Lumen help

Frequently Asked Questions

CDN Load Balancer

Calculating the Global CDN score

 

CDN Load Balancer bases its selection and switching decisions on a "global" score. In practice,

Global score = business score * QoS score

The global score is based on:

  1. A business score provided by the broadcaster: This business score reflects how heavily commit-based or business-based inputs should be evaluated; it can take integer values of 1 to 100.

  2. A Quality of Service score: At the beginning  of the session, the QoS score is calculated from the metrics CDN Load Balancer gathers from across the broadcaster's user base. During the session, the QoS score is the quality perceived by the end-user device during the session: bandwidth, time to first byte, and error rate.

After the beginning of the session, quality is calculated locally. This prevents CDN Load balancer from becoming a single point of failure; during the session, CDN Load Balancer only connects to the backend to send quality statistics to be ued in initial scoring for future sessions.

Practical Example

 

A broadcaster uses three CDNs for delivery on the West Coat of the US. CDN A is its primary delivery network with CDN B and CDN C as backups. It assigns each CDN the following business scores:

 

CDN A: 8     CDN B: 4        CDN C: 2       

 

In this case, CDN A will be chosen except when CDN B;s quality of service is more than twice as high as that privded by CDN A. In practice, this means significantly lower bandwidth or prevalent errors. By the same token, CDN C will not be used unless its QoS is more than twice as high as CDN B, and CDN A is not available.

 

The following table provides a non-exhaustive list of compatible workflows.

Encoding
Security
CDN
HTML5 Player
Mobile
SSAI
Analytics
AWS Elemental
Widevine
Lumen
Vimeo
Dash.js
Android - Exoplayer
Yospace
Conviva
Unified Streaming
Playready
AWS
Bitmovin
Hls.js
iOS, tPadOS, tvOS - AVPlayer
Google DAI
Youbora
Bitmovin
Fairplay
Fastly
Kaltura
Video.js
  Ad Insertion Platform
Luna
Wowza
BuyDRM
Akamai
Brightcove
Shaka Player
  AWS Media Tailor
Bitmovin
Anevia
AES 128
Edgecast
JW Player
Flowplayer
    Mux
Mediakind
  Limelight
Theoplayer
Clappr
    Cedexis
encoding.com
  CDN Networks
Castlabs
      Google
ffMPEG
  China Cache
Comcast
      Fastly
VP9/HEVC/AV1
  Cloudflare
Azure Media Player
       

The business score for a CDN can be changed at any moment and will be reflected on new and already running sessions less than a minute after you update in your dashboard. This can allow you to modify CDN priority if you reach one of your CDN commits during the month.