Contains the P-CSCF address learnt during P-CSCF discovery, plus the elements from the
Service-Route header from registration. The P-CSCF URI contains the port number learnt
during the security agreement negotiation.
This field is populated with the value "reg" to specify the use of the registration state package.
This field is populated with the value "application/reginfo+xml".
Contains the security agreement as represented by the previously received Security-Server header.