What Are Content Download Jobs?
ISA Server extends caching performance by enabling content download jobs. By monitoring and analyzing Internet access, you can determine which Web content is most likely to be requested by internal clients. You can then create a content download job to download the Web content to the ISA Server cache before any client requests the object. Content download jobs allow you to schedule content for download at a specific time or at recurring times.
Benefits of Using Content Download Jobs
The main reasons for using content download jobs are to improve Internet access performance and decrease the use of bandwidth to the Internet. There are several possible scenarios in which content download jobs can provide this functionality. For example, you can create a content download job at a branch office ISA Server so that the entire main-office intranet site is downloaded from the main office Web server. The content download job can be configured to take place during non-working hours so that the branch-office link to the main office is not used for the download during working
hours. When branch-office users arrive at the office, the main-office Web site’s content is stored in the branch-office cache. Branch office users can quickly download even large files from cache, while freeing the branch-office link to the main office during work hours for other business-related network activity.
You can also use content download jobs to update information from Internet Web sites. For example, users may frequently request a price list from the Web site of a business partner. You can configure a scheduled content download so that ISA Server retrieves the price list each night. By using a scheduled content download, the most recent version of the price list will be in the cache each morning.
You can also use scheduled content downloads to ensure that Web content is always available to users, even when they cannot connect to the Internet. For example, users may need constant access to a particular Web site, and any disruption in that access may disrupt business processes. In this case, you can configure ISA Server to download the content and provide that content for users even when the Internet connection is not available.
Scheduled download jobs can also be useful in reverse proxy scenarios. For example, if you are publishing an internal Web site that is modified every night, you can schedule a content download job every morning so that the new Web content is stored in the ISA Server cache. The ISA Server computer then does not need to access the internal Web site to provide the content to clients.
When you enable content download jobs, the actions listed in Figure 6-2 occur:
1. You create a content download job that specifies Web content to be retrieved from the Internet and when content retrieval occurs.
2. At the scheduled time, ISA Server uses a background process to retrieve the content from the Web server. The content is stored in the ISA Server cache based on the settings specified by the content download job.
3. A user on the internal network sends a request for the Web content to the ISA Server computer. The Firewall service passes the request to the Web proxy filter.
4. The ISA Server Web proxy filter determines that the content is in the Web cache, so ISA Server retrieves the content from the cache.
5. Content retrieved from cache is returned to the requesting user.
