Open Transport
Encyclopedia
Open Transport was the name given by Apple Inc. to their implementation of the Unix
-originated System V
STREAMS
. 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 their own implementation of AppleTalk
to the stack to support legacy networks.
s to provide networking functionality. The only one that was widely used throughout the OS was the AppleTalk
system. Among the other protocol stack
s 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 was both slow and lacking in features, however, and a major upgrade was clearly needed if Apple was to keep their hand in the Internet market.
Through the late 1980s several major efforts to re-combine the many Unix derivatives into a single system were underway, and the most significant among these was the AT&T
-led System V. System V included an entirely new networking stack, STREAMS
, replacing the existing Berkeley sockets system. STREAMS had a number of advantages over sockets, including the ability to support multiple networking stacks at the same time, the ability to plug in modules into the middle of existing stacks to provide simple mechanisms for filtering and similar duties, while offering a single application programming interface
to the user programs. At the time it appeared STREAMS would become the de-facto standard.
This change in the market led Apple to move to support STREAMS as well. It also presented two practical advantages to the company; STREAMS' multiprotocol support would allow them to support both TCP/IP and AppleTalk from a single interface, and a portable cross-platform version of STREAMS was available for purchase commercially, one that included a high-quality TCP implementation. Using STREAMS also appeared to offer a way to "one up" Microsoft
, who's own TCP/IP networking system, Winsock
, was based on the apparently soon-to-be-obsolete sockets.
. It was included with System 7.5.2
, a release for the new PCI
based Power Macs, and 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 a Control Panel
called Network Software Selector. Unlike MacTCP, Open Transport allowed users to save and switch between configuration sets.
Developer
opinion on Open Transport was divided. Some felt it offered enormous speed improvements over MacTCP. Some developers also liked it because it was flexible in the way it allowed protocols to be "stacked" to apply filters and other such duties. However, the system was also large and complex.The flexibility of the OpenTransport architecture, into which one could plug any desired protocol, was felt by some to be thoroughly overcomplicated. Additionally, most Unix code still used sockets, not STREAMS, and so MacTCP offered real advantages in terms of porting software to the Mac. Moreover, OpenTransport could only be utilized using the MPW
C/C++ compiler
.
The vaunted flexibility of the Open Transport architecture was undermined and ultimately made obsolete by the rapid rise of TCP/IP networking during the mid-90s. The same is true in the wider Unix market; System V was undermined by the rapid rise of free Unix-like systems, notably Linux
. As these systems grew in popularity, the vast majority of programmers ignored the closed STREAMS in favour of the BSD-licenced Sockets. Open Transport was abandoned during the move to Mac OS X
, which, like most Unix-like systems predating the System V efforts, was based entirely on sockets.
The Open Transport APIs are still present and usable in a limited form as a compatibility layer
for older applications, but are deprecated
in the Mac OS X 10.4 and later SDKs
.
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
-originated System V
UNIX System V
Unix System V, commonly abbreviated SysV , is one of the first commercial versions of the Unix operating system. It was originally developed by American Telephone & Telegraph and first released in 1983. Four major versions of System V were released, termed Releases 1, 2, 3 and 4...
STREAMS
STREAMS
In computer networking, STREAMS is the native framework in Unix System V for implementing character devices.STREAMS was designed as a modular architecture for implementing full-duplex I/O between kernel or user space processes and device drivers. Its most frequent uses have been in developing...
. Based on code licensed from Mentat's Portable Streams
Metat Portable Streams
Mentat Portable Streams was a platform independent implementation of the UNIX System V STREAMS networking protocol stack, normally sold with the Mentat TCP stack providing TCP/IP support. Portable Streams was used in a number of commercial products, including Apple Computer's Open Transport, AIX,...
product, Open Transport was built to provide the Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
with a modern TCP/IP implementation, replacing MacTCP
MacTCP
MacTCP was the standard TCP/IP implementation for the Macintosh operating system through version 7.5.1. It was the first application-independent implementation of a TCP stack for a non-Unix platform and predates Winsock by over 5 years...
. Apple also added their own implementation of AppleTalk
AppleTalk
AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking...
to the stack to support legacy networks.
STREAMS
Prior to the release of Open Transport, the Macintosh OS used a variety of stand-alone INITInit
init is a program for Unix-based computer operating systems that spawns all other processes. It runs as a daemon and typically has PID 1. The boot loader starts the kernel and the kernel starts init...
s to provide networking functionality. The only one that was widely used throughout the OS was the AppleTalk
AppleTalk
AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking...
system. Among the other protocol stack
Protocol stack
The protocol stack is an implementation of a computer networking protocol suite. The terms are often used interchangeably. Strictly speaking, the suite is the definition of the protocols, and the stack is the software implementation of them....
s supported, MacTCP
MacTCP
MacTCP was the standard TCP/IP implementation for the Macintosh operating system through version 7.5.1. It was the first application-independent implementation of a TCP stack for a non-Unix platform and predates Winsock by over 5 years...
was becoming increasingly important as the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
boom started to gain momentum. MacTCP emulated the Berkeley sockets
Berkeley sockets
The Berkeley sockets application programming interface comprises a library for developing applications in the C programming language that perform inter-process communication, most commonly for communications across a computer network....
system, widely used among Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating systems. MacTCP was both slow and lacking in features, however, and a major upgrade was clearly needed if Apple was to keep their hand in the Internet market.
Through the late 1980s several major efforts to re-combine the many Unix derivatives into a single system were underway, and the most significant among these was the AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
-led System V. System V included an entirely new networking stack, STREAMS
STREAMS
In computer networking, STREAMS is the native framework in Unix System V for implementing character devices.STREAMS was designed as a modular architecture for implementing full-duplex I/O between kernel or user space processes and device drivers. Its most frequent uses have been in developing...
, replacing the existing Berkeley sockets system. STREAMS had a number of advantages over sockets, including the ability to support multiple networking stacks at the same time, the ability to plug in modules into the middle of existing stacks to provide simple mechanisms for filtering and similar duties, while offering a single application programming interface
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
to the user programs. At the time it appeared STREAMS would become the de-facto standard.
This change in the market led Apple to move to support STREAMS as well. It also presented two practical advantages to the company; STREAMS' multiprotocol support would allow them to support both TCP/IP and AppleTalk from a single interface, and a portable cross-platform version of STREAMS was available for purchase commercially, one that included a high-quality TCP implementation. Using STREAMS also appeared to offer a way to "one up" Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
, who's own TCP/IP networking system, Winsock
Winsock
In computing, the Windows Sockets API , which was later shortened to Winsock, is a technical specification that defines how Windows network software should access network services, especially TCP/IP. It defines a standard interface between a Windows TCP/IP client application and the underlying...
, was based on the apparently soon-to-be-obsolete sockets.
OT
Open Transport was introduced in May 1995 with the Power Mac 9500Power Macintosh 9500
The Power Macintosh 9500 was a high-end Macintosh personal computer which was designed, manufactured and sold by Apple Computer from May 1995 until early 1997. It was powered by a PowerPC 604 processor, a second-generation PowerPC chip which was faster than the earlier PowerPC 601 chip...
. It was included with System 7.5.2
System 7
System 7 is the name of a Macintosh operating system introduced in 1991.System 7 may also refer to:* System 7 , a British dance/ambient band* System 7 , 1991 album* IBM System/7, a 1970s computer system...
, a release for the new PCI
Peripheral Component Interconnect
Conventional PCI is a computer bus for attaching hardware devices in a computer...
based Power Macs, and 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 a Control Panel
Control panel
Control panel may refer to:* Control panel , a flat, often vertical, area where control instrumentation is mounted.* Control panel , the tool in the operating system which allows most or all of the settings to be changed through a user interface** Control panel ** Control Panel ** Web hosting...
called Network Software Selector. Unlike MacTCP, Open Transport allowed users to save and switch between configuration sets.
Developer
Software developer
A software developer is a person concerned with facets of the software development process. Their work includes researching, designing, developing, and testing software. A software developer may take part in design, computer programming, or software project management...
opinion on Open Transport was divided. Some felt it offered enormous speed improvements over MacTCP. Some developers also liked it because it was flexible in the way it allowed protocols to be "stacked" to apply filters and other such duties. However, the system was also large and complex.The flexibility of the OpenTransport architecture, into which one could plug any desired protocol, was felt by some to be thoroughly overcomplicated. Additionally, most Unix code still used sockets, not STREAMS, and so MacTCP offered real advantages in terms of porting software to the Mac. Moreover, OpenTransport could only be utilized using the MPW
Macintosh Programmer's Workshop
Macintosh Programmer's Workshop or MPW, is a software development environment for the Classic Mac OS, written by Apple Computer. For Macintosh developers, it was one of the primary tools for building applications for System 7.x and Mac OS 8.x and 9.x. Initially, MPW was sold as a commercial product...
C/C++ compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
.
The vaunted flexibility of the Open Transport architecture was undermined and ultimately made obsolete by the rapid rise of TCP/IP networking during the mid-90s. The same is true in the wider Unix market; System V was undermined by the rapid rise of free Unix-like systems, notably Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
. As these systems grew in popularity, the vast majority of programmers ignored the closed STREAMS in favour of the BSD-licenced Sockets. Open Transport was abandoned during the move to Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, which, like most Unix-like systems predating the System V efforts, was based entirely on sockets.
The Open Transport APIs are still present and usable in a limited form as a compatibility layer
Compatibility layer
A compatibility layer is a term that refers to components that allow for non-native support of components.In software engineering, a compatibility layer allows binaries for a legacy or foreign system to run on a host system. This translates system calls for the foreign system into native system...
for older applications, but are deprecated
Deprecation
In the process of authoring computer software, its standards or documentation, deprecation is a status applied to software features to indicate that they should be avoided, typically because they have been superseded...
in the Mac OS X 10.4 and later SDKs
Software development kit
A software development kit is typically a set of software development tools that allows for the creation of applications for a certain software package, software framework, hardware platform, computer system, video game console, operating system, or similar platform.It may be something as simple...
.