CAS R2 scripting

This page contains information about TelcoBridges CAS R2 variant scripting.

Refer to the default script (itu.lua) in the Toolpack Web Portal for a complete working variant script example.

In this page, using the term "application" may refer to Toolpack or any other application using the basic TelcoBridges CAS R2 stack API.

Overview

CAS R2 signaling is done in two parts: line signaling and register signaling. In CAS R2 for E1 trunks, line signaling uses a single timeslot to communicate call states (such as off-hook, answering) for the remaining timeslots. Register signaling is the exchange of tones to convey information such as the calling number, called number and calling party category. TelcoBridges CAS R2 scripts allow complete customization of the register signaling process, while having some characteristics of the line signaling process customizable. Scripts also contain information relative to the conversion of register signaling data - group B signals and categories - into a format that the application can interpret.

Mandatory elements

In order for CAS R2 variant scripts to work, some variables, tables and events must be defined from within scripts. All of the following elements are required; if one of these elements is not present, it will not be possible to save the script in the Toolpack Web Portal or load it on the adapter.

VARIANT_ID

The VARIANT_ID variable must be filled to distinguish variants from another. More precisely, it is used when transporting group B and category information with calls in order to possibly convert information meaning across variants.

Default CAS R2 TelcoBridges scripts have variant IDs starting from 1. To avoid future conflicts, user scripts variant IDs should be prefixed with a sufficiently high value. For example, a modified ITU variant could have a ID equal to 0x0001001. Scripts may only share the same variant ID as other scripts if and only if the category and group B meanings are exactly identical.

Group B conversion information

Group B conversion information in scripts is used to convert group B information between CAS R2 variants and between other signaling types. The following elements must be filled so that these conversions can be completed successfully.

GROUPB_DIGIT_TO_MEANING

Each GROUPB_DIGIT_TO_MEANING table element must contain two values: a digit and a meaning. The digit must be a valid digit value (1 to 15) and the meaning must be a valid meaning (see Group B meanings). Each digit must be present in the table.

This table is used to convert group B digits to meaning in the context of an outgoing call. For a given digit, the specified meaning will be propagated to the application.

GROUPB_MEANING_TO_DIGIT

Each GROUPB_MEANING_TO_DIGIT table element must contain two values: a meaning and a digit. Meanings must not appear more than once in the table.

This table is used to convert meanings to digits for an incoming call. This is mostly used for calls where the other leg belongs to another signaling type, although it will be used if the other leg's signaling type is CAS R2 but the variant is different and there was no match in the GROUPB_OTHER_DIGITS table.

If a meaning is not found in this table, the meaning corresponding to GROUPB_DEFAULT_DIGIT will be used.

GROUPB_DEFAULT_DIGIT

This variable must be filled with a valid digit value. It will be used when lookups in the GROUPB_MEANING_TO_DIGIT table fail.

GROUPB_OTHER_DIGITS

Each GROUPB_OTHER_DIGITS table element must contain three values: a variant ID and two valid digit values. This table may be empty but cannot be omitted.

This table is used to convert a variant ID and a digit combination to a digit for the current variant in an outgoing call scenario.

Category conversion information

Category conversion information in scripts is used to convert category information between CAS R2 variants and between other signaling types. The following elements must be filled so that these conversions can be completed successfully.

The pattern used to handle categories is identical to the one used for group B conversions.

CATEGORY_DIGIT_TO_MEANING

Each CATEGORY_DIGIT_TO_MEANING table element must contain two values: a digit and a meaning. The digit must be a valid digit value (1 to 15) and the meaning must be a valid meaning (see Category meanings). Each digit must be present in the table.

This table is used to convert category digits to meaning in the context of an outgoing call. For a given digit, the specified meaning will be propagated to the application.

CATEGORY_MEANING_TO_DIGIT

Each CATEGORY_MEANING_TO_DIGIT table element must contain two values: a meaning and a digit. Meanings must not appear more than once in the table.

This table is used to convert meanings to digits for an incoming call. This is mostly used for calls where the other leg belongs to another signaling type, although it will be used if the other leg's signaling type is CAS R2 but the variant is different and there was no match in the CATEGORY_OTHER_DIGITS table.

If a meaning is not found in this table, the meaning corresponding to CATEGORY_DEFAULT_DIGIT will be used.

CATEGORY_DEFAULT_DIGIT

This variable must be filled with a valid digit value. It will be used when lookups in the CATEGORY_MEANING_TO_DIGIT table fail.

CATEGORY_OTHER_DIGITS

Each CATEGORY_OTHER_DIGITS table element must contain three values: a variant ID and two valid digit values. This table may be empty but cannot be omitted.

This table is used to convert a variant ID and a digit combination to a digit for the current variant in an outgoing call scenario.

Event handlers

Four register signaling event handlers must be defined in the script.

Call context table

Each event handler will have a table passed as a parameter. This table is the call context table, and contains critical information about the state of the call. Once calls are created (through Bwd_HandleNewCall and Fwd_HandleNewCall), the script must initialize the table with its own state information. Also, for incoming calls, as they go on, the script must fill the table with the collected signaling information. For outgoing calls, the table already contains this signaling information. The signaling information fields contained in the table are as follows:

Table element	Description
DestinationNumber	String of digits representing the called (destination) number.
OriginNumber	String of digits representing the calling (origin) number.
Category	Digit representing the calling party category. See Category conversion information.

Return values

Each event handlers must return two values. The first value is the action to take immediately or shortly following the call of the event. It must be set to one of the four following values:

First return value	Description
WAIT_SIGNAL	Generally emits the digit provided as the second return value, and waits for the response or the next compelled sequence.
END_SIGNALING	Ends the call with the provided digit.
VALIDATE_CALL	(Incoming only) Sends the cumulated signaling information to the application and ends the signaling.
PULSE_SIGNAL	(Incoming only) Emits a pulsed signal.

The second return value is the digit that accompanies the action, or NO_DIGIT if no digit must be emitted. Its meaning depends on the first return value.

Backward event handlers

The following event functions must be defined so that the CAS R2 stack can proceed with register signaling for incoming calls.

Bwd_HandleNewCall

The Bwd_HandleNewCall event is called whenever an incoming call is discovered on a timeslot. The purpose of this event is for the script to initialize local variables that will be used throughout the tone exchanges.

The event will have the call context table passed as a parameter. This table must be filled with the call state information required by the script for a new incoming call.

The event must return two values as described in the following table:

First return value	Description
WAIT_SIGNAL	Waits for the first compelled sequence to be initiated. The second return value must be NO_DIGIT.
END_SIGNALING	Ends the call immediately. The second return value must be NO_DIGIT.

Bwd_HandleFwdSignal

The Bwd_HandleFwdSignal is called whenever a tone signal has been received, which is most likely the beginning of a compelled sequence.

The event will receive two parameters: the call context table (which was also passed to Bwd_HandleNewCall) and the received tone signal. The event must use the received tone signal to fill the DestinationNumber, OriginNumber and Category fields of the call context table.

The event must return two values as described in the following table:

First return value	Description
WAIT_SIGNAL	Waits for the next compelled sequence to be initiated. The second return value must be a valid digit as it is emitted as a response to the current compelled sequence.
END_SIGNALING	Ends the call immediately. The second return value can either be NO_DIGIT or a valid digit. If the digit is valid and has an acceptance meaning (see the Group B conversion information section), the call will be accepted without explicit validation by the application. Otherwise, the call will be refused. In both cases, the digit will be emitted.
VALIDATE_CALL	Sends the cumulated signaling information to the application. The application will then provide a group B meaning (or digit) that will be sent to the outgoing end.
PULSE_SIGNAL	Instead of waiting for the next compelled sequence, the event handler will be called again with NO_DIGIT as a second parameter. The second return value must be a valid digit since it will be sent to complete the current compelled sequence.

Optional elements

The following elements may or may not be defined into a CAS R2 script.

SCRIPT_FILE_NAME

When affecting a value to this variable, the Toolpack Web Portal will automatically replace the value to the script name followed by the script revision. If the following piece of code is added appended at the end of the script (this is done for default scripts), it will print a trace when loading a CAS R2 stack which can be recovered using an application such as tblogtrace.

VARIABLES

The VARIABLES table is used to declare variables which can be altered through the Toolpack Web Portal. Typically, variables declared here contain parameters that affect particular trunks. Each row of this table must contain three elements: the variable name, the variable's default value and the variable's description.

Reference

Stack variables

Here is the list of stack variables. These variables are declared before the VARIABLES table is parsed in a script. A single script affectation will modify the value one of these variables. It is also possible to edit these variables in the Toolpack Web Portal.

Variable name	Default value	Description
TIMER_BWD_TONE	15000	Maximum time before a call is closed because the forward end did not emit a tone.
TIMER_BWD_PULSE	250	Length of a pulsed digit.
TIMER_BWD_PULSE_GUARD	100	Time between the end of a compelled sequence and the beginning of a pulsed digit.
TIMER_BWD_PULSE_DETECTION	3000	Time elapsed after a compelled sequence that triggers a pulsed digit.
TIMER_BWD_ALERT	14000	Maximum wait time for an ALERT API message.
TIMER_BWD_ANSWER	14000	Maximum wait time for an ANSWER API message.
TIMER_BWD_TERMINATE	3000	Maximum wait time for an TERMINATE API message.
TIMER_BWD_HOLD_ANSWER	100	Maximum time for which the CAS bits should stay in the ANSWER state before chaning to CLEAR_BACKWARD.
TIMER_BWD_HOLD_CLEAR_BACKWARD	200	Maximum time for which the CAS bits should stay in the CLEAR_BACKWARD state.
TIMER_BWD_HOLD_FORCED_RELEASE	200	Maximum time for which the CAS bits should stay in the FORCED_RELEASE state.
TIMER_BWD_HOLD_IDLE	100	Maximum time for which the CAS bits should stay in the IDLE state before starting a new call on the same timeslot.
TIMER_FWD_TONE	15000	Maximum time before a call is closed because the forward end did not emit a tone.
TIMER_FWD_TONE_GUARD	0	Time between the end of a compelled sequence and the beginning of the next one.
TIMER_FWD_SEIZURE_ACK_BIT	200	Maximum time for which the forward end should wait for a CAS bits SEIZURE_ACKNOWLEDGE state.
TIMER_FWD_ANSWER_BIT	14000	Maximum time for which the forward end should wait for a CAS bits ANSWER state.
TIMER_FWD_TERMINATE	3000	Maximum wait time for an TERMINATE API message.
TIMER_FWD_HOLD_SEIZURE	100	Maximum time for which the SEIZURE CAS bits state should be held in case of a collision.
TIMER_FWD_HOLD_IDLE	100	Maximum time for which the CAS bits should stay in the IDLE state before starting a new call on the same timeslot.
TIMER_CAS_CHANGE	20	Time required for a CAS bits state change to take effect.
ABCD_PATTERN_IDLE	0x1001	CAS R2 bit pattern for the IDLE state.
ABCD_PATTERN_BLOCKED	0x1101	CAS R2 bit pattern for the BLOCKED state.
ABCD_PATTERN_FWD_SEIZURE	0x0001	CAS R2 bit pattern for the forward SEIZURE state.
ABCD_PATTERN_FWD_CLEAR_FWD	0x1001	CAS R2 bit pattern for the forward CLEAR state.
ABCD_PATTERN_BWD_SEIZURE_ACK	0x1101	CAS R2 bit pattern for the backward SEIZURE ACKNOWLEDGE state.
ABCD_PATTERN_BWD_ANSWERED	0x0101	CAS R2 bit pattern for the backward ANSWERED state.
ABCD_PATTERN_BWD_CLEAR_BWD	0x1101	CAS R2 bit pattern for the backward CLEAR state.
ABCD_PATTERN_BWD_FORCED_RELEASE	0x0001	CAS R2 bit pattern for the backward FORCED RELEASE state.
USE_FORCED_RELEASE	0	Flag indicating if the CAS R2 line signaling state machine should use the forced release method.

Group B meanings

Here is the list of all defined group B meanings:

ACCEPT_CHARGE
ACCEPT_NO_CHARGE
REJECT_UNSPECIFIED
REJECT_UNALLOCATED_NUMBER
REJECT_NO_ROUTE_TO_NETWORK
REJECT_NO_ROUTE_TO_DESTINATION
REJECT_USER_BUSY
REJECT_SUBSCRIBER_ABSENT
REJECT_CALL_REJECTED
REJECT_NUMBER_CHANGED
REJECT_EXCHANGE_ROUTING_ERROR
REJECT_DESTINATION_OUT_OF_ORDER
REJECT_ADDRESS_INCOMPLETE
REJECT_NO_CIRCUIT_AVAILABLE
REJECT_NETWORK_OUT_OF_ORDER
REJECT_TEMPORARY_FAILURE
REJECT_SWITCHING_EQUIP_CONGESTION
REJECT_REQUESTED_CIRCUIT_NOT_AVAILABLE
REJECT_RESOURCE_UNAVAILABLE
REJECT_SERVICE_NOT_AVAILABLE
REJECT_CALL_IDENTITY_DOES_NOT_EXIST
REJECT_CALL_IDENTITY_IN_USE
REJECT_PROTOCOL_ERROR
REJECT_INTERWORKING_UNSPECIFIED

Category meanings

Here is the list of all defined category meanings:

CATEGORY_UNKNOWN
CATEGORY_OPERATOR_FRENCH
CATEGORY_OPERATOR_ENGLISH
CATEGORY_OPERATOR_GERMAN
CATEGORY_OPERATOR_RUSSIAN
CATEGORY_OPERATOR_SPANISH
CATEGORY_SUBSCRIBER
CATEGORY_SUBSCRIBER_WITH_PRIORITY
CATEGORY_DATA
CATEGORY_TEST
CATEGORY_PAYPHONE