IMS Registration signalling flow —
User not registered
R1-1d. SIP REGISTER request: between I-CSCF1 and HSS(5 of 22)
Cx-Query, or Diameter UAR: User-Authorization-Request:
I-CSCF1 makes a request for information related to the Subscriber registration status by sending the
private user identity ("firstname.lastname@example.org"), public user identity ("email@example.com")
and visited domain identifier ("Visited Network Number 1") to the HSS.