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CDN nodes are deployed in multiple locations, often over multiple backbones. 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. Optimization can take the form of reducing bandwidth costs, improving end-user performance, or both.
The number of nodes and servers making up a CDN varies, depending on the architecture, some reaching thousands of nodes with tens of thousands of servers.
Requests for content are intelligently directed to nodes that are optimal in some way. When optimizing for performance, locations that can serve content quickly to the user may be chosen. This may be measured by choosing locations that are the fewest hops or fewest number of network seconds away from the requestor, so as to optimize delivery across local networks. When optimizing for cost, locations that are less expensive to serve from may be chosen instead. Often these two goals tend to align, as servers that are close to the end user sometimes have an advantage in serving costs, perhaps because they are located within the same network as the end user.
InterVU and Sandpiper Networks were pioneers in CDN's. Akamai Technologies is more well known. InterVU was purchased by Akamai in April 2000. Sandpiper was purchased by Exodus Communications who was purchased by Cable & Wireless and is now owned by Savvis.
U.S. Patent and Trademark Office issued U.S. Patent No. 6,108,703, "Global Hosting System,". The patent was granted to MIT in the names of Tom Leighton, Akamai's chief scientist, and Danny Lewin, Akamai's chief technology officer.
Digital Island, via its acquisition of Sandpiper Networks, was issued U.S. Patent No. 6,185,598, " Optimized network resource location", which was based on the work of chief system strategist David Farber and vice president Andrew Swart.