SIP ↠  ExamplesGrammarsPresence ⇾  MainServicesTransactionDialogIMS
TS 24.228§7.2.4§7.3.5§7.4.3   List   Prev   Next
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IMS S3 signalling flow - Session Initiation: Origination in CS Network, and Mobile termination in home network - sequence chart for IMS S3-1. SIP INVITE request (UE1 to UE2)
  • The MGCF in the IM subsystem is a SIP endpoint that initiates requests on behalf of the CS Networks origination and Media Gateway. The subsequent nodes consider the signalling as if it came from a S-CSCF. The MGCF incorporates the network security functionality of the S-CSCF. This MGCF does not invoke Service Control, as this may be carried out in the CS Networks or at the terminating S-CSCF.
  • The CS Network establishes a bearer path to the MGW, and signals to the MGCF with a IAM message, giving the trunk identity, destination information and optionally the continuity indication.
  • The MGCF initiates a H.248 command, to seize the trunk and an IP port.