With the advent of thin clients, the world of computing has come full circle. In the beginning, there were big mainframe computers and dumb terminals. Then there was the personal computer revolution, and the power was pushed to the desktop. Now we have gone back to the future with thin clients connected to centralised servers.
We tested a thin-client/server solution from Microsoft and Citrix Systems, and we found it to be a good solution for enterprises looking to deploy new applications while retaining centralised administration and control.
The combination of these two server software packages is ideal for organisations with heterogeneous networks featuring different types of clients and running multiple protocols.
The solution we tested included Microsoft Windows NT 4.0 Terminal Server Edition (TSE), which extends the standard Windows NT platform to create a multi-user environment where all applications are executed on the server and client machines simply act as input/output devices. We also ran Citrix's MetaFrame server software, which adds several features to TSE.
First, TSE only supports Windows clients, but MetaFrame adds support for DOS, Java, OS/2, Unix-based clients and Apple Computer Inc.'s Macintosh. Second, TSE uses the Remote Display Protocol (RDP), which requires a high-bandwidth network and handles all communications with client machines. MetaFrame uses Citrix's proprietary Independent Computing Architecture (ICA) protocol, which works well over a wide range of network speeds all the way down to asynchronous dial-up lines. Third, the current version of RDP works only over Transmission Control Protocol/Internet Protocol networks, while ICA also works with IPX, SPX, NetBIOS and direct asynchronous connections.
Microsoft's recommends TSE as an upgrade path for terminal-based single-function applications. Citrix, on the other hand, offers tools to help manage multiple users and applications across multiple servers.
One advantage of the TSE/MetaFrame combination is easier administration. With all software running from the server, you only have to update a single copy rather than one copy at each client workstation. For large installations, this can translate into significant time savings.
Another benefit of the TSE/MetaFrame solution is improved technical support for users. The MetaFrame product includes a feature that lets an administrator view what is on a client workstation's screen. This tool is invaluable for help-desk support.
On the surface, MetaFrame appears to just expand the number of platforms and protocols supported by TSE. In actuality, MetaFrame provides several additional features targeted at large installations that require high levels of performance and availability.
For example, MetaFrame supports load balancing, which lets administrators equally share the processing power of multiple servers. Load balancing also makes it easy to scale an application simply by adding server hardware.
The performance of both TSE and MetaFrame depends on the server platform. The more memory and CPU power the server has, the better the software will perform and the easier it will be to serve multiple users. Our test server was a single processor, 200 MHz Intel Corp. Pentium MMX machine with 128M of memory.
We compared the performance of the Microsoft/Citrix solution running typical business applications to an alternate configuration where applications ran locally. Overall, the applications ran slightly slower on the server than when run locally. However, we saw significant performance improvements when running 32-bit applications such as Microsoft's Office 97, on older platforms. With the MetaFrame product, we saw a 33 MHz 486 PC running Windows 3.1 perform like a Pentium-class machine.
Installing the server portion of TSE is essentially the same as Windows NT 4.0. The CD-ROM-based installation took about an hour and requires that you know facts about your environment such as TCP/IP addresses for your server and gateway. You also will want to know how the TSE server will operate in your network in terms of domain controllers - master, slave or not at all.
On the client side you have several options for installation. The easiest way is to connect to a shared drive on the server and install the client files over the network. We used this method to install the Windows 95 and Windows 3.1 clients with no problems. You also can choose to create a set of installation floppy disks if necessary.
Citrix MetaFrame is an add-on to TSE and is installed after TSE. The only hitch we ran into was the registration nag screen informing us that we had 35 days to register the product over the Internet or by modem. If you're not connected to the Internet and don't have a modem, you can still register by fax or phone.
The minimum hardware requirement for TSE is a Pentium- or Alpha-based server with 32M of memory and an additional 4M to 8M for each concurrent user. In reality, you could support 10 to 20 simultaneous users with a dual 200MHz Pentium or better machine and 256M of memory.
Documentation for TSE is essentially the same as what you get with Windows NT with a few additions for setup and administration. The printed manuals are minimal unless you purchase the full set from Microsoft Press. On the other hand, MetaFrame comes with a complete set of well-written printed documentation.
How do you decide whether you need TSE or the TSE/MetaFrame combination? If you only support Microsoft-based clients, you probably will be OK with TSE alone. If, however, you have to support a mix of DOS, Unix and Macintosh systems, you'll need to purchase MetaFrame.
Ferrill, based at Edwards Air Force Base, California, is a principal engineer with Avionics Test & Analysis Corp. He can be reached at pferrill@fwb.gulf.net.
Report Card
Microsoft Windows NT Server 4.0 Terminal Server Edition and Citrix MetaFrame Microsoft: www.microsoft.com Citrix Systems: www.citrix.com Remarks: The combination of Windows NT Server 4.0 Terminal Server Edition and Citrix MetaFrame provides a solid platform for thin-client computing. In concert, these two products offer broad client and network protocol support along with administrative tools. Running on a powerful enough server, these products will perform at a level previously achieved only with desktop computers.
Final Score: Very Good