Emergency E911 Phone Number Services; Pre-Empting Existing Calls For E911 Ip-To-Tel Calls; Multilevel Precedence And Preemption - AudioCodes MP-11x User Manual

25.10 Emergency E911 Phone Number Services

This section describes the device's support for emergency phone number services.

25.10.1 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 Hunt Group for which the E911 call was initially destined and if the
channel select mode (configured by the ChannelSelectMode parameter) is set to a value
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 Priority header of the incoming SIP INVITE message contains the "emergency"
value.
Emergency pre-emption of calls can be enabled for all calls, using the global parameter
CallPriorityMode, or for specific calls using the Tel Profile parameter CallPriorityMode.
Notes:
•
For Hunt Groups configured with call preemption, all must be configured to MLPP
[1] or all configured to Emergency [2]. In other words, you cannot set some trunks
to [1] and some to [2].
•
The global parameter must be set to the same value as that of the Tel Profile
parameter; otherwise, the Tel Profile parameter is not applied.
•
If you configure call preemption using the global parameter and a new Tel Profile
is subsequently added, the TelProfile_CallPriorityMode parameter automatically
acquires the same setting as well.
•
This feature is applicable to FXO 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.

25.11 Multilevel Precedence and Preemption

The device supports Multilevel Precedence and Preemption (MLPP) service. MLPP is a
call priority scheme, which does the following:

Assigns a precedence level (priority level) 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
of devices and resources that are associated with an MLPP subscriber. When an
MLPP subscriber that belongs to a particular domain places a precedence call to
another MLPP subscriber that belongs to the same domain, MLPP service can
preempt the existing call that the called MLPP subscriber is on for a higher-
precedence call. MLPP service availability does not apply across different domains.
User's Manual 292
MP-11x & MP-124
Document #: LTRT-65432