Chris and Soo, my comments are inserted below (and marked with <Linh>). Hope, they help clarify the scenario you are looking for. Linh --- TRUONG Hong Linh hlt@zurich.ibm.com IBM Zurich Research Laboratory tel : +41 1 724 8434 CH-8803 Rueschlikon / Switzerland fax : +41 1 724 8955 _______________________________________________ Soo, 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 8.4.3.2(Figure 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. <Linh> Here I think we have to distinguish carefully between an endpoint and an MC (what the current H.323 achieves very badly!). In the above scenario, the MC is hosted in the same device as E2 and E1 is sending the SETUP message to the MC and not to E2 (H.323 Figure 28-30 are misleading, because they only show E2 and not the MC!). Therefore, IMO only E1 has to send an ARQ, not E2, and an MC never sends ARQ!
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. Linh, I know you've implemented some of this stuff: how do you get around this? <Linh>The point here is in general the GK does not (and needs not) know where the MC is actually located! It therefore, in response to the ARQ sent by E1, returns the transport address of either E3 (direct model) or itself (GK-routed model). In both cases, E1 has to send its SETUP message to the MC (which is in our specific scenario colocated with E2).Then the MC will relay that message to either E3 or the GK, depending on which transport address is included in the SETUP message sent by E1. Regards, Chris -- 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@madge.com