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Mbone (short for "multicast backbone") was an experimental backbone for IP multicast traffic across the Internet developed in the early 1990s. It required specialized hardware and software. Since most Internet routers have IP multicast disabled due to concerns of bandwidth tracking and billing, the Mbone evolved to connect multicast-capable networks over the existing Internet infrastructure. The commercialization of multicast routers is difficult because there are no efficient access control capabilities to the multicast trees (multicast routers and their protocols), and because Internet service providers have difficulty computing charges for multicast traffic.
Mbone is a virtual network built on top of the Internet, invented by Van Jacobson, Steve Deering and Stephen Casner in 1992. The purpose of Mbone is to minimize the amount of data required for multipoint audio/video-conferencing. Mbone is free; it uses a network of mrouters that can support IP multicast, and it enables access to real-time interactive multimedia on the Internet. Many older routers do not support IP multicast. To cope with this tunnels must be set up on both ends; also known as a tunneling protocol: multicast packets are encapsulated in unicast packets and sent through a tunnel. Mbone uses a small subset of the class D IP address space (126.96.36.199–188.8.131.52) assigned for multicast traffic. Mbone uses 184.108.40.206 for multimedia conferencing.
- topology: combination of mesh and star networks
- IP addresses: 220.127.116.11; routing schemes: DVMRP, MOSPF
- session registration: IGMP
- traffic requirement: audio 32-64 kbit/s, video 120 kbit/s
Mbone tools 
- Videoconferencing: vic -t ttl destination-host/port (supports: NV, H.261, CellB, MPEG, mJPEG)
- Audioconferencing: vat -t ttl destination-host/port (supports: LPC, PCMU, DVI4, GSM)
- Whiteboard: wb destination-host/port/ttl
- Session Directory: sdr
A November 1994 Rolling Stones concert at the Cotton Bowl in Dallas with 50,000 fans was the "first major cyberspace multicast concert." Mick Jagger opened the concert by saying, "I wanna say a special welcome to everyone that's, uh, climbed into the Internet tonight and, uh, has got into the M-bone. And I hope it doesn't all collapse."
A year later the Mbone is used, this time symmetrically (simultaneous transmission and reception without hierarchy among participants), for a first experience of real-time graphical interaction without the intermediary of any Center (Poietic Generator).
Mbone is currently of practical use for shared communication such as videoconferences or shared collaborative workspaces. It is not generally connected to Internet service providers, but often to universities and research institutions. Some other projects and network testbeds, such as Internet2's Abilene Network, have made Mbone obsolete.
A recent application with support over Mbone was Virtual Room Videoconferencing System (VRVS).
See also 
- CastGate—an attempt at providing connectivity to the multicast network for hosts which have none
- Lewis, Peter H. "Peering Out a 'Real Time' Window". The New York Times, 8 February 1995. Retrieved 26 August 2009.
- MBONE: Multicasting Tomorrow's Internet: Classic book about MBONE, by Kevin Savetz, Neil Randall, and Yves Lepage, complete on-line
- IETF MBONE Deployment working group
- How to connect to the MBone
- What is MBONE? From Webopedia
- Making the MBone Real—Ajit S. Thyagarajan, Stephen L. Casner, and Stephen E. Deering, Proc. INET '95. Internet Society. May 10, 1995