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NT Enterprise
NT Administrator
Looking for Multi-User NT?
Set up an application server that gives multiple users the Windows apps they want.

-- by Tom Henderson

The folks at Microsoft know a good idea when they see one, even if they didn't think of it first. So it's no surprise that Microsoft is challenging Citrix with its Hydra software, which turns NT Server 5.0 into a multi-user system (see NT Newstrends in this issue)

My company has been using a Citrix WinFrame Enterprise daily for over a year with astonishing results. You have to love a product that stays awake for a year with virtually no administration and maintenance when it's serving two to seven concurrent sessions per day of an accounting application written for Win16. The connections are made via the Citrix ICA protocol, which I'll explain later. An app server that provides whatever Windows apps we want has solved what we feared would be a difficult problem.

Our challenge was to find a way to connect seven branch offices to accounting software without running several instances of the software in each branch office. We wanted to avoid the need to upload and synchronize data from each profit center to the master set of books. Hardware duplication, along with administrative and capital costs, would have been a heavy burden.

We chose Citrix's WinFrame Enterprise server over several highly evolved remote access servers from Cubix, Evergreen Systems and a few others. These alternative remote-access servers let you use PC Cards via remote-control applications. At the time, Stax' remote-control software appeared to be the common choice for emulation among the remote-control servers. We were certainly happy with it, and we also used Symantec's pcAnywhere.

However, PC Cards lock the hardware platform. Citrix offered a scalable approach.

Instead of discrete PC Cards, Citrix employs a single server with CPUs shared by multiple instances of NT workstations. Each virtual session has its own address space. NT resources, such as disks, network connections (NetWare servers included), and dial-in or network-based log-ons, are shared.

We were apprehensive about WinFrame. First, we were concerned that a user could crash the entire server and all user instances running at the time. We also worried that a WinFrame server would sag proportionately with an increased number of users. WinFrame's recommended requirements were 16MB of DRAM per user in our app, putting a burden on our CPU.

However, price considerations strongly favored WinFrame. The license fee for 15 users was around $6,000. When coupled with the recommended hardware platform, the cost would rise to just over $10,000. That was one-third the cost of a similarly configured system from Cubix, and half the cost of an Evergreen Systems platform. The choice became easier.

The background

WinFrame Enterprise is an evolution of MultiWin, a product that runs over OS/2 but delivers Windows via the Intelligent Console Architecture (ICA) protocol. ICA disassociates the console from a distinct address space for each user app. In WinFrame Enterprise, the NT kernel is slightly modified. Later, that presented us with a small problem: Microsoft service packs have to be modified by Citrix to work on WinFrame. Otherwise, the MS-supplied service packs refuse to install because they can't find a Microsoft kernel. Citrix delivers them a few months after Microsoft, which turns out to be a blessing when Microsoft rapidly patches its service packs. Citrix's service patches already have the fixes when they're released the first time.

Microsoft has licensed ICA, and it's inside Windows NT 4.0. It runs over TCP/IP, IPX and NetBEUI in any combination for any user who can get a connection via one of these protocols. The disassociation means that it's possible to run an NT session on an IBM AT (with a VGA display and mouse) with no difficulty. If you really want to use small hardware, there's a port in progress for the Psion and for Windows CE. ICA also works in browsers, such as the one in the Wyse WinTerm NetPC.

Other uses for ICA

Sun Microsystems has also licensed ICA, so we can expect an adaptation to Java. This could make it easy for Sun's JavaStations to get sessions on WinFrame Enterprise, helping the company make the JavaStation a viable network member. Tektronix has already turned ICA into WinDD. WinDD allows a number of UNIX workstations to achieve the same connectivity that Sun's looking for-Windows sessions.

Microsoft obviously covets the type of success Citrix has had with WinFrame, and the Hydra product will either have WinFrame technology or a facsimile for NT 5. Even IBM has licensed ICA technology as a simple means to allow OS/2 Warp users to run Windows sessions.

Client-side use of WinFrame is simple (see sidebar, "Easy Access"). I can't recommend using the client with modems under 28.8Kb per second, but faster modems are acceptable, if slightly hesitant. The 56Kbps digital lines that we use to connect the branch offices work well even when two phone lines are mixed in the same connection. From home, I frequently dial in to the WinFrame server to cruise the Internet through our office's T1 connection-and it's far quicker than my fastest notebook. There's an eight-port NT Remote Access Server running in the same machine, a Pentium 133 with 96MB of DRAM.

Connection controls

Citrix administration follows the NT administration model, but you can control sessions in several ways. You can initiate the sessions via IPX, NetBEUI or TCP/IP.

My company chose TCP/IP for our WAN users, and IPX for corporate sessions. Users can be brought directly to a specific application, or they can receive a Windows NT Program Manager screen.

When connected to NT RAS, dial-in sessions are permitted with optional fixed or mobile dial-back capability. We run two such lines on a fixed dial-back basis to increase security.

Except for the occasional response lag during high network traffic conditions, the accounting application that we use completes its transactions quickly. We replaced the Ethernet 10BaseT network card in the original setup with a 100BaseT and received some performance increase. But the file server for the accounting app is now the laggard in the delivery chain. The next performance increase will come when we swap the file server disk array with an Ultra-SCSI subsystem and a faster SCSI adapter.

The solution that Citrix provides, multi-user terminal sessions in a host environment (where the host is NT), is one of those great, malleable puzzle pieces that transcends hardware. I'm not sure that I want an ICA NT session on my new Philips Velo CE, but, then again, you never know.

Contributing editor Tom Henderson is senior vice president of engineering for Indianapolis-based Unitel. Contact Tom in the "NT Enterprise Administrator" topic of WINDOWS Magazine's areas on America Online and CompuServe, or care of the editor at the e-mail addresses here.

Windows Magazine, June 1997, page NT41.

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