The Routing Over Large Clouds Mailing List Archive by date

[Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>]

> I think you folks just talked past each other.  Sam said, "over a simple
> ATM star topology".  He was, if I understand him correctly, assuming that
> the VCs converge at a single point in the "logical center" of the network.

In WAN environment on Earth with N nodes and geographical size
L, such topology costs O(L*N) for wiring, while mesh like one
costs only O(L*sqrt(N)).

That is, the architecture is impractical in large cloud WAN,
where N is, by definition, large.

Note that, in Sam's case, N is not so large.

> In the Frame Relay environment, this continues to be a very common and
> practical way to construct internetworks, notwithstanding the hype you read
> in the trade rags.

I don't think Fram Relay is practical.

But, anyway, as long as the purpose is the construction of the
Internet backbone where small number of routers over geographically
large area are connected, the topology might not be fatally bad.

For large cloud environment where routers can't divide subnets,
the topology is impractical.

							Masataka Ohta