On 3/29/12 7:16 AM, Stig Venaas wrote:
On 3/29/2012 3:38 AM, Kerry Lynn wrote:
On Thu, Mar 29, 2012 at 12:02 PM, Iljitsch van Beijnum
<iljit...@muada.com <mailto:iljit...@muada.com>> 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
IMO you cannot do that. The higher scope value, the wider distribution.
If you have scopes X and Y where X < Y, then the distribution of X
should be a subset (can be the same) of the distribution of Y.
There are implementations making such assumptions.
It is not an assumption, it is stately quite clearly in the Scoped
Addressing Architecture (RFC 4007). From Section 5 :
A zone of a given scope (less than global) falls completely within
zones of larger scope. That is, a smaller scope zone cannot
include more topology than would any larger scope zone with which
it shares any links or interfaces.
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.
Correct me if I'm wrong, but isn't Admin Scoped multicast defined on a
per-
port, per-application basis? That would suggest that some multicast group
addresses can (selectively) be forwarded through the CER uplink to the
ISP.
There is nothing magical with scope 4. It is wider than link-local, and
you need to configure routers to limit the distribution according to
your policy.
RFC 4007 lays out all the rules you need to adhere to for scoped
addressing boundaries.
Regards,
Brian
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