MGCP Flows

It’s something I didn’t do in many many years, that’s why I create this post. Just for me to find all the information for the next time when I will have to configure MGCP.

 

MGCP Verbs :

Command Message Name Sent By Description
AUEP AuditEndpoint CallManager Get the status of a given endpoint.
AUCX AuditConnection CallManager Retrieves all the parameters associated with a connection.
CRCX CreateConnection CallManager Creates a connection between two endpoints.
DLCX DeleteConnection Both From CallManager:Terminates a current connection. From Gateway:Indicates that a connection can no longer be sustained.
MDCX ModifyConnection CallManager Changes the parameters (Update info) associated with an established connection.
RQNT NotificationRequest CallManager Instructs the gateway to watch for special events such as hooks or DTMF tones. It is also used to instruct the gateway to provide a signal to the endpoint (for example, dial tone and busy tone).
NTFY Notify Gateway Informs the Cisco CallManager when requested events occur.
RSIP RestartInProgress Gateway Informs the Cisco CallManager that an endpoint or group of endpoints are taken out or placed back into service.
EPCF Endpoint configuration Callmanager Alert configuration of the endpoint(things like gain level, codec, etc

Key Parameters :

X: Request id, RQNT/NTFY correlator

C: Callid, String

N: Notified entity (addr of call agent to be notified)

I: Connection id

S: Signal request(dialtone, ringback etc)

M : Connection mode (sendonly, recvonly, sendrecv)

T: Events to be detected (on/off hook, DTMF)

O: Events detected

R: Events requested

D: Digit map

B: Bearer Information (A-law, mu-law)

 

MGCP Flow

Here is a call between a SIP device and the FXS phone. The picture above is pretty correct. 😉

VG200 FXS (7777) calls SIP (1002)

Red is VG200, Blue is CUCM

 

NTFY 100785530 aaln/S0/0@VG202.homemade.nl MGCP 0.1
N: ca@192.168.5.2:2427
X: 52
O: L/hd

200 100785530 RQNT 100 AALN/S0/0@VG202.homemade.nl MGCP 0.1 X: 53 R: L/hu, D/[0-9ABCD*#] S: L/dl Q: process,loop

200 100 OK
NTFY 100785531 aaln/S0/0@VG202.homemade.nl MGCP 0.1
N: ca@192.168.5.2:2427
X: 53
O: D/1

200 100785531
RQNT 101 AALN/S0/0@VG202.homemade.nl MGCP 0.1
X: 54
R: L/hu, D/[0-9ABCD*#], L/hf
S:
Q: process,loop

200 101 OK
NTFY 100785532 aaln/S0/0@VG202.homemade.nl MGCP 0.1
N: ca@192.168.5.2:2427
X: 54
O: D/0

200 100785532

NTFY 100785533 aaln/S0/0@VG202.homemade.nl MGCP 0.1
N: ca@192.168.5.2:2427
X: 54
O: D/0

200 100785533

NTFY 100785534 aaln/S0/0@VG202.homemade.nl MGCP 0.1
N: ca@192.168.5.2:2427
X: 54
O: D/2

200 100785534

CRCX 102 AALN/S0/0@VG202.homemade.nl MGCP 0.1
C: A000000001a005ac000000F5
X: 55
L: p:20, a:PCMU, s:off, t:b8, fxr/fx:t38
M: recvonly
R: L/hu
Q: process,loop

200 102 OK
I: F
v=0
c=IN IP4 192.168.5.6
m=audio 19314 RTP/AVP 0 100
a=rtpmap:100 X-NSE/8000
a=fmtp:100 192-194,200-202
a=X-sqn:0
a=X-cap: 1 audio RTP/AVP 100
a=X-cpar: a=rtpmap:100 X-NSE/8000
a=X-cpar: a=fmtp:100 192-194,200-202
a=X-cap: 2 image udptl t38

RQNT 103 AALN/S0/0@VG202.homemade.nl MGCP 0.1
X: 56
R: L/hu
S: G/rt
Q: process,loop

200 103 OK

MDCX 104 AALN/S0/0@VG202.homemade.nl MGCP 0.1
C: A000000001a005ac000000F5
I: F
X: 57
L: p:20, a:PCMU, s:off, t:b8, fxr/fx:t38
M: sendrecv
R: L/hu, L/hf, D/[0-9ABCD*#], FXR/t38
S:
Q: process,loop
v=0
o=- 15 0 IN EPN AALN/S0/0@VG202.homemade.nl
s=Cisco SDP 0
t=0 0
m=audio 29092 RTP/AVP 0
c=IN IP4 192.168.5.117
a=X-sqn:0
a=X-cap:1 image udptl t38

200 104 OK

RQNT 105 AALN/S0/0@VG202.homemade.nl MGCP 0.1
X: 58
R: L/hu, D/[0-9ABCD*#], L/hf, FXR/t38
S:
Q: process,loop

200 105 OK

MDCX 106 AALN/S0/0@VG202.homemade.nl MGCP 0.1
C: A000000001a005ac000000F5
I: F
X: 59
M: recvonly
R: L/hu
Q: process,loop

200 106 OK

DLCX 107 AALN/S0/0@VG202.homemade.nl MGCP 0.1
C: A000000001a005ac000000F5
I: F
X: 5a
R: L/hu
S:
Q: process,loop

250 107 OK
P: PS=381, OS=60960, PR=377, OR=60320, PL=0, JI=7, LA=1
NTFY 100785535 aaln/S0/0@VG202.homemade.nl MGCP 0.1
N: ca@192.168.5.2:2427
X: 5a
O: L/hu

200 100785535
RQNT 108 AALN/S0/0@VG202.homemade.nl MGCP 0.1
X: 5b
R: L/hd
S:
Q: process,loop
200 108 OK

More information : http://www.cisco.com/c/en/us/support/docs/voice/media-gateway-control-protocol-mgcp/44130-understanding-mgcp.html

For debugging and decoding the messages : http://www.cisco.com/c/en/us/support/docs/voice-unified-communications/unified-communications-manager-callmanager/42104-debug-mgcp.html

http://docwiki.cisco.com/wiki/Cisco_IOS_Voice_Troubleshooting_and_Monitoring_–_MGCP_Overview#Figure:_MGCP_Call_Flow_Topology

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