Wednesday, June 12, 2024

One Protocol to Rule Them All? Maybe Not

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Just because TCP/IP may be the de facto standard networking protocol in

today’s Internet-driven world, it doesn’t mean everyone abandoned older


DECnet, in particular, can be found in various nooks and crannies, and

those using it say they have no plans to eliminate it.

Take the case of Quayle Consulting of Columbus, Ohio, a systems

integration software development, system management and data migration

firm that harnesses a mix of IP and DECnet on its 25-system internal

network. The network consists mainly of a wide range of VMS systems

running on VAX, Alpha, and Itanium, as well as various Windows and Linux


”Keeping DECnet requires no effort,” says Stan Quayle, principal of

Quayle Consulting. ”To totally eliminate it, I’d have to go through

substantial work, so why bother?”

Your Father’s Network

DECnet was originally developed in 1974 by DEC and was a standard of data

centers in the 1970s and ’80s. Like TCP/IP, it basically is a set of

rules for the transmission of data between systems. Two versions can

still be found if you look hard enough: DECnet Phase IV developed in the

’80s, and DECnet-Plus (also known as DECnet/OSI or DECnet Phase V), which

evolved in the early ’90s.

This later version completed the separation of DECnet from the OpenVMS

operating system. As a result, DECnet can use IP as the transport, or

alternatively, VMS can run on IP independently of DECnet — even VMS

stalwarts don’t have to use DECnet. And indeed, many have gradually

phased over to exclusively IP environments.

It’s hardly surprising then that most analysts don’t pay any attention to


”I thought DECnet and other protocols had pretty much lost to TCP/IP in

the last century,” says IT analyst Richard Ptak of Ptak, Noel and

Associates of Amherst, N.H.

What isn’t so well known, though, is that many VMS shops brought in IP,

but held onto DECnet, too, for specific tasks. Quayle Consulting, for

instance, uses DECnet internally on its local network and to remotely

oversee backup of VMS disks via DECnet to Linux systems (there is an open

source version of DECnet available for Linux.) In

addition, the company transfers files to client sites in Columbus, Ohio

and Winston-Salem, N.C., using DECnet over IP via the Internet.

”We replicate important files and development environments on a daily

basis to our partners,” says Quayle. ”DECnet preserves all the file

characteristics, which are very important in VMS.”

If you need to access a file on a remote system, the VMS file syntax

supports those operations directly. Take a situation, for example, where

a local file is called ”XYZ.ABC” and the same file in North Carolina is

called ”N2::XYZ.ABC”. You still can access it remotely using DECnet

without any need to FTP or use a browser. It appears to almost be in the

local file system.

”DECnet-over-IP on the Internet is definitely very robust,” says


IP, though, is the industry standard protocol. These days, everybody

knows how to use TCP/IP. That means anyone also deploying DECnet has to

license both protocols. The good news is that the DECnet fees are a bit

less than those for TCP/IP.

What about heterogeneous sites where universes collide? Wht about older

systems based on VMS that have to interface with newer Wintel or UNIX

systems that run exclusively on IP?

Interestingly, networking staff sometimes remain blissfully unaware of

the presence of DECnet over IP.

”In large corporate sites, the presence of DECnet on a LAN is considered

a minor nuisance, if it’s noticed at all,” says Quayle. ”Proper network

design can keep all the DECnet traffic isolated on a single virtual LAN

(VLAN), and not irritate anyone else.”

Not Just Living in the Past

Far from just hanging onto the past or being resistant to progress, those

using DECnet insist it makes life a lot easier. IP jockeys often complain

about problems with regard to subnet masks, default gateways, multiple IP

addresses per routing host and the frequent changes needed in IP

addresses during cabling upgrades. Such shortcomings are minimized on


Further, there are certain capabilities present in DECnet that have never

evolved in TCP/IP. These include transparent remote file access, session

management and validation, and integrated system management access. These

functions can make DECnet easier to deploy — if you know what you are


”When I implement a complex, networked application, the DECnet

facilities dramatically decrease the time-to-deployment, cost, and risk,

while increasing the integrity of the application,” says Bob Gezelter, a

software consultant from Flushing, N.Y.

But it’s security that stands out as a big reason to hold onto DECnet.

It’s the industry standard platforms, such as IP and Wintel, that attract

the vast majority of hacker activity, and just about anyone with a

network monitor can peer into TCP/IP. By the simple expedient of

retaining DECnet for VMS-based systems, the data inside is almost

impossible to get at. By using DECnet over IP, the details of routing are


”Since DECnet is a less well-known protocol, nobody is attempting to

hack it,” says Quayle.

But it isn’t just lack of familiarity that protects users of this veteran

protocol. DECnet offers a full session control implementation,

facilitating applications that use the requestor’s identity and

authorization in a variety of ways, without requiring the implementer of

a network application to conduct validation or privilege checks. Thus, it

is natively more secure than IP.

But vendor support, not functionality or security, could ultimately bring

about the demise of DECnet. Some of the newer routers don’t support aging

protocols. Over time, DECnet users could be forced to rely on the

second-hand equipment market, much like users of VAX hardware are today.

If it comes to that, most of the remaining users may decide that staying

on DECnet is no longer a luxury they can afford.

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