content delivery network (Internet) (CDN)
A Content Delivery Network(CDN) is a Value Added Network( VAN) of an Internet Service Provider( ISP) or a carrier that contains intelligent routers and load balancing facilities at strategic locations. The purpose of a CDN is to deliver content close to users so that they can access the desired content as quickly as possible. A Content Delivery Network can be configured over the Internet, but it can also be configured over a completely independent core network.
The structure of CDN networks
A Content Delivery Network is composed of centrally managed cache and storage systems that are deployed in a distributed manner across a network. The purpose of distribution is to bring Web content closer to the user, use available bandwidth more efficiently, and accelerate data access. Conceptually, a content delivery network consists of various components such as the nodes in which the data is stored and which ensure the distribution of the content as well as the integration of the services, the storage and delivery nodes. This distribution is done via the Internet Content Adaption Protocol( ICAP).
Another component is the central controller/manager, which is responsible for content storage, administration, user account and performance monitoring. In addition, there is the Request Manager, which distributes content requests from users to the next available Storage Node.
The configuration of CDN networks
In terms of configuration, there are three basic structures for CDN networks: the edge distribution, the edge hierarchy and thehub and spoke. The Edge Distribution is suitable for small CDNs. Here, content is transferred from a central storage system to edge devices or to points of presence( PoP), where it is stored for faster access. In Edge Hierarchy, which is suitable for larger CDN network configurations, hub caches are placed downstream of the central storage system to handle content distribution. And in the Hub and Spoke CDN configuration, which can be deployed in global enterprises, content from the central storage system is offloaded to any number of decentralized storage systems. The content is stored by the hub systems in cache systems called spokes.
CDNs must provide content for all types of end devices. These can be mobile devices such as smartphones, cell phones, handhelds, tablets, or PDAs, but also computers or personal computers.