Mbone is short for multicast backbone on the internet, and is an extension to the internet designed to support IP multicasting, or the transmission of data packets to multiple addresses. Most of this traffic is streaming audio and video which, like radio and TV broadcasts, is sent to many people at once. The Mbone was established in 1994 by the Internet Engineering Task Force.
Mbone is likely to go obsolete with the adoption of IPv6 which supports multicasting by default.