A content delivery network (CDN) is an interconnected system of computers on the Internet that provides Web content rapidly to numerous users by duplicating the content on multiple server s and directing the content to users based on proximity. CDNs are used by Internet service providers (ISPs) to deliver static or dynamic Web pages but the technology is especially well suited to streaming audio, video, and Internet television ( IPTV ) programming.
In a CDN, content exists in multiple copies on strategically dispersed servers. This is known as content replication. A large CDN can have thousands of servers, making it possible to provide identical content to many users efficiently and reliably even at times of maximum Internet traffic or during sudden demand "spikes." 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 node s between the server and the user) is dynamically determined. This optimizes the speed with which the content is delivered to that user.
The use of CDN technology has obvious economic advantages to enterprises who expect, or experience, large numbers of hits on their Web sites from locations all over the world. If dozens or hundreds of other users happen to select the same Web page or content simultaneously, the CDN sends the content to each of them without delay or time-out. Problems with excessive latency , as well as large variations in latency from moment to moment (which can cause annoying "jitter" in streaming audio and video), are minimized. The bandwidth each user "sees" is maximized. The difference is noticed most by users with high-speed Internet connections who often demand streaming content or large files.
Another advantage of CDN technology is content redundancy that provides a fail-safe feature and allows for graceful degradation in the event of damage to, or malfunction of, a part of the Internet. Even during a large-scale attack that disables many servers, content on a CDN will remain available to at least some users. Still another advantage of CDN technology is the fact that it inherently offers enhanced data backup, archiving, and storage capacity. This can benefit individuals and enterprises who rely on online data backup services.