Transport Layer Interface
Encyclopedia
In computer networking, the Transport Layer Interface (TLI) was the networking API
provided by AT&T
UNIX System V
Release 3 (SVR3) in 1987 and continued into Release 4 (SVR4). TLI was the System V counterpart to the BSD
sockets
programming interface, which was also provided in UNIX System V
Release 4 (SVR4). TLI was later standardized as XTI, the X/Open Transport Interface
.
protocols would supersede TCP/IP, thus TLI is designed from an OSI model
-oriented viewpoint, corresponding to the OSI transport layer
. Otherwise, TLI looks similar, API-wise, to sockets.
TLI and XTI were widely used and, up to UNIX 98, were preferred over the POSIX Sockets API. TLI and XTI are still supported in SVR4-derived operating systems and operating systems conforming to branded UNIX (UNIX 95, UNIX 98 and UNIX 03 Single UNIX Specifications) such as Solaris (as well as "classic" Mac OS
, in the form of Open Transport
). Under UNIX 95 (XPG4) and UNIX 98 (XPG5.2), XTI was the preferred and recommended supported API for new transport protocols. As a result of deliberations by the Austin Group with the goal of bringing flavors of UNIX that do not provide STREAMS
, such as BSD and Linux
, under the Single UNIX Specification, the UNIX 03 Single UNIX Specification both declares STREAMS
as optional, and declares POSIX Sockets as the preferred API for new transport protocols.
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...
provided by 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...
UNIX 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...
Release 3 (SVR3) in 1987 and continued into Release 4 (SVR4). TLI was the System V counterpart to the BSD
Berkeley Software Distribution
Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...
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....
programming interface, which was also provided in UNIX 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...
Release 4 (SVR4). TLI was later standardized as XTI, the X/Open Transport Interface
X/Open Transport Interface
The X/Open Transport Interface is an Open Group specification for network application programming present in UNIX System V operating systems. It provides OSI Transport Layer services with protocol independence...
.
TLI and Sockets
It was originally expected that the OSIOpen Systems Interconnection
Open Systems Interconnection is an effort to standardize networking that was started in 1977 by the International Organization for Standardization , along with the ITU-T.-History:...
protocols would supersede TCP/IP, thus TLI is designed from an OSI model
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
-oriented viewpoint, corresponding to the OSI transport layer
Transport layer
In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...
. Otherwise, TLI looks similar, API-wise, to sockets.
TLI and XTI were widely used and, up to UNIX 98, were preferred over the POSIX Sockets API. TLI and XTI are still supported in SVR4-derived operating systems and operating systems conforming to branded UNIX (UNIX 95, UNIX 98 and UNIX 03 Single UNIX Specifications) such as Solaris (as well as "classic" 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...
, in the form of Open Transport
Open Transport
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...
). Under UNIX 95 (XPG4) and UNIX 98 (XPG5.2), XTI was the preferred and recommended supported API for new transport protocols. As a result of deliberations by the Austin Group with the goal of bringing flavors of UNIX that do not provide 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...
, such as BSD and 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...
, under the Single UNIX Specification, the UNIX 03 Single UNIX Specification both declares 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...
as optional, and declares POSIX Sockets as the preferred API for new transport protocols.
See also
- X/Open Transport InterfaceX/Open Transport InterfaceThe X/Open Transport Interface is an Open Group specification for network application programming present in UNIX System V operating systems. It provides OSI Transport Layer services with protocol independence...
, formally standardized successor to TLI. - X/Open Portability Guide, the predecessor to POSIXPOSIXPOSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...
- Computer networking, outlining the major networking protocols