IMS P-CSCF Proxy Call State Control Function

- details for the function, operation and implementation of the IMS P-CSCF, Proxy Call State Control Function.

IMS, IP multimedia subsystem tutorial includes:

    •  IMS tutorial
    •  IMS architecture
    •  IMS HSS
    •  IMS S-CSCF
    •  IMS P-CSCF
    •  IMS I-CSCF
    •  IMS layers & stack

The P-CSCF is the user to network proxy. In this respect all SIP signalling to and from the user runs via the P-CSCF whether in the home or a visited network.

P-CSCF basics

When any user registers with the IMS network, the registration signalling will pass through the P-CSCF.

For instances where a subscriber has more than one active terminal, these may communicate and pass registration requests through different P-CSCFs, but the same S-CSCF will always be used. This is because the HSS will provide data to use the same S-CSCF regardless of which I-CSCF presents the requests.

By Ian Poole

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