it's still unclear if you're asking about how topology *or* routing
table looks like: topology is the real AS-level topology (e.g.
extracted either from skitter or routeviews), while the routing
table at every node consists of two parts: global part = shortest
path routes to landmarks; and local part = shortest path routes
to nodes closer to the given node rather than to their closest
landmarks. both parts are upper-bounded by sqrt(n) in the worst
case and precise algorithms are given on how to select landmarks
s.t. these bounds are satisfied. for more details see refs in
the paper.