S3. IMS Session Initiation signalling flow —
origination in CS Network
mobile termination in home network
S3-2c. SIP 183 Session Progress response:
from S-CSCF2 to I-CSCF1
(9 of 48)
: The S-CSCF adds the identifier of its own network to the terminating Inter Operator Identifier (IOI) parameter of this header and puts back the originating IOI parameter.
: The S-CSCF passes this header to the I-CSCF for charging.