  Recently, many works focus on the implementation of collective communication
operations adapted to wide area computational systems, like computational Grids
or global-computing. Due to the inherently heterogeneity of such environments,
most works separate "clusters" in different hierarchy levels. to better model
the communication. However, in our opinion, such works do not give enough
attention to the delimitation of such clusters, as they normally use the
locality or the IP subnet from the machines to delimit a cluster without
verifying the "homogeneity" of such clusters. In this paper, we describe a
strategy to gather network information from different local-area networks and
to construct "logical homogeneous clusters", better suited to the performance
modelling.
