Media Gateway Control Protocol (MGCP)

Media Gateway Control Protocol (MGCP) provides the signaling and call control protocol which is used to communicate between the Media Gateway Controller (MGC) and Media Gateway (MG). Basic purpose of the protocol depends on the direction of communication taking place. MGC instructs MG using MGCP about the media, events, signals to be played on endpoint. Creation of the connection, auditing the status of the endpoints and connections involved in the communication of media between networks is primary tasks of the protocol in MGC-->MG communication. At the same time, MG uses MGCP to report events to the call agent.

MGCP supports VoIP systems in which it provides an alternative method to call controlling. Since VoIP has following advantages compared to the traditional systems, even though replacement is not performed, slow adoption is performed in most of the implementations.

• Lower cost of network implementation
• Integration of voice and data applications
• New service features
• Reduced bandwidth
• Interoperation with traditional ss7 networks
• Seamless interworking in between the networks

In most of the networks, Signaling conversation and Media conversation is done separately as shown in the diagram below since it has many advantages.

• Media conversion closes to the traffic source and sink
• The call-handling functions is centralized
• MGC can control multiple gateways.
• New features can be added more quickly

Media Control Gateway Protocol should assist Media gateway in performing following activities in order to provide a quality service.

• The creation, modification and deletion of media streams
• Including the capability to negotiate the media formats
• The specification of the transformations applied to media streams
• Request the MG to report the occurrence of specified events within the media streams, and the corresponding actions
• Request the MG to apply tones or announcements
• The establishment of media streams according to certain QoS requirements
• Reporting QoS and billing/accounting statistics from an MG to an MGC
• The management of associations between an MG and an MGC
• In the case of failure of a primary MGC
• A flexible and scalable architecture in which an MGC can control different MGs
• Facilitate the independent upgrade of MGs and MGCs

There are 9 commands in MGCP to handle connections in which each and every command is acknowledged.

1. EPCF - EndpointConfiguration (coding characteristics)
2. RQNT - NotificationRequest (requested events)
3. NTFY - Notify (GW: detected events)
4. CRCX - CreateConnection
5. MDCX - ModifyConnection
6. DLCX - DeleteConnection
7. AUEP - AuditEndpoint
8. AUCX - AuditConnection
9. RSIP - RestartInProgress (GW : taken in/out of service)