(Global MSF In- teroperability) to conduct comprehensive tests of IMS which involved over 225 network components from 22 participating vendors in its five labs that are spread across the world. The results showed that the overall architecture is complex; interoperability is impacted by the choice of implementation model while the IMS protocols are largely stable. The issues that were encountered were related to routing and configuration rather than protocols [12]. 9.10.4 Deployment The deployment of IMS is totally another story - within IMS architecture each function is logically considered as an individual component and can be deployed as a separate product. This deployment approach is highly unlikely and will be costly. Another likely and cost effective approach is to house several functional components together. In this approach the challenge is - which boxes to mix and match in order to offer a suitable solution. 9.10.5 Services Enhancement IMS must support legacy services with at least the similar parity if not better. The PSTN and cellular quality circuit switched voice, cellular data and short messages services, emergency services, and SO on, all need to be supported by IMS. Additionally, IMS must support additional multimedia services that are not currently offered. The challenge is twofold - first to come up with a superset of services and then to make sure that these services are offered reliably and with appropriate QoS across different networks. 9.10.6 Service Delivery Platform IMS outlines a service delivery platform (SDP) to accommodate multimedia services that are in high demand. However, there are a number of SDPs which already exist that focus on IT (Information Tech- nology) systems. The challenge is how to integrate the IMS elements with enterprise IT infrastructures. The need is to refine the IMS based SDP by accommodating some of the functional characteristics supported in today's IT based SDP systems. 9.10.7 IMS Capable Devices Though much attention has been paid to the IMS infrastructure, t