Re: [v6ops] A common problem with SLAAC in "renumbering" scenarios

Richard Patterson <richard@helix.net.nz> Thu, 31 January 2019 13:51 UTC

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From: Richard Patterson <richard@helix.net.nz>
Date: Thu, 31 Jan 2019 13:51:31 +0000
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Subject: Re: [v6ops] A common problem with SLAAC in "renumbering" scenarios
To: Fernando Gont <fgont@si6networks.com>
Cc: Tassos Chatzithomaoglou <achatz@forthnet.gr>, "6man@ietf.org" <6man@ietf.org>, IPv6 Operations <v6ops@ietf.org>
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On Thu, 31 Jan 2019 at 12:15, Fernando Gont <fgont@si6networks.com> wrote:
>
> On 31/1/19 08:40, Tassos Chatzithomaoglou wrote:
> > Isn't that handled by L-13 of RFC7084?
> >
> > L-13:  If the delegated prefix changes, i.e., the current prefix is
> >           replaced with a new prefix without any overlapping time
> >           period, then the IPv6 CE router MUST immediately advertise the
> >           old prefix with a Preferred Lifetime of zero and a Valid
> >           Lifetime of either a) zero or b) the lower of the current
> >           Valid Lifetime and two hours (which must be decremented in
> >           real time) in a Router Advertisement message as described in
> >           Section 5.5.3, (e) of [RFC4862].
>
> Yes, we missed this REQ, and will update our doc accordingly. HOwever,
> this bullet was included for completeness sake. The case we care and are
> trying to address here is that in which the CPE reboots.

I think this requirement already resolves the CPE-side of things, and
the rest I believe, is solved server-side?
If the CPE is hard rebooted, it hasn't sent a Release, so I'd expect
the lease-state to be kept server-side, and re-offered if the DUID+MAC
binding is the same when the CPE reconnects.

Although, during soft reboots, I have often seen CPEs sending a
Release, telling the servers to relinquish the lease.  Perhaps we
should discuss the benefits/detriments of doing this?