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IMS User to IMS User Call Flow

Call from an IMS user to another IMS user

A detailed IMS subscriber to IMS subscriber is presented here. The preconditions for this call flow are:

  • The calling IMS subscriber is currently roaming outside the home network.
  • The called user is registered in the home network.
  • The caller and the called user require resource reservation before the call can be setup.

The major steps in the call flow are:

  • IMS routing of the initial SIP INVITE.
  • IMS routing of the first response to the INVITE.
  • Resource allocation via PDP context activation.

IMS (IP Multimedia Subsystem) user calls another IMS user