Subject: Re: New Internet Draft on IP multicasting over ATM

From: [email-masked] (Ajay Bakre)
Date: Mon, 1 Dec 1997 20:11:16 -0800

> From [email-masked] Wed Nov 26 13:04:56 1997
> Date: Wed, 26 Nov 1997 15:02:17 -0500 (EST)
> From: Joel Halpern <[email-masked]>
> X-Sender: jhalpern@lobster
> To: Ajay Bakre <[email-masked]>
> cc: [email-masked], [email-masked], [email-masked],
>         [email-masked], [email-masked], [email-masked],
>         [email-masked]
> Subject: Re: New Internet Draft on IP multicasting over ATM
> MIME-Version: 1.0
> 
> Your section 5 (Interworking with External Mrouters) and in particular the
> section where you say "the border routers will cooperate to make sure that
> only one of them is the ATM entry for any given IP source network" is the
> tricky part.  If we could pull that off, many schemes for IP/ATM multicast
> shortcuts would become possible.
> Can you explain how you propose to do that?

One way to achieve this is to exchange reachability and distance information
among border routers (just as DVMRP routers on a shared IP subnet would do).
With such information, the border routers can "elect" one among themselves
as the forwarder for (all hosts on) a given IP network.

If you have a PNNI hierarchy, the highest level group leaders for the groups
that have at least one border router, can follow the above procedure to 
allocate external networks among themselves. Within each group that has 
multiple such border routers, the border routers (or lower level group leaders)
can further partition the IP networks allocated to that group and so on,
until each individual border router is left with a list of IP networks, for 
which it is the ingress router (forwarder) for traffic entering the ATM cloud.

As far as the question of "how border routers may exchange such information"
is concerned, something like the I-PNNI proposal in the ATM Forum might give 
us a solution, allowing the use of PTSEs for propagating IP routing information 
within an ATM cloud.

> 
> Yours,
> Joel M. Halpern                         [email-masked]
> Newbridge Networks Inc.
> 

Regards,

--Ajay Bakre

C&C Research Labs, NEC USA, Inc.
110 Rio Robles, San Jose, CA 95134
Phone: 408-943-3034, Fax: 408-943-3099
Email: [email-masked]