The Digital Connection, Part 2

File Transfer, File Sharing, Printer Sharing, and Program-to-Program Communications

Although terminal access is certainly an important component in anyhost-based network (see, "The Digital Connection, Part 1" in the Marchissue of Windows NT Magazine), it's not the only consideration.When you introduce PCs or Windows NT Workstations into a network, your need forhost-connectivity services typically expands to include file transfer and moreadvanced network services, such as directory and file sharing, printer sharing,and program-to-program communications. Let's take a look at how thesenon-terminal services come into play in Digital Equipment's networks.

The network services available in Digital's TCP/IP networks are remarkablysimilar to those in most UNIX-based TCP/IP networks. Specifically, you can usethe Telnet protocol for terminal access, the File Transfer Protocol (FTP) forfile transfer, the Network File Services (NFS) protocol for directory and filesharing, the Line Printer Daemon/Line Printer Requester (LPD/LPR) protocol forprinter sharing, and old-fashioned TCP/IP sockets (i.e., Berkeley sockets) forprogram-to-program communications. The TCP/IP suite of protocols and services isavailable for all of Digital's commercial operating systems, including DigitalUNIX, OpenVMS, Ultrix (a Digital UNIX precursor), and even Digital's "closed"VMS operating system.

At one time, Digital didn't support TCP/IP under VMS and offered itsproprietary DECnet suite of protocols and services instead. The DECnet suite isa well-rounded, robust architecture for implementing distributed processing andclient/server applications. The combination of VMS and DECnet was strategicallyimportant to Digital when the company was competing against IBM's host-centricmainframe architecture. Instead of selling processor or central resourceupgrades to give customers more power (the IBM approach), Digital sold customersanother computer to go on their networks.

DECnet shares a number of similarities with TCP/IP--as VMS shares a numberof similarities with UNIX--but DECnet also provides some unique advantages inseveral key areas.

DECnet services originally were geared toward peer-to-peer communicationsbetween Digital hosts. When PCs arrived on the scene, Digital and Digitalconnectivity vendors had to devise new solutions for integrating PCs into DECnetnetworks.

The Demanding Desktop
The first approach to PC-to-Digital connectivity was to bundle simplemodem-transfer protocols with terminal-emulation software. These protocolsincluded Kermit, Xmodem, Ymodem, and eventually Zmodem, but Kermit was by thefar the most popular. Some Digital connectivity vendors such as Walker, Richer &Quinn (WRQ) also developed their own proprietary file-transfer protocols forinclusion with their terminal-emulation software. Although this approach waslimited in scope, it was an effective solution for a variety of applications.It's still used frequently today.

As PCs became more sophisticated, demands for more sophisticatedPC-to-Digital connectivity tools increased. Digital responded by developing aproduct called DECnet-DOS that delivered many--but not all--of DECnet'scapabilities to the PC environment. In time, DECnet-DOS evolved into a productcalled Pathworks, which quickly became Digital's flagship product forconnectivity to its networks from DOS, Windows, OS/2, and Macintoshworkstations.

At first, Pathworks was a DECnet-oriented product that provided thefollowing services:

As TCP/IP became more popular--or from Digital's perspective, as DECnetbecame less popular--Digital expanded Pathworks to include TCP/IPcapabilities (e.g., Telnet and FTP), NetBEUI support for Pathworks connections,and support for NetWare protocols and services (including host-side softwarethat emulates a NetWare server instead of a LAN Manager server). All theoriginal capabilities listed are still available in the LAN Manager version ofPathworks.

The Transition to NT
Given Digital's investment in the future of Windows NT technology, you wouldthink that the company would have developed a robust version of Pathworks forthe NT environment. Although it has to a certain extent, Digital also has takenthe opportunity to weed out some of the protocols and services it wasn'tparticularly fond of. Therefore, if you look at the capabilities of Pathworksfor Windows NT, you will find that it offers:

Notice anything missing from this list? Pathworks for Windows NT does notinclude the two native terminal-transport protocols, CTERM and LAT. These twoprotocols are Digital's least favorite--for a variety of reasons--and have notbeen ported to NT. If you want terminal access to Digital hosts, you need to useTelnet or employ a third-party package. (A list of third-party vendors appearswith my March column, as well as more information on CTERM and LAT.)

Viable and Welcome
Despite the absence of CTERM and LAT, Pathworks for Windows NT is a viableand welcome member of the Pathworks family of products. Furthermore, althoughDigital is clearly moving away from DECnet and proprietary networkimplementations, Pathworks remains Digital's premiere client/server connectivitysolution. It will most likely be around until the last DECnet network is shutdown and dismantled. And that's likely to be a long time from now.