Web Application Video Ecosystem - Common Media Server Data (CTA-5006)
Adaptive streaming of segmented media is enabled by media players requesting media objects from servers. These servers are arranged in a hierarchy starting with the origin server, which holds the authoritative copy of the content requested by user agents and other servers. Outbound responses traverse a series of mid-tier and edge intermediaries, known collectively as Content Distribution Networks (CDNs). The origin servers know information about the media object which the CDN servers do not. For example, they may know the format, the duration and the encoded bitrate of a media object. The edge servers in turn know information unavailable to the origin or players. For example, they may know the throughput available in the next network hop, or the cache status of the various objects.
The CMSD specification defines a standard means by which every media server (intermediate and origin) can communicate data with each media object response and have it received and processed consistently by every intermediary and player, for the purpose of improving the efficiency and performance of distribution and ultimately the quality of experience enjoyed by users.