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SIP ↠  ExamplesGrammarsPresence ⇾  MainServicesTransactionDialogIMS
TS 24.228§7.2.2§7.3.2§7.4.2   List   Prev   Next
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IMS S1 signalling flow - Session Initiation: Mobile origination and termination roaming, with different network operators - IMS S1-1b. SIP INVITE request (UE1 to UE2): from P-CSCF1 to S-CSCF1
  • P-CSCF1 adds itself to the Record-Route header and Via header. As the request is forwarded to an interface that is not compressed, the own P-CSCF SIP URI does not contain the "comp=sigcomp" parameter.
  • P-CSCF1 removes the Security-Verify header and associated "sec-agree" option-tags prior to forwarding the request. As the Proxy-Require header is empty, it removes this header completely.
  • P-Asserted-Identity: P-CSCF1 inserts the SIP URI in the P-Asserted-Identity header field and it also removes P-Preferred-Identity header field.
  • P-Charging-Vector: P-CSCF1 inserts this header and populates the icid parameters with a globally unique value.
  • S-CSCF#1 validates the service profile of this subscriber and evaluates the initial filter criterias. For this example, assume no Application Server involvement.