Frank,
H.450.1 is the framework for individual supplementary service specifications. Which messages will be used for supplementary service APDUs is specified in these individual specifications, subject to the rules of H.450.1. In particular:
- In the context of H.450, a Facility message needs a valid, agreed-upon call reference.
- Therefore the sender of Setup shall not send a Facility message before having received a positive response message (e.g. Call Proceeding, but obviously not Release Complete since the call reference would be no longer valid).
- The recipient of Setup shall not use Facility as first response message - note that supplementary service APDUs can be included in almost all other possible response messages.
The last bullet applies only to H.450 standards. It does not mean that Facility could not be the first response message for other purposes!
Ernst Horvath Siemens AG
-----Ursprüngliche Nachricht----- Von: Frank Derks [mailto:frank.derks@PHILIPS.COM] Gesendet am: Dienstag, 04. September 2001 14:28 An: ITU-SG16@mailbag.cps.INTEL.COM Betreff: Rules for sending H.450.1 APDUs
6.3/H.450.1 states (the third bullet item):
"a FACILITY message shall not be sent if a SETUP message previously sent or received has not been answered"
It is not clear what constitutes an answer to a SETUP message. Does this refer to any response that is the effect effect of sending or receiving a SETUP message? E.g. a SETUP ACKNOWLEDGE or a CALL PROCEEDING as "response" to having received a SETUP?
Regards,
Frank
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