After a widespread blackout hit the United States and Canada, the so-called network domino effect attracted high public attention.

Network domino means that each node connected to a network shows a reaction that is triggered by something that went before. For example, most websites on the Internet are connected to a few core hubs. If one of the hubs broke down, sub websites geared with the hub would fail. Then another similar hub would collapse like a domino and in the end, the entire network would fail.

Modern physicists have paid attention to the effect of network dominos. Especially, scientists who have studied complex systems have warned that a network domino effect, if it occurs, will bring chaos to a society that is well connected through the Internet.

The cause of the blackout in the United States and Canada was not traced down quickly. But it apparently shows a typical network domino effect. The electricity network, tightly connected through the grid, got out of order at one point and then the glitch triggered other points to breakdown in succession. Finally it led to a blackout over an enormous area.

There was a similar case in Korea involving the Internet last January. The domain name server at the Hyehwa telephone office, an international port by which domain name servers connect local Internet service users to foreign websites, was overloaded by a huge amount of data and then other linked hubs broke down like dominos.

To prevent a network domino effect, we must build alternative hubs by diversifying servers. And it is important to establish a warning system to forestall any network failure.

The Internet and a combination of technology and functions using the Internet are characteristic of information transmission and communications in modern society. Because it is open to everyone, the Internet is a democratic structure. But numerous subordinate sites depend on a few hubs to operate on the Internet. So some critics say that Internet structure is a typical complex system of the rich get richer and the poor get poorer.

If only a few hubs monopolize core functions, network dominos can occur in politics and economics as well. Unless there are alternate hubs and warning systems, and if we are too dependent on the core hubs, we can be victims.