9.1 Introduction

9.1.1 Invoking D Channel Identifier Request

9.1 Introduction

This chapter describes the D Channel Identifier Request supplementary service. The D Channel Identifier Request service allows an application to get the switch-assigned value of a particular PRI.

9.1.1 Invoking D Channel Identifier Request

To get the D Channel Identifier of a particular PRI, an application should invoke the D Channel Identifier Request supplementary service on any of the existing calls on the PRI. It sends an acu_ss_d_channel_id_rq_invoke extended data structure to the stack, in an ACU_FACILITY_RQ message. The service header to this structure must contain:

• Operation ID ACU_OP_ID_D_CHANNEL_ID_RQ

• OpType ACU_OP_TYPE_INVOKE

The following is listing of the acu_ss_d_channel_id_rq_invoke extended data structure:

struct acu_ss_d_channel_id_rq_invoke

{

struct u4_acu_ext_hdr ext_hdr; /* extension header */

struct u4_acu_ss_hdr ss_hdr; /* supplementary services header */

};

Successful D Channel Identifier Request

When a request is successful, the application receives the ACU_FACILITY_IN message, which also contains an acu_ss_d_channel_id_rq_ret_result extended data structure. The service header to this structure contains:

• Operation ID ACU_OP_ID_D_CHANNEL_ID_RQ

• OpType ACU_OP_TYPE_RETRES

The following is a listing of the acu_ss_d_channel_id_rq_ret_result extended data structure:

struct acu_ss_d_channel_id_rq_ret_result

{

struct u4_acu_ext_hdr ext_hdr; /* Extension header */

struct u4_acu_ss_hdr ss_hdr; /* Supplementary services header */

struct acu_d_channel_id dCID;

};

The following is a listing of the acu_d_channel_id structure within the acu_ss_d_channel_id_rq_ret_result extended data structure:

#define ACU_MX_SZ_D_CHNL_ID 4 /* Default maximum size for D channel ID */

struct acu_d_channel_id

{

uchar value[ACU_MX_SZ_D_CHNL_ID]; /* D Channel Identifier value */

uchar length; /* Length of D Channel Identifier value */

pad3

};

where:

• dCID.value contains the D Channel Identifier value

• dCID.length contains the length of the value (from 1 to 4)

Figure 53 illustrates a successful D Channel Identifier Request.

Figure 53. Successful D Channel Identifier Request

Unsuccessful D Channel Identifier Request

When a request is not successful, the application receives the ACU_FACILITY_IN message containing an acu_ss_d_channel_id_rq_ret_err extended data structure. The service header to this structure contains:

• Operation ID ACU_OP_ID_D_CHANNEL_ID_RQ

• OpType ACU_OP_TYPE_RETERR

The following is a listing of the acu_ss_d_channel_id_rq_ret_err extended data structure:

struct acu_ss_d_channel_id_rq_ret_err

{

struct u4_acu_ext_hdr ext_hdr; /* extension header */

struct u4_acu_ss_hdr ss_hdr; /* supplementary services header */

ushort err_id; /* From D_CHANNEL_ID_RETERR... constants */

pad6

};

The err_id field contains the error reason, from the TBCT_RETERR constants.

Constant	Description
D_CHANNEL_ID_RETERR_NOT_AVAILABLE	The network does not have an interface identifier assigned to the PRI.
D_CHANNEL_ID_RETERR_NOT_SPECIFIED	The error is not known.

Figure 54 illustrates an unsuccessful D Channel Identifier Request.

Figure 54. D Channel Identifier Request Error