IMS Signalling flows for session initiation: Non Hiding
MO#2 / S-S#2 / MT#2 (page 3 of 3)
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Mobile Origination, located in home network
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Single Network Operator performing Origination and Termination
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Mobile Termination, located in home network
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Before proceeding with session establishment, UE2 waits for two events. First, the resource
reservation initiated in step #4 must complete successfully. Second, the resource reservation initiated
by the originating endpoint must complete successfully (which is indicated by message UPDATE received by
UE1). UE2 may now alert the
destination subscriber of an incoming session attempt; it indicates this to the calling party by
a 180 Ringing provisional response sent to P-CSCF2.
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Record-Route:
P-CSCF2 rewrites the Record-Route header field value to remove the port number and the
comp=sigcomp parameter from its own entry.
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Record-Route:
P-CSCF1 rewrites the Record-Route header to add the comp=sigcomp parameter to its
own SIP URI and its port number negotiated during the security agreement.
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Request-URI:
Takes the value of the Contact header of the received 180 Ringing response.
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Security-Verify:
Contains the security agreement as represented by the received Security-Server header.
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When the called party answers, UE2 sends a 200 OK final response to the INVITE request to P-CSCF2,
and starts the media flow(s) for this session.
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P-CSCF2 approves the commitment of the QoS resources if it was not approved yet.
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