Re: [Autoconf] Using DHCPv6 without link-local? Support only EUI-64 interfaces?

Alexandru Petrescu <alexandru.petrescu@gmail.com> Mon, 02 August 2010 12:29 UTC

Return-Path: <alexandru.petrescu@gmail.com>
X-Original-To: autoconf@core3.amsl.com
Delivered-To: autoconf@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id 948043A69FB for <autoconf@core3.amsl.com>; Mon, 2 Aug 2010 05:29:12 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.154
X-Spam-Level:
X-Spam-Status: No, score=-2.154 tagged_above=-999 required=5 tests=[AWL=0.095, BAYES_00=-2.599, HELO_EQ_FR=0.35]
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 5+7KZrtPBZ1m for <autoconf@core3.amsl.com>; Mon, 2 Aug 2010 05:29:11 -0700 (PDT)
Received: from sainfoin-out.extra.cea.fr (sainfoin-out.extra.cea.fr [132.166.172.107]) by core3.amsl.com (Postfix) with ESMTP id 76FB83A687D for <autoconf@ietf.org>; Mon, 2 Aug 2010 05:29:11 -0700 (PDT)
Received: from pisaure.intra.cea.fr (pisaure.intra.cea.fr [132.166.88.21]) by sainfoin.extra.cea.fr (8.14.2/8.14.2/CEAnet-Internet-out-2.0) with ESMTP id o72CTcST032689 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Mon, 2 Aug 2010 14:29:38 +0200
Received: from muguet2.intra.cea.fr (muguet2.intra.cea.fr [132.166.192.7]) by pisaure.intra.cea.fr (8.14.4/8.14.4) with ESMTP id o72CTbeZ015455; Mon, 2 Aug 2010 14:29:38 +0200 (envelope-from alexandru.petrescu@gmail.com)
Received: from [127.0.0.1] ([132.166.133.173]) by muguet2.intra.cea.fr (8.13.8/8.13.8/CEAnet-Intranet-out-1.1) with ESMTP id o72CTbaZ009348; Mon, 2 Aug 2010 14:29:37 +0200
Message-ID: <4C56BA31.6040203@gmail.com>
Date: Mon, 02 Aug 2010 14:29:37 +0200
From: Alexandru Petrescu <alexandru.petrescu@gmail.com>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.9.2.7) Gecko/20100713 Thunderbird/3.1.1
MIME-Version: 1.0
To: Teco Boot <teco@inf-net.nl>
References: <EBE1B970-DADA-4643-BB75-4EDEDE41F758@inf-net.nl> <4C568726.1020307@gmail.com> <26410CAF-6B3A-4AAF-B194-1C1F989F4E27@inf-net.nl>
In-Reply-To: <26410CAF-6B3A-4AAF-B194-1C1F989F4E27@inf-net.nl>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Cc: "autoconf@ietf.org autoconf@ietf.org" <autoconf@ietf.org>
Subject: Re: [Autoconf] Using DHCPv6 without link-local? Support only EUI-64 interfaces?
X-BeenThere: autoconf@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: Ad-Hoc Network Autoconfiguration WG discussion list <autoconf.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/autoconf>, <mailto:autoconf-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/autoconf>
List-Post: <mailto:autoconf@ietf.org>
List-Help: <mailto:autoconf-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/autoconf>, <mailto:autoconf-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 02 Aug 2010 12:29:12 -0000

Le 02/08/2010 14:07, Teco Boot a écrit :
> Op 2 aug 2010, om 10:51 heeft Alexandru Petrescu het volgende
> geschreven:
>
>> I was thinking about the same thing as you say: if RFC5889 forbids
>> link local addresses and new Charter wants DHCP then how could both
>> work?
>
> The document doesn't say "forbid".

Right, RFC5889-to-be does not say "forbid".

5889-to-be:
> Note that while link-local addresses are assumed to be "on link",
> the utility of link-local addresses is limited as described in
> Section 6.

Ok, DHCPv6 could leave with this, thinking that the utility of 
link-local addresses is only  during the initial DHCP exchanges 
(Solicit-Advertise I believe).

5889-to-be (without WG discussion Maastricht):
>    Note that while an IPv6 link-local address is assigned to each
>    interface as per [RFC4291], in general link-local addresses are of
>    limited utility on links with undetermined connectivity, as
>    connectivity to neighbors may be constantly changing.  The known
>    limitations are:
>
>    o  There is no mechanism to ensure that IPv6 link-local addresses are
>       unique across multiple links, hence they cannot be used to
>       reliably identify routers (it is often desirable to identify a
>       router with an IP address).
>
>    o  Routers cannot forward any packets with link-local source or
>       destination addresses to other links (as per [RFC4291]), while
>       most of the time, routers need to be able to forward packets to/
>       from different links.

Although DHCP Relay sits on a router, DHCP is not "most of the time" in 
that a DHCP Relay will use its global address although the Client sent a 
Solicit using its link-local address - Relay duplicates the packet.

>    Therefore, autoconfiguration solutions should be encouraged to
>    primarily focus on configuring IP addresses that are not IPv6 link-
>    local.

This is fine, because DHCP would configure an IP address on Client which 
is not link-local but global.

Of course this DHCPv6-LL analysis should change when we get the more 
final RFC5889-to-be text.

Alex