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

[Brian E Carpenter <brc@zurich.ibm.com>]

Pekka Savola wrote:
> On Tue, 11 May 2004, Erik Nordmark 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)?
> >
> > This implies that all IPv6 (unicast and multicast) packets will be sent
> > as IPv4 multicast, right?
>
>
> Not necessarily -- sorry for failing to say that explicitly in the
> first place (you guys couldn't read my mind yet?!?! :).  See the note
> I wrote to Stig for clarification.
>  
>
> > While that might significantly increase the use of IPv4 multicast, it might
> > have negative implications on the performance of the network :-)
>
>
> Yes, it could be a problem -- a bit in the same way as 6over4 (in this
> context) hass a problem.  But luckily enough, this would probably
> apply only to v6 multicast of scope greater than link-local.

6over4 only uses v4 multicast when native IPv6 over Ethernet would use
Ethernet multicast, so I don't see this as a significant issue for
6over4. In fact, the only known issue with 6over4 is that most enterprises
don't run v4 multicast on their intranets. Any other solution relying
on v4 multicast has this issue.

   Brian

   Brian