Re: [v6ops] SLAAC renum: Problem Statement & Operational workarounds

Fernando Gont <fgont@si6networks.com> Fri, 01 November 2019 03:07 UTC

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To: Owen DeLong <owen@delong.com>
Cc: Ted Lemon <mellon@fugue.com>, Philip Homburg <pch-v6ops-9@u-1.phicoh.com>, v6ops@ietf.org
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From: Fernando Gont <fgont@si6networks.com>
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Subject: Re: [v6ops] SLAAC renum: Problem Statement & Operational workarounds
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On 31/10/19 16:39, Owen DeLong wrote:
> 
> 
>> On Oct 31, 2019, at 12:25 PM, Fernando Gont <fgont@si6networks.com> wrote:
>>
>> On 27/10/19 10:54, Ted Lemon wrote:
>>> On Oct 27, 2019, at 9:41 AM, Philip Homburg <pch-v6ops-9@u-1.phicoh.com
>>> <mailto:pch-v6ops-9@u-1.phicoh.com>> wrote:
>>>> The little bit missing is that the CPE should write prefixes
>>>> advertised using
>>>> SLAAC to persistent storage which allows the CPE to invalidate stale
>>>> prefixes
>>>> after a reboot.
>>>
>>> Actually I do not believe this is correct behavior.   Let us assume
>>> prefix delegation.   If we have prefix delegation, then when the CPE
>>> comes back from a power cycle, it should reconfirm the prefix it had
>>> previously; the assumption is that that prefix is still valid.  This can
>>> be handled in infrastructure—the ISP edge router should know whether the
>>> prefix is still valid, because if it is it should be advertising a route
>>> for it.   If it is not still valid, then the CPE router should attempt
>>> to renew it, which would go to the DHCP server (possibly both messages
>>> would).
>>
>> That assues the CPE has stored the previously-leased prefix on stable
>> storage -- which does not need to be the case. Hence the related text in
>> our I-D.
> 
> IMHO, the CPE requirements should be increased and the CPE should be required
> to store the prefix and it’s expected valid and preferred expiration times in persistent
> storage. I would like to see the text in the I-D updated accordingly.

It's already there (draft-gont-v6ops-slaac-renum-00):

3.2.1.  Signaling Stale Configuration Information

   In order to phase-out stale configuration information:

   o  A CPE router sending RAs that advertise dynamically-learned
      prefixes (e.g. via DHCPv6-PD) on an interface MUST record, on
      stable storage, the list of prefixes being advertised on each
      network segment.


Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492