Atika Cohen

AMS: an integrated simulator for open systems

The main objective of the OSISIM project (Open System Integrated Simulator) is to set up an atelier for the modeling of communication networks and the analysis of their performances. The atelier gives the end-user powerful tools to edit a communication system in a graphical environment. The representation of a system to be simulated is based on models of several standard networks available in the library which is the kernel of the atelier. Each model implements uniform and well-defined sets of functions, while having clearly specified interfaces. This article describes the architecture of the atelier, and focuses on the internal structure of basic models.<<ETX>>

Generic simulation models of communication systems

One of the most significant criticisms on traditional simulation modeling has been the lack of reusability. However, the cost of using simulation technology can be reduced through the extensive application of model reusability. We address the question of reusability by showing how to create, in a generic way, models of complex communication network components from a library of basic models. These reusable units model network elements, such as buses, protocols, bridges, satellite repeaters, etc. We focus on how to enhance this library by deriving benefit from the reusability aspects of basic models. The Generic Models (GeMs) represent an adequate solution to notably enrich the library. They will be constructed by the modelers who have to respect certain constraints depicted in this paper. These constraints are related to the modeled domain which is the communication system.

Function-based methodology to model communication protocols for performance evaluation

The paper describes a methodology based on the function concept, as defined in the OSI Reference Model, to model protocol entities in order to assess their performance while being used in a communication network. This concept provides a high degree of flexibility to model protocol entities, because it allows the modeler to combine some functions needed to build a given protocol which will provide a particular level of performance. The functions of a protocol entity are structured inside a library of functions, and are mainly related by means of the precedence relation.<<ETX>>

High speed data communication by satellite in Europe-the HELIOS architecture

A description is given of the HELIOS architecture, which is based on access points running on OSI data link protocol and acting as gateways between the satellite circuit and a local area network. The access points consist of Bull SPS/7 minicomputers; test of a preliminary version of the software have allowed the successful transmission of files at 128 kb/s between Paris and Brussels. Being totally OSI-compatible, the HELIOS architecture is independent of manufacturers, applications, or other local considerations, and will therefore also be compatible with the future, ground-based, high-speed circuits. The aims and scope of HELIOS as well as its main characteristics and basic architecture are examined. The present status of work on the HELIOS project is discussed.<<ETX>>