hierarchical routing
The complex problem of routing on large networks can be
simplified by breaking a network into a hierarchy of smaller
networks, where each level is responsible for its own routing.
The Internet has, basically, three levels: the backbones, the
mid-levels, and the stub networks. The backbones know how to
route between the mid-levels, the mid-levels know how to route
between the sites, and each site (being an autonomous system)
knows how to route internally. See also Exterior Gateway
Protocol, Interior Gateway Protocol, transit network.
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