4.2. L2_BLK

The L2_BLK data structure is used to send or receive a frame of information to or from the data link layer using the gc_SndFrame( ) or the gc_GetFrame( ) function. See example code for these functions in the GlobalCall API Software Reference for details.

The L2_BLK data structure is defined as follows:

 #define MAXLEN_IEDATA    254
typedef struct
  {
   char sapi;
   char ces;
   short length;
   char data[MAXLEN_DATA];
   } L2_BLK, *L2_BLK_PTR; 

See Table36 for descriptions of the L2_BLK fields.

Table 36. L2_BLK Fields 

Field	Description
sapi	service access point ID (always set to 0)
ces	connection endpoint suffix (always set to 0)
length	Length of data block in bytes. Value must be less than MAXLEN_IEDATA as defined in gcisdn.h.
data[MAXLEN_IEDATA]	Data for frame. Must be formatted to meet CCITT recommendations. The maximum length of the data field is MAXLEN_IEDATA.

The following L2 block structure can be passed to the function via the GC_L2_BLK structure. */

      l2_blk_ptr[0] = 0x08;     /* Protocol discriminator */
     l2_blk_ptr[1] = 0x02;     /* CRN length - 2 bytes */
     l2_blk_ptr[2] = 0x03;     /* CRN = 8003 */
     l2_blk_ptr[3] = 0x80;
     l2_blk_ptr[4] = 0x6e;     /* msg type = NOTIFY */
      /* The first IE */
     l2_blk_ptr[5] = 0x27;     /* IE type = 27 (NOTIFY) */
     l2_blk_ptr[6] = 0x01;     /* The length of NOTIFY */
     l2_blk_ptr[7] = 0xF1;     /* Notify indication */
      /* The second IE */
     l2_blk_ptr[8] = 0x76;     /* IE type = 76 (REDIRECTION) */
     l2_blk_ptr[9] = 0x03;     /* length of redirection */
     l2_blk_ptr[10] = 0x01;    /* unknown type and E164 plan */
     l2_blk_ptr[11] = 0x03;    /* network provides presentation */
     l2_blk_ptr[12] = 0x8D;    /* reason = transfer */

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