Re: Objection to draft-ietf-6man-rfc4291bis-07.txt

Fernando Gont <fgont@si6networks.com> Tue, 28 February 2017 20:36 UTC

Return-Path: <fgont@si6networks.com>
X-Original-To: ipv6@ietfa.amsl.com
Delivered-To: ipv6@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 459FE1296E1 for <ipv6@ietfa.amsl.com>; Tue, 28 Feb 2017 12:36:17 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.901
X-Spam-Level:
X-Spam-Status: No, score=-1.901 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id raAv6-IDofAU for <ipv6@ietfa.amsl.com>; Tue, 28 Feb 2017 12:36:15 -0800 (PST)
Received: from fgont.go6lab.si (fgont.go6lab.si [91.239.96.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 7781C1296E0 for <ipv6@ietf.org>; Tue, 28 Feb 2017 12:36:15 -0800 (PST)
Received: from [192.168.3.83] (unknown [181.165.116.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by fgont.go6lab.si (Postfix) with ESMTPSA id 9A7A580634; Tue, 28 Feb 2017 21:36:11 +0100 (CET)
Subject: Re: Objection to draft-ietf-6man-rfc4291bis-07.txt
To: Brian E Carpenter <brian.e.carpenter@gmail.com>, Lorenzo Colitti <lorenzo@google.com>, David Farmer <farmer@umn.edu>
References: <20170223134026.GI5069@gir.theapt.org> <9277BC0B-04F3-4FC1-901E-F83A8F0E02D7@google.com> <58AF6429.70809@foobar.org> <902276E9-0521-4D4E-A42B-C45E64763896@google.com> <58AF726A.3040302@foobar.org> <F7C230DE-4759-4B78-ABF2-6799F85B3C62@google.com> <58B014F6.2040400@foobar.org> <6DA95097-8730-4353-A0C9-3EB4719EA891@google.com> <CAKD1Yr0qk_njAGnex_FZsYisCVw=eM8hXTr1v+wqvcfX_09wiQ@mail.gmail.com> <CAN-Dau0ohz3Wp55bs+eoFvSyoUjuKfjzKGSAsJS3wUt3z7TGtA@mail.gmail.com> <CAKD1Yr0wK8EiAbz39EZz-xZLtsSV2JROSzNECKtGo36Zc=RZ0Q@mail.gmail.com> <3fba77e0-d7ff-802e-019b-6fe152eaee67@gmail.com>
From: Fernando Gont <fgont@si6networks.com>
X-Enigmail-Draft-Status: N1110
Message-ID: <3c1a2749-a6e5-01ae-bdd0-0bd7b8c50bc9@si6networks.com>
Date: Tue, 28 Feb 2017 17:36:03 -0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0
MIME-Version: 1.0
In-Reply-To: <3fba77e0-d7ff-802e-019b-6fe152eaee67@gmail.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/ipv6/Z9KLjfOLSrA0JKvE5TLRrIUC8E0>
Cc: james woodyatt <jhw@google.com>, 6man WG <ipv6@ietf.org>
X-BeenThere: ipv6@ietf.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: "IPv6 Maintenance Working Group \(6man\)" <ipv6.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ipv6>, <mailto:ipv6-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/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: Tue, 28 Feb 2017 20:36:17 -0000

On 02/28/2017 04:56 PM, Brian E Carpenter wrote:
> On 01/03/2017 05:29, Lorenzo Colitti wrote:
> ...
>>> We have defined this as a parameter not as a constant.
>>>
>>
>> I really don't understand this statement. How can you say that it's a
>> parameter, given that every RFC that has been published on this topic
>> starting from 1998 states that (most) IIDs are 64 bits long?
> 
> Yes, I think we have a long tradition of expressing this badly, and now
> is a chance to get it right. It's clear at the point where it's
> introduced in RFC4291 that it's a floating boundary:
> 
>   "A slightly sophisticated host (but still rather simple) may
>    additionally be aware of subnet prefix(es) for the link(s) it is
>    attached to, where different addresses may have different values for
>    n:
> 
>    |          n bits               |           128-n bits            |
>    +-------------------------------+---------------------------------+
>    |       subnet prefix           |           interface ID          |
>    +-------------------------------+---------------------------------+"
> 
> but later in the same document we state that (128-n) == 64. That is
> inconsistent; what we're trying to do now is fix that inconsistency
> in a way that is *also* consistent with running code, SLAAC, and the
> newly important privacy issues that require long, unpredictable IIDs.

I agree with Brian's comment. We need to get this fixed.

Regarding long IIDs:
* when it comes to privacy, either long or very short will generally do
-- with long, you can produce good unpredictable IIDs. With short IIDs,
you almost guarantee collisions of IIDs, hence the IIDs are meaningless
to track nodes (as in IPv4).

* From a network scanning et al, long IIDs are obviously desirable.
But.. /64 would do in the same way that something > 50 bits would
probably do.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492