More in-depth diagram

1. Subscriber makes a content (subscription) request to CPA
2. CPA checks with CP regarding request validity
   • Invalid request: CPA passes CP's report to the subscriber
3. CPA sends a confirmation code to subscriber
4. Subscriber sends the code to CPA
   • Incorrect code: CPA sends a note to subscriber (can retry)
5. CPA makes the content request to CP
   

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6. CP sends the content to CPA
7. CPA sends the content to subscriber
8. CPA sends the delivery report to CP
   

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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.