H.245 alphanumeric support required?

Rich Bowen rkbowen at cisco.com
Tue Nov 10 10:04:20 EST 1998


Hello experts,

H.323 v2 section 6.8.2.1 says, "Transmitters shall limit the content
of their transmitted information to that which the receiver has
indicated it is capable of receiving."  On the other hand, H.245 v3
section 7.12.6 says, "Endpoints shall use the alphanumeric indication
to convey DTMF user input if the other endpoint has not indicated
the ability to receive DTMF using UserInputCapability."

These two statements seem to be in conflict since H.245 v3 seems
to be saying that the endpoint is required to send alphanumeric
user input regardless of whether the remote endpoint has indicated
its ability to receive input in that format.  The only ways I can
see to reconcile these two statements are to assume either:

   o Every endpoint is required to indicate capability of
     receiving alphanumeric user input (not likely), or --

   o Every endpoint is assumed to have the capability to
     accept alphanumeric user input; i.e., each endpoint
     *implicitly* indicates that it has this capability.  Or --

   o I'm interpreting H.245 v3 too strictly.  What it really
     means is that endpoints shall use alphanumeric if the
     remote endpoint did not indicate DTMF capability but it did
     indicate alphanumeric capability; otherwise don't send user
     input at all.

Is any of these interpretations correct?  Can someone please
clarify the requirements here?

Thanks,
Rich
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Richard K. Bowen                       Cisco Systems, Inc.
rkbowen at cisco.com                      Research Triangle Park, NC
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