Section: 8.3.1 Call Control
Content: The mobile station and the network shall ignore a Call Control message received with TI EXT bit = 0. Otherwise, if the TI EXT bit =1 or no extension is used, the behaviour described below shall be followed. The mobile station and network shall reject a SETUP, EMERGENCY SETUP or START CC message received with octet 1 part of the TI value coded as "111" by sending RELEASE COMPLETE with cause #81 "Invalid transaction identifier value" The TI value in RELEASE COMPLETE shall be the complete TI value including the extension octet from the message that caused the rejection. Any message other than SETUP, EMERGENCY SETUP or START CC received with octet 1 part of the TI value coded as "111" shall be ignored. For a call control message received with octet 1 part of the TI value not coded as "111", the following procedures shall apply: a) For a network that does not support the "Network initiated MO call" option and for all mobile stations: Whenever any call control message except EMERGENCY SETUP, SETUP or RELEASE COMPLETE is received specifying a transaction identifier which is not recognized as relating to an active call or to a call in progress, the receiving entity shall send a RELEASE COMPLETE message with cause #81 "invalid transaction identifier value" using the received transaction identifier value and remain in the Null state. For a network that does support the "Network initiated MO call" option $(CCBS)$: Whenever any call control message except EMERGENCY SETUP, SETUP, START CC or RELEASE COMPLETE is received specifying a transaction identifier which is not recognized as relating to an active call or to a call in progress, the receiving entity shall send a RELEASE COMPLETE message with cause #81 "invalid transaction identifier value" using the received transaction identifier value and remain in the Null state. b) When a RELEASE COMPLETE message is received specifying a transaction identifier which is not recognized as relating to an active call or to a call in progress, the MM connection associated with that transaction identifier shall be released. c) For a network that does not support the "Network initiated MO call" option and for all mobile stations: When an EMERGENCY SETUP or, a SETUP message is received specifying a transaction identifier which is not recognized as relating to an active call or to a call in progress, and with a transaction identifier flag incorrectly set to "1", this message shall be ignored. For a network that does support the "Network initiated MO call" option $(CCBS)$: When an EMERGENCY SETUP, a START CC or, a SETUP message is received specifying a transaction identifier which is not recognised as relating to an active call or to a call in progress, and with a transaction identifier flag incorrectly set to "1", this message shall be ignored. d) When a SETUP message is received by the mobile station specifying a transaction identifier which is recognized as relating to an active call or to a call in progress, this SETUP message shall be ignored. e) For a network that does not support the "Network initiated MO call" option: When an EMERGENCY SETUP message or a SETUP message is received by the network specifying a transaction identifier which is recognized as relating to an active call or to a call in progress, this message need not be treated and the network may perform other actions. For a network that does support the "Network initiated MO call" option $(CCBS)$: When an EMERGENCY SETUP message or a START CC message is received by the network specifying a transaction identifier which is recognised as relating to an active call or to a call in progress, this message need not be treated and the network may perform other actions. The same applies to a SETUP message unless the transaction has been established by a START_CC message and the network is in the "recall present" state (N0.6).