Paul,
Like I said before, H.323 clearly states that a Setup cannot contain both a fastStart and h245Control component. Period. 8.2.1/H.323v3: "The calling endpoint >>>shall not<<< include both a fastStart element and encapsulated H.245 messages in h245Control in the same Setup message..." What part are people having trouble understanding?
That covers it for the calling EP. Q.931 is equally clear about what the called EP is required to do. 5.8.6.2/Q.931: "When a SETUP or RELEASE message is received which has one or more mandatory information elements with invalid content [e.g., fastStart and h245Control both present], a RELEASE COMPLETE message with cause No. 100, 'invalid information element contents' shall be returned."
If a calling EP had some way to determine which version the called EP was before it sent Setup, we could make this version-specific behavior (which has its own problems, remember), but since Setup is the first message, we cannot do this.
Paul Long Smith Micro Software, Inc.
-----Original Message----- From: Paul E. Jones [mailto:paulej@PACKETIZER.COM] Sent: Wednesday, May 31, 2000 12:29 AM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: On TD26 - Fast TCS and M/S negotiation in H.323v4
Pete,
If we could follow such logic, I would agree that this procedure would be worth perusing. Unfortunately, the inclusion of fastStart and tunneled H.245 messages in the SETUP message is not defined. There is no way to predict how a V2 device will behave when receiving these messages. I like the idea, but I'm afraid we will compromise backward compatibility by including it.
Let's assume a V2 device does *not* recognize the tunneled H.245 in SETUP (ignores it), but accepts the Fast Connect proposal. Assume, also, that in the CONNECT message, the endpoint includes the fastStart element *and* a tunneled TCS message. What could the calling endpoint *safely* assume?
Assume that CONNECT was the first message received following the SETUP if that helps complicate matters further for you. :-)
I just need further convincing.
Paul
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