IETF Logo Mail Archive

Re: on-link and off-link addresses, side discussion

Simon Hobson <linux@thehobsons.co.uk> Tue, 06 July 2021 16:32 UTC

Return-Path: <linux@thehobsons.co.uk>
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 ACC293A2D81 for <ipv6@ietfa.amsl.com>; Tue, 6 Jul 2021 09:32:14 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.898
X-Spam-Level:
X-Spam-Status: No, score=-1.898 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_NONE=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 zPUsvp-LqZc7 for <ipv6@ietfa.amsl.com>; Tue, 6 Jul 2021 09:32:12 -0700 (PDT)
Received: from patsy.thehobsons.co.uk (patsy.thehobsons.co.uk [80.229.10.150]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 4921A3A2D7E for <ipv6@ietf.org>; Tue, 6 Jul 2021 09:32:12 -0700 (PDT)
X-Virus-Scanned: Debian amavisd-new at patsy.thehobsons.co.uk
Received: from [192.168.137.104] (unknown [192.168.137.104]) by patsy.thehobsons.co.uk (Postfix) with ESMTPSA id 539776402F for <ipv6@ietf.org>; Tue, 6 Jul 2021 16:32:07 +0000 (UTC)
Content-Type: text/plain; charset="us-ascii"
Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\))
Subject: Re: on-link and off-link addresses, side discussion
From: Simon Hobson <linux@thehobsons.co.uk>
In-Reply-To: <2f1f68a1-8130-45b6-0586-6340f5e0bf9a@gmail.com>
Date: Tue, 06 Jul 2021 17:32:06 +0100
Content-Transfer-Encoding: quoted-printable
Message-Id: <8FC82801-F5FC-4FC3-8946-C37D1420248D@thehobsons.co.uk>
References: <162512790860.6559.14490468072475126698@ietfa.amsl.com> <CAFU7BAT0O9nsuhs5FyNjvPfRKY+EM1fLYKaMYTwaPg2QjZAEpA@mail.gmail.com> <61e14cd7-ff37-5380-e547-8a9b6d3993da@gmail.com> <CAFU7BASF-vas+PP2dVNXuqScQArC+joB-fwRGzG3UZnsqq1QJg@mail.gmail.com> <2f1f68a1-8130-45b6-0586-6340f5e0bf9a@gmail.com>
To: 6man <ipv6@ietf.org>
X-Mailer: Apple Mail (2.2104)
Archived-At: <https://mailarchive.ietf.org/arch/msg/ipv6/TmftqlNVmqMw0GiRjMvM8tT8WhE>
X-BeenThere: ipv6@ietf.org
X-Mailman-Version: 2.1.29
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, 06 Jul 2021 16:32:15 -0000

Alexandre Petrescu <alexandre.petrescu@gmail.com> wrote:

>> I suggest you look at it from a different angle. "on-link address" is
>> defined as an address that is assigned to an interface on a specified
>> link.
> 
> But, each address is on a link.
> 
> On-link means the address is on this link that we are assuming commonly.
> The term off-link means that the address is not on this link we assume
> commonly, but is on-link on another link.

Isn't it simpler than that ?
On link == hosts can directly contact other hosts in the prefix via this link
Not on link == hosts can only contact other hosts in the prefix via one or more intermediaries

Intermediary in this case is quite flexible and could include routing packets or mechanisms like proxy ND

I think any more is just making things complicated. If the link is of a type (e.g. unfiltered ethernet) where neighbours can find each other (e.g. using ND), then a prefix can be on-link. Otherwise (non-broadcast link technology, security filtering, etc), prefixes will need to be off-link.


OK, so what have I missed here ?

Simon

v2.30.2 | Report a Bug | By Email | System Status