SIP (Session Initiation Protocol)
The standard protocol for initiating, maintaining, and terminating real-time communication sessions over the internet.
SIP (Session Initiation Protocol) is the standard signaling protocol used to initiate, manage, and terminate real-time communication sessions — including VoIP phone calls. It is the underlying protocol that connects AI voice agent platforms to the public telephone network (PSTN) and to existing phone infrastructure.
SIP defines how call setup messages are exchanged between devices (phones, PBX systems, SIP trunks) and servers. Once a call is established, the actual audio is transmitted separately using RTP (Real-Time Transport Protocol).
SIP in AI voice agent deployments
- SIP trunking: The most common way to connect a business phone system to an AI voice agent platform. A SIP trunk delivers phone calls over an internet connection, replacing traditional analog or ISDN phone lines.
- Direct SIP integration: Enterprise deployments often connect TurboCall directly to an on-premise PBX or UCaaS platform (like Cisco, Avaya, or Zoom Phone) via a SIP trunk.
- BYON (Bring Your Own Number): TurboCall supports connecting existing phone numbers via SIP, so businesses keep their established numbers while switching their call handling to AI.
SIP vs. PSTN: The Public Switched Telephone Network (PSTN) is the traditional circuit-switched telephone infrastructure. SIP-based calls travel over the internet (VoIP) and are converted to PSTN format at a carrier's edge when calling traditional landlines or mobiles.