Network Control Program (DECnet)

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NCP (Network Control Program) is the program that manages DECnet in all of the DEC operating systems that support it.

Every operating system has got its own NCP variant, but most of the commands are identical.

Citation from "DECnet-VAX, Version 1 Software Product Description" (September 1978):

The Network Control Program (NCP) performs three primary functions: displaying statistics, controlling network components, and testing network components.
Using the DECnet-VAX NCP utility, an operator can display the status of DECnet activity at the local node. The user can choose to display statistics related to the local node, other DECnet-VAX nodes, and communication lines, including information on traffic and errors.
Using the DECnet-VAX NCP utility, the local operator can also perform many network control functions such as reconfiguring the local node’s network parameters, starting and stopping lines, activating the local node, and down-line loading DECnet-11S systems.
NCP allows the user to perform a series of tests that aid in isolating problems. NCP can be used to send and receive test messages over individual lines either between nodes or through other controlled loopback arrangements. The messages can then be compared.

NCP Versions

An early version of NCP (e.g. included in DECnet-VAX V1.3, June 1980) was missing some features and commands found in more recent versions:

  • No distinction between 'VOLATILE' and 'PERMANENT' settings resp. database - all settings were 'permanent'; only 'PURGE', and no 'CLEAR' commands
  • Command execution restricted to the 'LOCAL' node - i.e. no 'SET EXECUTOR' command to change to a 'REMOTE' node, and no 'TELL' command to execute single commands remotely
  • No 'LOGGING' command
  • No 'TRIGGER' command
  • No 'DUMP' command

Shortly after the release of DECnet-VAX V1.3, there was a major update in NCP functionality, and most of the features described missing above were introduced.

Later updates brought support for new protocols, network interfaces, and utilities.

NCP served DECnet Phases I to IV, but Phase V (DECnet-OSI) had its own new management program NCL.

DECnet Phases, supported DEC Operating Systems, and DECnet Product Names

Phase I (1975)

  • RSX-11M
  • RSX-11D

Phase II (1978)


  • SPD10.78.1 DECnet Phase II Products V1.0 (March 1978)
  • 10.78.02_7809_DECnet_Phase_II_Products (September 1978)
  • 10.78.05_8006_DECnet_Phase_II_Products (June 1980)
  • AA-AV51A-TK Introduction to DECnet Phase III (May 82)
  • AA-K179A-TK DECnet Digital Network Architecture General Description (October 1980)
  • AA-K181A-TK DECnet Digital Network Architecture Network Management Functional Specification (October 1980), pdf page 17pp !!!

  • RSX-11M: DECnet-11M / DECnet-RSX
  • RSX-11D: DECnet-11D
  • RSX-11S: DECnet-11S (Phase???)
  • IAS: DECnet-IAS
  • RSTS/E: DECnet/E
  • RT-11: DECnet-RT
  • TOPS-20: DECnet-20

Phase III (1980)

  • RSX-11M
  • RSX-11M-PLUS
  • IAS
  • RSTS/E
  • RT-11
  • TOPS-20

Phase IV (1982)

  • RSX-11M/M+
  • MS-DOS
  • TOPS-20
  • RSTS/E