Risk of internet collapse rising

The 11 September attack knocked out net hubs

Simulated attacks on key internet hubs have shown how vulnerable the worldwide network is to disruption by disaster or terrorist action.

If an attack or disaster destroyed the major nodes of the internet, the network itself could begin to unravel, warn the scientists who carried out the simulations.

The virtual attacks showed that the net would keep going in major cities, but outlying areas and smaller towns would gradually be cut off.

The researchers warn that the net has become more vulnerable as it has become more commercialised and key net cables are concentrated in the hands of fewer organisations.

Cutting the ties

The simulations were carried out by a trio of scientists from Ohio State University led by Tony Grubesic, Assistant Professor of Geography at the University of Cincinnati.

Dr Grubesic compared the net to US air traffic system.

"If weather stops or delays traffic in a major airport hub, like Chicago's O'Hare, air passengers throughout the country may feel the effects," said Dr Grubesic, "even if they are not travelling to Chicago."

If you destroyed a major internet hub, you would also destroy all the links that are connected to it

Morton O'Kelly, Ohio State University

In its early days the net was as decentralised as possible with multiple links between many of the nodes forming it. If one node disappeared, traffic could easily flow to other links and route traffic to all parts.

However, said the researchers, the increasing commercialisation of the net has seen the emergence of large hubs that act as key distribution points for some parts of the web.

As a result, the net has become much more vulnerable to attack.

"If you destroyed a major internet hub, you would also destroy all the links that are connected to it," said Morton O'Kelly, Professor of Geography at Ohio State University.

"It would have ripple effects throughout the internet"

Small worlds

US cities such as Los Angeles, New York, Atlanta, Dallas, Chicago and Washington DC are large net hubs and have several connections to the web.

An attack on one hub could have ripple effects

As a result any attack would bump up traffic levels on these links, but the larger cities would probably maintain net services.

By contrast, warn the researchers, smaller cities that rely on the large hubs to keep them connected could see their links severed by an attack on their routing centre.

The researchers said the attack on the World Trade Centre revealed how disruption could spread.

A major net hub was destroyed during the attack and severed links between New York City and three New York counties.

"The ability for networks to re-route, re-connect and have redundancy is clearly important for the survival of the internet in the face of disasters," said Dr Grubesic.

The researchers' work will appear in the February 2003 edition of Telematics and Informatics.