MGCP Overview

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Introduce MGCP, a VoIP protocol

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MGCP Overview

  1. 1. 1 MGCP Overview (a VoIP protocol) William.L wiliwe@gmail.com 2005-01-11
  2. 2. 2 Agenda What’s MGCP? MGCP Internal Basic Call Flows
  3. 3. 3 What’s MGCP?
  4. 4. 4 Media Gateway Control Protocol Media Gateway (MG) provides conversion between the audio signals (telephone circuits) and data packets (Internet) For controlling media gateway from call control elements Media Gateway Controller (MGC) Call Agent (CA) MGCP (1/2)
  5. 5. 5 Master-Slave architecture MGCP (2/2) Media Gateway Media Gateway IP network Call Agent MGCPMGCP Analog Phone A Analog Phone B (RG, residential gateway) RTP (Endpoint) (Endpoint)
  6. 6. 6 Streaming Multimedia Protocols - SIP, H.323, MGCP, RTSP, RTP, RTCP RTCPRTP IP MGCP Signaling Protocols Media Data Transport H.225 Q.931 H.323 TCP RAS UDP SIPH.245 Audio/ Video RTSP MGCP messages are transmitted over UDP.
  7. 7. 7 MGCP Internal
  8. 8. 8 MGCP Components Endpoints sources and sinks of data Connection point-to-point, multi-point ex: ATM, IP, PSTN… Event off-hook, on-hook, flash-hook, dialed digits … Signal dial tone, ringing, busy tone… Package group of signals and events ex: R:hu , S:dl …
  9. 9. 9 Connections Connections may be either point-to-point or multipoint Point-to-Point(p2p) connection Associates two endpoints. Once this association is established for both endpoints, data transfer between these endpoints can begin Multipoint connection Established by connecting the endpoint to a multipoint session
  10. 10. 10 Events & Signals The controlling primitives for MGCP operations are Signals sent from MGC to MG Events sent from MG to MGC The concepts of Signals and Events are used for establishing and tearing down calls Operations are performed by applying Signals TO, and detecting Events FROM endpoints
  11. 11. 11 MGCP Commands(Methods) RQNT - Notification Request NTFY - Notify CRCX - Create Connection MDCX - Modify Connection DLCX - Delete Connection AUEP - Audit Endpoint RSIP - Restart In Progress AUCX - Audit Connection EPCF - Endpoint Configuration
  12. 12. 12 MGCP Return(Status) Codes Failure due to a permanent error (ex:522 – no such event or signal) (521 - redirect to another call agent) 500~599 Failure due to a transient error (ex:401 – already off- hook) 400~499 Command Successful (ex: 200) (250 -- only for DLCX) Provisional responses; a final response will follow later (ex: 100) 200~299 100~199
  13. 13. 13 MGCP Digit Map Digit maps are provided to the gateway by the Call Agent Local operator Long distance operator Local extension number Local number Shortcut to local number at other corporate sites Star services Long distance number International number 0 00 xxxx 8xxxxxxx #xxxxxxx *xx 91xxxxxxxxxx 9011 + up to 15 digits (0T | 00T | [1-7]xxx | 8xxxxxxx | #xxxxxxx | *xx | 91xxxxxxxxxx | 9011x.T)
  14. 14. 14 Basic Call Flows
  15. 15. 15 MG Boot Up - Register to Call Agent 2. OK 3. AUEP 4. OK 1. RSIP 5. RQNT 6. OK 7. RSIP 8. OK 9. AUEP 10. OK 11. RQNT 12. OK Endpoint 1 MG-1 Call Agent MG-2 Endpoint 2
  16. 16. 16 Create a Call (1/2) Endpoint 1 MG-1 Call Agent MG-2 Endpoint 2 3. OK 2. NTFY 19. OK 18. RQNT 1. Off hook 4. Dial tone 4. RQNT 5. OK 6. Press Digits 7. NTFY 8. OK 10. OK 9. CRCX 17. Ring 11. CRCX 12. OK 13. MDCX 14. OK 15. MDCX 16. OK
  17. 17. 17 Create a Call (2/2) Endpoint 1 MG-1 Call Agent MG-2 Endpoint 2 24. NTFY 23. Off hook 29. Remove ring tone 25. OK Start media session (transport Audio/Video data using RTP/RTCP) 20. RQNT 22. OK 21. Ring tone
  18. 18. 18 Terminate a Call Endpoint 1 MG-1 Call Agent MG-2 Endpoint 2 3. OK 2. NTFY 9. NTFY 4. DLCX 1. On hook 5. DLCX 7. OK 11. RQNT 12. OK 8. On hook 6. OK 10. OK 13. RQNT 14. OK Media session is terminated when MGs receive RTCP BYE

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