H.245 alphanumeric support required?

Rich Bowen rkbowen at cisco.com
Wed Nov 11 17:01:35 EST 1998


Paul,

Thanks for clearing this up for me.

Rich
----------------------------------------------------------------------------
Richard K. Bowen                       Cisco Systems, Inc.
rkbowen at cisco.com                      Research Triangle Park, NC
----------------------------------------------------------------------------
Paul Long wrote:
>
> > From:         Rich Bowen[SMTP:rkbowen at CISCO.COM]
> > 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."
> >
> This was written back when "transmitted information" did not include H.245
> messages. It referred only to the streams of video, audio, and data. That's
> why it seems to contradict the following, which was added much later:
>
> > 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."
> >
> >    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?
> >
> The second one.
>
> > Can someone please clarify the requirements here?
> >
> First, the intent was that all H.323 terminals have at least a basic ability
> to signal "DTMF." In fact, this is a requirement. 6.2.8/H.323v2: "An H.245
> indication, userInputIndication, is available for transport of user input
> alphanumeric characters from a keypad or keyboard, equivalent to the DTMF
> signals used in analogue telephony... H.323 terminals shall support the
> transmission of user input characters 0-9, "*", and "#". Transmission of other
> characters is optional."
>
> All endpoints must be able to receive all of the H.245 messages, including
> userInputIndication (6.2.8/H.245v3: "H.323 terminals shall be capable of
> parsing all H.245 MultimediaSystemControlMessage messages..."); however, note
> that there is no requirement to do anything with this information on the
> receive side. Just like with the PSTN, it is up to special-purpose terminals
> to decide whether and how to interpret these signals, but all terminals are
> required to send them.
>
> Paul Long
> Smith Micro Software, Inc.



More information about the sg16-avd mailing list