RG              UP                       CP             AAA
       |               |  Public Address Block  |               |
       |               |   Allocation Request   |               |
       |              1|<--------via Ci-------->|               |
       |               |  Public Address Block  |               |
       |               |   Allocation Reply     |               |
       |              2|---------via Ci-------->|               |
       |   Subscriber  |                        |               |
       | Access Request|        Subscriber      |               |
      3|-------------->|      Access Request    |               |
       |              4|----------via Si------->|               |
       |               |                        |      AAA      |
       |               |       Subscriber       |    Req/Rep    |
       |  Subscriber   |      Access Reply     5|<------------->|
       | Access Reply 6|<---------via Si--------|               |
      7|<--------------|                        |               |
       |               |  Create Subscriber     |               |
       |               |   Session Request      |               |
       |              8|<--------via Ci---------|               |
       |               |                        |               |
       |               |  Create Subscriber     |               |
       |               |   Session Response     |               |
       |               | (with NAT information) |               |
       |              9|---------via Ci-------->|               |
       |               |                        |   Accounting  |
       |               |                        |  with source  |
       |               |                        |   information |
       |               |                      10|<------------->|
       |               |                        |  Public IP +  |
       |               |                        |  Port Range   |
       |               |                        |  to Private IP|
       |               |                        |  Mapping      |
       |               |                        |               |