OSI layers .

[Mark Jones]

Hi , I was just wondering ...   I need to know what layers of the OSI model, the followin firewalls cover.   Can soemone please help me out ..   firewall-1 Cisco PIX Gauntlet Raptor   Thanks, Also If a firewall has proprietory OS, can it still complete proxying just as well as a firewall on say linux or Windows.   Thanks    Mark.