The Internet has become an integral part of the ubiquitous information infrastructure of the modern society. But its global scale comes with a price: to route information packets from a given source to a given destination, routers maintain and constantly update an almost full view of the global network topology. This maintenance involves immense computation and information processing overhead, and has recently been widely recognized as one of the biggest scalability problems in the Internet.
In this talk we focus on the question if routing (or targeted information propagation) can be efficient in the Internet and networks alike without any global knowledge of the network topology. In other words we are interested if the Internet and other complex networks are navigable -- we say that a network is navigable if some simple routing strategies based only on local information available to a node are efficient. Such local information can be nodes' coordinates in some hidden metric spaces, and then nodes can route "greedily" by forwarding information to their neighbors closest to the destination in the hidden space. We show that if these spaces are hyperbolic, then networks built upon them naturally acquire scale-free node degree distributions and strong clustering. The topology of these networks are thus surprisingly similar to the topologies of real networks, including the Internet. Moreover, their navigability properties are essentially best possible: almost all greedy routes reach their destinations and follow the shortest paths in the network.