CMCD in DVB-I (Commercial Requirements)

Introduction

Common Media Client Data (CMCD, CTA 5004) defines communication from a media player in a client device to a CDN. Some of the features can be described as follows.

• Media player clients can convey information to Content Delivery Networks (CDNs) with each object request. This information can be useful in log analysis, QoS monitoring and delivery optimization.
  • Session identification allows thousands of individual server log lines to be interpreted as a single user session, leading to a clearer picture of end-user quality of service.
  • Bitrate, buffer and segment signalling allow CDNs to fine-tune and optimize their midgress traffic by intelligently reacting to the time constraints implicit in each request.
  • Prefetch hints allow CDNs to have content ready at the edge ahead of the client request, improving delivery performance.
  • Buffer starvation flags allow performance problems across a multi-CDN delivery surface to be identified in real-time.
• In combination, this transferred data should improve the quality of service offered by CDNs, which in turn will improve the quality of experience enjoyed by consumers.
• Common Data metrics for different protocols and players are defined.

CMCD is a simple, focussed specification created after more complex specifications (e.g. CTA-2066) failed to get industry acceptance. In addition, the metrics reporting mechanisms defined in TS 103 285 (DVB-DASH) also failed to get significant adoption as the current solution introduces additional request overhead, which can be costly and inefficient. In CMCD reporting metrics are integrated with the requests that are already made by a player, which is more efficient.

Scope

The scope of this document is to enable the optional use of CMCD with DVB-I services presented by the ‘native’ DASH player, i.e. the one built-in to a DVB-I client.