IP Multimedia Subsystem (IMS); Stage 2
This document defines the stage-2 service description for the IP Multimedia Core Network Subsystem (IMS), which includes the elements necessary to support IP Multimedia (IM) services. ITU‑T Recommendation I.130 [4] describes a three-stage method for characterisation of telecommunication services and ITU‑T Recommendation Q.65 [3] defines stage 2 of the method.
This document does not cover the Access Network functionality except as they relate to provision of IM services, these aspects are covered in the normative Annexes.
This document identifies the mechanisms to enable support for IP multimedia applications. In order to align IP multimedia applications wherever possible with non-3GPP IP applications, the general approach is to adopt non-3GPP specific IP based solutions.