An outgrowth of the first two IETFaudiocast experiments, in which live audio and video were multicast from the IETF meeting site to destinations around the world. The idea is to construct a semipermanent IP multicast "testbed" to carry the IETF transmissions and to support continued experimentation between meetings. It is a cooperative, volunteer effort.
The Mbone itself is a virtualnetwork. It is layered on top of portions of the physical Internet, to support the routing of IP multicast packets. That function has not yet been integrated into many production routers. The Mbone network is composed of "islands" that directly support IP multicast, such as multicast LANs (like Ethernet). These are linked by virtual point-to-point "tunnels." The tunnel endpoints are typically workstation-class machines that have operating system support for IP multicast and run the "mrouted" multicast routing daemon.