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H.323 Packet-based multimedia communications systems

H.323 Packet-based multimedia communications systems. Speaker: Yi-Lei Chang Advisor: Dr. Kai-Wei Ke 2012/11/28. Outline. Introduction Protocol Stack Elements Call signalling procedures. Introduction. 1996

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H.323 Packet-based multimedia communications systems

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  1. H.323 Packet-based multimedia communications systems Speaker: Yi-Lei Chang Advisor: Dr. Kai-Wei Ke 2012/11/28

  2. Outline • Introduction • Protocol Stack • Elements • Call signalling procedures

  3. Introduction • 1996 • ITU-T (Telecommunication Standardization sector of International Telecommunication Union) • Packet-based multimedia communications systems

  4. Protocol Stack

  5. Additional Documents • H.235 Security within H.245-based systems • H.450.x Supplementary services • H.460.x Various H.323 protocol extensions • H.501 Protocol for mobility management and inter/intra-domain communication • H.510 User, terminal, and service mobility • H.530 Security specification for H.510

  6. Elements • Terminals • Gateways • Gatekeeper • MC, MP, MCU • Multipoint controller • Multipoint processor • Multipoint control unit

  7. Terminals • Telephones, Video phones, etc. • Soft phones • G.711 (voice) • H.261 (video, optional)

  8. Gateway • Interface H.323 to other networks • PSTN • H.320 systems • other H.323 networks (proxy) • etc.

  9. Gatekeeper • Optional element • H.225.0 RAS • Address Translation • Admissions Control • Bandwidth Control • Zone Management • Optional • Call Control signalling • Call Management

  10. MC, MP, MCU • Multipoint controller • Provides control functions to support conferences between three or more endpoints in a multipoint conference • Multipoint processor • Handle media mixing, switching, or other media processing • Multipoint control unit • An endpoint which provides support for multipoint conferences • The MCU shall consist of an MC and zero or more MPs

  11. MC, MP, MCU

  12. H.255.0 RAS • Registration, Admission, and Status • Used between the endpoint and its Gatekeeper • RAS Port • 1719 (unicast) • 1718 (multicast) for GRQ, LRQ • RAS messages generally have three types • Request (xRQ) • Reject (xRJ) • Confirm (xCF) • x can be • G:GatekeeperR:Registration • A:AdmissionsL:Location • D:DisengageU:Unregistration • IRQ (Information Request), IRR (Information Request Response)

  13. Call signalling procedures • Phase A: Call setup. • H.225.0/Q.931 Call control , H.225.0 RAS (if reg. to a gatekeeper) • Phase B: Initial communication and capability exchange • H.245 Multimedia control, H.225.0/Q.931 Call control • Phase C: Establishment of audiovisual communication • H.245 Multimedia control, RTP, RTCP • Phase D: Call services • Status, Bandwidth changes, Conference expansion • Phase E: Call termination • H.225.0/Q.931 Call control, H.245 Multimedia control (optional), H.225.0 RAS (if reg. to a gatekeeper)

  14. Phase A: Call setup • Notify user, setup H.245 channel • Caller/Callee registered to Gatekeeper? • Routed/direct call? (if reg. to a Gatekeeper) • Simple call setup:

  15. Phase A: Call setupCaller/Callee registered to Gatekeeper

  16. Phase A: Call setupCaller routed call

  17. Phase A: Call setupCallee routed call

  18. Phase A: Call setupAn example • Endpoint 1 • registered to gatekeeper 1 • Gatekeeper 1 • use direct call • Endpoint 2 • registered to gatekeeper 2 • Gatekeeper 2 • use routed call

  19. Phase B: Initial communication and capability exchange • Capability exchange • Master Slave Determination

  20. Phase C: Establishment of audiovisual communication

  21. Phase D: Call services • Status • IRQ, IIR • Interval > 10 sec. • Bandwidth changes • BRQ, BCF, BRJ • closeLogicalChannel, openLogicalChannel, flowControlCommand • Conference expansion • Create • Invite • Join

  22. Phase E: Call termination • Terminate a call • Discontinue transmission of video, data, audio and then close all logical channels for them • Transmit the H.245 endSessionCommand (optional) • Close H.245 Control Channel • Transmit a Release Complete message and close the H.225.0 call signalling channel • Terminate a conference • H.245 message dropConference • Wait for MC to terminate calls • Call clearing with a gatekeeper • Call clearing by gatekeeper

  23. Phase E: Call terminationCall clearing with a gatekeeper

  24. Phase E: Call terminationCall clearing by gatekeeper

  25. Reference [1] International Telecommunication Union, "Packet-based Multimedia Communications Systems," Recommendation H.323, Telecommunication Standardization Sector of ITU, December 2009. [2] International Telecommunication Union, "Call signalling protocols and media stream packetization for packet-based multimedia communication systems," Recommendation H.225.0, Telecommunication Standardization Sector of ITU, December 2009. [3] International Telecommunication Union, "Control protocol for multimedia communication," Recommendation H.245, Telecommunication Standardization Sector of ITU, May 2011.

  26. Thanks for Listening Q&A

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