IETF Logo Mail Archive

RE: Pseudorandom Flow Labels

"Hemant Singh (shemant)" <shemant@cisco.com> Wed, 06 April 2011 01:33 UTC

Return-Path: <shemant@cisco.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 CA3F73A69A9 for <ipv6@core3.amsl.com>; Tue, 5 Apr 2011 18:33:16 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -10.625
X-Spam-Level:
X-Spam-Status: No, score=-10.625 tagged_above=-999 required=5 tests=[AWL=-0.026, BAYES_00=-2.599, RCVD_IN_DNSWL_HI=-8]
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 26EGry8-QduD for <ipv6@core3.amsl.com>; Tue, 5 Apr 2011 18:33:15 -0700 (PDT)
Received: from sj-iport-1.cisco.com (sj-iport-1.cisco.com [171.71.176.70]) by core3.amsl.com (Postfix) with ESMTP id D8C5D3A69A7 for <ipv6@ietf.org>; Tue, 5 Apr 2011 18:33:15 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=shemant@cisco.com; l=1331; q=dns/txt; s=iport; t=1302053699; x=1303263299; h=mime-version:content-transfer-encoding:subject:date: message-id:in-reply-to:references:from:to:cc; bh=6TEm1XXEfd9Z6LT5zq6CyW1wWZXn8PFbjB4kZj8vWTA=; b=ib1bmsw4bjd1jPsGXyzgQVLeZKDQB/h8C++jMVww3rOzpH1BFLa4fPB7 6/suXMoD6O5Jaf1WPTGOi72K0OoFNq1zKIeILbBXZit5BsP+28gxQC3hZ fYG1axgICkFvW5/GWvzh42rMwJw//R1ZDtc6kai3B+wT1KjuBMwedEpxo c=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AhkBAKLCm02tJXG+/2dsb2JhbACYLI1Id6YhnDGFbASFR4s/
X-IronPort-AV: E=Sophos;i="4.63,307,1299456000"; d="scan'208";a="424535978"
Received: from rcdn-core2-3.cisco.com ([173.37.113.190]) by sj-iport-1.cisco.com with ESMTP; 06 Apr 2011 01:34:59 +0000
Received: from xbh-rcd-301.cisco.com (xbh-rcd-301.cisco.com [72.163.63.8]) by rcdn-core2-3.cisco.com (8.14.3/8.14.3) with ESMTP id p361YwwV005125; Wed, 6 Apr 2011 01:34:59 GMT
Received: from xmb-rcd-109.cisco.com ([72.163.62.151]) by xbh-rcd-301.cisco.com with Microsoft SMTPSVC(6.0.3790.4675); Tue, 5 Apr 2011 20:34:58 -0500
X-MimeOLE: Produced By Microsoft Exchange V6.5
x-cr-hashedpuzzle: Af4j DoXm Dz7A KHW2 MGgZ OfYp P2Ir UK+K Vomj WwzW W5Rb XjiP YpOI ZFUD ZH7c Z0M8; 3; aQBwAHYANgBAAGkAZQB0AGYALgBvAHIAZwA7AGoAaAB3AEAAYQBwAHAAbABlAC4AYwBvAG0AOwBuAGEAcgB0AGUAbgBAAHUAcwAuAGkAYgBtAC4AYwBvAG0A; Sosha1_v1; 7; {DEA874CB-172B-4D41-99C3-08449837DDCE}; cwBoAGUAbQBhAG4AdABAAGMAaQBzAGMAbwAuAGMAbwBtAA==; Wed, 06 Apr 2011 01:34:53 GMT; UgBFADoAIABQAHMAZQB1AGQAbwByAGEAbgBkAG8AbQAgAEYAbABvAHcAIABMAGEAYgBlAGwAcwA=
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
x-cr-puzzleid: {DEA874CB-172B-4D41-99C3-08449837DDCE}
Content-class: urn:content-classes:message
Subject: RE: Pseudorandom Flow Labels
Date: Tue, 05 Apr 2011 20:34:53 -0500
Message-ID: <5B6B2B64C9FE2A489045EEEADDAFF2C301391466@XMB-RCD-109.cisco.com>
In-Reply-To: <201104060008.p3608OlC022133@cichlid.raleigh.ibm.com>
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
Thread-Topic: Pseudorandom Flow Labels
Thread-Index: Acvz7s7pyTFFmQOPRvu1/IvWT9Er5AACos2A
References: <BD901061-96AC-4915-B7CE-2BC1F70861A5@castlepoint.net><201104052036.p35KaoHV019253@cichlid.raleigh.ibm.com><19204E85-5B6E-409C-B450-7E3AC5EF47FA@apple.com><201104052148.p35LmM9g019765@cichlid.raleigh.ibm.com><9ED6022F-6863-4267-A268-C73240098539@apple.com> <201104060008.p3608OlC022133@cichlid.raleigh.ibm.com>
From: "Hemant Singh (shemant)" <shemant@cisco.com>
To: Thomas Narten <narten@us.ibm.com>, james woodyatt <jhw@apple.com>
X-OriginalArrivalTime: 06 Apr 2011 01:34:58.0810 (UTC) FILETIME=[D73465A0:01CBF3FA]
Cc: 6MAN Working Group <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 01:33:17 -0000

-----Original Message-----
From: ipv6-bounces@ietf.org [mailto:ipv6-bounces@ietf.org] On Behalf Of
Thomas Narten
Sent: Tuesday, April 05, 2011 8:08 PM
To: james woodyatt
Cc: 6MAN Working Group
Subject: Re: Pseudorandom Flow Labels


>What is *required* is that the hash function (or whatever function
>that is used) on the router maps the tuples in a *uniform* way across
>the range of possible outputs.

>If you have 10 links, and all your Flow Labels are clustered around
>low ten values, but in an approximately uniform way, a simple modulo
>hash will get you the kind of distribution you need.

>The range of values of the flow label itself does not need to be
>uniformly distributed.

>That is why incrementing a counter for each new flow provides adequate
>properties. I remain unconvinced that we need to require that they
>exhibit pseudo randomness, or even be uniform.

>If that is a requirement, I'd like to see the justification, not just
>hand waiving.

How about something like the text below:

A property of the flow label is that when the flow label is used a key
to a hash function the function produces a uniform distribution of hash
values.  Thus, incrementing a counter for each new flow is one means to
achieve the property described in the previous sentence. 

Hemant

v2.23.0 | Report a Bug | By Email