CS406: Information Security

Figure 1: architecture of IMS

IP Multimedia Subsystem or IMS is a standardized Next Generation Networking (NGN) architecture for telecom operators that want to provide mobile and fixed multimedia services. It uses a Voice-over-IP (VoIP) implementation based on a 3GPP standardized implementation of Session Initiation Protocol (SIP), and runs over the standard Internet Protocol (IP). Existing phone systems (both packet-switched and circuit-switched) are supported.

The IMS is the technology that will merge the Internet with the Cellular world. It is network enables and drives efficient converged service offerings. It is the key to delivering multimedia services with telecom-grade quality of service across fixed and mobile accesses. It creates new opportunities for operators who want to deliver attractive, easy-to-use, reliable and profitable multimedia services – including voice, pictures, text and video, or any combination of these – with existing services such as web, email, instant messaging, and videoconferencing available nearly everywhere. The IMS is based on a horizontally layered architecture, consisting of three layers, namely, Service Layer, Control Layer, and transport Layer.

(i) Service Layer comprises application and content servers to execute value-added services for the user.

(ii)Control layer comprises network control servers for managing call or session set-up, modification and release. The most important of these is the Call Session Control Function (CSCF).

(iii)Connectivity Layer comprises of routers and switches, for both the backbone and the access network Device layer consists of user terminal devices like UE (user equipment), PDA, Desktop, and Laptop which can connect to the IMS network.

Figure 2: Reference point in IMS