we further divide one of those seconds into 100 ten-millisecond segments, we will again see the jumpy
variation over those 100 segments. This self-similar behavior is like the fractals on a Mandelbrot set [7]
— when we zoom in on part of the curve, we eventually see a repetition of the curve.
In contrast to voice traffic that smooths out over larger time scales, the fractal nature of Internet traffic
means that you see burstiness at all time scales (10-msecs, seconds or minutes). With smoothed-out traffic,
an engineer knows how much capacity to provide to comfortably accommodate that traffic. With bursty
traffic, however, a wide and expensive margin of error must be provided; otherwise, a burst of traffic can
cause messages to be lost, which is perceived by users as delays.
Traffic self-similarity thus poses a challenge that has stimulated much research into data traffic modeling
and control.
2.7 Playing games with Internet traffic control and pricing
Some research has shown that traffic self-similarity may be partly caused by TCP [8], the principal Internet
software that regulates traffic flow. When TCP detects network congestion, it slows down the rate at which
a user can send data packets into the Internet. This is one reason the Internet has managed to cope with the
exponential growth in Web traffic over the last decade.
Nonetheless, TCP is imperfect, and its interaction with queueing delays, packet losses, etc., can some-
times cause undesirable behavior. Internet engineers therefore continue to tweak it. Also, there is now an
inexorable growth in file sharing traffic, generated by users of peer-to-peer systems (Napster, Gnutella,
KaZaA, etc.). One download of a movie can take hours, so there is also a temptation for expert users to
hack TCP and thus get a larger share of bandwidth for their traffic.
Neither tweaking nor hacking is guaranteed to have the desired effect, since a user’s TCP connection
could be interacting with thousands of other connections, each exercising some form of control. We can
thus view the Internet as a huge game in which players try to capture bandwidth. Indeed, researchers are
using game theory to study the appropriate TCP control mechanism for ensuring that the Internet remains
efficient and stable, despite selfish user behavior.
There is in fact another game going on, with less players but real money. The Internet is divided into
smaller networks, each controlled by an ISP (Internet Service Provider). Your traffic to an European des-
tination, say, is passed from ISP to ISP along the way. When an ISP