Important
Be aware, Mobicents ISUP Stack is subject to changes as it is under active development!
Note
SS7 design allows ISUP to be used on top of SCCP, however currently Mobicents ISUP does not support this use case.
Note
For messages definition please refer to source or Q.763.
ISUP specification declares only messages and parameters to pass information about trunks and circuits setup. Mobicents ISUP introduces notion of transactions. Transaction groups messages which logically belong to single interaction (like associating circuit to call or releasing circuit). Server transaction is used as reference for incoming request. It provides means of sending answer back to originating peer. Client transaction is used as reference for outgoing requests. It provides means of sending request to remote peer. Also incoming answers will be delivered on client transaction which sent it.
Depending on type of action and messages involved, life time of transaction varies. Diagram below depicts transaction scope:
Note
Depending on transaction state machine messages #2 and #3 may not be present.
Following transactions types are defined by Mobicents ISUP :
Table 3.1. Transaction types
| Name | Initial message | Intermediate messages | Final message |
|---|---|---|---|
| IAM | IAM | ACM | ANM |
| REL | REL | RLC | |
| CGB | CGB | CGBA | |
| GRS | GRS | GRA | |
| CGU | CGU | CGUA | |
| RSC | RSC | ||
| UBL | UBL | UBA |
Transactions are either terminated on receiving or sending final response or when certain time elapses without answer. In both cases stack user is notified that transaction is no longer valid.