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Figure 14-4
NCAUUI Invocation Rejection from Network
Originating PBX
Originating PBX
Originating PBX
NCAUUI Congestion and Flow Controls
NCAUUI supports two types of congestion control: user congestion and
network congestion flow control. The PRI user that receives a Q.931
Congestion Control message cannot distinguish whether the originator of the
message is the far-end user or the DMS-250 switch.
When necessary, the DMS-250 switch or the end user controls the transfer of
User Information messages by means of a Congestion Control message. The
Q.931 Congestion Control message contains a Congestion Level IE that can
be set to "Receiver Not Ready" indicating congestion or "Receiver Ready"
indicating congestion clearing. The Q.931 Congestion Control message also
contains an optional Cause IE.
SETUP (NCAUUI Request)
RELease COMPlete w/value cause of 42
"switching equipment congestion"
SETUP (NCAUUI Request)
RELease COMPlete w/value cause of 21
"call rejected"
RELease COMPlete
SETUP (NCAUUI Request)
RELease COMPlete w/value cause of 50
"requested facility not subscribed"
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
DMS-250
TSC RESOURCES ARE ALL BUSY
DMS-250
NOT ISDN PRI AGENCY
DMS-250
Originating
user not
subscribed
NCAUUI 14-7
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