each leaf switch by two cables -->
<zone id="world" routing="Full">
<cluster id="bob_cluster"
prefix="node-" radical="100-101,119-120" suffix=".simgrid.org"
each leaf switch by two cables -->
<zone id="world" routing="Full">
<cluster id="bob_cluster"
prefix="node-" radical="100-101,119-120" suffix=".simgrid.org"