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.
| ● | 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]. |
| ● | 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. |
| ● | If required, you can exclude the "resource-priority” tag from the SIP Require header in INVITE messages for Tel-to-IP calls when MLPP priority call handling is used. This is configured using the RPRequired parameter. |
| ● | For a complete list of the MLPP parameters, see MLPP and Emergency Call Parameters. |
The Resource Priority value in the Resource-Priority SIP header can be any one of those listed in the table below.
For each MLPP call priority level, the Multiple Differentiated Services Code Points (DSCP) can be set to a value from 0 to 63.
MLPP Call Priority Levels (Precedence) and DSCP Configuration Parameters
|
MLPP Precedence Level |
Precedence Level in Resource-Priority SIP Header |
DSCP Configuration Parameter |
|---|---|---|
|
0 (lowest) |
routine |
MLPPRoutineRTPDSCP |
|
2 |
priority |
MLPPPriorityRTPDSCP |
|
4 |
immediate |
MLPPImmediateRTPDSCP |
|
6 |
flash |
MLPPFlashRTPDSCP |
|
8 |
flash-override |
MLPPFlashOverRTPDSCP |
|
9 (highest) |
flash-override-override |
MLPPFlashOverOverRTPDSCP |