DECnet

Last updated

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. Initially built with three layers, it later (1982) evolved into a seven-layer OSI-compliant networking protocol.

Contents

DECnet [1] was built right into the DEC flagship operating system OpenVMS since its inception. Later Digital ported it to Ultrix, OSF/1 (later Tru64) as well as Apple Macintosh and IBM PC running variants of DOS, OS/2 and Microsoft Windows under the name PATHWORKS, allowing these systems to connect to DECnet networks of VAX machines as terminal nodes. [2]

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. [3] DECnet code in the Linux kernel was marked as orphaned on February 18, 2010 [4] [5] and removed August 22, 2022. [6]

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 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, 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 (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 operating system, or a small number of PDP-8s running the RTS-8 operating system, with communication over point-to-point (DDCMP) links between nodes.

Phase II (1975) [7] 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, TOPS-20 and VAX/VMS [8] 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). [9] Support for networks of up to 255 nodes with 8-bit addresses, 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.

DECnet Phase IV protocol suite
ApplicationDAP: Data Access Protocol

CTERM: Command Terminal

Network ManagementNICE: Network Information (and) Control Exchange

MOP: Maintenance Operations Protocol

SessionSCP: Session Control Protocol
TransportNSP: Network Service Protocol
NetworkDRP: DECnet Routing Protocol
Data linkDDCMP: Digital Data Communications Message Protocol
Ethernet, Token Ring, HDLC, FDDI, ...
Physical Ethernet, Token Ring, FDDI, ...

1981–1986

Phase IV [10] [11] and Phase IV+ (1982). Phase IV was released initially to RSX-11 and VMS systems, later TOPS-20, TOPS-10, ULTRIX, VAXELN, and RSTS/E gained support. Support for networks of up to 64,449 nodes (63 areas of 1023 nodes) with 16-bit addresses, datalink capabilities expanded beyond DDCMP to include Ethernet local area network support as the datalink of choice, expanded adaptive routing capability to include hierarchical routing (areas, level 1 and level 2 routers), VMScluster 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 does in the TCP/IP 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 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 DIGITAL ever shipped with the notable exception of RT-11. 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 LAT for serial terminal access via Terminal servers. 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 [12] 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 (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 TCP/IP were added via the IETF 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, [13] 15,000 nodes (in 39 countries) as of 1987, [14] and 54,000 nodes as of 1990. [15]

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), Energy Sciences Network, and other research and education networks. [16] [17] The network consisted of over 17,000 nodes as of 1989. [18] Routing between networks with different address spaces involved the use of either "poor man's routing" (PMR) or address translation gateways. [16] 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. [19] 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. [20]

Hobbyist DECnet networks

Hobbyist DECnet networks have been in use during the 21st century. These include:

See also

Related Research Articles

<span class="mw-page-title-main">Digital Equipment Corporation</span> U.S. computer manufacturer 1957–1998

Digital Equipment Corporation, 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 until he was forced to resign in 1992, after the company had gone into precipitous decline.

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 suite are the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and the Internet Protocol (IP). Early versions of this networking model were known as the Department of Defense (DoD) model because the research and development were funded by the United States Department of Defense through DARPA.

<span class="mw-page-title-main">OSI model</span> Model of communication of seven abstraction layers

The Open Systems Interconnection (OSI) model is a reference model from the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." In the OSI reference model, the communications between systems are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

In computer networking, Point-to-Point Protocol (PPP) is a data link layer communication protocol between two routers directly without any host or any other networking in between. It can provide loop detection, authentication, transmission encryption, and data compression.

<span class="mw-page-title-main">VAX</span> Line of computers sold by Digital Equipment Corporation

VAX 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 VAX-11/780, introduced October 25, 1977, was the first of a range of popular and influential computers implementing the VAX ISA. The VAX family was a huge success for DEC, with the last members arriving in the early 1990s. The VAX was succeeded by the DEC Alpha, which included several features from VAX machines to make porting from the VAX easier.

<span class="mw-page-title-main">OpenVMS</span> Computer operating system

OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using OpenVMS include banks and financial services, hospitals and healthcare, telecommunications operators, network information services, and industrial manufacturers. During the 1990s and 2000s, there were approximately half a million VMS systems in operation worldwide.

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 piece of software. The implementation of SNA takes the form of various communications packages, most notably Virtual Telecommunications Access Method (VTAM), the mainframe software package for SNA communications.

A virtual private network (VPN) is a mechanism for creating a secure connection between a computing device and a computer network, or between two networks, using an insecure communication medium such as the public Internet.

<span class="mw-page-title-main">Ultrix</span> Series of discontinued Unix operating systems by DEC

Ultrix is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations.

Peripheral Interchange Program (PIP) was a utility to transfer files on and between devices on Digital Equipment Corporation's computers. It was first implemented on the PDP-6 architecture by Harrison "Dit" Morse early in the 1960s. It was subsequently implemented for DEC's operating systems for PDP-10, PDP-11, and PDP-8 architectures. In the 1970s and 1980s Digital Research implemented PIP on CP/M and MP/M.

<span class="mw-page-title-main">RSTS/E</span> Computer operating system

RSTS is a multi-user time-sharing operating system developed by Digital Equipment Corporation for the PDP-11 series of 16-bit minicomputers. The first version of RSTS was implemented in 1970 by DEC software engineers that developed the TSS-8 time-sharing operating system for the PDP-8. The last version of RSTS was released in September 1992. RSTS-11 and RSTS/E are usually referred to just as "RSTS" and this article will generally use the shorter form. RSTS-11 supports the BASIC programming language, an extended version called BASIC-PLUS, developed under contract by Evans Griffiths & Hart of Boston. Starting with RSTS/E version 5B, DEC added support for additional programming languages by emulating the execution environment of the RT-11 and RSX-11 operating systems.

IPX/SPX stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and SPX are networking protocols used initially on networks using the Novell NetWare operating systems. They also became widely used on networks deploying Microsoft Windows LANS, as they replaced NetWare LANS, but are no longer widely used. IPX/SPX was also widely used prior to and up to Windows XP, which supported the protocols, while later Windows versions do not, and TCP/IP took over for networking.

Local Area Transport (LAT) is a non-routable networking technology developed by Digital Equipment Corporation to provide connection between the DECserver terminal servers and Digital's VAX and Alpha and MIPS host computers via Ethernet, giving communication between those hosts and serial devices such as video terminals and printers. The protocol itself was designed in such a manner as to maximize packet efficiency over Ethernet by bundling multiple characters from multiple ports into a single packet for Ethernet transport.

VAXELN is a discontinued real-time operating system for the VAX family of computers produced by the Digital Equipment Corporation (DEC) of Maynard, Massachusetts.

In computer networking, DECserver initially referred to a highly successful family of asynchronous console server / terminal server / print server products introduced by Digital Equipment Corporation (DEC) and later referred to a class of UNIX-variant application and file server products based upon the MIPS processor. In February 1998, DEC sold its Network Products Business to Cabletron, which then spun out as its own company, Digital Networks, in September 2000.

PATHWORKS was the trade name used by Digital Equipment Corporation of Maynard, Massachusetts for a series of programs that eased the interoperation of Digital's minicomputers and servers with personal computers. It was available for both PC and Mac systems, with support for MS-DOS, OS/2 and Microsoft Windows on the PC. Before it was named PATHWORKS, it was known as PCSA.

<span class="mw-page-title-main">B.A.T.M.A.N.</span> Routing protocol for multi-hop mobile ad hoc networks

The Better Approach to Mobile Ad-hoc Networking (B.A.T.M.A.N.) is a routing protocol for multi-hop mobile ad hoc networks which is under development by the German "Freifunk" community and intended to replace the Optimized Link State Routing Protocol (OLSR) as OLSR did not meet the performance requirements of large-scale mesh deployments.

Distributed Overlay Virtual Ethernet (DOVE) is a tunneling and virtualization technology for computer networks, created and backed by IBM. DOVE allows creation of network virtualization layers for deploying, controlling, and managing multiple independent and isolated network applications over a shared physical network infrastructure.

The History of the Berkeley Software Distribution begins in the 1970s.

<span class="mw-page-title-main">Sniffer (protocol analyzer)</span> Network packet and protocol analyzer

The Sniffer was a computer network packet and protocol analyzer developed and first sold in 1986 by Network General Corporation of Mountain View, CA. By 1994 the Sniffer had become the market leader in high-end protocol analyzers. According to SEC 10-K filings and corporate annual reports, between 1986 and March 1997 about $933M worth of Sniffers and related products and services had been sold as tools for network managers and developers.

References

  1. ↑ James M. Moran; Brian J. Edwards (February 1984). "Giving DECnet a LAN". Hardcopy . pp. 62–65.
  2. ↑ "SYSTEMS STRATEGIES". The New York Times . May 13, 1992. DECnet/SNA gateway solution
  3. ↑ "DECnet for Linux". SourceForge. Archived from the original on October 4, 2009. Retrieved June 26, 2018.
  4. ↑ Caulfield, Christine (February 18, 2010). "Orphan DECnet". Linux Kernel ChangeLog 2.6.33. Archived from the original on August 11, 2011. Retrieved June 26, 2018.
  5. ↑ "kernel/git/torvalds/linux.git - Linux kernel source tree". git.kernel.org. Retrieved August 3, 2022.
  6. ↑ "kernel/git/torvalds/linux.git - Linux kernel source tree". git.kernel.org. Retrieved October 6, 2023.
  7. ↑ Digital Equipment Corporation (1978). "Nineteen Fifty-Seven to the Present" (PDF). Computer History Museum. p. 53. Archived from the original (PDF) on December 21, 2013. Retrieved June 26, 2018.
  8. ↑ "Software Product Description: DECnet-VAX, Version 1" (PDF). DEC. September 1978. Retrieved May 23, 2023.
  9. ↑ "Introduction to DECnet (Phase III)" (PDF). May 22, 1982.
  10. ↑ "Overview of DECnet" (PDF).
  11. ↑ "The DECnet Phase IV Specifications".
  12. ↑ James Martin; Joel Leben (1992). DECnet Phase V: An OSI Implementation Network. ISBN   978-0-1320-2987-2.
  13. ↑ Erik E. Fair (January 5, 1984). Re: The Plethora of Networks. Usenet fa.human-nets. Retrieved August 19, 2018. Archived March 14, 2016, at the Wayback Machine
  14. ↑ Network World (September 7, 1987), p.4. DECworld network links hotels, ocean liners. Retrieved August 19, 2018.
  15. ↑ Network World (August 6, 1990), p.1. DEC shares early lessons on DECnet V. Retrieved August 19, 2018.
  16. 1 2 L. Stuart Vance (1990). The User's Directory of Computer Networks, The DECnet Internet. Retrieved August 19, 2018.
  17. ↑ L. Stuart Vance (1990). The User's Directory of Computer Networks, The DECnet Internet (Publisher Summary). Retrieved August 19, 2018.
  18. ↑ NASA Technical Reports Server (August 1, 1989). Space physics analysis network node directory (The Yellow Pages): Fourth edition. Retrieved August 19, 2018. Archived March 8, 2021, at the Wayback Machine
  19. ↑ The DECSYSTEM-20 at Columbia University 1977-1988. Archived from the original on July 7, 2022. Retrieved August 3, 2022.
  20. ↑ Computing at Columbia Timeline. Archived from the original on July 6, 2022. Retrieved August 3, 2022.
  21. ↑ HECnet - The hobbyist DECnet. Retrieved January 24, 2022.
  22. ↑ Retro DECnet. Retrieved August 19, 2018.

General references

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.