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Linux may soon lose support for the DECnet protocol

Ancient, yes, but its progenitor VMS isn't dead just yet

Updated There's a proposal to remove the code for the DECnet networking protocol from the Linux kernel… but what was DECnet anyway?

Microsoft software engineer Stephen Hemminger has proposed removing the DECnet protocol handling code from the Linux kernel. The timing is ironic, as this comes just two weeks after VMS Software Inc announced that OpenVMS 9.2 was really ready this time…

That announcement, of course, came some months after the first time it announced [PDF] version 9.2, as we covered in The Reg in May.

The last maintainer of the DECnet code was Red Hat's Christine Caulfield, who flagged the code as orphaned in 2010. The change is unlikely to vastly inconvenience many people: VMS is the last even slightly mainstream OS that used DECnet, and VMS has supported TCP/IP for a long time. Indeed, for decades, the oldest email in this reporter's "sent" folder was a 1993 enquiry about the freeware CMUIP stack for VMS.

One of the easier ways to bootstrap VMS on an elderly VAX these days is to install it on the SimH VAX hardware simulator, and then net-boot the real VAX from the simulated one. Anyone keen enough to do that will be competent to run an older version of Linux just for the purpose.

Although their existence is rapidly being forgotten today, TCP/IP is not the only network protocol around, and as late as the mid-1990s it wasn't even the dominant one.

The Linux kernel used to support multiple network protocols, but they are disappearing fast. In 2018, the same Mr Hemminger removed the last vestiges of Novell's IPX protocol from the kernel, joining its partner SPX, eliminated in 2002. The IPX/SPX stack was how Novell Netware servers communicated with its client machines, and in 1993 it was one of the default protocols in both Windows for Workgroups 3.11 and Windows NT 3.1. TCP/IP was just an optional extra.

For now, Linux still supports AppleTalk, the native network language of classic MacOS. AppleTalk was dropped from Mac OS X since 10.6 "Snow Leopard", so it's bound to go soon.

For a long time, DECnet was a significant network protocol. DEC supplied a client stack called PathWorks to let DOS, Windows and Mac clients connect to VAX servers, not only for file and print, but also terminal connections and X.11. Whole worldwide WANs ran over DECnet, and as a teenage student, your correspondent enjoyed exploring them.

The protocol wars are finally over. ®

Updated to clarify on 9 August

Linux formerly supported DECnet Phase IV, and it is DECnet Phase IV support that is being dropped. It never supported DECnet Phase V, which came later and did get rolled out in a few places.

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