The previous section describes methods to create hierarchical topologies
by hand. However, there is a script available in ns that converts
Georgia-tech's SGB-graphs into ns compatible hierarchical topologies.
Please refer to http://www-mash.CS.Berkeley.EDU/ns/ns-topogen.html
for downloading as well as instructions on using the hierarchical
33.3 Creating large Hierarchical topologies
See hier-rtg-10.tcl and hier-rtg-100.tcl in ~ns/tcl/ex for example
scripts of hier routing on small and large topologies