For those who might need this: I have two servers in the .cn pool, but their monthly bandwidth quota is 4TB for each. To make sure I don’t exceed the quota I need to throttle the traffic somehow. I do this by blocking probes from the monitoring server’s netblocks. I don’t block the traffic originating from elsewhere. The scripts I use are available at http://miuku.net/ntp/limit-speed.html
Hopefully this helps someone.