Mbone (short for "multicast backbone") was an experimental backbone and virtual network built on top of the Internet for carrying IP multicast traffic on the Internet. It was developed in the early 1990s and required specialized hardware and software.

Virtual Internet Backbone for Multicast IP. IP-Multicast is the class-D addressing scheme in IP implemented by Steve Deering at Xerox PARC. It was adopted at the IETF March 1992 meeting and acquired the name MBONE after the July 1992 IETF meeting. IP Multicast-based routing allows distributed applications to achieve real-time communication over IP {wide area networks} through a lightweight, highly threaded model of communication. Each network-provider participant in the MBONE provides one or more IP multicast routers to connect with tunnels to other participants and to customers. The multicast routers are typically separate from a network's production routers since most production routers don't yet support IP multicast. Most sites use workstations running the mrouted program, but the experimental MOSPF software for Proteon routers is an alternative. Ideally, the machines running mrouted should be dedicated to this task, for reasons of real-time performance and ease of installing kernel patches. Since most intermediate nodes have at least three tunnels, each carrying a separate (unicast) copy of each packet, it is also useful to have multiple network interfaces so it can be installed parallel to the unicast router for those sites with configurations like this: +----------+ | Backbone | | Node | +----------+ | ------------------------------------------ External DMZ Ethernet | | +----------+ +----------+ | Router | | mrouted | +----------+ +----------+ | | ------------------------------------------ Internal DMZ Ethernet This configuration allows the mrouted machine to connect with tunnels to other regional networks over the external DMZ and the physical backbone network, and connect with tunnels to the lower-level mrouted machines over the internal DMZ, thereby splitting the load of the replicated packets. The mrouted machine would not do any unicast forwarding. Note that end-user sites may participate with as little as one workstation that runs the packet audio and video software and has a tunnel to a network-provider node. RFC 1112 gives the details. mbone/mbone.html">FAQ (http://eit.com/techinfo/mbone/mbone.html). (1994-11-11)

(MBONE) A virtual network on top of the Internet which supports routing of IP multicast packets, intended for multimedia transmission. MBONE gives public access {desktop video} communications. The quality is poor with only 3-5 frames per second instead of the 30 frames per second of commercial television. Its advantage is that it avoids all telecommunications costs normally associated with teleconferencing. An interesting innovation is the use of MBONE for audio communications and an electronic "whiteboard" where the computer screen becomes a shared workspace where two physically remote parties can draw on and edit shared documents in real-time. (1994-10-27)