Question: What triggers the start and end of the time interval accumulation for the 'Accumulated originating session time' measurement at the P-CSCF or S-CSCF in IMS?
Option 1: Transmission of SIP_INVITE message and receipt of SIP_ACK response message
Option 2: Transmission by the originating P-CSCF or S-CSCF of a SIP_200_OK response message to initial SIP_INVITE, and receipt of corresponding release message 'BYE'
Option 3: Receipt of SIP_INVITE message and transmission of SIP_BYE response message
Option 4: Transmission of SIP_REGISTER request and receipt of SIP_200_OK response for registration
Explanation: This is the correct answer because, according to the performance measurement specification, the time interval starts with the transmission by the P-CSCF or S-CSCF of a SIP_200_OK response to an initial SIP_INVITE (indicating successful session setup) and ends with the receipt of the corresponding release message 'BYE' (indicating session teardown), accurately reflecting the duration of an originating session.