5 General Architecture

29.2283GPPIP Multimedia (IM) Subsystem Cx and Dx InterfacesRelease 17Signalling flows and message contentsTS

This clause further specifies the architectural assumptions associated with the Cx reference point, building on TS 23.228 [1] and also the Px reference point building upon TS 23.141 [10].

5.1 Functional requirements of network entities

5.1.1 Functional requirements of P-CSCF

There is no requirement for the interaction between the P-CSCF and the HSS.

5.1.2 Functional requirements of I-CSCF

The I-CSCF communicates with the HSS over the Cx interface.

For functionality of the I-CSCF refer to TS 23.002 [4].

5.1.3 Functional requirements of S-CSCF

The S-CSCF communicates with the HSS over the Cx interface.

For functionality of the S-CSCF refer to TS 23.002 [4].

5.1.4 Functional requirements of HSS

The HSS communicates with the I-CSCF and the S-CSCF over the Cx interface.

For functionality of the HSS refer to TS 23.002 [4].

5.1.5 Functional classification of Cx interface procedures

Operations on the Cx interface are classified in functional groups:

1. Location management procedures

– The operations regarding registration and de-registration.

– Location retrieval operation.

2. User data handling procedures

– The download of user information during registration and to support recovery mechanisms.

– Operations to support the updating of user data and recovery mechanisms.

3. User authentication procedures

4. IMS Restoration Procedures (see TS 23.380 [19]) to support S-CSCF service interruption

5.1.6 Functional Requirements of the Presentity Presence Proxy

The interaction between the Presentity Presence Proxy and the HSS, referred to as the Px interface, is handled using the mechanisms defined for the Cx interface.