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Reference Architecture of R00. Support of Roaming Subscribers. via the service platform in the Home Network via an external service platform. UE Accessing IM Subsystem Services. In the visited network. Public and Private Identities. One or more private user identities IMSI within a NAI
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Support of Roaming Subscribers • via the service platform in the Home Network • via an external service platform
UE Accessing IM Subsystem Services • In the visited network
Public and Private Identities • One or more private user identities • IMSI within a NAI • is not used for routing of SIP messages • One or more public user identities
Roles of CSCF • Call State Control Function • SIP proxy servers • Proxy CSCF • The first contact point within the IM subsystem • Forward the SIP register requests from the UE to an I-CSCF • Forward the SIP messages from the UE to the S-CSCF • CDR • Authorisation of bearer resources and QoS management. For details see TS 23.207
Interrogating CSCF • The contact point within an operator’s network • Assign an S-CSCF to a user performing SIP Reg • Route a SIP request received from another network towards the S‑CSCF • Obtain from HSS the address of the S-CSCF • Forward the SIP request or response to the S‑CSCF determined by the step above • CDR
Serving CSCF • A registrar • Session control for the registered endpoint's sessions. • Interaction with Services Platforms • On behalf of an originating endpoint • On behalf of an destination endpoint • CDR • Authenticate the UEs
Home A Home B HSS HSS 8 7 4 3 9 6 5 S-CSCF I-CSCF S-CSCF I-CSCF 14 15 16 10 13 17 2 Visited B Visited A P-SCSF P-CSCF 11 12 18 1 GGSN GGSN SGSN SGSN Radio Access Network Radio Access Network B A Different Kinds of CSCFs