What is the topology of the MBONE?

We anticipate that within a continent, the MBONE topology will be a combination of mesh and star: the backbone and regional (or mid-level) networks will be linked by a mesh of tunnels among mrouted machines located primarily at interconnection points of the backbones and regionals. Some redundant tunnels may be configured with higher metrics for robustness. Then each regional network will have a star hierarchy hanging off its node of the mesh to fan out and connect to all the customer networks that want to participate.

Between continents there will probably be only one or two tunnels, preferably terminating at the closest point on the MBONE mesh. In the US, this may be on the Ethernets at the two FIXes (Federal Internet eXchanges) in California and Maryland. But since the FIXes are fairly busy, it will be important to minimize the number of tunnels that cross them. This may be accomplished using IP multicast directly (rather than tunnels) to connect several multicast routers on the FIX Ethernet.

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