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

David Farmer <farmer@umn.edu> Mon, 13 November 2017 15:34 UTC

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From: David Farmer <farmer@umn.edu>
Date: Mon, 13 Nov 2017 09:33:56 -0600
Message-ID: <CAN-Dau1yMCMAJGhjgEG41L14uPX_=WwcHfcWpPUfjJse6ZK3rg@mail.gmail.com>
Subject: Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host)
To: Fernando Gont <fgont@si6networks.com>
Cc: Ted Lemon <mellon@fugue.com>, IPv6 Ops WG <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>
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On Mon, Nov 13, 2017 at 8:57 AM, Fernando Gont <fgont@si6networks.com>;
wrote:

> Ted,
>
> On 11/13/2017 10:31 PM, Ted Lemon wrote:
> > Fernando, the document is in AUTH48. If there is a technical problem
> > with it that is sufficient to pull it out of the publication queue at
> > this point, I haven't heard it yet. I think it would be nice to add a
> > little advice on how to manage the state, but it's up to the authors to
> > do this or not. This discussion is getting a bit old.
>
> The technical problem is that this is a v6ops document making SLAAC
> stateful. As discussed, making SLAAC stateful brings breakage scenarios
> not present in SLAAC, and that is certainly not a minor change.
>
> And having folks noted that they have implemented this sort of behavior
> without changing SLAAC, the low-level protocol details in Section 4 are
> even less unwarranted.
>
> It is not my call what's the proper action. But I do note that this is
> yet another BCP that rather that essentially disregards work of other wg
> (dhc), unnecessarily. Are you are pushing a BCP with a mechanism that is
> so underspecified, that folks meaning to implement this are likely to
> introduce breakage.
>
> That said, it is not my call what's the proper action to follow. My
> intent (noted to e.g. Suresh off-line) is not to obstruct the document,
> but to avoid breakage -- particularly when it's unwarranted.
>

You claim this is making SLAAC stateful by adding state to the router.
However, if anything this reduces the state the router needs to track.
Currently the router has to track address state of  O(NxM).  Where N =
Number Hosts, and M = Average Number Addresses used per Host.  With Unique
Prefix per host, the router only has to track prefix state of O(N).
Allowing a host to use as many addresses as it sees fit without impacting
the amount of state the router has to track.

Further, it seems to me that if anything it's Neighbor Discovery that is
changed, and not SLAAC, and Neighbor Discovery has always been stateful.
Now I don't believe the Neighbor Discovery protocol is actually being
changed, it is merely being implemented differently within the variations
allowed by the protocol.

Finally, this discussion has relieved that there this draft is incomplete
in several ways.  However this document is not any more incomplete than
many other documents already approved by the IESG and implemented on
thousands or even millions of hosts.  That is why we revise documents, we
never get it right the first time.

Thanks.

-- 
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