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NANOG Meeting Presentation Abstract

Scriptroute: A Public Internet Measurement Facility
Meeting: NANOG26
Date / Time: 2002-10-29 4:30pm - 4:50pm
Room: Hellman/Williams/O\'Neill
Presenters: Speakers:

Neil Spring, Department of CSE, University of Washing

Neil Spring is a graduate student at the University of Washington, focusing on techniques for measuring network link and path properties. The latest project for Neil and his colleagues is Rocketfuel, an ISP toplogy mapping engine.
David Wetherall, Department of CSE, University of Washington.
Tom Anderson, Department of CSE, University of Washington.
Abstract: We present Scriptroute, a new system that allows network operators and researchers to make measurements from remote vantage points.

Existing systems such as NIMI, the National Internet Measurement Infrastructure, provide much of the needed functionality, but not all. NIMI provides the advantages of dedicated hardware that can be used for a wide range of network measurements. In return, users must possess credentials, which creates a barrier that limits access to a small community of users trusted by the administrator. Thus these systems do not help unaffiliated users like a network operator trying to debug poor network performance.

The popularity of Web-accessible traceroute servers offers a different solution. Several hundred public traceroute servers are available, constituting the largest de facto Internet measurement facility. These servers are typically used to debug two-way connectivity problems, providing indirect benefit to the traceroute server host. They are also easy to secure, because they provide only limited functionality and local administrators retain control to deny access to abusive users. As a result, many network operators now contribute traceroute servers.

However, traceroute servers provide limited functionality -- only a hop-by-hop TTL test -- and have significant drawbacks when used as a measurement system. They are difficult to coordinate, as they were not designed with programmed access in mind. More importantly, there are many non-intrusive performance tests that are not supported by traceroute servers, such as available bandwidth, capacity, and congestion. In short, it is clear that a much richer diagnostic and measurement capability would be possible with a general-purpose tool.

Our goal is to combine the best of both worlds: the flexibility to run a wide variety of different measurement tools with the general availability of traceroute servers. We begin with the safety properties of traceroute servers: we design the system to prevent misuse, even at the cost of disallowing some kinds of useful measurements. We call our system Scriptroute. We use scripting for flexibility, both to make it easy to implement measurement tools and to coordinate measurements across multiple servers. For security, we use sandboxing and local control over resources to protect the measurement host, and rate-limiting and filters that block known attacks to prevent misuse of the network. Further, because network measurements often send probe traffic to random Internet hosts and administrators sometimes mistake measurement traffic for an attack, we provide a mechanism for sites to block unwanted measurement traffic.

We have implemented the Scriptroute design and deployed it on servers across 33 PlanetLab sites. The Scriptroute code is available and can be used for local measurement script development or for participation in the global system. We have used the system to measure routing trees around the destination. Early experience suggests that our system will be flexible enough to implement a variety of new measurement tools despite its security restrictions, that access to many remote vantage points makes the system valuable, and that scripting is an apt choice for expressing and combining measurement tasks.

For more information, see:

Files: pdfNeil Spring Presentation(PDF)
youtubeScriptroute: A Public Internet Measurement Facility
Sponsors: None.

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