Editing Transport Layer Interface

{{use dmy dates|cs1-dates=ly|date=January 2021}}
In [[computer networking]], the '''Transport Layer Interface''' (TLI) was the networking [[Application Programming Interface|API]] provided by [[AT&T Corporation|AT&T]] [[UNIX System V]] Release 3 (SVR3) in 1987{{sfnp|Goodheart|Cox |1994|p=11}} and continued into Release 4 (SVR4).{{sfnp|Goodheart|Cox |1994|p=17}} TLI was the System V counterpart to the [[Berkeley Software Distribution|BSD]] [[Berkeley sockets|sockets]] programming interface, which was also provided in [[UNIX System V]] Release 4 (SVR4).{{sfnp|Goodheart|Cox |1994|p=17}} TLI was later standardized as '''XTI''', the '''[[X/Open Transport Interface]]'''.

==TLI and Sockets==
It was originally expected that the [[Open Systems Interconnection|OSI]] protocols would supersede TCP/IP, thus TLI is designed from an [[OSI model|OSI&nbsp;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, may have been preferred over the POSIX Sockets API<ref name="Xns">{{Cite book
|author=X/Open Group
|title=Networking Services (XNS) Issue 5.2
|edition=5.2
|date=January 2000
|publisher=The Open Group
|location=Berkshire, U.K.
|series=CAE Specification
}}</ref> with respect to existing standards.  However, it was clear at least since the early 1990s that the Berkeley Socket interface would ultimately prevail.<ref>{{cite web |author=Andrew L. Russell |date=30 July 2013 |title=OSI: The Internet That Wasn't |work=IEEE Spectrum |url=https://spectrum.ieee.org/osi-the-internet-that-wasnt |access-date=2021-01-10}}</ref> 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 (operating system)|Solaris]] and [[AIX]] (as well as the [[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.<ref name="Xns" /><ref>{{Cite book
|author=X/Open Group
|title=Networking Services (XNS) Issue 5
|edition=5th
|date=February 1997
|publisher=The Open Group
|location=Berkshire, U.K.
|series=CAE Specification
|isbn=1-85912-165-9
}}</ref>  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.

== See also ==
* [[X/Open Transport Interface]], formally standardized successor to TLI.
* [[X/Open Portability Guide]], the predecessor to [[POSIX]]
* [[Computer networking]], outlining the major networking protocols

==Notes==
{{Reflist|30em}}

==References==
*{{cite book
|first1=Berny
|last1=Goodheart
|first2=James |last2=Cox
|title=The magic garden explained: the internals of UNIX System V Release 4, an open-systems design
|year=1994
|location=Australia
|publisher=Prentice Hall
|isbn=0-13-098138-9
}}
* {{Cite book
|first=Branko
|last=Nuss
|title=RTFM!!! Issue 5.2
|volume=1
|edition=1.0
|date=January 2000
|publisher=Addison-Wesley
|location=Akron, OH
|series=CAE Specification
}}
*{{cite book
|first=George
|last=Pajari
|year=1992
|edition=2nd Printing
|orig-year=1991
|title=Writing UNIX Device Drivers
|location=Reading, MA
|publisher=Addison-Wesley
|isbn=0-201-52374-4
|url=https://archive.org/details/writingunixdevic00paja_0
}}
*{{Cite book
|author=Santa Cruz Operation
|publisher=The Santa Cruz Operation, Inc.
|location=Santa Cruz, CA
|title=System V Application Binary Interface — Intel386 Architecture Processor Supplement
|edition=4th
|year=1997
|orig-year=1995
}}
*{{Cite book
|author=Santa Cruz Operation
|publisher=The Santa Cruz Operation, Inc.
|location=Santa Cruz, CA
|title=System V Application Binary Interface
|edition=4.1th
|year=1997
|orig-year=1995
}}
* {{cite book
|last=Stevens
|first=W. Richard
|title=UNIX Network Programming
|year=1990
|publisher=Prentice-Hall
|location=Englewood Cliffs, N.J.
|isbn=0-13-949876-1
}}
*{{cite book
|first=W. Richard
|last=Stevens
|title=Advanced Programming in the UNIX Environment
|publisher=Addison-Wesley
|location=Reading, MA
|year=1993
|edition=1st Edition, 15th Printing
|isbn=0-201-56317-7
|url=https://archive.org/details/advancedprogramm00stev
}}
*{{cite book
|first=Rebecca
|last=Thomas
|author2=Lawrence R. Rogers |author3=Jean L. Yates
|publisher=Osborne McGraw-Hill
|location=Berkeley, CA
|title=Advanced Programmers Guide to UNIX System V
|year=1986
|isbn=0-07-881211-9
}}
*{{Cite book
|author=UNIX System Laboratories
|year=1995
|edition=4th
|title=System V Application Binary Interface
|publisher=UNIX System Laboratories
|location=Englewood Cliffs, N.J.
}}
*{{cite book
|author=Waite Group
|editor=Mitchel Waite
|year=1987
|edition=2nd Printing
|title=UNIX Papers
|location=Indianapolis, IN
|publisher=Howard W. Sams & Company
|isbn=0-672-22578-6
|url=https://archive.org/details/unixpapers00wait
}}
*{{Cite book
|first=Steve
|last=Zucker
|author2=Kari Karhi
|publisher=SunSoft
|location=Mountain View, CA
|title=System V Application Binary Interface—PowerPc Processor Supplement
|year=1995
|orig-year=1993
}}

== External links ==
* [http://www.opengroup.org/bookstore/catalog/c523.htm The Open Group's XTI standard]
* [http://gim.org.pl/uczelnia/PSI/7.XTI_TLI/ Example client-server application working on Solaris and Linux]

[[Category:Application programming interfaces]]