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In February last year, Pakistan Telecom began routing the prefix 208.65.153.0/24 to a null site inside Pakistan. This routing message was then forwarded to the rest of the internet so that all traffic to 208.65.153.0/24 ended up in Pakistan. That turned out to be bad news for YouTube which owns the prefix and which was more or less unnaccessible during the hijacking of its prefix. The 28th February has since gained some notoriety for being the date of one of the most serious prefix hijacks in history.

The hijack lasted only a few hours but what of the possibility of a more serious event in which one country deliberately affects the traffic in another country?

Josh Karlin from the University of New Mexico and a few buddies point out that this is likely to become a bigger issue as countries impose laws on ISPs in their region. Deliberate attacks are not the only threat. Poorly drawn up or badly implemented legislation affecting ISPs could have a significant impact on other country’s traffic.

So karlin and his mates have begun the curiously tricky task of measuring how likely it is that one country’s traffic will be routed through another’s and how the routing can be changed to avoid this kind of conflict. And the work has thrown up some counterintuitive results.

It turns out that the countries with the most notorious censorship policies may not be the ones that pose the greatest risk.

For example, it’s well known that countries such as China, Iran, Pakistan, Saudi Arabia and Vietnam and South Korea all use a number of techniques to prevent their citizens gaining access to certain types of traffic. These techniques include blocking certain IP addresses, filtering traffic with certain URLs in the data packets and prefix hijacking, any of which could affect international traffic.

But according to Karlin and co, very little international traffic is routed through these countries so they pose a relatively small threat.

Less well known, they say, is that countries like Great Britain and Australia also censor traffic, albeit ona less pervasive scale. And that huge amounts of international traffic is routed through Britain.

The only country that is more influential than Britain by a measure invented by Karlin and co called the Country Centrality, is the US. The US, along with Sweden, allows wiretapping of international traffic without a warrant, not everybody’s cup of tea. But routing your internet traffic to avoid the US, or Britain for that matter, would be a tricky business.

Karlin and co say:

“Our results show that some countries known for their national policies, such as Iran and China, have relatively little effect on interdomain routing, while three countries (the United States, Great Britain, and Germany) are central to international reachability, and their policies thus have huge potential impact.”

Just how serious these issue might become remains to be seen. But it’s conceivable that these kinds of issues could trigger a major international dispute.

For that reason, policy makers in these countries need to be aware of the impact that their decisions can have. This looks to be an important step to giving them that knowledge.

Ref: arxiv.org/abs/0903.3218: Nation-State Routing: Censorship, Wiretapping, and BGP

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