An Evaluation of Architectures for IMS Based Video Conferencing

The IP Multimedia Subsystem is an architectural framework for delivering multimedia services over an Internet Protocol (IP) network. Originally, it was specified for wireless networks, but has since evolved to incorporate fixed line access as well. It forms part of a Next Generation Network (NGN) which is defined as a packet-based network where the service functionality is independent of the underlying transport technologies. This allows new converged services to be implemented on top of an existing packet switched network. The IMS is not intended to act as a standard for services, but rather to aid the creation of new multimedia applications. As such, it has a horizontal control layer which separates the access network from the service layer. Each new service developed does not need its own control functions but can rather reuse the common infrastructure provided by the IMS. Examples of these features are: Quality of Service (QoS), user authentication, charging and security. Thus the IMS provides a good platform to develop multimedia rich services. This paper evaluates two different architectures for providing a video conferencing service over the IMS. It discusses the different methods of handling the control signalling, as well as different ways of controlling the multimedia traffic. The first architecture analysed is modelled upon a standard server-client archetype. The second architecture discussed is based upon a distributed P2P model. It concludes that each architecture has its own set of advantages and disadvantages and both systems are viable for different environments.