Re: [v6ops] How do you solve 3GPP issue if neither operator nor handset supports PD?

otroan@employees.org Tue, 24 November 2020 14:50 UTC

Return-Path: <otroan@employees.org>
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 CAB083A0F06 for <ipv6@ietfa.amsl.com>; Tue, 24 Nov 2020 06:50:20 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: 0
X-Spam-Level:
X-Spam-Status: No, score=0 tagged_above=-999 required=5 tests=[SPF_HELO_NONE=0.001, 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 eVp91qV2IbyF for <ipv6@ietfa.amsl.com>; Tue, 24 Nov 2020 06:50:19 -0800 (PST)
Received: from clarinet.employees.org (clarinet.employees.org [IPv6:2607:7c80:54:3::74]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 03B753A0F22 for <ipv6@ietf.org>; Tue, 24 Nov 2020 06:50:18 -0800 (PST)
Received: from astfgl.hanazo.no (unknown [IPv6:2a01:79c:cebd:9724:e591:b8dd:48ed:9fb0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by clarinet.employees.org (Postfix) with ESMTPSA id A63CD4E11AD6; Tue, 24 Nov 2020 14:50:17 +0000 (UTC)
Received: from [IPv6:::1] (localhost [IPv6:::1]) by astfgl.hanazo.no (Postfix) with ESMTP id 67A9D45E262F; Tue, 24 Nov 2020 15:50:15 +0100 (CET)
Content-Type: text/plain; charset="us-ascii"
Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.20.0.2.21\))
Subject: Re: [v6ops] How do you solve 3GPP issue if neither operator nor handset supports PD?
From: otroan@employees.org
In-Reply-To: <m1khZLr-0000IXC@stereo.hq.phicoh.net>
Date: Tue, 24 Nov 2020 15:50:14 +0100
Cc: 6man WG <ipv6@ietf.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <51F56897-AEE2-43E6-8FCC-BD9412B53675@employees.org>
References: <CABNhwV2-dH81CY4wSisV8BU-7H9m5a1xYMqTMecRxhNqZe=ApQ@mail.gmail.com> <CAKD1Yr1xV179LZ7Kxtk5mGruJcJ+BpGb2heBBy4ORtRU7bfvqw@mail.gmail.com> <CAMGpriWqnmL0qo0Hm=b+GbzcdCuXz6PM5aq8owE7-=ty5pDFsw@mail.gmail.com> <1DB65027-BEF2-4C0A-ACF4-C979DA7444C2@employees.org> <m1khXWs-00007wC@stereo.hq.phicoh.net> <47150D97-27D7-4AFD-8418-692D68D09828@employees.org> <m1khXol-0000MEC@stereo.hq.phicoh.net> <BD254B32-FAAE-4433-9CF5-2AF19275CA96@employees.org> <m1khZLr-0000IXC@stereo.hq.phicoh.net>
To: Philip Homburg <pch-ipv6-ietf-6@u-1.phicoh.com>
X-Mailer: Apple Mail (2.3654.20.0.2.21)
Archived-At: <https://mailarchive.ietf.org/arch/msg/ipv6/LQcU92QEB-3ey1sBarD_cpAvzwc>
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, 24 Nov 2020 14:50:21 -0000

Philip,

>> Neither do any implementation I'm aware do that.
>> To be clear. If a link-type has no L2 address / is point to point, then 
>> no implementation I've touched does ND address resolution.
>> It would be happy to respond to a NUD message.
> 
> ND answers two questions, what is the L2 address of an address and is the
> remote node alive.

ND has many functions.
One is address resolution and another is NUD (neighbor unreachability detection).
They use the same messages but have distinct functions.

> So from my point of view it is obvious to just send an NS, mark the neighbor
> cache as incomplete until you get an NA back. Then you know that neighbor
> is alive.

If you have a neighbor cache for neighbors for p2p links.

> Now, I wouldn't mind if other implementations would not send the NS and
> just assume that their neighbors are alive.
> 
> However I found that most sutff just doesn't reply with an NA at all.

Right. While NUD isn't a particularly effective keepalive/link state detection mechanism I would expect it to be supported.

>> The current behaviour of 64share does that (and gets the hack label
>> for that reason).  What I'm saying is that 64share (and what I
>> propose in p2p ethernet) is a lot closer to PD than it is to address
>> assignment.  As soon as you stop thinking that a p2p link has a
>> shared subnet, that's where you end up.
> 
> From a 'bits on the wire' point of view, there is nothing magic to PD.
> It is just a message that says: here is prefix, you can do with it as you
> see fit.
> 
> The devil is in the details. What if the down stream router then hands out
> the prefix using DHCPv6 PD. Do we need to do anything special for homenet?
> (I guess doing PD using RA would actually be the 3rd version of PD, because 
> homenet also does prefix delegation).

no, I can't see that the protocol external to the homenet matters.
homenet does not do prefix delegation. homenet does prefix assignment.

> If we want this to work on ethernet, we may have to say something specific,
> like 'a route will be installed that points to the (link local) source
> address of the RS'. Which I guess implies that an RA with a PDIO can only
> be sent in response to an RS (on ethernet). Then, what do we do on p2p links.

p2p links are simple. my proposal is also to treat Ethernet as a P2P link.
But otherwise, yes, you would have to install the route with the LL as NH.

The biggest difference I see between DHCP PD and something we might do in RA is the coupling between interface state and prefix.
DHCPv6 PD is essentially a fax-replacement. A delegation is independent of the upstream link-state, and in theory also which interface the delegation was received on. Although the realities of routing quickly sets in. If in RA the delegation's lifetime is restricted by the link-state/lifetime of RA, then that will have significant issues for downstream hosts/applications.

Cheers,
Ole