Re: Review of draft-ietf-6man-rfc4291bis-06

Fernando Gont <fgont@si6networks.com> Fri, 13 January 2017 19:44 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 1AABC129DA2; Fri, 13 Jan 2017 11:44:56 -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, 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 orO-SYn_Pxtq; Fri, 13 Jan 2017 11:44:53 -0800 (PST)
Received: from fgont.go6lab.si (fgont.go6lab.si [IPv6:2001:67c:27e4::14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 7E218129DA0; Fri, 13 Jan 2017 11:44:53 -0800 (PST)
Received: from [192.168.3.95] (142-135-17-190.fibertel.com.ar [190.17.135.142]) (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 C981B82997; Fri, 13 Jan 2017 20:44:44 +0100 (CET)
Subject: Re: Review of draft-ietf-6man-rfc4291bis-06
To: Brian E Carpenter <brian.e.carpenter@gmail.com>, Randy Bush <randy@psg.com>
References: <148406593094.22166.2894840062954191477.idtracker@ietfa.amsl.com> <m2fukqbbwv.wl-randy@psg.com> <F6953234-3F85-4E28-9861-433ADD01A490@gmail.com> <m2wpdzhncn.wl-randy@psg.com> <82245ef2-cd34-9bd6-c04e-f262e285f983@gmail.com> <m2d1frhjfn.wl-randy@psg.com> <18e6e13c-e605-48ff-4906-2d5531624d64@gmail.com>
From: Fernando Gont <fgont@si6networks.com>
X-Enigmail-Draft-Status: N1110
Message-ID: <513edeeb-1713-13c5-3e44-97d79f19da6f@si6networks.com>
Date: Fri, 13 Jan 2017 16:44:23 -0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1
MIME-Version: 1.0
In-Reply-To: <18e6e13c-e605-48ff-4906-2d5531624d64@gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/ipv6/qH99IxiZxs2vZmdom0aYJH2w9as>
Cc: Bob Hinden <bob.hinden@gmail.com>, IETF <ietf@ietf.org>, IPv6 List <ipv6@ietf.org>, draft-ietf-6man-rfc4291bis.all@ietf.org, int-dir@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: Fri, 13 Jan 2017 19:44:56 -0000

On 01/12/2017 10:55 PM, Brian E Carpenter wrote:
> On 13/01/2017 13:50, Randy Bush wrote:
>>> RFC7421 (which is Informational) calls out RFC 6164 (not 6141!) as an exception.
>>> To be precise it says:
>>>
>>>    The de facto length of almost all IPv6 interface identifiers is
>>>    therefore 64 bits.  The only documented exception is in [RFC6164],
>>>    which standardizes 127-bit prefixes for point-to-point links between
>>>    routers, among other things, to avoid a loop condition known as the
>>>    ping-pong problem.
>>>
>>> I would suggest adding a similar exception statement in 4291bis.
>>
>> and then next year we will go through another draft and have another
>> exception.  just get rid of classful addressing.  we went through this
>> in the '90s.
> 
> The problem is (and why we wrote 7421) is that stuff breaks with subnet
> prefixes longer than 64, *except* for the point-to-point case covered
> by 6164. Yes, I see the problem in enshrining this but I think we face
> signifcant issues if we do otherwise.
> 
> What we could conceivably say is that /64 is mandatory except for
> links where SLAAC will never be used. (SLAAC itself is designed
> to work with any reasonable length of IID, but again in practice it
> only works with /64, because we need mix-and-match capability. So
> although IID length is a parameter in the SLAAC design, it's a
> parameter whose value needs to be fixed globally.)

Well, yes and no. With the traditional slaac (embed the mac address) it
only works with 64-bit IIDs. With something like RFC7217 (grab as many
bits as needed to for an IID), it could work.

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