A hierarchical directory based X.400 server

The need to use the X.500 directory to resolve X.400 naming and routing problems led the OSI Community to elaborate some schemes defining the organization and the exchange of data for this purpose (Jordan, 1991; Kille, 1988, 1992; Mastrolonardo et al., 1991). We present in this article, the implementation of an X.400 MHS pilot that relies completely on the use of the X.500 directory service. We show the three different situations where it is accessed. The first situation is related to name resolution. The second is based on dynamic attributes and aims to interface between the directory and other non-OSI applications essentially for X.500-DNS gatewaying. Finally the third situation is for routing. We show how routing tables are integrated in the directory and explain the added value to such a service. Facing heavy traffic due to massive name queries, we then present a hierarchical routing mechanism to improve resolution efficiency. We describe it and show some positive results obtained through X.400 traces.