Cisco Cisco IOS Software Release 12.2(2)XA

call agent (CA)—An intelligent entity in an IP telephony network that handles call control in an MGCP 
voice over IP network. A call agent is also known as a media gateway controller (MGC).

CAS—Channel Associated Signaling.

COT—Continuity test as defined by SS7.

digit map—A representation of the number and type of digits that a gateway can expect to collect in a 
buffer, based on the network dial plan. The purpose is to tell the gateway how many digits to expect so 
that the digits can be sent in a single transaction rather than one at a time. The call agent provides digit 
maps to the gateway whenever the gateway is instructed to listen for digits.

disconnect threshold—The number of times a gateway retries sending a call agent message to the final 
IP address in the call-agent DNS lookup table. If this value is exceeded without response from a call 
agent, the gateway performs one last DNS lookup if lookup is enabled. If a new IP address has been 
added to the DNS table, the gateway starts the retransmission process again. Otherwise, the gateway 
places the endpoint in a disconnected state.

DS0—64 kbps channel in a T1/E1 line.

DSP—Digital Signal Processor.

DTMF—Dual Tone Multi-Frequency.

endpoint—A source or sink of voice data, which may be physical (such as a trunk interface or a line 
interface in a media gateway) or logical (such as an announcement stored on a server). Endpoint 
identifiers have two components: the domain name of the entity on which the endpoint exists (such as 
an access server or router) and the local name that specifies the individual endpoint (such as a port 
number for a physical endpoint).

FGD—Bellcore Feature Group D.

FGD-OS—Bellcore FGD Operator Services signaling.

FQDN—Fully Qualified Domain Name. Complete domain name including the host portion; for 
example, serverA.companyA.com.

ISUP—ISDN User Part. Protocol used in SS7 signaling.

media gateway—Equipment that provides call handling between the PSTN or a PBX and a VoIP 
network or an NAS. The media gateway is controlled by a call agent via MGCP.

media gateway controller—Another term for call agent.

MF—Multi-Frequency. Type of tone signaling used on PSTN trunks.

MGCP—Media Gateway Control Protocol.

MGC—Media gateway controller. Another term for call agent.

NAS—Network access server. An MGCP media gateway that provides a modem interface for accessing 
an IP network.

NCS—Network-based Call Signaling. PacketCable protocol that is a profile of MGCP 1.0 for 
residential gateways. 

package—A collection of MGCP events and signals that pertains to a particular type of endpoint.

persistent events—Events that are defined as reportable whether or not the call agent has explicitly 
requested to be notified of their occurrence.

piggybacked messages—Messages from the call agent to the gateway that are sent in the same UDP 
packet but processed in the order they were sent, as separate, simultaneous messages.