Large IPv6 Multicast Domains

[James Small]

Hi Benedikt,

> Hi Jim and list,
> 
> first off, I've done some IPv6 multicast routing but I've never been
> unlucky enough not to deal with it over IPv4.
> 
> > 1)      There is no MSDPv6 and probably never will be.  Of course you
> > have SSM and Embedded RP but that doesn’t cover all cases.  For
> > example – if you have a partnership with another organization and only
> > want to share select multicast groups/sources then in IPv4 you use
> > MSDP and MSDP filters.  However, I don’t see how to do this with IPv6
> > multicast.
> 
> Would it work if you used one of the available (unnamed) scopes for that
> job?  Agree on a scope that gets routed with your partner organization
> and set up your border multicast routers accordingly.

Agreed - this is a viable approach.

> > 2)      Often I see different multicast domains with MSDP between them
> > (including filters).  Do organizations just do one huge PIMv6-Anycast
> > domain and leave it at that?
> 
> I'm not sure what you mean with "PIMv6-Anycast domain", but if I

Basically something compliant with RFC 4610.  With IPv4 I would use the approach described in RFC 3446.  With IPv6 it seems like the replacement is "Anycast-RP using PIM" as described in 4610.  My concern was using this approach for a large global backbone, but sounds like that's the only option.

> understand your question correctly, then the answer is yes: One
> (possibly anycasted) RP or set of RPs for all "multicast domains" (which
> is a concept that doesn't really apply to IPv6) and matching scopes to

So essentially I should stop thinking local "domains" and think globally for any IPv6 multicast deployment?

> filter between the domains.  (And yes, there may be constellations where
> you actually run out of scopes...)
> 
> If there is no direct connection between the domains, either use some
> sort of VPN (which you'll likely have anyway) or possibly just a simple
> GRE or configured 6in4 tunnel.

Coming from an IPv4 Multicast background, I'm having a hard time accepting that my only Inter-domain RP option is embedded RP.  I understand the issues with MSDP and why it wasn't extended to support IPv6.  However, it still feels like there should be some kind of inter-domain RP communication/synchronization option.  Perhaps I have not fully grokked IPv6 Multicast yet?

Thanks,
  --Jim