Structure of simple CPA content subscription:

More in-depth diagram

  1. Subscriber makes a content (subscription) request to CPA
  2. CPA makes the content request to CP
  3. CP sends the content to CPA
  4. CPA sends the content to subscriber
  5. CPA sends the delivery report to CP

The separated items are repeated during the subscription; note that there's a CPA side limit on the repeat number, so the last message could be an invitation to continue the subscription.