  Routing information through networks is a universal phenomenon in both
natural and manmade complex systems. When each node has full knowledge of the
global network connectivity, finding short communication paths is merely a
matter of distributed computation. However, in many real networks nodes
communicate efficiently even without such global intelligence. Here we show
that the peculiar structural characteristics of many complex networks support
efficient communication without global knowledge. We also describe a general
mechanism that explains this connection between network structure and function.
This mechanism relies on the presence of a metric space hidden behind an
observable network. Our findings suggest that real networks in nature have
underlying metric spaces that remain undiscovered. Their discovery would have
practical applications ranging from routing in the Internet and searching
social networks, to studying information flows in neural, gene regulatory
networks, or signaling pathways.
