4.12.1.1 On-Demand Content Delivery
The On-Demand Content Delivery consists of the following steps:
The cache/proxy server checks whether the requested stream is in its local cache.
If the content is not in the cache, the cache/proxy opens a connection with the origin server, as specified in Request to Start Streaming Content, section 3.1.4.3. These steps are described in section 4.12.1.3.
The cache/proxy server checks whether the content in the local cache is stale. If the content is stale, the cache/proxy server revalidates the content.
If the content is still stale, the cache/proxy opens a connection with the origin server, as specified in Request to Start Streaming Content, section 3.1.4.3. These steps are described in section 4.12.1.3.
The cache/proxy server sends the Cache-Control header to the client.
The cache/proxy server sends $H and $D packets for the requested stream from its local cache to the client.
The cache/proxy server communicates any subscribed-to events (as indicated within the x-wms-event-subscription directive on the Cache-Control header) to the origin server, as specified in SendEvent Request, section 2.2.2.9.
The following illustration shows the sequencing that occurs when the client requests a file from a media server that is configured as a cache/proxy server.

Figure 17: On-demand content delivery