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Traditional CDNs focus on web acceleration. That is still their main revenue service. New CDNs have integrated media delivery services so they are optimized for live video streaming, high definition video and large asset delivery.
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 to optimize the delivery process. Optimization can take the form of reducing bandwidth costs, improving end-user performance, or increasing global availability of content.
The number of nodes and servers making up CDN varies, depending on the architecture, some reaching thousands of nodes with tens of thousands of servers on many remote PoPs. Others build a global network and have a small number of geographical PoPs.
Requests for content are 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 or fewest number of network seconds away from the requesting client, so as to optimize delivery across local networks. When optimizing for cost, locations that are least expensive may be chosen instead.
In a optimal scenario, these two goals tend to align, as servers that are close to the end user at the edge of the network may have an advantage in serving costs, perhaps because they are located within the same network as the end user. Traditional CDNs tend to compete based on the size and scale of their Edge Network deployments and generally follow a strategy of pushing the Edge Network closer to end users. The Edge Network is grown outward from the origin/s by further purchasing co-locations facilities, bandwidth and servers.
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