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					IWF and CCF for VoIP Protocols

         Ming-Feng Chang
            Professor
          CSIE, NCTU


                                 1
                       VoIP

• Voice over IP
  – transport of telephone calls using IP
  – telephony devices, multimedia PCs or dedicated
    terminals
• The benefits
  – a single infrastructure for Internet access and
    Internet telephony
  – saving money
  – easily integrated with other services and
    applications

                                                      2
• The problems
  – lower quality of voice over IP
     • higher delay and jitter
  – accounting, billing, charging, roaming etc. remain
    open
  – Interworking functions
     • ISUP, Q.sig, H.323, SIP and MGCP/MEGACO




                                                         3
       A Converged Network Architecture

• ICA – integrated call agent
  – A GK, SIP proxy server, and CA/MGC




                                          4
       The Interworking Functions

• PSTN
  – ISUP, Q.sig
• IP networks
  – H.323, SIP
• MGCP/MEGACO
  – Trunking gateways
  – Access gateways
  – Residential gateways
• Communication between any devices
  – The interworking function
                                      5
     Half-Call Call State Model of IN

• Originating FSM
• Terminating FSM




  – The switching system - an MGC or IWF

                                           6
          The Interactions of the FSMs


                                   8.Abandon
8. O_Ex   1. O_Null     7. O_Ab
                         1.Setup                1. T_Null    6. T_Ex

          2. Col_Info
                          2.Busy               2. Sel_Fac
          3. Ana_Info
                           3.Alert
                                               3. T_Alert
                             4.NoAns
          4. Routing
                              5.Answer         4. T_Active

          5. O_Active     6.Disconnect
                                                5. T_Dis
                          7.Disconnect
           6. O_Dis
                                                                       7
                The Interactions (Normal)


8. O_Ex   1. O_Null     7. O_Ab
                         1.Setup           1. T_Null    6. T_Ex

          2. Col_Info
                                          2. Sel_Fac
          3. Ana_Info
                           3.Alert
                                          3. T_Alert
          4. Routing
                              5.Answer    4. T_Active

          5. O_Active      6.Disconnect
                                             5. T_Dis
                           7.Disconnect
             6. O_Dis
                                                                  8
                  The Interactions (Fail)


8. O_Ex   1. O_Null     7. O_Ab
                                        1. T_Null    6. T_Ex

          2. Col_Info
                          2.Busy       2. Sel_Fac
          3. Ana_Info
                                       3. T_Alert
                             4.NoAns
          4. Routing
                                       4. T_Active

          5. O_Active                     5. T_Dis

             6. O_Dis
                                                               9
                   An Interworking Architecture

      • We have developed half-call BCSMs
            – SIP, H.323, MGCP, and MEGACO



             SIP Messages       SIP                       SIP      SIP Messages
SIP user agent                O_BCSM                    T_BCSM                    SIP user agent
                                            Events
             H.323 Messages    H.323                     H.323     H.323 Messages
H.323 endpoint                O_BCSM                    T_BCSM                   H.323 endpoint

            MGCP Messages      MGCP                      MGCP      MGCP Messages
      MGW                     O_BCSM                    T_BCSM                 MGW
                              Originating            Terminating
                               BCSMs                   BCSMs




                                                                                      10
      The Integrated IWF and CCF

• Integrate CA/MGC, GK and SIP proxy server
       Q.931                    Q.931
       OFSM                     OFSM
               Events
       MGCP    • busy           MGCP
       OFSM    • alerted        TFSM
               • no answer
        SIP                      SIP
               • answered
       OFSM                     TFSM
               • disconnected
       H323    • abandoned      H323
       OFSM    • suspend        TFSM
               • resume
       ISUP                     ISUP
       OFSM                     TFSM

                                              11
               SIP-H323 IWF

• The IWF for SIP and H.323
  – A GK and SIP proxy server

         SIP                       H323
        OFSM                       TFSM

         SIP                       H323
        TFSM                       OFSM

                  Events
                  • busy
                  • alerted
                  • no answer
                  • answered
                  • disconnected
                  • abandoned             12
           VoIP Gateways

• H.323, SIP and MEGACO/MGCP




                               13
The Integrated CA Design

                   SIP
                  TFSM

 MGCP             H323
 OFSM             TFSM

                  ISUP
                  TFSM

                  SIP
                 OFSM

 MGCP            H323
 TFSM            OFSM

                 ISUP
                 OFSM
                           14
           MGCP-SIP IWF/GW

• Inter-CA and intra-CA call setup
          MGCP                  SIP
          OFSM                 TFSM


            Intra-CA                 Inter-CA


          MGCP                 SIP
          TFSM                OFSM




                                                15
          Inter-zone Communications

• Support inter-ICA call setup

Zone 1                      Zone 2
          ICA 1                        ICA 2
                      SIP
  H.323        SIP             SIP         MGCP
 O_BCSM      T_BCSM          O_BCSM       T_BCSM


                             Media
                             Gateway

  H.323



                                                   16
          MGCP Half-Call Model

NTFY:HD
RQNT              O_Null                                 T_Null


NTFY:digits    O_Collec_Info                         T_Present_Call   CRCX:RG
                                            Alert
CRCX:reconly                   Setup                   T_Alerting     NTFY:HD
MDCX:RT         O_Routing
MDCX:sendrec                                                          MDCX:
                                            Answer
                                                       T_Active

NTFY:HU          O_Active
                                                                      DLCX:E
                               Disconnect            T_Disconnect
DLCX           O_Disconnect




                                                                                17
           H.323 Half-Call Model

Setup
               O_Null                                 T_Null
                                                                   Setup
CallProc
            O_Collec_Info                         T_Present_Call   CallProc
                                         Alert                     Alert
Alert                       Setup                   T_Alerting     Connect
             O_Routing
                                                                   H.245 EX
                                         Answer
Connect                                             T_Active
                               SDP
H.245 EX      O_Active
                                                                   Release
                            Disconnect            T_Disconnect
Release     O_Disconnect




                                                                              18
              SIP Half-Call Model
INVITE (SDP)
100 Trying        O_Null                                 T_Null
                                                                      INVITE (SDP)
               O_Collec_Info                         T_Present_Call   100 Trying
                                            Alert                     180 Ringing
                               Setup                   T_Alerting     200 OK (SDP)
180 Ringing
                O_Routing
                                                                      ACK
                                            Answer
200 OK (SDP)                                           T_Active

ACK              O_Active
                                                                      BYE
BYE                            Disconnect            T_Disconnect
200 OK         O_Disconnect                                           200 OK




                                                                               19
                 MEGACO Half-Call Model
Notify:of
Modify:digitmap,on       O_Null                           T_Null


NTFY:digits           O_Collec_Info   Setup(sdp1)     T_Present_Call   Add:ri,sendrec,sdp1
                                              Alert                        Reply:sdp2
Add:rt,reconly
                                                        T_Alerting     Notify:of
    Reply:sdp1
                       O_Routing
Modify:sendrec,sdp2                   Answer(sdp2)                     Modify: ,on
                                                        T_Active

Notify:on               O_Active
                                      Disconnect
                                                                       Subtract:ct,on
                                                      T_Disconnect
Subtract:of           O_Disconnect




                                                                                   20
                MGW FSMs

• Media Gateways
  – Trunking GWs
  – Access GWs
  – Residential GWs
• OFSMs and TFSMs
  – For TGWs, AGWs, and RGWs




                               21
                Examples

• Our VoIP platform




                           22
               Examples

• Communications between any devices




                                       23
                Conclusions

• The interworking functions are important
  – ISUP, Q.sig, H.323, SIP and MGCP/MEGACO
• Half-call model
  – For the integrated IWF and CCF
• Gateway selection?
  – iptel
• Mobility support?




                                              24

				
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posted:7/28/2013
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