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Voice over IP, IP Telephony

Voice over IP, IP Telephony. Allan Jost MEI Program, Feb 2000. The PSTN: Separate Voice and Signaling Networks. SS7. Voice. SSP. SSP : Service Switching Point (Telephone Switch) STP : Signaling Transfer Point (Router) SCP : Service Control Point (Database, Logic). STP. Trunk. SCP.

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Voice over IP, IP Telephony

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  1. Voice over IP,IP Telephony Allan Jost MEI Program, Feb 2000

  2. The PSTN: Separate Voice and Signaling Networks SS7 Voice SSP • SSP: Service Switching Point (Telephone Switch) • STP: Signaling Transfer Point (Router) • SCP: Service Control Point (Database, Logic) STP Trunk SCP SSP Signaling (Packet) Trunk (TDM) Trunk STP SSP

  3. OMAP ASEs Application TCAP ISUP Presentation Session Transport SCCP Network MTP Level 3 Data Link MTP Level 2 Physical MTP Level 1 SS7 Protocol Stack

  4. ISUP Call Control Originating Switch Terminating Switch Calling Party Called Party IAM (dialed #, CIC, etc.) (Dials) ACM (Hears ring) (Ringing) ANM (Answers) (Connected) REL (Hangs Up) RLC (Disconnected, trunks released) ISUP used between Switches only

  5. Ideal IP Telephony IP Phone IP Phone “Converged” Network Soft-Phone IP Phone Call Manager IP Phone

  6. Carrier Model POTS Phones POTS Phones Managed IP Network Analog, ISDN CO Switch IP CO Switch IP Media Gateway Signaling Gateway PSTN SS7 TDM

  7. Enterprise Model IP Phones PSTN Corporate LAN IP Phones ISDN PRI Corporate WAN Gateway IP Call Manager Gateway Branch Office LAN Call Manager PSTN ISDN PRI

  8. Enterprise Level VoIP (CISCO)

  9. Some VoIP Protocols • H.323 • Umbrella ITU Spec • SIP, SDP • IETF Open standards • MGCP • Tie various gateways together (Considerable Overlap, competition)

  10. H.323 Protocols • Audio Codecs • Video Codecs • H.225 Registration, Admission and Status • H.225 Call Signaling • H.245 Control Signaling • RTP - Real Time Protocol • RTCP - Real-Time Control Protocol

  11. ITU Voice Encoding

  12. H.323 Components • Terminal • Gateways • Gatekeeper • MCU

  13. H.323 Terminal

  14. H.323 Gateway

  15. H.323 Gateway

  16. H.323 Gatekeeper

  17. Mandatory Gatekeeper Functions Address Translation Admission Control Bandwidth Control Zone Management Optional Gatekeeper Functions Call-Control Signaling Call Authorization Call Management H.323 Gatekeeper

  18. H.323 MCU

  19. H.323 Call Setup • Phase A - Call Setup • Call Setup: Non Registered Endpoints • Call Setup: Registered Endpoints • Gateway Outbound Call Setup • Phase B - Initial Communication and Capability Exchange • Capability Exchange • Master/Slave Determination

  20. H.323 Call Setup • Phase C - Establishment of Audiovisual Communication • Opening Logical Channels • Mode Change • Phase D - Call Services • Bandwidth Changes • Status Changes • Ad Hoc Conference Expansion • Other services • Phase E - Call Termination

  21. Q.931 Call Setup & Tear down Terminal Network SETUP CALL PROCEEDING ALERTING CONNECT CONNECT ACK (Call Established) DISCONNECT RELEASE RELEASE COMPLETE (Call Ended)

  22. H.323 Call Setup Calling End Called End Q.931 TCP Connection SETUP ALERTING CONNECTED H.245 TCP Connection H.245 Messages RTCP Address RTP and RTCP Addresses RTCP Address RTP and RTCP Addresses Duplex RTP Session RTCP Session

  23. H.323 Call Tear Down Calling End Called End End Session End Session Q.931 TCP Disconnect H.245 Messages H.245 TCP Disconnect

  24. Some Issues • Number mapping • Directory services • QoS • Provisioning • Billing, Administration • Interworking • Protocol Conversion • Media Conversion

  25. It’s Here Now!

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