,--------------------------------------------------------------------------,
|   Fixed    PSTN/ISDN  Gateway  Home Location  PSTN/ISDN          Mobile  |
| Subscriber exchange     MSC      Register     exchange  MSC/VLR  Station |
|     |          |         |          |          |          |          |   |
|     |--------->| MSISDN  |          |          |          |          |   |
|     | MSISDN   |-------->|  MSISDN  |          |          |          |   |  
|     |          |         |- - - - ->|          |          |          |   |
|     |          |         |   MSRN   |          |          |          |   |
|     |          |         |<- - - - -|          |          |          |   |
|     |          |         |   MSRN   |          |          |          |   |
|     |          |         |-------------------->|  MSRN    |          |   |
|     |          |         |          |          |--------->|  TMSI    |   |
|     |          |         |          |          |          |--------->|   |
|     |        ,---,     ,---,        |        ,---,      ,---,        |   |
|     |        | S |     | S |        |        | S |      | S |        |   |
|              `---'     `---'                 `---'      `---'            |
|   ,---,                                                                  |
|   | S | indicates a switching node.                                      |
|   `---'                                                                  |
`--------------------------------------------------------------------------'