High noon in Desktop City. A mysterious gang of three paradigms has arrived in town. Some say the three came from the East, others say from the West. Their true names are elusive--people call them thin clients, hollow workstations, network workstations, diskless workstations, Windows terminals, Internet terminals, network computers (NCs), and more. Each member of the gang carries a unique weapon: One totes a shiny new pistol named the Intelligent Console Architecture (ICA), the second carries a trusty old rifle called X-terminal, and the third tucks a small derringer named Web browser in a sleeve holster. Despite the mystery surrounding this gang, its intent is clear--each member comes gunning for a share of desktop real estate in the Windows NT market.

With guns drawn and ready to fire, these paradigms aim to reduce the overall cost of deploying NT-based applications by minimizing cost on the desktops. The gang offers these cost reductions in two ways: You can put low-cost graphics terminals on the desktop or run thin client software on existing desktop units such as Windows PCs, Macs, and UNIX systems. Either way, your NT server's CPU, memory, and disk resources run the users' NT-based applications.

Two of these paradigms--the ICA-based and X-based--are similar; in fact, they're like brothers. The third paradigm--the Web browser--is a different sort of fellow. For this discussion, let's focus on the two similar paradigms, ICA and X. A later article will deal with the odd fellow, Web browser. So let's sidle on up to the ICA and X paradigms for a closer look-see.

X vs. ICA
The X-based paradigm in the NT market is the same X11 protocol technology the UNIX world has known for many years. Bringing X-terminal technology into the NT fold has resulted in some interesting changes in the X environment: For example, you can now purchase NT software that lets you boot diskless X-terminals from NT servers. Also, you can now run native NT applications on X-terminals (or with X-terminal emulation software). This capability opens a new area of interoperability--you can drop an NT server into a 100% UNIX shop, giving existing desktops instant access to NT-based applications, from Microsoft Word to full-blown SQL Server applications.

ICA resulted from Citrix's work on its WinFrame software. ICA is WinFrame's underlying protocol that lets workstations access NT applications over a network. Originally, ICA was for remote, dial-in workstations--ICA transmits a minimum amount of information over the wire, compressing the transmitted information to further save transmission time. Over time, while retaining its minimum-transmission and compressed-data characteristics, ICA expanded from a strictly dial-in protocol to one that encompasses LAN links.

ICA and X share several attributes: Both are fairly high-level protocols that operate over TCP/IP. Both keep the application intelligence--and the corresponding resource utilization--in the server. For example, when you run Word on X or ICA, Word runs in the server and uses server-side CPU, memory, and disk storage. In fact, you can think of X and ICA as network redirectors for ordinary keyboard, monitor, and mouse operations. You can deploy both ICA and X in standalone "terminals" or in software running in existing desktop computers. And both protocols are multitasking and multiuser solutions: They let you deploy one NT server to handle several desktop users.

I looked at ICA and X desktop-to-NT solutions in the Windows NT Magazine Lab, and those I tested share one more important attribute: A customized form of Citrix's WinFrame software drives the server. As Tim Daniels explains in his May review ("Citrix WinFrame 1.6 Beta"), WinFrame is a special OEM version of NT Server that lets multiple graphical terminals or desktops run applications from a single-server system. WinFrame supports the ICA model, but several vendors, including Insignia Solutions and Network Computing Devices (NCD), have modified WinFrame to support X-terminal access to NT Server applications. How many desktops you can support on one server varies, depending on the desktop's applications and the size of the server, but a good rule of thumb is that a reasonably configured dual-processor Pentium server can support up to 15 desktops--by the way, plan to add 8MB of server memory for each desktop system you want to support.

ICA and X differ in many ways, as well. First, to handle data compression and decompression, ICA consumes extra CPU resources on both the desktop systems and the servers. X does not add that overhead, but X consumes more network bandwidth and is more complex to set up and maintain than ICA. For example, to download operational and configuration information, most X-terminals must establish communications with a special server during bootup. Also, you must configure X-terminals to launch a command on the NT server to start a session, and this step can be annoying. In contrast, ICA was designed as a plug-and-play solution--most ICA terminals are ready to communicate with an application server after power on.

At present, the vendors producing X and ICA solutions are still arguing about which protocol--ICA or X--is best. Most vendors agree, however, that ICA is a better fit for low-speed access (e.g., over Remote Access Service--RAS--links or Internet connections). Also, Microsoft is including a limited-feature ICA client in the second Windows 95 Service Pack, and this move can certainly change the landscape of the battle.

The Attraction Factor
The X and ICA paradigms are appealing as a desktop solution not for their technical, wire-level technology, but for their ability to deliver NT-based applications to a variety of desktop equipment. Without X or ICA, desktop access to NT-based applications is limited to desktop systems that run either NT Workstation or Server or that use a remote-control product such as Symantec's pcANYWHERE or Avalan's Remotely Possible. (For more on these products, see John Enck, "Symantec's pcANYWHERE32," and "Avalan's Remotely Possible/32," May 1996.) The problem with the first option, of course, is the cost of configuring a desktop system so it can run NT.

The problem with the second approach is that remote-control products are not for high availability, high performance, multiuser access (however, they are good at letting a single non-NT desktop access an NT application). In contrast, with X or ICA, you can access NT-based applications with X-terminals; Windows (ICA) terminals, such as the ones Wyse and Tektronix manufacture; UNIX systems running ICA client software or X-terminal emulation software; Macintosh systems running ICA client software or X-terminal emulation software; Windows 3.11 or Windows for Workgroups (WFW) systems running ICA client software or X-terminal emulation software; or Win95 or NT systems running ICA client software or X-terminal emulation software.

If you choose a server-side product that supports both ICA and X technology (e.g., Insignia's NTRIGUE and NCD's WinCenter), you can mix and match desktop strategies. You can deploy X-terminals, Windows (ICA) terminals, ICA client software, and X-terminal emulation software as you need. In contrast, if you choose a product that supports only ICA (e.g., Tektronix's WinDD, Wyse's WinFrame, or Citrix's WinFrame), you'll be locked into one desktop paradigm. Note that most WinFrame-based software vendors ship DOS, 16-bit Windows, and 32-bit Windows ICA clients with their server software. These vendors typically provide client software for other environments (e.g., Mac or UNIX) as an additional, priced item.

In theory, X/ICA access to NT is a good idea. To test the theory, Windows NT Magazine brought the following products into our Lab for evaluation: the Wyse 2500T ICA terminal and Wyse's Version 1.5 implementation of WinFrame (for a case study of a Wyse and WinFrame solution, see Kevin Woodward, "ProStaff's WinFrame Solution," page 148); NCD's Explora X-terminal, WinCenter Pro 1.6 (NCD's version of WinFrame, which includes X support), and NCDware (NCD software that lets X-terminals boot from an NT server); a Tektronix Netstation 400 Series X/ICA terminal, which supports both paradigms, and WinDD 2.0 (Tektronix's implementation of WinFrame); and Insignia's NTRIGUE 2.0 (Insignia's version of WinFrame with X support).

These products' ability to deliver NT applications to non-NT desktops im-pressed me. (For information on the specific products we tested, please refer to the product sidebars.) We used a variety of X-terminal emulation software, including Insignia's NTRIGUE Mac Client, NCD's PC-Xware, and Hummingbird's Exceed to test X-to-NT access. We tested only interoperability among the server-side products and therefore did not include them in the product sidebars.

Is X/ICA Cost Effective?
Are you really saving money if you adopt an X or ICA desktop strategy? Well, the answer depends on where you're starting from and how you look at cost savings. If, for example, your organization has X-terminal systems, 386 or 486 PCs, or Macintoshes on the desktop, the X and ICA strategies let you introduce NT applications without spending money to upgrade your desktop hardware. In most medium- to large-scale organizations, this approach will be more cost effective than placing NT on every desktop--even after you figure in the higher cost for the software and hardware you need to drive the X or ICA server.

But what if you're building a new solution? Is the X or ICA approach always more cost effective? If you look at the equipment costs only, the savings depends on the scale. You can purchase a Windows (ICA) terminal for less than $1000, which will clearly help offset the cost of a high-end server. If you broaden your vision of cost to include the price of supporting and maintaining desktop equipment, X and ICA terminals reduce these costs because they have no local hard disk to maintain (or corrupt), no floppy drives to introduce games or viruses, and fewer moving parts to break.

Would you ever deploy X or ICA on new, full-scale PCs on the desktop? Probably not, but you might still find some useful applications for X/ICA on a smaller scale. For example, even if you roll out new PC hardware for the desktops, certain key applications may restrict you to running Windows or Win95 on certain desktops, or you may need to accommodate remote access from traveling laptops or telecommuters. X or ICA access is a good option in these situations.

One emerging application for ICA (but not X) is to have an ICA client plugin for your Web browser deliver applications over the Internet. When you click an ICA tag in a Web page, your browser launches your ICA client helper application, and bingo--you're running an NT application over the Internet. The possibilities for this technology range from software vendors offering product demos, to corporations offering employees and partner companies full-blown, multiplatform applications (remember, ICA clients are available for many hardware platforms). Of course, running ICA over the Internet comes close to the third paradigm, Web browsers. But, as you will see in a later article, the Web browser paradigm has a life of its own.

So when high noon comes in your organization, will you be facing this gang of desktop paradigms? Chances are pretty good that you will. And considering that you've probably already faced the Internet connection challenge, the TCP/IP-only network challenge, and the NT vs. NetWare challenge, chances are pretty good that you'll come out a winner again. Just remember to keep the sun at your back.