PIX was originally conceived in early 1994 by John Mayes of Redwood City, California and designed and coded by Brantley Coile of Athens, Georgia. The PIX name is derived from its creators' aim of creating the functional equivalent of an IP PBX to solve the then-emerging registered IP address shortage. At a time when NAT was just being investigated as a viable approach, they wanted to conceal a block or blocks of IP addresses behind a single or multiple registered IP addresses, much as PBXs do for internal phone extensions. When they began, RFC 1597 and RFC 1631 were being discussed, but the now-familiar RFC 1918 had not yet been submitted.