Much of the work on routing algorithms, particularly for 
multicast, which has been done in the past has used fairly simple 
models to generate the topological graph which represents the 
hosts in the network. Some such random graphs bear little resem
blance to data communication networks which are actually de
ployed. This paper proposes a more realistic model, 
incorporating hierarchy and redundancy, and is developed into a 
network generation algorithm. The approach described here can 
be developed to provide more refined models in the future, and 
the source code of an implementation is freely available from 
ftp.nexen.com/pub/papers.