RG            UP              CP         AAA
     |             |   L3 access    |          |
     |             |  control list  |          |
     |            1|<----via Ci-----|          |
     |    User     |                |          |
     |   traffic   |                |          |
    2|------------>|                |          |
     |             |  User traffic  |          |
     |            3|-----via Si---->|          |
     |             |                |   AAA    |
     |             |                |  Req/Rep |
     |             |               4|<-------->|
     |             |                |          |
     |             | Create Session |          |
     |             |    Request     |          |
     |            5|<----via Ci-----|          |
     |             | Create Session |          |
     |             |    Response    |          |
     |            6|----via Ci----->|          |
     |             |                |          |