R2. IMS Registration signalling flow —
Re-registration – User currently registered
R2-2a. SIP 200 OK response:
from S-CSCF1 to I-CSCF1
(8 of 10)
: 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.