Only item f) applies to messages using the global call reference.
a) Whenever any message except SETUP,RELEASE, RELEASE COMPLETE, STATUS, STATUS ENQUIRY or (for networks supporting the call rearrangement procedures of 5.6) RESUME is received specifying acall reference which it does not recognize as relating to an active call or acall in progress, clearing is initiated by sending a RELEASE message with cause No. 81, invalid call reference value, and following the procedures in 5.3, specifying the call reference in the received message.
Alternatively, the receiving entity may send a RELEASE COMPLETE message with cause No. 81, invalid call reference value, and remain in the Null state.
b) When a RELEASE message is received that specified a call reference which is not recognized as relating to an active call or a call in progress, a RELEASE COMPLETE message with cause No.81, invalid call reference value, is returned, specifying the call reference in the received message.
c) When a RELEASE COMPLETE message is received specifying a call reference which it does not recognize as relating to an active call or a call in progress, no action should be taken.
d) When a SETUP or RESUME message is received specifying a call reference with a call reference flag incorrectly set to "1", that message shall be ignored.
e) When a SETUP message is received specifying a call reference which is recognized as relating to an active call, or a call in progress, this SETUP message shall be ignored.
f) When any message except RESTART, RESTART ACKNOWLEDGE, or STATUS is received using the global call reference, no action should be taken on this message and a STATUS message using the global call reference with a call state indicating the current state associated with the global call reference and cause No. 81, invalid call reference value, shall be returned.
g) When a STATUS message is received specifying a call reference which is not recognized as relating to an active call or to a call in progress, the procedures of 5.8.11 shall apply.
h) When a STATUS ENQUIRY message is received specifying a call reference which is not recognized as relating to an active call or to a call in progress, the procedures of 5.8.10 shall apply.
Note - Some implementations conforming to Recommendation Q.931 (1988) may choose to initiate clearing by sending a RELEASE message with cause No. 81, invalid call reference value, and continue to follow the procedures in 5.3, specifying the call reference in the received message, or respond with a RELEASE COMPLETE message with cause No. 81, invalid call reference value and remain in the Null state.
i) When a RESTART message is received specifying a global call reference with a call reference flag set to "1", that message shall be ignored.