MODELING END-TO-END PROTOCOLS OVER INTERCONNECTED HETEROGENEOUS NETWORKS

The performance aspects of end-to-end communication in interconnected heterogeneous networks are investigated. The individual networks to be connected (e.g. LANs, highspeed LANs, X.25 networks, WANs including satellite links, ISDN, B-ISDN) differ significantly in their quality of service. On the other hand, requirements imposed by applications also differ significantly. Thus there is no single protocol stack which is optimum for all cases, and decisions have to be made on a special case-by-case basis. Motivated by the planned European space mission, for which a proper protocol stack assuring reliable end-to-end communication between application processes residing in space labs and ground-based application processes has to be chosen, a novel, top down modelling approach is developed. Rather than combining models of individual subnetworks, we represent any type of subnetwork by a specific set of network quality of service characteristics, and model the transport protocol so as to express the obtainable transport quality of service. Using such an approach it is possible to decide what kind of technological constraints have to be imposed on the parameters of a subnetwork A, which is to be connected to the given subnetworks B and C so as to assure the desired end-to-end quality of service.