Building the Internet's MBone: LBL's Van Jacobson a Principal Architect

December 9, 1994

By Jeffery Kahn,

In March 1992, an important new venue opened on the Internet--one in which users worldwide could meet in a common electronic window and not only see and talk to one another, but work on a shared "whiteboard." But despite its popularity within the select group that used the new technology--called the Multicast Backbone, or M-Bone--few others knew of its existence.

That began to change two weeks ago. Mick Jagger and the Rolling Stones brought their "Voodoo Lounge" concert to M-Bone, performing for 50,000 people in Dallas' Cotton Bowl as well as a small audience at workstations around the world. The event made international news, and brought M-Bone into prominence.

Van Jacobson of LBL's Information and Computing Science Division is one of the three principal creators of M-Bone. The others are Steve Deering, of Xerox Corp.'s Palo Alto Research Center, and Steve Casner of the University of Southern California. Deering and Casner developed the protocols that make the virtual network possible, and Jacobson created many of the tools that make it valuable.

As Jacobson told Newsweek magazine in a December 5 article, the Stones' concert should inspire new ways to use the medium. But well before Jagger strutted online, more than 10,000 people in 30 countries routinely used the M-Bone for collaborative work.

In multicasting, rather than send information to a single location, the network distributes it from senders to every receiver who has signed up for the session. While simple in concept, the magic underlying M-Bone is its ability to dynamically construct distribution trees using the shortest, most efficient paths. Because M-Bone usually includes live video, which means huge volumes of traffic, efficiency was a prerequisite to prevent congestion and collapse of the Internet.

M-Bone was first used to simulcast the March 1992 Internet Engineering Task Force conference. Since then, it has provided around-the-clock coverage of space shuttle flights, an opportunity for surgeons to observe and question a San Francisco surgeon performing a complex liver operation, and a place for Ph.D. candidates to defend their dissertations to committee members.

"The tools are so easy to use that anybody can announce a session and be their own producer," Jacobson says. "Somebody actually sent out to the universe live pictures of their pet iguana climbing a tree."

The heaviest use of M-Bone has been by network researchers to conference and collaborate with each other. It offers a number of advantages over teleconferencing, which joins a few sites with expensive dedicated transmission lines. M-Bone links anyone to the Internet who has a workstation with audio/video capabilities and a high-speed connection. Jacobson says this flexibility has resulted in moves by both NASA and DOE to replace teleconferencing with M-Bone meetings.

Jacobson's research group at LBL includes Steve McCanne and Sally Floyd. Jacobson and McCanne designed the whiteboard, which Jacobson calls an "infinite piece of paper." It allows participants in an M-Bone session to write, type, and draw on a shared drawing window. It even has a memory, so that those using it can flip pages, scrolling back to earlier versions of the contents, or import other drawings and text.

Jacobson also developed the session directory, a conference coordination tool that provides a menu of what is currently available or upcoming on M-Bone. The Session Directory allows the user to join a session, or to announce and advertise an upcoming session.

The tool pack developed by Jacobson's group also includes VIC (Video Conferencing) and VAT (Visual Audio Tool). These make it possible for all parties to both talk and listen. It also makes possible the transmission of a video stream to an unlimited number of participants.

Currently, Jacobson says, M-Bone is handicapped in that most of the routers that forward packets around the Internet do not support the Internet Protocol multicast addressing system developed by Deering. In the next year, new commercial routers are scheduled to be introduced that support multicasting. As this happens and as efficiency improves, Jacobson predicts that multicasting will become so ubiquitous that M-Bone will essentially disappear as a distinct entity on the Internet.

For those who want to know more about M-Bone, information is available on LBL's World Wide Web from Introduction to Videoconferencing and the MBONE Additional information can be obtained on the Web from the MBone Home Page