AudioCodes Media Pack MP-11x, User Manual

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User's Manual 294 Document #: LTRT-65432
MP-11x & MP-124
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Reason: preemption ;cause=3 ;text=”Generic Preemption”
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Reason: preemption ;cause=4 ;text=”Non-IP Preemption”
This Reason cause code indicates that the session preemption has occurred in a non-
IP portion of the infrastructure. The device sends this code in the following scenarios:
•
The device performs a network preemption of a busy call (when a high priority
call is received), the device sends a SIP BYE or CANCEL request with this
Reason cause code.
•
The device performs a preemption of a B-channel for a Tel-to-IP outbound call
request from the softswitch for which it has not received an answer response
(e.g., Connect), and the following sequence of events occurs:
a. The device sends a Q.931 DISCONNECT over the ISDN MLPP PRI to the
partner switch to preempt the remote end instrument.
b. The device sends a 488 (Not Acceptable Here) response with this Reason
cause code.

Reason: preemption; cause=5; text=”Network Preemption”
This Reason cause code indicates preempted events in the network. Within the
Defense Switched Network (DSN) network, the following SIP request messages and
response codes for specific call scenarios have been identified for signaling this
preemption cause:
•
SIP:BYE - If an active call is being preempted by another call
•
CANCEL - If an outgoing call is being preempted by another call
•
480 (Temporarily Unavailable), 486 (User Busy), 488 (Not Acceptable Here) -
Due to incoming calls being preempted by another call.
The device receives SIP requests with preemption reason cause=5 in the following
cases:
•
The softswitch performs a network preemption of an active call - the following
sequence of events occurs:
a. The softswitch sends the device a SIP BYE request with this Reason cause
code.
b. The device initiates the release procedures for the B-channel associated
with the call request and maps the preemption cause to PRI Cause = #8
‘Preemption’. This value indicates that the call is being preempted. For PRI,
it also indicates that the B-channel is not reserved for reuse.
c. The device sends a SIP 200 OK in response to the received BYE, before the
SIP end instrument can proceed with the higher precedence call.
•
The softswitch performs a network preemption of an outbound call request for the
device that has not received a SIP 2xx response - the following sequence of
events occur:
a. The softswitch sends the device a SIP 488 (Not Acceptable Here) response
code with this Reason cause code. The device initiates the release
procedures for the B-channel associated with the call request and maps the
preemption cause to PRI Cause = #8 ‘Preemption’.
b. The device deactivates any user signaling (e.g., ringback tone) and when
the call is terminated, it sends a SIP ACK message to the softswitch.
25.11.2 Precedence Ring Tone
You can assign a ring tone that is defined in the CPT file to be played when a precedence
call is received from the IP side. This is configured by the PrecedenceRingingType
parameter.
Emergency Telecommunications Services (ETS) calls (e.g., E911) can be configured with
a higher priority than any MLPP call (default), using the E911MLPPBehavior parameter.