Cnna Final Exam Review Edition 7 Chapter 4

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110Block

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Atype of punch-down block designed to terminate Cat 5 or bettertwisted-pair wires and typically used to handle data connectionsrather than telephone connections. The numeral 110 refers to themodel number of the earliest blocks.

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42U

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U(rack unit) The industry-standard unit for measuring rack height.Standard racks are 42U tall—about 6 feet. Most rack mountablecomputers are 1U—4U high, whereas a server may only require 1U.

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Airflow

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na chassis, the path along which air from a cool air source isconducted, past equipment to cool it, and then out of the rack.Typically, air moves from front to back. Clutter in the rack shouldbe minimized to prevent airflow blockages

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Backbone

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Thecentral conduit of a network that connects network segments andsignificant shared devices (such as routers, switches, and servers)and is sometimes referred to as “a network of networks.

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BendRatio

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Theradius of the maximum arc into which a cable can be looped withoutimpairing data transmission. Generally, a twisted-pair cable’s bendradius is equal to or greater than four times the diameter of thecable.

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Blackout

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Acomplete power loss

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Brownout

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Amomentary decrease in voltage, also known as a sag. An overtaxedelectrical system may cause brownouts, recognizable as a dimming ofthe lights.

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Collisions

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(1)In Ethernet networks, the interference of one node’s datatransmission with the data transmission of another node sharing thesame segment. (2) In the context of hashing, a problem that occurswhen the input of two different data sets result in the same hashvalue.

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CRC

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(cyclicredundancy check) An algorithm (or mathematical routine) used toverify the accuracy of data contained in a data frame.

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CSMA/CD

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CSMA/CD(Carrier Sense Multiple Access with Collision Detection) A networkaccess method specified for use by IEEE 802.3 (Ethernet) networks. InCSMA/CD, each node waits its turn before transmitting data to avoidinterfering with other nodes’ transmissions. If a node’s NICdetermines that its data has been involved in a collision, itimmediately stops transmitting. Next, in a process called jamming,the NIC issues a special 32-bit sequence that indicates to the restof the network nodes that its previous transmission was faulty andthat those data frames are invalid. After waiting, the NIC determinesif the line is again available; if it is available, the NICretransmits its data

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Demarc

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Thepoint of division between a telecommunications service carrier’snetwork and a building’s internal network.

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Duplex

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(akaFull- Duplex) Signals are free to travel in both directions over amedium simultaneously.

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EMI

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Atype of interference that can be caused by motors, power lines,televisions, copiers, fluorescent lights, or other sources ofelectrical activity.

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Entrancefacility

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Thelocation where an incoming network service (whether phone, Internet,or long-distance service) enters a building and connects with thebuilding’s backbone cabling.

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EthernetII

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TheEthernet frame type developed by Digital Equipment Corporation,Intel, and Xerox (collectively called DIX), before the IEEE began tostandardize Ethernet. Ethernet II is distinguished from otherEthernet frame types in that it contains a 2-byte type field toidentify the upper-layer protocol contained in the frame. It supportsTCP/IP and other higher-layer protocols.

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FaultTolerance

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(1)Techniques that allow data storage or other operations to continue inthe event of a failure or fault of one of its components, forexample, storing redundant data on multiple storage devices in theevent one device fails. (2) A system’s ability to continueperforming despite an unexpected hardware or software malfunction.

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Florescentlights can cause

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EMI

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HorizontalWiring

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Thewiring that connects workstations to the closest data closet.

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IDF

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(intermediatedistribution frame) A junction point between the MDF andconcentrations of fewer connections for example, those that terminatein a data closet.

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Inverter

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Adevice that converts DC electrical energy to AC electrical energy.Better inverters will also condition the power, which helps protectsensitive electronic equipment from power fluctuations

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iSCSI

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(InternetSCSI) A Transport layer protocol used by SANs that runs on top of TCPto allow fast transmission over LANs, WANs, and the Internet.

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JumboFrame

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Asetting on Ethernet network devices that allows the creation andtransmission of extra-large frames, as high as 9198 bytes, dependingon the type of Ethernet architecture used.

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KVM

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Adevice that connects the equipment in a rack to a single console toprovide a central control portal for all devices on the rack

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MDF

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(maindistribution frame) Also known as the main cross connect, the firstpoint of interconnection between an organization’s LAN or WAN and aservice provider’s facility.

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Noise

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Fluctuationin voltage levels caused by other devices on the network or EMI. Somenoise is unavoidable on an electrical circuit, but excessive noisecan cause a power supply to malfunction, immediately corruptingprogram or data files and gradually damaging motherboards and othercomputer circuits

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Patchcable

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Arelatively short section (usually between 3 and 25 feet) of cablingwith connectors on both ends that connect two devices.

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Plenum

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Thearea above the ceiling tile or below the subfloor in a building

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PowerConverter

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Adevice that changes the form of electrical energy in some way. Fourcommon types are inverter, rectifier, transformer, and voltageregulator.

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PVC

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Apermanent virtual circuit (PVC) is a connection that is permanentlyestablished between two or more nodes in frame relay and asynchronoustransfer mode (ATM) based networks. It enables the creation of alogical connection on top of a physical connection between nodes thatcommunicate frequently or continuously.

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Rack

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Anopen or enclosed cabinet that holds network devices such as switches,routers, servers, and/or patch panels

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RackSystem

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Mountinghardware for network equipment that helps optimize the use of squarefootage in equipment rooms and helps ensure adequate spacing, access,and ventilation for those devices.Rectifier

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Sag

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Brownout

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SANs

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(storagearea network) A distinct network of storage devices that communicatedirectly with each other and with other networks. A SAN uses aproprietary network transmission method such as Fibre Channel ratherthan a traditional network transmission method such as Ethernet.

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StructuredCabling

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Amethod for uniform, enterprise-wide, multivendor cabling systemsspecified by the TIA/EIA 5 68 Commercial Building Wiring Standard.Structured cabling is based on a hierarchical design using ahigh-speed backbone

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Surge

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Amomentary increase in voltage caused by distant lightning strikes,solar flares, or electrical problems.

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TIA/EIA

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aset of telecommunications standards from the TelecommunicationsIndustry Association (TIA), an offshoot of the Electronic IndustriesAlliance (EIA). The standards address commercial building cabling fortelecommunications products and services.

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Transformer

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Adevice that changes the voltage of AC electrical energy, such as whenthe power over the main line from the electric company is transformedbefore being delivered to a house.

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U

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(rackunit) The industry-standard unit for measuring rack height. Standardracks are 42U tall—about 6 feet. Most rack mountable computers are1U—4U high, whereas a server may only require 1U.

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UPS

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(uninterruptiblepower supply) A battery-operated power source directly attached toone or more devices and to a power supply (such as a wall outlet)that prevents undesired fluctuations of the wall outlet’s AC powerfrom harming the device or interrupting its services.

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Verticalcross connect

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Partof a network’s backbone that supplies connectivity between abuilding’s floors. For example, vertical cross connects mightconnect an MDF and an IDF or IDFs and data closets within a building.

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VoltAmps

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Ameasure of electrical power. A voltampere, or volt-amp, is theproduct of the voltage and current (measured in amps) of theelectricity on a line