Measuring the Internet by Coordinating Distributed Vantage Points

Network operators and researchers rely on traceroute to measure Internet paths, monitor performance, and localize faults. This approach is not ideal, as traceroute, though extremely useful, is inherently limited in the data it can provide. We have designed practical techniques that dynamically coordinate distributed vantage points to yield substantially better measurements for the types of data currently provided by traceroute. To provide a richer view than is available with existing tools, our measurement techniques take advantage of topological relationships vantage points have to each other and to destinations. We propose to empirically demonstrate that these techniques work on the Internet without special support and often provide ideal information in scenarios in which people now depend on traceroute’s limited information. We also describe applications we plan to build that utilize our novel measurement techniques. 1. BACKGROUND AND MOTIVATION As we depend on the Internet more and more, it is critically important that it functions well. However, Internet communication depends on complex interactions between multiple protocols and multiple autonomous domains, making it difficult to guarantee high performance or understand the causes of problems. With limited visibility or control outside their local network, network operators and researchers make measurements to monitor the Internet and attempt to understand the wide area. Network operators rely on the traceroute tool to ensure the proper functioning of their networks and to troubleshoot problems. Researchers use traceroute measurements to study properties of the Internet and to build useful systems. Traceroute, which measures the router-level path from the source to a specified destination, is the “number one go-to tool” for troubleshooting problems [13]. Operators and researchers use traceroute to determine paths [10, 8], locations of failures [10, 14], laten∗This extended abstract describes the author’s work-inprogress thesis research. cies [11, 9], and (via DNS names) geographic locations of routers [10, 9]. Although traceroute is an extremely useful measurement tool, it does not provide complete information, and the limits on what it provides restrict the accuracy of inferences made with it. As networks and operators have become more sophisticated, few problems encountered are simple to diagnose and resolve [13], and existing diagnostic techniques no longer suffice given the more complicated problems that dominate. The majority of Internet communication is bidirectional, and most paths are asymmetric [2], yet traceroute measures only the forward path, forcing systems into the unrealistic assumption of path symmetry [8, 15]. One cannot differentiate forward and reverse path failures using traceroute, limiting our ability to diagnose Internet anomalies [14, 15]. Traceroute measures the round-trip latency to each hop, but many systems want link or one-way latencies [9, 8], which are difficult to estimate because of path asymmetry. Many IP addresses do not have DNS names with geographic meaning [3], forcing systems to rely on limited data [8, 9]. Ideally, traceroute would give (1) the forward and reverse path, (2) the link causing any failure, (3) the latency of every link, and (4) each hop’s geographic location.