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15-2 NCAUUI
When the terminating DMS-250 switch receives an SCCP Class 2
Connection Request (CR) message, it builds and sends the Q.931 SETUP
message. The Q.931 message indicates the presence of NCAUUI to the
terminating ISDN user based on the TTG received in the SCCP Class 2 CR
message.
The user at the terminating end can acknowledge the NCAUUI request with
a Q.931 CONNect message. Once the terminating DMS-250 switch receives
a Q.931 CONNect message, it generates and sends a Q.931 CONNect
ACKnowledgment message to the terminating ISDN user and SCCP Class 2
Connection Confirm (CC) to the originating DMS-250 switch. When the
originating switch receives the SCCP Class 2 CC message, it formulates and
sends a Q.931 CONNect message to the originating ISDN user. At this
point, a NCA-TSC virtual connection has been established.
Once a NCA-TSC has been successfully established, either PRI user may
send User Information messages. No attempt is made by the switch to
interpret the contents of the User Information messages.
Non Call Associated User-to-User Signaling Invocation
The incoming Q.931 SETUP message must have valid Bearer Capability
and Channel Identification, in order for a NCAUUI request to be recognized
by the DMS-250 switch.
Incoming Q.931 SETUP messages received without the NCAUUI defined
Bearer Capability Information Element and Channel Identification
Information Element are not considered NCAUUI requests, therefore are
handled by way of regular call processing.
The call reference that the PBX receives in the NCAUUI SETUP message
must contain a valid call reference. Global or null call references are not
supported for feature invocation.
When the originating DMS-250 switch receives the Q.931 SETUP message
and receives an ADF response from the DAP, the following criteria is
verified before an SCCP Connection Request (CR) message is sent to the
terminating switch:
297-2521-106 Standard 23.01 March 2001
Table C7LOCSSN datafill for the local Non-Call Associated
User-to-User Service (NCAUUS) subsystem is present.
Table SCCPDEST datafill for the TSID returned from the DAP is
present.
Table C7RTESET datafill for the terminating routeset for the TSID is
present.
The C7NETSSN datafill for the NCAUUS subsystem at the terminating
routeset is present.
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