Multilevel Precedence And Preemption - AudioCodes Mediant 800 User Manual

CHAPTER 28 Configuring Supplementary Services
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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.
MLPP is typically used in the military where, for example, high-ranking personnel can preempt
active calls during network stress scenarios such as a national emergency or degraded network
situations.
MLPP can be enabled for all calls, using the global parameter, CallPriorityMode, or for specific calls
using the Tel Profile parameter, CallPriorityMode.
The feature is applicable to the following interfaces:
✔
FXO
✔
ISDN
✔
CAS
The device also identifies emergency calls if the Priority header of the incoming
SIP INVITE message contains the "emergency" value.
For Trunk 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].
If you are using a Tel Profile, you must configure the 'Call Priority Mode' parameter
in the Tel Profile table and on the Priority & Emergency page with the same value;
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.
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.
Mediant 800 Gateway & E-SBC | User's Manual
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