I was curious about the way Sentinel's "join-part" mechanism works.
Say nick A with host 1.1.1.1 Joins a channel and then nick B with the same host 1.1.1.1 Parts that same channel ... does it count as 1 join-part flood ?
I mean does it monitor nicks or ip addresses and how often they join part a channel ?
When it's detecting an actual flood, it doesn't care about the hosts of the flooders, just that the total number of joins and total number of parts that occured on the channel each match your sl_jflood setting. One thing to note is that for efficiency reasons, it only detects a flood on a join (e.g. if sl_jflood is 6:30, and there are 6 joins followed by 6 parts, it won't react until the next join).
Only the banning system cares about the host. For a host to be banned, it must be present in both the list of those that joined and of those that parted.