This paper reports on the specification and development of an advanced, feature rich call handling mechanism. The conferencing call model, referred to as the service session graph, is heavily influenced by, and has significantly contributed to, the TINA service architecture informational viewpoint. It is shown that two new features of the model, implicit stream binding and control mechanisms, allow telecom services to incorporate advanced conferencing features in a very efficient way. A number of implementations are described, where the call model is extended with a series of end-user services and runs on top of ATM networks.

Self-healing is the ability of a network to reconfigure itself around failures such that calls in progress are not dropped and suffer of no or almost no degradation in quality of service. Providing self-healing capabilities in all parts of the future ATM network in a cost effective way is therefore a key challenge. A new self-healing method based on the multilink concept is presented for dedicated parts of the ATM network, such as, for instance, feeder networks. In the multilink concept that is proposed, the cells of an ATM connection carried by a multilink are distributed over several physical links. If a physical link supporting the multilink fails, the cells will be distributed among the remaining physical links thus providing a self-healing capacity. In this way the quality of service can be maintained at the expense of a higher load on the remaining physical links. The speed of restoration only relies on the detection and signaling of the failure since spare capacity is available on the very multilink. The sharing of spare capacity in addition to the statistical multiplexing gain provides a cost effective self-healing method and leads to a simplified network resource management. The proposed multilink concept is based on an extension of the multipath self-routing concept, which is currently applied by Alcatel in its ATM switching fabric.>