What Is SIP Trunking?
SIP (Session Initiation Protocol) is an application layer control protocol for creating, modifying, and terminating sessions with one or more participants.
These sessions include telephone calls, multimedia distribution, multimedia conferences and presence.
SIP trunking is a term applied to the services offered by carriers and service providers to terminate Voice over IP (VoIP) calls to the Public Switched Telephone Network (PSTN).
SIP trunking allows enterprises and small businesses to eliminate a PSTN gateway at their site and outsource that function to a carrier. It is typically a lower-cost alternative to Primary Rate Interfaces (PRIs) because SIP trunks can be purchased in single-trunk increments.