All things related to multicast

[Bill Owens <>]

On Thu, Feb 24, 2011 at 10:57:30AM -0500, Garry Peirce wrote:
> Using the frequency of messages on this list and working SAP entries as a
> rudimentary gauge, the level of interdomain v4 multicast work/content seems
> low (not to mention v6 which is not yet possible for us).   

I think that the level of interdomain multicast is low, and not likely to 
increase. So I would like to talk about v6 multicast, since I've grown jaded 
and find ordinary v4 multicast to be quite boring ;)

Actually, it's because I have been worrying for some time about how the 
transition to v6 multicast will affect the current users, though they may be 
few in number. Specifically because we will lose interdomain any-source 
multicast, which means that the original vic/vat model of sources being able 
to come and go as they please simply doesn't exist any more. 

This means no more "TV guide" function with SAP/SDP, which won't be much 
missed since the list has long been clogged with advertisements from 
admin-scoped groups coming from misconfigured sources. Unfortunately it also 
affects the folks at the Access Grid, based on what I can find out about how 
their software is set up.

It might be possible to rebuild the AG model so that it could function with 
embedded-RP, if there were a 'host' for each session with a willingness to 
operate an RP available to all the participants. That's probably the path of 
least resistance, though it still doesn't look like an easy job.

The $64 question, then: when will this become necessary? I suspect that the 
pressure will arise in the APNIC region since they'll be the first to run out 
of v4, and existing networks will eventually feel the need to go behind NAT 
in order to keep growing (assuming that they run dual-stack, v4 NAT and v6 
native). I don't know when that will happen, though; perhaps we have a few 
years yet before any of the R&E institutions run out of their existing v4 
allocations. 

Am I missing anything about the AG model, or any feature of v6 multicast that 
would allow it to continue working as it has? And are there any other 
widely-used interdomain applications that also rely on the traditional ASM 
model?

Bill.