LDC_ELEM_SIZE
#define LDC_PACKET_SIZE (LDC_ELEM_SIZE * 8)
#define LDC_PAYLOAD_SIZE_UNRELIABLE (LDC_PACKET_SIZE - LDC_ELEM_SIZE)
#define LDC_PAYLOAD_SIZE_RELIABLE (LDC_PACKET_SIZE - (LDC_ELEM_SIZE * 2))
#define VIO_PAYLOAD_ELEMS (VIO_PAYLOAD_SZ / LDC_ELEM_SIZE) /* num words */