R2. IMS Registration signalling flow —
Re-registration – User currently registered
R2-2. SIP 200 OK response
(7 of 10)
Update registration timer: As the REGISTER request arrived integrity protected, S-CSCF1 does not need
to challenge the user, but
just update the registration timer to the value requested by the user (if the policy of the network allows it).
NOTE: S-CSCF1 is allowed to challenge the user. If S-CSCF1 decides to challenge the user, the call flow
will be similar to the one presented in "Registration: user not registered".