Re: [Roll] Multi-Link Subnets via /128

Michael Richardson <mcr+ietf@sandelman.ca> Thu, 25 July 2013 21:37 UTC

Return-Path: <mcr@sandelman.ca>
X-Original-To: roll@ietfa.amsl.com
Delivered-To: roll@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 2952321F853A; Thu, 25 Jul 2013 14:37:44 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.044
X-Spam-Level:
X-Spam-Status: No, score=-2.044 tagged_above=-999 required=5 tests=[AWL=0.555, BAYES_00=-2.599]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OStCvNwusq8f; Thu, 25 Jul 2013 14:37:43 -0700 (PDT)
Received: from tuna.sandelman.ca (tuna.sandelman.ca [IPv6:2607:f0b0:f:3::184]) by ietfa.amsl.com (Postfix) with ESMTP id 62C2E21F852D; Thu, 25 Jul 2013 14:37:43 -0700 (PDT)
Received: from sandelman.ca (obiwan.sandelman.ca [IPv6:2607:f0b0:f:2::247]) by tuna.sandelman.ca (Postfix) with ESMTP id 35ADE20168; Thu, 25 Jul 2013 18:43:20 -0400 (EDT)
Received: by sandelman.ca (Postfix, from userid 179) id 5585163A88; Thu, 25 Jul 2013 17:36:13 -0400 (EDT)
Received: from sandelman.ca (localhost [127.0.0.1]) by sandelman.ca (Postfix) with ESMTP id 4357763A7C; Thu, 25 Jul 2013 17:36:13 -0400 (EDT)
From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Routing Over Low power and Lossy networks <roll@ietf.org>, "6man@ietf.org" <6man@ietf.org>
In-Reply-To: <CE16D142.225DC%d.sturek@att.net>
References: <CE16D142.225DC%d.sturek@att.net>
X-Mailer: MH-E 8.2; nmh 1.3-dev; GNU Emacs 23.4.1
X-Face: $\n1pF)h^`}$H>Hk{L"x@)JS7<%Az}5RyS@k9X%29-lHB$Ti.V>2bi.~ehC0; <'$9xN5Ub# z!G,p`nR&p7Fz@^UXIn156S8.~^@MJ*mMsD7=QFeq%AL4m<nPbLgmtKK-5dC@#:k
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="=-=-="; micalg="pgp-sha1"; protocol="application/pgp-signature"
Date: Thu, 25 Jul 2013 17:36:13 -0400
Message-ID: <9271.1374788173@sandelman.ca>
Sender: mcr@sandelman.ca
Subject: Re: [Roll] Multi-Link Subnets via /128
X-BeenThere: roll@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
Reply-To: Routing Over Low power and Lossy networks <roll@ietf.org>
List-Id: Routing Over Low power and Lossy networks <roll.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/roll>, <mailto:roll-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/roll>
List-Post: <mailto:roll@ietf.org>
List-Help: <mailto:roll-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/roll>, <mailto:roll-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 25 Jul 2013 21:37:44 -0000

Don Sturek <d.sturek@att.net> wrote:

    > Note I changed the title on the thread......

Thank you.
I would like to know what a multi-link subnet via /128 means.

    > My problem with RFC 5889 (http://tools.ietf.org/html/rfc5889) is that it
    > solves the problem simply by saying "don't allocate link locals".   The
    > issue I have is that it precludes the use of mDNS (which operate off of
    > link locals).

1) mDNS doesn't have to use link locals, it can, and does distribute ULAs and
   GUAs v6 addresses just fine.

2) sdnsext might well fix mDNS to run across multiple subnets, not just
   a multi-link subnet.

    > Some questions:
    > 1)  Would you recommend then the allocation of ULA's with a /128 (as
    > opposed to globals).  There are a lot of applications that really only
    > need to communicate within a residence and don't really have a need in
    > having all devices using globals

Yes to ULAs or to NCN's GUAs... but I understand the question.

    > 2)  If we use ULA's, there does not seem to be guidance around which
    > interfaces to perform prefix delegation on and which should not
    > (specifically, I am thinking of rules that a border router would use as to
    > where to issue PIOs in a RPL sense)

My reading/understanding/coding is that a border router which thinks it is
grounded (G=1) should issue PIOs.

    > 3)  And of course if there ended up being more than one border router,
    > there is also not guidance on how to combine or proxy ULA prefixes (maybe
    > this topic could be a Homenet solution....)

homenet might provide a solution outside of the RPL space for deciding who
will be the root ULA provider and how that might get distributed, but that
won't help many RPL/LLN deployments.

    > In case anyone is wondering, our initial application deployment using
    > ZigBee IP was Smart Energy Profile 2.0 (SEP 2.0).   There was a
    > requirement to perform service discovery without a centralized repository
    > (since it was a multivendor deployment where no device manufacturer wanted
    > responsibility for a centralized DNS).  mDNS (extended to use ULAs) was
    > our choice.  It would seem with a /128, we would still need the same
    > extensions to mDNS.   We plan to support Wi-Fi, HomePlug Power Line
    > Carrier and ZigBee IP in a combined network topology within the home.

I assume you used trickle-mcast to propogate the mDNS.
Across those three links types, did you have a single ULA/64?
How did the gateways between the media types know that they were not at a
scope-3 boundary?

--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works