This figure illustrates the three diameter-request processing extension points; Request-Received extension, Pre-OCS extension, and Post-OCS extension. This figure shows that the Request-Received extension processes the CCR before any rating, discounting, or alteration logic has been invoked and also it allows immediate response (CCA) that bypasses the OCS completely. This figure shows that the Pre-OCS extension processes the ECE Usage Request payload before any rating, discounting, or alteration logic has been invoked. This figure shows that the Post-OCS extension processes the CCA before it is returned to the diameter client.