From 1989–1990, three colleagues from AT&T Bell Laboratories, Dave Presotto, Janardan Sharma, and Kshitij Nigam, developed the second generation of firewalls, calling them circuit-level gateways.
V letech 1989-1990 tři kolegové z laboratoře AT&T Bell, Dave Presotto, Janardan Sharma a Kshitij Nigam vyvinuli druhou generaci firewallů a nazvali ji circuit-level brány.