Does anyone have any stats on this?
I'm mainly asking from a private network perspective (assuming that they are affected by the firewall as well). That is, all of my apps that are in use in China are on our internal network.
I got to thinking about this after reading Mr Denny's recent answer on SQL replication. Now I'm wondering how much of a hit my app is taking in China because of the firewall.
When I was working on it, we calculated round trip at 550ms, with about 250ms of the time being native network lag time, about about 300-350ms of time being spent on the firewall.
This was over a T1 with no traffic on it (it was dedicated to SQL Replication traffic).
Bruce Schneier commented on an article about how the firewall works and how to circumvent it. Warranted, the article is from 2006, so things might have changed, but it's a worthwhile read nonetheless.
Besides the closed TCP connections, I'm not aware of any other practices that the Chinese use with their firewall, so connections shouldn't incur too much more of a penalty. The added latency of connections to China are more likely due too the distance traveled than the firewall.