Invitation via Gatekeeper

Chris Purvis CPurvis at MADGE.COM
Thu Mar 4 06:46:59 EST 1999


Yes, it is splendidly unclear, isn't it?

> I tried to get answer from implementors group and some other
> person, but I couldn't get any satisfiable answer.
> My question is here.
> In section 28/H.323-Non-MC invite signalling),

It's worth mentioning which standard here.  For the benefit of anyone
needing to catch up, we're talking about H.323.

> when an
> endpoint(E1) which do not have active MC wants to invite other
> endpoint(E3), does E1 send an ARQ to its Gatekeeper for the invite or
> does E2 send the ARQ to its gatekeeper, or do both of them send ARQ's?

I would suggest that both ought to send ARQs.  Both are logically setting up
calls, so both need to ask permission.  However, E1's ARQ need ask for no
bandwidth as none will be used on the call between it and E2.

> And, when Gatekeeper doesn't know which endpoint has active MC in any
> conference, what should Gatekeeper do if it receives ARQ(for
> invitation)
> from an endpoint which do not have active MC? I mean, if Gatekeeper
> receives ARQ from E1, what should Gatekeeper do? Does Gatekeeper send
> ACR with E2's CallTransportAddress instead of E3's
> CallTransportAddress?

E1's gatekeeper can conceivably spot that invite is probably what's wanted,
by matching up conferenceIDs, although there's nothing in the ARQ message to
say directly that invite is the desired outcome.  The gatekeeper certainly
MUST return the address to which E1 should send its Setup message, so in the
direct-routed model that will be E2.  However, a non-routing gatekeeper will
have no way of knowing where the active MC is.  I believe this is a genuine
"hole" in the standard.


I know you've implemented some of this stuff: how do you get around this?

Dr Chris Purvis - Senior Development Engineer, WAVE CC Software
Madge Networks Ltd, Wexham Springs, Framewood Road, Wexham, Berks.  ENGLAND
Phone: +44 1753 661 359  email: cpurvis at

More information about the sg16-avd mailing list