ing services individually for each specific application, a service platform is needed that presents standard interfaces to allow applications to access and orchestrate these services. Such standard platforms have been developed over the past years, for example, Parlay for telecommunication networks [1], and IP Multimedia Subsystem (IMS) for IP-based fixed and mobile networks [2-4]. These platforms are composed of service functions and standard interfaces for applica- tions to discover, access, and orchestrate those service functions. The IMS is a specification of an environment where these types of services can be rapidly developed, deployed, and delivered with relative ease in a standardized fashion as compared to current vendor-based solutions. IMS is built for services and applications, providing operators the capability to manage rich multimedia services across both next-generation and traditional (with limited functionalities) networks. In addition to deriving added value from their own networks, operators can further benefit by opening up these networks to host third-parties' services and applica- tions. IMS is standard based and one of the key features is the use of open interfaces and functional components in both hardware and software systems to support real- time interactive services and applications. Design and Implementation of an IMS-Based Testbed IMS was introduced by the 3rd-Generation Partnership Project (3GPP) initiative to control and provide multimedia services over 3G mobile networks, but it is now adopted in the next-generation network (NGN) standardizations. The key technology behind IMS is Session Initiation Protocol (SIP) [5]. Many of the important interfaces between IMS components use SIP as the underlying signaling protocol. IMS specification began in 3GPP Release 5 as part of the core network evolution from circuit switching to packet switching and was refined by subsequent Releases 6 and 7 [6]. Till today, IMS standards are still evolving. Both the International Telecommunication Union