This study looks at how the Internet is organized in terms of function, as well as how it's connected. While efforts have been made previously to plot the topological structure in terms of the connections between Internet nodes, none have taken into account the role that these connections play. As Shar Carmi, a physicist who took part in this research at the Bar Ilan University explains, "Some nodes may not be as important as other nodes".
This image shows the hierarchical structure of the Internet, based on the connections between individual nodes (such as Computer Networks or Internet Service Providers). Three distinct regions are apparent: an inner core of highly connected nodes, an outer periphery of isolated networks, and a mantle-like mass of peer-connected nodes. The bigger the node, the more connections it has. Those nodes that are closest to the center are connected to more well-connected nodes than are those on the periphery. This study also demonstrates the scale-free nature of the Internet which has been argued by several researchers.
The core: At the center of the Internet are about 80 core nodes through which most traffic flows. Remove the core, and 70 percent of the other nodes are still able to function through peer-to-peer connections.
The periphery: At the very edge of the Internet are 5,000 or so isolated nodes that are the most dependent upon the core and become cut off if the core is removed or shut down. Yet those nodes within this periphery are able to stay connected because of their peer-to-peer connections.
For the visualizations, the authors used the Lanet-vi program, by Ignacio Alvarez-Hamelin et al.