OBJECT-ORIENTED COMMUNICATION STRUCTURES FOR MULTIMEDIA DATA TRANSPORT

With multimedia transport, user entities reside in subscriber terminal s and communicate with one another over a network by sending and recei ving multiple data streams as application level information (e.g., gra phics, audio, and text in a catalog browsing service). The evolving mu ltimedia applications generate requirements for complex transport capa bilities, i.e., functional features, in the end to-end communication s ystem such as handling of heterogeneity among communicating terminals, supporting finer levels of user-specifiable quality of data transport service, and synchronization of various data streams for delivery at users in real time, Accordingly, the communication system may be viewe d as extending the basic capabilities provided by the backbone network (e.g., bandwidth allocation) into a set of transport capabilities sui table for complex applications, This paper presents: 1) an object-orie nted view of user interface to the communication system with an elegan t separation of data transport functionalities, and 2) an approach to the design of underlying transport protocols. The object-orientation d ecomposes an application-level data transport into a set of network ch annel objects, with each channel object handling a separate data strea m, The object interactions are modeled using a ''dataflow programming' ' style, which allows a richer set of protocols to implement the commu nication system and offers flexibility to accommodate complex and hete rogeneous subscriber services/terminals. The ''data-flow programming'' method also allows a high degree of communication level parallelism a mong data transport through channels, The view of multimedia communica tion system as a ''parameterizable black-box,'' as underscored in the object-oriented structuring, allows easier interworking of the communi cation system with existing networks and easier integration of multime dia transport into programming environments.