Digital Data Communications Message Protocol (DDCMP) is a communications protocol

Communications protocol

A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...

 devised by Digital Equipment Corporation

Digital Equipment Corporation

Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

 in 1974 to allow communication over point-to-point network links for the company's DECnet

DECnet

DECnet is a suite of network protocols created by Digital Equipment Corporation, originally released in 1975 in order to connect two PDP-11 minicomputers. It evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s...

 Phase I network protocol. The protocol uses full or half duplex

Duplex

Duplex commonly means double or twofold.It may also refer to:* Duplex , a two-unit apartment building or condominium* Duplex, a common electrical receptacle with two NEMA type 5 plugs* Duplex locomotive, a type of steam locomotive...

 synchronous

Synchronization

Synchronization is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....

 and asynchronous

Asynchronous communication

In telecommunications, asynchronous communication is transmission of data without the use of an external clock signal, where data can be transmitted intermittently rather than in a steady stream. Any timing required to recover data from the communication symbols is encoded within the symbols...

links and allowed errors introduced in transmission to be detected and corrected. It was retained and extended for later versions of the DECnet protocol.