Since this is Beijing, we're behind the Great Firewall of China, also called The Golden Shield. It works, as far as I've read, on three layers:
- A rudimentary "DNS block" and/or redirect.
- If you access the IP-address directly, it sends a TCP RST effectively tearing down your connection. (You browser responds with a "Connection reset")
- Content filtering of HTTP-traffic. Especially targeted at news-articles containing certain sensitive information. If a one or more pre-defined keywords appear in the page, the connection is blocked.
A couple of DNS lookups of blocked sites from behind the firewall:
$ cat /etc/resolv.conf
$ dig +short www.facebook.com
$ dig +short www.youtube.com
$ dig +short www.blogspot.com
But IETF's NOC have taken over the hotel network (both wired and wireless) and are currently bypassing the firewall. In cooperation with Tsinghua University, two 1Gbps links connect us to the CERNET (with backup to CSTNet).
A couple of test network has also been deployed. Including a IPv6-only network and a IPv6 network using NAT64.