1 IMS Entities and the Information They Store During and After Registration
Device Before During After
Credentials
Home domain
Proxy name & address
Credentials
Home domain
Proxy name & address
Credentials
Home domain
Proxy name & address
P-CSCF Nothing stored Device address
Public user identity
Private user identity
Device address
Public user identity
Private user identity
I-CSCF HSS or SLF address S-CSCF address and name
P-CSCF domain
Home network domain
Nothing
HSS User service profile P-CSCF domain S-CSCF address & name
S-CSCF Nothing HSS address
User profile
P-CSCF address
P-CSCF domain
Public identity
Private identity
Device IP address
HSS address
User profile
P-CSCF address
P-CSCF domain
Public identity
Private identity
Device IP address
118 Chapter 5
The P-CSCF also subscribes to Event Notification and sends a SUBSCRIBE to the
S-CSCF with the following headers and parameters:
?– REQUEST-URI populated with the subscriber??™s default public user identity
?– FROM populated with the P-CSCF address
?– TO populated with the default public user identity of the subscriber
?– EVENT set to REG
?– EXPIRES set to a value higher than what was received in the 200 OK response
?– P-ASSERTED-IDENTITY populated with the address of the P-CSCF identified in
the PATH header of the initial REGISTER message
?– P-CHARGING-VECTOR populated with the IMS CHARGING IDENTIFICATION
(ICID)
The P-CSCF forwards the SUBSCRIBE to the I-CSCF in the home network of the
subscriber that the P-CSCF is subscribing to.
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