Software Distribution Channels

After Internet Explorer is installed, you can provide future software updates over the Internet or intranet by using software distribution channels, which are Web sites dedicated to software distribution. You can make a software update, such as a new custom package of Internet Explorer, available on your Internet or intranet server and then use a software distribution channel to distribute the update to channel subscribers. By default, Internet Explorer also notifies users when new browser releases and updates are available. You can use software distribution channels to control how often Internet Explorer checks for this updated information.

A Channel Definition Format (.cdf) file contains the software distribution channel settings, including the files to be updated and the daily, weekly, or monthly schedule for updating them on subscribers' computers. Each time the channel is updated, the latest version of the .cdf file is downloaded to subscribers' computers.

When the Open Software Distribution (OSD) section of the .cdf file indicates that a new version of the software is available, subscribers' computers can be instructed to do the following:

• Install the updates automatically and notify users that the updates were made.

• Download the installation files to users' hard disks, notify users, and provide instructions and links so that users can run the installation program manually.

• Automatically notify users by e-mail when new software updates are available. Provide instructions and links so that users can download the software manually.

Configuring Software Distribution Channels

To configure software distribution channels, you must complete the following tasks:

• Create the Web content to support the channels.

• Create the .cdf files.

• Create the software distribution packages.

• Configure the Web servers to support the channels.

After you configure software distribution channels on your computer, you can import them into your custom browser packages by using the Internet Explorer Customization wizard. For more information about using the Internet Explorer Customization wizard to import channels, see Chapter 15 , "Running the Internet Explorer Customization Wizard."

If automatic browser configuration is enabled on your users' computers, you can use the IEAK Profile Manager to add or delete software distribution channels after you distribute your custom packages.

Creating Web Content

You can create the following Web content, which is included with each .cdf file:

• Notification Web pages - A notification Web page is used to describe the software updates and typically provides users with links to the individual notification Web pages for more details. This summary page can be an HTML file or an Active Server Page (.asp) file.
  The notification page is specified in the .cdf file for the CHANNEL element HREF attribute - for example, HREF="https:// Web server / filename .htm," where filename is the name of the summary page. When users select the channel on the Channel bar or on the Favorites menu, the summary page appears on the right side of the browser window. If USAGE VALUE="E-mail" is specified, a notification page is sent by e-mail to users who have e-mail notification enabled.

• Optional Channel bar graphic images - You can create two optional graphic images in either .gif or .jpg format for the desktop Channel bar logo and the browser Channel bar logo. You can also create an optional .ico image, which appears to the left of each item in the Channel bar hierarchy.
  The following list describes the specifications for these images:

  • Desktop Channel bar logo - 32 pixels high by 80 pixels wide with a black background.
    .cdf file entry: <LOGO HREF=" filename .gif" STYLE="Image">

  • Browser Channel bar logo - 32 pixels high by 194 pixels wide with a color background.
    .cdf file entry: <LOGO HREF=" filename .gif" STYLE="Image-Wide">

  • Browser Channel bar icon - 16 pixels high by 16 pixels wide, with different images, colors, or shapes to indicate whether an item is a container for other items or is actual content.
    .cdf file entry: <LOGO HREF=" filename .ico" STYLE="Icon">

  You can use the Channel bar logo for the browser window logo, and the extra area will be filled in with the same color as the rightmost top pixel. Animated .gif files are not supported. Images are displayed with a fixed 256-color palette regardless of the monitor color depth. Therefore, you should use the Windows halftone palette.
  Note The Channel bar provides users with a 14-pixel-high by 14-pixel-wide red gleam to indicate when channel content has been updated. The gleam is a triangular overlay applied to the upper-left corner of the Channel bar logos. When you create Channel bar logos, do not place critical text or visual elements in this area. A 7-pixel-high by 7-pixel-wide gleam is also applied to the upper-left corner of icons to indicate when item content has been updated.

Creating the .cdf Files

Create a .cdf file for each software distribution channel that will be installed on users' computers. When you deploy custom packages of Internet Explorer to your users' computers, you should have enough preconfigured software distribution channels to meet your organization's needs.

Your .cdf file should include the schedule for updates. Using the SCHEDULE element in the .cdf file, you can specify daily, weekly, or monthly update frequencies as well as the time of day and the interval during which updates can occur. Assigning user groups to different schedules, such as alternating days or weeks, can help distribute network load.

You should schedule software downloads for times of low network traffic, especially for large software packages. To avoid a heavy load on your Web servers when all subscribers update the software distribution channel, you should specify that Internet Explorer updates the channel at random times.

Creating Software Distribution Packages

Create the software distribution packages you need to support your software distribution channels. Software distribution packages contain files that are compressed by using the .cab compression format. Each .cab file contains an .inf file that specifies how the .cab file should be installed. To locate the .cab files for the update, Setup reads the information in the IE5Sites.dat file.

Important You should digitally sign your .cab and .exe files before distributing software updates to users' computers. Digital signatures identify the source of programs and guarantee that the code hasn't changed since it was signed. Depending on how users' browser security levels are configured, users could be prevented from downloading .cab and .exe files that aren't signed. For more information about signing your files, see Chapter 12 , "Preparing for the IEAK."

Configuring Web Servers

You should configure enough Web servers to support your software distribution channels, as well as the volume of software you distribute. You can include multiple channels on each Web server.

To configure Web servers to support your distribution channels, complete the following tasks:

1. Install Web server software, such as Microsoft Internet Information Server (IIS).

2. Configure file systems for each software distribution channel.

3. Copy the notification pages, graphics files, and software distribution packages to your Web servers.

For more information about configuring Web servers, see your Web server documentation.

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