This article discusses technical issues related
to delivery of multimedia services, such as video-on-demand, over heterogeneous
networking environments. In particular, it describes the design and
implementation of an experimental system for multimedia service interworking
between a DAVIC (Digital Audio Visual Council) domain and an Internet domain.
The system, called MIDDLEMEN (middlemen for multimedia environment), consists
of the broker and the interworking unit, which work together to provide
multimedia services across different types of networks in a seamless manner.
The broker acts as a guide to multimedia services, and complements servers or
clients that are not equipped with full functionality. The broker also controls
the resources in MIDDLEMEN. The interworking unit performs various translation
functions under the control of the broker, including stream transport protocol
conversion, traffic monitoring and bit-rate control, service gateway
conversion, and stream control conversion. Current implementation supports the
delivery of a DAVIC-compliant VOD service from an ATM network to an IP network