IBM Network Control Program
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The IBM Network Control Program, or NCP, was software that ran on a 37xx communications controller and managed communication with remote devices. NCP provided services comparable to the
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and
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functions in the
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of a
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.


Overview

The original
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Network Control Program ran on the 3705-I and supported access to older devices by application programs using Telecommunications Access Method (TCAM). With the advent of
Systems Network Architecture Systems Network Architecture (SNA) is IBM's proprietary computer network, networking architecture, created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes formats and protocols but, in its ...
(SNA), NCP was enhanced to connect cluster controllers (such as the
IBM 3270 The IBM 3270 is a family of Block-oriented terminal, block oriented display and printer computer terminals introduced by IBM in 1971 and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display ter ...
) to application programs using TCAM and later to application programs using Virtual Telecommunications Access Method (VTAM). Subsequent versions of NCP were released to run on the IBM 3704, IBM 3705-II, IBM 3725. IBM 3720, or
IBM 3745 The IBM 3745 is the latest and last of a 37xx family of communications controllers for the IBM mainframe environment. As of mid-2009 there were an estimated 7,000+ of the larger 3745 models still in active production status, down from 20,000 or m ...
Communications Controllers, all of which SNA defined as a SNA Physical Unit Type 4 (PU4). A PU4 usually had SDLC links to remote cluster controllers (PU1/PU2) or to other PU4s. Polling and addressing of the cluster controllers was performed by the NCP without mainframe intervention. In 2005 IBM introduced
Communications Controller for Linux Communications Controller for Linux (Communications Controller for Linux on System z or CCL) is an IBM software product announced in 2005 that runs under Linux on IBM Z and emulates an IBM 37xx communications controller. CCL runs unmodified IBM Net ...
(CCL), a software product that allows an unmodified NCP to run on the mainframe, eliminating the need for a separate communications controller in some cases. A ''local'' NCP connected to a
System/370 The IBM System/370 (S/370) is a range of IBM mainframe computers announced as the successors to the IBM System/360, System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migrati ...
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via singleHowever, if NCP was generated with Partitioned Emulation Program (PEP), then the Emulator Program (EP) has its own block of I/O addresses, normally on a different channel from that used by the NCP proper. The EP part of a PEP was often used to communicate with the Message Control Program (MCP) provided by TCAM running in the mainframe as the interface with application programs. address. A ''remote'' NCP had no direct connection to a mainframe but was connected to a local NCP via one or more high-speed SDLC links.


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Further reading

*{{cite web , author=W. S. Hobgood , title=The role of the Network Control Program in Systems Network Architecture , publisher=IBM Systems Journal , year=1976 , version=Vol 15, No 1 , url=http://www.research.ibm.com/journal/sj/151/ibmsj1501E.pdf , accessdate=2006-08-26 , url-status=bot: unknown , archiveurl=https://web.archive.org/web/20070316233256/http://www.research.ibm.com/journal/sj/151/ibmsj1501E.pdf , archivedate=2007-03-16 Network Control Program Network protocols Network Control Program