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

DY Kim <dykim6@gmail.com> Sat, 11 November 2017 03:02 UTC

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Subject: Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host)
From: DY Kim <dykim6@gmail.com>
In-Reply-To: <59F47233-62ED-489D-9421-00128C8E7EB2@fugue.com>
Date: Sat, 11 Nov 2017 12:02:12 +0900
Cc: Fernando Gont <fgont@si6networks.com>, IPv6 Operations <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>, "6man-ads@tools.ietf.org" <6man-ads@ietf.org>, "v6ops-ads@ietf.org" <v6ops-ads@ietf.org>, draft-ietf-v6ops-unique-ipv6-prefix-per-host@tools.ietf.org
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To: Ted Lemon <mellon@fugue.com>
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The issue is about the router crash and recovery, not SLAAC itself; not particular about SLAAC.

Even with the legacy operation wherein the router is assigned a link prefix (from the site server by some means) to be advertised to the hosts on the shared link and the hosts run SLAAC for address assignment to their interfaces, what happens if the router crashes?

Either the router has kept that link prefix in a stable storage, or if not, the router might have to acquire a new link prefix from the site server, and not even knowing whether the refreshed prefix should be the same as or different from the previous one, the router and the hosts on the link might go through a painful renumbering anyhow.

Hence, the issue, if any, should be raised against the router spec, not against this draft or even SLAAC, I’d think.

---
DY

> On 11 Nov 2017, at 11:45, Ted Lemon <mellon@fugue.com>; wrote:
> 
> The issue is that if you have allocated a prefix for a host and then you reboot the router, either you retain the allocation in stable storage, or you don't.   If you don't, how do you make sure that the host doesn't get renumbered?
> 
> That's the sense in which this is stateful, whereas SLAAC by itself is not.   It's not really SLAAC that's stateful—it's the mapping between the link-local SLAAC address and the prefix that's assigned to the host.