Sudhir R. Ahuja

The rapport multimedia conferencing system

This paper describes the design and initial implementation of the Rapport multimedia conferencing system, which supports interactive, real-time, distributed conferences among two or more users. Using computers connected by data and voice networks, this system creates an environment in which many sorts of meetings can take place, including telephone conversations, discussions among colleagues, and lectures. Rapport provides new opportunities for meetings, allowing a user to interact with distant colleagues and to participate in several conferences concurrently at his or her workstation. The system allows many existing computer programs to be used, unmodified, within its conferencing environment. Thus computer-generated data and displays are available to the conferees for manipulation and editing, enhancing the exchange of information during meetings. Although Rapport does not encourage a particular methodology of meeting conduct, such specialized support can be built using Rapport. The paper outlines Rapports conference abstraction and the model on which it is based — the “virtual meeting room.” It then presents an overview of Rapports architecture, discusses the systems environmental requirements, and concludes by mentioning some of our plans for future work with Rapport.

A comparison of application sharing mechanisms in real-time desktop conferencing systems

Desktop conferencing is a term used to describe real-time, computer-based conferences in which users may share data through their personal computers. In these conferences, the participants may access user-level programs, called application programs, which produce common displays (screens or windows) on their computers. Because each participant may give input to the application program and sees its resulting output as though the program were executing on his or her local computer, these applications retain their own look and feel as they form a shared environment for the conference. We compare some methods of sharing application programs during real-time, computer-based conferencing. In particular, we have explored different methods in three versions of Rapport, a multimedia conferencing system. We examine the qualitative and quantitative differences of these implementations using some typical shared applications and find that one method possesses good semantic characteristics as well as good performance in several network environments.

The Rapport multimedia conferencing system-a software overview

The Rapport multimedia conferencing system supports interactive, real-time, distributed conferences among two or more people. Executing on personal workstations interconnected by data and voice networks, Rapport provides basic mechanisms to create, manage, and terminate conferences. The authors focus on the Rapport software, which is a three-level hierarchy comprised of the user interface, conference server, and system levels. The user interface level provides humans and other programs with access to the Rapport system. Maintaining consistent views of the conference for all the participants, the conference server level coordinates the activities of the conferees and provides basic protocols for exchanging information and control during a conference. The system level includes window management service and drivers for the hardware required to transmit data in the various media.<<ETX>>

Matching language and hardware for parallel computation in the Linda Machine

The Linda Machine is a parallel computer that has been designed to support the Linda parallel programming environment in hardware. Programs in Linda communicate through a logically shared associative memory called tuple space. The goal of the Linda Machine project is to implement Lindas high-level shared-memory abstraction efficiently on a nonshared-memory architecture. The authors describe the machines special-purpose communication network and its associated protocols, the design of the Linda coprocessor, and the way its interaction with the network supports global access to tuple space. The Linda Machine is in the process of fabrication. The authors discuss the machines projected performance and compare this to software versions of Linda. >

Networking requirements of the Rapport multimedia conferencing system

The Rapport multimedia conferencing system supports interactive real-time distributed conferences among two or more people. Rapport executes on personal workstations interconnected by data and voice networks. It is designed to help people emulate face-to-face conferences as closely as possible with their workstations. These conferences can be of different type, including phone conversations, group meetings, or lectures. The authors describe the Rapport system and elaborate on its networking requirements. Based on experience with their initial prototype system, the authors highlight some of the current networking limitations and examine future directions, such as broadband communication, for alleviating these problems.<<ETX>>

Control issues in multimedia conferencing

A discussion is presented of the control and coordination functions that must be associated with communication networks supporting multimedia conferencing systems. The authors have determined that the systems need underlying networks with large numbers of connections available to each user, direct support for message multicasting, and synchronization of transmissions over associated links. Furthermore, each of these capabilities needs associated, user-accessible control functions.<<ETX>>

An associative/parallel processor for partial match retrieval using superimposed codes

This paper presents the design and implementation of special hardware for effective use of the method of superimposed codes. It is shown that the method of superimposed codes is particularly well suited to easy design and implementation of fast and modular hardware. The implementation has shown that a performance gain of two orders of magnitude over conventional software implementations is obtained by using the special hardware. This makes the method of superimposed codes extremely attractive for data base system requiring partial match retrieval. We also demonstrate that the associative memory design is easily adaptable to large scale integration which would make such an approach very cost effective and lead to even further gains in performance.

The architecture of a Linda coprocessor

We describe the architecture of a coprocessor that supports the communication primitives of the Linda parallel programming environment in hardware. The coprocessor is a critical element in the architecture of the Linda Machine, an MIMD parallel processing system that is designed top down from the specifications of Linda. Communication in Linda programs takes place through a logically shared associative memory mechanism called tuple space. The Linda Machine, however, has no physically shared memory. The microprogrammable coprocessor implements distributed protocols for executing tuple space operations over the Linda Machine communication network. The coprocessor has been designed and is in the process of fabrication. We discuss the projected performance of the coprocessor and compare it with software Linda implementations. This work is supported in part by National Science Foundation grants CCR-8657615 and ONR N00014-86-K-0310.

The Rapport multimedia communication system (demonstration)

The Rapport multimedia communication system [Ah 88] allows people to hold long-distance discussions, sharing voice, video, and program displays in real-time. Rapport manages these meetings by coordinating the muitiple communication streams among the participants. People can take part in a Rapport meeting using a range of devices, from simple telephones to workstations equipped with specialized peripherals. Conventional teiephone calis are managed as voiceonly meetings. Meeting participants with appropriate monitors can see each other through video feeds and share displays of other video-based information. Rapport also allows meeting participants to see common program displays on their computer monitors.

A market based approach for efficient resource management in an intranet

In this paper a pricing technique for resource management in an intranet environment is given. The price of the services are dynamically determined by the servers of the network, taking into account the general policy of the manager of the network. Both decentralized and centralized control is used to increase the efficiency of the network. An architecture imposing small implementation cost is presented. Implementation issues are discussed and experimental results are given.