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| DECnet Phase IV | |
|---|---|
| Name | DECnet Phase IV |
| Developer | Digital Equipment Corporation |
| Initial release | 1977 |
| Latest release | 1983 |
| Status | Historical |
| Written in | VAX/VMS |
| Platform | VAX, DECnet-Plus, PDP-11 |
DECnet Phase IV DECnet Phase IV was a widely deployed networking suite developed by Digital Equipment Corporation in the late 1970s and early 1980s that provided node-to-node networking, routing, and network services across Local Area Network and Wide Area Network topologies. It extended earlier DECnet research from DEC PDP projects and influenced contemporaneous systems from IBM, Xerox PARC, and Bell Labs. Phase IV saw adoption in academic, corporate, and governmental sites such as MIT, Stanford University, NASA, and Los Alamos National Laboratory.
Phase IV evolved from experimental initiatives at Digital Equipment Corporation and efforts by teams in Maynard, Massachusetts and Palo Alto Research Center. It standardized procedures for interprocess communication used by systems including VAX-11/780, PDP-11/70, and later VAX 11/785. Key milestones intersected with projects at Bolt Beranek and Newman, Honeywell, Hewlett-Packard, and standards work at Institute of Electrical and Electronics Engineers gatherings, while deployments interfaced with networks overseen by Energy Sciences Network and BITNET participants.
The layered Phase IV architecture implemented a suite of protocols for routing, transport, and application services, integrating with systems like UNIX variants and VMS. Its link-level support encompassed interfaces to Ethernet, X.25 clouds, and proprietary links used in ARPA-funded trials. Protocol suites featured address resolution and end-to-end communication mechanisms that paralleled efforts at Stanford Research Institute and research at Bell Labs, influencing protocol work later codified in Internet Engineering Task Force output. Interoperability experiments were conducted with systems from Sun Microsystems, Siemens, AT&T, and Northern Telecom.
Phase IV introduced a hierarchical 16-bit node address plan enabling area-based routing akin to schemes discussed at RAND Corporation and implemented in regional networks connected to NSFNET. Routing protocols supported table exchange and shortest-path calculations influenced by algorithms from Dijkstra-inspired research and implementations compared with routing in Berkman Center testbeds and Stanford Linear Accelerator Center installations. Administrative addressing allowed integration with legacy addressing used by Cambridge Computer Laboratory and facilitated gateways to DECnet Phase V trials and external systems from Tymnet and X.25 service providers.
Phase IV provided remote file access, remote command execution, directory and naming services, and remote procedure features used in labs at Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and CERN testbeds. Service primitives supported remote job submission similar to practices at Argonne National Laboratory and interactive sessions used by researchers at Carnegie Mellon University. Security and authentication mechanisms were primitive by later standards but interoperated with host-based controls found in VAXcluster environments and administrative domains like Department of Energy facilities.
Implementations ran on VAX-11 systems, PDP-11 series machines, and routers assembled by Digital Equipment Corporation hardware groups in Maynard and Bangalore labs. Front-end processors and network interface cards were supplied by partners including DEC, Western Digital, 3Com, and Intel, and integrated into systems alongside storage arrays from StorageTek and EMC Corporation-era devices. Network management consoles interfaced with operator terminals built by Tektronix and graphical consoles inspired by Xerox Alto research.
Operational deployments used combinations of leased lines, campus LANs, and packet-switched services provided by Comsat and regional carriers; sites such as Princeton University, University of California, Berkeley, and Yale University ran production networks for academic workloads. Network administrators applied practices developed in conjunction with consultants from Bellcore and academic centers including University College London and followed configuration approaches later mirrored in Open Systems Interconnection discussions. Interconnection with international research networks involved coordination with operators at CERN, EPFL, and Rutherford Appleton Laboratory.
Phase IV contributed architectural ideas to later efforts including TCP/IP adoption in research networks, influenced DEC’s own DECnet Phase V, and informed product strategy at Digital Equipment Corporation that affected acquisitions by Compaq and later Hewlett-Packard. Concepts from Phase IV echoed in routing research at MIT Laboratory for Computer Science and influenced commercial networking products by Cisco Systems and protocol work at the IETF. Its deployment in scientific institutions left an imprint on networking curricula at Massachusetts Institute of Technology, Stanford University, and University of Illinois Urbana-Champaign.
Category:Computer networking Category:Digital Equipment Corporation Category:History of computing