Version 6.4 313 March 2012
SIP User's Manual 18. GW and IP to IP
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
Example (b): The detection of a Wink signal generates the following SIP INFO
message:
INFO sip:4505656002@192.168.13.40:5060 SIP/2.0
Via: SIP/2.0/UDP 192.168.13.2:5060
From: port1vega1 <sip:06@192.168.13.2:5060>
To: <sip:4505656002@192.168.13.40:5060>;tag=132878796-
1040067870294
Call-ID: 0010-0016-D69A7DA8-1@192.168.13.2
CSeq:2 INFO
Content-Type: application/broadsoft
Content-Length: 17
18.5.2.10.3 Pre-empting Existing Calls for E911 IP-to-Tel Calls
If the device receives an E911 call from the IP network destined to the Tel, and there are
unavailable channels (e.g., all busy), the device terminates one of the calls (arbitrary) and
then sends the E911 call to that channel. The preemption is done only on a channel
pertaining to the same Trunk Group for which the E911 call was initially destined and if the
channel select mode (configured by the ChannelSelectMode parameter) is set to other
than “By Dest Number” (0).
The preemption is done only if the incoming IP-to-Tel call is identified as an emergency
call. The device identifies emergency calls by one of the following:
The destination number of the IP call matches one of the numbers defined by the
EmergencyNumbers parameter. (For E911, you must defined this parameter with the
value "911".)
The incoming SIP INVITE message contains the “emergency” value in the Priority
header.
This feature is enabled by setting the CallPriorityMode parameter to “Emergency” (2).
Notes:
• This feature is applicable to FXO, CAS, and ISDN interfaces.
• For FXO interfaces, the preemption is done only on existing IP-to-Tel
calls. In other words, if all the current FXO channels are busy with calls
that were answered by the FXO device (i.e., Tel-to-IP calls), new
incoming emergency IP-to-Tel calls are rejected.
18.5.2.11 Multilevel Precedence and Preemption
The device's Multilevel Precedence and Preemption (MLPP) service can be enabled using
the CallPriorityMode parameter. MLPP is a call priority scheme, which does the following:
Assigns a precedence level (priority level of call) to specific phone calls or messages.
Allows higher priority calls (precedence call) and messages to preempt lower priority
calls and messages (i.e., terminates existing lower priority calls) that are recognized
within a user-defined domain (MLPP domain ID). The domain specifies the collection
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