multicast-transition

[Dirk Ooms <Dirk.Ooms@alcatel.be>]

Hi all,

I was wondering whether anyone ever considered to apply techniques,
similar to the ones defined in ngtrans for ipv6, to ip multicast.  At
the moment one needs to configure static tunnels to connect to the MBone
over a non-multicast network.  Wouldn't it be good to investigate how
senders and/or receivers can hook up automatically to the MBone (without
the requirement of somebody in the MBone configuring a tunnel to your
network).

So, the concept of tunnel brokers might be useful: potential senders or
receivers can request a tunnel to a tunnel broker.  This requires some
boxes at the border of the MBone that are willing to
encapsulate/decapsulate, possibly take the role of DR (maybe one can
find broadcasters that want to sponsor such boxes).

Automatic tunneling might be another mechanism helping the deployment of
multicast.  In SSM, one could consider mechanisms as the following one
(I know it impacts the current model, but I think it's also pretty cool,
so maybe someone else might come up with variants that diminish the
impact):

At the SSM meeting in Pittsburg Doron Rajwan presented the idea to
extend IGMP to enable SSM-senders to check whether there are any
receivers for their data.  As an alternative one could consider to
terminate the PIM messages on the senders themselves (this would be a
scaled down PIM-stub with very limited functionality).  Once this
principle of terminating PIM at the SSM-sender would be accepted, one
can easily create automatic tunnels: again a number of special boxes are
placed at the border of the MBone, which will inject a default route
into the Mbone (the MRIBs will have a default route).  So (S,G) PIM
Joins with an S that is not part of the multicast topology will follow
the default route and will end up in this special border box.  The box
consults its RIB and tunnels the PIM Join to the sender S.  By looking
at the source of the outer IP header the sender knows where it has to
tunnel its multicast data to.

The above mechanism would allow that anyone can send to the MBone by
just downloading an application (no need to have a multicast router or
to configure a tunnel).  In ISM it was required that a sender sends its
data to the DR of the sender to be able to be discovered by the
receivers (via flooding or via an RP), but in SSM this is not necessary
anymore since out-of-band signaling is used.

In ngtrans there is another group of mechanisms beside tunneling, which
are the translators.  This could be another topic to investigate: how
can a unicast-only host hook up to a multicast distribution via a
special translator box.

Any comment?

dirk

-- 
Dirk Ooms                       mailto:dirk.ooms@alcatel.be
                                tel:+32 3 2404732
Network Strategy Group (NSG)    http://www.rc.bel.alcatel.be/nsg
Alcatel                         http://www.alcatel.com