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
network}s through a lightweight, highly {thread}ed 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 (http://www.eit.com/techinfo/mbone/mbone.html)}
(1994-11-11)