This layer includes origin servers (usually co-located), reverse proxies, and load balancer(s).
The origin server receives the fragments from the packager and delivers them to players through a CDN.
The origin server can store the fragments for a while. In this case, it modifies the entries in the manifest file to indicate the fragments that are available with it and the corresponding metadata. You can also use Primetime Origin server to convert the packaged content from HDS to HLS format just-in-time while delivering it to HLS clients.
The origin service layer also includes a reverse proxy. It is a stateless server that serves as an endpoint for player requests. It can cache the response of HTTP GET request to reduce the load on the origin server.
Reverse proxy implements failover logic to ensure high availability of the packaged content. For example it uses the 503-failover scheme to serve a fragment request if it is available with any origin server.
A load balancer distributes the client load between the reverse proxies. It must have a public IP address that is used to construct rendition stream URLs, which are listed in the top-level manifest.