What role does the call agent play when using an MGCP gateway?

A call agent is essential when you are using an MGCP gateway. It knows the dial plan, so it tells the gateway where to route calls. It controls the setup and teardown of connections to endpoints on the gateway, and thus the setup and teardown of calls.

List the control messages that MGCP uses.

NotificationRequestRQNT

NotifyNTFY

CreateConnectionCRCX

ModifyConnectionMDCX

DeleteConnectionDLCX

AuditEndpointAUEP

AuditConnectionAUCX

EndpointConfigurationEPCF

RestartInProgressRSIP

How does MGCP Backhaul function?

The gateway terminates ISDN Q.921 messages but places the Q.931 messages in a TCP packet and sends them to the CallManager for processing.

What three commands do you need to enable MGCP on a router and identify Cisco CallManager as its call agent?

mgcp

mgcp call-agent [ip-address|hostname] [port] 5ccm-manager mgcp

Why is there a need for DTMF relay in a VoIP network, regardless of the gateway protocol used?

When you are using codecs that compress voice, DTMF tones might become distorted or part of the signal might be lost. Then the receiver would not be able to respond correctly to the numbers that were sent.