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 ("user1_private@home1.net"), public user identity ("user1_public1@home1.net")
and visited domain identifier ("Visited Network Number 1") to the HSS.
Cx-Query response, or Diameter UAA: User-Authorization-Answer:
The HSS returns S-CSCF required capabilities and I-CSCF1 uses this information to select a suitable S-CSCF.