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ISSUE
Fixed Network Curriculum
Development Section
2.0
OAA000004 Bearer controlprotocol MGCP protocol
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Objective
MGCP functions
MGCP commands
Meanings and usage of the
parameters in MGCP commands
MGCP message interaction process
After this session, you will learn:
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References
Product Manual -- Technical Manual -- Signaling and
Protocols -- MGCP
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About this session
Section 1 Overview
Section 2 Message Structure
Section 3 Call Flow
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Bearer Control Protocols
Bearer control protocols are used for the communication
between a Media Gateway Controller (MGC) and a Media
Gateway (MG).
As control-layer equipment, SoftX3000 supports two bearercontrol protocols:
MGCP and H.248.
MGC MG
IP DATA
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Concept
MGCP : Media Gateway Control Protocol
assumes a call control structure in which the call control
functions are gateway-independent and are processed by the
external call control unit.
a master/slave protocol. The gateway needs to execute the
commands sent from the MG controller.
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Terms
Gateway
Gateway : a network element that provides interconnection and inter-
working between networks of various architectures. In NGN architecture,
NGN inter-works with other networks via certain gateways.
Trunk Media Gateways (TMG): It provides the interfaces between the
traditional telephone network (PSTN) and a Voice over IP (VoIP)
network.
Access Media Gateways (AMG): It provides a traditional analog
subscriber line interface or a digital PBX interface to a Voice over IP
network.
Residential Gateways (RG): It is an entity that provides traditional
analog (RJ11) interfaces to VoIP network. Examples of residential
gateways include cable modem/cable set-top boxes, xDSL devices, and
broadband wireless devices
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Terms
Call Agent :
handles the signaling and call processing functions, and it is
external call control element controlling Telephony Gateways.
SoftX3000 system provides MGCP call agent functions. SoftX3000
can act as the access point for MGCP E-phones and softphones in
the network.
End point:
It refers to the originating end or receiving end of data. It can be a
physical concept or a virtual concept.
Media Resource Server (MRS):
It is a type of gateway that supports endpoint types such as
announcement server access point, interactive voice response
access point, conference bridge access point, etc.
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Terms
Terminal nameincludes
Domain name of the gateway
Interface name of the terminal in gateway
@is use to seperate domain name and interface name, theform is like Email address
Examples:
AGaaln/1 @ amg1.hauwei.comrefers to the first interface
named aaln in AG named amg1.hauwei.com
TGX35V3+A4/[email protected] refers to the 13th
TDM circuit on interface X35V3+A4 which is in
gw23.example.net
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Terms
Call connection:
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MGCP Implementation in SoftX3000
PSTN
SoftPhone
TMG8010
MRS
IAD
E-phone E-phone
IP Core
SS7
E1
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Inter-working Support
SoftX3000 supports interworking between MGCP and the following protocols:
SIP: SIP User and SIP trunk;
H.323: H.323 User and H.323 Trunk
ISUP: PSTN user through ISUP trunk
SIP
PSTN
IP Core
H.323
SIP Terminal
H.323 Terminal
SIP
H.323
ISUP
IAD
MGCP
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Protocol Stack
MAC
MGCP
IPUDP
SM (ISUP/TUP/SIP/H.323/ESL)
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About this session
Section 1 Overview
Section 2 Message Structure
Section 3 Call Flow
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Message Types:
MGCP messages exchanged between MGC and MG have 9
types
they are called commands when being sent to MG or MGC,
while called responses when being returned from MG orMGC.
Command and response are inseparable. Upon receiving a
command, MG (or MGC) will return a response immediately.
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Command Line
A command line is composed of
the name of the requested verb (command name)
the identification of the transaction,
the name of the endpoint (entity)
the protocol version. These four items are separated by spaces.
Command
name
Identification
of transaction
End point
Parameter: Parameter value:
Parameter: Parameter value:
...
Protocol versionCommand
line
Parameter
line
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Command Name
Item Command Name Code Description
1Endpoint
ConfigurationEPCF
MGCMG, used to inform the gateway about the
coding characteristics expected by the "line-side" of
the endpoint.
2 CreateConnection CRCX
MGCMG, used by call agent to associate an end
point with a specified IP address and UDP port.
Apart from that, a CreateConnection command is
also sent to the remote endpoint to create the
connection between the two endpoints.
3 ModifyConnection MDCXMGCMG, used to change the parameters of a
previously established connection.
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Command Name
Item Command Name Code Description
4 DeleteConnection DLCXMGCMG, used to delete a
previously established connection.
5 NotificationRequest RQNT
Used to instruct the gateway to
watch for specific events on a
specified endpoint. If it happens, the
Call Agent will be notified.
6 Notify NTFY
MGMGC, used by the gateway to
notify the Call Agent that a specific
event requested to watch for takes
place
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Command Name
Item. Command Name Code Description
7 AuditEndpoints AUEP
MGCMG, used by the Call Agent to
obtain the detailed information of an
end point or a group of endpoints
8 AuditConnection AUCX
MGCMG, used by the Call Agent to
obtain the detailed information of a
connection on an end point
9 RestartInProgress RSIP
MGMGC, used by the gateway to
notify the Call Agent that an end point
is getting out of or into service
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Command Example
RQNT 4561 [email protected] MGCP 1.0
N: [email protected]: 5777
X: 45848484
R: hd
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Command Response Format
The response line consists of :
the response code
Values between 200 and 299 indicate a successful completion.
Values between 400 and 499 indicate a transient error.
Values between 500 and 599 indicate a permanent error.
transaction identifier
an optional commentary, which are separated by white spaces.
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Command Response Example
200 1203 OK
C: A3C47F21456789F0
N: [128.96.41.12]
L: p: 10, a: PCMU; G726-32
M: sendrecv
P: PS=1245, OS=62345, PR=780, OR=45123, PL=10,
JI=27,LA=48
v=0
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Command Response Example (Cont.)
c=IN IP4 128.96.41.1
m=audio 1296 RTP/AVP 0
v=0
c=IN IP4 128.96.63.25
m=audio 1296 RTP/AVP 0 96
a=rtpmap:96 G726-32/8000
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About this session
Section 1 Overview
Section 2 Message Structure
Section 3 Call Flow
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Scenario 1MG Registration
SoftX3000MG
RSIP
RSIP_RSP
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Scenario 2 - Successful Call
User MG SoftX3000 MG User
1 RQNT
ACK
2 NTFY
ACK
3 RQNT
ACK
4 NTFY
ACK
5 CRCX
ACK
8 RQNT
Off-hook
ACK
Dail tone
Ringbacktone
6 CRCX
ACK
Ringing
Off-hook9 NTFY
ACK
Dailing
7 RQNT
ACK
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Scenario 2 - Successful Call (continued)
User MG SoftX3000 MG User
11 MDCXACK
16 NTFY
ACK
13 DLCX
ACKBusy tone
14 DLCX
ACK
On-hook12 NTFY
ACK
On-hook
10 MDCX
ACK
CONVERSATION
15 RQNT
ACK
17 RQNT
ACK
13 MDCX
ACK
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Scenario 3 - Unsuccessful Call Flow
User MG SoftX3000 MG User
1 RQNT
ACK
2 NTFY
ACK
3 RQNT
ACK
4 NTFY
ACK
5 RQNT
ACK
Off-hook
Dail tone
Dailing
Busy tone
On-hook 6 NTFY
ACK
7 RQNT
ACK
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Summary
Concept and function of MGCP: The MGCP protocol is used
for communication between MGC and MG. It is a bearer
control protocol.
MGCP includes 9 commands and 3 types of responses. Eachcommand consists of 4 parts; values 200~299 indicate
success, and the other values indicate failure.
The role of each command in MGCP call flow must be
mastered as the key point.
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