Section: 5.2.1.3 Receipt of a CALL PROCEEDING message
Content: Having entered the "call initiated" state, when the call control entity of the mobile station receives a CALL PROCEEDING message, it shall stop timer T303; start timer T310 unless - the CALL PROCEEDING message contains a progress indicator IE specifying progress description #1, #2, or #64; or - it has received a PROGRESS message containing a progress indicator IE specifying progress description #1, #2, or #64 prior to the CALL PROCEEDING message and enter the "mobile originating call proceeding" state. Abnormal case: If timer T310 elapses before any of the ALERTING, CONNECT or DISCONNECT messages has been received, the mobile station shall perform the clearing procedure described in subclause 5.4. Figure 5.3/3GPP TS 24.008[ Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 ]  Call proceeding sequence at mobile originating call establishment