Re: [v6ops] draft-wbeebee-v6ops-ipv6-cpe-router-bis - where to go from here

[Ole Troan <[e-mail]>]

Jack,

>> please see the discussion a month or two ago. the CPE has not
>> information available to request a certain prefix size.
>> 
> 
> CPE has the information available to
> 
> 1) request it's immediate needs if it's virgin

unless the CPE is configured with this information it has no available information to know the size required to number the site behind it.

> 2) request an aggregate of it's needs and all subtending needs if it has active prefix information.
> 
> As I have mentioned, the ability for a CPE to expand it's prefix with the ISP is also of great benefit in this case.

"expanding" the site can only be done either by renumbering or doing flat as in /64s prefix delegation.

>> how the provider deals with delegating prefixes and the size of the
>> prefix is up to provider policy. there is nothing stopping a provider
>> from assigning whatever sized prefix to whatever number of connected
>> CPEs in a single site.
>> 
> 
> A mechanism isn't documented for a variable prefix layout. As you said, the CPE (especially virgin) has no idea what it's future needs might be. If the ISP hands it a large prefix, it has what it has to work with. However, an ISP should be able to support more, handing out portions of a /48 to a customer site regardless of how they connect routers to the ISP.

then hand out /56s to up to 256 CPEs.

>> you cannot expect to rely on a hint in the PD message to determine
>> the size to delegate, nor can the provider depend on multiple IAIDs
>> in the request.
> 
> Depend, no. Which is why I wrote up a rough idea of ISP logic which could compensate for a variety of dumb and smart CPEs. The HINT is useful in making determinations. Lack of a HINT can be answered in a number of ways. As for multiple IAIDs, if CPEs aren't FORCED to support this, we will have problems when delegations are too small for what is required (unless we just want to sit back and proxy-nd everything when we are out of prefix space).

with a /56 a end user site has 2^8 number of prefixes, do we think that will ever run out? if so, he can justify a request for whatever he needs.

you can either do flat delegation and expose the internal topology of the end user site to the SP or you can do aggregated delegation.  you _could_ imagine a CE using multiple IAIDs to request additional bits of address space. but that would complicate sub-delegation a lot. all the proposals I'm aware of are based on a single site prefix being subdelegated...

in any case I don't think there is anything for the Basic IPv6 CE document here. but lots of opportunities for a home networking architecture one, so I look forward to drafts! ;-)

cheers,
Ole