IMS to PSTN Call Flow Poster - EventHelix.com

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IMS Originating to PSTN ISUP Call (IMS-PSTN(ISUP) Call; Megaco/H.248 Signaling; IMS Caller Initiated Call Release)Calling UE IMS Core Network PSTN InterfaceCaller User Visited IMS Home IMS Signaling MediaEquipmentCaller Orig P-CSCF Orig S-CSCF BGCF MGCF IM-MGWEventStudio System Designer 624-Feb-13 15:23 (Page 2)Caller Media PDP Context ActivationSelect the Codec indicated in 183Session ProgressSelected CodecPRACKThe Caller confirms the codec selection in PRACK towardsMGCF.beginCaller PDP Context ActivationH.248: MOD.reqContext = C1,Termination = RTP1,Selected CodecThe MGCF modifies the IM-MGW context to update the IM-MGWabout the codec selected for the RTP session.Configure IMS resourcesH.248: MOD.respContext = C1,Termination = RTP1IM-MGW responds back.Selected Codec,Selected UDP Port,Selected IP Address200 OK (PRACK)The codec selected is acknowledged to the UE.endCaller PDP Context ActivationUPDATESince caller PDP Context Activation is over, notify the called endin UPDATE message.200 OK (UPDATE) The called end replies back with 200 OK.ISUP COTBased on the continuity support of the outgoing channelselected MGCF sends a COT message to the PSTN network.RingingISUP ACMThe path towards the called party is allocated in the PSTNnetwork and address complete message, ACM containingsubscriber free indication is sent to MGCF. The ACM messagealso indicates that the called party in the PSTN network is beingalerted.180 Ringing The MGCF forwards called party alerting indication in 180ringing message towards the Caller.Ring BacRTP: Ring Back TonePRACKRing BacThe ring back tone is fed to the calling subscriber. The IM-MGWconverts the tone into RTP. The UE converts it back to the ringback tone and feeds it to the calling subscriber.The Caller acknowledges the 180 ringing with PRACK messagetowards MGCF.200 OK (PRACK) The MGCF acknowledges the PRACK message with 200 OKmessage.Conversation ModeISUP ANMH.248: MOD.reqContext ID = C1,Termination ID = RTP1When the called party answers, the terminating PSTN networksends answer, ANM message towards MGCF.Request a bidirectional through connectionChange IMS Through Connection =bothH.248: MOD.respContext ID = C1,Termination ID = RTP1H.248: MOD.reqContext ID = C1,Termination ID = TDM1Request activation of TDM voice processing function.Activate TDM Voice ProcessingFunctionH.248: MOD.respContext ID = C1,Termination ID = TDM1200 OK (INVITE) The final response, 200 OK, is sent by the MGCF over thesignaling path when the subscriber has accepted the incomingsession attempt.ACKThe Caller sends the final acknowledgement in ACK messagetowards MGCF.VoiceRTP: VoiceVoiceBidirectional voice path is now through. The IM-MGW convertsRTP to voice and vice versa. UE also maps audio to RTP andback.BYEThe Caller sends BYE towards MGCF when the calling partyhangs up.Drop media PDP context200 OK (BYE) The MGCF acknowledges with 200 OK message towards Caller.
IMS Originating to PSTN ISUP Call (IMS-PSTN(ISUP) Call; Megaco/H.248 Signaling; IMS Caller Initiated Call Release)Calling UE IMS Core Network PSTN InterfaceCaller User Visited IMS Home IMS Signaling MediaEquipmentCaller Orig P-CSCF Orig S-CSCF BGCF MGCF IM-MGWRelease IMS TerminationISUP RELH.248: SUB.reqContext ID = C1,Termination ID = RTP1EventStudio System Designer 624-Feb-13 15:23 (Page 3)The MGCF initiates call release in the PSTN network by sendingISUP REL message.MGCF requests IM-MGW to release RTP1 resource.H.248: SUB.respContext ID = C1,Termination ID = RTP1Release TDM TerminationMGCF requests IM-MGW to release TDM1 resource.H.248: SUB.reqContext ID = C1,Termination ID = TDM1H.248: SUB.respContext ID = C1,Termination ID = TDM1ISUP RLCThis sequence diagram was generated with EventStudio System Designer (http://www.EventHelix.com/EventStudio).The PSTN network acknowledges the call release with ISUPRLC, release complete towards MGCF.
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IMS to PSTN Call Flow Poster - EventHelix.com

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