Re: [dhcwg] [homenet] PPP, DHCPv6 and Prefix Delegation

Athanasios Douitsis <aduitsis@gmail.com> Tue, 19 November 2013 15:00 UTC

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Date: Tue, 19 Nov 2013 17:00:37 +0200
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From: Athanasios Douitsis <aduitsis@gmail.com>
To: "Bernie Volz (volz)" <volz@cisco.com>
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Subject: Re: [dhcwg] [homenet] PPP, DHCPv6 and Prefix Delegation
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On Tue, Nov 19, 2013 at 3:19 PM, Bernie Volz (volz) <volz@cisco.com> wrote:

> I guess from RFC 4818, Delegated-IPv6-Prefix is used for PD. Whereas it
> says:
>
>
>
>    The Framed-IPv6-Prefix attribute [4] is not designed to support
>
>    delegation of IPv6 prefixes to be used in the user's network, and
>
>    therefore Framed-IPv6-Prefix and Delegated-IPv6-Prefix attributes may
>
>    be included in the same RADIUS packet.
>
>
>
> But, I’m not really clear if that ends up mapping to OPTION_PD_EXCLUDE for
> the Framed-IPv6-Prefix. Perhaps if the case is as in your example
> (Framed-IPv6-Prefix is contained by Delegated-IPv6-Prefix, but not equal)
> then using the Framed-IPv6-Prefix for OPTION_PD_EXCLUDE makes some sense?
>

Hello,

In some cases like the one you and I have described here, I think it
probably makes sense for the delegating router to use the
Framed-IPv6-Prefix to infer what to put in the OPTION_PD_EXCLUDE. In these
cases, the delegating router probably has all the information it needs to
answer PD requests. Of course, some configuration options (e.g. do copy the
Framed-IPv6-Prefix to OPTION_PD_EXCLUDE) and sanity checks (e.g. make sure
the Framed is contained in the Delegated prefix) may be in order to make it
work right, but the idea remains essentially the same.

What I was also wondering previously is whether there are valid cases where
one would want to explicitly dictate the OPTION_PD_EXCLUDE via RADIUS,
presumably along with the Delegated-IPv6-Prefix. If those cases actually
exist, maybe a separate RADIUS attribute could be useful. Just thinking
loudly, not sure yet.

Kind regards,
-- 
Athanasios Douitsis