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

[Erik Nordmark <Erik.Nordmark@sun.com>]

> Let's take an example.  An enterprise is has a multicast application
> with IPv4, for example, video broadcast of CEO talking every morning
> :-), delivering stock prices to the brokers' terminals, or whatever.
> (Videoconferencing is out of scope.)  Those are mainly one-to-many 
> multicast.

I think you mean "single sender" since all multicast is "one-to-many".
Are you explicitly excluding applications, such a streaming media,
which have a unicast feedback channel? (for quality reports etc)

> Now, that enterprise would wish to do the same with v6, but their v6 
> routers don't support multicast (or they don't have many v6 routers in 
> the first place).

Does "don't have many v6 routers" imply that there
might not be unicast connectivity between all the nodes for which you want
to establish single-sender multicast connectivity?

> (No IPv6 addresses would be needed on the tunnel, except the 
> traditional link-locals.)

I think that implies that it is impossible to have unicast feedback;
there isn't a tunnel configured on the multicast receivers which can be
used to send packets to the senders link-local IPv6 address, is there?


> On the other hand, the benefits are:
>  1) no unicast->multicast packet duplication at the tunnel servers, 
>     etc -- uses v4 multicast techniques
>  2) no new protocols needed, i.e., if deploying/implementing 6over4 is 
>     not seen feasible, this could provide a means to achieve some 
>     benefits of 6over4 for v4 multicast application.

But why not just run this application over IPv4 multicast?
I don't see what IPv6 multicast using only IPv6 link-local addresses
(and perhaps not a unicast return channel) would provide
over what IPv4 multicast can provide in this case.

   Erik