One Protocol to Rule Them All? Maybe Not

Just because TCP/IP may be the de facto standard networking protocol in today's Internet-driven world, it doesn't mean DECnet has been abandoned. And it has its advantages.
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 protocols.

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 servers.

''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 DECnet.

''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 Quayle.

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 DECnet.

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 doing.

''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 hidden.

''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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