Re: v6-in-v4 configured tunneling over v4 multicast (vs 6over4)

[Fred Templin <ftemplin@iprg.nokia.com>]

Pekka,

Pekka Savola wrote:

> If you want to create point-to-multipoint tunnels over v4 multicast
> infrastructure, wouldn't the obvious solution be simply using
> configured tunneling?  That is, you configure the tunnel destination
> v4 address to be a multicast address (this requires zero code
> changes), and the decapsulators configure their "local end" to be the
> multicast address (requires code change in the tunnel setup tool to
> permanently join the specified multicast address)?

As you know, the decapsulating end of a configured tunnel requires
a specific IPv4 source address for the "remote end" of the tunnel, so
the configured tunnels you describe would only be able to decapsulate
multicasts from a single specific encapsulator. I.e., you would need
one such configured tunnel for each potential encapsulator (which
could be a large number).

If you want a single tunnel interface that could decapsulate multicasts
from *any* decapsulator, you would need something like 6over4 (or,
ISATAP if the IPv6 multicast address is mapped to a unicast IPv4
link-layer address.) Your configured tunnels could still be used as
decapsulator-specific "overlays" (if needed), but it seems like
you would still need the 6over4/ISATAP for wildcard match
on a large set of potential encapsulators.

Fred
ftemplin@iprg.nokia.com