You define MLPP service domains at two levels:
On the Class of Restriction screen, where you then assign the COR to a telephone of a user
On the Multiple Level Precedence & Preemption Parameters screen, which applies to all resources on the server
The system uses the service domain to determine whether the system applies the preemption or precedence level of the caller to potentially preempt a routine call or another call of lower precedence. If an existing call has a different service domain than the service domain of the call that attempts a preemption, preemption is disallowed, regardless of the preemption levels of the two calls.
The two levels of service domain influence preemption and precedence capabilities in different ways, depending on which of the following resources the server recognizes as carrying the call:
Intraswitch routing to another telephone on the same server
Incoming ISDN-PRI trunks for a call that originates from another server on the network
Incoming non-ISDN-PRI trunks for a call that originates from another server on the network