This paper proposes a special resource based architecture to support multimedia, multiparty communications in ATM networks, and details it for the implementation of point-to-multipoint and multipoint-to-point ATM connections. The special resources are implemented by servers: these have a modular design and each of them provides the facilities specific to one special resource. Enhanced connection types are supported by a two level architecture: homogeneous servers are arranged into logical subnetworks that are accessed by the users by means of point-to-point switched connections. New algorithms are designed to route point-to-multipoint and multipoint-to-point ATM virtual connections inside the logical subnetworks. To this purpose, two classes of heuristics are considered: those that take into account only the link's spare capacity to identify a suitable and low cost routing; and those that attempt to minimize the number of resources assigned to a connection. The performance evaluation shows that the former have good connection blocking performance, are simpler and impose a lower load on the servers than the others.