If the Call reference information element octet 1, bits 5 through 8 do not equal 0000, then the message shall be ignored.
If the Call reference information element octet 1, bits 1 through 4 indicate a length greater than the maximum length supported by the receiving equipment (see 4.3), then the message shall be ignored.
When a message is received with the dummy call reference it shall be ignored unless it is required for a supplementary service (see Recommendation Q.932 [4]).