Researchers at the University of Southern California
Information Sciences Institute, one of the birthplaces of the
Internet decades ago, have just completed and plotted a
comprehensive census of all of the more 2.8 billion
allocated addresses on the Internet -- the first complete
effort of its kind in more than
two decades, they say.|
"An Internet census," explains John Heidemannn, an ISI
project leader who also has an appointment in the USC
Viterbi School of Engineering computer science department,
"is just that: every single assigned address in the entire
Internet was sent a
The technical name for an Internet probe, more commonly
called a "ping" is an "Internet Control Message Protocol
(ICMP) echo request
packet." It took some 62 days to send almost 3 billion of
these from four
machines, an effort carried out by Heidmann's ISI
collaborator Yuri Pradkin.
A detailed account of the research is at http://www.isi.edu/ant/address/index.html
Many (61 percent) of the pings received no response at all.
Many others got a "do not disturb" or "no information
available" response that many network administrators
program into their routers and firewalls. Some of the non-
replies were probably also due to firewalls intentionally
blocking the pings. Still, as the census went on, millions of
sites did respond, positively and negatively, and a unique
Internet atlas took shape.
Below: Pradkin, left, and Heidemann. (click
image for larger view)
The atlas is not geographic, though geographic areas (North
American, Europe, etc) show up on it. Instead, it is
numerical, building on the mathematical structure of the
Internet address system.
Each Internet address is a number between 0 and 2 to the
32nd power (4,294,967,295), usually written in "dotted-
decimal notation" as four base-10 numbers separated by
periods; for example 18.104.22.168. Each number
represents one 8-bit part of the whole address.
These addresses appear in the chart as a grid of squares,
each square representing all the addresses beginning with
the same first number ("128," in the preceding example).
map is arranged in not in simple ascending numerical order,
but instead in
a looping pattern called a Hilbert curve, which keeps
adjacent addresses physically near each other, and also
makes it possible to zoom seamlessly in to show
greater detail. "The idea of using a Hilbert curve actually
came from a web comic, xkcd," said Heidemann.
The smallest feature the map shows is a singe pixel, which is
records averaged responses from some 65,536 (2 to the
16th) addresses. The averaging is conveyed by color coding,
with all-positive responses showing up as brilliant green, all-
as brilliant red, equal numbers as brilliant yellow,
with brilliance decreasing down to dim shades in areas
where fewer addresses respond.
The map presents a novel census view of the visible
"To our knowledge," said Heidemann," the only other census
of the Internet was in
1982," when the Intenet consisted of 315 allocated
Heidemannn and Pradkin have also plotted a second
rendering where each pixel represents a single address.
When printed out at laser-printer resolution, this map that
literally shows every address in the Internet took up a 9x9
foot space on a corridor wall in at a recent conference.
(see photo below)
The project is continuing. Heidemann hopes to continue
censuses to create not just a snapshot -which is what the
current map is - but a dynamic movie of Internet evolution,
which can aid in detecting and monitoring trends. He and his
are intensively studying the census results working toward
While the new census is the first they have visualized. ISI
has been taking censuses since 2003, when Pradkin and
Joseph Bannister (of ISI) and Ramesh Govindan (of the USC
Viterbi School of Engineering, started collecting data. Their
hopes were to study the growth of the Internet, and their
group is still processing this data to look for trends.
"Internet census data is useful for several reasons",
Heidemannn says. "As the Internet use becomes
widespread, we are running out of Internet addresses-good
predictions by Geoff Huston suggest all addresses may be
allocated as soon as early 2010. The IETF (Internet
Engineering Task Force, the technical body that manages the
Internet) has anticipated this since the 1990s and designed a
new protocol, IPv6, to solve this problem, but deployment
has been slow. Our data can help illustrate the need to
It's hoped tha tthe census also can improve Internet
security. In fact, the Department of Homeland Security
"supported our work with the goal of improving network
security," said Heidemann, pointing to the work of ISI
researcher Jelena Mirkovic that is using
this census data to study how worms spread in the Internet.
Other researchers have plotted maps of where cyber-attacks
"There's also a sense of discovery in these maps",
Heidemannn says. "We've built a huge Internet and use it
every day. Like the far side of the moon, wouldn't you like
to know what it looks like?"
The census was undertaken by the Ant project, a research
group, according to its web site, " spanning USC/ISI, the
USC and Colorado State University Computer Science
Departments, the USC Electrical Engineering department,
and USC's Information Technology Services,. We're looking
at novel ways to examine network traffic."
More details about the census project and the full-scale map
are at http://www.isi.edu/ant/
ISI was one of the original nurseries of the Internet, playing
a key role in the development of the domain name system
and other features. ISI computer scientist Jon Postel
(1943-1998) directed the Internet Assigned Numbers
Authority for years.
The Department of Homeland Security and the National
Science Foundation supported the research.