User's Manual 536 Document #: LTRT-89730
Mediant 3000
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.
27.6.2 Precedence Ring Tone
You can configure the duration for which the device plays a preemption tone to the Tel and
IP sides if a call is preempted, using the PreemptionToneDuration parameter.
27.7 Detecting Collect Calls
The device detects collect calls (reverse charge calls) using any of the following
information elements (IE) in the received Q.931 ISDN Setup message for Tel-to-IP calls:
Reverse Charging Indication IE
Facility IE
When the device detects a collect call, it adds a proprietary header (X-Siemens-Call-Type:
collect call) to the outgoing SIP INVITE message.
This support does not require any configuration and is applicable to the Euro ISDN protocol
variant.
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