AudioCodes Mediant 3000 User Manual page 394

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.
Notes:
The Resource Priority value in the Resource-Priority SIP header can be any one of those
listed in the table below. A default MLPP call Precedence Level (configured by the
SIPDefaultCallPriority parameter) is used if the incoming SIP INVITE or PRI Setup
message contains an invalid priority or Precedence Level value respectively. 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
0 (lowest)
2
4
6
8
9 (highest)
The device automatically interworks the network identity digits (NI) in the ISDN Q.931
Precedence Information Element (IE) to the network domain subfield of the INVITE's
Resource-Priority header, and vice versa. The SIP Resource-Priority header contains two
fields, namespace and priority. The namespace is subdivided into two subfields, network-
domain and precedence-domain. Below is an example of a Resource-Priority header
whose network-domain subfield is "uc", r-priority field is "priority" (2), and precedence-
domain subfield is "000000":
Resource-Priority: uc-000000.2
The MLPP Q.931 Setup message contains the Precedence IE. The NI digits are presented
by four nibbles found in octets 5 and 6. The device checks the NI digits according to the
translation table of the Department of Defense (DoD) Unified Capabilities (UC)
Requirements (UCR 2008, Changes 3) document, as shown below:
User's Manual
•
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.
Precedence Level in
Resource-Priority SIP Header
routine
priority
immediate
flash
flash-override
flash-override-override
DSCP Configuration Parameter
MLPPRoutineRTPDSCP
MLPPPriorityRTPDSCP
MLPPImmediateRTPDSCP
MLPPFlashRTPDSCP
MLPPFlashOverRTPDSCP
MLPPFlashOverOverRTPDSCP
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Mediant 3000
Document #: LTRT-89729