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
data link layer
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer p ...
and
Network Layer
In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers.
Functions
The network layer provides the means of transfe ...
functions in the
OSI model
The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...
of a
Wide area network
A wide area network (WAN) is a telecommunications network that extends over a large geographic area. Wide area networks are often established with leased telecommunication circuits.
Businesses, as well as schools and government entities, us ...
.
Overview
The original
IBM 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 networking architecture, created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes formats and protocols but, in itself, is not a pi ...
(SNA), NCP was enhanced to connect cluster controllers (such as the
IBM 3270
The IBM 3270 is a family of 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 terminal. Due to the text ...
) 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 Ne ...
(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 model range of IBM mainframe computers announced on June 30, 1970, as the successors to the System/360 family. The series mostly maintains backward compatibility with the S/360, allowing an easy migration path f ...
channel
Channel, channels, channeling, etc., may refer to:
Geography
* Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water.
Australia
* Channel Country, region of outback Austral ...
via single
[However, 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.
Notes
References
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