mgcpoverview20050111-140621121817-phpapp01
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MGCP Overview(a VoIP protocol)
William.L
wiliwe@gmail.com
2005-01-11
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Agenda
Whats MGCP?
MGCP Internal
Basic Call Flows
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Whats MGCP?
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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)
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Master-Slave architecture
MGCP (2/2)
Media Gateway Media Gateway
IP network
Call Agent
MGCPMGCP
AnalogPhone A
AnalogPhone B
(RG, residential gateway)
RTP(Endpoint) (Endpoint)
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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 messagesare transmitted
over UDP.
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MGCP Internal
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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
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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 multipointsession
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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 SignalsTO, and detecting Events FROM endpoints
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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
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MGCP Return(Status) Codes
Failure due to a permanent error (ex:522no suchevent or signal)
(521 - redirect to another call agent)
500~599
Failure due to a transient error (ex:401already 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
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MGCP Digit Map Digit maps are provided to the gateway by the Call
Agent
Local operator
Long distance operatorLocal extension numberLocal numberShortcut to local number at other
corporate sitesStar services
Long distance numberInternational number
0
00xxxx8xxxxxxx#xxxxxxx
*xx
91xxxxxxxxxx9011 + up to 15 digits
(0T | 00T | [1-7]xxx | 8xxxxxxx | #xxxxxxx | *xx | 91xxxxxxxxxx | 9011x.T)
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Basic Call Flows
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MG Boot Up - Register to Call Agent
2. OK
3. AUEP
4. OK
1. RSIP
5. RQNT
6. OK7. RSIP
8. OK
9. AUEP
10. OK
11. RQNT
12. OK
Endpoint 1 MG-1 Call Agent MG-2 Endpoint 2
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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. OK15. MDCX
16. OK
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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 datausing RTP/RTCP)
20. RQNT
22. OK
21. Ring tone
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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 terminatedwhen MGs receive RTCP BYE
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