Along with the improvement of micro processors and local area networks, a distributed system becomes useful to realize a telecommunication system. It has potential advantage to achieve both high performance and high reliability. However, the design of a distributed system tends to be more complicated compared to a conventional centralized system. For the purpose of the standardization of distributed processing, ISO and ITU-T study the Open Distributed Processing (ODP) and are currently standardizing the Basic Reference Model of ODP (RM-ODP). To avoid dealing with the complexity of distributed systems, RM-ODP defines five viewpoints. The viewpoint approach of RM-ODP is proposed as a framework for the design of a distributed system. Although some previous works give the design methods of distributed systems based on the ODP viewpoint approach, the detailed design method has not been fully specified or all of the five viewpoints are not taken into account. In this paper, we describe a detailed design method for a distributed telecommunication system based on the ODP viewpoint approach. The method applies the five viewpoints to the three phases of design of a distributed system, that is, requirement analysis, functional design and detailed design phase. It clarifies what specifications for the target system should be made from the individual viewpoints and how the specifications are related each other. It also takes account of the platform which provides the distribution support, and gives the design method for both the platform and the application specific functions on the platform. The design method is examined by applying it to the design of a distributed MHS system supporting X.400 series protocols. In this example, the remote procedure call based on the client-server model is selected as the base of the platform. The result shows that our method is useful to simplify the complexity of the design for a distributed telecommunication system.

In order to make the implementation of network components flexible and cost effective, it is required to use widely available technologies as the implementation platform. The distributed operating systems can be adopted as such a platform, because they allow to implement a network component using multiple computers connected through a local area network. In this paper, we focus on the Intelligent Network (IN) whose network components are modelled as Functional Entities (FEs), and describe an implementation method of FEs using distributed operating systems. Our method is summarized as follows: The remote procedure call (RPC) is used for the access transparent inter-process communication. The lightweight process mechanism is used for handling concurrent requests. CCF/SSF (Call Control Function/Service Control Function) and SDF (Service Data Function) are implemented as an SSF server and an SDF server, respectively. SCF (Service Control Function) is composed of a Service Dispatcher and a set of Service Executors. The Service Dispatcher accepts all the requests for IN call processing and dispatches them to appropriate Service Executors. Service Executors are created for the individual IN services and execute the service logics. SDF server and Service Executor may be replicated for load partitioning.This paper has also described the implementation of experimental system supporting "Freephone" service based on our method, and showed the performance evaluation of the experimental system in terms of the real-time and concurrent call processing of IN services. We used Mach and SUN OS as a platform for implementing the servers for FEs. The experimental system using four workstations shows that it can handle up to 170IN calls in one second with the additional response time of less than 200msec, which is small enough compared with the response time for the basic connection control. Those results prove that our method is feasible for implementing practical FEs.

The Intelligent Network (IN) provides advanced telecommunication services by use of network components distributed over the telecommunication networks. Therefore, the distributed processing technologies are the key to IN and the distribution transparencies which are the purpose of the distributed processing technologies are useful to reduce the difficulties of the IN development. This paper proposes two approaches to apply distributed processing technologies to IN considering on which plane to use the distribution transparencies in the IN conceptual model. The first approach applies distributed processing technologies to the implementation of the functional entities defined in the IN distributed functional plane. The second approach uses distributed processing technologies as the service independent building blocks defined in the IN global functional plane: This paper also presents the results of some typical case studies of the proposed two approaches, the implementation of the functional entities using the remote procedure call and the use of the global naming service as the number translation service independent building block, which show that the distributed processing technologies are highly applicable to IN.