Big sites hoard links

The Internet is scale-free, meaning it is made up of a few nodes, or servers, that have many links, and many nodes with only a few links. It is also a small-world network -- you can get to any node via only a few links among adjoining nodes.

University of London researchers have uncovered another clue about the Internet's structure -- the rich-club phenomenon. Large, well-connected nodes have more links to each other than to smaller nodes, and smaller nodes have more links to the larger nodes than to each other.

The researchers found that 27 percent of connections are among the largest five percent of nodes, 60 percent connect the remaining 95 percent to the largest five percent, and only 13 percent of connections are between nodes not in the top five percent.

The findings suggest that the Internet is more dependent on the larger nodes than previously thought, which makes it more vulnerable to a targeted attack, according to the researchers.

The findings could contribute to better strategies for optimizing network traffic flow, network reliability and security, and building network topology simulators; it could be applied to practical systems into three years, according to the researchers.