Broadband customers and US military systems are the most common victims of
an online phenomenon researchers have dubbed "dark address space," which
leaves some 100 million hosts completely unreachable from portions of the
Internet.
For a variety of reasons ranging from contract disputes among network
operators to simple router mis-configuration, over five percent of the
Internet's routable address space lacks global connectivity, according to
the results of a three-year study by researchers at Massachusetts-based
Arbor Networks, to be released Tuesday.
"Popular belief holds that the Internet represents a completely connected
graph," says Craig Labovitz, Arbor Networks' director of network
architecture. "It turns out that's just not true."
Anecdotal evidence has long hinted at the existence of dark address space,
but the researchers shed light on the subject by continuously gathering and
analyzing core routing tables for three years. In the end, they found that
for much of the Internet, the shortest path between two points doesn't
exist.
The most common factors contributing to dark address space: aggressive
route filtering by network operators seeking to ease the load on
equipment, and accidental mis-configuration. US military sites frequently
fall into the shadow zone because they often occupy neglected 'Milnet'
address blocks dating back to the Internet's stone age. Why cable modem
customers also top the list remains one of the unsolved mysteries in the
project, says Labovitz, who describes the research findings as preliminary.
Murky Crime
Despite the large number of hosts that fall into the partitioned space,
the phenomenon is generally not noticeable to average Internet users
because most Netizens only use a tiny portion of the Net. "Most people
access five or ten web sites," Labovitz says.
The study was conducted by Labovitz, Michael Bailey and Abha Ahuja. [...]
[For IP archives see:
http://www.interesting-people.org/archives/interesting-people/] [David Farber via risks-digest Volume 21, Issue 75]
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