NATURAL networks have tree and branch structures with tributaries and arteries leading to or from concentrating organs or reservoirs. From vast rivers starting from a drop of rainwater falling from a leaf, to the vascular system of animals, or some nervous system, they all follow a similar fractal structure. Natural systems also have intermediate points of storage and activity, with streams and rivers punctuated by ponds and lakes.

Perhaps it is not surprising that most forms of human network adopt a similar form to Mother Nature. Even road systems start and finish in someone's drive; railways have inter-city tracks linked by lesser feeder systems; a letter penned in the living room is aggregated with millions of others for transport and delivery. Air traffic is the same, and so is the fax and telephone network, but there are some interesting exceptions. Canals built for standard-sized barges, and broadcast radio and TV, are two. We might argue that canals do not form a true network because there are too few of them, and certainly those that combine with mighty rivers tend toward the natural fractal state.

The biggest exception to this natural network mode is the future Internet. Today the Net is very tree-and-branch, very fractal. The principal reason is the use of the telephone network, and much of the associated thinking. Moreover, computer terminals still take much of their input from humans typing at less than 100 bits a second.

Two things are about to change all this: more mobility and more machines online. Once information sources become predominantly mobile, and machines generate more bits than people, networks have to take on a radically different form.

Probably the best analogy would be a society where no one had a home, but every individual had a car, travelled extensively every day, seldom stopping for food and rest, and slept in a different hotel (with a minimum of 1,000 beds) every night. But with only enough beds for a fraction of the populace, the network never sleeps. Imagine the road system necessary to support such a society, and you are close to seeing the future of the Net.

The overflow of rivers is accommodated by lakes, dams, the sea, and flooding, while our cars are similarly dealt with by traffic jams and car parks. In the bit world we have data storage, transmission, switching, router and terminal packet losses fulfilling the same function. But in the future this will be inadequate and wholly unsatisfactory.

As we wear and carry more technology, continue to be transported in machines, live and work in buildings with ever more technology, we will see traffic and service demands concentrated at different nodes daily and hourly. We thus have only three options: suffer an increasingly poor and sporadic service; cache data in large quantities; or provide a reasonably homogenous network. Of course, caching does not work for real-time services, and bandwidth provision is the only solution. Fortunately, we now have the technology and ability to provide thick Net pipes everywhere. These unnatural fibre and radio nets will transcend today's Internet to provide at least a gigabit per second to every fixed node.

Peter Cochrane holds the Collier Chair for the Public Understanding of Science & Technology at the University of Bristol. His home page is:
http://cochrane.org.uk