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Appendix D

Sending and Receiving PCS-User Information

Introduction
Structure of User-PCS IEs
Sending and Receiving PCS Information Elements
Example Code

IntroductionTop of Page

The user-to-PCS and PCS-to-user information elements are network-specific information elements (coded using codeset 6), to transmit information between the user and a PCS (Point de Commande de Service). They are used in the French ISDN variant (VN6). These information elements can be included in several ISDN message types, in the call setup, call connected, and call disconnection phases.

This appendix describes:

Structure of User-PCS IEsTop of Page

Each user-to-PCS and PCS-to-user information element includes:

Sending and Receiving PCS Information ElementsTop of Page

An application using the ISDN Messaging API interface can send and receive user-to-PCS and PCS-to-user information elements, for the VN6 variant only, in the following primitives:
ACU_CONN_RQ

 ACU_CONN_IN

ACU_CONN_RS

 ACU_CONN_CO

ACU_ALERT_RQ

 ACU_ALERT_IN

ACU_PROGRESS_IN

 ACU_CLEAR_RQ

ACU_CLEAR_IN

 ACU_CLEAR_RS

ACU_CLEAR_CO

 ACU_FACILITY_RQ

ACU_FACILITY_IN

The AG ISDN stack provides three macros for each primitive, for accessing these information elements. (xxx represents the primitive name; i.e., conn_rq):

The application can send pcs_user information in the Connected state, using the ACU_FACILITY_RQ primitive. In this case, in addition to the pcs_user macros previously described, the following macros must be set:
Macro

 Must be set to...

Acu_facility_code

 ACU_FAC_PCS_USER_ONLY

Acu_facility_action

 ACU_RQ_ACTIVATE

The user-to-PCS information element can only be sent in the user-to-network direction. The PCS-to-user information element can only be sent in the network-to-user direction. Therefore, the two information elements are never present at the same time in an ISDN message. For this reason, the same macros are used for both information elements.

There are no restrictions on the contents of the information area in the user-to-PCS or PCS-to-user information elements. Non-printable characters, including "\0", can be sent and received. However, for consistency with other macros and for ease of use, the stack automatically adds a "\0" character at the end of any incoming pcs_user information. For example, if the incoming pcs_user information is 0x31 0x32 0x33 (representing the number "123"), the stack sets the Acu_xxx_pcs_user_size macro to 4 and adds a 0x00 byte.

For outbound pcs_user information elements, the stack sends the exact number of octets specified by the application in Acu_xxx_pcs_user_size. For example, to send 0x31 0x32 0x33, the application sets Acu_xxx_pcs_user_size to 3.

Example CodeTop of Page

The following code sample illustrates how to build a structure containing PCS information, prior to sending it:

void build_facility_with_pcs(char *buffer, int *len)
{
struct acu_facility *p_data;
/* for simplicity lets use a string, we could also have used non-printable
characters here and use memcpy instead of strcpy */
char pcs_string[] = "pcs_string";

p_data = (struct acu_facility *)buffer;

memset(p_data, OFF, ISDN_BUFFER_DATA_LGTH);

Acu_facility_code = ACU_FAC_PCS_USER_ONLY;
Acu_facility_action = ACU_RQ_ACTIVATE; 
Acu_facility_pcs_user_protocol = ACUPCS_USER_TRANSGROUP;
strcpy(Acu_facility_a_pcs_user,pcs_string);
Acu_facility_pcs_user_size = strlen(pcs_string);

*len = Acu_facility_total_size;

return;
}

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