9.1 Introduction to the TCAP Layer

9.2 The TCAP Configuration File

9.3 TCAP Configuration Reference

9.3.1 General Parameters Definition

9.3.2 User Service Access Point (SAP) Definitions

9.1 Introduction to the TCAP Layer

The SS7 TCAP layer adds transaction services onto the connectionless data transfer service provided by the SCCP layer. Transactions in the SS7 network are typically database queries/responses or requests to activate services in remote switching points.

The SS7 TCAP layer 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. Use of the TCAP layer requires use (and proper configuration of) the SCCP and MTP layers.

The TCAP layer configuration consists of general configuration parameters and TCAP User Service Access Points (SAPs). The general configuration parameters define the resource allocation for the TCAP layer: maximum number of user SAPs, maximum number of simultaneous dialogs, and maximum number of outstanding invokes.

User SAPs 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 (see Chapter 7), although not all SCCP SAPs must be assigned to TCAP applications; some applications may access the SCCP layer directly.

The relationship between TCAP user SAPs and SCCP user SAPs is illustrated in Figure 11.

Figure 11. TCAP Service Access Points

9.2 The TCAP Configuration File

The TCAP distribution software contains an application (tcapcfg) which reads a text configuration file and downloads it to the TCAP layer on the TX board, typically as part of the boot sequence. A sample configuration file, tcapcpn.cfg is included with the distribution software and is shown below.

Note: Not all configurable parameters need be specified in the configuration file. Most will default to reasonable values if not specified.

#
# Sample TCAP configuration file for the following configuration
#
#       General:
#           4 user APPs max
#           200 max simultaneous dialogs
#           200 max simultaneous invokes
#           all others general defaults
# General Configuration Section
TCAP_ALARM_LEVEL      1       # standard alarms
MAX_TCAP_USERS        4       # Max TCAP user applications
MAX_TCAP_DIALOGS      200     # Max TCAP simultaneous dialogs
MAX_TCAP_INVOKES      200     # Max TCAP simultaneous invokes
END
#
# User SAP configuration for 1st application
#
USER_SAP              0       # Sap number start at 0
SWITCH_TYPE           ANSI92  # one of ITU92, ITU88, ANSI92, ANSI88
END                           # User application 0
#
# User SAP configuration for 2nd application
#
USER_SAP              1       # Sap number start at 0
SWITCH_TYPE           ANSI92  # one of ITU92, ITU88, ANSI92, ANSI88
END                           # User application 0
#
# User SAP configuration for 3rd application
#
USER_SAP              2       # Sap number start at 0
SWITCH_TYPE           ANSI92  # one of ITU92, ITU88, ANSI92, ANSI88
END                           # User application 0
#
# User SAP configuration for 4th application
#
USER_SAP              3       # Sap number start at 0
SWITCH_TYPE           ANSI92  # one of ITU92, ITU88, ANSI92, ANSI88
END                           # User application 0

9.3 TCAP Configuration Reference

The following sections detail the configurable parameters for each configuration section.

9.3.1 General Parameters Definition

The general parameters configuration section defines the operational characteristics of the TCAP layer, mostly upper bounds for internal data structures (these determine the amount of memory used by the TCAP layer). It is the first section of the configuration file.

Field Name	Range	Description
MAX_TCAP_USERS	1 to 512	Maximum number of user SAPs. Default value is 4.
MAX_TCAP_DIALOGS	1 to 32767	Maximum number of TCAP transactions that may be pending at any one time. Default value is 256.
MAX_TCAP_INVOKES	1 to 32767	Maximum number of TCAP invoke operations that may be pending at any one time. Default value is 256.
MIN_TID_LEN	1 to 4	Forces use of transaction IDs of at least the specified number of bytes when using ITU-T TCAP; Primarily for interoperability with certain networks which require use of 4-byte transaction IDs. Default value is 1.
PC_FORMAT	DEFAULT [DFLT], INTER-NATIONAL [INTL], JNTT	Point Codes are interpreted/displayed as 24-bit 8.8.8 values. Point Codes are interpreted/displayed as 14-bit 3.8.3 values. Point codes are interpreted/displayed as 16-bit values in the following format: mcode.scode.ucode where the U-code occupies the most significant 7 bits, the S-code occupies the next 4 bits, and the M-code occupies the least significant 5 bits. Default value is DEFAULT.
TCAP_ALARM_LEVEL	0 to 3	The level of alarms to be generated by the TCAP layer: 0 = none (not recommended) 1 = service impacting events 2 = individual transaction impacting events (encode/decode errors) 3 = debugging level Default value is 1.
TCMEM_THRESH_1	1 to 99	Percentage of memory available in default message buffer pool below which congestion level 1 is triggered. Default value is 20.
TCMEM_THRESH_2	1 to 99	Percentage of memory available in default message buffer pool below which congestion level 2 is triggered. Must be less than TCMEM_THRESH_1. Default value is 15.
TCMEM_THRESH_3	1 to 99	Percentage of memory available in default message buffer pool below which congestion level 1 is triggered. Must be less than TCMEM_THRESH_2. Default value is 10.

9.3.2 User Service Access Point (SAP) Definitions

One user SAP is defined for each application/subsystem using the TCAP layer services. A user SAP is associated with a single subsystem number and switch type (ANSI88, ANSI92, ANSI96, ITU88, or ITU92, ITU97).

Note: Field names indicated in bold are only available with SS7 3.5 and later releases.

Field Name	Range	Description
USER_SAP	0 to (MAX_USERS-1)	Marks start of a User SAP definition. User SAP numbers start at zero and are numbered sequentially up to MAX_USERS-1. There is no default value.
SWITCH_TYPE	ITU88, ITU92, ITU97 ANSI88, ANSI92, ANSI96	Protocol variant used on this SAP. Default value is ANSI92.
TCAP_T1	1 to 32767	Default invocation timer, in seconds (time to wait for response to invoke). Default value is 60.
TCAP_T2	1 to 32767	Time to wait for reject of a non-invoke component, in seconds, before considering operational successful (where applicable). Default value is 60.
TCAP_SEQ_TIMER	1 to 255	Duration to request SCCP to maintain SLS for when sequential delivery required. Default value is 60.
SCCP_SAP	0 to 32766	SCCP SAP ID (from SCCP config.) to map this TCAP SAP onto. By default, set to the same value as the TCAP SAP ID.
ALLOW_INVOKE_END	0 or 1	When set to 1, allows an Invoke component in an ITU-T End message. Default value is 0.
SCCP_ADDR_OVERRIDE	0 or 1	SCCP called and calling addresses specified by a user application are ignored for the following messages: · ITU-T: Continue, End, and User Abort · ANSI: Conversation, Response, and User Abort If set to 1, SCCP called and calling addresses specified by the user application are used for all affected messages. Default value is 0.
INACTIVITY_TIMER	0 to 64535	Default inactivity timer. Number of seconds before an inactivity indication is sent for a transaction with no traffic. If set to zero, the inactivity timer is disabled. Default value is 0.
DEFAULT_CHECKPOINT	CHKPT_NONE, CHKPT_SEND, CHKPT_ALL	Default checkpoint value. If set to CHKPT_ALL, all transactions are checkpointed to the backup TCAP task. If set to CHKPT_SEND, only transactions initiated by the TX board are checkpointed. If set to CHKPT_NONE, no transactions are checkpointed. Default value is CHKPT_NONE.
TCQ_THRESH_1	1 to 65535	Number of inbound messages queued to the application before entering level 1 congestion. Default value is 600.
TCQ_THRESH_2	1 to 65535	Number of inbound messages queued to the application before entering level 2 congestion. Must be greater than TCQ_THRESH_1. Default value is 900.
TCQ_THRESH_3	1 to 65535	Number of inbound messages queued to the application before entering level 2 congestion. Must be greater than TCQ_THRESH_2. Default value is 1200.