DECnet is a suite of

network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...

s created by

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president un ...

. Originally released in 1975 in order to connect two PDP-11

minicomputers A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ...

, it evolved into one of the first

peer-to-peer Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network. They are said to form a peer-to-peer ...

network architectures, thus transforming DEC into a networking powerhouse in the 1980s. Initially built with three layers, it later (1982) evolved into a seven-layer OSI-compliant networking protocol. DECnet was built right into the DEC flagship operating system OpenVMS since its inception. Later Digital ported it to Ultrix, as well as

Apple Macintosh The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc., Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and ...

and IBM PC running variants of

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

and Microsoft Windows under the name DEC Pathworks, allowing these systems to connect to DECnet networks of

VAX VAX (an acronym for Virtual Address eXtension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The V ...

machines as terminal nodes. While the DECnet protocols were designed entirely by Digital Equipment Corporation, DECnet Phase II (and later) were open standards with published specifications, and several implementations were developed outside DEC, including ones for FreeBSD and

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...

. DECnet code in the Linux kernel was marked as orphaned on February 18, 2010.

Evolution

DECnet refers to a specific set of hardware and software networking products which implement the DIGITAL Network Architecture (DNA). The DIGITAL Network Architecture has a set of documents which define the network architecture in general, state the specifications for each layer of the architecture, and describe the

protocols Protocol may refer to: Sociology and politics * Protocol (politics), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technology ...

which operate within each layer. Although network protocol analyzer tools tend to categorize all protocols from DIGITAL as "DECnet", strictly speaking, non-routed DIGITAL protocols such as

LAT Lat or LAT may refer to: Places * Lat, Fuman, village in Gilan Province, Iran * Lat, Rasht, village in Gilan Province, Iran * Lat, Mazandaran, village in Iran * Lat-e Disar, village in Mazandaran Province, Iran * Lat, Qazvin, village in I ...

, SCS, AMDS, LAST/LAD are not DECnet protocols and are not part of the DIGITAL Network Architecture. To trace the evolution of DECnet is to trace the development of DNA. The beginnings of DNA were in the early 1970s. DIGITAL published its first DNA specification at about the same time that IBM announced its

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). Since that time, development of DNA has evolved through the following phases:

1970-1980

Phase I (1974) Support limited to two PDP-11s running the

RSX-11 RSX-11 is a discontinued family of multi-user real-time operating systems for PDP-11 computers created by Digital Equipment Corporation. In widespread use through the late 1970s and early 1980s, RSX-11 was influential in the development of later ...

operating system only, with communication over point-to-point (

DDCMP Digital Data Communications Message Protocol (DDCMP) is a byte-oriented communications protocol devised by Digital Equipment Corporation in 1974 to allow communication over point-to-point network links for the company's DECnet Phase I network pr ...

) links between nodes. Phase II (1975) Support for networks of up to 32 nodes with multiple, different implementations which could inter-operate with each other. Implementations expanded to include RSTS, TOPS-10 and

TOPS-20 The TOPS-20 operating system by Digital Equipment Corporation (DEC) is a proprietary OS used on some of DEC's 36-bit mainframe computers. The Hardware Reference Manual was described as for "DECsystem-10/DECSYSTEM-20 Processor" (meaning the DEC PDP- ...

with communications between processors still limited to point-to-point links only. Introduction of downline loading (MOP), and file transfer using File Access Listener (FAL), remote file access using Data Access Protocol (DAP), task-to-task programming interfaces and network management features. Phase III (1980). Support for networks of up to 255 nodes over point-to point and multi-drop links. Introduction of adaptive routing capability, record access, a network management architecture, and gateways to other types of networks including IBM's SNA and CCITT Recommendation X.25.

1981-1986

Phase IV and Phase IV+ (1982). Phase IV was released initially to

and VMS systems, later

, TOPS-10, ULTRIX,

VAXELN VAXELN (typically pronounced "VAX-elan") is a discontinued real-time operating system for the VAX family of computers produced by the Digital Equipment Corporation (DEC) of Maynard, Massachusetts. As with RSX-11 and VMS, Dave Cutler was the ...

, and

RSTS/E RSTS () is a multi-user time-sharing operating system developed by Digital Equipment Corporation (DEC, now part of Hewlett-Packard) for the PDP-11 series of 16-bit minicomputers. The first version of RSTS (RSTS-11, Version 1) was implemented in 1 ...

gained support. Support for networks of up to 64,449 nodes (63 areas of 1023 nodes), datalink capabilities expanded beyond DDCMP to include

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...

support as the datalink of choice, expanded adaptive routing capability to include hierarchical routing (areas, level 1 and level 2 routers),

VMScluster A VMScluster, originally known as a VAXcluster, is a computer cluster involving a group of computers running the OpenVMS operating system. Whereas tightly coupled multiprocessor systems run a single copy of the operating system, a VMScluster is l ...

support (cluster alias) and host services (CTERM). CTERM allowed a user on one computer to log into another computer remotely, performing the same function that

Telnet Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet contr ...

does in the

TCP/IP The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...

protocol stack. Digital also released a product called the PATHWORKS client, and more commonly known as the PATHWORKS 32 client, that implemented much of DECnet Phase IV for DOS, and 16 and 32 bit Microsoft Windows platforms (all the way through to Windows Server 2003). Phase IV implemented an 8 layer architecture similar to the OSI (7 layer) model especially at the lower levels. Since the OSI standards were not yet fully developed at the time, many of the Phase IV protocols remained proprietary. The Ethernet implementation was unusual in that the software changed the physical address of the Ethernet interface on the network to AA-00-04-00-xx-yy where xx-yy reflected the DECnet

network address A network address is an identifier for a node or host on a telecommunications network. Network addresses are designed to be unique identifiers across the network, although some networks allow for local, private addresses, or locally administer ...

of the host. This allowed ARP-less LAN operation because the LAN address could be deduced from the DECnet address. This precluded connecting two NICs from the same DECnet node onto the same LAN segment, however. The initial implementations released were for VAX/VMS and RSX-11, later this expanded to virtually every

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

DIGITAL ever shipped with the notable exception of

RT-11 RT-11 (Real-time 11) is a discontinued small, low-end, single-user real-time operating system for the full line of Digital Equipment Corporation PDP-11 16-bit computers. RT-11 was first implemented in 1970. It was widely used for real-time computin ...

. DECnet stacks are found on Linux, SunOS and other platforms, and Cisco and other network vendors offer products that can cooperate with and operate within DECnet networks. Full DECnet Phase IV specifications are available. At the same time that DECnet Phase IV was released, the company also released a proprietary protocol called

for serial terminal access via

Terminal server A terminal server connects devices with a serial port to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication ...

s. LAT shared the OSI physical and datalink layers with DECnet and LAT terminal servers used MOP for the server image download and related bootstrap processing. Enhancements made to DECnet Phase IV eventually became known as DECnet Phase IV+, although systems running this protocol remained completely interoperable with DECnet Phase IV systems.

1987 & beyond

Phase V and Phase V+ (1987). Support for very large (architecturally unlimited) networks, a new network management model, local or distributed name service, improved performance over Phase IV. Move from a proprietary network to an

Open Systems Interconnection 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 ...

(OSI) by integration of ISO standards to provide multi-vendor connectivity and compatibility with DNA Phase IV, the last two features resulted in a hybrid network architecture (DNA and OSI) with separate "towers" sharing an integrated transport layer. Transparent transport level links to

were added via the

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

RFC 1006 (OSI over IP) and RFC 1859 (NSP over IP) standards ''(see diagram)''. It was later renamed DECnet/OSI to emphasize its OSI interconnectibility, and subsequently DECnet-Plus as TCP/IP protocols were incorporated.

Notable installations

DEC Easynet

DEC's internal corporate network was a DECnet network called Easynet, which had evolved from DEC's Engineering Net (E-NET). It included over 2,000 nodes as of 1984,Erik E. Fair (January 5, 1984)
Re: The Plethora of Networks
''Usenet fa.human-nets''. Retrieved August 19, 2018. 15,000 nodes (in 39 countries) as of 1987,Network World (September 7, 1987), p.4
DECworld network links hotels, ocean liners
Retrieved August 19, 2018. and 54,000 nodes as of 1990.Network World (August 6, 1990), p.1
DEC shares early lessons on DECnet V
Retrieved August 19, 2018.

The DECnet Internet

DECnet was used at various scientific research centers which linked their networks to form an international network called the DECnet Internet. This included the U.S. Space Physics Analysis Network (US-SPAN), the European Space Physics Analysis Network (E-SPAN), and other research and education networks.L. Stuart Vance (1990)
The User's Directory of Computer Networks, The DECnet Internet
Retrieved August 19, 2018.L. Stuart Vance (1990)
The User's Directory of Computer Networks, The DECnet Internet (Publisher Summary)
Retrieved August 19, 2018. The network consisted of over 17,000 nodes as of 1989.NASA Technical Reports Server (August 1, 1989)
Space physics analysis network node directory (The Yellow Pages): Fourth edition
Retrieved August 19, 2018. Routing between networks with different address spaces involved the use of either "poor man's routing" (PMR) or address translation gateways. In December 1988, VAX/VMS hosts on the DECnet Internet were attacked by the Father Christmas worm.

CCNET

CCNET (Computer Center Network) was a DECnet network that connected the campuses of various universities in the eastern regions of the United States during the 1980s. A key benefit was the sharing of systems software developed by the operations staff at the various sites, all of which were using a variety of DEC computers.The DECSYSTEM-20 at Columbia University 1977-1988
Archived fro

on July 7, 2022. Retrieved August 3, 2022. As of March 1983, it included Columbia University, Carnegie Mellon University, and Case Western Reserve University. By May 1986, New York University, Stevens Institute of Technology, Vassar College and Oberlin College had been added. Several other universities joined later.Computing at Columbia Timeline
Archived fro
the original
on July 6, 2022. Retrieved August 3, 2022.

Hobbyist DECnet networks

Hobbyist DECnet networks have been in use during the 21st century. These include: * HECnet * Italian Retro DECnetRetro DECnet
Retrieved August 19, 2018.

References

General references

Carl Malamud Carl Malamud (born July 2, 1959) is an American technologist, author, and public domain advocate, known for his foundation Public.Resource.Org. He founded the Internet Multicasting Service. During his time with this group, he was responsible fo ...

, ''Analyzing DECnet/OSI Phase V''. Van Hostrand Reinhold, 1991. . * James Martin, Joe Leben, ''DECnet Phase V: An OSI Implementation''. Digital Press, 1992. . * DECnet-Plus manuals for OpenVMS are available at http://www.hp.com/go/openvms/doc/ * DECnet Phase IV OpenVMS manuals for DECnet Phase IV; these Phase IV manuals are archived on OpenVMS Freeware V5.0 distribution, at http://www.hp.com/go/openvms/freeware and other sites. * DECnet Phase IV architecture manuals (including DDCMP, MOP, NICE, NSP, DAP, CTERM, routing); at https://web.archive.org/web/20140221225835/http://h71000.www7.hp.com/wizard/decnet/ (the originals are mirrored a
DECnet for Linux
. * Cisco documentation of DECnet, at http://docwiki.cisco.com/wiki/DECnet {{Authority control History of computer networks Network protocols Digital Equipment Corporation OpenVMS