Robustness of the Internet


Router-level topology of Abilene. Each vertex represents a router, and each link represents a physical connection; however, each physical connection can support many virtual connections, giving the appearance of greater connectivity at higher layers of the IP stack. End-user networks are shown in white, peering networks are shown in blue, and high-degree routers can only be found at the network periphery (not shown).

John Doyle and his colleagues published a very interesting paper on the structure of the internet and its implications for robustness. It is a popular belief that the structure of the Internet follow a scale free distribution of the number of connections, which then results in being sensitive to target attacks at the hubs. Doyle et al. dig deeper in to the real structure of the internet and falsify this myth. Indeed the number of connections follow a scale free distribution, but there are various ways to derive such a distribution. Doyle et al. find that the components of the internet with the most connections are not the crucial hubs of the internet.

Doyle et al. define an alternative model to generate networks structures of the internet (an alternative to the preferential attachment models). This alternative model is based on the highly optimized tollerance (HOT) concept and includes specific technological (bandwidth) and economic (costs) constraints. The resulting model generates statistics more in line with the real internet, and an important finding is that this structure is robust to targeted attacks to highly connected nodes.

Reference
John C. Doyle, David L. Alderson, Lun Li, Steven Low, Matthew Roughan, Stanislav Shalunov, Reiko Tanaka, and Walter Willinger (2005) The “robust yet fragile” nature of the Internet, Proceedings of the National Academy of Sciences of the United States of America 102: 14497-14502

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