Open Transport

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Open Transport was the name given by Apple Computer to their implementation of the Unix-originated System V STREAMS, replacing MacTCP.

Open Transport included STREAMS-based code for handling TCP/IP and serial devices based on Mentat Portable Streams.^[1] Additionally, Apple added an implementation of AppleTalk.

[edit] History

Open Transport was introduced in May 1995 with the Power Mac 9500. It was included with System 7.5.2, a release for the new PCI based Power Macs, but became available for older hardware later. MacTCP was not supported on PCI-based Macs but older systems could switch between MacTCP and Open Transport using Network Software Selector. Unlike MacTCP, Open Transport allowed users to save and switch between configuration sets.

Open Transport was generally successful, and offered enormous speed improvements over Apple's existing TCP/IP implementation, MacTCP. Developers also liked it because it was flexible in the way it allowed protocols to be "stacked" to apply filters and other such duties.

Open Transport was later abandoned during the move to Mac OS X, which uses the far more common Berkeley sockets networking system, although it is still present and usable in a limited form by older applications in the Classic environment. At the time this abandonment caused serious consternation among programmers, but this has generally disappeared since.