CDN Architectures Demystified

TR 068

With streaming platforms gaining in popularity, PSMs are expending effort to create their own “Over-The-Top" or “Direct-To-Consumer" offerings.

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The breadth of the content catalogue, the scale of the viewership and its expectation of a high-quality experience pose technical distribution challenges. To overcome these challenges, complex distribution chains are constructed. This report gives an insight into the architectures of Content Delivery Networks (CDNs) used to distribute streaming media over IP networks, as well as the choices that need to be made when choosing amongst distribution solutions.

The report introduces the concept of a CDN (Content Delivery network), explaining the differences between commercial and private CDNs. The multi-CDN architecture is then introduced, and the different strategies needed to balance traffic between them are laid out. There follows the description of some value-added CDN services that may be offered on top of the main data distribution service and pricing models and cost considerations are addressed.  To round up the report, standardisation activities related to CDN services are reviewed and a conclusion is drawn.

Keywords: CDN, Content Delivery Network, Distribution, Traffic pattern, Congestion, Network Saturation, Caching, Pop, Point of Presence, MPEG-DASH, HLS.