Thanks both for your explanation, I did not saw the auth stats in cachemgr !
Looks like I ran too many, I have two squids with 1k simultaneous connexions on each, I set up 250 ntlm negotiate + 250 ntlm basic, it's far too much according to stats. 80 negotiate and 10 basic are sufficient :) I'm going to change this (and add kerberos).
