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Ethan Katz-Bassett graduated from Williams College in 2001, spent 3 years as a ski instructor in Taos, New Mexico, then decided to go to graduate school. He is working towards a PhD in Computer Science at the University of Washington and expects to graduate in about a year. Ethan’s dissertation work is on measurement-based global-scale Internet monitoring systems, and he’ll be speaking about Hubble, one such system he developed. Hubble identifies and monitors Internet black holes, when a network is reachable from some locations and not others for extended periods of time. It has been running for almost a year now, and one of the goals of the project is to eventually have a measurement deployment with probers located in every edge network on the Internet.

Ethan’s primary interests are in networks and distributed systems, especially Internet measurement. He is interested in how we can use measurements from distributed vantage points to infer otherwise hidden properties of the Internet. He likes to build real systems that provide benefits to end-users and network operators.

Global reachability — when every address is reachable from every other address — is the most basic goal of the Internet. It was specified as a top priority in the original design of the Internet protocols, ahead of high performance or good quality of service, with the philosophy that “there is only one failure, and it is complete partition.” However, this is not always the case in practice; traffic may disappear into black holes and consistently fail to reach the destination. This is problematic when the outages are not simply transient, as an operator generally has little visibility into other ASes to discern the nature of an outage and little ability to check if the problem exists from other vantages points.

We present Hubble, a system that operates continuously to find Internet reachability problems in which routes exist to a destination but packets are unable to reach the destination. Hubble allows us to characterize global Internet reachability by identifying how many prefixes are reachable from some vantages and not others, how often these problems occur, and how long they persist. Whereas previous work focused on reachability within the narrower context of an AS, testbed, or set of clients, or obtained breadth by monitoring routes only via BGP, Hubble monitors the data-path to prefixes that cover 89% of the Internet’s edge address space at a 15 minute granularity. Key enabling techniques include a hybrid passive/active monitoring approach and the synthesis of multiple information sources, including historical data and spoofed probes to isolate failures.

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