ement the RST reference point by using the same protocols to interface with various service platforms. Open standard-based service platforms for the NGN service stratum are limited. Most service platform standards are now considered legacy. For example, the Intelligent Network (IN) [9] focuses on voice services operating over circuit-mode transports. The IN does not take advantage of the underlying converged network resources and capabilities, since it implements the RST reference point using its legacy INAP [10] protocol. In addition, legacy service platforms do not satisfy service stra- tum requirements, such as exposing service enablers to external entities. As a result, they do not implement the RCS and RSS reference points. Other service platforms use proprietary mechanisms and therefore hinder NGN standardization. Hence, a stan- dards-based service platform is required for the NGN service stratum. We motivate the use of the SDP for the NGN service platform. The SDP architecture will also provide the structure needed for the NGN service platform architecture. 2.3 Service Delivery Platform The SDP represents a concept with no agreed definition. However, a popular inter- pretation specifies the SDP as an IT-based platform used by telcos to provide Service Delivery Platforms services to a variety of customers. [2]. Both fixed and mobile telcos may use an SDP to provide services. These services include traditional telco services, such as tele- phony, and advanced data services, such as those provided by IT applications. Expanding this definition, [2] defines a minimal set of SDP requirements: Is service-oriented because it manages service creation, provisioning, execu- tion, and billing. 2. Supports the delivery of services in a network and device-independent man- ner, by abstracting the underlying network infrastructure. 3. Provides a single standardized point for developers to find and use diverse service enablers and content. 4. Provides external developers and IT using enterprises with open and secure access