SIP 기능

The Session Initiation Protocol (SIP) is an application-layer control

protocol that can 

1. establish, 

2. modify and terminate multimedia sessions

3. or calls. These multimedia sessions include multimedia conferences,

distance learning, Internet telephony and similar applications. 

SIP can invite both persons and "robots", such as a media storage

service. SIP can invite parties to both unicast and multicast

sessions; the initiator does not necessarily have to be a member of

the session to which it is inviting. Media and participants can be

added to an existing session.