Re: Pseudorandom Flow Labels

Fernando Gont <fernando@gont.com.ar> Wed, 06 April 2011 17:34 UTC

Return-Path: <fernando.gont.netbook.win@gmail.com>
X-Original-To: ipv6@core3.amsl.com
Delivered-To: ipv6@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id 914E43A68EA for <ipv6@core3.amsl.com>; Wed, 6 Apr 2011 10:34:10 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -3.599
X-Spam-Level:
X-Spam-Status: No, score=-3.599 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, RCVD_IN_DNSWL_LOW=-1]
Received: from mail.ietf.org ([64.170.98.32]) by localhost (core3.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 3MUx7d3GYej6 for <ipv6@core3.amsl.com>; Wed, 6 Apr 2011 10:34:09 -0700 (PDT)
Received: from mail-gx0-f172.google.com (mail-gx0-f172.google.com [209.85.161.172]) by core3.amsl.com (Postfix) with ESMTP id 9E06B3A68CE for <ipv6@ietf.org>; Wed, 6 Apr 2011 10:34:09 -0700 (PDT)
Received: by gxk19 with SMTP id 19so789131gxk.31 for <ipv6@ietf.org>; Wed, 06 Apr 2011 10:35:53 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:sender:message-id:date:from:user-agent :mime-version:to:cc:subject:references:in-reply-to :x-enigmail-version:openpgp:content-type:content-transfer-encoding; bh=mC//GIHVdKHtis3s8Ikgx00J3j3G4tvmMon6wGrfj6k=; b=oZvaC7vMTIMWKGwbE8IDCq4+nCKIjGySc2PL5xvP6qOCp4qmZenRUZgIgOh2ZD/df3 GlcsvcSiVpIIa/EMBya/u4m051KUtoppLEcAN/2Klkqv73Vcw/X2DXcyD5e2yQuF4Ida Ei5n1e0HKUVcruSZ/huUPpsYuEv2I4Yo71UOw=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:openpgp:content-type :content-transfer-encoding; b=Mn3ViHzmW3qlrPvSHP6tHiU7ApaHg7q/VD4nG8yA3STV/wzHP91gNypgKT2jiuW58r 4gBy84bIY9DtrOUrGymGlrM9Us1A3pTgnFGs5L6lRQgqsadhQw4QYM+yPTOXlaA/eadF UQjnes6//MLDfmHiRcXN5iI9AZVzz9rGNyt40=
Received: by 10.101.174.3 with SMTP id b3mr957577anp.114.1302111353396; Wed, 06 Apr 2011 10:35:53 -0700 (PDT)
Received: from [192.168.123.101] ([190.48.201.131]) by mx.google.com with ESMTPS id e24sm880572ana.28.2011.04.06.10.35.44 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 06 Apr 2011 10:35:52 -0700 (PDT)
Sender: Fernando Gont <fernando.gont.netbook.win@gmail.com>
Message-ID: <4D9CA46C.6040404@gont.com.ar>
Date: Wed, 06 Apr 2011 14:35:40 -0300
From: Fernando Gont <fernando@gont.com.ar>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.8) Gecko/20100802 Thunderbird/3.1.2
MIME-Version: 1.0
To: Shane Amante <shane@castlepoint.net>
Subject: Re: Pseudorandom Flow Labels
References: <BD901061-96AC-4915-B7CE-2BC1F70861A5@castlepoint.net>
In-Reply-To: <BD901061-96AC-4915-B7CE-2BC1F70861A5@castlepoint.net>
X-Enigmail-Version: 1.1.1
OpenPGP: id=D076FFF1
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: Thomas Narten <narten@us.ibm.com>, 6man List <ipv6@ietf.org>
X-BeenThere: ipv6@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: "IPv6 Maintenance Working Group \(6man\)" <ipv6.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/ipv6>, <mailto:ipv6-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/ipv6>
List-Post: <mailto:ipv6@ietf.org>
List-Help: <mailto:ipv6-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ipv6>, <mailto:ipv6-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 06 Apr 2011 17:34:10 -0000

Hi, Shane,

On 05/04/2011 04:22 p.m., Shane Amante wrote:
> With respect to your comments on, both at the mic at the 6MAN WG and
> on the list: draft-ietf-6man-flow-3697bis-02 
> draft-ietf-6man-flow-ecmp-01 draft-ietf-6man-flow-update-04
> 
> You seem to take issue with a recommendation for creating/selecting a
> flow-label that is "pseudo-random".  Can you clarify the reason(s)
> you take issue with creating/selecting a flow-label that is
> "pseudo-random"?  (IMO, the current 'SHOULD' in the draft provides
> enough leeway that if implementations have good reason(s) to not
> select pseudo-random values for flow-labels they can choose to do so,
> but would hopefully have good reasons for that).
> 
> The reason I ask is as follows: 1)  RFC 6056: Recommendations for
> Transport Protocol Randomization, in particular Appendix A.  In
> short, a lot of [deployed] implementations are already computing a
> pseudo-random value for a transport protocol port (within the
> ephemeral port range), today, so IMHO the implementation "burden" of
> choosing a pseudo-random value must be quite low and, in theory,
> there should be good re-use of that code/logic for selecting
> flow-labels. 

And even if they had to implement this support "from scratch", the code
would be very small -- see e.g. the recent patch for port randomization
that was posted to freebsd-net.



> 2)  If we expect that if a intermediate router or switch
> is using *just* the 3-tuple of {src_ip, dst_ip + flow_label} as
> input-keys to compute a load-balancing hash algorithm, then the more
[...]

+1 for pseudo-random Flow Labels :-)

Thanks,
-- 
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@acm.org
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1