Mbone

Mbone

(Multicast backBONE) A group of servers throughout the Internet that support the IP multicast protocol (one-to-many) and allow for live audio and video transmission. When it is necessary to leave the Mbone and traverse a part of the Internet that does not support multicast packets, the packets are tunneled into normal packets. Mbone routers (mrouters) encapsulate the multicast packets into unicast packets and unencapsulate them on the receiving side.

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MBONE - 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. It is best if the workstations can be dedicated to the multicast routing function to avoid interference from other activities and so there will be no qualms about installing kernel patches or new code releases on short notice. Since most MBONE nodes other than endpoints will have at least three tunnels, and each tunnel carries a separate (unicast) copy of each packet, it is also useful, though not required, to have multiple network interfaces on the workstation 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. FAQ.