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Guest Editor's Introduction: Support for Glogal Teams

Injong , North Carolina State University

Pages: pp. 30-32

Effective teamwork is the key to the success for most organizations. One barrier to teamwork in a global economy is the geographical separation among team members, and hence the need to travel long distances. Fortunately, the unprecedented growth of the Internet is quickly reducing this barrier. Using novel Internet collaboration tools, a group of geographically dispersed co-workers can be "telepresent" in the same virtual information space without ever leaving their own offices. Grabbing the same files that co-workers a thousand miles away are working on, engaging in face-to-face conversations with them, visualizing and manipulating the same data objects at the same time, and controlling remote laboratory instruments are now just a few mouse clicks away. There seems little doubt that Internet-based collaboration technologies will revolutionize our daily activities, not just in our workplaces, but also in our homes, schools, and other social arenas.

Many recent advances in Internet technologies add diversity and new dimensions to computer-supported collaboration:

  • the development of a multicast communication infrastructure, such as the Mbone, and of platform-independent languages, such as Java, encourages a paradigm shift from small-scale intranet collaboration to large-scale, synchronous group work involving potentially thousands of participants from all over the world;
  • advances in multimedia streaming and computer graphics enhance our ability to create the illusion of telepresence;
  • rapid growth of the Web and advances in multiagent systems have coupled with asynchronous collaboration technologies in workflow applications that support around-the-clock teamwork.

This issue of IEEE Internet Computing presents a snapshot of this dynamic area of development in five articles. The articles describe the status of collaboration-enabling technologies and tools. They include case studies and experience in the implementation and use of multimedia collaborative environments over the Internet.

Large-scale collaborative sessions always face the issues of scalability in data delivery and heterogeneity in the systems that receive it. Thus, we begin with Steven McCanne's authoritative survey of multicast technologies and their associated protocols for addressing these issues, such as IP Multicast and lightweight session control. The protocols have been implemented in Mbone conferencing tools that are now in daily use by the large and growing Mbone user and research communities.

Of the four remaining theme articles, three describe case studies and implementation experience and the fourth introduces a protocol for sharing resources in large multicast environments. We hope you enjoy this snapshot of multimedia collaboration—Internet-style.

The Articles


Steven McCanne

A member of Lawrence Berkeley National Laboratory's team that developed the network and application software tools underlying the Internet Multicast Backbone, or Mbone, surveys the technologies that developed around the Mbone to support large-scale Internet-based multimedia conferencing.


Sushila Subramanian, G. Robert Malan, Hyong Sop Shim, Jang Ho Lee, Peter Knoop, Terry E. Weymouth, Farnam Jahanian, and Atul Prakash

The Upper Atmospheric Research Collaboratory integrated worldwide observational systems for collecting space physics data together with supercomputer-class theoretical models. The Web-based system provided services to support real-time global views of, for example, a magnetic storm. It also allowed scientists to make simultaneous comparisons of experimental data with theoretic output.


Lidia Fuentes and José M. Troya

Component platforms like DCOM and JavaBeans allow the construction of independent software components, which can be further assembled via application-level frameworks. MultiTel is a component platform and also an application framework for the composition of Java components. It manages the multimedia and networking resources used in the design of collaborative services.


Jitendra Padhye and Jim Kurose

Understanding how users interact with multimedia systems can help to optimize resource allocation and access mechanisms. Results from this study of user interactions with CM courseware at the University of Massachusetts call into question some current modeling assumptions and provide specific real-world data points for future studies.


Hans-Peter Dommel

As Internet-based collaborative applications grow larger and more diverse, collaborative sessions may require more formal mechanisms to coordinate the use of shared resources. The authors survey the problems and existing solutions, and then propose a new approach that integrates group coordination with extended multicast services.

Standards Activity for Interactive Multimedia Communications


The Audio/Video Transport Working Group was chartered "to specify a protocol for real-time transmission of audio and video over UDP and IP multicast. This is the Real-time Transport Protocol (RTP), together with its associated profile for audio/video conferences and payload format documents."

The current WG goals include revising the main RTP specification and the RTP profile to draft standard status, completing the RTP management information base (MIB), producing a guidelines document for future developers of payload formats, and continuing development of new payload formats.

The payload formats currently under discussion include media-specific formats, such as MPEG-4 and PureVoice, and forward-error-correction (FEC) techniques that apply to multiple formats.


The Multiparty Multimedia Session Control (MMUSIC) Working Group was chartered "to develop Internet standards-track protocols to support Internet teleconferencing sessions. MMUSIC's focus is on supporting the loosely controlled conferences that are pervasive on the Mbone today. However, the WG will also ensure that its protocols are general enough to be used in managing tightly controlled sessions."

Current MMUSIC activities include the standardization of

  • session initiation protocols (initiating a session and inviting participants),
  • session description protocols (protocols for distributing session descriptions),
  • real-time stream protocols (the protocols for controlling on-demand continuous media delivery)


The T.120 series of ITU-T Recommendations defines communication and application protocols that support a multipoint data communication service for multimedia conferencing environments. The Recommendations can be purchased from the ITU. The T.120 document presents the architectural model, which shows the interrelationships among the constituent Recommendations. A primer and summary of the protocol is available on the Website of DataBeam Corporation.

The lower layers of the T.120 architecture specify an open-standard mechanism for providing multipoint data communication services to any application that can use them. The upper level layers define protocols for specific conferencing applications (currently T.126 for still image exchange and T.127 for multipoint file transfer).


DAVIC is an industry consortium established in 1994 to create open interface and protocol specifications that support end-to-end interoperability of digital audio-visual applications and services. DAVIC includes more than 150 member companies from more than 25 countries.

Each version of the DAVIC 1.0 specifications builds on the previous version. The current specifications allow the deployment of applications such as video on demand and some basic forms of teleshopping. DAVIC 1.5 version is expected to address digital audio-visual broadcast over IP-based networks, delivery of interactive multimedia over IP, integration of DAVIC and Internet content, and content metadata for end-to-end systems.

About the Authors

Injong Rhee is assistant professor of computer science at North Carolina State University. He received a BE degree in electrical engineering from Kyung Pook N. University, Korea in 1989, and his PhD in computer science from the University of North Carolina at Chapel Hill in 1994. His research interests include synchronization, group communication middleware, congestion control, robust video transmission, and video compression. He received the National Science Foundation Faculty CAREER Award in 1999. Rhee has published numerous articles on multimedia systems and networking, reliable multicast, distributed systems support for Internet-based collaborative computing, synchronization, and real-time systems. He was a member of the program committee for the International Conference on Distributed Computing Systems (ICDCS 97), and he is a member of the IEEE and the ACM.
Readers may contact him via email at rhee@csc.
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