P-CSCF

proxy-call session control function

An IMS SIP server that is the first point of contact in a VoLTE call. The P-CSCF has the following functions:

• forwards SIP messages to other IMS nodes and to the UE

• interacts with the PCRF for billing and policy rules

• maintains a security association with the UE

• detects and forwards emergency calls to the local E-CSCF