Section: 5.4.2 Exception conditions
Content: Under normal conditions, the call control entity of the mobile station or of the network initiates call clearing by sending a DISCONNECT message to its peer entity; then both entities follow the procedures defined in subclauses 5.4.3 and 5.4.4 respectively. As an exception to the above rule, the call control entity of the mobile station or of the network, in response to a SETUP or START CC or CC-ESTABLISHMENT CC-ESTABLISHMENT CONFIRMED or RECALL message, can reject a call by stopping all running call control timers, responding with a RELEASE COMPLETE message, releasing the MM connection, and returning to the "null" state, provided no other response has previously been sent. As a further exception, the call control entity of the network may initiate call clearing by stopping all running call control timers, sending a RELEASE message, starting timer T308, and entering the "release request" state. NOTE: This way to initiate call clearing by sending a RELEASE message should not be used by the network: - if in-band tones/announcements are provided and the network decides to use the procedure described in subclause 5.4.4.1.1.1 or 5.4.4.2.1; - if the network wants to have the opportunity to respond to information sent by the mobile station during call clearing, e.g. when the network indicates that "CCBS activation is possible". A call control entity shall accept an incoming RELEASE COMPLETE message used to initiate the call clearing even though the cause information element is not included. A control entity shall accept an incoming RELEASE message used to initiate the call clearing even though the cause information element is not included. Furthermore, a call control entity shall regard an incoming RELEASE COMPLETE message as consistent with any of its states; a call control entity shall regard an incoming RELEASE message as consistent with any of its states except the null state: a call control entity of the mobile station shall regard an incoming DISCONNECT message as consistent with any of its call control states except the "null" state, the "release request" state, and the "disconnect indication" state; a call control entity of the network shall regard an incoming DISCONNECT message as consistent with any of its call control states except the "null" state and the "release request" state. NOTE: This allows the introduction of shorter call clearing procedures in the future.