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Figure 15-6
NCAUUI Invocation Rejection with a Q.931 RELease COMPlete Message
Originating PBX
SETUP (NCAUUI Request)
RELease w/cause of 29
"facility rejected"
RELease COMPlete
Network Rejection
The DMS-250 switch rejects a NCA-TSC request message with a Q.931
RELease, RELease COMPlete, or SCCP CREF message.
Note: A Q.931 RELease Message is sent if NCAUUI rejection occurs at the
CC. A Q.931 RELease COMPlete message is sent if NCAUUI rejection
occurs at the XPM.
Network rejection is handled in one of the following areas:
NCAUUI Invocation Rejection from the Originating XPM
Temporary Signaling Connection Blocks (TSCB) are data structures that are
allocated for NCAUUI calls at the originating and terminating XPM. There
are 127 TSCBs available per DTCI. If TSCBs are not available at the
originating XPM, the XPM rejects the NCA-TSC request message by
sending a Q.931 RELease COMPlete with a cause value of 42 "Switching
Equipment Congestion", location code of "Transit" and coding standard of
"CCITT" to the originating ISDN user.
Originating MCI DMS–250
Connection Request
Negative Acknowledgment at the Originating XPM
Negative Acknowledgment at the Originating DMS-250 switch
Negative Acknowledgment at the Originating SCCP
Negative Acknowledgment at the Terminating SCCP
Negative Acknowledgment at the Terminating DMS-250 switch
Negative Acknowledgment at the Terminating XPM
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
Terminating MCI DMS–250
CR
SETUP (NCAUUI Request)
RELease COMPlete w/cause of 29
CREF
Connection
Refused
NCAUUI 15-9
Terminating PBX
"facility rejected"
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