The TCAP (Transaction Capabilities Application Part) layer adds transaction services onto the connectionless data transfer service provided by SCCP. Transactions in the SS7 network are typically database queries and responses or requests to activate services in remote switching points.
TCAP can be configured for either ANSI (see ANSI T1.114) or ITU-T (see Q.771 - Q.775) operation, on a per-application basis. Use of ITU-T TCAP on top of an ANSI MTP/SCCP stack is fully supported. TCAP requires using SCCP and MTP.
TCAP implements services through the configuration of the following entities:
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Entity |
Description |
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Define the resource allocation for the TCAP layer: maximum number of user SAPs, simultaneous dialogs, and outstanding invokes. | |
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Define the interface between a TCAP user application and the TCAP layer. One user SAP is defined for each application using the TCAP layer services. A user SAP is associated with a single subsystem number and protocol variant (ANSI-88, ANSI-92, ANSI-96, ITU-88, ITU-92, or ITU-97). Each TCAP user SAP maps directly to a SCCP user SAP in the SCCP configuration file, although not all SCCP SAPs must be assigned to TCAP applications. Some applications can access the SCCP layer directly. Refer to the SCCP configuration overview for more information. |
The following illustration shows the relationship between TCAP user SAPs and SCCP user SAPs: