Editing ESCON (section)

{{Short description|IBM data connection}}
{{Refimprove|date=December 2009}}
{{Use dmy dates|date=July 2020}}
[[Image:ESCON cable.JPG|thumb|280px|ESCON cable with connectors]]

'''ESCON''' (Enterprise Systems Connection) is a data connection created by [[IBM]], and is commonly used to connect their [[mainframe computer]]s to peripheral devices such as [[disk storage]], [[tape drive]]s and [[IBM 3270]] display controllers.  ESCON is an [[optical fiber]], [[half-duplex]], [[Serial communications|serial]] interface.  It originally operated at a rate of 10{{nbsp}}MB/s, which was later increased to 17{{nbsp}}MB/s.  The current maximum distance is 43 kilometers.{{Citation needed|date=December 2021}}

IBM introduced ESCON<ref>{{cite web
 |     title = IBM ENTERPRISE SYSTEMS CONNECTION ARCHITECTURE OVERVIEW
 |        id = 190-134
 |      date = September 5, 1990
 |       url = https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/4/897/ENUS190-134/index.html
 |      work = Announcement Letters
 | publisher = IBM
 }}
</ref> in September 1990 as part of its System/390 announcement.<ref>
{{cite book
 |date=September 5, 1990
 |title=System/390 processors, systems, functions designed to meet customer needs in the '90s
 |publisher=IBM
 |pages= 13–14
}}</ref><ref>{{cite web
 |     title = IBM SYSTEM/390 OVERVIEW: A NEW ERA BEGINS
 |        id = 190-123
 |      date = September 5, 1990
 |       url = https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/3/897/ENUS190-123/index.html
 |      work = Announcement Letters
 | publisher = IBM
 }}
</ref>  It replaced the older, slower (4.5{{nbsp}}MB/s), copper-based, parallel, [[IBM System/360]] [[Bus and Tag]] channels technology of 1960-1990 era mainframes.  Optical fiber is smaller in diameter and weight, and hence could save installation costs.  Space and labor could also be reduced when fewer physical links were required - due to ESCON's switching features.  ESCON is being supplanted by the substantially faster [[FICON]], which runs over [[Fibre Channel]].

ESCON allows the establishment and reconfiguration of channel connections dynamically, without having to take equipment off-line and manually move the cables.  ESCON supports channel connections using serial transmission over a pair of fibers.  The ESCON Director supports dynamic switching (which could be achieved prior to ESCON, but not with IBM-only products).  It also allows the distance between units to be extended up to 60&nbsp;km over a dedicated fiber. "Permanent virtual circuits" are supported through the switch.

ESCON switching has advantages over a collection of point-to-point links.  A peripheral previously capable of accessing a single mainframe can now be connected simultaneously to up to eight mainframes, providing peripheral sharing.

The ESCON interface specifications were adopted in 1996 by [[American National Standards Institute|ANSI]] X3T1 committee as the SBCON standard, which is now managed by [[Fibre Channel|X3T11]].<ref name="DeCusatisDeCusatis2006">{{cite book|author1=Casimer DeCusatis|author2=Carolyn J. Sher DeCusatis|title=Fiber optic essentials|url=https://books.google.com/books?id=c-B990MwuPkC&pg=PA154|year=2006|publisher=Academic Press|isbn=978-0-12-208431-7|pages=154–155}}</ref>