SIP

Technical Explanation

SIP is the universal protocol for telecom call signaling. Smartphones exchange SIP messages (INVITE, 180 Ringing, 200 OK, BYE) with IMS servers to set up VoNR calls, negotiate voice/video codecs via SDP, and manage supplementary features like conference calling and hold.

Key Functions

• Establishes, negotiates, and tears down VoNR voice and video calls
• Carried over dedicated IMS PDU session using high-priority 5QI 5
• Transports Session Description Protocol (SDP) parameters for codec negotiation