SIP (Session Initiation Protocol) is the standard protocol for establishing, managing, and terminating voice and video sessions over IP networks. It is the foundation for VoIP communications and connects voice AI systems to telephone networks.
How does SIP work?
SIP handles signaling for call setup and teardown, including locating participants, negotiating session parameters, and managing call state. The actual audio travels via a separate protocol (typically RTP). SIP trunks connect VoIP systems to the PSTN, enabling AI voice agents to make and receive standard phone calls.
Why does SIP matter for voice AI?
SIP is the standard interface between voice AI platforms and telephone infrastructure. Understanding SIP enables proper integration, troubleshooting connectivity issues, and optimizing call quality. Most enterprise voice systems and all major carriers use SIP.
SIP in practice
A voice AI platform receives calls via SIP trunks from a carrier. When a call arrives, SIP signaling establishes the session and negotiates audio parameters. The AI answers, and audio flows bidirectionally. When the call ends, SIP handles the termination. All standard phone features work transparently over SIP.