Internet Telephony 1 Reference Architecture of R00

Internet Telephony 2 Support of Roaming Subscribers via the service platform in the Home Network via an external service platform

Internet Telephony 3 UE Accessing IM Subsystem Services In the visited network

Internet Telephony 4 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

Internet Telephony 5 Relationship of Private and Public User Identities

Internet Telephony 6 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

Internet Telephony 7 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

Internet Telephony 8 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

Internet Telephony 9 Registration Information Flow

Internet Telephony 10 Re-Registration

Internet Telephony 11 NodeBefore RegistrationDuring RegistrationAfter Registration UE - in local networkCredentials Home Domain Proxy Name/Address Same as before registrationCredentials Home Domain Proxy Name/Address Proxy ‑ CSCF - in Home or Visited network Routing FunctionInitial Network Entry point UE Address Public and Private User IDs Final Network Entry point UE Address Public and Private User IDs Interrogating ‑ CSCF - in Home network HSS or SLF Address Serving ‑ CSCF address/name P ‑ CSCF Network ID Home Network contact Information No State Information HSSUser Service Profile P ‑ CSCF Network IDServing ‑ CSCF address/name\ Serving ‑ CSCF (Home) No state informationHSS Address/name User profile (limited – as per network scenario) Proxy address/name P ‑ CSCF Network ID Public/Private User ID UE IP Address May have session state Information Same as during registration

Internet Telephony 12 De-registration

Internet Telephony 13 Call flow

Internet Telephony 14

Internet Telephony 15 Different Kinds of CSCFs P-SCSF Visited B S-CSCF Home A P-CSCF Visited A 18 AB GGSN SGSN Radio Access Network GGSN SGSN Radio Access Network S-CSCF Home B 8 I-CSCF HSS I-CSCF HSS 5 16

Internet Telephony 16 PSTN origination procedure

Internet Telephony 17 PSTN origination procedure

Internet Telephony 18 PSTN termination procedure

Internet Telephony 19 PSTN termination procedure