What is the MBONE?

MBONE stands for the Multicast Backbone on the Internet. IP-Multicast is the class-D addressing scheme in IP developed by Steve Deering at Xerox PARC. The multicast backbone was adopted at the IETF March 1992 meeting and acquired the name MBONE after the July 1992 IETF meeting. Class-D IP addresses range from 224.0.0.0 to 239.255.255.255, and the MBONE based audio video conferences have been allocated the address range of 224.2.*.* by the IANA. A new proposal to IANA has also been submitted recently for allocating a set of addresses for administratively scoped multicast, the range is 239.0.0.0 to 239.255.255.255.

The first multicast tunnel was established between BBN and Stanford University in the summer of 1988. Tunneling was originally meant just as a short term hack until the core routers knew about IP multicasting. Here is an original public email contributed by David Waitzman (djw@bbn.com) that captures the moment.

IP Multicast-based routing facilitates distributed applications to achieve time-critical "real-time" communications over wide area IP networks through a lightweight, highly threaded model of communication. The IP Multicast routers (referred to as "mrouters") take the responsility of distributing and replicating the multicast data stream to their destinations as opposed to individual IP hosts. The MBone topology of mrouters is designed in such a manner that it facilitates "efficient" distribution of packets without congesting any node inappropriately.

RFC-1112 fully describes the details. More details are available in the references section of this guide.

Several MBONE topology maps are available at ftp://ftp.isi.edu/mbone/:

Topology map, PostScript version
Topology map, GIF image
Topology map, Small GIF image

Last Modified 8/20/95
Created by Vinay Kumar