traffic mimics earthquakes
Technology Research News
Earthquakes and the Internet may seem very
different, but they do have one thing in common. They're both complex
systems whose behavior is currently very difficult to predict.
Seismologists, statistical physicists and complex systems scientists around
the world have long studied the ways the earth's many fault-lines interact
with each other and the slow-moving tectonic plates that underlie the
earth's crust in hopes of eventually figuring out ahead of time when and
where earthquakes could occur.
Meanwhile, as the Internet has grown, computer scientists have studied
the Net's structure and the ebbs and flows of its traffic in order to
make network travel more efficient.
Complex system science, however, is still very much in its infancy, according
to Dion Weatherley, a geophysicist at the University of Queensland in Australia.
"There is no comprehensive 'complex systems theory' as yet," he said.
"Scientists are gathering observations at an incredible rate, but... no
one has managed to comprehend all these observations within a single theoretical
Researchers from Tsukuba and Nihon universities in Japan may have uncovered
a clue. They have shown that the self-organizing behavior of bits traveling
down the Internet's communications lines shares some mathematical characteristics
with the self-organizing behavior of the many cracks, or faults, in the
earth's crust. "Although earthquakes and the Internet are apparently very
different, they exhibit similar behaviors," said Sumiyoshi Abe, an associate
professor of physics at University of Tsukuba in Japan.
Recent research into the Internet's structure has proved that the network
has a scale-free, or power law nature, meaning it naturally organizes
so that a few sites, or nodes have many links to other nodes, and the
vast majority of nodes have only a few links. The discovery of this Internet
structural trait "reminded me of the scale-free natures of earthquakes
and financial markets," said Abe.
Self-organizing complex systems all have certain properties in common.
The systems have a large number of individual elements, these elements
interact in ways that affect nearby elements and in other ways that affect
all of the elements in the system, and the system's behavior cannot be
predicted simply by studying the individual elements and their interactions,
according to Weatherley.
In the case of earthquakes, each fault represents an individual element,
said Weatherley. "An earthquake along any given fault changes the pressure
on surrounding faults, either promoting or inhibiting earthquakes of those
faults," he said. At the same time, the motion of the earth's tectonic
plates increases the pressure on all faults within the plate's region.
"This is a global interaction," he said.
In the case of the Internet, each site is connected to the whole through
servers, which host web pages, and routers, which coordinate traffic.
The servers and routers themselves also form a hierarchical clustering
structure, said Abe.
To find connections between Internet traffic patterns and earthquake behavior,
the researchers measured minute changes in digital traffic by sending
a series of signals from one computer to a site on the Internet and back.
The simple ping signals were emitted every second and traveled through
10 different routers before the signals eventually reached the destination
computer. The researchers were able to measure frequent changes in Internet
congestion by measuring the time it took a series of signals to complete
a round trip.
The results showed that the Internet, like the earth's network of faults,
exhibits criticality -- a condition of sudden and drastic change. "Sudden
drastic congestion leads to a large value of the round trip time of the
ping signal, which is identified with a main shock," said Abe. The researchers
referred to these sudden, drastic traffic changes as Internetquakes.
Criticality exists whenever there is a phase transition. It happens, for
example, when water suddenly turns to ice as it reaches 0 degrees Celsius.
"Nowadays, this concept is employed in a wider sense for complex systems,"
The traffic snapshots showed that the Internet was constantly changing
on two very different time scales. The longer events were user sessions
on the net, which typically lasted an hour. The short quake events lasted
about one tenth of a second.
The two-tiered timing resembles seismic activity, Abe said. Faults build
up energy over a time-scale of many years, then release it as an earthquake
over a few seconds.
Earthquakes follow the Gutenberg-Richter law, which says that the frequency
of earthquakes corresponds to their magnitude. Specifically, the logarithm,
or exponent, of the cumulative frequency of earthquakes is proportional
to their magnitude. The researchers found that the Internetquakes followed
similar mathematics: the round trip time, which represented the magnitude
of the Internetquake, corresponded in the same way to the frequency of
the quakes, according to Abe.
The researchers' experiments also showed similar mathematics between Internet
activity and earthquake aftershock activity, said Abe. "We have also discovered
the Omori law, known for aftershocks in seismology, [is true for] Internetquakes,"
he said. Omori's law describes the timing of earthquake aftershocks, and
is also true of financial market crashes. Omori's law could be universal
for complex systems, according to Abe.
The researchers are working to eventually use the Internetquake measurements
to monitor the general health of Internet traffic, Abe said. "The network
is healthy as long as it exhibits the scale-free nature, which is essential
for the system to be robust against random errors, breakdowns and attacks,"
They are also continuing to compare earthquakes and Internet traffic activity
in order to better understand and possibly predict catastrophic behaviors,
said Abe. The study of Internetquakes could eventually shed new light
on earthquakes, he said.
The Internet offers a big advantage to complex system researchers. It
is much easier to trace traffic interactions over the communications lines
that make up the Internet than to trace networks of fault patterns in
the earth. The researchers' experiments were relatively simple, although
they required a sizable amount of computer power to analyze large numbers
In contrast, there are considerable timing and logistics challenges in
measuring faults. "Earthquakes involve processes occurring over a very
broad range of spatial and temporal scales, from microns and seconds to
thousands of kilometers and many hundreds of years," said Weatherley.
Even more problematic, "the majority of the processes involved are not
directly measurable because they occur at great depths within the earth's
crust -- typically more than five kilometers deep and up to... 600 kilometers
deep," Weatherley said. "Due to the lack of observational data, progress
in developing a comprehensive scientific theory of earthquakes has been
greatly hampered and accurate predictions of earthquakes cannot be made,"
Whether the self-organizing properties of Internet traffic and the earth's
crust truly follow the same mathematical laws is still an open question,
said Weatherley. "The power-law distribution of round-trip times is certainly
evidence that the Internet is a self-organizing complex system," he said.
However, "evidence for a link between earthquakes and Internet traffic
flow is not convincing," Weatherley said.
The researchers need to show "much more clearly that there are similarities
between interacting fault systems and the Internet traffic flow interactions
in order to claim that studying these 'Internetquakes' can provide insight
into earthquakes," said Weatherley.
The close monitoring of Internetquake patterns may eventually contribute
to making the Internet more efficient, said Abe. "We expect that further
study in this direction will allow us to control or optimize the network
behavior," he said. These methods could be ready to optimize real networks
like the Internet in about 10 years, he said.
The researchers are also continuing to investigate similarities among
earthquakes, the Internet, and also financial market crashes, said Abe.
"It would appear that earthquakes, Internetquakes and financial market
crashes are all fundamentally a manifestation of the same type of complex
systems," he said.
Abe's research colleague was Norikazu Suzuki. The research was funded
by University of Tsukuba and Nihon University.
Timeline: 10 years
TRN Categories: Applied Technology; Internet; Physics
Story Type: News
Related Elements: Technical paper, "Gutenberg-Richter Law
for Internet Quakes," posted at the arXiv physics preprint archive at
arXiv.org/abs/cond-mat/ ; Technical paper, "Omori's law in the Internet
traffic," posted at the arXiv physics preprint archive at arxiv.org/PS_cache/cond-mat/pdf/0206/0206453.pdf
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