http://www.nytimes.com/2008/02/26/technology/26tube.html?_r=1&ref=business&oref=slogin
Although I was not personally aware of it at the time, apparently YouTube was made unavailable to most of the world this past Sunday for a period of about 2 hours because of an alleged accident made by the Pakistani state-operated Pakistan Telecommunication Authority (PTA). The two above links will direct you a New York Times article and blog respectively that have further information and insight into this strange happening. The paragraph that follows briefly summarizes the incident.
The Pakistani government recently decided to block its citizens from viewing YouTube, purportedly in response to a specific video on the site that was offensive to Muslims; it was by no means the first country to implement such a block. To cut domestic access, the PTA set up a dummy route for YouTube, which essentially sent the site’s traffic to a “black hole.” What reportedly went wrong was that it next announced this dummy route to its telecommunications partner, the Hong Kong based ISP PCCW, which mistakenly accepted and relayed that route to several dozen other major and minor ISP’s around the world. These ISP’s, now faced with competing routes, automatically accepted the Pakistani one over the original, functioning one because of the Border Gateway Protocol, which favors and selects longer routing addresses over shorter ones. YouTube was thus blocked for hundreds of millions of internet users worldwide until the website’s administrators caught on and alerted the ISP’s to the issues, which thankfully only took a few hours.
This story clearly connects to concepts in graph theory and the structure and function of information networks. While we might tend to think of the physical and virtual structures of the internet as a massive graphs with billions of nodes and edges, such that a popular site/node like YouTube would lie on millions of different paths and cycles and would thus be extremely difficult, if not impossible, to globally block in such an unintentional and uncoordinated way, clearly there are other factors to examine. The block is a good example of the shortcomings of graph theory, in that the structure of a network is not always capable of demonstrating that network’s functioning and behavior, which are in this case perhaps best understood in the context of internet protocol and the network of ISP’s; the former being responsible for the dummy route replacement, while the latter explains the widespread scale and ultimate severity of the block. Ironically, in this instance, the notion of optimal paths, combined with the interconnectedness and automatic processing of ISP’s seemed to prevent proper functioning.
Finally, this story also raises some serious question about internet security and vulnerability; if a country as relatively small and undeveloped as Pakistan could very easily accidentally disrupt YouTube’s traffic and block the site for users worldwide, then what sort of cyber-chaos and confusion could potentially be unleashed by a malevolent country or group? Furthermore, does the blame lie with Pakistan, the ISP’s, internet protocol, or something else entirely? Lastly, what can be done to prevent something like this or worse from happening again, and who is responsible for doing it?
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