  The observation that real complex networks have internal structure has
important implication for dynamic processes occurring on such topologies. Here
we investigate the impact of community structure on a model of information
transfer able to deal with both search and congestion simultaneously. We show
that networks with fuzzy community structure are more efficient in terms of
packet delivery that those with pronounced community structure. We also propose
an alternative packet routing algorithm which takes advantage of the knowledge
of communities to improve information transfer and show that in the context of
the model an intermediate level of community structure is optimal. Finally, we
show that in a hierarchical network setting, providing knowledge of communities
at the level of highest modularity will improve network capacity by the largest
amount.
