Open Transport

Open Transport was the name given by Apple Inc. to its implementation of the Unix-originated System V STREAMS networking stack. Based on code licensed from Mentat's Portable Streams product, Open Transport was built to provide the Mac OS with a modern TCP/IP implementation, replacing MacTCP. Apple also added its own implementation of AppleTalk to the stack to support legacy networks.

History

STREAMS

Prior to the release of Open Transport, the Macintosh OS used a variety of stand-alone INITs to provide networking functionality. The only one that was widely used throughout the OS was the AppleTalk system. Among the other protocol stacks supported, MacTCP was becoming increasingly important as the Internet boom started to gain momentum. MacTCP emulated the Berkeley sockets system, widely used among Unix-like operating systems.

MacTCP and the previous generation AppleTalk library were slow on PowerPC-based Macintoshes because they were written for previous generation 680x0-based Macintoshes and therefore ran under emulation on PowerPC-based machines. MacTCP was also lacking in features, however, and a major upgrade was clearly needed if Apple was to keep its hand in the Internet market.