10Base-2
A variant of Ethernet, connecting stations via thin coaxial cable; maximum cable distance in one non-repeated segment is 185 meters.

10Base-FL
10BASE-FL is the most commonly used 10BASE-F specification of Ethernet over optical fiber. It replaces the original FOIRL specification, but retains compatibility with FOIRL-based equipment. Maximum segment length values 2000 meters. Mixing it with FOIRL equipment, maximum segment length reduces to FOIRL's 1000 meters.

10Base-T
10BASE-T supports Ethernet's 10 Mbps transmission speed using Category 5, 5e, 6 Ethernet cable.

100Base-FX
100Base-FX is a version of Fast Ethernet over optical fiber. It uses a 1300 nm near-infrared (NIR) light wavelength transmitted via two strands of multi-mode optical fiber, one for receive (RX) and the other for transmit (TX). Maximum length is 400 meters (1,310 ft) for half-duplex connections (to ensure collisions are detected) or 2 kilometers (6,600 ft) for full-duplex. 100BASE-FX uses the same 4B5B encoding and NRZI line code that 100BASE-TX does. 100BASE-FX should use SC, ST, or MIC connectors with SC being the preferred option.

100Base-TX
100BASE-TX is the predominant form of Fast Ethernet, and runs over two pairs of category 5 or above cable (a typical category 5 cable contains 4 pairs and can therefore support two 100BASE-TX links).

1000Base-LX
1000BASE-LX is a fiber optic gigabit Ethernet standard, using a long wavelength laser. Signaling speed 1.25±100 ppm GBd,  Wavelength 1270 to 1355 nm, RMS spectral width (max) 4 nm. Typically, GbE lasers will be specified as having a 1300 or 1310 nm wavelength.  1000BASE-LX is specified to work over a distance of up to 2 km over 9 µm single-mode fiber. In practice it will often operate correctly over a much greater distance. Many manufacturers will guarantee operation up to 10 or 20 km, provided that their equipment is used at both ends of the link. 1000BASE-LX can also run over multi-mode fiber with a maximum segment length of 550 m. For any link distance greater than 300 m, the use of a special launch conditioning patch cord may be required. This launches the laser at a precise offset from the center of the fiber which causes it to spread across the diameter of the fiber core, reducing the effect known as differential mode delay which occurs when the laser couples onto only a small number of available modes in multi-mode fiber.  Two strands of fiber are needed, one for each direction of the communication.

1000Base-SX
1000BASE-SX is a fiber optic gigabit Ethernet standard. It operates over multi-mode fiber using a 850 nanometer, near infrared (NIR) light wavelength. The standard specifies a distance capability between endpoints of 220 m over 62.5/125 µm fiber although in practice, with good quality fiber and terminations, 1000BASE-SX will usually work over significantly longer distances. Modern 50/125 µm fibers can reliably extend the signal to 500 m or more. This standard is highly popular for intra-building links in large office buildings, collocation facilities and carrier neutral internet exchanges. Typical optical power parameters of SX interface: maximum mean output power = -5 dB; stressed receiver sensitivity = -14 dB.

1000Base-T
1000BASE-T (also known as IEEE 802.3ab) is a standard for gigabit Ethernet over copper wiring. It requires, at a minimum, Category 5 cable, but Category 5e ("Category 5 enhanced") and Category 6 cable may also be used and are often recommended.

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Access Point
is a device that connects wireless communication devices together to form a wireless network. The WAP usually connects to a wired network, and can relay data between wireless devices and wired devices. Several WAPs can link together to form a larger network that allows "roaming". (In contrast, a network where the client devices manage themselves - without the need for any access points - becomes an ad-hoc network.) WAPs have IP addresses for configuration.

ACR
(Attenuation to Crosstalk Ratio) is the ratio of the attenuated signal to near-end crosstalk (NEXT). It's a factor in determining how far a signal can be transmitted in any given medium.
 
Adapter card - See "NIC".

Amplitude
In communications, the distance between the highest and lowest points in a wave. The amplitude controls the strength, or volume, of the signal.

ANSI
(American National Standards Institute) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international standards so that American products can be used worldwide. For example, standards make sure that people who own cameras can find the film they need for them anywhere around the globe.

Attenuation
is the reduction in amplitude and intensity of a signal. Signals may be attenuated exponentially by transmission through a medium, in which case attenuation is usually reported in dB with respect to distance traveled through the medium. Attenuation can also be understood to be the opposite of amplification.

AUI
(Attachment Unit Interface) is a 15 pin connection that provides a path between a node's Ethernet interface and the Medium Attachment Unit (MAU), sometimes known as a transceiver.

Auto-Negotiation (N-Way)
A mechanism that controls the data when a connection is established to a network device. It automatically switches to the correct technology in the following sequence:

1) 100Base-TX, Full Duplex
2) 100Base-T4
3) 100Base-TX
4) 10Base-T, Full Duplex
5) 10Base-T

With the following benefits:

1) Automatic Connection
2) Backward Compatibility
3) Network Protection
4) Technology Extension
5) Path Upgrade
6) Management Interface
7) Proprietary Extension

AWG
(American Wire Gauge) also known as the "Brown and Sharpe" wire gauge, is used in the United States and other countries as a standard method of denoting wire diameter, especially for nonferrous, electrically conducting wire.

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Backbone
A backbone network provides a path for the exchange of information between different LANs or sub networks.  A backbone can tie together diverse networks in the same building, in different buildings in a campus environment, or over wide areas. Normally, the backbone's capacity is greater than the networks connected to it.

Balance
Balance can mean the amount of signal from each channel reproduced in a stereo audio recording. Typically, a balance control will have 0 dB of gain in the center position for both channels, and attenuate one channel as the control is turned, leaving the other channel at 0 dB.

Balanced Signal Transmission
Two voltages, equal and opposite in phase with respect to each other, across the conductors of a twisted-pair

Balun
Balanced/unbalanced. An impedance matching device used to connect balanced twisted pair cabling with unbalanced coaxial cable.

Bandwidth
(1) The range of signal frequencies that can be carried on a communications channel. The capacity of a channel is measured in cycles per second, or hertz (Hz), between the highest and lowest frequencies. (2) Commonly, the carrying capacity of a digital translation facility, measured in bits per second (bps).

Baseband
A technique whereby digital input is directly applied to transmission media without the intervention of a modulating device. Baseband is generally applied in an environment with high bandwidth over a short distance. It is generally considered easier and more cost-effective than broadband. Ethernet, token ring, FDDI, and ATM generally use baseband.

Bend Loss
Increased attenuation in a fiber that results from the fibers being bent, or from minute distortions within the fiber.

Bit
A contraction of Binary Digit. The smallest unit of digital information.

Bit Rate (BR)
The rate of data throughput on the medium in bits per second. Ethernet specifies 10 million bits per second.

Bit Time
The duration of one bit symbol (1/BR). Ethernet specifies a bit time of 100 ns.

BNC Connector
A specific type of connector used for coaxial RG58 cable connection.

Bonding
The permanent joining of metallic parts to form an electrically conductive path that will assure electrical continuity and the capacity to conduct safely any current likely to be imposed on it.

bps (Bits per second)
The amount of data transferred in a second.

Bridged Tap
The multiple appearances of the same cable pair or fiber at several distribution points.

Bridging
A means of providing through connections between conductors or pairs that are terminated on connecting blocks. These through connections are commonly provided by means of individual metallic "bridging" clips or multiple "bridging" clips that are housed in a plastic insulator.

Broadband
Characteristic of any network that multiplexes multiple, independent carrier signals onto a single cable. This is usually accomplished through frequency division multiplexing. Broadband technology allows several signals to coexist on a single cable; traffic from one signal does not interfere with traffic from another, since data is transmitted on a different frequency. Cable television uses broadband.

Buffer
A block of storage used to hold a portion of an information packet.

Bundled Cable
An assembly of two or more cables continuously bound together to form a single unit prior to installation.

Bus (linear bus)
A network topology in which all computers are connected by a single length of cabling with a terminator at each end.

Bus topology
A network structure in which the signals sent by one device are received by all other devices. Each device then selects those transmissions addressed to it based on address information contained in the transmission.

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Cabling
A combination of cables, wire, cords and connecting hardware used in the telecommunications infrastructure.

Campus Backbone
Cabling between buildings that share telecommunications facilities.

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
The LAN access method used in Ethernet. When a device wants to gain access to the network, it checks to see if the network is quiet (senses the carrier). If it is not, it waits a random amount of time before retrying. If the network is quiet and two devices access the line at exactly the same time, their signals collide. When the collision is detected, they both back off and each wait a random amount of time before retrying.

Channel
The end-to-end transmission path connecting any two points at which application specific equipment is connected.

Cladding
In fiber-optic cabling, a layer of glass that surrounds the inner core and reflects light back into the core.

Class I Repeater
Class I Repeaters operate by translating line signal on the incoming port to a digital signal. This allows the translation between different types of Fast Ethernet like 100Base-TX and 100Base-FX. Class I repeaters introduce delays when performing this conversion so that only one repeater can be put in a single Fast Ethernet LAN segment.

Class II Repeater
Class II Repeaters immediately repeat the signal on the incoming port to all the ports on the repeater. This quick movement of the data introduces Very little delay across the repeater, thus two class II repeaters are allowed per Fast Ethernet segment.

Coaxial Cable (Coax)
Formerly common in Ethernet networks, coax comes in various types with different transmission characteristics. It is copper-based, with an inner conductor surrounded by an outer conductor, with insulation between the two, insulation around the outer conductor, and a jacket. Coax is less flexible than twisted pair cable, but more resistant to EMI and physical breakage.

Collision
Concurrent Ethernet transmissions from two or more devices on the same segment. A collision is sensed by the transmitting station as an over-voltage condition causing the station to retransmit after waiting a random amount of time.

Collision Domain
Single CSMA/CD LAN segment.

Cross-connect
A facility enabling the termination of cables as well as their interconnection or cross-connection with other cabling or equipment.

Crosstalk
The unwanted introduction of signals from one channel or pair to another.

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Data Communications Equipment (DCE)
Traditional data communications terminology for the equipment that enables a DTE to communicate over a telephone line or data circuit. The DCE establishes, maintains, and terminates a connection as well as performing the conversions necessary for communications.

Data Terminal Equipment (DTE)
Traditional data communications terminology for a device receiving and/or originating data on a network. Typically, a computer or patch panel.

DCE (Data Circuit-terminating equipment)
The designation given to equipment such as modems and multiplexers by the Electronic Industry of America (EIA). Differs from DTE (Data Terminal Equipment) in that it transmits data on pin 3 and receives data on pin 2.

Decibel (dB)
A logarithmic comparison of power levels defined as ten times the base ten log of the ratio of input power to output power. One tenth of a bel.

Demarcation Point
The point inside your building (or on the campus premises) at which the phone company (or other service provider) is no longer responsible for network cabling or service.

Digital Line
A data or voice network interconnectivity medium that supports digital signaling.

DSL (Digital Subscriber Line)
A method for moving data over regular phone lines. A DSL circuit is much faster than a regular phone connection and uses the same copper premises wires used for regular phone service. A DSL circuit must be configured to connect two specific locations, similar to a leased line. DSL is now a popular alternative to ISDN and leased lines, being faster than ISDN and less costly than traditional leased lines.

D-Sub connector
AUI cable use 15-pin D-sub connectors. "D" refers to the shape of the connector shell. Also called miniature D, DB-15, or DIX connectors.

DTE (Data Terminal Equipment)
The RS232-C Standard referring to equipment that transmits and/or receives data on a network. This standard typically applies to terminals, PCs, and printers.

D-Type
The standard connector used for RS232-C, RS423 and RS422 communication. It is most commonly used in 9, 15, and 25-pin configurations.

Duplex
A technique allowing bi-directional, simultaneous transmission along a channel. Generally referred to as full duplex.

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EIA
Electronic Industries Association

EIA 568
A commercial building wiring standard for voice and data communications developed in 1989 by EIA.

ELFEXT (Equal Level Far-end Crosstalk)
Crosstalk measured at the opposite end from which the disturbing signal is transmitted, normalized by the attenuation contribution of the cable or cabling.

EMI (Electromagnetic Interference)
Energy generated by outside sources, such as lighting systems and electric motors, which is received by copper data/voice cable and interferes with transmission.

Ethernet
The most common layer-two protocol used in LANs. Ethernet is a 10 Mbps CSMA/CD standard originally developed by Xerox to run on thick coaxial cabling. It has evolved and now runs primarily on twisted pair cabling.

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Fast Ethernet
A version of Ethernet which operates at 100 Mbps. See 100Base-Tx and 100Base-FX.

FDDI (Fiber Distributed Data Interface)
A high-speed networking standard. The underlying medium is fiber optics and the topology is a dual-attached, counter-rotating Token Ring. The FDDI protocol has also been adapted to run over traditional copper wires.

Fiber Channel
A form of high-speed fiber optic transmission designed primarily for communications between mainframe computers, and between mainframe computers and high-speed peripherals such as disk drives. Sometimes used for general-purpose networking.

Fiber Optic Cable
A type of cable consisting of glass or plastic fibers that are used to carry light signals. Fiber optic cable supports transmission speeds up into the 100Mbps.

Fiber Optic Transmission
A communications scheme whereby electrical data is converted to light energy and transmitted through optical fibers.

FOIRL (Fiber Optic Inter Repeater Link)
A fiber optic signaling method based on the IEEE 802.3 standard governing fiber optics. Allows up to 1,000 meters (3,280 ft.) of multi-mode duplex fiber optic cable in a point-to-point link.

Frame Relay
An ITU standard for the interface to a public frame-switching network designed to provide high-speed frame transmission with minimum delay across the wide area. It operates at layer two, and is used in public and private networks, gradually replacing X.25 and leased-line networks.

Full-Duplex
A communications method in which a transmission path is provided in each direction, so that each end can simultaneously transmit and receive.

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Gbps
Billions of bits per second.

Gigabit Ethernet
A variant of Ethernet which operates over multi-mode fiber optic cable, single mode fiber optic cable, or unshielded twisted pair, at 1,000 Mbps.

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Half-Duplex
A communications method in which one end transmits while the other receives, then the process is reversed. This was common in wide area point-to-multipoint circuits, such as those used in many SNA networks.Head End -A central point in a broadband network that receives signals on one set of frequency bands and retransmits them on another set of frequencies. The head end is viewed as a central hub. Every transmission on a broadband network must go through the head end.

Head End
A central point in a broadband network that receives signals on one set of frequency bands and retransmits them on another set of frequencies. The head end is viewed as a central hub. Every transmission on a broadband network must go through the head end.

Horizontal Cabling
That portion of a building's cabling system which extends from the wiring closets to the individual workstations, servers, telephones, and other devices. This is generally copper twisted pair cable.

Hot Swapping
The process of replacing a module without bringing down the system. This process occurs by sliding an active module into or out of a fully powered unit without shutdown.

Hub
The center of a star topology network or cabling system. Typically used in older Ethernet and token ring networks. A device connected to a hub receives all the transmissions of all other devices connected to that hub. Hubs are now being replaced in many cases by LAN switches.

Hybrid cable
An assembly of two or more cables, of the same or different types or categories, covered by one overall sheath.

Hybrid Network
A LAN consisting of a number of topologies and access methods. For example, a network that includes both token ring and Ethernet.

HZ (Hertz)
A measure of frequency or bandwidth.

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IDC (Insulation Displacement Contact)
A type of wire terminating connection in which the insulating jacket is cut by the connector when the wire is inserted.

IEEE (Institute of Electrical and Electronic Engineers)
A standards-making body responsible for implementing many standards used in LANs, including the 802.x series.

IEEE 802.1D
See "Spanning Tree".

IEEE 802.1p
An IEEE standard for prioritizing time-critical flows and filtering multicast traffic to contain traffic in layer-two networks. The 802.1 p header includes three bits for prioritization, allowing for eight priorities to be established.

IEEE 802.1Q
An IEEE standard for providing a virtual LAN capability within a campus network, used in conjunction with IEEE LAN protocols such as Ethernet and token ring.

IEEE 802.2
A data link standard outlining how basic data connectivity over cable should be set up. Used with the IEEE 802.3, 802.4 and 802.5 standards.

IEEE 802.3
The IEEE's specification for Ethernet, including both physical cabling and layer-two protocol.

IEEE 802.5
The IEEE's specification for token ring, including both physical cabling and layer-two protocol.

IEEE 802.10
The IEEE's protocol for providing security in a metropolitan area network. A variant of 802.10 has sometimes been used to provide a virtual LAN service within a campus network, although this is now generally replaced with 802.1 Q.

IEEE 802.11b

Insertion Loss
The amount of the signal that is lost (attenuation) as the signal passes through a connection or interface.

Internetwork
Two or more networks connected by bridges or routers.

Intranet
The use of various Internet tools and protocols, especially HTTP and HTML, within an organization.

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Kbps
Thousands of bits per second.

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LAN (Local Area Network)
(1) The network which interconnects all computing devices located within a single end user location; e.g., an integrated token ring / ATM network covering an entire campus. (2) A single layer-two network, which may be connected to other such networks within an end user location; e.g., a single Ethernet segment. To avoid confusing the two definitions, Xylan commonly refers to the former as a "campus" network.

LED
Light Emitting Diode.

Link
An end-to-end transmission path provided by the cabling infrastructure. Cabling links include all cables and connecting Equipment and work area cables are not included as part of a link.

Local Exchange Carrier (LEC)
The local regulated provider of public switched telecommunications services.

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MAC (Media Access Control)
The way LAN workstations share access to a transmission medium. MAC-layer protocols include Ethernet, token ring, and FDDI. This MAC has absolutely nothing to do with the Apple Macintosh computer.

MAC Address
The layer-two address of a LAN device.

MAU (Media Access Unit)
In token ring, a hub which interconnects the devices connected to the ring, and in turn connects to other MAUs through Ring-In / Ring-Out connections. Generally, a MAU is not managed via software.

Mbps
Millions of bits per second.

MDF (Main Distribution Frame)
In a structured building wiring system, the central point for cabling throughout the building. Typically, multiple IDFs located in wiring closets connect to a central MDF.

MII (Media Independent Interface)
The standard interface for Fast Ethernet. It is similar to the AUI interface for traditional Ethernet.

MMJ (Modified Modular Jack)
A six-wire modular jack with the locking tab shifted off to the right side. Used in the DEC wiring system.

Modulation
The process of modifying a carrier signal to transmit information.

MT-RJ
A type of dual fiber optic connector: small size, lower cost, more flexible application and easier use. The MT-RJ system supports both Single Mode and Multi-Mode applications, providing a robust solution for both backbone and horizontal needs. About half the size of an SC-based transceiver, the MT-RJ presents significant space savings. The narrower width allows network equipment vendors to achieve the same port density as with modular jacks.

Multi-mode
A form of fiber optic cabling in which light is able to follow multiple paths as it traverses the cable. Less expensive, and with a lower maximum rate and distance, than single mode fiber optic cable.

Multiplex
To transmit two or more messages or message streams on a single channel, typically through the use of frequency-division multiplexing, time division multiplexing, or statistical time division multiplexing.

Multiplexer
A device used for division of a transmission facility into two or more subchannels, either by splitting the frequency band into narrower bands or by allotting a common channel to several different transmitting devices one at a time. Also known as a mux.

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NEXT (Near End Crosstalk)
Signal distortion as a result of signal coupling from one pair to another at various frequencies.

Network
A number of interconnected systems that, typically, exchange information with one another and share resources that may be distributed among the systems.

NIC (Network Interface Card)
A physical plug-in module which goes into a workstation or server and provides the connection to a network.

Node
Any network device (such as a server, workstation, or router) that can communicate across the network.

Noise
A low-voltage, low-current, high-frequency signal that interferes with normal network transmissions, often data.

N-Way
See "Auto-Negotiation".

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Parallel Detection
The method of establishing a link between auto-negotiation and non-negotiation devices

Patch Cord
The connecting cord between the terminal device and the drop.

Patch Panel
Connecting hardware that typically provides means to connect horizontal or backbone cables to an arrangement of fixed connectors that may be accessed using patch cords or equipment cords to form cross-connections or interconnections.

Phase
The amplitude of a cyclic signal at a specific point in time.

Plant
The cables that connect computers together in a LAN

Plenum
A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system.

Port
An interface of a computer or other transmission device that acts as an input and/or output point.

POTS
Plain Old Telephone System

Propagation Delay
The amount of time that passes between when a signal is transmitted and when it is received at the opposite end of a cable or cabling.

Protocols
The specifications that define procedures used by computers when they transmit and receive data.

Punch Down
A method for securing wire to a quick clip in which the insulated wire is placed in the terminal groove and pushed down with at special tool.

PVC (Poly-vinyl Chloride)
The material most commonly used for the insulation and jacketing of cable.

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Return Loss
Noise or interference caused by impedance discontinuities along the transmission line at various frequencies. Return loss is expressed in decibels.

RFI (Radio Frequency Interference)
Noise created in the radio-frequency range.

Riser Cabling
That portion of a building's cabling system which extends from the main distribution frame to the wiring closets. For data, this is often fiber optic cable. For voice, it is fiber optic cable if the PBX is distributed, and twisted pair copper cable otherwise.

RJ-11/12
A standard connector commonly used to terminate voice connections.

RJ-45
A standard connector commonly used to terminate data connections.

RS-232-C
An Electrical Industries Association (EIA) Standard for the physical interface between Data Terminal Equipment (DTE) and Data Circuit Terminating Equipment (DCE).

Router
A layer-three device responsible for making decisions regarding which of several paths network 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). Routers interconnect subnets.

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SC
A type of optical fiber connector. The SC utilizes the same 2.5mm ferrule as the ST, held in a housing that allows for "push-pull" insertion and removal of the connector of choice for data networks.

ScTP (Screened Twisted Pair)
Copper cable that includes one or more sets of cable pairs which have been molded into an insulating material and covered by a braided shielding conductor. STP offers better noise protection than unshielded twisted pair (UTP) but is much more expensive and more difficult to use. Commonly associated with early token ring networks.

Signaling
The process of sending information over media.

Single Mode fiber
A form of fiber optic cabling in which light follows a single path as it traverses the cable. More expensive, and with a higher maximum rate and distance, than multi-mode fiber optic cable.

SNMP (Simple Network Management Protocol)
An IAB protocol designed to manage networking devices. With SNMP, a management station can configure a supported device (SET), request that the device send statistical, status, and configuration information (GET), and receive unsolicited alarms from the device (TRAP).

SOHO
Small Office / Home Office

Spanning Tree
A protocol specified in the IEEE 802.1 D standard which allows a network to have a topology that contains physical loops. Spanning Tree operates in bridges and switches. It opens certain paths to create a tree topology, thereby preventing packets from looping endlessly on the network.

SQE test
A special 802.3 signal sent by MAU to the DTE to test the collision detection function. Commonly referred to as Heartbeat. DTEs request the SQE signal; repeaters do not.

ST
A registered trademark of AT&T for their fiber optic connector. Originally, an acronym for "Straight Tip".

Star
A network topology in which each node is connected to a central point.

Station Cabling
See "Horizontal Cabling".

Store and Forward
A method of switching in which a message is received as a whole, buffered, and then resent. All routers and virtually all current switches work in this manner. This method ensures that information being forwarded is free of errors.

STP (Shielded Twisted Pair)
Copper cable that includes one or more sets of cable pairs which have been molded into an insulating material and covered by a braided shielding conductor. STP offers better noise protection than unshielded twisted pair (UTP) but is much more expensive and more difficult to use. Commonly associated with early token ring networks.

Surge
A rapid rise in current or voltage, usually followed by a fall back to a normal level. Also known as transient.

Switch, Ethernet
The Ethernet switch functions like a bridge to isolate traffic and separate collision domains. It’s objective is to increase throughput to each user by decreasing the number of stations that compete for the shared bandwidth. It also maintains a matrix of destination addresses and the physical ports associated with each address, so that it can switch frames/packets. An incoming frame/packet is only transmitted on the port associated with the frame’s destination address. The number of destination addresses is dependent on the vendor model of a switch, but can range from one to over one thousand.

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TC (Telecommunications Closet)
Central location for termination and routing of on-premises wiring systems.

T-Connectors
Connectors used to join thin Ethernet cable sections. The connectors also have a connector that is attached directly to a station.

TIA (Telecommunications Industry Association)
An organization that sets standards for cabling, pathways, spaces, grounding, bonding, administration, field testing and other aspects of the telecommunications industry.

Token ring
A network architecture standardized in IEEE 802.5 in which the devices on a ring transmit data while they are in possession of a token which passes from node to node continuously. Token ring operates at 4 or 16 Mbps.

Topology
Can be either physical or logical. Physical topology describes the physical connections of a network and the geometric arrangement of links and nodes that make up that network. Logical topology describes the possible logical connections between nodes, and indicates which pairs of nodes are able to communicate.

TP-PMD
Twisted Pair Physical Media Dependent. ANSI X3T9.5 Committee’s proposed 100 Mbps over UTP Standard. Also referred to as CDDI (Copper Distributed Data Interface).

Transceiver
A device used in contention networks for sending and receiving data over the same network.

Transient
A high-voltage burst of electric current, usually lasting less than 1 second, occurring randomly.

Trunk Cable
Typically refers to a copper twisted pair backbone or vertical riser cable consisting of multiple groups of 25 pairs.

Twisted Pair
Insulated copper wires twisted together with the twists or lays varied in length to reduce potential signal interference between the pairs. They are usually bundled together and wrapped in a cable sheath. New data grade Unshielded Twisted Pair (Category 5) is specified for 100 Mbps transmission.

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UTP (Unshielded Twisted-Pair)
A type of twisted-pair wire that has no metalized outer covering, shielding the pairs of wire. The pairs are typically covered with a plastic sheath.

USOC (Uniform Service Ordering Code)
A term originally used by the telephone company to specify installation of a standard modular jack.

VLAN (Virtual Local Area Network)
In a switched network, a logical collection of devices, such as workstations and servers with a particular IP subnet address, which are grouped into a broadcast domain. Usually, this domain is software based as opposed to a physical LAN, which is defined entirely by wiring.

VF-45
A fiber connector using V-groove technology instead of ferrules used in traditional SC fiber-optic connectors. The mechanical connection formed with the V-grooves reduces installation time from approximately 15 minutes to 2 minutes. The connector is tested to ISO-11801, the current TIA-568-A premises cabling standards, and the corresponding component standards. The Fiber Channel Association ASC-x3t11 Technical Committee adopted the design in February 1997 as the new, small-form factor interface for future variants of Fiber Channel.

VLAN (Virtual Local Area Network)
In a switched network, a logical collection of devices, such as all the workstations and servers with a particular IP subnet address, which are grouped into a broadcast domain.

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WAN (Wide Area Network)
A network that covers a larger geographical area such as a state or country.

Workstation
A terminal station, usually connected to a LAN, providing local processing capability and storage as well as access to other workstations and shared resources.