The ease with which an entire country can be disconnected from the Internet depends almost entirely on the number of Internet entry and exit points it has, said Carlos Morales, vice president of global sales engineering and operations at Arbor Networks. It's easy to cut countries like Burma and Syria off the Internet because all they have is a single government-owned ISP with an international connection, he said.
Not only are such infrastructures easy to shut down, they are also much more susceptible to denial-of-service attacks and router-poisoning attacks, he said. "The Internet is all about IP routing reachability," he said. "People traveling on roads know how to get to their destination. On the Internet, at every point you need to be told where to go next." So if the routers that perform that task for a country are shut down, the country disappears from the Internet, Morales said.
The situation in Syria highlights the importance of having physical and logical diversity in the Internet infrastructure, Zmijewski added. Egypt, which suffered through a somewhat similar blackout two years ago, had multiple companies providing Internet services within the country. Even so, the government there was able to easily choke off the Internet because the providers were operating from a fairly limited set of facilities, he said.
"In Egypt's case, they just turned off the power to the facilities where the cables were coming in," Zmijewski said.
Achieving a similar result in a country like the U.S., with its countless Internet entry and exit points and numerous services, would be infinitely harder, even if such a thing were legally permissible, Renesys said. According to the company, countries like the U.S, Canada, Australia, the Netherlands and many in Europe and South America have more than three-dozen major ISPs connecting to the global Internet.
Each country has too many paths for Internet connectivity and too many independent providers to allow for large scale Internet shutdowns. While a government could conceivably impair connectivity by forcing large providers to shut down, there would still be too many paths in and out of the country that remain open, Renesys CTO James Cowie wrote today.