The Internet Multicast Backbone (MBone) is a virtual subnetwork deployed over the Internet that supports IP Multicast. IP Multicast is an N-way, unreliable protocol that has been used to deliver streaming media including audio, video, and data. The advantage of multicast over traditional unicast protocols (e.g., TCP and UDP) is that data transmission capacity is used efficiently. For example, packets are only delivered to hosts and users who have joined a particular multicast conference. In addition, only one copy of a packet is sent to participants in a subnetwork which means that if 20 people on the east coast and 50 people in the San Francisco area are participating in a conference, only one copy of transmissions from a participant needs to be sent across the United States.

A higher level protocol to transport real-time media streams (RTP) and a collection of tools to capture, send, receive, and display media streams (e.g., vat, vic, sd, etc.) were developed in the early 1990's to support experiments in media streaming and conferencing. These tools are called the Internet MBone Tools. Many of these tools and protocols were developed by researchers at Lawrence Berkeley Laboratories and the University of California at Berkeley.

In the Spring Semester 1995, Professors Lawrence A. Rowe and Martin Vetterli along with the assistance of Professor Steven McCanne who was then a graduate student at Berkeley, begin broadcasting the regularly scheduled Berkeley Multimedia, Interfaces, and Graphics Seminar world-wide on the Internet MBone. The seminar series was very successful. Remote attendance ranges between zero and two hundred people depending on the state of the Internet MBone, the technology required to produce the broadcast, and viewer interest in the speaker and topic. Many changes have been made to improve the quality and reliability of the broadcasts. BIBS is the next step in the development of remote conferencing and distance learning technology using the Internet MBone technology.

The following links provide more information on the technology, protocols, and history of the MBone.

• Multicast Technology and Applications
• Internet MBone Resources
• U of Michigan Merit MBone Software Archives
• UC Berkeley Mash Project
• ICAST MBone Information Web

Larry Rowe
Copyright © 1998 by the Regents of the University of California
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