What does 'exchange' mean and which H.245 message gets to be sent first?

Frank Derks frank.derks at PHILIPS.COM
Tue Apr 3 11:32:36 EDT 2001


Vladimir,

With H.450 apdus to be sent within H.323 versions up to v3 your may choose
not to include the Facility-UUIE construct at all (but set the "empty"
h323-message-body choice instead). The disadvantage with this is that for
such messages you miss the Call Identifier. Therefore, it has been agreed to
make the Facility-UUIE mandatory with H.323v4, even if only H.450 would have
to be transmitted in the H.225.0 message (mainly to get the call
identifier).

Since the FacilityReason is mandatory in Facility-UUIE, you have to select a
reason that fits best to the situation. E.g. use "routeCallToMc" if your
scenario is an H.450.2 Transfer to an MCU or use starth245 in conjunction
with a FACILITY that also contains an H.450.3  callReroute.Inv if this is
what you want to achieve, etc. If none of the reasons are suitable, the new
value "transportedInformation" I guess is intended to be used. Value
undefinedReason should be accepted always.

However, H.225.0 v4 clause 7.4 (third para, last sentense) is misleading,
since someone may interpret that the only FacilityReason that is allowed in
conjunction with transmitted H.450 apdus may be the new value
transportedInformation, which would limit combination of applications
significantly.
Therefore, the sentense should be rewored to say:
"...
In H.225.0 version 4 and higher, a sender of an H.450 apdu shall include a
Facility-UUIE carrying a callIdentifier field in every Facility message. The
FacilityReason field should be set to value transportedInformation if no
other reason fields are suitable."

I propose to add this clarification to the v4 Implementers Guide.

Regards,
Karl Klaghofer


-----Ursprüngliche Nachricht-----
Von: Vladimir Burlik [mailto:vladbph at home.com]
Gesendet: Dienstag, 3. April 2001 04:14
An: imtch323implementors at mail.imtc.org
Betreff: [imtch323implementors] Facility reason


Hello all,
Could somebody tell me what facility reason should be used when transferring
supplementary services messages?
For example CallRerouting.Invoke?

Thanks
Vlad



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