SIP (Session Initiation Protocol)

The Session Initiation Protocol, defined in RFC 3261, is the IETF signalling protocol used to create, modify, and terminate multimedia sessions over IP. It is the control plane of VoIP, IMS, VoLTE/VoNR, and RCS, and runs over UDP, TCP, or TLS. SIP is text-based and extensible, which makes it powerful but also exposes a wide attack surface: registration hijacking, INVITE flooding, toll fraud, response splitting, and CLI spoofing. TLS for transport, SIP digest or AKA authentication, and STIR/SHAKEN for caller verification are standard mitigations.

Categories: Radio Access NetworkSignalingSecurity Controls

SIP in context

The radio access network is where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations and downgrade attacks; defenses rest on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

Signaling protocols carry the control-plane messages that set up calls, register subscribers and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA as top-tier telecom risk.

To place SIP in the wider telecom-security picture, review 1G, ITU, Lawful Interception, RADIUS, RTP and TCP — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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