Re: Use of SAP in a PIM SSM Network

[Toerless Eckert <eckert@cisco.com>]

> I don't want to abandon completely the capability for global 
> shared trees, which I think will continue to be most appropriate
> for large numbers of low datarate sources, such as distributed
> simulations, as well as multicast-enabled games that were 
> "threatened" a few years ago.

I don't know. I think that access-control, management and
scalability requirements will make it more and more obvious, that
handling source-discovery at the network layer will not fly in
the Internet. Especially not with the unsolved address allocation
problem for application sessions.

I wonder why nobody thinks of session management with a standardizable
solution for a session/ application layer RP function to handle session.
An application programmer really does not care if "joining to a session as
a source and/or receiver" is done with IP Multicast alone, or
if there's a session library that will do this: 

    Contacting some RP-server, signal to the RP if you are a
    source, maybe also if you are active or also a receiver, and
    then have the library also join towards the active currently
    active sources for this session - as indicated by the RP.

Conferencing solutions using unicast are doing things along this 
line since the beginning of time, only that each application has
it's own solution for it, which takes away the ability to really
set up session management facilities in an application independent
way. Maybe i just don't know the solutions space well enough there,
but with something like this i really don't see a need for
"global source-discovery in an ad-hoc managed address space", which
is what we have today.

Cheers