How to turn off the internet
We recently discussed the bow-tie structure of the web in class – the fact that most web pages are in one of three groups – those with many links to other pages but not many pages linking to them, those that are linked to by many pages but do not link to many pages themselves, and those that both have many links to them from other pages and link to many other pages. However, there is another structure that is important to consider when evaluating the accessibility of pages on the internet: that of the network connecting users to the internet itself.
This network can also be described by a directed graph, as shown in the article: each internet user must connect to an internet service provider (ISP), which (in most cases) must then connect to an Autonomous System controlled by a larger ISP, through which the internet can be accessed. Since all traffic must pass through an AS in order for a user to access the internet, the AS acts as a local bridge between a certain group of users and the rest of the internet. If the node representing the AS were to be removed, every user whose ISP directs its traffic through that AS would be unable to access any of the pages on the internet.
This is exactly what happened in January 2011, when the Egyptian government decided to cut off all access to the internet as a response to anti-government protests that were being organized over social media. Despite the millions of users and internet connections within the country, the government was able to shut off access to the internet all over Egypt within a few hours. This was possible due to the structure of data through Egypt’s ISP’s and AS’s. As shown in the graph, an overwhelming majority of Egypt’s traffic is directed through one of three Autonomous Systems. By forcing those AS’s to shut down, the government removed the local bridges that connected everyone in Egypt (almost everyone – the ISP that services the Egyptian stock market was not affected) to the internet. Therefore the importance of the local bridge in maintaining the overall structure of the network was clearly illustrated by the relative ease with which the Egyptian government was able to shut down the internet throughout all of Egypt.
http://qz.com/780675/how-do-internet-censorship-and-surveillance-actually-work/