VoIP-specific KPIs are as follows:

Denotes the probability that the terminal cannot register towards IMS when requested.

Denotes the time elapsing from the IMS registration request until the terminal is registered to IMS.

Denotes the probability that the terminal cannot set up an MTSI session. An MTSI session setup is initiated when the user presses the "call" button and concludes when the user receives, within a predetermined time, a notification that the callee has answered.

Denotes the time elapsing from initiation of an MTSI session until a notification is received that the session has been set up.

Denotes the probability that a successfully set up MTSI call is ended by a cause other than intentional termination by either party.