Re: [MBONED] An alternative to draft-ietf-mboned-64-multicast-address-format?

["Manfredi, Albert E" <[e-mail]>]

> -----Original Message-----
> From: Stig Venaas [mailto:[e-mail]]

> I don't think you can have just 96 fixed bits though. I'm not quite
> sure
> what you mean by predictable.
> 
> If there is nothing in say a PIM (S,G)-join (in the group address or in
> the PIM message) to say that G has a 32-bits IPv4 multicast address
> embedded, then the best I can think of is to configure the devices so
> that they know that a specific IPv6 prefix has an address embedded. But
> I don't think it can be a fixed well-known hardcoded address.

For networks that are NOT dual stack, the scheme has to work for 6 to 4 and 4 to 6.

So, the way I see it working, the easiest solution is to have a single, fixed, 96-bit IPv6 multicast prefix, for multicasts that have to do this traversing back and forth.

1. The ingress router to an IPv4-only network can detect that the IPv4 address is embedded.

2. The egress router from the IPv4 network to the IPv6 network can know what IPv6 prefix to add.

I don't see how a flag in the IPv6 multicast address can solve both problems, UNLESS we also create a new subgroup of IPv4 multicast addresses?

Bert