WinFrame, MetaFrame and Terminal Server: The Difference Is ICA

When Microsoft Corp. announced it would be developing Terminal Server last year, it would have been easy to think it was time for employees at Citrix Systems Inc. to pack up and go home. Citrix had pioneered the multiuser Windows market in 1995, but it was hard to see how the company could compete against a similar product from Microsoft itself.

The answer to that question soon became abundantly clear: If you can’t beat ‘em, join ‘em. Instead of trying to compete head-to-head, Citrix signed a 5-year marketing and research and development agreement with the software giant. The two companies agreed to work together to develop Windows Terminal Server. In exchange, Citrix received a $75 million payment along with a royalty arrangement estimated to be worth about $100 million, but more importantly, it dodged a potentially deadly bullet.

The fruits of the arrangement ripened last month at PC Expo, when Microsoft and Citrix made simultaneous announcements: Windows NT Server 4.0 Terminal Server Edition (formerly code-named Hydra), and Citrix MetaFrame (formerly code-named Picasso).

But in spite of, or perhaps because of, the attention these products have garnered, there remains some confusion about the relationship between the products. At a recent trade show in Boston, John Marchese, director of the thin client consultancy for Inacom Professional Services (New York), a technology services company, explained the similarities and differences between MetaFrame and Terminal Server during a session titled “Application Deployment With Windows Terminal and Citrix.”

Citrix’s original product, WinFrame, contained both the ability to connect multiple users to a single application running on Windows NT, and the functionality to separate application logic from the user interface, enabling the application to run on the server but be controlled by one or more remote clients.

Under the deal with Microsoft, Citrix will continue to develop WinFrame. However, it will always be based on the Windows NT 3.51 kernel, while Terminal Server is based on the NT 4.0 kernel. On the surface, this would seem to imply that, as customers upgrade, they will stop using Citrix products and move over to Microsoft. But according to Marchese, “For true enterprise users, you will see very few people implementing Terminal Server alone.” The reason lies in the differences between the protocols used by Citrix and Microsoft.

Terminal Server is built on the Remote Display Protocol (RDP), which is based on the International Telecommunications Union’s (ITU) T.120 protocol, a multichannel conferencing protocol currently used in the Microsoft NetMeeting conferencing software product.

RDP lacks many of the features included in Citrix ICA, or Independent Computing Architecture, which is the protocol used by Citrix WinFrame and MetaFrame. “You’ll see that RDP will become much more robust during the next year, but you can see there’s a big difference between RDP and ICA right now,” Marchese said. As a result, Citrix designed MetaFrame to sit on top of Terminal Server and provide the benefits of ICA to Terminal Server users.

Some of the differences between RDP and ICA are deliberate, Marchese said. “Citrix is focused on delivering WinFrame everywhere; Microsoft is focused on delivering Windows to all PCs. You’ll see Citrix ICA clients embedded in just about anything you can name by Christmastime,” he explained. For example, RDP works only under TCP/IP, while ICA works on many protocols. “If you’re running NetWare, you need to add MetaFrame,” Marchese said.

But ICA also has several features that would be useful to Windows-based networks that RDP just doesn’t support yet. ICA enables application publishing -- where the application is on one server but is available across the cluster -- session shadowing, anonymous users, audio support, and drive, printer and port mapping. MetaFrame can push new ICA clients to the desktop once one copy has been installed. MetaFrame also supports load balancing among multiple servers.

ICA is also built into Internet Explorer and is available as a free plug-in for Netscape. On the other hand, RDP doesn’t permit applications to run in a browser, Marchese points out.

This last difference may be a result not of the technological differences between RDP and ICA, but of the way Microsoft and Citrix have decided to license their products. Citrix offers concurrent user licensing with no per-user charge. WinFrame costs $5,995 for 15 concurrent users, and MetaFrame costs $4,995 per Terminal Server.

Terminal Server, on the other hand, is licensed on a per-seat basis. Each user must have an NT Workstation license, which costs $269 per client, and an NT Server client access license, which costs $39.95 per client. Terminal Server itself costs $1,129, the same price as NT Server.

As it releases future versions of Terminal Server, Microsoft will probably try to incorporate features from Citrix ICA into RDP and Terminal Server. According to Marchese, that just means that Citrix needs to add new features to maintain its lead, and to broaden ICA to new products outside the Microsoft sphere. But in the Windows world, for now, Marchese said, Microsoft and Citrix are “the best of partners, because one is not going to succeed without the other in this market.”