Content Delivery Network (CDN)
A content delivery network, or content distribution network, is a geographically [distributed] network of [proxy-server] and their data centers. The goal is to provide high availability and performance by distributing the service spatially relative to end users.
Requests for content are typically algorithmically directed to nodes that are optimal in some way. When optimizing for performance, locations that are best for serving content to the user may be chosen. This may be measured by choosing locations that are the fewest hops, the lowest number of network seconds away from the requesting client, or the highest availability in terms of server performance (both current and historical), so as to optimize delivery across local networks. When optimizing for cost, locations that are least expensive may be chosen instead. In an optimal scenario, these two goals tend to align, as [edge-server] that are close to the end user at the edge of the network may have an advantage in performance or cost.