Chris,
I think you see my point, then. Now that I think about it, an EP _is_ required to at least send its TCS, if it has not already, if it receives an H.245 request message. Specifically, it cannot send the TCSAck until it has sent its own TCS, according to the following:
8.2/H.323v3: "Endpoint system capabilities are exchanged by transmission of the H.245 terminalCapabilitySet message. This capability message shall be the first H.245 message sent."
And then there's the following. I think it means that if an EP receives TCS without already having sent TCS itself, it shall do so now. Is that your understanding?
8.2/H.323v3: "An endpoint which receives a terminalCapabilitySet message from a peer prior to initiating capabilities exchange shall respond as required by 6.2.8.1, and should initiate and successfully complete capabilities exchange with that peer prior to initiating any other procedure."
So if an EP initiates H.245 procedures, the remote is forced to also perform H.245 procedures. Okay, that's what I was looking for. Maybe it just means that it has to perform the cap exchange. You know, both sides don't really need to initiate the MSD. It's enough that the side that first wanted to use H.245 procedures has performed it, so TCS alone is enough of a prelude to get the H.245 session up and running. Do you think this needs clarification text?
Paul Long Smith Micro Software, Inc.
-----Original Message----- From: Chris Wayman Purvis [mailto:cwp@isdn-comms.co.uk] Sent: Monday, April 03, 2000 8:00 AM To: Paul Long Subject: Re: Force remote to start H.245 session?
Paul,
First of all, sorry for the fact that this seems to be a week-old mail I'm finally responding to...
I may have misunderstood, but I don't understand why this is necessary. If both endpoints have expressed willingness to use tunnelled H.245, why can an endpoint not simply start sending H.245 messages (of COURSE starting with TCS, and potentially tunnelled in purpose-built FACILITY messages) when it wishes to start a tunnelled H.245 session? I would have thought that would be a pretty clear indication of intent to start a tunnelled H.245 session!
FACILITY/reason=startH245 is required for separate H.245 connections because an endpoint may not know an address at its interlocutor to use to initiate an H.245 connection. This problem doesn't exist in tunnelled H.245, so I see no necessity for the extra interpretation!
We may want some extra text specifying behaviour at the start of an H.245 session, to ensure that the destination of the initial tunnelled H.245 message actually does something constructive (sends a TCS) rather than non-constructive (merely Acking the TCS it's been sent and not advancing anything useful).
Regards, Chris