Open Transport is modem networking and communications system software for the MAC OS. It is based on industry standards and brings a new level of networking connectivity, control, and compatibility to MAC OS computers, while preserving built-in support for easy-to-use networking. Open Transport is supported on system software versions 7.1, 7.1.1, 7.1.2, 7.5.3, 7.5.5 or later. System software version7.5.3 or later is recommended. No other system software versions are supported.
Apple
www.apple.com