I Know What Your Packet Did Last Hop: Using Packet Histories to Troubleshoot Networks

The complexity of networks has outpaced our tools to debug them; today, administrators use manual tools to diagnose problems. In this paper, we show how packet histories—the full stories of every packet’s journey through the network—can simplify network diagnosis. To demonstrate the usefulness of packet histories and the practical feasibility of constructing them, we built NetSight, an extensible platform that captures packet histories and enables applications to concisely and flexibly retrieve packet histories of interest. Atop NetSight, we built four applications that illustrate its flexibility: an interactive network debugger, a live invariant monitor, a path-aware history logger, and a hierarchical network profiler. On a single modern multi-core server, NetSight can process packet histories for the traffic of multiple 10 Gb/s links. For larger networks, NetSight scales linearly with additional servers and scales even further with straightforward additions to hardwareand hypervisor-based switches.