IP Multimedia (IM) Core Network (CN) subsystem Centralized Services (ICS); Stage 3
IP Multimedia (IM) Core Network (CN) subsystem centralized services (ICS) allow for the delivery of consistent IMS services to the user regardless of the attached access type (e.g. CS domain access or IP-CAN).
The present document provides the protocol details for the realization of ICS based on the Session Initiation protocol (SIP), the Session Description Protocol (SDP), the I1 protocol, and the protocols of the 3GPP Circuit-Switched (CS) domain (e.g. CAP, MAP, ISUP, BICC and the NAS call control protocol for the CS access).
This document makes no ICS specific enhancements to SIP or SDP beyond those specified in 3GPP TS 24.229 [11].
The present document is applicable to User Equipment (UEs), MSC Servers and Application Servers (AS) providing ICS capabilities.