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MGCP | Cisco Collaboration

MGCP Common Messages

Here are some MGCP messages that you can see in the interaction between the Call Agent and the endpoint:

  • EndpointConfiguration (EPCF) : A Call Agent sends this message to a gateway to specify signal encoding that will be received by an endpoint . A good example of these message will be the audio encoding using ulaw or alaw.
  • CreateConnection (CRCX) : This command creates a connection between 2 endpoints. the connection is created based on parameters included with the commad such as codec , allowable bandwidth, use of echo cancellation, silence suppression , gain control, and so on.
  • ModifyConnection (MDCX) : This is used to modify the parameters associated with a connection that was previously created.
  • DeleteConnection (DLCX) : The Call Agent can send this command to inform a gateway that it should terminate a connection, and a gateway can send this command to indicate that a connection can no longer be sutained. In response to a DeleteConnection, an endpoint sends statistics associated with the connection.
  • NotificationRequest (RQNT) : This is sent by the Call Agent to instruct a gateway to informit when specific events occur in an endpoint. Example : be on-hook/off-hook, tones,..
  • Notify (NTFY) : An endpoint uses this command to inform a Call Agent when requested events occur
  • AuditEndpoint (AUEP) : The Call Agent sends the AuditEndpoint command to the gateway to audit the status of an endpoint. The Call Agent can, for example, find out signal status, bearer information, …
  • AuditConnection (AUCX) : The Call Agent sends this command to the  gateway to find out the status of  a connection. Connection status information that can be retrieved using this command includes Call ID, Connection Mode, and connection parameters
  • RestartInProgress (RSIP) : The gateway sends this command to the Call Agent to inform the Call Agent that it is taking an endpoint or group of endpoints out of service or is returning an endpoint or group of endpoints to service.

MGCP Transport Layer

MGCP is Master/Slave protocol and MGCP endpoints are controlled by the Control Agent ( Most of the case , it will be the CUCM)

MGCP uses the UDP/2427 for its communication between the CUCM and the GW. It is also a text-based master/slave protocol used by a media gateway controller (MGC) and Call Agent to control media gateways. However , TCP/2428 is used to exchange keepalives between endpoints and Call Agent, as well for MGCP PRI/BRI backhaul.

MGCP MGCs and MGs can be described as follows:

  • MGC/Call Agent: this element possesses call control intelligence and controls MGs (example : Call Manager)
  • MG: This device provides translation between data packet and audio signals reveived over VoIP networks and other networks such as the PSTN ( example: IOS gateway)

Power of Alias command

In Cisco IOS , you have the option to put in place your own command with the command alias .

Don’t be shy to use it as it can be fun for the long expression or command that you have problem to remember / to type .

Here are some examples :

!
alias configure ns no shut
alias exec scavb show call active voice brief
alias exec sdvs show dial-peer voice summary
!