Introduction to Content Delivery Networks As rich media and streaming content becomes a more important element of a company’s online presence, small-to-medium sized businesses now not only have to think about which Web hosting provider to sign up with, but also how to best optimize the delivery of their content. Companies should consider a variety of factors when deciding on how they want to stream their rich media content.nnContent delivery network is a term used to describe an interconnected system of computers on the Internet that cooperate transparently to deliver Web content rapidly to numerous users by duplicating the content on multiple servers and directing the content to users based on proximity. nnIn general, CDN nodes are deployed in multiple locations and often over multiple backbones. This is known as content replication. These nodes cooperate with each other to satisfy requests for content by end users, transparently moving content behind the scenes to optimize the delivery process.nnThe details of the actual caching and delivery, however, vary from one CDN provider to the next. There are multi-network providers, like Akamai, that don’t necessarily own the network, but place their caches and servers on sites owned by access providers and other ISPs. There are also facilities-based providers, like large ISPs, that own their own facilities and have a national backbone using peering networks or partnerships. And then there are hybrid providers, like Digital Island, that have some facilities-based and some colocated CDN elements.nnSince the prospect of deploying a content delivery network would be prohibitively expensive to most companies, it is wiser for most businesses to offload the whole task to a third-party provider.nnCDN operator Akamai’s (akamai.com) EdgePlatform is one of the world’s largest distributed computing platforms and comprises of more than 20,000 secure servers deployed in 71 countries that relies on applied mathematics and algorithms to help solve congestion and vulnerability problems on the Internet. Akamai says these servers reside within approximately 1,000 of the world’s networks monitoring the Internet in real time gathering information about traffic, congestion and trouble spots. nnMirror Image (mirror-image.com) on the other hand specializes in caching technology and its Content Access Point network, which consists of 23 content access points, each with hundreds of servers, is designed to integrate into existing data centers and greatly accelerate the mirroring, caching and delivery of rich media content.nnAnd NaviSite (navisite.com) offers electronic file delivery, content streaming and Web acceleration services using HotRoute, its network-based proximity detection service to automatically select the nearest server or caching device to deliver requested content. The HotRoute technology determines the location of the end user and dynamically adjusts network paths between an end user and the closest content server to optimize data delivery from multiple data centers. NaviSite says the result is that content delivery is optimized.nnThe use of CDN technology can have economic advantages to enterprises that receive considerable traffic to their Web sites from locations all over the world. When a specific page, file or program is requested by a user, the server closest to that user, in terms of the minimum number of nodes between the server and the user, is determined, which optimizes the speed with which the content is delivered.nnIn addition, a large CDN can have thousands of servers, making it possible to provide identical content to many users efficiently, even at times of maximum Internet traffic or during sudden demand spikes. Still another advantage of CDN technology is the fact that it inherently offers enhanced data backup, archiving, and storage capacity, which can ultimately benefit individuals and enterprises that rely on online data backup services.