Glossary

glossary

ACO

Alarm cut-off. A switch in hardware and software that cuts off audible alarms. See also alarm.

ADSL

Asymmetric digital subscriber line. One of several DSL technologies. ADSL is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream. Downstream rates range from 1.5 to 9 Mbps; upstream bandwidth ranges from 16 kbps to 1 Mbps. ADSL transmissions work at distances up to 18,000 feet (5486 meters) over a single copper wire twisted pair. See also DSL.

ADSL Forum

An organization of competing companies that sponsors an Internet Web site (http://www.adsl.com) containing information about the applications, technology, systems, markets, trials, and tariffs related to ADSL technology.

AIS

Alarm Indication Signal. A SONET port status indicator.

alarm

A status condition that shows that a module or port is experiencing an abnormal operating condition. See also critical alarm, major alarm, and minor alarm.

Asynchronous Transfer Mode

See ATM.

ATM

Asynchronous Transfer Mode. International standard for a broad-bandwidth, low-delay cell relay switching and multiplexing technique. ATM bandwidth is dynamically allocated. Multiple service types (such as voice, video, and data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, which reduces transit delays. ATM is designed to take advantage of high-speed transmission media such as DS3 and SONET. Also known as fast packet technology.

AWG

American Wire Gauge. The measurement of thickness of a wire. The lower the number, the thicker the wire (and the greater its capacity, both in terms of current it can carry and distance it can cover). Most telephone wiring is in the range 19 to 26 AWG, inclusive.

backplane

A printed circuit board at the rear of a chassis that can distribute data, clocking, power, or other services to the other modules in the system.

bandwidth

The range of frequencies a transmission line or channel can carry: the greater the bandwidth, the greater the information-carrying capacity of a channel. For a digital channel this is expressed in bits. For an analog channel, bandwidth depends on the type and method of modulation used to encode the data.

BITS

Building-integrated timing source. A receive-only T1 interface that extracts only the clock signal from the T1 line (data is discarded). This highly stable time reference supports constant bit rate (CBR) applications.

blower

Internal cooling fan used in larger chassis.

bps

Bits per second. A standard measurement of digital transmission speeds.

CAP

Carrierless amplitude modulation/phase modulation. An encoding method used by modems in some DSL equipment. For example, some CPE devices and the Flexi line card used in the Cisco 6160 use CAP. Contrast with DMT. CAP also stands for competitive access provider.

category cabling

EIA/TIA-defined standards for the twisted pair cabling used for data and telephony. The standards define cabling categories 1 through 5. Categories 1 and 2 are obsolete.

Category 1: Analog voice use only (not suitable for data). No frequency rating. UTP.

Category 2: Used for digital and analog voice, low-speed data (up to 4 Mbps). Rated to 1 MHz. UTP.

Category 3: Used for voice and for data such as 10BaseT Ethernet; can carry up to 10 Mbps. Rated to 16 MHz. UTP or STP.

Category 4: Used for voice and for data such as Token Ring and 10BaseT Ethernet; can carry data up to 16 Mbps. Rated to 20 MHz. UTP or STP.

Category 5: Used for voice (T3) and for data such as T3 and fast Ethernet; can carry data up to 100 Mbps. Rated to 100 MHz. UTP or STP.

Standards are under development for categories 6 (coaxial cable) and 7 (fiber-optic cable).

cell

In ATM, the basic data unit for switching and multiplexing. Each cell contains an identifier that specifies the data stream to which it belongs. Each cell consists of a 5-byte header and 48 bytes of payload. See also cell relay.

cell relay

Network technology based on the use of small, fixed-size packets, or cells. Because cells are fixed-length, they can be processed and switched in hardware at high speeds. Cell relay is the basis for many high-speed network protocols including ATM, IEEE 802.6, and SMDS. See also cell.

central office

See CO.

Cisco IOS software

Cisco Internetwork Operating System software. System software that provides common functionality, scalability, and security for all products under the CiscoFusion architecture. Cisco IOS software allows centralized, integrated, and automated installation and management of internetworks and ensures support for a wide variety of protocols, media, services, and platforms.

Central office. Local telephone company office to which all subscriber loops in a given area connect and in which circuit switching of subscriber lines occurs.

concentrator

In telephony, a device that multiplexes many lower-speed circuits onto one or more high-speed circuits, improving the efficiency of the network. For example, ISPs use concentrators to combine their dial-up modem connections onto faster lines (such as T1s) that connect to the Internet.

CPE

Customer premises equipment. Terminating equipment at the subscriber's side of the local telephone loop. CPE is often supplied by the telephone company and is always connected to the telephone company's network. Examples of CPE include telephones, POTS splitters, terminals, modems, and routers. Wiring is often included under the heading of CPE.

critical alarm

One of a group of alarm conditions that is considered the most severe of all reportable problems. Critical alarms affect most or all subscribers that connect to the reporting node. See also major alarm and minor alarm.

customer premises equipment

See CPE.

digital subscriber line

See DSL.

digital subscriber line access multiplexer

See DSLAM.

DMT

Discrete multitone modulation. An encoding method used by modems in some DSL equipment. For example, some CPE devices and the Flexi line card used in the Cisco 6160 use DMT. Contrast with CAP.

downstream

Pertaining to the movement of data traffic from a service provider to a subscriber. Contrast with upstream.

downstream rate

The line rate for return messages or data transfers from the network machine to the user's customer's premise machine. Contrast with upstream rate.

DS3

Digital signal level 3. Framing specification used for transmitting digital signals at 44.736 Mbps on a T3 facility. See also E3 and T3.

DSL

Digital subscriber line. A public network technology that delivers high bandwidth over conventional copper wiring (such as telephone lines) over limited distances. There are several types of DSL, including ADSL, HDSL, IDSL, SDSL, and VDSL. All are provisioned by means of modem pairs, with one modem located at a central office and the other at the customer site. Because most DSL technologies do not use the whole bandwidth of the twisted pair, there is room left for a voice channel.

DSLAM

Digital subscriber line access multiplexer. A device that connects many digital subscriber lines to a network by multiplexing the DSL traffic onto one or more network trunk lines.

Wide-area digital transmission scheme used predominantly in Europe. E3 carries data at a rate of 34.368 Mbps. See also DS3 and T3.

EIA

Electronic Industries Association. A group that specifies electrical transmission standards. The EIA and TIA have developed numerous well-known communications standards, including EIA/TIA-232 formerly (RS-232) and EIA/TIA-449 (formerly RS-449).

EIA/TIA-232

Common physical layer interface standard, developed by EIA and TIA, that supports unbalanced circuits at signal speeds up to 64 kbps. Closely resembles the V.24 specification. Formerly called RS-232.

EMI

Electromagnetic interference. Electromagnetic signals that escape from one device or circuit to be picked up by another. EMI can cause reduced data integrity and increased error rates on transmission channels.

ESD

Electrostatic discharge. Discharge of stored static electricity that can damage electronic equipment and impair electrical circuitry, resulting in complete or intermittent failures.

Ethernet

Baseband LAN specification originated by Xerox and developed jointly by Xerox, Intel, and Digital Equipment Corp. Nodes on Ethernet networks use CSMA/CD to contend for access to the transmission medium. 10-Mbps Ethernet includes specifications for many different cable types, including 10Base2, 10Base5, 10BaseF, 10BaseT, and 10Broad36. A newer standard, Fast Ethernet, calls for data to be carried at 100 Mbps. Ethernet is similar to IEEE 802.3.

ETSI

European Telecommunication Standards Institute. An organization that proposes telecommunication standards for Europe. It was established in 1988 by a decision of the European Conference of Postal and Telecommunications Administrations (CEPT). It has taken over the work of the CEPT in developing the Net-Normes Europeene de Telecommunication.

faceplate

The front panel of a plug-in module such as a line card or a power supply.

FCC

Federal Communications Commission. A U.S. government agency that regulates interstate and foreign communications. The FCC sets rates for communication services, determines standards for equipment, and controls broadcast licensing.

FEC

Forward error correction. A class of methods for controlling errors in a one-way communication system. Along with the payload data, nodes using FEC send information that can be used to check and correct the data.

FERF

Far End Receive Failure. A SONET port status indicator.

field-replaceable unit

See FRU.

Flexi card

A 4-port ATU-C line card that can be configured to provide either CAP or DMT line encoding.

forward error correction

See FEC.

FRU

Field-replaceable unit. A component that can be removed from a network device and replaced in the field. Line cards, power modules, and fan modules are typically FRUs.

host

A computer system on a network. Similar to node, except that "host" usually implies a computer system, whereas "node" generally applies to any networked system, including access servers and routers. See also node.

Internet Protocol

See IP.

I/O card

The I/O card used in the Cisco 6160 provides three DS3 ports (paired BNC connectors), plus a wire wrap connector for alarm relay and BITS interfaces. The I/O card is mounted on the back of the chassis.

IOS

See Cisco IOS software.

Internet Protocol. The network layer protocol for the TCP/IP protocol stack, offering a connectionless internetwork service. IP provides features for addressing, type-of-service specification, fragmentation and reassembly, and security. IP is defined in RFC 791.

IP address

The 32-bit address assigned to hosts using TCP/IP. An IP address belongs to one of five classes (A, B, C, D, or E) and is written as four octets separated by periods. This is called dotted decimal format. For example: 172.16.211.0. Each address consists of a network number, an optional subnetwork number, and a host number. The network and subnetwork numbers together are used for routing, and the host number is used to address an individual host within the network or subnetwork. A subnet mask is used to extract network and subnetwork information from the IP address. Also called Internet address. See also IP and subnet mask.

ISP

Internet service provider. A company that allows home and corporate users to connect to the Internet.

ITU-T

International Telecommunications Union, Standardization Sector. ITU-T is the telecommunication standardization sector of ITU and is responsible for making technical recommendations about telephone and data (including fax) communications systems for service providers and suppliers. The ITU-T carries out the functions of the former CCITT. A sister organization, ITU-R, carries out similar functions for radio.

Kilobyte (approximately 1000 bytes).

Kilobit (approximately 1000 bits).

kBps

Kilobytes per second, a measurement of transmission speed.

kbps

Kilobits per second, a measurement of transmission speed.

LAIS

Line Alarm Indication Signal. A SONET port status indicator that activates when an LAIS defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds.

LAN

Local-area network. A limited distance (typically under a few kilometers or a couple of miles) high-speed network (typically 4 to 100 Mbps) that supports many computers (typically two to thousands). Compare with WAN.

LED

Light emitting diode. A light indicating status or activity on electronic equipment.

line

Originally, the wires connecting the telephone subscriber to the local central office (CO). (See loop; contrast with trunk.) However, the term line is often used now to indicate a wire or fiber connection between two points, even if that connection is technically a trunk.

Line Alarm Indication Signal

See LAIS.

line rate

The speed by which data is transferred over a particular line type, expressed in bits per second (bps).

Line Remote Failure Indication

See LRFI.

loading coils

Regularly spaced inductance coils added to a voice circuit in order to improve its transmission characteristics. Loading coils are not used on data circuits because they tend to introduce errors in frequencies that are outside the normal voice range.

LOCD

Loss of Cell Delineation. A SONET port status indicator that activates when an LOCD defect occurs and does not clear for an interval of time equal to the alarm integration period, which is typically 2.5 seconds.

LOF

Loss of Frame. A SONET port status indicator that activates when an LOF defect occurs and does not clear for an interval of time equal to the alarm integration period, which is typically 2.5 seconds.

loop

The wire-line connection between a service-providing network and the customer; also called distribution loop, local loop, subscriber loop, or subscriber line.

loopback

A diagnostic test that returns a transmitted signal to the sending device after it has passed through a network or across a particular link. The returned signal can then be compared to the transmitted one. The discrepancy between the two helps you to trace faults. When you are trying to locate a faulty piece of equipment, you can use repeated loopbacks to eliminate healthy machines until the problem is found.

LOP

Loss of Pointer. A SONET port status indicator that activates when an LOP defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds.

LOS

Loss of Signal. A SONET port status indicator that activates when an LOS defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds.

Loss of Cell Delineation

See LOCD.

Loss of Frame

See LOF.

Loss of Pointer

See LOP.

Loss of Signal

See LOS.

Loss of Synchronization

See LOST.

LOST

A SONET port status indicator that activates when a LOST defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds. A LOST defect occurs when a valid clock signal cannot be extracted from the configured timing source.

LRFI

Line Remote Failure Indication. A SONET port status indicator that activates when an LRFI defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds.

MAC

Media Access Control Layer. A sublayer of the Data Link Layer (Level 2) of the ISO OSI model responsible for media control.

major alarm

One of a group of alarm conditions that is considered the second most severe of all reportable alarms. Major alarms affect several subscribers who connect to the reporting node. See also critical alarm and minor alarm.

Management Information Base

See MIB.

Megabyte (approximately 1,000,000 bytes).

Megabit (approximately 1,000,000 bits).

Mbps

Megabits per second, a measurement of transmission speed.

MIB

A database of network management information that is used and maintained by a network management protocol such as CMIP (Common Management Information Protocol) or SNMP (Simple Network Management Protocol). The value of a MIB object can be changed or retrieved using CMIP or SNMP commands, usually through a GUI-based network management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches.

minor alarm

One of a group of alarm conditions that is considered the third most severe of all reportable alarms. Minor alarms affect a single subscriber or a small number of subscribers who connect to the reporting node. See also critical alarm and major alarm.

multiplexer

A device that can send several signals over a single line. The signals are separated by a similar device at the other end of the link. This can be done in a variety of ways: time division multiplexing, frequency division multiplexing, and statistical multiplexing. Multiplexers are becoming increasingly efficient in terms of data compression, error correction, transmission speed, and multi-drop capabilities.

NI-2

The second-generation network interface card that is used in the Cisco 6160 and other systems. The NI-2 card runs Cisco IOS software and provides the ATM switch fabric, trunk and subtending interfaces, processing, and nonvolatile storage resources for the system. The NI-2 is available with either OC-3c or DS3 interfaces.

node

Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be processors, controllers, or workstations. Nodes, which vary in routing and other functional capabilities, can be interconnected by links, and serve as control points in the network. "Node" is sometimes used generically to refer to any entity that can access a network, and is frequently used interchangeably with "device." See also host.

OC-3c

A physical protocol for SONET optical signal transmissions. OC-3c puts STS frames onto a fiber-optic line at 155.52 Mbps.

PAIS

Path Alarm Indication Signal. A SONET port status indicator that activates when a PAIS defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds. A PAIS defect occurs when an LOS, LOF, LAIS, or LOP is detected on the incoming signal of an upstream network element. The PAIS is signaled to downstream elements.

Path Alarm Indication Signal

See PAIS.

Path Remote Failure Indication

See PRFI.

PEM

Power entry module. A hardware module that distributes power to the chassis.

PLCP

Physical Layer Convergence Procedure. A specification that maps ATM cells into physical media such as T3 or E3, and defines certain management information.

POTS

Plain old telephone service. See also PSTN.

POTS splitter

A frequency-based filter that separates (or combines) voice signals and data signals traveling on the same telephone line. Also called a voice filter.

power entry module

See PEM.

PRFI

Path Remote Failure Indication. A SONET port status indicator that activates when a Path Remote Defect Indication (PRDI) occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds.

PSTN

Public switched telephone network. General term referring to the various telephone networks and services in place worldwide. Sometimes called plain old telephone service (POTS).

public switched telephone network

See PSTN.

RDI

Remote Defect Indication. A SONET port status indicator.

ring

See tip and ring.

RJ connector

Registered jack connector. One of a series of standard connectors originally used to connect telephone lines. RJ connectors are now used for telephone connections and for 10BaseT and other types of network connections. RJ-11, RJ-12, and RJ-45 are popular types of RJ connectors.

router

Network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information.

routing table

A data structure stored within a router that contains network path and status information. It is used to select the most appropriate route by which to forward information.

RS-232

See EIA/TIA-232.

SDSL line card

A module that provides 4 symmetric digital subscriber line (SDSL) subscriber ports for the DSLAM.

Signal Label Mismatch

See SLM.

signal-to-noise ratio

See SNR.

Simple Network Management Protocol

See SNMP.

SLM

Signal Label Mismatch. A SONET port status indicator that activates when an SLM defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds.

SNMP

Simple Network Management Protocol. A network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, and to manage configurations, statistics collection, performance, and security. SNMP2 is an improved version of SNMP.

SNR

Signal-to-noise ratio. The ratio of good data (signal) to bad (noise) on a line, expressed in decibels (dB).

SONET

Synchronous Optical Network. Specification for a high-speed (up to 2.5 Gbps) synchronous network developed by Bellcore and designed to run on optical fiber. STS-1 is the basic building block of SONET. See also STS-1.

splitter

See POTS splitter.

STM-1

Synchronous Transport Module level 1. One of a number of SDH formats that specifies the frame structure for the 155.52-Mbps lines used to carry ATM cells. (SDH is a European format similar to SONET.)

STS-1

Synchronous Transport Signal level 1. Basic building block signal of SONET, operating at 51.84 Mbps. Faster SONET rates are defined at STS-n, where n is a multiple of 51.84 Mbps. See also SONET.

STS-3c

Synchronous Transport Signal level 3, concatenated. SONET format that specifies the frame structure for the 155.52-Mbps lines used to carry ATM cells. See also SONET.

subnet mask

A 32-bit address mask used in IP to indicate the bits of an IP address that are being used for the subnet address. Sometimes referred to simply as a mask. See also IP address.

subscriber

The entity who requests and pays for various network services. Also called end user or customer.

subscriber loop

The wire-line connection between a service-providing network and the customer; also called distribution loop, local loop, or subscriber line.

subtending

The practice of linking two or more similar devices (such as DSLAMs) so that they can be served by a single network trunk port. Subtended Cisco 6160 units are managed as separate devices.

Digital WAN carrier facility. T1 transmits DS1-formatted data or voice at 1.544 Mbps through the telephone switching network, using AMI or B8ZS coding over two pairs of standard copper wires.

Digital WAN carrier facility. T3 transmits DS3-formatted data or voice at 44.736 Mbps through the telephone switching network, using fiberoptic cable.

Telnet

The virtual terminal protocol in the Internet suite of protocols. Allows users of one host to log in to a remote host and act as normal terminal users of that host.

tip and ring

The two sides of a telephone circuit. The names come from old telephone switch board plugs: the tip wire was connected to the tip of the plug, and the ring wire was connected to the ring at the base of the plug.

trunk

A physical and logical connection between two telephone or data switches across which network traffic travels. A network backbone is composed of one or more trunks.

twisted pair

A relatively low-speed transmission medium consisting of two insulated copper wires twisted together, with the twists or lays varied in length to reduce potential signal interference between the pairs. The wires can be shielded or unshielded. Twisted pair wiring is common in telephone applications and is increasingly common in data networks. See also category cabling and UTP.

Underwriters Laboratories. A private organization in the U.S. that tests electrical components and devices against rigorous safety standards. A UL listing mark on a product means that representative samples of the product have been tested against nationally recognized safety standards with regard to fire, electric shock, and other safety hazards.

unshielded twisted pair

See UTP.

upstream

Pertaining to the movement of data traffic from a subscriber to a service provider. Contrast with downstream.

upstream rate

The line rate for message or data transfer from the source machine to a destination machine on the network. Contrast with downstream rate.

UTP

Unshielded twisted pair. The cable that is used for standard voice service between a subscriber and a telephone service provider, and in a variety of other applications. UTP consists of one or more pairs of insulated copper wire. It does not require the fixed spacing between connections that is necessary with coaxial-type connections. There are five types of UTP cabling, Category 1 through Category 5. See also category cabling and twisted pair.

In ATM, a virtual channel. A defined route between two end points in an ATM network. A VC can traverse several virtual paths.

WAN

Wide area network. A data communications network that serves users across a broad geographic area and often uses transmission devices provided by a common carrier (such as a telephone company). Frame Relay, SMDS, and ATM are examples of WANs. Compare with LAN.

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glossary

glossary