Sender: fanf2@hermes-1.csi.cam.ac.uk
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
Subject: Re: interop problems with getaddrinfo() address selection
In-Reply-To: <200712062020.PAA16213@Sparkle.Rodents.Montreal.QC.CA>
Message-ID: <Pine.LNX.4.64.0712071735070.24448@hermes-1.csi.cam.ac.uk>
References: <Pine.LNX.4.64.0712061901020.24448@hermes-1.csi.cam.ac.uk> <200712062020.PAA16213@Sparkle.Rodents.Montreal.QC.CA>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset="US-ASCII"
X-Spam-Score: -4.0 (----)
X-Scan-Signature: d6b246023072368de71562c0ab503126
Cc: discuss@apps.ietf.org
X-BeenThere: discuss@apps.ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: general discussion of application-layer protocols <discuss.apps.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/discuss>, <mailto:discuss-request@apps.ietf.org?subject=unsubscribe>
List-Post: <mailto:discuss@apps.ietf.org>
List-Help: <mailto:discuss-request@apps.ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/discuss>, <mailto:discuss-request@apps.ietf.org?subject=subscribe>
Errors-To: discuss-bounces@apps.ietf.org

On Thu, 6 Dec 2007, der Mouse wrote:
>
> I'm interseted in what sort of problems it causes.

DNS round robin is effective at balancing load evenly across multiple
servers, because each client is (in effect) directed to one of the servers
at random. If the client sorts the DNS response before using it then the
randomization is defeated and the load on the servers is no longer
balanced.

Ian's message described the problem briefly in point 12, but I forgive you
for not reading it :-)

Tony.
-- 
f.a.n.finch  <dot@dotat.at>  http://dotat.at/
GERMAN BIGHT HUMBER THAMES DOVER: WEST OR NORTHWEST 7 TO SEVERE GALE 9,BACKING
SOUTHWEST 5 OR 6. VERY ROUGH DECREASING ROUGH. SHOWERS, RAIN LATER. GOOD
BECOMING MODERATE.