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1000Base-LX - A variant of Gigabit Ethernet which runs on multi-mode and single mode fiber optic cable at a 1330 um frequency.

1000Base-SX - A variant of Gigabit Ethernet which runs on multi-mode fiber optic cable at an 850 um frequency.

1000Base-T - A variant of Gigabit Ethernet which runs on unshielded twisted pair cable.

ACR (Attenuation to Crosstalk Ratio) - The difference between attenuation and crosstalk measured in decibels.

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 ) - A U.S. standard body. ANSI is a member of the International Organization for Standardization (ISO)

ATM (Asynchronous Transfer Mode ) - A high-speed, connection-oriented switching and multiplexing technology for transmitting information across a wide area or local area network. ATM divides information into fixed-length cell capable of transmitting different types of traffic simultaneously, including voice, video, and data.

Attenuation - The progressive weakening of a signal as it travels away from its point of origin.

AUI (Attachment Unit Interface) - Defined in the IEEE802.1 specification as the interface between an Ethernet MAU and DTE. Basically, the way an Ethernet station connects to a transceiver sitting on a thick Ethernet Cable.

AWG (American Wire Gauge ) - A standard for determining wire size. The gauge varies inversely with the actual wire diameter.

Backbone - LAN or WAN connectivity between subtends across a high-speed network. Often applied to a high-speed campus network, such as ATM OC-12or GIGABIT Ethernet., that interconnects lower speed networks, such as ATM OC-3 or Fast Ethernet. Fiber optic cable is often used.
Balance - An indication of signal voltage equality and phase polarity on a conductor pair. Perfect balance occurs when the signals across a twisted-pair are equal in magnitude and opposite in phase with respect to ground.

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 modulation device. Baseband is generally 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 used baseband.

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

Bonding - The permanent joining of metallic parts to form an electrically conductive patch 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.

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

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

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

Campus Backbone - Cabling between building that share telecommunications facilities.

Channel - The end-to-end transmission patch 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.

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 that two, 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.

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 o pair to another.

DCE (Data Circuit-terminating equipment) - The designation given to equipment such as modems and multiplexes by the Electronic Industry of America (EIA). Differs from DTE (Data Terminal Equipment) in that it transmits data on pin3 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.

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.

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.

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

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 cooper data/voice cable and interferes with transmission.

Ethernet - The most common layer-two protocol used in LANs. Ethernet is a 10Mbps CSMA/CD standard originally developed by Xerox to run on thick coaxial cabling. It has evolved and now runs primarily on twisted pair cabling.
Fast Ethernet 
- A version of Ethernet which operates at 100 Mbps. See 100Base-Tx and 100Base-FX.

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 Distributed Data Interface (FDDI)-A high speed networking technology based on fiber optics. The topology of FDDI LANs is dual-attached, counter-rotating Token Rings.

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.

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 it used in public and private networks, gradually replacing X.25 and leased-line networks.

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.

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.

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.

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.

IDC (Insulation Displacement Contact ) - A type of wire terminating connection in which the insulating jackets 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”

IEEE802.1p - An IEEE standard for prioritizing time-critical flows and filtering multicast traffic to contain traffic in layer-two networks. The 802.1p 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 802.1Q.

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 ands protocols, especially HTTP and HTML, within an organization.

 Kbps - Thousands of bits per second.

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 ot 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.

Mpbs - 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.

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 informaiton.

Multi-mode – A form of fiber optic cabling in which light in 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 divisionmultiplexing, 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.

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.

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 crossconnections 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.

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.

POTS – Plain Old Telephone System

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.

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

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

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 – 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.

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.

Signaling – The process of sending information over media.

Single Mode – 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.

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.

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

Station Cabling – See “Horizontal Cabling”.

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

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.

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

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 16Mbps.

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 fo rsending 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.

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 all the workstations and servers with a particular IP subnet address, which are grouped into a broadcast domain.

WAN (Wide Area Network) – A network which covers a larger geographical area than a single end user location, and in which telecommunications links are implemented; normally leased from service provider(s).

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