Topology discovery by active probing

As the Internet has grown, so has the challenge of accurate measurement and modeling of its topology. Commonly used but coarse methods of measuring topology, e.g., BGP tables, suffer from several limitations. To pursue more accurate empirically-based topology modeling, in 1998 CAIDA began its Macroscopic Topology Project, which focuses on actively measuring topology and round trip time (ITT) information across a large cross-section of the commodity Internet. In this paper we describe CAIDA's topology measurement architecture and our analysis and visualization tools. We describe differences between IP and AS (BGP-based) granularities of topology modeling, including advantages and limitations of both, as well as how correlation between both types of data can yield more relevant insights. We introduce four new visualization metaphors for handling macroscopic topology data, as well as a tool for aggregating multiple IP addresses into the same physical router. We highlight results of our analyses, in particular relationships between RTT and topology data, and how source and destination selection and geopolitical boundaries affect those relationships.