I'm not an expert on the technical intricacies of how the Internet is controlled in China, but since we talked about those issues at a seminar (seminar group 2), here is a good article I read last year:
China’s Great Firewall is crude, slapdash, and surprisingly easy to breach. Here’s why it’s so effective anyway.
"China’s Internet seems slow. Partly this is because of congestion in China’s internal networks, which affects domestic and international transmissions alike. Partly it is because [...] And partly it is because of the delaying cycles imposed by China’s system that monitors what people are looking for on the Internet, especially when they’re looking overseas.
In reality, what the Olympic-era visitors will be discovering is not the absence of China’s electronic control but its new refinement—and a special Potemkin-style unfettered access that will be set up just for them, and just for the length of their stay. According to engineers I have spoken with at two tech organizations in China, the government bodies in charge of censoring the Internet have told them to get ready to unblock access from a list of specific Internet Protocol (IP) addresses—certain Internet cafés, access jacks in hotel rooms and conference centers where foreigners are expected to work or stay during the Olympic Games.