Net software uses genetic algorithms
By Duncan Graham-Rowe
VIRUSES are common on the Internet, but now it's the turn of bacteria, says
British Telecom. But rather than being a menace, the organisms BT has in
mind have been designed to help make the Net faster. The idea is to mimic
bacterial sex to "evolve" a more efficient network.
Ian Marshall at BT's research centre near Martlesham, Suffolk, believes that
the volume of Internet traffic is growing at an unsustainable rate. "It's
important that the network is able to adapt continuously," he says. BT's
solution is to let it manage itself.
Rather than having software oversee the entire network, Marshall and his
colleague Chris Roadknight designed the junctions of a network so that each
could be run by a piece of autonomous software. Like bacteria, they had no
central knowledge or overall control, yet Marshall says they were able to
run the network very efficiently.
Information sent over the Internet is broken up into discrete packets which
are stored in a "buffer" memory before being forwarded to the next leg of
their journey. Ideally, buffers are long. But the more information the
packets hold, the slower they move. "If a packet arrives at the buffer and
it is full, then it tends to get thrown away," says Marshall. This means
some information will be lost.
What is needed is the ability for buffers to know what kind of information
they are passing and adapt their length according to the need. To do this
using traditional techniques will become impossible as the Internet grows.
So BT turned to nature in the form of "genetic algorithms". These are
biologically inspired programs commonly used to help design--or
evolve--things that people find difficult.
GAs mimic natural selection by treating strings of data like genetic
material. These strings can be combined and mutated to produce offspring
whose fitness is then evaluated. The best are "bred" to produce more
offspring. This is repeated until the best design has evolved. The problem
BT found was that GAs are too slow for real-time applications, since they
require the evaluation to take place over many generations. So Marshall and
his colleagues proposed a different biologically inspired solution.
Bacteria don't have sex in the traditional sense, they reproduce using a
technique known as plasmid migration. "They wander around and bump into each
other and say 'hi, do you want some of my genetic material'," explains Inman
Harvey, an artificial intelligence researcher at the University of Sussex.
By exchanging plasmids (rings of genetic information) through their cell
membranes with neighbouring cells, successful genes can pass quickly through
a colony and allow it to adapt rapidly to its environment. Random mutations
produce new genes, with successful genes flourishing and ineffective ones
quickly dying off. In a network these successful genes will enable the
buffers to be optimised to carry packets of information as efficiently as
possible. According to Harvey, the technique could open up many
"With evolution, traditionally you only reap the benefits after many
generations, whereas here you have the three aspects of evolution--heredity,
variety and selection--but without anyone having to die," he adds.
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