Есть связка squid c delay pools и dansguardian. Настройки delay pools:
delay_pools 2
delay_class 1 2
delay_class 2 2
delay_access 1 allow kabinet19
delay_access 1 allow kabinet21
delay_access 1 allow others
delay_access 1 deny admins
delay_access 1 allow files
delay_access 1 deny all
delay_access 2 allow admins
delay_access 2 deny all
delay_parameters 1 -1/-1 2000/20000
delay_parameters 2 -1/-1 -1/-1