SIP (Session Initiation Protocol) is a protocol used to initiate voice and/or video conversations over the internet.
SIP stands for Session Initiation Protocol and refers to a TCP/IP-based network protocol which can be used to establish and control communication connections of several subscribers. SIP is often used in Voice-over-IP telephony to establish the connection for telephone calls.
It brings together many of the ‘building blocks’ needed to make phone calls via an internet connection (VoIP calls). Through SIP, a connection forms between endpoints.