P-CSCF (Proxy Call Session Control Function)

Also known as: Proxy CSCF, Proxy Call Session Control Function

P-CSCF is the first SIP contact point for an IMS user equipment on the Gm interface. It forwards SIP requests toward the home IMS, enforces media policy with the PCRF/PCF over Rx/N5, and terminates the IPsec security association negotiated during IMS-AKA registration. Attacks that target the P-CSCF include SIP flooding, malformed message fuzzing, and attempts to bypass access-side signalling security when it is co-located with the SBC.

Categories: SignalingSecurity ControlsInternet and Routing

P-CSCF in context

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.

Security controls span signaling firewalls (SS7/Diameter/GTP screening), transport encryption (IPsec, TLS, PRINS), identity and access on OSS/BSS, and monitoring at both packet and log level. Controls are audited against GSMA FS.11/FS.19/FS.20/FS.36.

To place P-CSCF in the wider telecom-security picture, review Integrity, Signaling Firewall, Trunk, MGCF, Satellite Backhaul and Diameter Interconnect Security: each entry cross-references back to this page so you can walk the topic in either direction.

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