It can also invite participants to already existing sessions, such as multicast conferences.
SIP, in combination with other protocols describes the session characteristics to potential session participants.
It supports 5 facets of establishing & terminating multimedia communications
These are:
- User Location: Determination of the end system to be used for communication.
- User Availability: Determination of the willingness of the called party to engage in communications.
- User Capabilities: Determination of media and media parameters to be used.
- Session Setup: Establishment of session parameters at both called & calling party.
- Session Management: This includes transfers & termination of sessions, modifying session parameters and invoking services.
