Subject: Multiple sernder scenario

From: [email-masked] (Aman Devgan)
Date: Thu, 25 Feb 1999 16:53:30 -0500 (EST)

If two MADCAP clients request addresses for the same scope (TTL),
does the MADPCAP server lease the same multicast address to them both?
So if one of the many senders to a multicast group decides to leave and
generates a RELEASE, the MADCAP server should not release this multicast
address to be reused. Is this true? The draft-ietf-malloc-madcap-04.txt 
doesn't say much about how the MADCAP server manages the leases 
and addresses.

Also is there a mechanism (like a dedicated UDP port) by which addresses
in use within a scope are advertised to all hosts? Given enough information
the receivers can make an informed decision about which multicast group
to join. By the way, they will have to lease this group address from the
MADCAP server, right? This mechanism could also be used by other senders
to this group which can request lease on the address already in use for
this scope.

Thanks,
-- 
Aman Devgan

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From: Dave Thaler <[email-masked]>
Date: Thu, 25 Feb 1999 17:23:31 -0800 (PST)

> If two MADCAP clients request addresses for the same scope (TTL),

TTL scoping should not be used, only admin scoping.

> does the MADPCAP server lease the same multicast address to them both?

If the requests are for non-overlapping times, the server
is perfectly free to do so.

> address to be reused. Is this true? 

The MADCAP server will not release the address unless the client
identifier matches, so if client that allocated the address doesn't
give out the client identifier to any other sender, then the server
won't release it.  Additional access-control can be done if the
server supports IPsec, although user-based IPsec is needed before
it becomes really useful.

> The draft-ietf-malloc-madcap-04.txt 

From my understanding, that's because it's up to the implementation.

> in use within a scope are advertised to all hosts? 

That's what the SAP protocol is for.  Session advertisement is covered 
by the MMUSIC WG.

> Given enough information
> MADCAP server, right? 

No, only the session creator needs to lease the address.

-Dave

---

From: Aman Devgan <[email-masked]>
Date: Thu, 25 Feb 1999 20:24:39 -0500

If the session creator decides to leave the group while there are other
sources
active in this multicast group, does the MADCAP server release the group
address? The said active sources would then have to try to set up a new
session.

--
Aman

---

From: Dave Thaler <[email-masked]>
Date: Thu, 25 Feb 1999 19:25:07 -0800 (PST)

> address? The said active sources would then have to try to set up a new

No, the address allocation is unrelated to membership.
The session creator may never even join or send anything
to the group.  For example, you might allocate the address
from one machine and advertise the session far in advance.
When the start time arrives, you might participate in the
session on a different machine.

-Dave