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NCAUUI 15-5
CONNect message to the originating ISDN user to indicate positive
acknowledgment of the NCA-TSC request message.
CAUUI2 and CAUUI3 Requests
If the DMS-250 switch receives CAUUI2 requests in the NSF IE included in
the Q.931 SETUP message requesting NCAUUI, the DMS-250 switch
rejects the CAUUI2 request. The rejection is done by sending a Q.931
FACility REJect message with a cause value of 29 "Facility Rejected",
location code of "Transit", and coding standard of "CCITT" to the
originating ISDN user. The request for NCAUUI is still considered valid.
IF the DMS-250 switch receives a CAUUI3 request within a Q.931 FACility
message from either the originating or the terminating ISDN user, the
DMS-250 switch does not report the Q.931 FACility message to the far end
user. If this message is received before the first call clearing message, a
Q.931 FACility REJect message with a cause value of 29 "Facility
Rejected", location code of "Transit", and coding standard of "CCITT" is
sent to the sender of the Q.931 FACility message.
Connect Timers
T310 Timer
The T310 timer tracks the Q.931 SETUP message that is sent to the
terminating ISDN user. The terminating DMS-250 switch waits to receive a
Q.931 CONNect message indicating a connection. The default for this timer
is 10 seconds. After the Q.931 SETUP message is sent to the terminating
ISDN user, the DMS-250 switch moves into the Call Received network state
(N7) and timer T310 is started. The timer is stopped when the DMS-250
switch receives the Q.931 CONNect message. The T310 timer is datafilled
in table ISDNPROT. However, datafilling timer T310 in table ISDNPROT
affects all PRI calls for that protocol variant and not just NCAUUI calls.
If the T310 timer expires before the DMS-250 switch receives the Q.931
CONNect message, the terminating DMS-250 switch sends a Q.931
RELease COMPlete message with cause value of 102 "Recovery on Timer
Expiry" to the terminating ISDN user and an SCCP Connection Refused
(CREF) message to the originating DMS-250 switch. Once the originating
switch receives the SCCP CREF message, a Q.931 RELease message with a
cause value of 18 "No User Responding" is sent to the originating ISDN
user.
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
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