Editing Systems Network Architecture (section)

==History==
[[File:Tapes and IBM 3745-170 (13889447458).jpg|thumb|IBM 3745-170]]
SNA was made public as part of IBM's "Advanced Function for Communications" announcement in September, 1974,<ref>{{cite web |last1=IBM Corporation |title=IBM Highlights, 1970-1984 |website=[[IBM]] |url=https://www.ibm.com/ibm/history/documents/pdf/1970-1984.pdf |access-date=Apr 19, 2019}}</ref> which included the implementation of the SNA/SDLC ([[Synchronous Data Link Control]]) protocols on new communications products:
*[[IBM 3767]] communication terminal (printer)
*[[IBM 3770]] [[data communication]] system
They were supported by [[IBM 3705 Communications Controller|IBM 3704/3705]] communication controllers and their [[IBM Network Control Program|Network Control Program]] (NCP), and by System/370 and their VTAM and other software such as CICS and IMS. This announcement was followed by another announcement in July, 1975, which introduced the [[IBM 3760]] data entry station, the [[IBM 3790]] communication system, and the new models of the [[IBM 3270]] display system.<ref name=newIBMin1975>{{cite report |quote=and the 3790/3760 data entry/data communications ... |title=IBM 3770 Family Batch Communications Terminal |publisher=Datapro |url=https://bitsavers.org/pdf/datapro/programmable_terminals/Datapro_C21_IBM.pdf}}</ref>

SNA was designed in the era when the computer industry had not fully adopted the concept of layered communication. Applications, databases, and communication functions were mingled into the same protocol or product, which made it difficult to maintain and manage.<ref name=NotProCon.DBxDatamation>{{cite news |magazine=[[Datamation]] |title=Bridge your legacy systems to the Web |url=https://www.datamation.com/applications/bridge-your-legacy-systems-to-the-web/}}</ref><ref>{{cite news |newspaper=[[Computerworld]] |title=Fujitsu Net Architecture |page=99 |date=November 15, 1976 |url=https://books.google.com/books?id=kuEuAAAAIBAJ&pg=PA99}}</ref> SNA was mainly designed by the IBM Systems Development Division laboratory in [[Research Triangle Park]], [[North Carolina]], USA,<ref name=TriParkSNA>{{citation |chapter=SNA: Recent advances and additional requirements |publisher=[[Springer Publishing]] |author=RJ Sundstrom |title=Networking in Open Systems |series=Lecture Notes in Computer Science |year=1987|volume=248 |pages=107–116 |isbn=3-540-17707-8 |doi=10.1007/BFb0026957 |chapter-url=https://link.springer.com/chapter/10.1007/BFb0026957}}</ref> helped by other laboratories that implemented SNA/SDLC. IBM later made the details public in its System Reference Library manuals and [[IBM Research#Publications|IBM Systems Journal]].

It is still used extensively in banks and other financial transaction networks, as well as in many government agencies. In 1999 there were an estimated 3,500 companies "with 11,000 SNA mainframes."<ref>{{cite news |newspaper=[[Informationweek]] |title=AT&T Outlines VPN Migration Plan |date=May 12, 1999 |url=https://www.informationweek.com/atandt-outlines-vpn-migration-plan/d/d-id/1007133?piddl_msgorder=asc |access-date=September 16, 2022}}</ref> One of the primary pieces of hardware, the [[IBM 3745|3745]]/3746 communications controller, has been withdrawn{{efn|However, the 3745 simulator [[Communications Controller for Linux]] (CCL) is still available.}} from the market by IBM. IBM continues to provide hardware maintenance service and microcode features to support users. A robust market of smaller companies continues to provide the 3745/3746, features, parts, and service. VTAM is also supported by IBM, as is the NCP required by the 3745/3746 controllers.

In 2008 an IBM publication said:
{{Blockquote|with the popularity and growth of TCP/IP, SNA is changing from being a true network architecture to being what could be termed an "application and application access architecture." In other words, there are many applications that still need to communicate in SNA, but the required SNA protocols are carried over the network by IP.<ref>{{cite book |title=Networking on z/OS |year=2010 |page=31 |publisher=IBM Corporation |url=https://www.ibm.com/docs/en/zosbasics/com.ibm.zos.znetwork/znetwork_book.pdf#page=41}}<br>{{cite web |title=Networking on z/OS (web document) |publisher=IBM Corporation |url=https://www.ibm.com/docs/en/zos-basic-skills?topic=review-systems-network-architecture-sna}}</ref>}}