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

Fernando Gont <fgont@si6networks.com> Thu, 24 October 2019 11:18 UTC

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To: 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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Date: Thu, 24 Oct 2019 08:17:48 -0300
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Subject: Re: [v6ops] SLAAC renum: Problem Statement & Operational workarounds
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Hello, Philip,

On 24/10/19 02:42, Philip Homburg wrote:
>> A better mitigation is to affect the preferred and possibly the valid
>> lifetimes in response to consecutive RAs from the same router that lack
>> the original (stale) prefix. e.g., after two consecutive RAs that do not
>> contain the existing prefix, reduce the preferred lifetime. After two
>> additional RAs, reduce the valid lifetime.
> 
> I think that to avoid confusion it is probably best to have 3 documents:
> - one that describes host behavior. I think that what you describe above would
>   fit in such a document. There is a lot we can do to make hosts more robust.

Agreed. FWIW, We should have such document ready this weekend.


> - one that describes CPE behavior. If the CPE explicitly deprecates old
>   prefixes then that solves the problem with CPE reboots. Having
>   more sensible lifetimes fits in such a document, but I don't think it
>   provides a solution. It just reduces some secondary effects such as
>   stale prefix build up.

Agreed


> - Finally, a document for ISPs describing how to best provide prefixes 
>   using DHCPv6-PD. 
> 
> I think all 3 approaches are needed:
> - a host doesn't want to rely on a cheap CPE doing its job.
> - a quality CPE can provide better support for hosts today. There will always
>   be ISPs that do flash renumbering
> - finally a quality ISP may have a need to renumber customers and would like
>   to do so without breaking things.

I fully agree with your assessment. That said, maybe the first step is
to start with a problem statement, as with this document?

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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