IBM Network Control Program
Encyclopedia
The original IBM
Network Control Program (NCP) ran on the 3705 and supported access to older devices by application programs using Virtual Telecommunications Access Method (VTAM). A subsequent version also supported access to SNA networks, initially only by application programs using Virtual Telecommunications Access Method (VTAM) and later by application programs using Telecommunications Access Method (TCAM)
, and was the basis for the subsequent versions that ran on an IBM 3704, 3705, IBM 3725. IBM 3720, or 3745
. It caused the machine to become an IBM Systems Network Architecture (SNA) Physical Unit Type 4 (PU4). A PU4 usually had SDLC
links to remote cluster controllers (PU1/PU2) and optional SDLC links to other PU4s. Polling and addressing of the cluster controllers was performed by the NCP without mainframe intervention.
A local NCP connected to a System/370
channel via singleHowever, if NCP was generated with Partitioned Emulator 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. address. A remote NCP had no direct connection to a mainframe. Instead a connection was made through a local NCP via SNA packet switching. NCP provided the link control
and Network layer
functions of a Wide area network
.
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
Network Control Program (NCP) ran on the 3705 and supported access to older devices by application programs using Virtual Telecommunications Access Method (VTAM). A subsequent version also supported access to SNA networks, initially only by application programs using Virtual Telecommunications Access Method (VTAM) and later by application programs using Telecommunications Access Method (TCAM)
Telecommunications Access Method
Telecommunications Access Method is an access method, in IBM's OS/360 and successors computer operating systems on IBM System/360 and later, that provides access to terminals units within a teleprocessing network....
, and was the basis for the subsequent versions that ran on an IBM 3704, 3705, IBM 3725. IBM 3720, or 3745
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 more in 2007...
. It caused the machine to become an IBM Systems Network Architecture (SNA) Physical Unit Type 4 (PU4). A PU4 usually had SDLC
Synchronous Data Link Control
Synchronous Data Link Control is a computer communications protocol. It is the layer 2 protocol for IBM's Systems Network Architecture . SDLC supports multipoint links as well as error correction. It also runs under the assumption that an SNA header is present after the SDLC header...
links to remote cluster controllers (PU1/PU2) and optional SDLC links to other PU4s. Polling and addressing of the cluster controllers was performed by the NCP without mainframe intervention.
A local NCP connected to a System/370
System/370
The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the...
channel via singleHowever, if NCP was generated with Partitioned Emulator 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. address. A remote NCP had no direct connection to a mainframe. Instead a connection was made through a local NCP via SNA packet switching. NCP provided the link control
Data Link Control
In the OSI networking model, Data Link Control is the service provided by the data link layer. Network interface cards have a DLC address that identifies each card; for instance, Ethernet and other types of cards have a 48-bit MAC address built into the cards' firmware when they are...
and Network layer
Network layer
The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...
functions of a Wide area network
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...
.