P-CSCF refers to "Proxy Call Session Control Function". It is the first point of contact in the IMS network for the UE.

The roles of the P-CSCF include,

• It works as a proxy between the UE and the IMS network.

• Performs authentication and security for the UE, in order for the UE to be able to access the IMS network.

• Routes the SIP messages received from the UE to the appropriate IMS entity (e.g. I-CSCF or the S-CSCF).

• Enforces policies to the multimedia session (e.g. bandwidth allocation and QoS).