A computer-based message system (CBMS) consists of computer facilities that expedite the creation, management, and nonreal time distribution of messages. These systems are increasingly being used for formal and informal communication, supporting the distribution of textual messages. However, nontext media such as voice and graphics are very important for human interaction, and are becoming more and more important in computer system applications. As a result, there is a growing need for the support of media other than text in CBMS.Before standards for multimedia CBMS can be implemented, there are many technical issues that must be addressed. These range from the design of new mechanisms for the distribution of multimedia mail, to the design of tools needed for editing nontext media. This panel will be discussing issues encountered in the development of multimedia CBMS and an outlook for standards for multimedia computer mail.

In this paper we present an overview of an architectural model for large, distributed computer-based message systems. This model specifies 1) the organization of message systems in terms of functional entities; 2) the operation of the system; 3) the protocols and interfaces needed for interprocess communication; 4) the organization of the directory system used to support identification services. General architectural considerations related to the communications protocols for computer-based message systems are presented; these follow the general framework of the ISO model for open system interconnection. The organization and operation of the directory system are discussed in detail. Special emphasis is given to the importance of identification services in international and interconnected message systems.

In this paper we present major design considerations for the development of international computer mail protocols. A simplified functional model for computer mail systems is introduced to serve as the basis of the discussion of the protocols. The general framework of the Reference Model for Open System Architecture proposed by the ISO is followed in the description of the computer mail protocol and design issues involved at each layer of the computer mail protocol are examined. The computer mail protocol is aimed at non-interactive communication between message system users.

In the first talk, Dr. Lebow will discuss DoD plans for providing secure voice for three disparate communities within DoD: 1. Narrowband Tactical (datarate: up to 2.4 KB), 2. Wideband Tactical (16 and 32 KB) and 3. Long-haul Strategic (DCS-based, up to 9.6 KB). Dr. Lebow will compare advantages and deficiencies of the three systems and will discuss the evolution of these systems into a two-rate architecture in the 1990's.,

This paper describes briefly three new Defense data networks, AUTODIN II, SATIN IV and PWIN which employ packet switching technology. It then discusses Defense policy concerning common-user networks and in what circumstances special purpose networks are permitted. Finally it addresses the issue of whether the three new data networks under discussion are common-user or dedicated networks.

This paper considers a mixed-media packet-switched computer communication network which consists of a low-delay terrestrial store-and-forward subnet combined with a low-cost high-bandwidth satellite subnet. We show how to route traffic via ground and/or satellite links by means of static, deterministic procedures and assign capacities to channels subject to a given linear cost such that the network average delay is minimized. Two operational schemes for this network model are investigated: one is a scheme in which the satellite channel is used as a slotted ALOHA channel; the other is a new multiaccess scheme we propose in which whenever a channel collision occurs, retransmission of the involved packets will route through ground links to their destinations. The performance of both schemes is evaluated and compared in terms of cost and average packet delay tradeoffs for some examples. The results offer guidelines for the design and optimal utilization of mixed-media networks.