Our recent study of the evolution of the Internet ecosystem over the last twelve years (1998-2010) appeared in the IEEE/ACM Transactions on Networking in October 2011. Why is the Internet an ecosystem? The Internet, commonly described as a network of networks, consists of thousands of Autonomous Systems (ASes) of different sizes, functions, and business objectives that interact to provide the end-to-end connectivity that end users experience. ASes engage in transit (or customer-provider) relations, and also in settlement-free peering relations. These relations, which appear as inter domain links in an AS topology graph, indicate the transfer of not only traffic but also economic value between ASes. The Internet AS ecosystem is highly dynamic, experiencing growth (birth of new ASes), rewiring (changes in the connectivity of existing ASes), as well as deaths (of existing ASes). The dynamics of the AS ecosystem are determined both by external business environment factors (such as the state of the global economy or the popularity of new Internet applications) and by complex incentives and objectives of each AS. Specifically, ASes attempt to optimize their utility or financial gains by dynamically changing, directly or indirectly, the ASes they interact with.
The goal of our study was to better understand this complex ecosystem, the behavior of entities that constitute it (ASes), and the nature of interactions between those entities (AS links). How has the Internet ecosystem been growing? Is growth a more significant factor than rewiring in the formation of new links? Is the population of transit providers increasing (implying diversification of the transit market) or decreasing (consolidation of the transit market)? As the Internet grows in its number of nodes and links, does the average AS-path length also increase? Which ASes engage in aggressive multihoming? Which ASes are especially active, i.e., constantly adjust their set of providers? Are there regional differences in how the Internet evolves?