|
|
|
| Signalling protocols for end-to-end |
||
| connection |
||
| User
interface |
| PSTN
Network |
| User
interface |
| SS7 |
| Q.931 |
| Q.931 |
| ISUP |
| ISUP |
| Q.931 |
| Q.931 |
| DSS1 |
| DSS1 |
| MTP 3 |
| MTP 3 |
| Q.921 |
| Q.921 |
| MTP 2 |
| MTP 2 |
| Q.921 |
| Q.921 |
| I.430 |
| I.430 |
| MTP 1 |
| MTP 1 |
| I.430 |
| I.430 |
| contains
the signalling messages for call control |