Authentication, authorization, and accounting. Security services for packet networks.
AAL2
ATM Adaptation Layer 2. Supports traffic needing precise timing, such as compressed voice and video.
AAL5
ATM Adaptation Layer 5
AUEP
Audit Endpoint command. An MGCP or SGCP command that is used by the call agent to determine the status of a given endpoint on a gateway.
B
BGW
Business gateway.
bind
In MGCP, configuring the source address for signaling and media packets to the IP address of a specific interface.
business gateway
An xGCP media gateway which is a business customer premises equipment that has connection(s) to the VoIP network as well as connection(s) to the user's telephony equipment (typically a PBX, a corporate LAN or WAN). Such gateways are used to eliminate or reduce the need for individual medium (voice, data, and so forth) connectivity.
C
CA
Call agent.
CAC
Call admission control. Controls whether a call can be established, according to availability of local or network resources.
call agent
An intelligent entity in an IP telephony network which handles call control in an MGCP model Voice over IP network.
An intelligent entity in an IP telephony network that handles call control in an xGCP model Voice-over-IP network. A Call Agent is also known as a media gateway controller (MGC).
CAS
Channel Associated Signaling. A signaling technique that uses the same facility path for both voice and signaling traffic.
CCS
Common Channel Signaling
CID
AAL2 Channel Identifier
CLASS
Custom Local Area Subscriber Services, usually referred to as "Custom Calling" features
CLI
command-line interface.
CRCX
Create Connection request. Used in an MGCP call sequence by gateways to exchange SDP.
CSM
Call switching module. Card that contains digit collection logic to process incoming calls for automatic number information (ANI) and dialed number identification service (DNIS) digits.
D
DDR
Dial-on-demand routing.
disconnected procedure
When an endpoint attempts to communicate with its call agent and fails, the gateway may initiate the disconnected procedure, in which a timer (the disconnected timer) is started and RSIP messages are sent to the call agent at prescribed intervals until contact is established. This procedure ensures that an RSIP message is the first message to reach the call agent after communications are reestablished. The call agent may request an AUEP after the RSIP is received.
DNS
Domain Name System. Used to translate H.323 IDs, URLs, or e-mail IDs into IP addresses. DNS is also used to assist in locating remote gatekeepers and to reverse-map raw IP addresses to host names of administrative domains.
DS-0
64-kbps channel in a T1/E1 line.
DTMF
Dual-tone multifrequency. Tones made by pushing buttons on a telephone.
Tones used to send phone number digits to and from a switch. DTMF tones identify the numbers 0 through 9 and the * and # symbols.
E
E&M
Ear and Mouth analog signaling.
F
fax passthrough
The GW sends fax data encoded using a codec such as G.711 ulaw or G.711 alaw, resulting in a more reliable transmission. Fax passthrough provides repression of compression, echo cancellation, and other functions; issues redundant packets to ensure complete transmission; and provides a buffer to protect against clock skew.
FGD
Feature Group-D. Identifies a standardized service available to carriers delivered on a channelized T1 line.
FGD-OS
Feature Group-D Operator Services protocol. OS is a telephony signaling protocol for calls that originate from the Bell Operating Company (BOC) and are sent towards the carrier switch.
fx:extension
An extension of the local connection option used by the CA to instruct the GW to be in CA-controlled mode or GW-controlled mode.
FXO
Foreign Exchange Operator—An interface from a telephone to a PSTN central office or a station interface on a PBX.
FXS
Foreign Exchange Station—An interface that connects to a telephone, key set, or PBX to supply ring, voltage, and dial tone.
G
GW
Gateway.
I
IETF
Internet Engineering Task Force. Task force that consists of over 80 working groups responsible for developing Internet standards. The IETF operates under the auspices of the Internet Society.
IPDC
Internet Protocol Device Control. A device control specification.
ISP
Internet service provider.
M
MDCX
Modify connection request. Used in an MGCP call sequence by gateways to exchange SDP information.
mediagateway
The emerging industry standard generic term for a gateway.Equipment that connects the PSTN or a PBX with the Voice-over-IP network. It is controlled by a call agent using MGCP.
MGC
Media gateway controller. The emerging industry standard generic term for the VSC.Another name for call agent.
MGCP
Media Gateway Control Protocol. A merging of the IPDC and SGCP protocols.
N
NAS
network access server. Communications processor that connects asynchronous devices to a LAN or WAN through network and terminal emulation software. Performs both synchronous and asynchronous routing of supported protocols.
NCS
Network-based Call Signaling. PacketCable protocol, profile of MGCP 1.0 for residential gateways.
NSE
Named Signaling Event. Format of RTP packets used for applications such as modem relay and fax relay. NSEs have different payload values than NTEs.
NTE
Named Telephony Event. Format of RTP packets used to transport DTMF digits as defined in RFC 2833, RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals.
P
package
A set of signals and events that define a type of voice endpoint or connection. Examples include line-package, trunk-package, dtmf-package, and atm-package
payload type
Payload types are defined in RFC 2833, RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals. A payload type is a number from 96 through 127 that identifies the type of payload carried in the packet (for example, a payload type of 121 denotes a Cisco DTMF relay payload; a payload type of 122 denotes a fax payload). The payload type should be identical on the GW and call agent.
PDU
protocol data units. Used by bridges to transfer connectivity information.
PRI
ISDN primary rate interface
PSTN
Public Switched Telephone Network
PVC
Permanent Virtual Circuit
R
residential gateway
An xGCP media gateway that is customer premises equipment and has one or more connections to the VoIP network as well as to user telephony equipment.
RGW
Residential gateway.
RSC
Router switch controller.
RSIP
Restart In Progress command. An MGCP or SGCP command that is used by the gateway to signal that an endpoint, or a group of endpoints, is being taken in or out of service.
RTCP
RTP Control Protocol. The protocol monitors an RTP connection and conveys information about the on-going session.
RTP
Real-Time Transport Protocol. The protocol provides end-to-end network transport functions for applications transmitting real-time data and services such as payload type identification, sequence numbering, timestamping, and delivery monitoring.
S
SDP
Session Description Protocol.Messages containing capabilities information that are exchanged between gateways.
SGCP
Simple Gateway Control Protocol. Controls Voice-over-IP gateways using an external call control element (called a call agent). SGCP is used to establish, maintain, and disconnect calls across an IP network.
SIP
Session Initiation Protocol.
SPVC
Soft Permanent Virtual Circuit
SVC
Switched Virtual Circuit
T
T1
T1—24 64-Kbps time slots on a 1.544-Mbps serial interface.
TGW
see Trunking Gateway. Trunking gateway, also called the trunk side gateway. An xGCP media gateway that provides PSTN/IP gateway functionality.
trunking gateway
An xGCP media gateway that provides connectivity between the PSTN and VoIP networks.
An external gateway control protocol (xGCP) media gateway that provides connectivity between the PSTN and VoIP networks.
TSE
Inband Telephony Signaling Events
V
VAD
Voice Activity Detection
VCC
Virtual Channel Connection (used where it may be a PVC, SPVC, or SVC)
VoIP
Voice over IP. The ability to carry normal telephone-style voice over an IP-based Internet with POTS-like functionality, reliability, and voice quality. VoIP is a blanket term that generally refers to the Cisco standards-based approach (for example, H.323) to IP voice traffic.
VToA
Voice Trunking on ATM.
X
XCSP
External Call Service Provider. Subsystem that interoperates with external call protocols to provide services such as modem call setup and teardown.
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