The Internet as Model Organism - Meeting Brief on
biological
aspects of the net
Lois Wingerson (editor in chief, HMS Beagle)
[...] Fractals and their theoretical descendants have
succeeded as
models for the behavior of the Internet -- where the
Poisson model
failed -- because the telephone system is not a good
analogy.
When you make a phone call, you occupy one dedicated
line until
you hang up; delivery is immediate and direct. The
Internet acts
more like a package delivery service. It picks up a
very large
number of packages and delivers them from "node" to
"node" until
they all reach their destinations. The packages can
travel over any
route, and can arrive out of order. Further, some go
through one
main post office, but others go through different
routing centers.
Also like the postal service, the Internet slows down
when demand
gets heavy (think about Christmas). When demand gets
too heavy,
the Internet simply throws excess parcels away.
In 1993, a paper by the session's chairman, Walter
Willinger of
AT&T, proposed that one could describe this kind of
traffic as a
fractal. "This was a bombshell," [Vern] Paxson said.
"It electrified
the community." But it was clearly the right idea, he
added. By
now there is "very strong empirical evidence" that the
behavior of
human populations as they log on to and use the Web
fits a fractal
pattern.
Another speaker at the session presented such evidence.
In Japan,
Misako Takayasu of Keio University has found a way to
measure
the passage of Internet packets traveling to and from
Tokyo.
Measuring from a packet's origin to the first node it
passes, she
said, its behavior is very "Poisson-like," but
somewhere between
the fourth and seventh junction it becomes ever more
fractal-like.
Takayasu's team has been trying to understand what
happens
when the junctions are so jammed that the system begins
to throw
packets away. The analogy she chose for Internet
traffic was
infectious disease. Her slide showed a rank of
schoolchildren
sitting at desks.
If you ignore the immune system, she said, Internet
traffic behaves
very like an infectious disease viewed from the vantage
point of the
organism. Infection and recovery rates are dependent on
interactions between neighbors and on the distance
between them;
so are the recovery rates of overcrowded Internet nodes
(called
routers). An infection can overburden and eradicate a
host; on the
other hand, a host can also recover. So can a router.
"This is one of the simplest trivial stochastic
models," Takayasu
said. "Many models having different evolution
properties converge
to the contact model." (In her abstract, she also used
the term
"evolve" to describe the future of the Internet.)
Going beyond modeling, Takayasu's team used the
Internet as an
experimental organism, sending packets to and from the
most
congested points, predicting what would happen at times
of high
congestion and measuring the actual behavior of the
packets.
Curiously, like the overworked executive who functions
best under
pressure, "the network can transport packets most
efficiently at the
critical point between congestion and the
non-congestion phase,"
she said (making yet another analogy, to phase
transition in
physical chemistry.) "If we can control to the critical
point," she
predicted, "we can make it an efficient system."
Will the Internet get so crowded it eventually breaks
down?
someone asked Paxson during the discussion. Everyone's
crystal
ball fails about two years out, he responded, but he
went on: "The
network has basic mechanisms within itself to avert a
collapse. . . .
The system is very elastic."
The Internet might never have survived at all, added
the final
speaker, Deborah Estrin of the University of Southern
California, if it
had been built as a rigid and stable steady-state
entity.
"Robustness," she concluded, "is the ability to
continue to operate
in the existence of continual component change."
Sound familiar? Mathematicians may not yet understand
the
Internet's behavior, but biologists can certainly
recognize some of
its qualities.
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3 of 5
Margaret Penfold (Saada, 3/22/99 5:32:10 PM)
I have on several occasions had recourse to the net to
answer such questions as "What is the incubation
periods for fox-cubs"
What are the migratory patterns for thrushes.
The net is a good place for keeping those photographs
of nature and other things within one's own back yard.
A digital camera is quite useful for recording
primroses, snails and frogs. Not so good for things
that move out of close focus. Then it is loading the
good camera and frequent trips to the chemist,
unfortunately beyond both my memory and my pocket.
4 of 5
Christy Sheffield Sanford (Christy1, 3/22/99 9:19:14 PM)
Thanks, Saada, what kind of digital camera do you have?
I have been looking but haven't made up my mind yet.
Beautiful line, by the way, the one with primroses,
snails and frogs. And have you put any of your nature
images up on the web? I would like to see them. Have
you considered adding them to your journal?
5 of 5
Christy Sheffield Sanford (Christy1, 3/27/99 9:43:28 PM)
I would like to create the effect on the web of writing
on water. If anyone has an idea of how this could be
done, let me know. Also, is it possible to have wide
angle cam shots, panormanic format? Say 10 in. long by
3 in. wide; this would be a landscape-like format?