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Citrix NFuse: Program Neighborhood for the Web

NFuse is the collective name for a number of components that work together to deliver Program Neighborhood application-set support to users through a Web browser interface. Until the introduction of NFuse, Web-enabled applications were accessed through statically created links on a Web page. NFuse now allows an administrator to manage a user's access to applications just as if the user were running Program Neighborhood directly from the desktop, using the Win32 or Java ICA clients.

When NFuse has been implemented on a Web server, a user is first presented with a logon page, which requires him or her to provide authentication credentials for a Windows domain. These credentials are then used by NFuse to determine which application set access the user has and dynamically generate the HTML page containing links to the applications within this application set.


Warning - The logon information communicated between the Web browser and the Web server (running NFuse) is standard HTTP. Unless the HTTP has been encrypted with SSL (Secure Sockets Layer), the information will be transmitted in clear text. In an Internet implementation, this is a definite security concern. An excellent document on this topic is available at the Citrix Web site: "Security Guidelines for NFuse 1.0." Before implementing NFuse, I highly recommend that you review this document to ensure that you have a clear understanding of the possible security concerns in NFuse. This document can be found at the following address:

ftp.citrix.com/doclib/NfuseSecurity.pdf


Figure 15.4 shows the updated components and steps involved in connecting to a Web-enabled application with NFuse. This is an update of Figure 15.1.

  1. The user requests the initial Web page from the server.

  2. The logon page is displayed within the user's Web browser (see Figure 15.5).

Figure 15.4
MetaFrame Web computing components and the steps to launch an application when using NFuse.

Figure 15.5
An NFuse logon Web page.

  1. After the necessary information is entered (user ID, password, and possibly the domain), the user's Web browser sends the credentials back to the Web server.

  2. The NFuse Java objects running on the Web server pass the information to a corresponding NFuse service running on a MetaFrame server.

  3. The NFuse service takes the information and communicates with the Program Neighborhood service on that MetaFrame server to get the necessary application-set information. This information is then passed by the NFuse service back to the NFuse Java objects, which generate the corresponding HTML page containing links to the applications in the set. The links on the page point to ICA template files that, when clicked, will provide the information to establish the connection to the appropriate application.

  4. The generated HTML page is returned to the client's Web browser to be displayed locally. Figure 15.6 shows an example.

  5. After the desired application is clicked, the request for the corresponding ICA is sent back to the Web server.

  6. NFuse replaces the substitution tags in the ICA file with the necessary information specific to the user, and the file is then passed back to the client.

  7. Based on the information in the ICA file, the ICA client connects to the appropriate published application within the MetaFrame environment.

  8. A regular MetaFrame published-application session is opened between the client and the server.

Figure 15.6
An NFuse-generated application set in a Web page.


Author's Note - The MetaFrame server that communicates with the NFuse objects on the Web server in steps 4 and 5 doesn't have to be the same server with which the user establishes the connection in step 9. The NFuse service simply acts as a liaison between the Citrix Program Neighborhood service running on the MetaFrame server and the NFuse objects on the Web server.


NFuse provides an application programming interface (API) to the Java objects, allowing experienced Web developers to have more control over the construction and behavior of the NFuse Web site. Using the API, you can manipulate the contents of both the HTML pages and the ICA files that your users may access. Currently, the NFuse API is accessible via the following APIs:

  • Microsoft's Active Server Pages (ASP)

  • Sun's JavaServer pages

  • Citrix's proprietary HTML substitution tags

  • Custom-developed Java server applets (servlets)


Author's Note - Citrix's substitution tags are available for Webmasters who are unfamiliar with Web server scripting. The use of these tags also requires a Citrix-provided Java servlet or ASP support files in order to perform the desired NFuse actions.


To implement NFuse, you must perform some configuration steps on each of the components shown in Figure 15.4 (the client browser, the Web server, and the MetaFrame server). The following sections look at each of these areas in turn and discuss the configuration requirements for both a standard Web-enabled application environment and an NFuse environment.

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