You are here: CSP Developer’s Guide: Common Channel Signaling > 6 SCCP/TCAP > TCAP Primitive Set Interface

TCAP Primitive Set Interface

Purpose

The TCAP Primitive Set Interface feature is based on the existing TCAP software architecture. TCAP and the SS7 layer below it reside on the CSP and the TC-User resides on the host.

TCAP communicates with the TC-User through multiple TC-primitives so that a dialog can be embedded into a single PPL Event Request or PPL Event Indications API message.

This feature provides the following:

• Reduces the API level transport and processing overhead on various software components, such as the SS7 host communication and transport layer, and host application message processing and transport layer.

• Reduces message traffic on the internal Ethernet or HDLC depending on the architecture, thereby improving overall system performance.

TCAP Primitive Set Interface Description

The host application sends and receives messages to and from the TCAP USer Interface (TUSI) PPL component for the primitive set interface. Each TC-primitive type is uniquely identified by a PPL Event ID in the PPL Event Request and PPL Event Indication API messages. These API messages include all of the ICBs for each individual TC-primitive. A component TC-primitive includes a TCAP parameter ICB. A dialog TC-primitive includes a TCAP parameter ICB plus an optional SCCP parameter ICB for SCCP addresses.

TCAP Outgoing Message

The TUSI parses and validates the PPL Event Request API message with TC primitive set PPL Event ID from the TC-User. After validation, the TUSI sends the component primitive data and the dialog primitive data to the TCAP PPL components according to the TCAP protocol.

• The TUSI first sends each component primitive data to the TCAP PPL components in the order presented in the API message.

• The TUSI then sends the dialog primitive data to the TCAP PPL components and sends a Positive Acknowledgement to the TC-User.

• Other TCAP PPL components will process each of these primitives individually.

TCAP Incoming Message

When TCAP receives an incoming message with one or more components, the TCAP PPL components process this message according to the TCAP protocol.

• After processing, the dialog primitive data first and then the component primitive data are sent to the TUSI.

• The TUSI packs the dialog primitive ICB(s), followed by all the component ICBs in the order it receives them.

• It then sends all of these ICBs in one PPL Event Indication API message to the TC-User.

TUSI Negative Acknowledgements (NACK)

The TUSI sends a negative acknowledgement (NACK) to the TC-User if it detects syntax errors in the PPL Event Request API message. The TC-User may re-send the API message after receiving a NACK from TCAP.

Important! The TC-User is responsible for the correctness and consistency of the contents in the PPL Event Request API message. After the TUSI validates the API message syntax and sends the dialog and component primitives to other TCAP PPL components, TCAP would consider any detected error as an unrecoverable error for the dialog primitives, therefore the dialog primitives will be aborted in this case. The TC-User as well as the network (if needed) will be informed.

TCAP Primitive Set Interface Call Flow

The following call flow provides an example of the TCAP to TC-User interface using the TCAP Primitive Set Interface feature.

TCAP Primitive Sets PPL Events

The TCAP Primitive Sets PPL Events listed below are provided for the TCAP Primitive Set Interface. One PPL Event is defined for each dialog TC-primitive type that is allowed to have attached component(s). The PPL Events listed below are in addition to the currently supported PPL Events for individual TC-primitives.

ANSI Variant TC Primitive Set PPL Events

TC_UNI Primitive Set (0x31) (PPL Event Indication and PPL Event Request)

TC_QUERY_WITH_PERMISSION Primitive Set (0x35) (PPL Event Indication and PPL Event Request)

TC_QUERY_WITHOUT_PERMISSION Primitive Set (0x36) (PPL Event Indication and PPL Event Request)

TC_CONVERSATION_WITH_PERMISSION Primitive Set (0x37) (PPL Event Indication and PPL Event Request)

TC_CONVERSATION_WITHOUT_PERMISSION Primitive Set (0x38) (PPL Event Indication and PPL Event Request)

TC_RESPONSE Primitive Set (0x39) (PPL Event Indication and PPL Event Request)

ITU/ETSI Variant TC Primitive Set PPL Events

TC_UNI Primitive Set (0x31) (PPL Event Indication and PPL Event Request)

TC_BEGIN Primitive Set (0x32) (PPL Event Indication and PPL Event Request)

TC_CONTINUE Primitive Set (0x33) (PPL Event Indication and PPL Event Request)

TC_END Primitive Set (0x34) (PPL Event Indication and PPL Event Request)

ANSI/ITU/ETSI Variant TC Primitive PPL Event

PPL_EVENT_TCAP_INITIATED_U_ABORT (0x21) (PPL Event Indication)

This PPL Event Indication is initiated by TCAP due to software internal inconsistency and unrecoverable errors. These errors can be caused by incorrect data passed from the TC-User or other software module in the system as well as TCAP internal software errors.

Important! This event is different from TC_U_ABORT event that indicates the remote TCAP User aborted the transaction.

TC Primitive Set

To align with the ICBs in individual TC-primitives, a TC Primitive Set includes a TCAP dialog primitive ICB and zero, one, or more TCAP component ICBs, and an optional SCCP ICB for SCCP addresses.

A zero-component is allowed to be compliant with the TCAP standard where the component portion is optional in some TCAP messages. Whether it is mandatory for each TCAP message to include a component is based on the specific TCAP standard variants.

When using the TCAP Primitive Set Interface, use the following TC-primitive variants in addition to the TC primitive set events:

ANSI Variants

TC_U_ABORT (PPL Event Indication and PPL Event Request)

TC_P_ABORT (PPL Event Indication)

TC_NOTICE (PPL Event Indication)

ITU/ETSI Variants

TC_U_ABORT (PPL Event Indication and PPL Event Request)

TC_P_ABORT (PPL Event Indication)

TC_NOTICE (PPL Event Indication)

TC_L_CANCEL (PPL Event Indication)

TCAP Primitive Options

TCAP primitive configuration options, per SS7 stack, are provided to select either the Individual TCAP Primitive API option or the TCAP Primitive Set Interface option.

The default is the Individual TC Primitive API option for backward compatibility considerations. The TCAP PPL Component TUSI Configuration Byte is used for this purpose.

Use the TCAP primitive ICB subtype for TCAP primitive sets.

ICB Subtype - TCAP Primitive ICB

The TCAP primitive ICB subtype (0x65) has two additional bytes for the TCAP TC-primitive ID in the following ICB formats:

• Data (bytes 8 and 9)

• Extended Data (bytes 10 and 11)

Compared to the existing TCAP parameter ICB, the TCAP TC-primitive ID value is same as the corresponding PPL Event ID value. The TCAP parameter TLVs for each TC primitive remain same as in current TCAP parameter ICB.

TCAP TUSI PPL Configuration Byte

Byte | Description | Value
--- | --- | ---
0x09 | Selects TCAP to TC-User interface format | 0x00 = Use individual TC-Primitive (Default) 0x01 = Use TCAP Primitive Set Interface

Examples

You can view TCAP Primitive Set API messaging examples in Example Configurations and TCAP API Messaging.

See Transaction Capability Application Part.
See Signaling System Number Seven.
See Programmable Protocol Language.
A condition that, when met, drives a state machine from one state to another. A condition that drives a Component out of its current state by invoking an associated primitive.
The protocol used in most local area PC networks. Typically, most Ethernet networks support data transmission speeds up to 10 Mbps, but 100 Mbps is also possible.
See Information Control Block.
Negative acknowledgement to a message.
American National Standards Institute. ANSI administers and coordinates the U.S. voluntary standardization and conformity assessment system for the
telecommunications industry. More details on these standards may be
viewed at www.ansi.org.
International Telecommunications Union (UN)
European Telecommunications Standards Institute
In PPL, a condition that, when met, drives a state machine (PPL Component) from one state to another, by invoking an associated Primitive. In PPL files, an Event is marked by an arrow and text.
A programmable software component that uses PPL state machines that can be modified with the PPL Tool.