Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host)

Lorenzo Colitti <lorenzo@google.com> Mon, 13 November 2017 17:09 UTC

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From: Lorenzo Colitti <lorenzo@google.com>
Date: Tue, 14 Nov 2017 02:08:51 +0900
Message-ID: <CAKD1Yr1AHpSm2QxWdGNBVGHe_q42qMFwYQSaWWOQxRbbvmDVKg@mail.gmail.com>
Subject: Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host)
To: Nick Hilliard <nick@foobar.org>
Cc: "6man@ietf.org" <6man@ietf.org>, "v6ops@ietf.org WG" <v6ops@ietf.org>
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On Tue, Nov 14, 2017 at 12:48 AM, Nick Hilliard <nick@foobar.org>; wrote:

> 1. draft-ietf-v6ops-unique-ipv6-prefix-per-host says nothing one way or
> another about networks that *only* use DHCPv6 address assignment, so RFC
> 7934 is not relevant in this case, even by your own arguments.
>

Agreed. It is relevant only in that there were comments on this thread that
roughly said "why not use DHCPv6 instead".


> 2. 7934 does not state that networks that *only* use DHCPv6 address
> assignment are not recommended.  There was no WG consensus for your
> interpretation, and your interpretation is in direct conflict with the
> reality that DHCPv6 can be used to provide multiple IP addresses to a
> host, as 7934 recommends, and as was proven with working examples during
> that thread and others.  Either way, this is outside the scope of
> draft-ietf-v6ops-unique-ipv6-prefix-per-host and it's not helpful to
> have another rehash of this argument here.
>

The 7934 recommendation that can't be met by networks that only use DHCPv6
address assignment is not "provide hosts with multiple addresses" - it's
"allow hosts to form new addresses without explicit requests to the
network". But I agree it's not useful to repeat that argument here.


> 3. you are now arguing that an option to implement
> draft-ietf-v6ops-unique-ipv6-prefix-per-host with DHCPv6 shouldn't be
> considered because of rfc7934.  In other words, you're arguing that we
> shouldn't introduce the option for hosts to be able to get multiple ipv6
> addresses via dhcpv6, because according to you, rfc7934 recommends
> against using dhcpv6-only because it lacks the ability to provide
> multiple ipv6 addresses for hosts.  I.e. circular reasoning.
>

I don't think you understood me. If you're saying that a unique prefix per
host can be assigned using DHCPv6 PD, then of course that's true. Given
that DHCPv6 PD is not widely supported by hosts, it's not a fit for the
goals of this document, which are to support as many hosts as possible. But
it would work.

RFC 7934 only recommends against a network that exclusively uses DHCPv6
*address* assignment. Using DHCPv6 PD to assign a /64 *prefix* to each host
is fine (and in fact, cited as an example).