Computer communications through telecommunication satellite systems — The NADIR project

New telecommunication satellite systems, such as SBS in the U.S. or TELECOM1 in France, can be used by computers for data communication. Compared to existing terrestrial networks, satellite networks have different characteristics s specific error distribution, natural geographic coverage, long propagation delay (about 300 ms), high transmission rates (several megabits /second) and broadcasting facilities. These characteristics are illustrated in this paper by a short description of the TELECOM 1 satellite system. New distributed computer applications will develop by taking advantage of high transmission rates and broadcasting facilities which are offered by satellite systems. Some examples of these possible applications in the field of remote processing, distributed data bases, computer teleconferencing and electronic mail systems are given in this paper. All these systems will need basic tools to make efficient use of satellite data channels. The paper then discusses the main problems related to the design of these tools, e. g. protocols for point to point or multipoint high speed data transfer, gateways for local network interconnection through satellite channels.