Motivation for and Design of a SIP2IMS Gateway

This paper looks at the development of the IP Multimedia Subsystem (IMS) from the Session Initiation Protocol (SIP) and how it has introduced added security and extensions to the basic SIP standard to enable voice, data and media services. The paper identifies the difficulties encountered in enabling interworking with non-IMS clients and then investigates the solutions proposed by the 3GPP including "early IMS". The proposals by ETSI TISPAN on interworking are examined and compared with those by the 3GPP as well as their different security architectures. The paper then looks at the issue of connecting users with legacy devices in the home network and proposes the SIP2IMS Gateway as a solution for a number of scenarios. The design and implementation and validation of these solutions on the IMS test bed at Fraunhofer FOKUS, Berlin and the University of Limerick are presented and a short comparison with similar work is made. Finally, plans for future work are described.