VoIP Glossary

ADSL
Asymmetric Digital Subscriber Line) capable of high speed communication over existing copper wires (up to 500 times higher than regular modems), as well as high speed data transmission over standard phone lines while simultaneously maintaining voice traffic. Supports downstream speeds from T-1 to 9Mbps and 640 Kbps upstream. The limit of the distance to the exchange is 18,000 feet (approx. 3.4 miles)

ATA – (Analog Telephone Adapter)
A phone handset-to-Ethernet adapter that allows traditional (analog) telephone devices to be used with Voice over IP (VoIP) services and equipment. The adapters are roughly the same size as a home Internet router and contain one or more traditional phone jack ports. The analog phone plugs into the adapter, which then communicates with an Internet router via an Ethernet connection.

Broadband
A transmission facility with bandwidth capacity considerable greater than a voice line of 4kHz, that enables high-speed transmission of multimedia over long haul networks.

Codec - (Coder / Decoder)
Critical item for converting analog voice into digital signals for transmission and other processes Electronically converts audio and video into digital codes and vice versa via techniques such as PCM and Delta modulation.

DHCP – (Dynamic Host Configuration Protocol)
Software that automatically assigns IP addresses to client stations logging onto a TCP/IP network. It eliminates having to manually assign permanent IP addresses. DHCP software typically runs in servers and is also found in some network devices. Newer DHCP servers dynamically update the DNS servers after making assignments.

DSL – (Digital Subscriber Line)
A technology that dramatically increases the digital capacity of ordinary telephone lines. DSL speeds are tied to the distance between the customer and the Telco Central Office. DSL is designed for short haul connections that require high speed in both directions. It is in an always on condition.

E-1
A European communication link, counterpart to the US T-1, that operates at a speed of 2.048 Mbps.

Ethernet
A widely used Local Area Network (LAN) developed by Xerox, Intel and Digital Equipment Corp. Ethernet is a shared LAN concept where all the transmissions are sent to the stations on the same segment. It operates over twisted wire and coaxial cable at speeds of up to 10 Mbps.

FXO - (Foreign Exchange Office)
Telephone line from distant LEC Central Office made available locally. With respect to VoIP gateways, it refers to a port(s) that a Central Office telephone line or analog extension line from a PABX would terminate on. This would make that line available to distant parties on the VoIP network.

FXS - (Foreign Exchange Subscriber)
Extension from a distant PABX made available locally. With respect to VoIP gateways, it refers to a port(s) that acts as an analog extension on the VoIP network.

Gatekeeper
Also known as Network Administrator software, whose function is to identify, control, count and supervise the flow of traffic on the network. Also handles terminal and gateway registration, address resolution, bandwidth control, admission control, etc. from a central point.

Gateway
An entrance and exit to/from a communications network. Technically, a computer that processes data received through the line, such as protocol conversion, data security checks, or converting ones email system to another - enabling the two systems to communicate. It is heavily used on the Internet, where the gateway is between the Internet link and the local network.

H.323
ITU-T standard defining a set of call control, channel setup, and codec specifications for real time transmission of voice and video over various types of networks (e.g., packet, Internet, Intranet, LAN's, WAN's) that don't offer guaranteed service or high quality of service. This standard defines the negotiation and adaptation layer for video and audio over packets switched networks. H.323 is comprised of a number of standards such as H.225 which is the middleware that specifies a message set for call signaling registration and admissions, supporting call negotiations.

ISP – (Internet Service Provider)
Companies that provide access to the Internet and World Wide Web, through either dial-up or dedicated circuits as cable, DSL, T-1, etc. There are many thousands of ISP's in the world. ISP's establish interface with one another in order to ensure a free flow of data between global networks.

IP Telephony – (Internet Protocol Telephony)
The two-way transmission of audio over a packet-switched IP network (TCP/IP network). When used in a private intranet or WAN, it is generally known as "voice over IP," or "VoIP." When the transport is the public Internet or the Internet backbone from a major carrier, it is generally called "IP telephony" or "Internet telephony." However, the terms IP telephony, Internet telephony and VoIP are used interchangeably.

LEC – (Local Exchange Carrier)
An organization that provides local telephone service within the U.S., which includes the RBOCs, large companies such as GTE and more than a thousand smaller and rural telephone companies (approximately 1,300 in total). A LEC provides service from the customer premises to its local exchange (central office) within a local geographic area.

PBX – (Private Branch Exchange)
A private telephone network used within an enterprise that interconnects telephone extensions to each other, as well as to the outside telephone network.

QoS – (Quality of Service)
Although a generic term widely used throughout every industry today, in Telephony, it is a specific measure of the quality of telephone service offered to subscribers. Furthermore, it is an ATM service in which bandwidth can be allocated by demand, therefore guaranteeing quality of transmission.

Packets
A frame or block of data (usually in binary form), organized for the transmission over communications channels.

POTS - (Plain Old Telephone Service)
Reference to standard telephone service on a regular telephone and line from the LEC.

Port
The entrance or exit to/from a computer, network or system. It may have a serial or parallel or analog RJ11interface. Serial ports are used for networking, parallel ports are used for printing RJ11 ports are used for voice and fax.

PPPoE - (Point-to-Point Protocol over Ethernet)
A method for running the PPP protocol, commonly used for dial-up Internet connections, over Ethernet. Used by DSL and cable modem providers, PPPoE supports the protocol layers and authentication widely used in PPP and enables a point-to-point connection to be established in the normally multipoint architecture of Ethernet. A discovery process in PPPoE determines the Ethernet MAC address of the remote device in order to establish a session.

PPP - (Point-to-Point Protocol)
The communications protocol used to dial up the Internet over a serial link, such as a POTS or IDSN line. Developed by the Internet Engineering Task Force in 1994, it superseded the SLIP protocol. PPP establishes the session between the user's computer and the ISP using the Link Control Protocol (LCP), which also handles authentication(PAP, CHAP, etc.), compression and encryption.

PSTN – (Public Switched Telephone Network)
The PSTN refers to the world's collection of interconnected voice oriented public telephone networks, both commercial and government owned.

Scalable
Software or hardware that can be expanded or contracted with relative ease and without major cost.

SNMP – (Simple Network Management Protocol)
Widely used for network monitoring and control. SNMP agents that reside in the network devices pass report data to the main console that is responsible for overseeing the network. These agents also return information to the Management Information base. (MIB)

SIP – (Session Initiated Protocol)
A signaling protocol for Internet Telephony. SIP can establish sessions for features such as audio/videoconferencing, interactive gaming, and call forwarding to be deployed over IP networks, thus enabling service providers to integrate basic IP telephony services with Web, email and chat services.

T-1
A US standard (1.544 Mbps) digital transmission link using two pairs of twisted wires. Typically brought to the subscriber over leased lines.

VoIP – (Voice over Internet Protocol)
Voice communications sent over packet networks such as the Internet.

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