What is "dnet"

DNET is a proprietary software suite of network protocols created by Swedish Dataindustrier AB DIAB, originally deployed on their Databoard products. It was based upon X.25, which was particularly popular in European telecommunications circles at that time. In that incarnation it was rated at 1 Mbit/s over RS-422.

In the 80's, ISC Systems Corporation (ISC) purchased DNET as part of their purchase of DNIX, and ported it to run over Ethernet. ISC's choice of DNET over TCP/IP was in part due to the relative light weight of the DNET protocol stack, allowing it to run more efficiently on the target machinery. DNET was also auto-configuring so there was no manual configuration of the local network, all that was required was that each machine in a network be given a unique name. This simplicity was advantageous in ISC's market.

Being based on X.25, DNET was connection-oriented, datagram-based (as opposed to a byte stream), supported out-of-band (interrupt) messages, and provided link-down notifications to its clients and servers so that applications did not have to provide their own heartbeats. In the financial community these were all considered advantages over, say, TCP/IP. DNET also supported Wide Area Networks (WAN) using X.25 point-to-point communication links, either leased line or dialup (see also Data link). (WAN support did require manual configuration of the gateway machines.)

DNET provided named network services, and supported a multicast protocol for finding them. Clients would ask for a named service, and the first respondent (of potentially many) would get the connection. Servers could either be resident, in which case they registered their service name(s) with the protocol stack when they were started, or transient, in which case a fresh server was forked/execed for each client connection.

DNET at ISC consisted of the following services:

• netman (the main networking client/server support handler)
• raccess (remote file access via /net/machine/path/from/raccess/root...)
• rx (remote execution)
• ncu (network login)
• bootserver ( diskless workstation boot service)
• dmap (ruptime analog)

There were many more services than these at a typical DNET installation - these are representative.