Corporate.Net Are NCs Really Worth The Price Of Admission? Terminal emulation is only the first step toward support of true legacy applications. Step two involves providing access to the mass of existing Windows applications. Vendors recognize the importance of this, and the typical strategy is to implement client capability that provides access to an application server capable of remote presentation of Windows applications. The most common approach is to implement some variant of Citrix Systems' WinFrame using a port of Citrix's Intelligent Console Architecture (ICA) protocol or an enhancement to the Citrix application server that allows for the display of Windows applications using the X protocol. In either case, you're limited to the Windows NT 3.51 interface until Citrix ports WinFrame to NT 4.0--a development that's bogged down in licensing negotiations between Citrix and Microsoft. Beyond the legacy applications, there's a clear need to support Java applets and an HTTP browser for access to Web-based applications. One obvious approach to Web support is to provide a local browser, but this may raise some red flags: You'll be dependent on your vendor to ensure that the latest version of the browser is available for that platform. Supporting a local browser also brings up the need for file-system access from the NC to store bookmarks and for use as cache space. Alternatively, you can provide access to a Windows-based browser via remote presentation from an application server. For Java, you have some of the same trade-offs, but it is probably a little safer to depend on an NC vendor to keep a Java virtual machine up to date than to keep a full-featured browser current. Be forewarned that Java applet performance may fall short of expectations if your standard is a Wintel system with a Just-In-Time Java compiler (see "NC Java Performance Not Up to Speed" at left). In addition to providing application capabilities, the NC must also offer a user interface that is simple and efficient. The approaches vary by ven dor. Alternatives include a standard Microsoft Windows interface, a browser-type interface, an X Window manager or some type of hybrid. It's also necessary to look at the system administration features. What exactly do you need to do to boot one of these devices? Are all applications stored on a server or does it make sense to load some common applications from local ROM? And what about the option of an intelligent local program cache that would update applications from a server one time and then load them from a secure local storage device? N Stands for Network Although many CIOs appreciate the potential savings of a network-oriented computing environment that minimizes systems administration functions, managers undoubtedly will have questions about the impact o f such a paradigm shift on design issues. Just as the speed of a hard disk or I/O bus can limit the performance of fat clients, it should come as no surprise that a slow network will have a significant negative effect on the performance of NCs. Unfortunately, the precise impact is difficult to assess in advance, since the availability of Java applications is fairly limited. It is safe to assume, however, that if your organization is planning to make a major migration to a thin-client computing environment, you'd better have the network capacity to support it. The steady drop in prices for Ethernet switches and high-speed LAN technologies makes the chase for more bandwidth economically feasible, but what about WAN environments where bandwidth is limited not by technology but by common carrier economics? These are often the kind of environments that have been slow to migrate from terminal-based systems, precisely because of the lack of bandwidth. You need an alternative to loading Java applications from a c entralized server to meet these demands. One alternative might be to implement easy-to-manage servers and local networks in those environments--an approach Sun is working toward with its Netra line of servers, which allow for manageme nt of the Unix environment from a Web browser. But easy to manage is a relative term and it's doubtful whether many environments capable of serving up Java applications qualify. Another alternative could be the implementation of intelligent caching systems that let applications be stored locally in nonvolatile RAM or on a protected disk drive on the thin clients. Only application updates would be transmitted across the WAN links, possibly in batch mode outside normal business hours. A third alternative is simply to use a thin-client technology that does not require significant bandwidth. The Citrix remote-presentation model, as implemented in the ICA protocol, is the best example. It's not exactly what most people think of when they talk about thin clients, but it wi ll get the job done when bandwidth is constrained and system administration is centralized. To download an Adobe Acrobat .pdf format version of the Network Computer features chart, click here. Network Computer Back-End Application Services

Internet RX by Chris Lewis The Tools to Smarten Up Your Web Site by Barry Nance Updated April 8, 1997