MGCP, Multimedia Gateway Control Protocol

Protocol suite:	TCP/IP.
Protocol type:	Application layer protocol.
Ports:	2427 (UDP) gateway. 2727 (UDP) call agent.
URI:
MIME subtype:
SNMP MIBs:
Working groups:
Links:	IANA: MGCP LocalConnectionOptions. IANA: MGCP Packages.

MAC header

IP header

UDP header

MGCP message

Data :::

Commands:

Code	Verb
AUCX	AuditConnection.
AUEP	AuditEndpoint.
CRCX	CreateConnection.
DLCX	DeleteConnection.
EPCF	EndpointConfiguration.
MDCX	ModifyConnection.
RQNT	NotificationRequest.
NTFY	Notify.
RSIP	RestartInProgress.

Return codes:

(0xx) Response acknowledgements:

Code	Description
0	The transaction is currently being executed. An actual completion message will follow on later.

(1xx) Provisional response:

Code	Description
100	The transaction is currently being executed. An actual completion message will follow on later.
101	The transaction has been queued for execution. An actual completion message will follow later.

(2xx) Successful completion:

Code	Description
200	The requested transaction was executed normally.
250	The connection was deleted.

(4xx) Transient error:

Code	Description
400	The transaction could not be executed, due to a transient error.
401	The phone is already off hook.
402	The phone is already on hook.
403	The transaction could not be executed, because the endpoint does not have sufficient resources at this time.
404	Insufficient bandwidth at this time.
405	The transaction could not be executed, because the endpoint is "restarting".
406	Transaction time-out. The transaction did not complete in a reasonable period of time and has been aborted.
407	Transaction aborted. The transaction was aborted by some external action, e.g., a ModifyConnection command aborted by a DeleteConnection command.
409	The transaction could not be executed because of internal overload.
410	No endpoint available. A valid "any of" wildcard was used, however there was no endpoint available to satisfy the request.

(5xx) Permanent error:

Code	Description
500	The transaction could not be executed, because the endpoint is unknown.
501	The transaction could not be executed, because the endpoint is not ready.
502	The transaction could not be executed, because the endpoint does not have sufficient resources.
503	"All of" wildcard too complicated.
504	Unknown or unsupported command.
505	Unsupported RemoteConnectionDescriptor. This SHOULD be used when one or more mandatory parameters or values in the RemoteConnectionDescriptor is not supported.
506	Unable to satisfy both LocalConnectionOptions and RemoteConnectionDescriptor. This SHOULD be used when the LocalConnectionOptions and RemoteConnectionDescriptor contain one or more mandatory parameters or values that conflict with each other and/or cannot be supported at the same time (except for codec negotiation failure, see error code 534).
507	Unsupported functionality. Some unspecified functionality required to carry out the command is not supported. Note that several other error codes have been defined for specific areas of unsupported functionality (e.g. 508, 511, etc.), and this error code SHOULD only be used if there is no other more specific error code for the unsupported functionality.
508	Unknown or unsupported quarantine handling.
509	Error in RemoteConnectionDescriptor. This SHOULD be used when there is a syntax or semantic error in the RemoteConnectionDescriptor.
510	The transaction could not be executed, because some unspecified protocol error was detected. Automatic recovery from such an error will be very difficult, and hence this code SHOULD only be used as a last resort.
511	The transaction could not be executed, because the command contained an unrecognized extension. This code SHOULD be used for unsupported critical parameter extensions ("X+").
512	The transaction could not be executed, because the gateway is not equipped to detect one of the requested events.
513	The transaction could not be executed, because the gateway is not equipped to generate one of the requested signals.
514	The transaction could not be executed, because the gateway cannot send the specified announcement.
515	The transaction refers to an incorrect connection-id (may have been already deleted).
516	The transaction refers to an unknown call-id.
517	Unsupported or invalid mode.
518	Unsupported or unknown package.
519	Endpoint does not have a digit map.
520	The transaction could not be executed, because the endpoint is "restarting".
521	Endpoint redirected to another Call Agent.
522	No such event or signal.
523	Unknown action or illegal combination of actions.
524	Internal inconsistency in LocalConnectionOptions.
525	Unknown extension in LocalConnectionOptions.
526	Insufficient bandwidth.
527	Missing RemoteConnectionDescriptor.
528	Incompatible protocol version.
529	Internal hardware failure.
530	CAS signaling protocol error.
531	Failure of a grouping of trunks (e.g. facility failure).
533	Response too large.
534	Codec negotiation failure.
535	Packetization period not supported.
536	Unknown or unsupported RestartMethod.
537	Unknown or unsupported digit map extension.
538	Event/signal parameter error (e.g., missing, erroneous, unsupported, unknown, etc.).
539	Invalid or unsupported command parameter. This code SHOULD only be used when the parameter is neither a package or vendor extension parameter.
540	Per endpoint connection limit exceeded.
541	Invalid or unsupported LocalConnectionOptions. This code SHOULD only be used when the LocalConnectionOptions is neither a package nor a vendor extension LocalConnectionOptions.

(8xx) Package specific response codes:

Code	Description
800	Invalid NextEndpointName.
801	Invalid StartEndpointName.
802	Invalid or unsupported BulkRequestInfo Parameter.
803	Invalid or unsupported StateType.
804	Bulk Audit Type not supported.
805	Incorrectly specified endpoint range.
806	Requested StartEndpoint unknown or unavailable.

Reason codes:
(RFC 2705) Reason codes are used by the gateway when deleting a connection to inform the Call Agent about the reason for deleting the connection. They may also be used in a RestartInProgress command, to inform the gateway of the Restart's reason.

Code	Description
0	Endpoint state is nominal. (This code is used only in response to audit requests.).
900	Endpoint malfunctioning.
901	Endpoint taken out of service.
902	Loss of lower layer connectivity (e.g., downstream sync).