Back to the original topic: Here are the rates I’ve seen in the past week. Note that the yaxis scale is now requests/second.
There is a noticeable diurnal pattern. There may be a ~15% increase on 12-15/12-16. I don’t see a significant change such as Profile - MagicNTP - NTP Pool Project showed in his first graph.
There are several abusive clients, but these peak at ~hundreds of requests/second.
There were ~5 1N14 requests / second (see arduino NTP library and this)
I didn’t see anything unusual.