The Missing AS Links and Their Impact On the Internet Topology Model

The topology of the Internet at the Autonomous System (AS) level is not yet fully discovered despite significant research activity. The community still does not know how many links are missing, where these links are and finally, whether the missing links will change our conceptual model of the Internet topology. An accurate and complete model of the topology is critical for protocol design, performance evaluation and analyses. The goal of our work is to develop methodologies and tools to identify and validate such missing links between ASes. We develop several methods and identify a significant number of missing links, particularly of the peerto-peer type. In a nutshell, our study brings to light three major properties of the missing AS links: (1) most of the missing AS edges are of the peer-to-peer type, (2) most of the missing AS edges appear in IRR, and (3) most of the missing AS edges are incident at IXPs. In more detail, we make the following main contributions. First, we examine the Internet Exchange Points (IXPs) which have not been sufficiently explored in topology-oriented studies. We develop an improved method to identify IXP participants, and the edges among them, and find a significant number of peer-to-peer AS edges that do not appear anywhere else. Second, we conduct a cross-comparison and synthesis of most available sources of information: BGP routing tables, Internet Routing Registries, and traceroute data. In addition, we develop a tool to validate the existence of potential edges. Finally, we study the impact of the new edges.