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15-8 NCAUUI
message. The cause value received and this clearing message is propagated
to the originating ISDN user.
Note: If the terminating switch receives a Q.931 DISConnect, RELease, or
RELease COMPlete message for NCAUUI invocation rejection, the
terminating switch builds and sends an SCCP CREF message to the
originating switch.
For example, if the terminating ISDN user negatively acknowledges the
request for NCAUUI with the Q.931 DISConnect or RELease message with
cause value of 29 "Facility Rejected", the terminating DMS-250 switch
sends a Q.931 RELease COMPlete message to the terminating ISDN user
and an SCCP CREF message to the originating switch.
If the NCA-TSC request message receives a negative acknowledgment at the
far end, the originating switch receives an SCCP CREF message. Once the
originating switch receives an SCCP CREF message, a Q.931 RELease
message is sent to the originating ISDN user to indicate negative
acknowledgment of the NCA-TSC request message.
Figure 15-5
NCAUUI Invocation Rejection with a Q.931 DISConnect or RELease Message
Originating PBX
SETUP (NCAUUI Request)
RELease w/cause of 29
"facility rejected"
RELease COMPlete
If the terminating ISDN user negatively acknowledges the request for
NCAUUI with the Q.931 RELease COMPlete message, the terminating
switch sends an SCCP CREF message to the originating switch.
If the NCA-TSC request message receives a negative acknowledgment at the
far end, the originating switch receives an SCCP CREF message. Once the
originating switch receives an SCCP CREF message, a Q.931 RELease
message is sent to the originating ISDN user to indicate negative
acknowledgment of the NCA-TSC request message.
297-2521-106 Standard 23.01 March 2001
Originating MCI DMS–250
CR
Connection Request
CREF
Connection
Refused
Terminating MCI DMS–250
SETUP (NCAUUI Request)
DISConnect/RELease w/cause
29 "facility rejected"
RELease COMPlete
Terminating PBX
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