Re: [v6ops] I-D Action: draft-colitti-v6ops-host-addr-availability-01.txt

Alexandru Petrescu <alexandru.petrescu@gmail.com> Fri, 31 July 2015 13:10 UTC

Return-Path: <alexandru.petrescu@gmail.com>
X-Original-To: v6ops@ietfa.amsl.com
Delivered-To: v6ops@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 23AF71A6F87 for <v6ops@ietfa.amsl.com>; Fri, 31 Jul 2015 06:10:02 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.983
X-Spam-Level:
X-Spam-Status: No, score=-4.983 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_ADSP_CUSTOM_MED=0.001, FREEMAIL_FROM=0.001, HELO_EQ_FR=0.35, NML_ADSP_CUSTOM_MED=0.9, RCVD_IN_DNSWL_HI=-5, SPF_SOFTFAIL=0.665] autolearn=ham
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 ECgtzY5dJz-I for <v6ops@ietfa.amsl.com>; Fri, 31 Jul 2015 06:09:55 -0700 (PDT)
Received: from cirse-out.extra.cea.fr (cirse-out.extra.cea.fr [132.167.192.142]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id C8C381A6F04 for <v6ops@ietf.org>; Fri, 31 Jul 2015 06:09:54 -0700 (PDT)
Received: from pisaure.intra.cea.fr (pisaure.intra.cea.fr [132.166.88.21]) by cirse.extra.cea.fr (8.14.2/8.14.2/CEAnet-Internet-out-2.3) with ESMTP id t6VD9qUM015725 for <v6ops@ietf.org>; Fri, 31 Jul 2015 15:09:52 +0200
Received: from pisaure.intra.cea.fr (localhost [127.0.0.1]) by localhost (Postfix) with SMTP id B6AB82039F1 for <v6ops@ietf.org>; Fri, 31 Jul 2015 15:13:40 +0200 (CEST)
Received: from muguet1.intra.cea.fr (muguet1.intra.cea.fr [132.166.192.6]) by pisaure.intra.cea.fr (Postfix) with ESMTP id ADFE1200EA7 for <v6ops@ietf.org>; Fri, 31 Jul 2015 15:13:40 +0200 (CEST)
Received: from [127.0.0.1] (is227335.intra.cea.fr [10.8.34.184]) by muguet1.intra.cea.fr (8.13.8/8.13.8/CEAnet-Intranet-out-1.2) with ESMTP id t6VD9qjF029913 for <v6ops@ietf.org>; Fri, 31 Jul 2015 15:09:52 +0200
To: v6ops@ietf.org
References: <20150723130715.12113.47480.idtracker@ietfa.amsl.com> <m1ZJfOr-0000CgC@stereo.hq.phicoh.net> <C9C3FBC4-44F3-45D2-B8C4-3725396E5D40@nominum.com> <CAPi140Mx96dBgeaCkrsDD+-J85OZDo5Di+gHTBiaGDzYK2us4w@mail.gmail.com> <20150728115944.GZ84167@Space.Net> <CAPi140PKh64L=nr96pv3dn7FO_Y9pW162YzBT8kZHSMsedGYtQ@mail.gmail.com> <BE811683-3BBA-40F0-B047-282DA7E774AA@nominum.com> <CAKD1Yr3pHBRk+BTOJOOSC=c6M4FNaumGEKwHvFW=ThED7M744g@mail.gmail.com> <4AB2ED61-23CF-40D5-B2A6-F1F4064EC0C6@nominum.com> <CAKD1Yr3-omr_M7pU9TgoECGnTGf-ta64UcE8ddbAom-rB8exZA@mail.gmail.com> <90E6B48E-B3FC-4AAD-B356-7D92A2777632@nominum.com> <m1ZK99A-0000DCC@stereo.hq.phicoh.net> <804F2F0B-B0EF-4054-99C5-C0CD8957C434@nominum.com> <m1ZK9Qp-0000CWC@stereo.hq.phicoh.net> <2134F8430051B64F815C691A62D9831832ED2 9AC@XCH-BLV-504.nw.nos.boeing.com> <m1ZKpuC-0000D4C@stereo.hq.phicoh.net> <2134F8430051B64F815C691A62D9831832ED2A37@XCH-BLV-504.nw.nos.boeing.com> <20150730191629.1817894a@envy.fud.no>
From: Alexandru Petrescu <alexandru.petrescu@gmail.com>
Message-ID: <55BB73A0.4040105@gmail.com>
Date: Fri, 31 Jul 2015 15:09:52 +0200
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0
MIME-Version: 1.0
In-Reply-To: <20150730191629.1817894a@envy.fud.no>
Content-Type: text/plain; charset="windows-1252"; format="flowed"
Content-Transfer-Encoding: 8bit
Archived-At: <http://mailarchive.ietf.org/arch/msg/v6ops/J-7b2kkA8PoTxJ5OVBIzoV506pM>
Subject: Re: [v6ops] I-D Action: draft-colitti-v6ops-host-addr-availability-01.txt
X-BeenThere: v6ops@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: v6ops discussion list <v6ops.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/v6ops>, <mailto:v6ops-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/v6ops/>
List-Post: <mailto:v6ops@ietf.org>
List-Help: <mailto:v6ops-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/v6ops>, <mailto:v6ops-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 31 Jul 2015 13:10:02 -0000


Le 30/07/2015 19:16, Tore Anderson a écrit :
> * Templin, Fred L
>
>> You can't give a device a /64 using SLAAC; SLAAC only allows for
>> autoconfiguration of singleton addresses taken from an on-link /64
>> prefix.
>
> Hi Fred,
>
> Actually, SLAAC works equally well with off-link prefixes. There is
> no inherent requirement in SLAAC that prefixes from which the
> addresses are auto-configured must be on-link; the L and A bits in an
> RA's PIO are completely orthogonal.

I can agree.

>> If you want to give a device a /64, the only choices I am aware of
>> are administrative configuration or DHCPv6 PD.
>
> True, although 3GPP networks is an exception. There a /64 prefix
> advertised to the UE via standard RA/PIO with SLAAC can be treated
> as if it was a delegated prefix.  RFC7278 depends on this.

IMHO it is wrong to treat it as a delegated prefix.  RFC7278 states
clearly that the right way to get a delegated prefix is DHCPv6-PD.

The treatment 'as if' is what makes operators think that one /64 in RA
is enough space for enough devices behind the UE.

A /64 on a cellular link can only accommodate one device.  Something may
make think that the /64 is a delegated prefix that _could_ accommodate
more than one device:
- the cellular link is a ptp link.  As such the first-hop router in the
   cellular network has a specific routing table entry containing the IP
   address of the UE as next-hop (instead of a '*' if it were a shared
   link) for that /64.  This makes that any address in that /64 is
   reachable through UE's IP address.

However, cellular links continue to advance away from being ptp links
and more be 'shared' links.  Recently 4G ptp links have got 48bit MAC
addresses.  In the future there will be true Neighbor Discovery on these
links, with '*' routes instead of next-hop routes.  At that point, the
assumption that a /64 can accommodate 2^64 devices will no longer hold,
because the first-hop router will issue NSs for the dst address, instead
of issuing RSs for the IP address of the UE.

Alex

> Tore
>
> _______________________________________________ v6ops mailing list
> v6ops@ietf.org https://www.ietf.org/mailman/listinfo/v6ops
>