Access Network

That portion of a public switched network that connects access nodes to individual subscribers. The Access Network today is predominantly passive twisted-pair copper wiring.

Access Nodes

Points on the edge of the Access Network that concentrate individual access lines to a smaller number of feeder lines. Access Nodes may also perform various forms of protocol conversion. Typical Access Nodes are Digital Loop Carrier systems concentrating individual voice lines to T1 lines, cellular antenna sites, PBXs, and Optical Network Units (ONUs).

ADSL

Asymmetric Digital Subscriber Line: Modems attached to twisted pair copper wiring that transmit from 1.5 Mbps to 9 Mbps downstream (to the subscriber) and from 16 kbps upstream, depending on line distance.

ATM

Asynchronous Transfer Mode: an ultra high speed cell-based data transmission protocol which may be run over ADSL.

CAP

Competitive Access Provider: A company which provides network links between the customer and the IntereXchange Carrier or even directly to the ISP. CAPs operate private networks independent of LECs.

CSA

Carrier Serving Area: area served by a LEC, RBOC or telco, often using Digital Loop Carrier (DLC) technology.

DMT

Discrete Multitone: A digital modulation scheme that uses DSPs to pump more than six megabytes per second of data over one copper twisted pair.

DSLAM

Digital Subscriber Line Access Multiplexer: specifically, a device which takes a number of ADSL subscriber lines and concentrates these to a single ATM line.

DSL

Digital Subscriber Line: Modems on either end of a single twisted pair wire that deliver ISDN Basic Rate Access.

E1

A kind of ISDN Primary Rate Interface (PRI). Outside North America and Japan a PRI usually has 30 B channels and 1 D channel and an E1 interface.

HDSL

High Data Rate Digital Subscribe Line: Modems on either end of one or more twisted pair wires that deliver T1 or E1 speeds. At present T1 requires two lines and E1 requires three.

IEEE

Institute of Electrical and Electronics Engineers.

ISDL

Uses ISDN transmission technology to deliver data at 128 kbps into an IDSL "modem bank" connected to a router.

ISDN

Integrated Services Digital Network: a high-speed digital phone system that supersedes POTS.

ISP

Internet Service Provider: an organization offering and providing Internet services to the public and having its own computer servers to provide the services offered.

LAN

Local Area Network.

LEC

Local Exchange Carrier: one of the new U.S. telephone access and service providers that have grown up with the recent U.S. deregulation of telecommunications.

MPEG

Motion Picture Experts Group: the group that has defined the standards for compressed video transmission.

NIC

An expansion board that is inserted into a computer and enables the computer to be connected to a network. NICs are designed for a particular type of network, protocol, and media, although some can serve multiple networks.

NSP

Network Service Provider: the term for an organization offering and providing value added network services on a telecommunications network.

PBX

Private Branch Exchange: a private telephone network used within an enterprise. Users of the PBX share a certain number of outside lines for making telephone calls external to the PBX. Most medium sized and larger companies use a PBX because it's much less expensive than connecting an external telephone line to every telephone in the organization. In addition, it's easier to call someone within a PBX because the number you need to dial is typically just 3 or 4 digits.

POP

Point of Presence, a location where dial-up access Internet Service is available. Providers (ISPs) generally provide many POPs so that users can make a local call to gain Internet access.

POTS

Plain Old Telephone Service: the only name recognized around the world for basic analog telephone service. POTS takes the lowest 4kHz of bandwidth on twisted pair wiring. Any service sharing a line with POTS must either use frequencies above POTS or convert POTS to digital and interleave with other data signals.

PRI

Primary Rate Interface: ISDN service used mainly by ISPs and businesses. Why? It provides 23 B channels with 64-kbps throughput capability and one 64-kbps D channel for call signaling and setup. It was designed for transmission through a standard North American T1 trunk and has throughput capability to 1.472 mbps. The notation 23B+D, is another way of saying the same thing.

RADSL

Rate Adaptive ADSL: a version of ADSL where the modems test the line at start up and adapt their operating speed to the fastest the line can handle.

RBOC

Regional Bell Operating Company: one of the seven U.S. Telephone companies that resulted from the break up of AT&T.

Telco

The generic name for telephone companies throughout the world which encompasses RBOCs, LECs and PTTs.

T1

A leased-line specification providing for 24 frames with an aggregate bandwidth of up to 1.54 Mbps.

VADSL

Very high speed ADSL: same as VDSL (or a subset of VDSL, if VDSL includes symmetric mode transmission).

VDSL

Very high data rate Digital Subscriber Line: Modem for twisted pair access operating at data rates from 12.9 to 52.8 Mbps with corresponding maximum reach ranging from 4500 feet to 1000 feet of 24 gauge twisted pair.

WAN

Wide Area Network: Private network facilities, usually offered by public telephone companies but increasingly available from alternative access providers (sometimes called Competitive Access Providers, or CAPs), that link business network nodes.

Information for this glossary was found in part on the ADSL website at http://www.adsl.com/adsl_glossary.html