Seattle (WA) - The reason why you cannot reach a specific web site at any given time can be very simple. Server and hosting issues, maintenance or the plain fact that a site has been discontinued are the most likely explanations why a site just won’t load. But there is another, more mysterious possibility: Black holes. A team at the University of Washington (UW) has begun mapping scenarios where information packets on the Internet simply disappear.

"There's an assumption that if you have a working Internet connection then you have access to all of the Internet," said Ethan Katz-Bassett, a UW doctoral student in computer science and engineering. "We found that's not the case."

Katz-Bassett has been working on a project called Hubble, a system that apparently is able to track what he refers to as information black holes. These are situations where a path between two computers does exist, but messages - a request to visit a Web site or an outgoing e-mail - get lost along the way. Katz-Bassett has published a Hubble map that enables users to monitor such black holes worldwide or simply type in a network address to check its status.

To determine a network status, Hubble sends test messages “around the world” to look for computers that can be reached from some but not the entire Internet, a situation that is described as “partial reachability”. Katz-Bassett said that short communication blips are ignored. However, if a problem surfaces in two consecutive 15-minute trials, it is listed as a “problem”. The research team found that more than 7% of computers worldwide experienced this type of error at least once during a three-week period in fall of 2007.

"When we started this project, we really didn't expect to find so many problems," said Arvind Krishnamurthy, a UW research assistant professor of computer science and engineering and Katz-Bassett's doctoral adviser. "We were very surprised by the results we got."

The name of the project, by the way, is no accident, as the researcher says it performs a service in an area that often is described as Internet astronomy. Just like the Hubble telescope can observe black holes in space, this software does similar work on the Internet by monitoring infrastructure and network performance.

Hubble is scheduled to being presented next week in San Francisco at the Usenix Symposium on Networked Systems Design and Implementation.

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