DECnetPlus

DECnet Plus, also known as DECnet Phase V, is a networking protocol suite developed by Digital Equipment Corporation (DEC). It superseded the earlier DECnet Phase IV protocol. DECnet Plus introduced several enhancements, including support for the Open Systems Interconnection (OSI) model, allowing for greater interoperability with other networking standards. It also featured improved network management capabilities and a more robust architecture.

The protocol suite comprises various layers, covering functionalities from the physical link to the application layer. Key components include the Network Services Protocol (NSP) for reliable data transfer, the Routing Protocol for DECnet (RP) for routing packets across the network, and the Layered Protocol (LP) for transport and session management. DECnet Plus was designed to be highly scalable and adaptable, supporting a wide range of hardware and operating systems, particularly those from DEC such as VMS.

While DEC was acquired by Compaq, and subsequently by Hewlett-Packard, DECnet Plus remained in use within many organizations. However, with the widespread adoption of TCP/IP as the dominant networking standard, the usage of DECnet Plus has declined significantly over time. Nevertheless, its legacy can be seen in the evolution of networking protocols and its contribution to the development of distributed computing.