Content Distribution and Management

The Cisco Content Distribution Manager can be used to manage how content is distributed to content engines, and to control other content engine settings.

Key Point

Cisco defines three types of content: on-demand, pre-positioned, and live.

On-demand content is what the content engines store as a result of users' requests, as described in the "Content Caches and Content Engines" section, earlier in this chapter. Content engines can check with the origin server to see whether on-demand content is up to date. This occurs, for example, when the content expires (as specified by the server), when a user explicitly requests it (such as when the user clicks the Reload button in his browser), or when configurable timers set on the content engine expire. If the content has changed, the content engine caches the updated content from the server.

Pre-positioned content is that which has been retrieved and distributed through a network of content engines; the network administrator configures the Content Distribution Manager to pre-position this bandwidth-intensive content (typically during off-peak hours) so that it will be available upon users' requests. Some terminology related to pre-positioned content is as follows:^[4]

• Channel A set of content from a single website and the configuration that defines how the content is to be acquired, distributed, and stored. Content engines are assigned to a channel so that they can handle requests for this content.

• Root content engine The content engine that is designated to download a channel's content from the origin server and forward it to the other content engines that are assigned to the channel.

• Manifest file Specifies the location from which the root content engine should fetch the pre-positioned content objects and the frequency with which the content engine should check for updates.

Note

Manifest files define content accessed through Hypertext Transfer Protocol (HTTP), Secure HTTP (HTTPS), and File Transfer Protocol (FTP). Thus, only these file types can be pre-positioned.

Live content is a stream of content, such as a CEO's annual message to employees, that is being broadcast and that is to be relayed by the content engines to the users according to specific policies (such as maximum bit rate and bandwidth). Live content is not associated with a manifest file but rather with a program file. The program file describes attributes of the program, such as the start and end time and the server to be used.