Media Gateway Control Protocol - Protocol Overview

Protocol Overview

MGCP packets are unlike those generated by many other protocols. Usually wrapped in UDP port 2427, the MGCP datagrams are formatted with whitespace, much like you would expect to find in TCP protocols.

An MGCP packet is either a command or a response. Every issued MGCP command has a transaction ID and receives a response. Commands begin with a four-letter verb. Responses begin with a three number response code.

There are nine (9) command verbs:

AUEP, AUCX, CRCX, DLCX, EPCF, MDCX, NTFY, RQNT, RSIP

Two verbs are used by a Call Agent to query (the state of) a Media Gateway:

AUEP - Audit Endpoint AUCX - Audit Connection

Three verbs are used by a Call Agent to manage an RTP connection on a Media Gateway (a Media Gateway can also send a DLCX when it needs to delete a connection for its self-management):

CRCX - Create Connection DLCX - Delete Connection MDCX - Modify Connection

One verb is used by a Call Agent to request notification of events on the Media Gateway, and to request a Media Gateway to apply signals:

RQNT - Request for Notification

One verb is used by a Call Agent to modify coding characteristics expected by the "line-side" on the Media Gateway:

EPCF - Endpoint Configuration

One verb is used by a Media Gateway to indicate to the Call Agent that it has detected an event for which the Call Agent had previously requested notification of (via the RQNT command verb):

NTFY - Notify

One verb is used by a Media Gateway to indicate to the Call Agent that it is in the process of restarting:

RSIP - Restart In Progress