Learning Center
Plans & pricing Sign in
Sign Out


VIEWS: 245 PAGES: 47

									 1                                                        Glossary

 2   .NET: Microsoft’s approach to the Web services.
 3   10/100 Ethernet: A collective name for the Ethernet physical layer
 4       100Base-TX and 100Base-FX standards.
 5   1000Base-LX: A fiber version of gigabit Ethernet for long wavelengths
 6       (transmitting at 1,300 nm).
 7   1000Base-SX: A fiber version of gigabit Ethernet for short wavelengths
 8       (transmitting at 850 nm).
 9   1000Base-T: A UTP version of gigabit Ethernet.
10   1000Base-x: The Ethernet physical layer technology of gigabit Ethernet,
11       used today mainly to connect switches to switches or switches to
12       routers; increasingly being used to connect servers and some desktop
13       PCs to the switches that serve them.
14   100Base-FX: The Ethernet physical layer 100 Mbps standard used
15       primarily to connect switches to other switches, now being phased
16       out.
17   100Base-TX: The dominant Ethernet physical layer 100 Mbps standard
18       brought to desktop computers today.
19   10Base-F: See 802.3 10Base-F.
20   10Base-T: See 802.3 10Base-T.
21   1G: See First-Generation.
22   2.5G: See Second-and-a-Half Generation.
23   232 Serial Port: The port on a PC that uses two voltage ranges to transmit
24       information.
25   25-Pair UTP Cord: The cabling used by telephony for vertical wiring
26       runs within a building.
27   2G: See Second-Generation.
28   2-Pair Data-Grade: The higher-quality UTP access lines used by
29       telephone carriers for private lines. Two pairs run out to each
30       customer.
31   3DES: See Triple DES.
32   3G: See Third-Generation.
33   4-Pair Unshielded Twisted Pair (UTP): The type of wiring typically
34       used in Ethernet networks. 4-pair UTP contains eight copper wires
35       organized as four pairs. Each wire is covered with dielectric
36       insulation, and an outer jacket encloses and protects the four pairs.
37   50-Pin Octopus Connector: The type of connector in which vertical
38       cords typically terminate.
39   802 Committee: See 802 LAN/MAN Standards Committee.
40   802 LAN/MAN Standards Committee: The IEEE committee responsible

                                                                     Chapter 1-1
 1       for Ethernet standards.
 2   802.11 Working Group: The IEEE working group that creates wireless
 3       LAN standards.
 4   802.11e: A standard for quality of service in 802.11 WLANS.
 5   802.11i: An advanced form of 802.11 wireless LAN security.
 6   802.16: WiMAX.
 7   802.1D Spanning Tree Protocol: The protocol that addresses both single
 8       points of failure and loops.
 9   802.1p: The standard that permits up to eight priority levels.
10   802.1Q: The standard that extended the Ethernet MAC layer frame to
11       include two optional tag fields.
12   802.3 10Base-F: An Ethernet physical layer 10 Mbps fiber standard, now
13       almost entirely extinct.
14   802.3 10Base-T: The slowest Ethernet physical layer technology in use
15       today; uses 4-pair UTP wiring and operates at 10 Mbps.
16   802.3 MAC Layer Frame: See Ethernet Frame.
17   802.3 MAC Layer Standard: The standard that defines Ethernet frame
18       organization and NIC and switch operation.
19   802.3 Working Group: The 802 Committee’s working group that creates
20       Ethernet-specific standards.
21   900 Number: A number that allows customers to call into a company;
22       callers pay a fee that is much higher than that of a regular toll call.
23   Access Control List (ACL): An ordered list of pass/deny rules for a
24       firewall or other device.
25   Access Line: 1) In networks, a transmission line that connects a station to
26       a switch. 2) In telephony, the line used by the customer to reach the
27       PSTN’s central transport core.
28   Access Line: The line used by the customer to reach the PSTN’s central
29       transport core.
30   Access Point: A bridge between a wireless station and a wired LAN.
31   Access System: In telephony, the system by which customers access the
32       PSTN, including access lines and termination equipment in the end
33       office at the edge of the transport core.
34   Account: An identifiable entity that may own resources on a computer.
35   ACE: See OPNET Application Characterization Environment.
36   ACK Bit: The bit in a TCP segment that is set to indicate if the segment
37       contains an acknowledgement.
38   ACK: See Acknowledgement.
39   Acknowledgement (ACK): 1) An acknowledgement message, sent by the
40       receiver when a message is received correctly. 2) An
41       acknowledgement frame, sent by the receiver whenever a frame is
42       received; used in CSMA/CA+ACK in 802.11.
43   Acknowledgement Number Field: In TCP, a header field that tells what
44       TCP segment is being acknowledged in a segment.
45   ACL: See Access Control List.
46   ADC: See Analog-to-Digital Conversion.

                                                                      Chapter 1-2
 1   Address Resolution Protocol (ARP): Protocol for address resolution
 2       used in Ethernet networks. If a host or router knows a target host’s or
 3       router’s IP address, ARP finds the target’s data link layer address.
 4   Administrative IP Server: A server needed to support IP.
 5   Administrator: A super account on a Windows server that automatically
 6       has full permissions in every directory on the server.
 7   ADSL: See Asymmetric Digital Subscriber Line.
 8   Advanced Encryption Standard (AES): New symmetric encryption
 9       standard that offers 128-bit, 192-bit or 256-bit encryption efficiently.
10   AES: See Advanced Encryption Standard.
11   Agent: See Network Management Agent.
12   Aggregate Throughput: Throughput shared by multiple users; individual
13       users will get a fraction of this throughput.
14   Alternative Route: In mesh topology, one of several possible routes from
15       one end of the network to the other, made possible by the topology’s
16       many connections among switches or routers.
17   Always On: Being always available for service; used to describe access
18       lines.
19   Amplitude Modulation: A simple form of modulation in which a modem
20       transmits one of two analog signals—a high-amplitude (loud) signal
21       or a low-amplitude (soft) signal.
22   Amplitude: The maximum (or minimum) intensity of a wave. In sound,
23       this corresponds to volume (loudness).
24   Analog Signal: A signal that rises and falls in intensity smoothly and that
25       does not have a limited numbers of states.
26   Analog-to-Digital Conversion (ADC): A device for the conversion of
27       transmissions from the analog local loop to signals on the digital
28       telephone network’s core.
29   Antivirus Software: Software that scans computers to protect them
30       against viruses, worms, and Trojan horses arriving in e-mail
31       attachments and other propagation methods.
32   API: See Application Program Interface.
33   AppleTalk: Apple’s proprietary architecture for use on Macintosh
34       computers.
35   Applicant: In authentication, the user trying to prove his or her identity;
36       sometimes called the supplicant.
37   Application Architecture: The arrangement of how application layer
38       functions are spread among computers to deliver service to users.
39   Application Characterization Environment: See OPNET Application
40       Characterization Environment.
41   Application Firewall: A firewall that examines the application layer
42       content of packets.
43   Application Layer: The standards layer that governs how two
44       applications communicate with each other; Layer 7 in OSI, Layer 5 in
45       TCP/IP.
46   Application Profile: A method, offered by Bluetooth, that allows devices

                                                                       Chapter 1-3
 1       to work with one another automatically at the application layer.
 2   Application Program Interface (API): A specification that allows
 3       application server programs to interact directly with database systems.
 4   Application Program: Program that does work for users; operating
 5       system is the other major type of program found on computers.
 6   Application Server: A server used by large e-commerce sites that accepts
 7       user data from a front-end webserver, assembles information from
 8       other servers, and creates a webpage to send back to the user.
 9   Architecture: A broad plan that specifies what is needed in general and
10       the components that will be used to provide that functionality.
11       Applied to standards, networks, and applications.
12   Asymmetric Digital Subscriber Line (ADSL): The type of DSL
13       designed to go into residential homes, offers high downstream speeds
14       but limited upstream speeds.
15   Asynchronous Transfer Mode (ATM): The packet-switched network
16       technology, specifically designed to carry voice, used for transmission
17       in the PSTN transport core. ATM offers quality of service guarantees
18       for throughput, latency, and jitter.
19   ATM: Asynchronous Transfer Mode.
20   Attenuate: For a signal’s strength to weaken during propagation.
21   Authentication Server: A server that stores data to help the verifier check
22       the credentials of the applicant.
23   Authentication: The requirement that someone who requests to use a
24       resource must prove his or her identity.
25   Autonomous System: Internet owned by an organization.
26   Autosensing: The ability of a switch to detect the standard being used at
27       the other end of the connection, and adjust its own speed to match.
28   Availability: The ability of a network to serve its users.
29   Backdoor: A way back into a compromised computer that an attacker
30       leaves open; it may simply be a new account or a special program.
31   Back-Office: Transaction processing applications for a business’s internal
32       needs.
33   Bandpass Filter: A device that filters out all signals below 300 Hz and
34       above about 3.4 kHz.
35   Bandwidth: The range of frequencies over which a signal is spread.
36   Bank Settlement Firm: An e-commerce service that handles credit card
37       payments.
38   Base Price: The price of a system’s hardware, software, or both before
39       necessary options are added.
40   Baseband Signal: 1) The original signal in a radio transmission; 2) a
41       signal that is injected directly into a wire for propagation.
42   Baseband: Transmission in which the signal is simply injected into a wire.
43   Baud Rate: The number of clock cycles a transmission system uses per
44       second.
45   Best-Match Row: The row that provides the best forwarding option for a
46       particular incoming packet.

                                                                      Chapter 1-4
 1   BGP: See Border Gateway Protocol.
 2   Binary Data: Data that has only two possible values (ones and zeros).
 3   Binary Numbers: The Base 2 counting system where ones and zeros used
 4        in combination can represent whole numbers (integers).
 5   Binary Signaling: Signaling that uses only two states.
 6   Biometrics: The use of bodily measurements to identify an applicant.
 7   Bit Rate: In digital data transmission, the rate at which information is
 8        transmitted; measured in bits per second.
 9   Bits per Second (bps): The measure of network transmission speed. In
10        increasing factors of 1,000 are kilobits per second (kbps), megabits
11        per second (Mbps), gigabits per second (Gbps), and terabits per
12        second (Tbps).
13   Black List: A list of banned websites.
14   Blended Threat: An attack that propagates both as a virus and as a worm.
15   Bluetooth: A wireless networking standard created for personal area
16        networks.
17   Bonding: See Link Aggregation.
18   Border Firewall: A firewall that sits at the border between a firm and the
19        outside world.
20   Border Gateway Protocol (BGP): The most common exterior routing
21        protocol on the Internet. Recall that gateway is an old term for router.
22   Border Router: A router that sits at the edge of a site to connect the site
23        to the outside world through leased lines, PSDNs, and VPNs.
24   Bps (bps): See Bits per Second.
25   Bridge: An access point that connects two different types of LANs.
26   Broadband Wireless Access (BWA): High-speed local wireless
27        transmission systems.
28   Broadband: 1) Transmission where signals are sent in wide radio
29        channels; 2) any high-speed transmission system.
30   Broadcast Address: In Ethernet, FF-FF-FF-FF-FF-FF (48 ones); tells
31        switches that the frame should be broadcast.
32   Broadcast: To send a message out to all other stations simultaneously.
33   Brute-Force Attack: A password-cracking attack in which an attacker
34        tries to break a password by trying all possible combinations of
35        characters.
36   Bursty: Having short, high-speed bursts separated by long silences.
37        Characteristic of data transmission.
38   Bus Topology: A topology in which one station transmits and has its
39        signals broadcast to all stations.
40   Business Case: An argument for a system in business terms.
41   Business Continuity Recovery: The reestablishment of a company’s
42        ability to continue operations.
43   Business Continuity: A company’s ability to continue operations.
44   BWA: See Broadband Wireless Access.
45   CA: 1) See Certificate Authority. 2) See Collision Avoidance.
46   Cable Modem: 1) Broadband data transmission service using cable

                                                                        Chapter 1-5
 1       television; 2) the modem used in this service.
 2   Cable Replacement: Getting rid of cables between devices by
 3       implementing wireless networking.
 4   Call Waiting: A service that allows the user to place an original caller on
 5       hold if someone else calls the user, shift briefly to the new caller, and
 6       then switch back to the original caller.
 7   Caller ID: Service wherein the telephone number of the party calling you
 8       is displayed on your phone’s small display screen before you pick up
 9       the handset; allows the user to screen calls.
10   Carrier Sense Multiple Access with Collision Avoidance and
11       Acknowledgements (CSMA/CA+ACK): A mandatory mechanism
12       used to reduce problems with multiple simultaneous transmissions,
13       which occur in wireless transmission. CSMA/CA+ACK is a media
14       access control discipline, and it uses both collision avoidance and
15       acknowledgement frames.
16   Carrier Sense Multiple Access with Collision Detection (CSMA/CD):
17       The process wherein if a station wants to transmit, it may do so if no
18       station is already transmitting but must wait if another station is
19       already sending. In addition, if there is a collision because two
20       stations send at the same time, all stations stop, wait a random period
21       of time, and then try again.
22   Carrier: A transmission service company.
23   Cat 5e: See Category 5e.
24   Category (Cat) 5e: Quality type of UTP wiring; required for 100Base-TX
25       and gigabit Ethernet.
26   Category 6: The newest quality type of UTP wiring being sold; not
27       required for even gigabit Ethernet.
28   CDMA IS-95: The form of CDMA used in 2G cellular technology in the
29       United States.
30   CDMA: See Code Division Multiple Access.
31   CDMA2000 1x: The initial 3G step for implementing CDMA2000,
32       offering telephone modem speeds.
33   CDMA2000 1xEV-DO: The second 3G step for implementing
34       CDMA2000, which will offer speeds similar to those in DSL and
35       cable modems.
36   CDMA2000: A new 3G technology, developed by Qualcomm, offering a
37       staged approach to increasing speed.
38   Cell: 1) In ATM, a fixed-length frame. 2) In cellular telephony, a small
39       geographical area served by a cellsite.
40   Cellphone: A cellular telephone, also called a mobile phone or mobile.
41   Cellsite: In cellular telephony, equipment at a site near the middle of each
42       cell, containing a transceiver and supervising each cellphone’s
43       operation.
44   Cell-Switching: A technology that uses fixed-length frames.
45   Certificate Authority (CA): Organization that provides public key–
46       private key pairs and digital certificates.

                                                                        Chapter 1-6
 1   Certificate Revocation List (CRL): A certificate authority’s list of digital
 2       certificates it has revoked before their expiration date.
 3   Challenge Message: In challenge–response authentication protocols, the
 4       message initially sent from the verifier to the applicant.
 5   Challenge–Response Authentication Protocol (CHAP): A specific
 6       challenge–response authentication protocol.
 7   Challenge–Response Authentication: Initial authentication method in
 8       which the verifier sends the applicant a challenge message, and the
 9       applicant does a calculation to produce a response, which it sends
10       back to the verifier.
11   Channel Bandwidth: The range of frequencies in a channel; determined
12       by subtracting the lowest frequency from the highest frequency.
13   Channel Reuse: The ability to use each channel multiple times, in
14       different cells in the network.
15   Channel Service Unit (CSU): The part of a CSU/DSU device designed to
16       protect the telephone network from improper voltages sent into a
17       private line.
18   Channel: A small frequency range that is a subdivision of a service band.
19   CHAP: See Challenge–Response Authentication Protocol.
20   Checkout: A core e-commerce function that allows a buyer who has
21       finished shopping to pay for the selected goods.
22   Chronic Lack of Capacity: A state in which the network lacks adequate
23       capacity much of the time.
24   CIDR: See Classless InterDomain Routing.
25   Ciphertext: The result of encrypting a plaintext message. Ciphertext can
26       be transmitted with confidentiality.
27   CIR: See Committed Information Rate.
28   Circuit Switching: Switching in which capacity for a voice conversation
29       is reserved on every switch and trunk line end-to-end between the two
30       subscribers.
31   Circuit: A two-way connection with reserved capacity.
32   Cladding: A thick glass cylinder that surrounds the core in optical fiber.
33   Class A IP Address: In classful addressing, an IP address block with
34       more than sixteen million IP addresses; given only to the largest firms
35       and ISPs.
36   Class B IP Address: In classful addressing, an IP address block with
37       about 65,000 IP addresses; given to large firms.
38   Class C IP Address: In classful addressing, an IP address block with 254
39       possible IP addresses; given to small firms.
40   Class D IP Address: In classful addressing, IP addresses used in
41       multicasting.
42   Class 5 Switch: See End Office Switch.
43   Classful Addressing: Giving a firm one of four block sizes for IP
44       addresses: a very large Class A address block, a medium-sized Class
45       B address block, or a small Class C address block.
46   Classless InterDomain Routing (CIDR): System for allocating IP

                                                                       Chapter 1-7
 1       addresses that does not use IP address classes.
 2   Clear to Send (CTS): In 802.11, a message broadcast by an access point,
 3       which allows only a station that has sent a Request to Send message
 4       to transmit. All other stations must wait.
 5   CLEC: See Competitive Local Exchange Carrier.
 6   CLI: See Command Line Interface.
 7   Client Station: A station that receives service from a server station.
 8   Client/Server Interaction: Interaction in which a client program requests
 9       service from a server and in which the server program provides the
10       service.
11   Client/Server Processing: The form of client/server computing in which
12       the work is done by programs on two machines.
13   Client/Server System: A system where some processing power is on the
14       client computer. The two types of client/server systems are file server
15       program access and full client/server processing.
16   Clock Cycle: A period of time during which a transmission line’s state is
17       held constant.
18   Cloud: The symbol traditionally used to represent the PSDN transport
19       core, reflecting the fact that although the PSDN has internal switches
20       and trunk lines, the customer does not have to know how things work
21       inside the cloud.
22   Coating: In optical fiber, the substance that surrounds the cladding to keep
23       out light and to strengthen the fiber. Coating includes strands of
24       yellow Aramid (Kevlar) yarn to strengthen the fiber.
25   Coaxial Cable: The IEEE working group that creates wireless LAN
26       standards.
27   Code Division Multiple Access (CDMA): A new form of cellular
28       technology and a form of spread spectrum transmission that allows
29       multiple stations to transmit at the same time in the same channel;
30       also permits stations in adjacent cells to use the same channel without
31       serious interference.
32   Codec: The device in the end office switch that converts between the
33       analog local loop voice signals and the digital signals of the end office
34       switch.
35   Collision Avoidance (CA): In 802.11, used with CSMA to listen for
36       transmissions, so if a wireless NIC detects a transmission, it must not
37       transmit. This avoids collision.
38   Collision Domain: In Ethernet CSMA/CD systems that use hubs or bus
39       topologies, the collection of all stations that can hear one another;
40       only one can transmit at a time.
41   Collision: When two simultaneous signals use the same shared
42       transmission medium, the signals will add together and become
43       scrambled (unintelligible).
44   Command Line Interface (CLI): An interface used to work with
45       switches and routers, in which the user types highly structured
46       commands, ending each command with Enter.

                                                                       Chapter 1-8
 1   Command–Response Cycle: The exchange of messages through which
 2      SNMP communication between the manager and agents takes place.
 3      In it, the manager sends a command, and the agent sends back a
 4      response confirming that the command has been met, delivering
 5      requested data, or saying that an error has occurred and that the agent
 6      cannot comply with the command.
 7   Committed Information Rate (CIR): PVC speed that is guaranteed by
 8      the Frame Relay carrier.
 9   Community Name: In SNMP Version 1, only devices using the same
10      community name will communicate with each other; very weak
11      security.
12   Competitive Local Exchange Carrier (CLEC): A competitor to the
13      ILEC.
14   Comprehensive Security: Security in which all avenues of attack are
15      closed off.
16   Compromise: A successful attack.
17   Computer Security Incident Response Team (CSIRT): A team
18      convened to handle major security incidents, made up of the firm’s
19      security staff, members of the IT staff, and members of functional
20      departments, including the firm’s legal department.
21   Confidentiality: Assurance that interceptors cannot read transmissions.
22   Connectionless: Type of conversation that does not use explicit openings
23      and closings.
24   Connection-Oriented: Type of conversation in which there is a formal
25      opening of the interactions, a formal closing, and maintenance of the
26      conversation in between.
27   Connectorize: To add connectors to something.
28   Constellation: In quadrature amplitude modulation, the collection of all
29      possible amplitude/phase combinations.
30   Continuity Testers: UTP tester that ensures that wires are inserted into
31      RJ-45 connectors in the correct order and are making good contact.
32   Convergence: The correction of routing tables after a change in an
33      internet.
34   Conversion: The process of browsers becoming buyers.
35   Cord: A length of transmission medium—usually UTP or optical fiber but
36      sometimes coaxial cable.
37   Core Switch: A switch further up the hierarchy that carries traffic
38      between pairs of switches. May also connect switches to routers.
39   Core: 1) In optical fiber, the very thin tube into which a transmitter injects
40      light. 2) In a switched network, the collection of all core switches.
41   Crack: To guess a password.
42   Credentials: Proof of identity that an applicant can present during
43      authentication.
44   Credit Card Verification Service: An e-commerce service that checks
45      the validity of the credit card number a user has typed.
46   Criminal Attacker: An attacker who attacks with criminal motivation.

                                                                        Chapter 1-9
 1   Crimping Tool: Tool for crimping wires into an RJ-45 connector.
 2   CRL: See Certificate Revocation List.
 3   CRM: See Customer Relationship Management.
 4   Cross-Connect Device: The device within a wiring closet that vertical
 5       cords plug into. Cross-connect devices connect the wires from the
 6       riser space to 4-pair UTP cords that span out to the wall jacks on each
 7       floor.
 8   Crossover Cable: A UTP cord that allows a NIC in one computer to be
 9       connected directly to the NIC in another computer; switches Pins 1
10       and 2 with Pins 3 and 6.
11   Crosstalk Interference: Mutual EMI among wire pairs in a UTP cord.
12   Cryptographic System: A security system that automatically provides a
13       mix of security protections, usually including confidentiality,
14       authentication, message integrity, and replay protection.
15   CSIRT: See Computer Security Incident Response Team.
16   CSMA/CA+ACK: See Carrier Sense Multiple Access with Collision
17       Avoidance and Acknowledgments. See definitions of the individual
18       components.
19   CSMA/CD: See Carrier Sense Multiple Access with Collision Detection.
20   CSU/DSU: Device that connects an internal site system to a private line
21       circuit.
22   CSU: See Channel Service Unit.
23   CTS: See Clear to Send.
24   Customer Premises Equipment (CPE): Equipment owned by the
25       customer, including PBXs, internal vertical and horizontal wiring, and
26       telephone handsets.
27   Customer Relationship Management (CRM): Software that examines
28       customer data to understand the preference of a company’s customers.
29   Cut-through: Switching wherein the Ethernet switch examines only some
30       fields in a frame’s header before sending the bits of the frame back
31       out.
32   Cyberterror: A computer attack made by terrorists.
33   Cyberwar: A computer attack made by a national government.
34   DAC: See Digital-to-Analog Conversion.
35   Data Encryption Standard (DES): Popular symmetric key encryption
36       method; with only 56-bit keys, considered to be too weak for
37       business-to-business encryption.
38   Data Field: The content delivered in a message.
39   Data Link Control Identifier (DLCI): The virtual circuit number in
40       Frame Relay, normally 10 bits long.
41   Data Link Layer: The layer that governs transmission within a single
42       network all the way from the source station to the destination station
43       across zero or more switches; Layer 2 in OSI.
44   Data Link: The path that a frame takes across a single network (LAN or
45       WAN).
46   Data Service Unit (DSU): The part of a CSU/DSU circuit that formats the

                                                                     Chapter 1-10
 1       data in the way the private line requires.
 2   dB: See Decibel.
 3   Dead Spot: See Shadow Zone.
 4   Decapsulation: The removing of a message from the data field of another
 5       message.
 6   Decibel (dB): The unit in which attenuation is measured.
 7   Decrypt: Conversion of encrypted ciphertext into the original plaintext so
 8       an authorized receiver can read an encrypted message.
 9   Dedicated Server: A server that is not used simultaneously as a user PC.
10   Default Printer: The printer to which a user’s print jobs will be sent
11       unless the user specifies a different printer.
12   Default Router: The next-hop router that a router will forward a packet to
13       if the routing table does not have a row that governs the packet’s IP
14       address except for the default row.
15   Default Row: The row of a routing table that will be selected
16       automatically if no other row matches; its value is
17   Defense in Depth: The use of successive lines of defense.
18   Demilitarized Zone (DMZ): A subnet in which webservers and other
19       public servers are placed.
20   Demodulate: To convert digital transmission signals to analog signals.
21   Denial-of-Service (DoS): The type of attack whose goal is to make a
22       computer or a network unavailable to its users.
23   Dense Wavelength Division Multiplexing (DWDM): WDM using fiber
24       that carries more than forty light sources at different frequencies.
25   DES: See Data Encryption Standard.
26   Designated Router: In OSPF, a router that sends change information to
27       other routers in its area.
28   Destination: In a routing table, the column that shows the destination
29       network’s network part or subnet’s network part plus subnet part,
30       followed by zeroes. This row represents a route to this network or
31       subnet.
32   DHCP: See Dynamic Host Configuration Protocol.
33   Dial-Up Circuit: A circuit that only exists for the duration of a telephone
34       call.
35   Dictionary Attack: A password-cracking attack in which an attacker tries
36       to break a password by trying all words in a standard or customized
37       dictionary.
38   Dictionary Word: A common word, dangerous to use for a password
39       because easily cracked.
40   Dielectric Insulation: The non-conducting insulation that covers each
41       wire in 4-pair UTP, preventing short circuits between the electrical
42       signals traveling on different wires.
43   Diff-Serv: The field in an IP packet that can be used to label IP packets
44       for priority and other service parameters.
45   Digital Certificate Authentication: Authentication in which each user
46       has a public key and a private key. Authentication depends on the

                                                                     Chapter 1-11
 1       applicant knowing the true party’s private key; requires a digital
 2       certificate to give the true party’s public key.
 3   Digital Certificate: A document that gives the name of a true party, that
 4       true party’s public key, and other information; used in authentication.
 5   Digital Signaling: Signaling that uses a few states. Binary (two-state)
 6       transmission is a special case of digital transmission.
 7   Digital Signature: A calculation added to a plaintext message to
 8       authenticate it.
 9   Digital Subscriber Line (DSL): A technology that provides digital data
10       signaling over the residential customer’s existing single-pair UTP
11       voice-grade copper access line.
12   Digital-to-Analog Conversion (DAC): The conversion of transmissions
13       from the digital telephone network’s core to signals on the analog
14       local loop.
15   Direct Sequence Spread Spectrum (DSSS): Spread spectrum
16       transmission that spreads the signal over the entire bandwidth of a
17       channel.
18   Disaster Recovery: The reestablishment of information technology
19       operations.
20   Disaster: An incident that can stop the continuity of business operations,
21       at least temporarily.
22   Discovering: The first phase of network mapping, in which the program
23       finds out if hosts and subnets exist.
24   Disgruntled Employee: Employee who is upset with the firm or an
25       employee and who may take revenge through a computer attack.
26   Disgruntled Ex-Employee: Former employee who is upset with the firm
27       or an employee and who may take revenge through a computer attack.
28   Dish Antenna: An antenna that points in a particular direction, allowing it
29       to send stronger outgoing signals in that direction for the same power
30       and to receive weaker incoming signals from that direction.
31   Distance Vector Protocol: Routing protocol based on the number of hops
32       to a destination out a particular port.
33   Distort: To change in shape during propagation.
34   DLCI: See Data Link Control Identifier.
35   DMZ: See Demilitarized Zone.
36   DNS: See Domain Name System.
37   Domain Controller: In Microsoft Windows, a computer that manages the
38       computers in a domain.
39   Domain Name System (DNS): A server that provides IP addresses for
40       users who know only a target host’s host name. DNS servers also
41       provide a hierarchical system for naming domains.
42   Domain Name System (DNS): A system of servers that give out IP
43       addresses when sent requests containing host names. DNS servers are
44       also called name servers.
45   Domain: 1) In DNS, a group of resources (routers, single networks, and
46       hosts) under the control of an organization. 2) In Microsoft Windows,

                                                                     Chapter 1-12
 1        a grouping of resources used in an organization, made up of clients
 2        and servers.
 3   DoS: See Denial-of-Service.
 4   Dotted Decimal Notation: The notation used to ease human
 5        comprehension and memory in reading IP addresses.
 6   Downtime: A period of network unavailability.
 7   Drive-By Hacker: A hacker who parks outside a firm’s premises and
 8        eavesdrops on its data transmissions; mounts denial-of-service
 9        attacks; inserts viruses, worms, and spam into a network; or does
10        other mischief.
11   DSL Access Multiplexer (DSLAM): A device at the end office of the
12        telephone company that sends voice signals over the ordinary PSTN
13        and sends data over a data network such as an ATM network.
14   DSL: See Digital Subscriber Line.
15   DSLAM: See DSL Access Multiplexer.
16   DSSS: See Direct Sequence Spread Spectrum.
17   DSU: See Data Service Unit.
18   Dumb Terminal: A desktop machine with a keyboard and display but
19        little processing capability; processing is done on a host computer.
20   DWDM: See Dense Wavelength Division Multiplexing.
21   Dynamic Host Configuration Protocol (DHCP): The protocol used by
22        DHCP servers, which provide each user PC with a temporary IP
23        address to use each time he or she connects to the Internet.
24   EAP: See Extensible Authentication Protocol.
25   E-Commerce Software: Software that automates the creation of catalog
26        pages and other e-commerce functionality.
27   E-Commerce: Electronic commerce; buying and selling over the Internet.
28   Economy of Scale: In managed services, the condition of being cheaper to
29        manage the traffic of many firms than of one firm.
30   Egress Filtering: The filtering of traffic from inside a site going out.
31   Electromagnetic Interference (EMI): Unwanted electrical energy
32        coming from external devices, such as electrical motors, fluorescent
33        lights, and even nearby data transmission wires.
34   Electromagnetic Signal: A signal generated by oscillating electrons.
35   Electronic Catalog: An e-commerce site’s display that shows the goods
36        the site has for sale.
37   Electronic Commerce (E-Commerce): The buying and selling of goods
38        and services over the Internet.
39   Elliptic Curve Cryptosystem (ECC): Public key encryption method;
40        more efficient than RSA.
41   EMI: See Electromagnetic Interference.
42   Encapsulation: The placing of a message in the data field of another
43        message.
44   Encrypt: To mathematically process a message so that an interceptor
45        cannot read the message.
46   Encryption method: A method for encrypting plaintext messages.

                                                                   Chapter 1-13
 1   End Office Switch: The nearest switch of the telephone company to the
 2       customer premises.
 3   End Office: Telephone company switch that connects to the customer
 4       premises via the local loop.
 5   End-to-End: A layer where communication is governed directly between
 6       the transport process on the source host and the transport process on
 7       the destination host.
 8   Ephemeral Port Number: The temporary number a client selects
 9       whenever it connects to an application program on a server.
10       According to IETF rules, ephemeral port numbers should be between
11       49153 and 65535.
12   Equipment Room: The room, usually in a building’s basement, where
13       wiring connects to external carriers and internal wiring.
14   Error Advisement: In ICMP, the process wherein if an error is found,
15       there is no transmission, but the router or host that found the error
16       usually sends an ICMP error message to the source device to inform it
17       that an error has occurred. It is then up to the device to decide what to
18       do. (This is not the same as error correction because there is no
19       mechanism for the retransmission of lost or damaged packets.)
20   Error Rate: In biometrics, the normal rate of misidentification when the
21       subject is cooperating.
22   Ethernet 10Base2: Obsolete 10 Mbps Ethernet standard that uses coaxial
23       cable in a bus topology. Less expensive than 10Base5 but cannot
24       carry signals as far.
25   Ethernet 10Base5: Obsolete 10 Mbps Ethernet standard that uses coaxial
26       cable in a bus topology.
27   Ethernet Address: The 48-bit address the stations have on an Ethernet
28       network; often written in hexadecimal notation for human reading.
29   Ethernet Frame: A message at the data link layer in an Ethernet network.
30   Ethernet Switch: Switch following the Ethernet standard. Notable for
31       speed and low cost per frame sent. Dominates LAN switching.
32   EtherPeek: A commercial traffic summarization program.
33   Excess Burst Speed: One of Frame Relay’s two-part PVC speeds; beyond
34       the CIR.
35   Exhaustive Key Search: Cracking a key by trying all possible keys to
36       decrypt a message.
37   Exploit: A break-in program; a program that exploits known
38       vulnerabilities.
39   Extended Star Topology: The type of topology wherein there are
40       multiple layers of switches organized in a hierarchy, in which each
41       node has only one parent node; used in Ethernet; more commonly
42       called a hierarchical topology.
43   Extensible Authentication Protocol (EAP): A protocol that authenticates
44       users with authentication data (such as a password or a response to a
45       challenge based on a station’s digital certificate) and authentication
46       servers.

                                                                      Chapter 1-14
 1   Exterior Routing Protocol: Routing protocol used between autonomous
 2        systems.
 3   Extranet: A network that uses TCP/IP Internet standards to link several
 4        firms together but that is not accessible to people outside these firms.
 5        Even within the firms of the extranet, only some of each firm’s
 6        computers have access to the network.
 7   Face Recognition: The scanning of passersby to identify terrorists or
 8        wanted criminals by the characteristics of their faces.
 9   Facilitating Server: A server that solves certain problems in P2P
10        interactions but that allows clients to engage in P2P communication
11        for most of the work.
12   False Alarm: An apparent incident that proves not to be an attack.
13   False Positive: A false alarm.
14   FDM: See Frame Division Multiplexing.
15   FHSS: See Frequency Hopping Spread Spectrum.
16   Fiber to the Home (FTTH): Optical fiber brought by carriers to
17        individual homes and businesses.
18   Field: A subdivision of a message header or trailer.
19   File Server Program Access: The form of client/server computing in
20        which the server’s only role is to store programs and data files, while
21        the client PC does the actual processing of programs and data files.
22   File Server: A server that allows users to store and share files.
23   File Service: Service on a file server that allows users to store and share
24        files.
25   File Sharing: The ability of computer users to share files that reside on
26        their own disk drives or on a dedicated file server.
27   Fingerprint Scanning: A form of biometric authentication that uses the
28        applicant’s fingerprints.
29   Fingerprinting: The second phase of network mapping, in which the
30        program determines the characteristics of hosts to determine if they
31        are clients, servers, or routers.
32   Firewall: A security system that examines each incoming packet. If the
33        firewall identifies the packet as an attack packet, the firewall discards
34        the packet and copies information about the discarded packet into a
35        log file.
36   First-Generation (1G): The initial generation of cellular telephony,
37        introduced in the 1980s. 1G systems were analog, were only given
38        about 50 MHz of spectrum, had large and few cells, and had very
39        limited speeds for data transmission.
40   Fixed Wireless Service: Local terrestrial wireless service in which the
41        user is at a fixed location.
42   Flag: A one-bit field.
43   Flat Rate: Local telephone service in which there is a fixed monthly
44        service charge but no separate fee for individual local calls.
45   Flow Control: The ability of one side in a conversation to tell the other
46        side to slow or stop its transmission rate.

                                                                        Chapter 1-15
 1   Forensics: The collection of data in a form suitable for presentation in a
 2       legal proceeding.
 3   Fractional T1: A type of private line that offers intermediate speeds at
 4       intermediate prices; usually operates at one of the following speeds:
 5       128 kbps, 256 kbps, 384 kbps, 512 kbps, or 768 kbps.
 6   FRAD: See Frame Relay Access Device.
 7   Fragment Offset Field: In IPv4, a flag field that tells a fragment’s
 8       position in a stream of fragments from an initial packet.
 9   Fragment: To break a message into multiple smaller messages. TCP
10       fragments application layer messages, while IP packets may be
11       fragmented by routers along the packet’s route.
12   Frame Check Sequence Field: A four-octet field used in error checking
13       in Ethernet. If an error is found, the frame is discarded.
14   Frame Relay Access Device (FRAD): Device that connects an internal
15       site network to a Frame Relay network.
16   Frame: 1) A message at the data link layer. 2) In time division
17       multiplexing, a brief time period, which is further subdivided into
18       slots.
19   Frequency Division Multiplexing (FDM): A technology used in
20       microwave transmission in which the microwave bandwidth is
21       subdivided into channels, each carrying a single circuit.
22   Frequency Hopping Spread Spectrum (FHSS): Spread spectrum
23       transmission that uses only the bandwidth required by the signal but
24       hops frequently within the spread spectrum channel.
25   Frequency Modulation: Modulation in which one frequency is chosen to
26       represent a 1 and another frequency is chosen to represent a 0.
27   Frequency Spectrum: The range of all possible frequencies from zero
28       hertz to infinity.
29   Frequency: The number of complete cycles a radio wave goes through
30       per second. In sound, frequency corresponds to pitch.
31   FTTH: See Fiber to the Home.
32   Full Control: In Microsoft Windows, an omnibus permission, equal to all
33       of the other Microsoft Windows Server permissions.
34   Full-Duplex: A type of communication that supports simultaneous two-
35       way transmission. Almost all communication systems today are full-
36       duplex systems.
37   Full-Duplex: The mode of operation wherein both parties in a
38       conversation can send and receive simultaneously.
39   Fully Configured: A system with all necessary options.
40   Functional Department: General name for departments in firm other than
41       the IT department; marketing, accounting, and so forth.
42   Gateway Controller: In IP telephony, a device that controls the operation
43       of signaling gateways and media gateways.
44   Gateway: An obsolete term for ―router;‖ still in use by Microsoft.
45   General Packet Radio Service (GPRS): The technology to which many
46       GSM systems are now being upgraded. GPRS can combine two or

                                                                    Chapter 1-16
 1       more GSM time slots within a channel and so can offer data
 2       throughput near that of a telephone modem. Often called a 2.5G
 3       technology.
 4   GEO: See Geosynchronous Earth Orbit Satellite.
 5   Geosynchronous Earth Orbit Satellite (GEO): The type of satellite
 6       most commonly used in fixed wireless access today; orbits the earth at
 7       about 36,000 km (22,300 miles).
 8   Get: An SNMP command sent by the manager that tells the agent to
 9       retrieve certain information and return this information to the
10       manager.
11   GHz: See Gigahertz.
12   Gigahertz (GHz): One billion hertz.
13   GIGO: Garbage in, garbage out. If bad information is put into a system,
14       only bad information can come out.
15   Global System for Mobile communication (GSM): The cellular
16       telephone technology on which nearly the entire world standardized
17       for 2G service. GSM uses 200 kHz channels and implements TDM.
18   Gnutella: A pure P2P file-sharing application that addresses the problems
19       of transient presence and transient IP addresses without resorting to
20       the use of any server.
21   Golden Zone: The portion of the frequency spectrum from the high
22       megahertz range to the low gigahertz range, wherein commercial
23       mobile services operate.
24   GPO: See Group Policy Object.
25   GPRS: See General Packet Radio Service.
26   Grid Computing: Computing in which all devices, whether clients or
27       servers, share their processing resources.
28   Group Policy Object (GPO): A policy that governs a specific type of
29       resource on a domain.
30   GSM: See Global System for Mobile communication.
31   H.323: In IP telephony, one of the protocols used by signalling gateways.
32   Hacking: The intentional use of a computer resource without
33       authorization or in excess of authorization.
34   Half-Duplex: The mode of operation wherein two communicating NICs
35       must take turns transmitting.
36   Handoff: a) In wireless LANs, a change in access points when a user
37       moves to another location. b) In cellular telephony, transfer from one
38       cellsite to another, which occurs when a subscriber moves from one
39       cell to another within a system.
40   Hardened: Set up to protect itself, as a server or client.
41   Hash: The output from hashing.
42   Hashing: A mathematical process that, when applied to a bit string of any
43       length, produces a value of a fixed length, called the hash.
44   HDSL: See High-Rate Digital Subscriber Line.
45   HDSL2: A newer version of HDSL, that transmits in both directions at
46       1.544 Mbps.

                                                                    Chapter 1-17
 1   Header Checksum: The UDP datagram field that allows the receiver to
 2       check for errors.
 3   Header: The part of a message that comes before the data field.
 4   Headquarters: The First Bank of Paradise’s downtown office building
 5       that houses the administrative site.
 6   Hertz (Hz): One cycle per second, a measure of frequency.
 7   Hex Notation: See Hexadecimal Notation.
 8   Hexadecimal (Hex) Notation: The Base 16 notation that humans use to
 9       represent address 48-bit MAC source and destination addresses.
10   Hierarchical Topology: A network topology in which all switches are
11       arranged in a hierarchy, in which each switch has only one parent
12       switch above it (the root switch, however, has no parent); used in
13       Ethernet.
14   Hierarchy: 1) The type of topology wherein there are multiple layers of
15       switches organized in a hierarchy, in which each node has only one
16       parent node; used in Ethernet. 2) In IP addresses, three multiple parts
17       that represent successively more specific locations for a host.
18   High-Rate Digital Subscriber Line (HDSL): The most popular business
19       DSL, which offers symmetric transmission at 768 kbps in both
20       directions. See also HDSL2.
21   Hop-by-Hop: A layer in which communication is governed by each
22       individual switch or router along the path of a message.
23   Host Computer: 1) In terminal–host computing, the host that provides the
24       processing power; 2) on an internet, any host.
25   Host Part: The part of an IP address that identifies a particular host on a
26       subnet.
27   Host: Any computer attached to the Internet (can be either personal client
28       or server).
29   Hot Spot: A public location where anyone can connect to an access point
30       for Internet access.
31   HTML Body: Body part in a Hypertext Markup Language message.
32   HTML: See Hypertext Markup Language.
33   HTTP Request Message: In HTTP, a message in which a client requests
34       a file or another service from a server.
35   HTTP Request–Response Cycle: An HTTP client request followed by an
36       HTTP server response.
37   HTTP Response Message: In HTTP, a message in which a server
38       responds to a client request; either contains a requested file or an error
39       message explaining why the requested file could not be supplied.
40   HTTP: See Hypertext Transfer Protocol.
41   Hub: An early device used by Ethernet LANs to move frames in a system.
42       Hubs broadcast each arriving bit out all ports except for the port that
43       receives the signal.
44   Hub-and-Spoke Topology: A topology in which all communication goes
45       through one site.
46   Hybrid TCP/IP-OSI Standards Architecture: The architecture that uses

                                                                       Chapter 1-18
 1       OSI standards at the physical and data link layers and TCP/IP
 2       standards at the internet, transport, and application layers; dominant in
 3       corporations today.
 4   Hypertext Markup Language (HTML): The language used to create
 5   webpages.
 6   Hypertext Transfer Protocol (HTTP): The protocol that governs
 7       interactions between the browser and webserver application program.
 8   Hz: See Hertz.
 9   ICC: See International Common Carrier.
10   ICF: See Internet Connection Firewall.
11   ICMP Echo: A message sent by a host or router to another host or router.
12       If the target device’s internet process is able to do so, it will send back
13       an echo response message.
14   ICMP Error Message: A message sent in error advisement to inform a
15       source device that an error has occurred.
16   ICMP: See Internet Control Message Protocol.
17   ICS: See Internet Connection Sharing.
18   IDC: See Insulation Displacement Connection.
19   Identification Field: In IPv4, header field used to reassemble fragmented
20       packets. Each transmitted packet is given a unique identification field
21       value. If the packet is fragmented en route, all fragments are given the
22       initial packet’s identification field value.
23   IDS: See Intrusion Detection System.
24   IEEE: See Institute for Electrical and Electronics Engineers.
25   IETF: See Internet Engineering Task Force.
26   ILEC: See Incumbent Local Exchange Carrier.
27   IM: See Instant Messaging.
28   Image: An exact copy.
29   IMAP: See Internet Message Access Protocol.
30   Impostor: Someone who claims to be someone else.
31   Incident Severity: The degree of destruction inflicted by an attack.
32   Incident: A successful attack.
33   Incumbent Local Exchange Carrier (ILEC): The traditional monopoly
34       telephone company within each LATA.
35   Index Server: A server used by Napster. Stations connected to Napster
36       would first upload a list of their files available for sharing to index
37       servers. Later, when they searched, their searches went to the index
38       servers and were returned from there.
39   Individual Throughput: The actual speed a single user receives (usually
40       much lower than aggregate throughput in a system with shared
41       transmission speed).
42   Ingress Filtering: The filtering of traffic coming into a site from the
43       outside.
44   Inherit: When permissions are assigned to a user in a directory, user
45       automatically receives the same permissions in subdirectories unless
46       this automatic inheritance is blocked.

                                                                        Chapter 1-19
 1   Initial Installation: The initial phase of a product’s life cycle. Ongoing
 2        costs may be much higher.
 3   Initial Labor Costs: The labor costs of setting up a system for the first
 4        time.
 5   Initial Sequence Number (ISN): The sequence number placed in the first
 6        TCP segment a side transmits in a session; selected randomly.
 7   Instance: An actual example of a category.
 8   Instant Messaging (IM): A popular P2P application that allows two users
 9        to type messages back and forth in real time.
10   Institute for Electrical and Electronics Engineers (IEEE): An
11        international organization whose 802 LAN/MAN Standards
12        Committee creates many LAN standards.
13   Insulation Displacement Connection (IDC): Connection method used in
14        UTP. A connector bites through the insulation around a wire, making
15        contact with the wire inside.
16   Interexchange Carrier (IXC): A telephone carrier that transmits voice
17        traffic between LATAs.
18   Interface: 1) The router’s equivalent of a network interface card; a port on
19        a router that must be designed for the network to which it connects.
20        2) In Web services, the outlet through which an object communicates
21        with the outside world.
22   Interference: See Electromagnetic Interference.
23   Interior Routing Protocol: Routing protocol used within a firm’s
24        internet.
25   Internal Back-End System: In e-commerce, an internal e-commerce
26        system that handles accounting, pricing, product availability,
27        shipment, and other matters.
28   Internal Router: A router that connects different LANs within a site.
29   International Common Carrier (ICC): A telephone carrier that provides
30        international service.
31   International Organization for Standardization (ISO): A strong
32        standards agency for manufacturing, including computer
33        manufacturing.
34   International Telecommunications Union-Telecommunications
35        Standards Sector (ITU-T): A standards agency that is part of the
36        United Nations and that oversees international telecommunications.
37   Internet Backbone: The collection of all Internet Service Providers that
38        provide Internet transmission service.
39   Internet Connection Firewall (ICF): The built-in stateful firewall that
40        comes with Windows XP.
41   Internet Connection Sharing (ICS): Microsoft Windows service that
42        allows a PC to connect to the Internet through another PC.
43   Internet Control Message Protocol (ICMP): The protocol created by the
44        IETF to oversee supervisory messages at the internet layer.
45   Internet Engineering Task Force (IETF): TCP/IP’s standards agency.
46   Internet Layer: The layer that governs the transmission of a packet across

                                                                      Chapter 1-20
 1        an entire internet.
 2   Internet Message Access Protocol (IMAP): One of the two protocols
 3        used to download received e-mail from an e-mail server; offers more
 4        features but is less popular than POP.
 5   Internet Network: A network on the Internet owned by a single
 6        organization, such as a corporation, university, or ISP.
 7   Internet Protocol (IP): The TCP/IP protocol that governs operations at
 8        the internet layer. Governs packet delivery from host to host across a
 9        series of routers.
10   Internet: 1) A group of networks connected by routers so that any
11        application on any host on any network can communicate with any
12        application on any other host on any other network. 2) A general term
13        for any internetwork (spelled with a lowercase i); 3) the worldwide
14        Internet (spelled with a capital I).
15   Internetwork Operating System (IOS): The operating system that Cisco
16        Systems uses on all of its routers and most of its switches.
17   Intranet: An internet for internal transmission within firms; uses the
18        TCP/IP transmission standards that govern transmission over the
19        Internet.
20   Intrusion Detection System (IDS): A security system that examines
21        messages traveling through a network. IDSs look at traffic broadly,
22        identifying messages that are suspicious. Instead of discarding these
23        packets, IDSs will sound an alarm.
24   IOS: See Internetwork Operating System.
25   IP Address: An Internet Protocol address; the address that every computer
26        needs when it connects to the Internet; IP addresses are 32 bits long.
27   IP Security (IPsec): A set of standards that operate at the internet layer
28        and provide security to all upper layer protocols transparently.
29   IP Telephone: A telephone that has the electronics to encode voice for
30        digital transmission and to send and receive packets over an IP
31        internet.
32   IP Telephony: The transmission of telephone signals over IP internets
33        instead of over circuit-switched networks.
34   IP Version 4 (IPv4): The standard that governs most routers on the
35        Internet and private internets.
36   IP Version 6 (IPv6): A new version of the Internet Protocol.
37   IP: See Internet Protocol.
38   Ipconfig (ipconfig): A command used to find information about one’s
39        own computer, used in newer versions of Windows (the command is
40        typed as ipconfig /all[Enter] at the command line).
41   IPsec Gateway: Border device at a site that converts between internal data
42        traffic into protected data traffic that travels over an untrusted system
43        such as the Internet.
44   IPsec: See IP Security.
45   IPv4: See IP Version 4.
46   IPv6: See IP Version 6.

                                                                       Chapter 1-21
 1   IPX/SPX Architecture: Non-TCP/IP standards architecture found at
 2        upper layers in LANs; required on all older Novell NetWare file
 3        servers.
 4   Iris: The colored part of the eye, used in biometric authentication.
 5   ISN: See Initial Sequence Number.
 6   ISO: See International Organization for Standardization.
 7   IT Guru. See OPNET IT Guru.
 8   ITU-T: See International Telecommunications Union-
 9        Telecommunications Standards Sector.
10   IXC: See Interexchange Carrier.
11   Jacket: The outer plastic covering, made of PVC, that encloses and
12        protects the four pairs of wires in UTP or the core and cladding in
13        optical fiber.
14   Java Applet: Small Java program that is downloaded as part of a
15        webpage.
16   Jitter: Variability in latency.
17   Key Exchange: The secure transfer of a symmetric session key between
18        two communicating parties.
19   Key: A bit string used with an encryption method to encrypt and decrypt a
20        message. Different keys used with a single encryption method will
21        give different ciphertexts from the same plaintext.
22   Label Header: In MPLS, the header added to packets before the IP
23        header; contains information that aids and speeds routers in choosing
24        which interface to send the packet back out.
25   Label Number: In MPLS, number in the label header that aids label-
26        switching routers in packet sending.
27   Label Switching Table: In MPLS, the table used by label-switching
28        routers to decide which interface to use to forward a packet.
29   LAN: See Local Area Network.
30   Language Independence: In SOAP, the fact that Web service objects do
31        not have to be written in any particular language.
32   LATA: See Local Access and Transport Area.
33   Latency: Delay, usually measured in milliseconds.
34   Layer 3: See Internet Layer.
35   Layer 4: See Transport Layer.
36   Layer 5: See Application Layer.
37   Layer 3 Switch: A router that does processing in hardware, that is much
38        faster and less expensive than traditional software-based routers.
39        Layer 3 switches are usually dominant in the Ethernet core above
40        workgroup switches.
41   Layer 4 Switch: A switch that examines the port number fields of each
42        arriving packet’s encapsulated TCP segment, allowing it to switch
43        packets based on the application they contain. Layer 4 switches can
44        give priority or even deny forwarding to IP packets from certain
45        applications.
46   Legacy Network: A network that uses obsolete technology; may have to

                                                                    Chapter 1-22
 1        be lived with for some time because upgrading all legacy networks at
 2        one time is too expensive.
 3   Legal Retention: Rules that require IM messages to be captured and
 4        stored in order to comply with legal requirements.
 5   Length Field: 1) The field in an Ethernet MAC frame that gives the
 6        length of the data field in octets. 2) The field in a UDP datagram that
 7        enables the receiving transport process to process the datagram
 8        properly.
 9   LEO: See Low Earth Orbit Satellite.
10   Line of Sight: An unobstructed path between the sender and receiver,
11        necessary for radio transmission at higher frequencies.
12   Link Aggregation: The use of two or more trunk links between a pair of
13        switches; also known as trunking or bonding.
14   Link State Protocol: Routing protocol in which each router knows the
15        state of each link between routers.
16   Link: Connection between a pair of routers.
17   Linux Distribution: A package purchased from a vendor that contains the
18        Linux kernel plus a collection of many other programs, usually taken
19        from the GNU project.
20   Linux: A freeware version of Unix that runs on standard PCs.
21   List Folder Contents: A Microsoft Windows Server permission that
22        allows the account owner to see the contents of a folder (directory).
23   LLC Header: See Logical Link Control Layer Header.
24   LLC: See Logical Link Control.
25   Load-Balancing Router: Router used on a server farm that sends client
26        requests to the first available server.
27   Local Access and Transport Area (LATA): One of the roughly 200 sites
28        regions the United States has been divided into for telephone service.
29   Local Area Network (LAN): A network within a site.
30   Local Loop: In telephony, the line used by the customer to reach the
31        PSTN’s central transport core.
32   Local: The value placed in the next-hop routing field of a routing table to
33        specify that the destination host is on the selected network or subnet.
34   Logical Link Control Layer Header: The header at the start of the data
35        field that describes the type of packet contained in the data field.
36   Logical Link Control Layer: The layer of functionality for the upper part
37        of the data link layer, now largely ignored.
38   Longest Match: The matching row that matches a packet’s destination IP
39        address to the greatest number of bits; chosen by a router when there
40        are multiple matches.
41   Loopback Address: The IP address When a user pings this IP
42        address, this will test their <ITAL>own</ITAL> computer’s
43        connection to the Internet.
44   Loopback Interface: A testing interface on a device. Messages sent to
45        this interface are sent back to the sending device.
46   Low Earth Orbit Satellite (LEO): A type of satellite used in mobile

                                                                      Chapter 1-23
 1      wireless transmission; orbits a few hundred miles or a few hundred
 2      kilometers above the earth.
 3   MAC Address: See Media Access Control.
 4   MAC: See Media Access Control.
 5   Mainframe Computer: The largest type of dedicated server; extremely
 6      reliable.
 7   Malware: Software that seeks to cause damage.
 8   Malware-Scanning Program: A program that searches a user’s PC
 9      looking for installed malware.
10   MAN: See Metropolitan Area Network.
11   Manageable Switch: A switch that has sufficient intelligence to be
12      managed from a central computer (the Manager).
13   Managed Device: A device that needs to be administered, such as
14      printers, hubs, switches, routers, application programs, user PCs, and
15      other pieces of hardware and software.
16   Managed Frame Relay: A type of Frame Relay service that takes on
17      most of the management that customers ordinarily would have to do.
18      Managed Frame Relay provides traffic reports and actively manages
19      day-to-day traffic to look for problems and get them fixed.
20   Management Information Base (MIB): A specification that defines what
21      objects can exist on each type of managed device and also the specific
22      characteristics of each object; the actual database stored on a manager
23      in SNMP. There are separate MIBs for different types of managed
24      devices; both a schema and a database.
25   Management Program: A program that helps network administrators
26      manage their networks.
27   Manager: See Network Management Program.
28   Manager: The central PC or more powerful computer that uses SNMP to
29      collect information from many managed devices.
30   Mask Operations: Applying a mask of ones and zeros to a bit stream.
31      Where the mask is 1, the original bit stream’s bit results. Otherwise,
32      the result is zero.
33   Mask: A 32-bit string beginning with a series of ones and ending a series
34      of zeroes; used by routing tables to Interpret IP address part sizes. The
35      ones designate either the network part or the network plus software
36      part.
37   Mature: Technology that has been under development long enough to
38      have its rough edges smoothed off.
39   Maximum Segment Size (MSS): The maximum size of TCP data fields
40      that a receiver will accept.
41   Maximum Transmission Unit (MTU): The maximum packet size that
42      can be carried by a particular LAN or WAN.
43   MD5: A popular hashing method.
44   Mean Time to Repair (MTTR): The average time it takes a staff to get a
45      network back up after it has been down.
46   Media Access Control (MAC): The process of controlling when stations

                                                                      Chapter 1-24
 1       transmit; also, the lowest part of the data link layer, defining
 2       functionality specific to a particular LAN technology.
 3   Media Gateway: A device that connects IP telephones networks to the
 4       ordinary public switched telephone network. Media gateways also
 5       convert between the signalling formats of the IP telephone system and
 6       the PSTN.
 7   Medium Earth Orbit Satellite (MEO): A type of satellite used in mobile
 8       wireless transmission; orbits a few thousand miles or a few thousand
 9       kilometers above the earth.
10   Megahertz (MHz): One million hertz.
11   MEO: See Medium Earth Orbit Satellite.
12   Mesh Topology: 1) A topology where there are many connections among
13       switches or routers, so there are many alternative routes for messages
14       to get from one end of the network to the other. 2) In network design,
15       a topology that provides direct connections between every pair of
16       sites.
17   Message Digest: The result of hashing a plaintext message. The message
18       digest is signed with the sender’s private key to produce the digital
19       signature.
20   Message Integrity: The assurance that a message has not been changed en
21       route; or if a message has been changed, the receiver can tell that it
22       has.
23   Message Timing: Controlling when hardware or software processes may
24       transmit.
25   Message Unit: Local telephone service in which a user is charged based
26       on distance and duration.
27   Message: A discrete communication between hardware or software
28       processes.
29   Method: In Web services, a well-defined action that a SOAP message can
30       request.
31   Metric: A number describing the desirability of a route represented by a
32       certain row in a routing table.
33   Metropolitan Area Ethernet: Ethernet operating at the scale of a
34       metropolitan area network.
35   Metropolitan Area Network (MAN): A WAN that spans a single urban
36       area.
37   MHz: See Megahertz.
38   MIB: See Management Information Base.
39   Microsoft Windows Server: Microsoft’s network operating system for
40       servers, which comes in three versions: NT, 2000, and 2003.
41   Microsoft Windows XP Home: The dominant operating system today for
42       residential PCs.
43   Microsoft Windows XP Professional: A version of Windows XP
44       designed to be run in organization; integrates with Windows Server
45       services.
46   Millisecond (ms): The unit in which latency is measured.

                                                                    Chapter 1-25
 1   MIME: See Multipurpose Internet Mail Extensions.
 2   Ministry of Telecommunications: A government-created regulatory body
 3       that oversees PTTs.
 4   Mobile IP: A system for handling IP addresses for mobile devices.
 5   Mobile Telephone Switching Office (MTSO): A control center that
 6       connects cellular customers to one another and to wired telephone
 7       users, as well as overseeing all cellular calls (determining what to do
 8       when people move from one cell to another, including which cellsite
 9       should handle a caller when the caller wishes to place a call).
10   Mobile Wireless Access: Local wireless service in which the user may
11       move to different locations.
12   Modal Bandwidth: The measure of multimode fiber quality; the fiber’s
13       bandwidth–distance product. A modal bandwidth of 200 MHz-km
14       means that if your bandwidth is 100 MHz, then you can transmit
15       2 km.
16   Modal Dispersion: The main propagation problem for optical fiber;
17       dispersion in which the difference in the arrival times of various
18       modes (permitted light rays) is too large, causing the light rays of
19       adjacent pulses to overlap in their arrival times and rendering the
20       signal unreadable.
21   Mode: An angle light rays are permitted to enter an optical fiber core.
22   Modify: A Microsoft Windows Server permission that gives an account
23       owner additional permissions to act upon files, for example, the
24       permission to delete a file, which is not included in Write.
25   Modulate: To convert digital signals to analog signals.
26   Momentary Traffic Peak: A surplus of traffic that briefly exceeds the
27       network’s capacity, happening only occasionally.
28   Monochrome Text: Text of one color against a contrasting background.
29   More Fragments Field: In IPv4, a flag field that indicates whether there
30       are more fragments (set) or not (not set).
31   MPLS: See Multiprotocol Label Switching.
32   Ms: See Millisecond.
33   MS-CHAP: Microsoft version of the Challenge–Response Authentication
34       Protocol.
35   MSS: See Maximum Segment Size.
36   MTSO: See Mobile Telephone Switching Office.
37   MTTR: See Mean Time to Repair.
38   MTU: See Maximum Transmission Unit.
39   Multicasting: Simultaneously sending messages to multiple stations but
40       not to all stations.
41   Multilayer Security: Applying security at more than one layer to provide
42       defense in depth.
43   Multimode Fiber: The most common type of fiber in LANs, wherein
44       light rays in a pulse can enter a fairly thick core at multiple angles.
45   Multipath Interference: Interference caused when a receiver receives
46       two or more signals—a direct signal and one or more reflected

                                                                     Chapter 1-26
 1       signals. The multiple signals may interfere with one another.
 2   Multiplex: To mix multiple signals together on the same line.
 3   Multiplexing: 1) Having the packets of many conversations share trunk
 4       lines; reduces trunk line cost. 2) The ability of a protocol to carry
 5       messages from multiple next-higher-layer protocols in a single
 6       communication session.
 7   Multiprocessing Computer: A computer with multiple microprocessors.
 8       This allows it to run multiple programs at the same time.
 9   Multiprotocol Label Switching (MPLS): A traffic management tool used
10       by many ISPs.
11   Multiprotocol Router: A router that can handle not only TCP/IP
12       internetworking protocols, but also internetworking protocols for
13       IPX/SPX, SNA, and other standards architectures.
14   Multiprotocol: Characterized by implementing many different protocols
15       and products following different architectures.
16   Multipurpose Internet Mail Extensions (MIME): A standard for
17       specifying the contents of files.
18   Mutual Authentication: Authentication by both parties.
19   Name Server: See Domain Name System.
20   Nanometer (nm): The measure used for wavelengths; one billionth of a
21       meter (10−9 meters).
22   NAP: See Network Access Point.
23   Narrowband: 1) A channel with a small bandwidth and, therefore, a low
24       maximum speed; 2) low-speed transmission.
25   NAT: See Network Address Translation.
26   Netstat: A popular route analysis tool, which gives data on current
27       connections between a computer and other computers.
28   Network Access Point (NAP): A site where ISPs interconnect and
29       exchange traffic.
30   Network Address Translation (NAT): Converting an IP address into
31       another IP address, usually at a border firewall; disguises a host’s true
32       IP address from sniffers. Allows more internal addresses to be used
33       than an ISP supplies a firm with external addresses.
34   Network Architecture: 1) A broad plan that specifies everything that
35       must be done for two application programs on different networks on
36       an internet to be able to work together effectively. 2) A broad plan for
37       how the firm will connect all of its computers within buildings
38       (LANs), between sites (WANs), and to the Internet; also includes
39       security devices and services.
40   Network Interface Card (NIC): Printed circuit expansion board for a PC;
41       handles communication with a network; sometimes built into the
42       motherboard.
43   Network Layer: In OSI, Layer 3; governs internetworking. OSI network
44       layer standards are rarely used.
45   Network Management Agent (Agent): A piece of software on the
46       managed device that communicates with the manager on behalf of the

                                                                      Chapter 1-27
 1       managed device.
 2   Network Management Program (Manager): A program run by the
 3       network administrator on a central computer.
 4   Network Mapping: The act of mapping the layout of a network, including
 5       what hosts and routers are active and how various devices are
 6       connected. Its two phases are discovering and fingerprinting.
 7   Network Operating System (NOS): A PC server operating system.
 8   Network Part: The part of an IP address that identifies the host’s network
 9       on the Internet.
10   Network Security: The protection of a network from attackers.
11   Network Simulation: The building of a model of a network that is used to
12       project how the network will operate after a change.
13   Network Topology: The order in which a network’s nodes are physically
14       connected by transmission lines.
15   Network: In IP addressing, an organizational concept—a group of hosts,
16       single networks, and routers owned by a single organization.
17   Networked Application: An application that provides service over a
18       network.
19   Next Header Field: In IPv6, a header field that describes the header
20       following the current header.
21   Next-Hop Router: A router to which another router forwards a packet in
22       order to get the packet a step closer to reaching its destination host.
23   NIC: See Network Interface Card.
24   Nm (nm): See Nanometer.
25   Nmap: A network mapping tool that finds active IP addresses and then
26       fingerprints them to determine their operating system and perhaps
27       their operating system version.
28   Node: A client, server, switch, router, or other type of device in a network.
29   Noise Floor: The mean of the noise energy.
30   Noise Spike: An occasional burst of noise that is much higher or lower
31       than the noise floor; may cause the signal to become unrecognisable.
32   Noise: Random electromagnetic energy within wires; combines with the
33       data signal to make the data signal difficult to read.
34   Nonblocking: A nonblocking switch has enough aggregate throughput to
35       handle even the highest possible input load (maximum input on all
36       ports).
37   Nonoverlapping Channel: Channels whose frequencies do not overlap.
38   Normal Attack: An incident that does a small amount of damage and can
39       be handled by the on-duty staff.
40   North Shore: The First Bank of Paradise’s backup facility; able to take
41       over within minutes if Operations fails.
42   NOS: See Network Operating System.
43   Not Set: When a flags field is given the value 0.
44   Nslookup (nslookup): A command that allows a PC user to send DNS
45       lookup messages to a DNS server.
46   Object: A specific Web service.

                                                                      Chapter 1-28
 1   Object: In SNMP, an aspect of a managed device about which data is
 2       kept.
 3   OC: See Optical Carrier.
 4   Octet: A collection of eight bits; same as a byte.
 5   OFDM: See Orthogonal Frequency Division Multiplexing.
 6   Official Internet Protocol Standards: Standards deemed official by the
 7       IETF.
 8   Official Standards Organization: An internationally recognized
 9       organization that produces standards.
10   Omnidirectional Antenna: An antenna that transmits signals in all
11       directions and receives incoming signals equally well from all
12       directions.
13   On/Off Signaling: Signaling wherein the signal is on for a clock cycle to
14       represent a one, and off for a zero. (On/off signalling is binary.)
15   Ongoing Costs: Costs beyond initial installation costs; often exceed
16       installation costs.
17   Open Shortest Path First (OSPF): Complex but highly scalable interior
18       routing protocol.
19   Operations: The First Bank of Paradise’s building in an industrial area
20       that houses the bank’s mainframe operations and other back-office
21       technical functions; also has most of the bank’s IT staff, including its
22       networking staff.
23   OPNET ACE: See OPNET Application Characterization Environment.
24   OPNET Application Characterization Environment (ACE): A network
25       simulation program; focuses on application layer performance.
26   OPNET IT Guru: A popular network simulation program; focuses
27       primarily on data link layer and internet layer performance.
28   Optical Carrier (OC): A number that indicates SONET speeds.
29   Optical Fiber Cord: A length of optical fiber.
30   Optical Fiber: Cabling that sends signals as light pulses.
31   Orthogonal Frequency Division Multiplexing (OFDM): A form of
32       spread spectrum transmission that divides each broadband channel
33       into subcarriers and then transmits parts of each frame in each
34       subcarrier.
35   OSI Application Layer (Layer 7): The layer that governs application-
36       specific matters not covered by the OSI Presentation Layer or the OSI
37       Session Layer.
38   OSI Layer 5: See OSI Session Layer.
39   OSI Layer 6: See OSI Presentation Layer.
40   OSI Layer 7: See OSI Application Layer.
41   OSI Presentation Layer (Layer 6): The layer designed to handle data
42       formatting differences between two communicating computers.
43   OSI Session Layer (Layer 5): The layer that initiates and maintains a
44       connection between application programs on different computers.
45   OSI: The Reference Model of Open Systems Interconnection; the 7-layer
46       network standards architecture created by ISO and ITU-T; dominant

                                                                      Chapter 1-29
 1       at the physical and data link layers, which govern transmission within
 2       single networks (LANs or WANs).
 3   OSPF: See Open Shortest Path First.
 4   Out of Phase: In multipath interference, the condition of not being in
 5       sync, as occurs with signals that have been reflected and thus traveled
 6       different distances and not arrived at the receiver at the same time.
 7   Outsourcing: Paying other firms to handle some, most, or all IT chores.
 8   Overprovision: To install much more capacity in switches and trunk links
 9       than will be needed most of the time, so that momentary traffic peaks
10       will not cause problems.
11   Oversubscription: In Frame Relay, the state of having port speeds less
12       than the sum of PVC speeds.
13   P2P: See Peer-to-Peer Architecture.
14   Packet Capture and Display Program: A program that captures selected
15       packets or all of the packets arriving at or going out of a NIC.
16       Afterward, the user can display key header information for each
17       packet in greater or lesser detail.
18   Packet Filter Firewall: A firewall that examines fields in the internet and
19       transport headers of individual arriving packets. The firewall makes
20       pass/deny decisions based upon the contents of IP, TCP, UDP, and
21       ICMP fields.
22   Packet Switching: The breaking of conversations into short messages
23       (typically a few hundred bits long); allows multiplexing on trunk lines
24       to reduce trunk line costs.
25   Packet: A message at the internet layer.
26   PAD Field: A field that the sender adds to an Ethernet frame if the data
27       field is less than 46 octets long (the total length of the PAD plus data
28       field must be exactly 46 octets long).
29   PAN: See Personal Area Network.
30   Parallel Transmission: A form of transmission that uses multiple wire
31       pairs or other transmission media simultaneously to send a signal;
32       increases transmission speed.
33   Password Length: The number of characters in a password.
34   Password Reset: The act of changing a password to some value known
35       only to the systems administrator and the account owner.
36   Password: A secret keyboard string only the account holder should know;
37       authenticates user access to an account.
38   Patch Cord: A cord that comes precut in a variety of lengths, with a
39       connector attached; usually either UTP or optical fiber.
40   Patch: An addition to a program that will close a security vulnerability in
41       that program.
42   Payload: 1) A piece of code that can be executed by a virus or worm after
43       it has spread to multiple machines. 2) ATM’s name for a data field.
44   Payment Mechanism: In e-commerce, ways for purchasers to pay for
45       their ordered goods or services.
46   PBX: See Private Branch Exchange.

                                                                      Chapter 1-30
 1   PC Server: A server that is a personal computer.
 2   PCM: Pulse Code Modulation.
 3   Peer-to-Peer Architecture (P2P): The application architecture in which
 4       most or all of the work is done by cooperating user computers, such
 5       as desktop PCs. If servers are present at all, they serve only
 6       facilitating roles and do not control the processing.
 7   Peer-to-Peer Service: Service wherein client PCs provide services to one
 8       another.
 9   Perfect Internal Reflection: When light in optical fiber cabling begins to
10       spread, it hits the cladding and is reflected back into the core so that
11       no light escapes.
12   Permanent IP Address: An IP address given to a server that the server
13       keeps and uses every single time it connects to the Internet. (This is in
14       contrast to client PCs, which receive a new IP address every time they
15       connect to the Internet.)
16   Permanent Virtual Circuit (PVC): A PSDN connection between
17       corporate sites that is set up once and kept in place for weeks, months,
18       or years at a time.
19   Permission: A rule that determines what an account owner can do to a
20       particular resource (file or directory).
21   Personal Area Network (PAN): A small wireless network used by a
22       single person.
23   Phase Modulation: Modulation in which one wave serves as a reference
24       wave or a carrier wave. Another wave varies its phase to represent
25       one or more bits.
26   Physical Layer: The standards layer that governs physical transmission
27       between adjacent devices; OSI Layer 1.
28   Physical Link: A connection linking adjacent devices on a network.
29   Piggybacking: The act of an attacker being allowed physical entrance to a
30       building by following a legitimate user through a locked door that the
31       victim has opened.
32   Ping: Sending a message to another host and listening for a response to
33       see if it is active.
34   Pinging: Sending an echo request message.
35   PKI: See Public Key Infrastructure.
36   Plaintext: The original message the sender wishes to send to the receiver;
37       not limited to text messages.
38   Planning: Developing a broad security strategy that will be appropriate
39       for a firm’s security threats.
40   Plan–Protect–Respond Cycle: The basic management cycle in which the
41       three named stages are executed repeatedly.
42   Plenum: The type of cabling that must be used when cables run through
43       airways to prevent toxic fumes in case of fire.
44   Point of Presence (POP): 1) In cellular telephony, a site at which various
45       carriers that provide telephone service are interconnected. 2) In
46       PSDNs, a point of connection for user sites. There must be a private

                                                                      Chapter 1-31
 1       line between the site and the POP.
 2   Point-to-Point Topology: A topology wherein two nodes are connected
 3       directly.
 4   Point-to-Point Tunneling Protocol (PPTP): A remote access VPN
 5       security standard offering moderate security. PPTP works at the data
 6       link layer, and it protects all messages above the data link layer,
 7       providing protection transparently.
 8   POP: See 1) Point of Presence. 2) See Post Office Protocol.
 9   Port Number: The field in TCP and UDP that tells the transport process
10       what application process sent the data in the data field or should
11       receive the data in the data field.
12   Port: In TCP and UDP messages, a header field that designates the
13       application layer process on the server side and a specific connection
14       on the client side.
15   Portfolio: A planned collection of projects.
16   Post Office Protocol (POP): The most popular protocol used to download
17       e-mail from an e-mail server to an e-mail client.
18   PPTP: See Point-to-Point Tunneling Protocol.
19   Preamble Field: The initial field in an Ethernet MAC frame; synchronizes
20       the receiver’s clock to the sender’s clock.
21   Presence Server: A server used in many P2P systems; knows the IP
22       addresses of each user and also whether the user is currently on line
23       and perhaps whether or not the user is willing to chat.
24   Presentation Layer: See OSI Presentation Layer.
25   Print Server: An electronic device that receives print jobs and feeds them
26       to the printer attached to the print server.
27   Printer Sharing: Allowing multiple PCs to share a single printer.
28   Priority Level: The three-bit field used to give a frame one of eight
29       priority levels from 000 (zero) to 111 (eight).
30   Priority: Preference given to latency-sensitive traffic, such as voice and
31       video traffic, so that latency-sensitive traffic will go first if there is
32       congestion.
33   Private Branch Exchange (PBX): An internal telephone switch.
34   Private IP Address: An IP address that may be used only within a firm.
35       Private IP addresses have three designated ranges: 10.x.x.x,
36       192.168.x.x, and 172.16.x.x through 172.31.x.x.
37   Private Key: A key that only the true party should know. Part of a public
38       key–private key pair.
39   Private Line Circuit: A circuit that is always on; carries data much faster
40       than dial-up circuits and can multiplex calls.
41   Probable Annual Loss: The likely annual loss from a particular threat.
42       The cost of a successful attack times the probability of a successful
43       attack in a one-year period.
44   Probe Packet: A packet sent into a firm’s network during scanning;
45       responses to the probe packet tend to reveal information about a
46       firm’s general network design and about its individual computers—

                                                                       Chapter 1-32
 1       including their operating systems.
 2   Problem Update: An update that causes disruptions, such as slowing
 3       computer operation.
 4   Propagate: To travel.
 5   Propagation Effects: Changes in the signal during propagation.
 6   Property: A characteristic of an object.
 7   Protecting: Implementing a strategic security plan; the most time-
 8       consuming stage in the plan–protect–respond management cycle.
 9   Protocol Fidelity: The assurance that an application using a particular
10       port is the application it claims to be.
11   Protocol Field: In IP, a field that designates the protocol of the message in
12       the IP packet’s data field.
13   Protocol: 1) A standard that governs interactions between hardware and
14       software processes at the same layer but on different hosts. 2) In IP,
15       the header field that describes the content of the data field.
16   Provision: To install and set up a local loop access line.
17   PSDN: See Public Switched Data Network.
18   PSTN: See Public Switched Telephone Network.
19   PTT: See Public Telephone and Telegraphy Authority.
20   Public IP Address: An IP address that must be unique on the Internet.
21   Public Key Authentication: Authentication in which each user has a
22       public key and a private key. Authentication depends on the applicant
23       knowing the true party’s private key; requires a digital certificate to
24       give the true party’s public key.
25   Public Key Encryption: Encryption in which each side has a public key
26       and a private key, so there are four keys in total for bidirectional
27       communication. The sender encrypts messages with the receiver’s
28       public key. The receiver, in turn, decrypts incoming messages with
29       the receiver’s own private key.
30   Public Key Infrastructure (PKI): A total system (infrastructure) for
31       public key encryption.
32   Public Key: A key that is not kept secret. Part of a public key–private key
33       pair.
34   Public Switched Data Network (PSDN): A carrier WAN that provides
35       data transmission service. The customer only needs to connect to the
36       PSDN by running one private line from each site to the PSDN
37       carrier’s nearest POP.
38   Public Switched Telephone Network (PSTN): The worldwide telephone
39       network.
40   Public Telephone and Telegraphy authority (PTT): The traditional title
41       for the traditional monopoly telephone carrier in most countries.
42   Pulse Code Modulation (PCM): An analog-to-digital conversion
43       technique in which the ADC samples the bandpass-filtered signal
44       8,000 times per second, each time measuring the intensity of the
45       signal and representing the intensity by a number between 0 and 255.
46   PVC: See Permanent Virtual Circuit.

                                                                      Chapter 1-33
 1   QAM: See Quadrature Amplitude Modulation.
 2   QoS: See Quality of Service.
 3   QPSK: See Quadrature Phase Shift Keying.
 4   Quadrature Amplitude Modulation (QAM): Modulation technique that
 5       uses two carrier waves—a sine carrier wave and a cosine carrier
 6       wave. Each can vary in amplitude.
 7   Quadrature Phase Shift Keying (QPSK): Modulation with four possible
 8       phases. Each of the four states represents two bits (00, 01, 10, and
 9       11).
10   Quality of Service (QoS): Numerical service targets that must be met by
11       networking staff.
12   Quality-of-Service (QoS) Parameters: In IPv4, service quality
13       parameters applied to all packets with the same TOS field value.
14   Radio Wave: An electromagnetic wave in the radio range.
15   RAS: See Remote Access Server.
16   Read and Execute: A set of Microsoft Windows Server permissions
17       needed to run executable programs.
18   Read: A Microsoft Windows Server permission that allows an account
19       owner to read files in a directory. This is read-only access; without
20       further permissions, the account owner cannot change the files.
21   Real Time Protocol (RTP): The protocol that adds headers that contain
22       sequence numbers to ensure that the UDP datagrams are placed in
23       proper sequence and that they contain time stamps so that jitter can be
24       eliminated.
25   Redundancy: Duplication of a hardware device in order to enhance
26       reliability.
27   Regenerate: In a switch or router, to clean up a signal before sending it
28       back out.
29   Relay Server: A server used in some IM systems, which every message
30       flows through. Relay servers permit the addition of special services,
31       such as scanning for viruses when files are transmitted in an IM
32       system.
33   Reliability: The situation of errors being corrected by resending lost or
34       damaged messages.
35   Remote Access Server (RAS): A server to which remote users connect in
36       order to have their identities authenticated so they can get access to a
37       site’s internal resources.
38   Remote Monitoring (RMON) Probe: A specialized type of agent that
39       collects data on network traffic passing through its location instead of
40       information about the RMON probe itself.
41   Repeat Purchasing: In e-commerce, a consumer returning to a site where
42       he or she had made a purchase previously and making another
43       purchase; essential to profitability.
44   Request for Comment (RFC): A document produced by the IETF that
45       may become designated as an Official Internet Protocol Standard.
46   Request to Send/Clear to Send: A system that uses request-to-send and

                                                                      Chapter 1-34
 1       clear-to-send messages to control transmissions and avoid collisions
 2       in wireless transmission.
 3   Request to Send: A message sent to an access point when a station wishes
 4       to send and is able to send because of CSMA/CA. The station may
 5       send when it receives a clear-to-send message.
 6   Resegment: Dividing a collision domain into several smaller collision
 7       domains to reduce congestion and latency.
 8   Responding: In security, the act of stopping and repairing an attack.
 9   Response Message: In Challenge–Response Authentication Protocols, the
10       message that the applicant returns to the verifier.
11   Response Time: The difference between the time a user types a request to
12       time the user receives a response.
13   Retention: Rules that require IM messages to be captured and stored in
14       order to comply with legal requirements.
15   RFC 2822: The standard for e-mail bodies that are plaintext messages.
16   RFC 822: The original name for RFC 2822.
17   RFC: See Request for Comment.
18   Ring Topology: A topology in which stations are connected in a loop and
19       messages pass in only one direction around the loop.
20   RIP: See Routing Information Protocol.
21   Risk Analysis: The process of balancing threats and protection costs.
22   RJ-45 Connector: The connector at the end of a UTP cord, which plugs
23       into an RJ-45 jack.
24   RJ-45 Jack: The type of jack into which UTP cords’ RJ-45 connectors
25       may plug.
26   RMON Probe: See Remote Monitoring Probe.
27   Roaming: The situation when a subscriber leaves a metropolitan cellular
28       system and goes to another city or country. Roaming requires the
29       destination cellular system to be technologically compatible with the
30       subscriber’s cellphone. It also requires administration permission
31       from the destination cellular system.
32   Rogue Access Point: An access point set up by a department or individual
33       and not sanctioned by the firm.
34   Root: 1) The level at the top of a DNS hierarchy, consisting of all domain
35       names. 2) A super account on a Unix server that automatically has full
36       permissions in every directory on the server.
37   Route Analysis: Determining the route a packet takes between your host
38       and another host and analyzing performance along this route.
39   Route: The path that a packet takes across an internet.
40   Router: A device that forwards packets within an internet. Routers
41       connect two or more single networks (subnets).
42   Routing Information Protocol (RIP): A simple but limited interior
43       routing protocol.
44   Routing Protocol: A protocol that allows routers to transmit routing table
45       information to one another.
46   Routing: 1). The forwarding of IP packets; 2) the exchange of routing

                                                                    Chapter 1-35
 1       protocol information through routing protocols.
 2   RSA: Popular public key encryption method.
 3   RTP: See Real Time Protocol.
 4   RTS/CTS: See Request to Send/Clear to Send.
 5   RTS: See Request to Send.
 6   Sample: To read the intensity of a signal.
 7   SC Connector: A square optical fiber connector, recommended in the
 8       TIA/EIA-568 standard for use in new installations.
 9   Scalability: The ability of a technology to handle growth.
10   Scanning: To try to determine a network’s design through the use of
11       probe packets.
12   Schema: The design of a database, telling the specific types of
13       information the database contains.
14   Scope: A parameter on a DHCP server that determines how many subnets
15       the DHCP server may serve.
16   Script Kiddie: An attacker who possesses only modest skills but uses
17       attack scripts created by experienced hackers; dangerous because
18       there are so many.
19   SDH: See Synchronous Digital Hierarchy.
20   Second-and-a-Half Generation (2.5G): A nickname for GPRS systems,
21       which offer a substantial improvement over plain 2G GSM but which
22       is not a full third-generation service.
23   Second-Generation (2G): The second generation of cellular telephony,
24       introduced in the early 1990s. Offers the improvements of digital
25       service, 150 MHz of bandwidth, a higher frequency range of
26       operation, and slightly higher data transmission speeds.
27   Second-Level Domain: The third level of a DNS hierarchy, which usually
28       specifies an organization (e.g.,,
29   Secure Hash Algorithm (SHA): A hashing algorithm that can produce
30       hashes of different lengths.
31   Secure Shell (SSH): A program that provides Telnet-like remote
32       management capabilities; and FTP-like service; strongly encrypts
33       both usernames and passwords.
34   Secure Sockets Layer (SSL): The simplest VPN security standard to
35       implement; later renamed Transport Layer Security. Provides a secure
36       connection at the transport layer, protecting any applications above it
37       that are SSL/TLS-aware.
38   Semantics: In message exchange, the meaning of each message.
39   Sequence Number Field: In TCP, a header field that tells a TCP
40       segment’s order among the multiple TCP segments sent by one side.
41   Serial Transmission: Ethernet transmission over a single pair in each
42       direction.
43   Server Farm: Large groups of servers that work together to handle
44       applications.
45   Server Station: A station that provides service to client stations.
46   Server: A host that provides services to residential or corporate users.

                                                                     Chapter 1-36
 1   Service Band: A subdivision of the frequency spectrum, dedicated to a
 2        specific service such as FM radio or cellular telephone service.
 3   Service Control Point: A database of customer information, used in
 4        Signaling System 7.
 5   Service Level Agreement (SLA): A quality-of-service guarantee for
 6        throughput, availability, latency, error rate, and other matters.
 7   Service Pack: For Microsoft Windows, large cumulative updates that
 8        combine a number of individual updates.
 9   Session Key: Symmetric key that is used only during a single
10        communication session between two parties.
11   Session Layer: See OSI Session Layer.
12   Set: An SNMP command sent by the manager that tells the agent to
13        change a parameter on the managed device.
14   Set: When a flags field is given the value 1.
15   SETI@home: A project from the Search for Extraterrestrial Intelligence
16        (SETI), in which volunteers download SETI@home screen savers that
17        are really programs. These programs do work for the SETI@home
18        server when the volunteer computer is idle. Processing ends when the
19        user begins to do work.
20   Setup Fee: The cost of initial vendor installation for a system.
21   SFF: See Small Form Factor.
22   SHA: See Secure Hash Algorithm.
23   Shadow Zone (Dead Spot): A location where a receiver cannot receive
24        radio transmission, due to an obstruction blocking the direct path
25        between sender and receiver.
26   Shannon Equation: An equation by Claude Shannon (1938) that shows
27        that the maximum possible transmission speed (C) when sending data
28        through a channel is directly proportional to its bandwidth (B), and
29        depends to a lesser extent its signal-to-noise ratio (S/N): C = B Log2
30        (1 + S/N).
31   Share: Microsoft’s name for something that is shared, usually a directory
32        or a printer.
33   Shared Documents Folder (SharedDocs): In Windows XP, a directory
34        that is automatically shared. To share a file with other users on the
35        computer or on an attached network, the user can copy a file from
36        another directory to the Shared Document Folder.
37   Shared Static Key: A key that is used by all users in a system (shared)
38        that is not changed (static).
39   SharedDocs: See Shared Documents Folder.
40   SHDSL: See Super-High-Rate DSL.
41   Shopping Cart: A core e-commerce function that holds goods for the
42        buyer while he or she is shopping.
43   Signal Bandwidth: The range of frequencies in a signal, determined by
44        subtracting the lowest frequency from the highest frequency.
45   Signal: An information-carrying disturbance that propagates through a
46        transmission medium.

                                                                     Chapter 1-37
 1   Signaling Gateway: The device that sets up conversations between
 2       parties, maintains these conversations, ends them, provides billing
 3       information, and does other work.
 4   Signaling: In telephony, the controlling of calling, including setting up a
 5       path for a conversation through the transport core, maintaining and
 6       terminating the conversation path, collecting billing information, and
 7       handling other supervisory functions.
 8   Signal-to-Noise Ratio (SNR): The ratio of the signal strength to average
 9       noise strength; should be high in order for the signal to be effectively
10       received.
11   Signing: Encrypting something with the sender’s private key.
12   Simple File Sharing: In Windows XP, extremely weak security used on
13       files in Shared Documents folders. Simple File Sharing does not even
14       use a password; the only security is that people must know the
15       workgroup names to read and change files.
16   Simple Mail Transfer Protocol (SMTP): The protocol used to send a
17       message to a user’s outgoing mail host and from one mail host to
18       another; requires a complex series of interactions between the sender
19       and receiver before and after mail delivery.
20   Simple Network Management Protocol (SNMP): The protocol that
21       allows a general way to collect rich data from various managed
22       devices in a network.
23   Simple Object Access Protocol (SOAP): A standardized way for a Web
24       service to expose its methods on an interface to the outside world.
25   Single Point of Failure: When the failure in a single component of a
26       system can cause a system to fail or be seriously degraded.
27   Single Sign-On (SSO): Authentication in which a user can authenticate
28       himself or herself only once and then have access to all authorized
29       resources on all authorized systems.
30   Single-Mode Fiber: Optical fiber whose core is so thin (usually 8.3
31       microns in diameter) that only a single mode can propagate—the one
32       traveling straight along the axis.
33   SIP: One of the protocols used by signalling gateways.
34   Situation Analysis: The examination of a firm’s current situation, which
35       includes anticipation of how things will change in the future.
36   SLA: See Service Level Agreement.
37   Sliding Window Protocol: Flow control protocol that tells a receiver how
38       many more bytes it may transmit before receiving another
39       acknowledgement, which will give a longer transmission window.
40   Slot: A very brief time period used in Time Division Multiplexing; a
41       subdivision of a frame. Carries one sample for one circuit.
42   Small Form Factor (SFF): A variety of optical fiber connectors; smaller
43       than SC or ST connectors but unfortunately not standardized.
44   Small Office or Home Office (SOHO): A small-scale network for a
45       small office or home office.
46   SMTP: See Simple Mail Transfer Protocol.

                                                                      Chapter 1-38
 1   SNA: See Systems Network Architecture.
 2   Sneakernet: A joking reference to the practice of walking files around
 3       physically, instead of using a network for file sharing.
 4   SNMP: See Simple Network Management Protocol.
 5   SNR: See Signal-to-Noise Ratio.
 6   SOAP: See Simple Object Access Protocol.
 7   Social Engineering: Tricking people into doing something to get around
 8       security protections.
 9   Socket: The combination of an IP address and a port number, designating
10       a specific connection to a specific application on a specific host. It is
11       written as an IP address, a colon, and a port number, for instance
13   SOHO: See Small Office or Home Office.
14   Solid-Wire UTP: Type of UTP in which in which each of the eight wires
15       really is a single solid wire.
16   SONET: See Synchronous Optical Network.
17   Spam: Unsolicited commercial e-mail.
18   Spanning Tree Protocol (STP): See 802.1D Spanning Tree Protocol.
19   Speech Codec: See codec.
20   Spread Spectrum Transmission: A type of radio transmission that takes
21       the original signal and spreads the signal energy over a much broader
22       channel than would be used in normal radio transmission; used in
23       order to reduce propagation problems, not for security.
24   SSH: See Secure Shell.
25   SSL/TLS: See Secure Sockets Layer and Transport Layer Security.
26   SSL/TLS-Aware: Modified to work with SSL/TLS.
27   SSL: See Secure Sockets Layer.
28   SSO: See Single Sign-On.
29   ST Connector: A cylindrical optical fiber connector, sometimes called a
30       bayonet connector because of the manner in which it pushes into an
31       ST port and then twists to be locked in place.
32   Standard: A rule of operation that allows two hardware or software
33       processes to work together. Standards normally govern the exchange
34       of messages between two entities.
35   Standards Agency: An organization that creates and maintains standards.
36   Standards Architecture: A family of related standards that collectively
37       allows an application program on one machine on an internet to
38       communicate with another application program on another machine
39       on the internet.
40   Star Topology: A form of topology in which all wires in a network
41       connect to a single switch.
42   Start of Frame Delimiter Field: The second field of an Ethernet MAC
43       frame, which synchronizes the receiver’s clock to the sender’s clock
44       and then signals that the synchronization has ended.
45   Stateful Firewall: A firewall whose default behavior is to allow all
46       connections initiated by internal hosts but to block all connections

                                                                       Chapter 1-39
 1       initiated by external hosts. Only passes packets that are part of
 2       approved connections.
 3   Station: A computer that communicates over a network.
 4   STM: See Synchronous Transfer Mode.
 5   Store-and-Forward: Switching wherein the Ethernet switch waits until it
 6       has received the entire frame before sending the frame back out.
 7   STP: See 802.1D Spanning Tree Protocol.
 8   Strain Relief: Crimping the back of an RJ-45 connector into an RJ-45
 9       cord so that if the cord is pulled, it will not come out of the connector.
10   Stranded-Wire UTP: Type of UTP in which in which each of the eight
11       ―wires‖ really is a collection of wire strands.
12   Stripping Tool: Tool for stripping the sheath off the end of a UTP cord.
13   Strong Keys: Keys that are too long to be cracked by exhaustive key
14       search.
15   Subcarrier: A channel that is itself a subdivision of a broadband channel,
16       used to transmit frames in OFDM.
17   Subnet Part: The part of an IP address that specifies a particular subnet
18       within a network.
19   Subnet: A small network that is a subdivision of a large organization’s
20       network.
21   Super Client: ―Serverish‖ client in Gnutella that is always on, that has a
22       fixed IP address, that has many files to share, and that is connected to
23       several other super clients.
24   Super-High-Rate DSL (SHDSL): The next step in business DSL, which
25       can operate symmetrically over a single voice-grade twisted pair and
26       over a speed range of 384 kbps to 2.3 Mbps. It can also operate over
27       somewhat longer distances than HDSL2.
28   Surreptitiously: Done without someone’s knowledge, such as
29       surreptitious face recognition scanning.
30   SVC: See Switched Virtual Circuit.
31   Switch: A device that forwards frames within a single network.
32   Switched Virtual Circuit (SVC): A circuit between sites that is set up
33       just before a call and that lasts only for the duration of the call.
34   Switching Matrix: A switch component that connects input ports to
35       output ports.
36   Symmetric Key Encryption: Family of encryption methods in which the
37       two sides use the same key to encrypt messages to each other and to
38       decrypt incoming messages. In bidirectional communication, only a
39       single key is used.
40   SYN Bit: In TCP, the flags field that is set to indicate if the message is a
41       synchronization message.
42   Synchronous Digital Hierarchy (SDH): The European version of the
43       technology upon which the world is nearly standardized.
44   Synchronous Optical Network (SONET): The North American version
45       of the technology upon which the world is nearly standardized.
46   Synchronous Transfer Mode (STM): A number that indicates SDH

                                                                        Chapter 1-40
 1   speeds.
 2   Syntax: In message exchange, how messages are organized.
 3   Systems Administration: The management of a server.
 4   Systems Network Architecture (SNA): The standards architecture
 5       traditionally used by IBM mainframe computers.
 6   T568B: Wire color scheme for RJ-45 connectors; used most commonly in
 7       the United States.
 8   Tag Control Information: The second tag field, which contains a 12-bit
 9       VLAN ID that it sets to zero if VLANs are not being implemented. If
10       VLANs are being used, each VLAN will be assigned a different
11       VLAN ID.
12   Tag Field: One of the two fields added to an Ethernet MAC layer frame
13       by the 802.1Q standard.
14   Tag Protocol ID: The first tag field used in the Ethernet MAC layer
15       frame. The Tag Protocol ID has the two-octet hexadecimal value 81-
16       00, which indicates that the frame is tagged.
17   Tag: An indicator on an HTML file to show where the browser should
18       render graphics files, when it should play audio files, and so forth.
19   TCO: See Total Cost of Ownership.
20   TCP Segment: A TCP message.
21   TCP/IP: The Internet Engineering Tasks Force’s standards architecture;
22       dominant above the data link layer.
23   TCP: See Transmission Control Protocol.
24   TCPDUMP: The most popular freeware packet analysis program; the
25       Unix version.
26   TDM: See Time Division Multiplexing.
27   TDR: See Time Domain Reflectometry.
28   Telecommunications Closet: The location on each floor of a building
29       where cords coming up from the basement are connected to cords that
30       span out horizontally to telephones and computers on that floor.
31   Telephone Modem: A device used in telephony that converts digital data
32       into an analog signal that can transfer over the local loop.
33   Telnet: The simplest remote configuration tool; lacks encryption for
34       confidentiality.
35   Temporal Dispersion: Another name for modal dispersion.
36   Temporal Key Integrity Protocol (TKIP): A security process used by
37       802.11i, where each station has its own nonshared key after
38       authentication and where this key is changed frequently.
39   Terminal Crosstalk Interference: Crosstalk interference at the ends of a
40       UTP cord, where wires are untwisted to fit into the connector. To
41       control terminal crosstalk interference, wires should not be untwisted
42       more than a half inch to fit into connectors.
43   Termination Equipment: Equipment that connects a site’s internal
44       telephone system to the local exchange carrier.
45   Terrestrial: Earth-based.
46   Test Signals: Signal sent by a high-quality UTP tester through a UTP cord

                                                                    Chapter 1-41
 1       to check signal quality parameters.
 2   TFTP: See Trivial File Transfer Protocol.
 3   Third-Generation (3G): The newest generation of cellular telephony,
 4       able to carry data at much higher speeds than 2G systems.
 5   Three-Party Call: A call in which three people can take part in a
 6       conversation.
 7   Three-Tier Architecture: An architecture where processing is done in
 8       three places: on the client, on the application server, and on other
 9       servers.
10   Throughput: The transmission speed that users actually get. Usually
11       lower than a transmission system’s rated speed.
12   TIA/EIA-568: The standard that governs transmission media in the
13       United States.
14   Time Division Multiplexing (TDM): A technology used by telephone
15       carriers to provide reserved capacity on trunk lines between switches.
16       In TDM, time is first divided into frames, each of which are divided
17       into slots; a circuit is given the same slot in every frame.
18   Time Domain Reflectometry (TDR): Sending a signal in a UTP cord and
19       recording reflections; can give the length of the cord or the location of
20       a propagation problem in the cord.
21   Time to Live (TTL): The field added to a packet and given a value by a
22       source host, usually between 64 and 128. Each router along the way
23       decrements the TTL field by one. A router decrementing the TTL to
24       zero will discard the packet; this prevents misaddressed packets from
25       circulated endlessly among packet switches in search of their
26       nonexistent destinations.
27   TKIP: See Temporal Key Integrity Protocol.
28   TLS: See Transport Layer Security.
29   Toll Call: Long-distance call pricing in which the price depends on
30       distance and duration.
31   Toll-Free Number Service: Service in which anyone can call into a
32       company, usually without being charged. Area codes are 800, 888,
33       877, 866, and 855.
34   Top-Level Domain: The second level of a DNS hierarchy, which
35       categorizes the domain by organization type (e.g., .com, .net, .edu,
36       .biz, .info) or by country (e.g., .uk, .ca, .ie, .au, .jp, .ch).
37   Topology: The way in which nodes are linked together by transmission
38       lines.
39   TOS: See Type of Service.
40   Total Cost of Ownership (TCO): The total cost of an entire system over
41       its expected lifespan.
42   Total Purchase Cost of Network Products: The initial purchase price of
43       a fully configured system.
44   Tracert (tracert): A Windows program that shows latencies to every
45       router along a route and to the destination host.
46   Trailer: The part of a message that comes after the data field.

                                                                       Chapter 1-42
 1   Transaction Processing: Processing involving simple, highly structured,
 2       and high-volume interactions.
 3   Transceiver: A transmitter/receiver.
 4   Transfer Syntax: The syntax used by two presentation layer processes to
 5       communicate, which may or may not be quite different than either of
 6       their internal methods of formatting information.
 7   Transmission Control Protocol (TCP): The most common TCP/IP
 8       protocol at the transport layer. Connection-oriented and reliable.
 9   Transparently: Without having a need to implement modifications.
10   Transport Core: The switches and transmission lines that carry voice
11   signals from one subscriber’s access line and delivering them to another
12   customer’s access line.
13   Transport Layer Security (TLS): The simplest VPN security standard to
14       implement; originally named Secure Sockets Layer. Provides a secure
15       connection at the transport layer, protecting any applications above it
16       that are SSL/TLS-aware.
17   Transport Layer: The layer that governs communication between two
18       hosts; Layer 4 in both OSI and TCP/IP.
19   Transport Mode: One of IPsec’s two modes of operation, in which the
20       two computers that are communicating implement IPsec. Transport
21       mode gives strong end-to-end security between the computers, but it
22       requires IPsec configuration and a digital certificate on all machines.
23   Transport: In telephony, transmission; taking voice signals from one
24       subscriber’s access line and delivering them to another customer’s
25       access line.
26   Traps: The type of message that an agent sends if it detects a condition
27       that it thinks the manager should know about.
28   Triple DES (3DES): Symmetric key encryption method in which a
29       message is encrypted three times with DES. If done with two or three
30       different keys, offers strong security. However, it is processing
31       intensive.
32   Trivial File Transfer Protocol (TFTP): A protocol used on switches and
33       routers to download configuration information; has no security.
34   Trojan Horse: A program that looks like an ordinary system file, but
35       continues to exploit the user indefinitely.
36   Trunk Line: A type of transmission line that links switches to each other,
37       routers to each other, or a router to a switch.
38   Trunking: See Link Aggregation.
39   TTL: See Time to Live.
40   Tunnel Mode: One of IPsec’s two modes of operation, in which the IPsec
41       connection extends only between IPsec gateways at the two sites.
42       Tunnel mode provides no protection within sites, but it offers
43       transparent security.
44   Twisted-Pair Wiring: Wiring in which each pair’s wires are twisted
45       around each other several times per inch, reducing EMI.
46   Type of Service (TOS): IPv4 header field that designates the type of

                                                                     Chapter 1-43
 1       service a certain packet should receive.
 2   U: The standard unit for measuring the height of switches. One U is 1.75
 3       inches (4.4 cm) in height. Most switches, although not all, are
 4       multiples of U.
 5   UDDI Green Pages: The UDDI search option that allows companies to
 6       understand how to interact with specific Web services. Green pages
 7       specify the interfaces on which a Web service will respond, the
 8       methods it will accept, and the properties that can be changed or
 9       returned.
10   UDDI White Pages: The UDDI search option that allows users to search
11       for Web services by name, much like telephone white pages.
12   UDDI Yellow Pages: The UDDI search option that allows users to search
13       for Web services by function, such as accounting, much like
14       telephone yellow pages.
15   UDDI: See Universal Description, Discovery, and Integration.
16   Unicast: To send a frame to only one other station.
17   UNICODE: The standard that allows characters of all languages to be
18       represented.
19   Universal Description, Discovery, and Integration (UDDI): A protocol
20       that is a distributed database that helps users find appropriate Web
21       services.
22   Unix: A network operating system used by all workstation servers. Linux
23       is a Unix version used on PCs.
24   Unlicensed Radio Band: A radio band that does not require each station
25       using it to have a license.
26   Unreliable: (Of a protocol) not doing error correction.
27   Unshielded Twisted Pair (UTP): Network cord that contains four twisted
28       pairs of wire within a sheath. Each wire is covered with insulation.
29   Update: To download and apply patches to fix a system.
30   Usage Policy: A company policy for who may use various tools and how
31       they may use them.
32   Username: An alias that signifies the account that the account holder will
33       be using.
34   UTP: See Unshielded Twisted Pair.
35   Validate: To test the accuracy of a network simulation model by
36       comparing its performance with that of the real network. If the
37       predicted results match the actual results, the model is validated.
38   Variable-Length Subnet Mask (VLSM): A mask that allows subnets to
39       be of different sizes.
40   VCI: See Virtual Channel Identifier.
41   Verifier: The party requiring the applicant to prove his or her identity.
42   Vertical Riser: Space between the floors of a building that telephone and
43       data cabling go through to get to the building’s upper floor.
44   Viral Networking: Networking in which the user’s PC connects to one or
45       a few other user PCs, which each connect to several other user PCs.
46       When the user’s PC first connects, it sends an initiation message to

                                                                    Chapter 1-44
 1       introduce itself via viral networking. Subsequent search queries sent
 2       by the user also are passed virally to all computers reachable within a
 3       few hops; used in Gnutella.
 4   Virtual Channel Identifier (VCI): One of the two parts of ATM virtual
 5       circuit numbers.
 6   Virtual Channel: In ATM, an individual connection within a virtual path.
 7   Virtual Circuit: A transmission path between two sites or devices;
 8       selected before transmission begins.
 9   Virtual LAN (VLAN): A closed collection of servers and the clients they
10       serve. Broadcast signals go only to computers in the same VLAN.
11   Virtual Path Identifier (VPI): One of the two parts of ATM virtual
12       circuit numbers.
13   Virtual Path: In ATM, a group of connections going between two sites.
14   Virtual Private Network (VPN): A network that uses the Internet with
15       added security for data transmission.
16   Virtual Private Network (VPN): Transmission over the Internet with
17       added security.
18   Virus Definitions Database: A database used by antivirus programs to
19       identify viruses. As new viruses are found, the virus definitions
20       database must be updated.
21   Virus: A piece of executable code that attaches itself to programs or data
22       files. When the program is executed or the data file opened, the virus
23       spreads to other programs or data files.
24   VLAN: See Virtual LAN.
25   VLSM: See Variable-Length Subnet Mask.
26   Voice Mail: A service that allows people to leave a message if the user
27       does not answer his or her phone.
28   Voice-Grade: Wire of a quality useful for transmitting voice signals in the
29       PSTN.
30   VPI: See Virtual Path Identifier.
31   VPN: See Virtual Private Network.
32   Vulnerability Testing: Testing after protections have been configured, in
33       which a company or a consultant attacks protections in the way a
34       determined attacker would and notes which attacks that should have
35       been stopped actually succeeded.
36   Vulnerability: A security weakness found in software.
37   WAN: See Wide Area Network.
38   WATS: See Wide Area Telephone Service.
39   Wavelength Division Multiplexing: Using signaling equipment to
40       transmit several light sources at slightly different wavelengths, thus
41       adding signal capacity at the cost of using slightly more expensive
42       signaling equipment but without incurring the high cost of laying new
43       fiber.
44   Wavelength: The physical distance between comparable points (e.g., from
45       peak to peak) in successive cycles of a wave.
46   WDM: See Wavelength Division Multiplexing.

                                                                     Chapter 1-45
 1   Weak Keys: Keys that are shot enough to be cracked by exhaustive key
 2      search.
 3   Web Service: A way to send processing requests to program (object) on
 4      another machine. The object has an interface to the outside world and
 5      methods that it is willing to undertake. Messages are sent in SOAP
 6      format.
 7   Web-Enabled: Client/server processing applications that use ordinary
 8      browsers as client programs.
 9   Webmail: Web-enabled e-mail. User needs only a browser to send and
10      read e-mail.
11   Well-Known Port Number: Standard port number of a major application
12      that is usually (but not always) used. For example, the well-known
13      TCP port number for HTTP is 80.
14   WEP: See Wired Equivalent Privacy.
15   Wide Area Network (WAN): A network that links different sites
16      together.
17   Wide Area Network (WAN): A network that links different sites
18      together.
19   Wide Area Telephone Service (WATS): Service that allows a company
20      to place outgoing long-distance calls at per-minute prices lower than
21      those of directly dialed calls.
22   WiMAX: Broadband wireless access method. Standardized as 802.16.
23   Window Size Field: TCP header field that is used for flow control. It tells
24      the station that receives the segment how many more octets that
25      station may transmit before getting another acknowledgement
26      message that will allow it to send more octets.
27   Windows Internet Name Service (WINS): The system required by
28      Windows clients and servers before Windows 2000 server to provide
29      IP address for host names.
30   WinDUMP: The most popular freeware packet analysis program; the
31      Windows version.
32   Winipcfg (winipcfg): A command used to find information about one’s
33      own computer; used in older versions of windows.
34   WINS: See Windows Internet Name Service.
35   Wired Equivalent Privacy (WEP): A weak security mechanism for
36      802.11.
37   Wireless Ethernet: Sometimes used as another name for 802.11.
38   Wireless LAN (WLAN): A local area network that uses radio (or rarely,
39      infrared) transmission instead of cabling to connect devices.
40   Wireless Networking: Networking that uses radio transmission instead of
41      wires to connect devices.
42   Wireless NIC: 802.11 network interface card.
43   Wireless Protected Access (WPA): 802.11 security method created as a
44      stopgap between WEP and 802.11i.
45   WLAN: See Wireless LAN.
46   Work-Around: A process of making manual changes to eliminate a

                                                                     Chapter 1-46
 1       vulnerability instead of just installing a software patch.
 2   Workgroup Name: To create a workgroup, all PCs in the workgroup are
 3       assigned the same workgroup name. They will find each other
 4       automatically.
 5   Workgroup Switch: A switch to which stations connect directly.
 6   Workgroup: A logical network. On a physical network, only PCs in the
 7       same workgroup can communicate.
 8   Working Group: A specific subgroup of the 802 Committee, in charge of
 9       developing a specific group of standards. For instance, the 802.3
10       Working Group creates Ethernet standards.
11   Workstation Server: The most popular type of large dedicated server;
12       runs the Unix operating system. It uses custom-designed
13       microprocessors and runs the Unix operating system.
14   Worm: An attack program that propagates on its own by seeking out other
15       computers, jumping to them, and installing itself.
16   WPA: See Wireless Protected Access.
17   Write: A Microsoft Windows Server permission that allows an account
18       owner to change the contents of files in the directory.
19   X.509: The main standard for digital certificates.
20   Zero-Day Exploit: An exploit that takes advantage of vulnerabilities that
21       have not previously been discovered or for which updates have not
22       been created.

                                                                   Chapter 1-47

To top