glossary

A

AAL5

ATM adaptation layer 5. This layer maps higher layer user data into ATM cells, making the data suitable for transport through the ATM network.

access identifier

See AID.

address mask

A bit mask used to select bits from an Internet address for subnet addressing. The mask is 32 bits long and selects the network portion of the Internet address and one or more bits of the local portion. Sometimes called subnet mask.

ADSL

asymmetric digital subscriber line. A digital subscriber line (DSL) technology in which the transmission of data from server to client is much faster than the transmission from the client to the server.

ADSL Transmission Unit—central office

See ATU-C.

ADSL Transmission Unit—remote

See ATU-R.

AID

access identifier.

AIS

alarm indication signal.

American National Standards Institute

See ANSI.

American Wire Gauge

See AWG.

ANSI

American National Standards Institute. An organization that develops standards for many things, only some having to do with computers. ANSI is a member of the International Standards Organization (ISO). See ISO.

asymmetric digital subscriber line

See ADSL.

asynchronous communications

A method of transmitting data in which each transmitted character is sent separately. The character has integral start and stop bits so that the character can be sent at an arbitrary time, and separate from any other character.

Asynchronous Transfer Mode

See ATM.

ATM

Asynchronous Transfer Mode. A cell-based data transfer technique in which channel demand determines packet allocation. ATM offers fast packet technology, real time, demand led switching for efficient use of network resources.

ATM adaptation layer 5

See AAL5.

ATU-C

ADSL Transmission Unit—central office.

ATU-R

ADSL Transmission Unit—remote.

authentication

A security feature that allows access to information to be granted on an individual basis.

autonegotiation

Procedure for adjusting line speeds and other communication parameters automatically between two computers during data transfer.

AWG

American Wire Gauge. The measurement of thickness of a wire.

B

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 defined in bits. For an analog channel, it is dependent on the type and method of modulation used to encode the data.

bandwidth on demand

The ability of a user to dynamically set upstream and downstream line speeds to a particular rate of speed.

BOOTP

A TCP/IP network protocol that lets network nodes request configuration information from a BOOTP "server" node.

bps

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

bits per second

See bps.

bridge

A device that connects two or more physical networks and forwards packets between them. Bridges can usually be made to filter packets, that is, to forward only certain traffic. Related devices are: repeaters which simply forward electrical signals from one cable to the other, and full-fledged routers which make routing decisions based on several criteria. See repeater and router.

broadband

Characteristic of any network that multiplexes independent network carriers onto a single cable. This is usually done using frequency division multiplexing (FDM). Broadband technology allows several networks to coexist on one single cable; traffic from one network does not interfere with traffic from another since the "conversations" happen on different frequencies in the "ether" rather like the commercial radio system.

broadband remote access server

Device that terminates remote users at the corporate network or Internet users at the ISP network that provides firewall, authentication, and routing services for remote users.

broadcast

A packet delivery system where a copy of a given packet is given to all hosts attached to the network. Example: Ethernet.

C

CAP

Carrierless Amplitude and Phase Modulation. A modulation technology for ADSL.

Carrierless Amplitude and Phase Modulation

See CAP.

CBOS

Cisco Broadband Operating System. Operating System that users access to configure and operate the Cisco products.

CCO

Cisco Connection Online.

cell relay

Generic term for a protocol based on small fixed packet sizes capable of supporting voice, video, and data at very high speeds.

central office

See CO.

Channel Service Unit/Data Service Unit (CSU/DSU)

A digital interface unit that connects end user equipment to the local digital telephone loop.

chassis

The card cage (housing) where modules are placed.

Cisco Broadband Operating System

See CBOS.

Cisco Connection Online

See CCO.

CLEI

Common Language Equipment Identifier.

client-server model

A common way to describe network services and the user processes (programs) of those services. Examples include the name-server/name-resolver paradigm of the DNS and file-serve/file-client relationships such as NFS and diskless hosts.

CLI

command line interface.

CLLI

Common Language Location Identifier.

CO

central office. Local telephone office through which all local loops in a given area connect and switch subscriber lines.

Common Language Equipment Identifier

See CLEI.

Common Language Location Identifier

See CLLI.

connectionless network

The transport of a single datagram or packet of information from one network node to a destination node or multiple nodes without establishing a network connection.

connection-oriented network

The transport of packets of information from one network node to a destination node following an established network connection.

CPE

customer premises equipment. Terminating equipment, such as terminals, telephones, and modems, supplied by the telephone company. The equipment is installed at customer sites and connected to the telephone company network.

CTC

common transmit clock.

customer premises equipment

See CPE.

D

daemon

A program that is not invoked explicitly but lies dormant waiting for some condition(s) to occur.

DDTS

Cisco Distributed Defect Tracking System.

dial-up network

Enables computer users to dial up a service provider's computer using a modem.

digital signal level 3

See DS3.

Discrete Multitone

See DMT.

Distributed Defect Tracking System

See DDTS.

distributed processing

An approach that allows one application program to execute on multiple computers linked together by a network. The networked computers share the work between them.

DMT

Discrete Multitone.

dotted decimal notation

The syntactic representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them. Used to represent IP addresses in the Internet as in: 221.34.64.32.

downstream rate

The line rate for return messages or data transfers from the network machine to the user's CPE.

DRAM

dynamic random-access memory. A type of semiconductor memory in which the information is stored in capacitors on a metal oxide semiconductor integrated circuit.

DS1

digital signal level 1. A 1.544 Mbps digital signal that is carried on a T1 line.

DS3

digital signal level 3. Framing specification used for transmitting digital signals at 44.736 Mbps on a T3 facility.

DSLAM

digital subscriber line access multiplexer. Concentrates and multiplexes digital subscriber line signals at the telephone service provider location to the broadband wide area network. Replaces ADSLAM.

DSL Forum

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

dynamic random-access memory

See DRAM.

E

E1

A digital carrier that is used to transmit a formatted signal at 2.048 Mbps.

EIA

Electronic Industries Association. A standards organization made up of electronics industry organizations. EIA is responsible for The RS-232C and RS-422 standards.

Electronic Industries Association

See EIA.

encapsulation

The technique used by layered protocols in which a layer adds header information to the protocol data unit (PDU) from the layer above. As an example, in Internet terminology, a packet would contain a header from the physical layer, followed by a header from the network layer (IP), followed by a header from the transport layer (TCP), followed by the application protocol data.

entity

A physical or logical system component which is represented in the 6100 SNMP Agent.

EPROM

Erasable programmable read-only memory.

erasable programmable read-only memory

See EPROM.

error detection

A process used during file transfer to discover discrepancies between transmitted and received data. Some file transfer programs only detect errors; others detect errors and attempt to fix them (called error correction).

ESF

Extended Superframe. A framing type that is used on T1 circuits that consists of 24 frames of 192 bits each, with the 193rd bit providing timing and other functions.

Ethernet

One of the most common local area network (LAN) wiring schemes, Ethernet has a transmission rate of 10 Mbps; a newer standard called Fast Ethernet carries 100 Mbps.

ETSI

A European standards body 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 the area of developing the Net-Normes Europeene de Telecommunication, Net standards.

F

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.

Federal Communications Commission

See FCC.

File Transfer Protocol

See FTP.

finger daemon

A software tool that allows a client to query a server for information on users.

firewall

A method for protecting Internet-connected enterprise networks from break-ins by unauthorized persons outside the network.

frame

A packet as it is transmitted over a serial line. The term derives from character oriented protocols where special start-of-frame and end-of-frame characters were added when transmitting packets.

FTP

File Transfer Protocol. The Internet protocol (and program) used to transfer files between hosts.

G

G.804

ITU-T framing standard that defines the mapping of ATM cells into the physical medium.

gateway

A system which does translation from some native format to another. Examples include X.400 to/from RFC 822 electronic mail gateways. See router.

H

handshake

Part of the procedure to set up a data communications link. The handshake can be part of the protocol itself or an introductory process. The computers wishing to talk to each other set out the conditions they can operate under. Sometimes, the handshake is just a warning that a communication is imminent.

HDLC

High-Level Data Link Control. A bit-oriented, synchronous, link layer, data-framing, flow control, and error detection and correction protocol. Available subsets include: 802.2 (logical link control for FDDI, Token Ring, and some Ethernet LANs, LAP (link access procedure balanced for X.25), LAPD (link access procedure for the ISDN D channel and frame relay), and LAPM (link access procedure for error-correcting modems specified as part of V.42).

High-Level Data Link Control

See HDLC.

hop count

A measure of distance between two points on the Internet. It is equivalent to the number of gateways that separate the source and destination.

HTML

Hypertext Markup Language. The page-coding language for the World Wide Web.

HTML browser

A browser used to traverse the Internet, such as Netscape or Microsoft Internet Explorer.

HTTP

Hypertext Transfer Protocol. The protocol used to carry world wide web (WWW) traffic between a WWW browser computer and the WWW server being accessed.

Hypertext Markup Language

See HTML.

Hypertext Transfer Protocol

See HTTP.

I

ICMP

Internet Control Message Protocol. The protocol used to handle errors and control messages at the IP layer.

ICP

IMA control protocol.

IDCR

IMA data cell rate.

IEEE

Institute of Electrical and Electronics Engineers. A U.S. publishing and standards organization responsible for many LAN standards.

IMA

inverse multiplexing over ATM. Standard protocol defined by the ATM Forum in 1997.

Industry-Standard Architecture

See ISA.

Institute of Electrical and Electronics Engineers

See IEEE.

International Organization for Standardization

See ISO.

International Telecommunication Union Telecommunication Standardization Sector

See ITU-T.

Internet

A collection of networks interconnected by a set of routers, which allows them to function as a single, large virtual network. When written in upper case, Internet refers specifically to the DARPA (Defense Advanced Research Projects Agency) Internet and the TCP/IP protocols it uses.

Internet address

An IP address assigned in blocks of numbers to user organizations accessing the Internet. The United States Department of Defense's Network Information Center establishes these addresses. Duplicate addresses can cause major problems on the network, but the NIC trusts organizations to use individual addresses responsibly. Each address is a 32-bit address in the form of x.x.x.x where x is an eight- bit number from 0 to 255. There are three classes: A, B, and C, depending on how many computers on the site are likely to be connected.

Internet Control Message Protocol

See ICMP.

Internet Protocol

See IP.

Internet service provider

See ISP.

Internetwork Packet Exchange

See IPX.

Internetwork Packet Exchange Control Protocol

See IPXCP.

inverse multiplexing

Allows individually dialed channels across the network to be combined into a single, higher-speed data streams. Using this service, a user can dial multiple calls and combine them together into a single high-speed data stream.

IP

Internet Protocol. The network layer protocol for the Internet Protocol suite.

IP address

The 32-bit address assigned to hosts that want to participate in a TCP/IP Internet.

IP datagram

The fundamental unit of information passed across the Internet. It contains source and destination addresses along with data and a number of fields that define such things as the length of the datagram, the header checksum, and flags to say whether the datagram can be or has been fragmented.

IPX

Internetwork Packet Exchange. The network layer (OSI Layer 3) datagram-based protocol usually used by Novell's NetWare network operating system. Supports any window size and packet sizes up to 64 KB.

IPXCP

Internetwork Packet Exchange Control Protocol. A protocol defined in RFC 1552.

ISA

Industry-Standard Architecture. The bus used in standard IBM-compatible PCs to provide power to add-in boards and to the motherboard (into which the boards plug). Typical maximum transfer speed of 1 to 2.5 Mbps (variables include other devices, memory, and buffering) but designed for up to 16 Mbps.

ISO

International Organization for Standardization. A voluntary, nontreaty organization founded in 1946, responsible for creating international standards in many areas, including computers and communications.

ISP

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

ITC

independent transmit clock.

ITU-T

International Telecommunication Union Telecommunication 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.

L

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).

LCD

loss of cell delineation.

LCP

link control protocol.

LED

light emitting diode. The lights indicating status or activity on electronic equipment.

LIF

loss of IMA frame.

light emitting diode

See LED.

line concentration

Functionality performed by a type of multiplexer that combines multiple channels onto a single transmission medium in such a way that all the individual channels can be simultaneously active. For example, ISPs use concentrators to combine their dial-up modem connections onto faster T1 lines that connect to the Internet.

line rate

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

local-area network

See LAN.

LODS

loss of delay synchronization.

LOF

loss of frame.

logical pool

A logical grouping of ATU-C ports and LIM ports that comprise a particular DOH oversubscription ratio.

logical port

A logical entry to a server machine. These ports are mostly invisible to the user, though you may occasionally see a URL with a port number included in it. These ports do not refer to physical locations; they are set up by server administrators for network trafficking.

loopback

A diagnostic test that returns the transmitted signal back 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 discrepancies between the two help to trace the fault. When trying to locate a faulty piece of equipment, loopbacks will be repeated, eliminating satisfactory machines until the problem is found.

LOS

loss of signal.

M

MAC

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

Management Information Base

See MIB.

MD5 protocol

Authentication and encryption protocol.

MDI

Multidocument Interface.

Media Access Control

See MAC.

MIB

Management Information Base. A collection of objects that can be accessed via a network management protocol, such as SNMP and CMIP (Common Management Information Protocol).

MMF

multimode fiber.

modem redundancy

When backup modems are immediately available should a modem facilitating communication fail.

module

A printed circuit board that occupies a slot in a chassis.

Multidocument Interface

See MDI.

multimode fiber

See MMF.

multicast

A special form of broadcast where copies of the packet are delivered to only a subset of all possible destinations. See also broadcast.

multiplexer

A device that can send several signals over a single line. They are then 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 also becoming increasingly efficient in terms of data compression, error correction, transmission speed, and multidrop capabilities.

N

NAT

Network Address Translation.

Network Address Translation

See NAT.

network interface

Boundary between a carrier network and a privately-owned installation.

network layer

The OSI layer that is responsible for routing, switching, and subnetwork access across the entire OSI environment.

Network Virtual Terminal

See NVT.

NI-2

A second generation network interface card.

node

A general term used to refer to a computer or related device; often used to refer to a networked computer or device.

Node System Save file

See NSS.

noise margin

The amount of noise tolerated by the ATU-C and ATU-R while training.

NSS

Node System Save file. The file that is saved during a Save Configuration or during a Software download. This file is required for Restore Configurations.

NVT

Network Virtual Terminal.

O

OC-3

optical carrier level 3. Physical protocol, defined for SONET optical signal transmissions.

octet

A networking term that identifies eight bits. In TCP/IP, it is used instead of byte, because some systems have bytes that are not eight bits.

OOF

out of frame.

Open System Interconnection

See OSI.

Optical Carrier Level 3

See OC-3.

OSI

Open System Interconnection. An international standardization program to facilitate communications among computers from different manufacturers. See ISO.

OSR

oversubscription ratio. The number of LIM ports divided by the number of ATU-C ports within a given logical pool.

oversubscription ratio

See OSR.

P

packet

The unit of data sent across a packet switching network.

PAP

Password Authentication Protocol.

Password Authentication Protocol

See PAP.

PCI

Peripheral Component Interconnect. An industry local bus standard. Supports up to 16 physical slots but is electrically limited to typically three or four plug-in PCI cards in a PC. Has a typical sustained burst transfer rate of 80 Mb—enough to handle 24-bit color at 30 frames per second (full-color, full-motion video).

PEM

power entry module.

Peripheral Component Interconnect

See PCI.

permanent virtual circuit

See PVC.

physical layer

Handles transmission of raw bits over a communication channel. The physical layer deals with mechanical, electrical, and procedural interfaces.

physical pool

A physical grouping of chassis slots within the Cisco 6100/6130 or Cisco 6110.

physical port

A physical connection to a computer through which data flows. An "Ethernet port," for example, is where Ethernet network cabling plugs into a computer.

plain old telephone service

See POTS.

Point-to-Point Protocol

See PPP.

port

The abstraction used by Internet transport protocols to distinguish among multiple simultaneous connections to a single destination host. A single termination point on one of the multiport modules (POTS, LIM, or ATU-C).

POTS

plain old telephone service.

PPP

Point-to-Point Protocol. The successor to SLIP, PPP provides router-to-router and host-to-network connections over both synchronous and asynchronous circuits. See SLIP.

protocol

A formal description of messages to be exchanged and rules to be followed for two or more systems to exchange information.

PVC

permanent virtual circuit. A fixed virtual circuit between two users: the public data network equivalent of a leased line. No call setup or clearing procedures are needed.

Q

QoS

quality of service. A characteristic of data transmission that measures how accurately and how quickly a message or data is transferred from a source computer to a destination computer over a network.

quality of service

See QoS.

R

RADIUS

Remote Authentication Dial-In User Service. A client/server security protocol created by Livingston Enterprises. Security information is stored in a central location, known as the RADIUS server.

RADIUS Accounting Client

Permits system administrators to track dial-in use.

RADIUS Security Client

Controls access to specific services on the network.

RADSL

rate adaptive digital subscriber line. A technique for keeping the quality of transmissions within specified parameters.

Rate Adaptive Digital Subscriber Line

See RADSL.

remote address

The IP address of a remote server.

Remote Authentication Dial-In User Service

See RADIUS.

remote server

A network computer that allows a user to log onto the network from a distant location.

Request for Comments

See RFC.

RFC

Request for Comments. The document series, begun in 1969, which describes the Internet suite of protocols and related experiments. Not all RFCs describe Internet standards, but all Internet standards are written up as RFCs.

route

The path that network traffic takes from its source to its destination. The route a datagram may follow can include many gateways and many physical networks. In the Internet, each datagram is routed separately.

router

A system responsible for making decisions about which of several paths network (or Internet) traffic will follow. To do this, it uses a routing protocol to gain information about the network and algorithms to choose the best route based on several criteria known as "routing metrics." See also bridge.

routing table

Information stored within a router that contains network path and status information. It is used to select the most appropriate route to forward information along.

RS-232

An EIA standard that is the most common way of linking data devices together.

S

SAP

Service Advertisement Protocol.

SDSL

symmetrical digital subscriber line.

secret

It is the encryption key used by RADIUS to send authentication information over a network.

serial line

A serial line is used to refer to data transmission over a telephone line via a modem or when data goes from a computer to a printer or other device.

Service Advertisement Protocol

See SAP.

shared secret

RADIUS uses the shared secret to encrypt the passwords in the authentication packets, so outside parties do not have access to the passwords on your network.

signal-to-noise ratio

See SNR.

SIMM

Single In-line Memory Module. A small circuit board or substrate, typically about 10cm x 2cm, with RAM integrated circuits or die on one or both sides and a single row of pins along one long edge.

Simple Network Management Protocol

See SNMP.

Single In-line Memory Module

See SIMM.

single-mode fiber

See SMF.

slot

A numbered location within a chassis capable of housing a module.

SMF

single-mode fiber.

SNMP

Simple Network Management Protocol. The network management protocol of choice for TCP/IP-based internets.

SNR

signal-to-noise ratio. Usable signal being transmitted divided by the noise or undesired signal.

socket

(1) The Berkeley Unix mechanism for creating a virtual connection between processes. (2) IBM term for software interfaces that allow two Unix application programs to talk via TCP/IP protocols.

Spanning-Tree Protocol

See STP.

spoofing

A method of fooling network end stations into believing that keep-alive signals have come from and return to the host. Polls are received and returned locally at either end of the network and are transmitted only over the open network if there is a condition change.

STP

Spanning-Tree Protocol. Part of an IEEE standard. A bridge protocol for detecting and preventing loops from occurring in a multibridged environment. When bridges connect three or more LAN segments, a loop can occur. Because a bridge forwards all packets which are not recognized as being local, some packets can circulate for long periods of time, eventually degrading system performance. This algorithm ensures only one path connects any pair of stations, selecting one bridge as the 'root' bridge, with the highest priority one as identifier, from which all paths should radiate.

STU-C

SDSL Transmission Unit—central office.

subnet

For routing purposes, IP networks can be divided into logical sub nets by using a subnet mask. Values below those of the mask are valid addresses on the subnet.

subnet mask

See address mask.

subordinate entity

An entity which has a superior entity.

subscriber

A logical entity with attributes identifying the customer that is receiving service on a particular LIM port.

superior entity

An entity which has subordinate entities.

SVC

switched virtual circuit. A temporary virtual circuit between two users.

switch

Equipment used to connect and distribute communications between a trunk line or backbone and individual nodes.

switched virtual circuit

See SVC.

symmetrical digital subscriber line

See SDSL.

synchronous connection

During synchronous communications, data is not sent in individual bytes, but as frames of large data blocks.

SYSLOG

SYSLOG allows you to log significant system information to a remote server.

T

T1

A digital carrier that is used to transmit a DS1 formatted digital signal at 1.544 Mbps.

T3

A digital carrier that is used to transmit a DS3 formatted digital signal at 45 Mbps.

TCP

Transmission Control Protocol. The major transport protocol in the Internet suite of protocols providing reliable, connection-oriented full-duplex streams.

Telnet

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

TFTP

Trivial File Transfer Protocol. A simple file transfer protocol (a simplified version of FTP) that is often used to boot diskless workstations and other network devices such as routers over a network (typically a LAN). Has no password security.

training

The procedure used by the ATU-C and ATU-R to establish an end-to-end ADSL connection.

training mode

Characteristic of a router that allows it to use RADSL technology to adjust its line speed according to noise conditions on the transmission line.

Transmission Control Protocol

See TCP.

transparent bridging

So named because the intelligence necessary to make relaying decisions exists in the bridge itself and is thus transparent to the communicating workstations. It involves frame forwarding, learning workstation addresses and ensuring no topology loops exist (in conjunction with the Spanning-Tree algorithm).

Trivial File Transfer Protocol

See TFTP.

twisted pair

Two insulated copper wires twisted together with the twists or lays varied in length to reduce potential signal interference between the pairs.

U

UDP

User Datagram Protocol. A connectionless transport protocol that runs on top of the TCP/IP IP. UDP, like TCP, uses IP for delivery; however, unlike TCP, UDP provides for exchange of datagrams without acknowledgments or guaranteed delivery. Best suited for small, independent requests, such as requesting a MIB value from an SNMP agent, in which first setting up a connection would take more time than sending the data.

UL

Underwriters Laboratories. A private organization that tests and certifies 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 and evaluated to nationally recognized safety standards with regard to fire, electric shock, and other related safety hazards.

Underwriters Laboratories

See UL.

UNI

User-Network Interface.

UNI signaling

User-Network Interface signaling for ATM communications.

upstream rate

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

User Datagram Protocol

See UDP.

V

VC

virtual circuit. A logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (PVC) or switched (SVC). In ATM, a virtual circuit is called a virtual channel. Sometimes abbreviated VC. See also PVC, SVC, VCI, and VPI.

VCC

virtual channel connection. Logical circuit, made up of links, that carries data between two end points in an ATM network. Sometimes called a virtual channel connection. See also VCI and VPI.

VCI

virtual channel identifier. 16-bit field in the header of an ATM cell. The VCI, together with the VPI, is used to identify the next destination of a cell as it passes through to the ATM switch. Sometimes called virtual channel connection. See also VPI.

virtual channel

See VC.

virtual circuit

See VC.

virtual channel connection

See VCC.

virtual channel identifier

See VCI.

virtual connection

In ATM, a connection between end users that has a defined route and endpoints. See also PVC and SVC.

virtual path

A logical grouping of virtual circuits that connect two sites. See also virtual circuit.

virtual path identifier

See VPI.

virtual path identifier/virtual circuit identifier

See VPI and VCI.

VP

virtual path. One of two types of ATM circuits identified by a VPI. A virtual path is a bundle of virtual circuits, all of which are switched across a network based on a common VPI. See also VPI.

VPI

virtual path identifier. An 8-bit field in the header of an ATM cell. The VPI, together with the VCI, is used to identify the next destination of a cell as it passes through the network. See also VCI.

W

WAN

wide-area network. A data communications network that spans any distance and is usually provided by a public carrier (such as a telephone company or service provider).

wide-area network

See WAN.