Re: I-D Action:draft-ietf-v6ops-ipv6-cpe-router-03.txt

[Ole Troan <ot@cisco.com>]

Mark et al,

> Maybe I'm being a bit overly paranoid about people being precious with
> IPv6 address space, however, the last sentence of -
> 
> 
> "WPD-1:  The IPv6 CE router MUST support DHCP prefix delegation
>           requesting router behavior as specified in [RFC3633] (IA_PD
>           option).  The IPv6 CE router MUST ask for a prefix large
>           enough to cover all of its LAN interfaces."
> 
> could be interpreted to mean that the ISP only needs to provide a
> prefix to meet the requested size e.g. for two LAN interfaces a /63.
> That would seem to me to be encouraging an "only enough" address space
> model, rather than a "more than enough" address space model, which is
> what I think IPv6 is aiming at.
> 
> There might be some value in stating that it is likely that an ISP will
> delegate a prefix that not only meets this minimum requirement but also
> allows for a number of additional subnets downstream of the CPE, with
> the delegated prefix size likely significantly larger, possibly a /48
> or /56. IOW, stating that the delegated prefix will likely be larger
> than what is requested (not that it is probably likely, but I could see
> a CPE vendor adding in a check to see if the delegated prefix size was
> equal to that requested, and if it didn't, not using it).

with multiple suggestions and comments on this thread. I've tried to wordsmith two suggestions. the first one saying nothing about the hint to the delegating router. it is after all only a weak may in rfc3633 and most service providers would most likely just ignore the hint anyway. the second, clearer text what the hint should be and also clarify that it is only a hint.

can we get consensus on one of these?

   WPD-1a:  The IPv6 CE router MUST support DHCP prefix delegation
           requesting router behavior as specified in [RFC3633] (IA_PD
           option).

   WPD-1b:

           (a)  The IPv6 CE router MUST support DHCP prefix delegation
                requesting router behavior as specified in [RFC3633]
                (IA_PD option).

           (b)  The IPv6 CE router MAY indicate as a hint to the
                delegating router the size of the prefix it requires.
                If so, it MUST ask for a prefix large enough to assign
                one /64 for each of its interfaces rounded up to the
                nearest nibble and MUST be configurable to ask for more.
                The IPv6 CE router MUST be prepared to accept a
                delegated prefix size different from what is given in
                the hint.



Best regards,
Ole