A key benefit of server-based computing is that with minimal effort, you can use the technology to provide seamless interoperability. For example, instead of running terminal emulation software to make one platform act like another, you can run display software on a client machine and display all graphical output from an application that's running on the terminal server. This scenario probably isn't news to you—a lot of people use terminal services to run Windows applications on non-Windows platforms. But what might be news to you is that you can employ the same technique to get UNIX applications to non-UNIX platforms without an X Window System (X) client. In addition, Citrix MetaFrame's ICA can make UNIX and Windows applications available from the same interface and enable you to copy data between the two kinds of applications. Let's examine how to set up MetaFrame for Windows and MetaFrame for UNIX to present Windows and UNIX applications from one UI, taking into account the challenges of licensing and configuring logons. I assume that you've already installed MetaFrame and Citrix NFuse, which lets you deploy traditional client/server applications over the Web, and are prepared to publish applications.
Why MetaFrame for UNIX?
Citrix originally developed its multiuser product for the Windows platform, but MetaFrame has been available for UNIX since 2000. Like MetaFrame for Windows, MetaFrame for UNIX uses the ICA protocol to display applications on user desktops.
UNIX has supported multiple users for decades, enabling any computer with an X client to display applications running on a separate UNIX machine. So why do you need more software to achieve something that you can do already? The simple answer is that ICA lets you do something that you can't do with X.
Until recently, the ICA display environment wasn't as rich as X's and its more powerful graphical rendering machine. However, ICA has its advantages. First, the ICA client component requires almost no configuration, regardless of the application you're running on it. In contrast, X emulation packages for non-UNIX clients often require a significant amount of configuration and tuning to work optimally. Second, the ICA protocol displays objects extremely well over low-bandwidth connections, whereas X requires too much bandwidth to work effectively over dial-up connections and most WAN connections. Third, ICA supports session shadowing, which lets one person see and interact with another's terminal session. Finally, ICA completely isolates the display component of an application from the application's execution, so you can disconnect one computer from a running terminal session, then reconnect to the session from another computer to pick up where you left off. Meanwhile, the application on the server retains the session data in memory. This feature alone has made MetaFrame for UNIX popular among UNIX developers because it lets them end a session at work and reconnect to it from home.
ICA's simpler software on the display device and lower bandwidth requirement result from differences in the way X and ICA work. In X, the display device is considered the server, and the host running the application is considered the client. This arrangement might seem backward at first glance, but if you think about it, it makes sense. The device that displays the application is a display server (i.e., the graphics rendering system). Graphical primitives travel from the UNIX application host (the client) to the display device (the server) for local rendering and display. In ICA, the display device is the client and the application host is the server. The server renders the graphics, then transmits them over the wire to the client for display.
MetaFrame for UNIX isn't as mature a product as MetaFrame for Windows. MetaFrame for UNIX 1.1 (the current version) roughly corresponds to MetaFrame for Windows 1.8, and MetaFrame XP—essentially, 2.0—is the current version. MetaFrame XP for Windows has some scalability and printer drivermanagement tools that earlier versions lack and implements the new Independent Management Architecture (IMA).
MetaFrame for UNIX doesn't support the concept of a server farm. You can't make MetaFrame for UNIX servers part of a MetaFrame for Windows server farm, nor can you place the MetaFrame for UNIX servers into a farm of their own. MetaFrame for UNIX does let you publish applications from MetaFrame for UNIX servers; define access for users, groups, and folders; and perform load balancing. Citrix says that MetaFrame XP for Windows' graphical Java console will be available for UNIX "in the future," but you must perform all MetaFrame for UNIX configuration from a command line until then. However, MetaFrame for UNIX is on the same development track as MetaFrame for Windows, and Citrix designed the two products to work together. In fact, one reason why MetaFrame XP for Windows has a Java-based management console (instead of a Microsoft Management Console—MMC—snap-in) is so that you can use the same administrative tools for the two products. (That said, the speed of using the command line might make you wish you could publish applications from the command line with MetaFrame for Windows.)
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Corrections to this Article:
We inadvertently omitted Stephen Greenberg's name as coauthor of "Windows and UNIX on the Desktop" (May 2003, http://www.winnetmag.com, InstantDoc ID 38495). Stephen Greenberg is the founder and president of Thin Client Computing in Scottsdale, Arizona. We regret any inconvenience this error might have caused.
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