IMS S-CSCF Serving Call State Control Function

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

The IMS S-CSCF, or Serving Call State Control Function, is one of the major entities within the overall IMS architecture.

The IMS S-CSCF is at the core of many functions within an IMS network, communicating with many other functions within the overall system.

The S-CSCF undertakes a variety of actions within the overall system, and it has a number of interfaces to enable it to communicate with other entities within the overall system.

IMS S-SCSF basics

The Serving Call State Control Function, S-CSCF, is the main SIP session control node within the overall IMS network.

When a subscriber enters the network, the subscriber provides a contact address and a public user identity. This is provided to the S-CSCF.

These two elements of data are then linked in a process known as binding.

In view of its role within the IMS network, the S-CSCF is seen as the registrar for the network, although the HSS holds the data against which the S-CSCF checks the authenticity of the subscriber requesting entry.

S-CSCF interfaces

The S-CSCF interfaces with several other entities within the IMS network.

A diagram shwoing the IMS S-CSCF or Serving Call State Control Function interfaces
IMS S-CSCF Interfaces

By Ian Poole

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