This TS specifies:
The interactions between the HSS (Home Subscriber Server) and the CSCF (Call Session Control Functions),
referred to as the Cx interface.
The interactions between the CSCF and the SLF (Server Locator Function), referred to as the Dx interface.
The IP Multimedia (IM) Subsystem stage 2 is specified in TS 23.228
and the signalling flows for the IP
multimedia call control based on SIP and SDP are specified in TS 24.228
This document addresses the signalling flows for Cx and Dx interfaces.
This document also addresses how the functionality of Px interface is accomplished.
The Presence Service Stage 2 description (architecture and functional solution) is specified in TS 23.141