Understanding The Components of a Streaming Media Network – Part 2

Streaming Servers
If content replication can be thought of as the backbone of the CDN, then the streaming servers are the muscle that makes it all happen. These machines deliver the content from disk, across the network to the client machine where it is viewed. A streaming server can either be an appliance, a piece of hardware specifically designed to stream content, or a regular commodity server installed with streaming software. Whether the server is an appliance or a commodity server, they all play an important part when it comes to the caching and replication of content across the CDN.

Caching content across a CDN can be proactive or passive. Proactive caching takes place by replicating content across the CDN before any client requests arrive. In contract, passive caching places a copy of the content onto the streaming server only when the client requests a file. It is them pulled from an origin server, placed on the streaming server and delivered to the client. Both methods have advantages and disadvantages. Proactive caching can take place late at night populating the servers when bandwidth is plentiful. Passive caching conserves bandwidth and disk space by populating content only as clients actually request the content. The objective is to have caches rich with content across the network at the minimum bandwidth expense required to distribute the content across the network.

Network Architecture still plays a role
A CDN works best when it is planned and designed carefully. The most complete packaged solution still needs to be tailored for the final installation. Among other criteria, the network architect needs to examine how the CDN will be used, what protocols will need to be supported and how much bandwidth is available at various points across the network. Some applications may not require a content management system while others may not require any replication or caching mechanisms. A large corporate installation may require more complex caching schemes allowing both proactive and passive caching of content and a high level of replication across the network. Then the various components can be selected and put together from the content management system down to the streaming servers.

CDN technology has come a long ways in the last few years. Improved video compression schemes have given higher resolution images at lower bit rates reducing network requirements. New caching and network protocols have allowed networks to support more and more viewers across existing network infrastructure. And the latest content management systems allow viewers to quickly author, broadcast and search through huge content libraries. It is easy to see that more can be done today than was possible just a few short years ago and the technology continues to make implementing a CDN even easier.