1000BASE-LX—A Physical layer standard for networks that specifies 1-Gbps transmission over fiber-optic cable using baseband transmission.. 1000BASE-SX—A Physical layer standard for netw
Trang 311. supported services list
12. change management system
13. crossover
14. tone locator
15. ohms
Trang 414. private key, symmetric
15. IPSec, Internet Protocol
Trang 61 gigabit per second (Gbps)—1,000,000,000 bits per second.
1 kilobit per second (Kbps)—1000 bits per second.
1 megabit per second (Mbps)—1,000,000 bits per second.
1 terabit per second (Tbps)—1,000,000,000,000 bits per second.
1000BASE-CX—A Physical layer standard for achieving 1-Gbps throughput over twinaxial copper
wire 1000BASE-CX segments are limited to 25 meters, and are useful mainly to connect devices such
as servers or switches
1000BASE-LX—A Physical layer standard for networks that specifies 1-Gbps transmission over
fiber-optic cable using baseband transmission 1000BASE-LX can run on either single-mode or multimodefiber The “LX” represents its reliance on “long wavelengths” of 1300 nanometers 1000BASE-LX canextend to 5000-meter segment lengths using single-mode, fiber-optic cable 1000BASE-LX networkscan use one repeater between segments
1000BASE-SX—A Physical layer standard for networks that specifies 1-Gbps transmission over
fiber-optic cable using baseband transmission 1000BASE-SX runs on multimode fiber Its maximum segmentlength is 550 meters The “SX” represents its reliance on “short wavelengths” of 850 nanometers.1000BASE-SX can use one repeater
1000BASE-T—A Physical layer standard for achieving 1 Gbps over UTP 1000BASE-T achieves its
higher throughput by using all four pairs of wires in a CAT 5 or higher twisted-pair cable to both mit and receive signals 1000BASE-T also uses a different data encoding scheme than that used by otherUTP Physical layer specifications
trans-100BASE-FX—A Physical layer standard for networks that specifies baseband transmission, multimode
fiber cabling, and 100-Mbps throughput 100BASE-FX networks have a maximum segment length of
2000 meters 100BASE-FX may also be called Fast Ethernet
100BASE-T—A Physical layer standard for networks that specifies baseband transmission, twisted-pair
cabling, and 100-Mbps throughput 100BASE-T networks have a maximum segment length of 100meters and use the star topology 100BASE-T is also known as Fast Ethernet
100BASE-TX—A type of 100BASE-T network that uses two wire pairs in a twisted-pair cable, but uses
faster signaling to achieve 100-Mbps throughput It is capable of full-duplex transmission and requiresCAT 5 or higher twisted-pair media
10BASE-2—See Thinnet.
10BASE-5—See Thicknet.
10BASE-F—A Physical layer standard for achieving 10-Mbps throughput over multimode fiber-optic
cable Three different kinds of 10BASE-F exist All require two strands of multimode fiber, in which onestrand is used for data transmission and one strand is used for reception, making 10BASE-F a full-duplextechnology
Trang 710BASE-FL—The most popular version of the 10BASE-F standard 10BASE-FL is designed to
con-nect workstations to a LAN or two repeaters and can take advantage of fiber-optic repeating technology
to reach its maximum segment length of 2000 meters 10BASE-FL makes use of the star topology, withits repeaters connected through a bus
10BASE-T—A Physical layer standard for networks that specifies baseband transmission, twisted-pair
media, and 10-Mbps throughput 10BASE-T networks have a maximum segment length of 100 metersand rely on a star topology
10GBASE-ER—A Physical layer standard for achieving 10-Gbps data transmission over _single-mode,
fiber-optic cable In 10GBASE-ER the “ER” stands for “extended reach.” This standard specifies a startopology and segment lengths up to 40 kilometers
10GBASE-LR—A Physical layer standard for achieving 10-Gbps data transmission over _single-mode,
fiber-optic cable using wavelengths of 1310 nanometers In 10GBASE-LR, the “LR” stands for “longreach.” This standard specifies a star topology and segment lengths up to 10 kilometers
10GBASE-SR—A Physical layer standard for achieving 10-Gbps data transmission over multimode
fiber using wavelengths of 850 nanometers The maximum segment length for 10GBASE-SR can reach
up to 300 meters, depending on the fiber core diameter and modal bandwidth used
2.4-GHz band—The range of radiofrequencies from 2.4- to 2.4835-GHz The 2.4-GHz band is often
used for wireless network transmissions
3DES—See Triple DES.
3-tier architecture—A client/server environment that uses middleware to translate requests between the
client and server
5-4-3 rule—A guideline for 10-Mbps Ethernet networks stating that between two communicating
nodes, the network cannot contain more than five network segments connected by four repeating devices,and no more than three of the segments may be populated
802.11a—The IEEE standard for a wireless networking technique that uses multiple frequency bands in
the 5-GHz frequency range and provides a theoretical maximum throughput of 54 Mbps 802.11a’s highthroughput, compared with 802.11b, is attributable to its use of higher frequencies, its unique method ofencoding data, and more available bandwidth
802.11b—The IEEE standard for a wireless networking technique that uses DSSS (direct sequence
spread spectrum) signaling in the 2.4–2.4835-GHz frequency range (also called the 2.4-GHz band).802.11b separates the 2.4-GHz band into 14 overlapping 22-MHz channels and provides a theoreticalmaximum of 11-Mbps throughput 802.11b is also known as Wi-Fi
802.11g—The IEEE standard for a wireless networking technique designed to be compatible with
802.11b while using different encoding techniques that allow it to reach a theoretical maximum capacity
of 54 Mbps 802.11g, like 802.11b, uses the 2.4-GHz frequency band
802.11i—The IEEE standard for wireless network encryption and authentication that uses the EAP
authentication method, strong encryption, and dynamically assigned keys, which are different for everytransmission 802.11i specifies AES encryption and weaves a key into each packet
802.11—The IEEE standard for wireless networking.
802.15.1—The IEEE standard for wireless personal area network (WPAN) technology, including
Blue-tooth
Trang 8802.16a—An IEEE standard for wireless MANs that specifies the use of the frequency ranges between
2 and 11 GHz In IEEE 802.16a, antennas do not require a line-of-sight path between them and canexchange signals with multiple stations at once 802.16a is capable of achieving up to 70-Mbps through-put and its range is 50 kilometers (or approximately 30 miles)
802.16—An IEEE standard for wireless MANs that specifies the use of frequency ranges between 10
and 66 GHz and requires line-of-sight paths between antennas 802.16 antennas can cover 50 ters (or approximately 30 miles) and connections can achieve a maximum throughput of 70 Mbps
kilome-802.2—The IEEE standard for error and flow control in data frames.
802.3ab—The IEEE standard that describes 1000BASE-T, a 1-Gigabit Ethernet technology that runs
over four pairs of CAT 5 or better cable
802.3ae—The IEEE standard that describes 10-Gigabit Ethernet technologies, including
10GBASE-SR, 10GBASE-ER, and 10GBASE-LR
802.3af—The IEEE standard that specifies a way of supplying electrical power over Ethernet (PoE).
802.3af requires CAT 5 or better UTP or STP cabling and uses power sourcing equipment to supply rent over a wire pair to powered devices PoE is compatible with existing 10BASE-T, 100BASE-TX, and1000BASE-T implementations
cur-802.3—The IEEE standard for Ethernet networking devices and data handling.
802.3u—The IEEE standard that describes Fast Ethernet technologies, including 100BASE-TX,
100BASE-T4, and 100BASE-FX
802.3z—The IEEE standard that describes 1000Base (or 1-Gigabit) Ethernet technologies, including
1000BASE-LX, 1000BASE-SX, and 1000BASE-CX
802.5—The IEEE standard for Token Ring networking devices and data handling.
A+—The professional certification established by CompTIA that verifies knowledge about PC
opera-tion, repair, and management
access method—A network’s method of controlling how nodes access the communications channel.
CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is the access method specified inthe IEEE 802.3 (Ethernet) standard CSMA/CA (Carrier Sense Multiple Access with Collision Avoid-ance) is the access method specified by IEEE 802.11 (wireless LAN) standards
access point—See AP.
access server—See remote access server.
account—A record of a user that contains all of her properties, including rights to resources, password,
user name, and so on
ACK (acknowledgment)—A response generated at the Transport layer of the OSI Model that confirms
to a sender that its frame was received The ACK packet is the third of three in the three-step process ofestablishing a connection
acknowledgment—See ACK.
Active Directory—The Windows Server 2003 method for organizing and managing objects associated
with the network
Trang 9active monitor—On a Token Ring network, the workstation that maintains timing for token passing,
monitors token and frame transmission, detects lost tokens, and corrects problems when a timing error
or other disruption occurs Only one workstation on the ring can act as the active monitor at any giventime
active scanning—A method used by wireless stations to detect the presence of an access point In active
scanning, the station issues a probe to each channel in its frequency range and waits for the access point
to respond
active topology—A topology in which each workstation participates in transmitting data over the
net-work
ad hoc—A type of wireless LAN in which stations communicate directly with each other (rather than
using an access point)
address—A number that uniquely identifies each workstation and device on a network Without unique
addresses, computers on the network could not reliably communicate
address management—The process of centrally administering a finite number of network addresses for
an entire LAN Usually this task can be accomplished without touching the client workstations
Address Resolution Protocol—See ARP.
address resource record—A type of DNS data record that maps the IP address of an Internet-connected
device to its domain name
addressing—The scheme for assigning a unique identifying number to every workstation and device on
the network The type of addressing used on a network depends on its protocols and network operatingsystem
Administrator—A user account that has unlimited privileges to resources and objects managed by a
server or domain The Administrator account is created during NOS installation
Advanced Encryption Standard—See AES.
AES (Advanced Encryption Standard)—A private key encryption algorithm that weaves keys of 128,
160, 192, or 256 bits through data multiple times The algorithm used in the most popular form of AES
is known as Rijndael AES has replaced DES in situations such as military communications, whichrequire the highest level of security
AFP (AppleTalk Filing Protocol or Apple File Protocol)—The native file access protocol used by
Macintosh computers
agent—A software routine that collects data about a managed device’s operation and provides it to the
network management application running on the console
AH (authentication header)—In the context of IPSec, a type of encryption that provides authentication
of the IP packet’s data payload through public key techniques
AIX—A proprietary implementation of the UNIX system distributed by IBM.
alias—A nickname for a node’s host name Aliases can be specified in a local host file.
AM (amplitude modulation)—A modulation technique in which the amplitude of the carrier signal is
modified by the application of a data signal
American National Standards Institute—See ANSI.
Trang 10amplifier—A device that boosts, or strengthens, an analog signal.
amplitude—A measure of a signal’s strength.
amplitude modulation—See AM.
analog—A signal that uses variable voltage to create continuous waves, resulting in an inexact
transmis-sion
ANDing—A logical process of combining bits In ANDing, a bit with a value of 1 plus another bit with
a value of 1 results in a 1 A bit with a value of 0 plus any other bit results in a 0
ANSI (American National Standards Institute)—An organization composed of more than 1000
rep-resentatives from industry and government who together determine standards for the electronics try in addition to other fields, such as chemical and nuclear engineering, health and safety, andconstruction
indus-anycast address—A type of address specified in IPv6 that represents a group of interfaces, any one of
which (and usually the first available of which) can accept a transmission At this time, anycast addressesare not designed to be assigned to hosts, such as servers or workstations, but rather to routers
AP (access point)—A device used on wireless LANs that transmits and receives wireless signals to and
from multiple nodes and retransmits them to the rest of the network segment Access points can connect
a group of nodes with a network or two networks with each other They may use directional or directional antennas
omni-API (application program interface)—A set of routines that make up part of a software _application.
Apple File Protocol—See AFP.
AppleShare IP—A proprietary network operating system from Apple Computer that offers file, print,
Web, DNS, and mail services AppleShare IP was the predecessor to Mac OS X Server
AppleTalk—The protocol suite used to interconnect Macintosh computers Although AppleTalk was
originally designed to support peer-to-peer networking among Macintoshes, it can now be routedbetween network segments and integrated with NetWare- or Microsoft-based networks
AppleTalk Filing Protocol—See AFP.
AppleTalk network number—A unique 16-bit number that identifies the network to which an
AppleTalk node is connected
AppleTalk node ID—A unique 8-bit or 16-bit number that identifies a computer on an AppleTalk
net-work
AppleTalk zone—A logically defined group of computers on an AppleTalk network.
application gateway—See proxy server.
Application layer—The seventh layer of the OSI Model Application layer protocols enable software
programs to negotiate formatting, procedural, security, synchronization, and other requirements with thenetwork
Application layer gateway—See proxy server.
application program interface—See API.
application switch—Another term for a Layer 3 or Layer 4 switch.
Trang 11archive bit—A file attribute that can be checked (or set to “on”) or unchecked (or set to “off ”) to
indi-cate whether the file needs to be archived An operating system checks a file’s archive bit when it is ated or changed
cre-ARP (Address Resolution Protocol)—A core protocol in the TCP/IP suite that belongs in the Network
layer of the OSI Model ARP obtains the MAC (physical) address of a host, or node, and then creates alocal database that maps the MAC address to the host’s IP (logical) address
ARP cache—See ARP table.
ARP table—A database of records that map MAC addresses to IP addresses The ARP table is stored
on a computer’s hard disk where it is used by the ARP utility to supply the MAC addresses of networknodes, given their IP addresses
array—A group of hard disks.
AS (authentication service)—In Kerberos terminology, the process that runs on a KDC (key
distribu-tion center) to initially validate a client who’s logging on The authenticadistribu-tion service issues session keys
to the client and the service the client wants to access
asset management—The process of collecting and storing data on the number and types of software and
hardware assets in an organization’s network The data collection is automated by electronically ing each network client from a server
examin-association—In the context of wireless networking, the communication that occurs between a station
and an access point to enable the station to connect to the network via that access point
asymmetric encryption—A type of encryption (such as public key encryption) that uses a different key
for encoding data than is used for decoding the ciphertext
asymmetric multiprocessing—A multiprocessing method that assigns each subtask to a specific
proces-sor
asymmetrical—The characteristic of a transmission technology that affords greater bandwidth in one
direction (either from the customer to the carrier, or vice versa) than in the other direction
asymmetrical DSL—A variation of DSL that offers more throughput when data travels downstream,
downloading from a local carrier’s switching facility to the customer, than when it travels upstream,uploading from the customer to the local carrier’s switching facility
asynchronous—A transmission method in which data being transmitted and received by nodes does not
have to conform to any timing scheme In asynchronous communications, a node can transmit at anytime and the destination node must accept the transmission as it comes
Asynchronous Transfer Mode—See ATM.
ATM (Asynchronous Transfer Mode)—A Data Link layer technology originally conceived in 1983 at
Bell Labs, and standardized by the ITU in the mid-1990s It relies on fixed packets, called cells, that eachconsist of 48 bytes of data plus a 5-byte header ATM relies on virtual circuits and establishes a connec-tion before sending data Having a reliable connection therefore allows network managers to specify QoSlevels for certain types of traffic
attenuation—The extent to which a signal has weakened after traveling a given distance.
Trang 12attribute—A variable property associated with a network object For example, a restriction on the time
of day a user can log on is an attribute associated with that user object
authentication—The process of comparing and matching a client’s credentials with the credentials in
the NOS user database to enable the client to log on to the network
authentication header—See AH.
authentication protocol—A set of rules that governs how servers authenticate clients Several types of
authentication protocols exist
authentication service—See AS.
authenticator—In Kerberos authentication, the user’s time stamp encrypted with the session key The
authenticator is used to help the service verify that a user’s ticket is valid
availability—How consistently and reliably a file, device, or connection can be accessed by authorized
personnel
B channel—In ISDN, the “bearer” channel, so named because it bears traffic from point to point.
backbone—The part of a network to which segments and significant shared devices (such as routers,
switches, and servers) connect A backbone is sometimes referred to as “a network of networks,” because
of its role in interconnecting smaller parts of a LAN or WAN
backleveling—The process of reverting to a previous version of a software application after attempting
to upgrade it
back up—The process of copying critical data files to a secure storage area Often, backups are performed
according to a formulaic schedule
backup—A copy of data or program files created for archiving or safekeeping.
backup rotation scheme—A plan for when and how often backups occur, and which backups are full,
incremental, or differential
bandwidth—A measure of the difference between the highest and lowest frequencies that a medium can
transmit
base I/O port—A setting that specifies, in hexadecimal notation, which area of memory will act as a
channel for data traveling between the NIC and the CPU Like its IRQ, a device’s base I/O port cannot
be used by any other device
base schema—The standard set of object classes and attributes installed as the default schema for
Net-Ware’s eDirectory The base schema can be extended through NetWare utilities
baseband—A form of transmission in which digital signals are sent through direct current pulses applied
to a wire This direct current requires exclusive use of the wire’s capacity, so baseband systems can mit only one signal, or one channel, at a time Every device on a baseband system shares a single chan-nel
trans-baseline—A record of how a network operates under normal conditions (including its performance,
col-lision rate, utilization rate, and so on) Baselines are used for comparison when conditions change
basic input/output system—See BIOS.
Trang 13Basic Rate Interface—See BRI.
beacon frame—In the context of wireless networking, a frame issued by an access point to alert other
nodes of its existence
bend radius—The radius of the maximum arc into which you can loop a cable before you will cause data
transmission errors Generally, a twisted-pair cable’s bend radius is equal to or greater than four times thediameter of the cable
Berkeley Software Distribution—See BSD.
best path—The most efficient route from one node on a network to another Under optimal network
conditions, the best path is the most direct path between two points However, when traffic congestion,segment failures, and other factors create obstacles, the most direct path may not be the best path
BGP (Border Gateway Protocol)—A complex routing protocol used on border and exterior routers.
BGP is the routing protocol used on Internet backbones
binary—A system founded on using 1s and 0s to encode information.
binding—The process of assigning one network component to work with another.
bio-recognition access—A method of authentication in which a device scans an individual’s unique
physical characteristics (such as the color patterns in his iris or the geometry of his hand) to verify theuser’s identity
BIOS (basic input/output system)—The firmware attached to a computer’s motherboard that controls
the computer’s communication with its devices, among other things
bit (binary digit)—A bit equals a single pulse in the digital encoding system It may have only one of
two values: 0 or 1
blackout—A complete power loss.
Block ID—The first set of six characters that make up the MAC address and that are unique to a
par-ticular manufacturer
Bluetooth—A wireless networking standard that uses FHSS (frequency hopping spread spectrum)
sig-naling in the 2.4-GHz band to achieve a maximum throughput of either 723 Kbps or 2.1 Mbps, ing on the version Bluetooth was designed for use primarily with small office or home networks in whichmultiple devices (including cordless phones, computers, and pagers) are connected
depend-Bluetooth Special Interest Group (SIG)—A consortium of companies, including Sony Ericsson, Intel,
Nokia, Toshiba, and IBM, that formally banded together in 1998 to refine and standardize Bluetoothtechnology
bonding—The process of combining more than one bearer channel of an ISDN line to increase
through-put For example, BRI’s two 64-Kbps B channels are bonded to create an effective throughput of 128Kbps
boot partition—A partition on a computer’s hard disk from which the operating system software is
launched
boot sector virus—A virus that resides on the boot sector of a floppy disk and is transferred to the
par-tition sector or the DOS boot sector on a hard disk A boot sector virus can move from a floppy to a harddisk only if the floppy disk is left in the drive when the machine starts
Trang 14BOOTP (Bootstrap Protocol)—An Application layer protocol in the TCP/IP suite that uses a central
list of IP addresses and their associated devices’ MAC addresses to assign IP addresses to clients ically BOOTP was the precursor to DHCP
dynam-Bootstrap Protocol—See BOOTP.
Border Gateway Protocol—See BGP.
border router—A router that connects an autonomous LAN with an exterior network—for example, the
router that connects a business to its ISP
BorderManager—An application from Novell that provides proxy and firewall services on NetWare
servers
bot—A program that runs automatically Bots can spread viruses or other malicious code between users
in a chat room by exploiting the IRC protocol
braiding—A braided metal shielding used to insulate some types of coaxial cable.
branch—A part of the organizational structure of an operating system’s directory that contains objects
or other organizational units
BRI (Basic Rate Interface)—A variety of ISDN that uses two 64-Kbps bearer channels and one
16-Kbps data channel, as summarized by the notation 2B+D BRI is the most common form of ISDNemployed by home users
bridge—A connectivity device that operates at the Data Link layer (Layer 2) of the OSI Model and reads
header information to forward packets according to their MAC addresses Bridges use a filtering base to determine which packets to discard and which to forward Bridges contain one input and oneoutput port and separate network segments
data-bridge router (brouter)—A router capable of providing Layer 2 bridging functions.
broadband—A form of transmission in which signals are modulated as radiofrequency analog pulses
with different frequency ranges Unlike baseband, broadband technology does not involve binary ing The use of multiple frequencies enables a broadband system to operate over several channels andtherefore carry much more data than a baseband system
encod-broadband cable—A method of connecting to the Internet over a cable network In encod-broadband cable,
computers are connected to a cable modem that modulates and demodulates signals to and from the cablecompany’s head-end
broadcast—A transmission that involves one transmitter and multiple receivers.
broadcast domain—A combination of ports on a switch (or multiple switches) that make up a Layer 2
segment To be able to exchange data with each other, broadcast domains must be connected by a Layer
3 device, such as a router or Layer 3 switch A VLAN is one type of broadcast domain
brouter—See bridge router.
brownout—A momentary decrease in voltage, also known as a sag An overtaxed electrical system may
cause brownouts, recognizable as a dimming of the lights
brute force attack—An attempt to discover an encryption key or password by trying numerous possible
character combinations Usually, a brute force attack is performed rapidly by a program designed for thatpurpose
Trang 15BSD (Berkeley Software Distribution)—A UNIX distribution that originated at the University of
Cal-ifornia at Berkeley The BSD suffix differentiates these distributions from AT&T distributions Nolonger being developed at Berkeley, the last public release of BSD UNIX was version 4.4
bug—A flaw in software or hardware that causes it to malfunction.
bus topology—A topology in which a single cable connects all nodes on a network without intervening
connectivity devices
bus topology WAN—A WAN in which each location is connected to no more than two other locations
in a serial fashion
bus—The single cable connecting all devices in a bus topology.
bus—The type of circuit used by a computer’s motherboard to transmit data to components Most new
Pentium computers use buses capable of exchanging 32 or 64 bits of data As the number of bits of data
a bus handles increases, so too does the speed of the device attached to the bus
byte—Eight bits of information In a digital signaling system, broadly speaking, one byte carries one
piece of information
cable checker—See continuity tester.
cable drop—A fiber-optic or coaxial cable that connects a neighborhood cable node to a customer’s
house
cable modem—A device that modulates and demodulates signals for transmission and reception via
cable wiring
cable modem access—See broadband cable.
cable performance tester—A troubleshooting tool that tests cables for continuity, but can also measure
crosstalk, attenuation, and impedance; identify the location of faults; and store or print cable testingresults
cable plant—The hardware that constitutes the enterprise-wide cabling system.
cable tester—A device that tests cables for one or more of the following conditions: continuity, segment
length, distance to a fault, attenuation along a cable, near-end crosstalk, and termination resistance andimpedance Cable testers may also issue pass/fail ratings for wiring standards or store and print cable test-ing results
call tracking system—A software program used to document technical problems and how they were
resolved (also known as help desk software)
capacity—See throughput.
CardBus—A PCMCIA standard that specifies a 32-bit interface running at 33 MHz, similar to the PCI
expansion board standard Most modern laptops are equipped with CardBus slots for connecting nal modems and NICs, among other things
exter-Carrier Sense Multiple Access with Collision Avoidance—See CSMA/CA.
Carrier Sense Multiple Access with Collision Detection—See CSMA/CD.