Re: You asked about multicast scope

[Fred Baker <[e-mail]>]

On Mar 29, 2012, at 12:02 PM, Iljitsch van Beijnum wrote:

> On 28 Mar 2012, at 12:08 , Fred Baker wrote:
> 
>>> I haven't read the spec yet, but isn't PCP supposed to work in the service provider run NAT64/CGN case, too? In that case, the multicasts need to escape out of the site or even organization to reach the service provider at least in the SOHO case. So this would be a scope just shy of global, maybe a new "service provider" scope?
> 
>> I personally rarely use "zero configuration" and "service provider" in the same sentence...
> 
> Am I understanding you correctly when I take that to mean that the admin (value 4) scope is appropriate because then the people running the multicast routing can determine exactly how far these packets travel?
> 
> That makes sense, but there is one potential issue, that I think some people who are well-steeped in IPv6 multicast should look at: in this situation, the scope value 4 may need wider distribution than side-wide, which is scope 5. I can't find any documentation on whether that's ok or not between sessions right now, but I'm reluctant to assume that a lower scope value can have wider distribution than a higher one without having a spec that explicitly says so or hearing from some implementers.

I imagine. Note that the document actually says "organization scope".

The non-boilerplate part of the document contains 44 sentences; three of them, in sections 4 and 5, mention the specifics of the scope. Is it fair to assume that you have no issue with the remaining sentences?

4.  IANA Considerations

   This note requests of the IANA the assignment of a set of multicast
   addresses as described in Section 2.7 of the IP Version 6 Addressing
   Architecture [RFC4291] from the registry [v6mult].  This set of
   addresses is referred to as "ALL-NPTv6-TRANSLATORS".  One address
   should be assigned for each of the following scopes: Link-Local,
   Admin-Local, Site-Local, and Organization-Local.


5.  Operational Considerations

   This document defines a set of multicast addresses in several scopes.
   Operationally, the choice of which scope is appropriate is made by
   the administration.  A reasonable default value in system
   configurations might be Organization-Local (e.g., all NPTv6
   Translators operated by the organization).  However, a large
   organization might well choose Site-Local or Admin-Local, and
   consider that "site" or "administrative" domain to include the set of
   NPTv6 Translators advertising a default route into a specific part of
   its network.