IMS Interworking

Abstract: The goal of this project was to analyze the IP Multimedia Subsystem (IMS) with respect to the interworking functionality between two or more IMS domains belonging to different operators. The thesis presents an overview of IMS, its purpose, the circumstances and the environment in which it has evolved, and a look into some of the challenges that lie ahead. Through careful examination of the history of the mobile communications and of IMS itself, the thesis attempts to give the reader a full and comprehendible understanding of what IMS is, what its purpose is, and why it came into existence. The thesis considers the different models of IMS interworking, as they are currently envisioned by the standardisation bodies and the telecom industry. This analysis aims to identify some of the problematic aspects of the IMS Interworking and to suggest concrete areas for further investigation, which will contribute to the future successful IMS development and deployment. The report looks into such aspects of IMS interworking as the DNS, different models for ENUM DNS resolution; security issues and technical challenges of security with respect to the network as a whole and some of the IMS network elements in particular, such as the DNS. This thesis also presents the findings of the authors, regarding the challenges of interworking between networks built to support different versions of the IP protocol. The thesis focuses on the areas of interest, mentioned above, as these have been identified as being of particular significance in connection with the further development of the IMS architecture.