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into DNA, proteins, membrane molecules, and any other special ingredient it
needs. On the Internet, data packets reach a computer, where they can be
reassembled into the original e-mail, YouTube videos, Skype telephone calls,
and the like.

A bow-tie organization allows both the Internet and E. coli to run quickly
and efficiently. If E. coli (like all bacteria, indeed like all living
things) did not have a bow tie, it would have to use a different set of
enzymes to make each of the thousands of different molecules it needs from
each type of food. Rather than use such a huge, slow system, E. coli just
points all its metabolic pathways into the same bow-tie knot, making
everything from the same raw materials. Likewise, the Internetâ™s bow-tie
architecture means that it doesnâ™t have different ways to handle, say,
e-mail traffic and instant-message traffic. Everything passes through as the
same types of data packets.

The bow-tie architecture also makes both the Internet and E. coli robust. If
the type of incoming material changes rapidlyâ”say, a surge in video
traffic in the Internetâ™s case, or a new food source for the E.
coliâ”the system can process that material without having to retool its
entire metabolism to cope.

Another advantage of a bow tie is that it makes feedback control easy.
Information travels back from a receiving computer to the sender, which can
speed up or slow down its packets in response. E. coliâ™s metabolism is
loaded with analogous feedback loops. Normally E. coli can synthesize all the
amino acids it needs for making proteins. But if it can get a certain kind of
amino acid from the environment, that information shuts down its own
production line.

But as Doyle points out, improving robustness comes with a price. The bow-tie
structure opens the door to a vulnerability that could prove very hard to
fix. Because of the homogenization that occurs at the heart of the bow tie,
itâ™s difficult to identify and block harmful agents. In the case of the
Internet, it takes only a short piece of code to produce a digital virus that
can spread quickly to millions of computers and cause billions of dollars of
damage. In living organisms, real viruses hijack cells in much the same way.

Doyle thinks the similarity between E. coli and the Internet is no accident.
As networks get big and complicatedâ”either through the tinkering of
Internet engineers or through millions of years of evolutionâ”they must
follow certain rules to stay robust. âœThere is an inevitable
architecture,❠Doyle says.

Over dinner, Doyle muses on how to deal with these fundamental
vulnerabilities. He hasnâ™t found a way to improve biological reliability
(yet), but he does think he can help address the Internetâ™s limits.

The current packet-receipt feedback system (known as TCP) has worked
wonderfully for years to control the flow of Internet traffic, but it
wonâ™t be able to cope with the coming jam, when fridges will scan the
RFID chip on a milk carton and send an alert when the expiration date
arrives. âœWhether we like it or not, [Internet equipment giant] Cisco
will network everything. Soon our glasses will tell the kitchen theyâ™re
empty,❠Doyle says. That vast amount of traffic will make the Internet
catastrophically fragile. âœWe could wake up one morning and nothing
works.â

Many Internet experts are also worried, and theyâ™ve launched several
projects to save the network, including Steven Low, another Caltech
professor. Doyle is working with Low on his project, which is unusual in its
simplicity. Their plan to speed up the Internet is to simply do a better job
of paying attention to measurements of Internet traffic. Today computers
sense Internet congestion by noticing how many packets they lose. Thatâ™s
like trying to drive down a highway by just looking at whatâ™s 20 feet
ahead of you, constantly accelerating and then slamming on the brakes as soon
as you see something.

Doyle and his coworkers enable computers to use more information about
traffic flow, noting how long it takes for their packets to get to their
destination. The less traffic, the shorter the time, and with these traffic
reports on hand, their computers make much smarter decisions. The result is a
string of victories for high-speed Internet communication competitions. In
the last face-off in 2006, they managed to send 17 gigabitsâ”about a
full-length movieâ™s worthâ”each second across the Internet. Doyle
smiles as he describes their success, a flash of the athleteâ™s spirit in
his face. âœYouâ™re not just proving theorems,❠he says. âœIt
beats anything anyone else can do.â

Last year the Caltech team started operating a company, FastSoft, to market
their protocol. In March they started selling a box about the size of a DVD
player that you can plug into a server. In one test, a Fortune 500 company
was able to speed up its transmissions 30-fold. But Doyle stresses that a
real solution to the Internet crisis will require rethinking the control
process from the bottom up.

âœIf someone said, â˜Do a radical redesign,â™ Iâ™d say weâ™re
not ready yet,❠Doyle confesses. âœGoing to the moon was trivial
compared to dealing with this. Weâ™ve got a research path, but thereâ™s
some hard math to be done.â