IMS Registration signalling flow —
User not registered
R1-4a. SIP 200 OK response:
from S-CSCF1 to I-CSCF1
(20 of 22)
S-CSCF1 sends a 200 (OK) response to I-CSCF1 indicating that Registration was successful.
S-CSCF1 inserts the Service-Route header that includes its own URI including a character string in the user part to differentiate mobile originating requests from mobile terminating requests.