Doug,
If you don't like Paul's solution (it does have the flaw that a device controlled by UIIs looks like something that doesn't terminate the call - not that I see WHY that is a problem), then you do have an alternative. If you don't know the capabilities of the final destination of the call by this point you won't lose a lot by using good old-fashioned H.245-in-a-separate-TCP-stream!
Regards, Chris
Douglas Clowes wrote:
Paul,
Ugly! That leaves open the decision, for the receiver of the TCS, of when you give up on a call because you do not have compatible capabilities.
I can see that an empty-ish TCS could be distinguished from a TCS that isn't empty, but contains codecs I can't match. But how many EPs out there would already appreciate the distinction? If I send TCS 0.5, will my peer drop the call?
Ugly!
Douglas
At 21:13 04/11/2000 -0600, Paul Long wrote:
Regarding Douglas' concern, regardless of whether "an EP _should_ be able to ack a received message, even before sending TCS" (emphasis mine), the fact remains that it _shall not_ do this, except when indicating that it understands earlyH245Control. The solution to the particular problem he mentions is for the endpoint to send an "almost empty" TCS, or "TCS=0.5" :-). All it contains is sequenceNumber, protocolIdentifier, and--here's the important part--multiplexCapability. In particular, it doesn't need to contain capabilityTable or capabilityDescriptors, and the multiplexCapability can provide only minimal information. Including multiplexCapability means that it is not an empty TCS and therefore cannot be mistaken for one, but the endpoint also does not need to know its eventual capabilities at call-startup time.
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