The MBONE is a critical piece of the technology that's makes the sharing of any digital information, like data, voice, and video conferencing on the Internet, cheap and convenient.
It is possible that organizations will adopt MBONE as a low cost way to conduct meetings without all the expenses of telecom equipped conference rooms. Smaller, informal organizations could use MBONE as well as large companies, because MBONE would be controlled personally, not commercially.
With today's technology there is a growing need for multicasting in the network.
Unfortunately, the majority of the routers on the Internet today don't know how to handle multicasting. Most routers are set up to transport traditional Internet Protocol (IP) unicast packets information that has a single, specific destination. Although the number of routers that know how to deal with multicast are growing, those products are still in the minority.
Router manufacturers have been reluctant to create equipment that can do multicasting until there is a proven need for such equipment. But it's difficult for users to try out a technology until they have a way to use it. Without the right routers, there's no multicasting and without multicasting, there won't be the right routers.
In 1992, the Internet Engineering Task Force (IETF) decided that what no one would do in hardware, they could do in software. So they created a "virtual network", a network that runs on top of the Internet, and wrote software that allows multicast packets to traverse the Net. Armed with the custom software, these folks could send data to not just one Internet node, but to 2, 10, or 100 nodes. Thus, the MBONE was born.
The MBONE is called a virtual network because it shares the same physical media, wires, routers and other equipment, as the Internet. The MBONE allows multicast packets to travel through routers that are set up to handle only unicast traffic. Software that utilizes the MBONE hides the multicast packets in traditional unicast packets so that unicast routers can handle the information.
The scheme of moving multicast packets by putting them in regular unicast packets is called tunneling. In the future, most commercial routers will support multicasting, eliminating the headaches of tunneling information through unicast routers.
When the multicast packets that are hidden in unicast packets reach a router that understands multicast packets, or a workstation that's running the right software, the packets are recognized and processed as the multicast packets they really are. Machines (workstations or routers) that are equipped to support multicast IP are called m-routers (multicast routers). M-routers are either commercial routers that can handle multicasting or (more commonly) dedicated workstations running special software that works in conjunction with standard routers.
Multicasting is a network routing facility a method of sending packets to more than one site at a time. The MBONE is a loose confederation of sites that currently implement IP multicasting.
Today, multicasting is used for videoconferencing, audioconferencing, shared collaborative workspaces, and more. Conference multicasts generally involve three types of media: audio, video, and a whiteboard a virtual note board that participants can share.
Perhaps the most sought after function that the MBONE provides is videoconferencing. The MBONE originated from the Internet Engineering Task Force's attempts to multicast its meetings as Internet videoconferences. MBONE video is nowhere close to television quality, but at a few frames a second, video quality is good enough for many purposes.
The MBONE's capability to carry remote audio and video makes it a wonderful tool for seminars, lectures, and other forms of "distance education." Imagine sitting in on a lecture that's being given live thousands of miles away and even asking questions or contributing to a panel discussion.
Today, about 1,700 networks (in about 20 countries) are on the MBONE, making the MBONE approximately the size that the entire Internet was in 1990.
The size of the MBONE, compared to the Internet as a whole, is relatively small. As of February 1995, the Internet was home to 48,500 subnetworks, so the MBONE was available on roughly 3.5 percent of the Internet.
It is estimated that by 1996 or 1997, multicasting will be broadly supported in routers. When that happens, and upgraded routers are installed in place of unicast routers, the MBONE and the Internet will effectively be one entity.
Although anyone who has the right equipment can use the MBONE, the hardware and connectivity requirements for using the MBONE are much greater than what's available on the equipment that most Internet users have in their homes. A PC or Macintosh system coupled with a standard modem doesn't have enough computing power or bandwidth to send or receive MBONE transmissions.
You need a good deal of power to handle multicast IP. Today, multicasting software the behind the scenes tools for moving, encoding, decompressing, and manipulating multicast packets is available only for high end UNIX workstations, such as those from Sun, DEC, HP, IBM, and Silicon Graphics.
Even if users had the hardware to do multicasting today, another huge hurdle would prevent the MBONE from taking over the Internet: Most users don't have enough bandwidth. A multicast video stream of 1 to 4 frames per second eats about 128Kbps of bandwidth and gives you slow, grainy, bandwidth hogging video. (By comparison, television quality video scans at about 24 frames per second.) A video stream uses the same bandwidth whether it is received by 1 workstation or 100. Incidentally, 128Kbps is about nine times the speed of a 14.4Kbps modem. A dual channel ISDN line can move data at 128Kbps, so if you are one of the lucky few who have ISDN, you have barely enough bandwidth to receive multicast video.
There's a ceiling to the amount of information that can move around on the MBONE as a whole: 500Mbps (million bits per second). At full tilt, the MBONE itself can handle no more than four simultaneous videoconferencing sessions or eight audio sessions.
No one is actually in charge of the MBONE's topography of event scheduling. Much like the Internet itself, the MBONE's growth has been based on mutual cooperation between network service providers and users.
The MBONE community is active and open. Work on tools, protocols, standards, applications, and events is a cooperative international effort. Cooperation is essential due to limited bandwidth on many networks (for example, on intercontinental links).
Today, the MBONE offers users a certain degree of functionality as well as the opportunity to participate in and perhaps influence the gestation of a medium that will one day become predominant interactive multimedia multicast communications.
