Generating a TCAP transaction requires the following steps:
Step |
Action |
1 |
Allocate a memory buffer large enough for the transaction request. A TCAP transaction buffer must be at least TCAP_MSG_SIZE bytes. |
2 |
Assign a unique user dialog ID (suDlgId) for the transaction (if it is the first request belonging to this transaction) and populate the transaction information data structure with the:
|
3 |
Initialize the transaction request with TCAPInitTrans. |
4 |
Add one or more components to the request with TCAPAddComp. Each invoke component must also have a unique invoke ID assigned within the current dialog ID. |
5 |
Send the transaction to the destination signaling point by calling TCAPTransRqst. |
The following examples show how the TCAP service implements a simple request and response transaction and a more complex conversational linked transaction. The ITU-T and ANSI variants are shown separately to clarify the conceptual differences.
A simple transaction consists of a transaction begin (ITU-T) or query with permission (ANSI) request with a single invoke component, followed by a single end (ITU-T) or response (ANSI) message with a single return result component. An example transaction is a request from a service switching point (SSP) to a service control point (SCP) to translate an 800 number into a subscriber directory number.
The following illustration shows the ANSI version of a simple transaction:
The following illustration shows the ITU-T version of a simple transaction:
A complicated conversational and linked transaction can occur as described in the following ANSI and ITU-T examples:
Stage |
Description |
1 |
A switching application issues an invoke on behalf of a subscriber to initiate a feature in a remote switch. |
2 |
The remote switch decides it does not have enough information to carry out the feature invocation. It responds with a new invoke (linked to the original invoke) to play an announcement to the subscriber and collect digits. |
3 |
The original switch collects the digits and returns them as the result to invoke #2. |
4 |
The remote switch now completes the feature invocation and returns the result to invoke #1. |
The following illustration shows the ANSI version of a conversational linked transaction:
The following illustration shows the ITU-T version of a conversational linked transaction: