Glossary of Terms Flashcards
1
Q
10Base2
A
The last true bus-standard network where nodes connected to a common, shared length of coaxial cable
2
Q
10BaseFL
A
Fiber-optic implementation of Ethernet that runs at 10 Mbps using baseband signaling. Maximum segment length is 2 km
3
Q
10BaseT
A
An Ethernet LAN designed to run on UTP cabling. Runs at 10 Mbps and uses baseband signaling. Maximum length for the cabling between the NIC and the hub (or the switch, the repeater, and so forth) is 100 m.
4
Q
10GBaseER/10GBaseEW
A
A 10 GbE standard using 1550-nm single-mode fiber. Maximum cable length up to 40 km
5
Q
10GBaseLR/10GBaseLW
A
A 10 GbE standard using 1310-nm single-mode fiber. Maximum cable length up to 10 km.
6
Q
10GBaseSR/10GBaseSW
A
A 10 GbE standard using 850-nm multimode fiber. Maximum cable length up to 300 m.
7
Q
10GBaseT
A
A 10 GbE standard designed to run on CAT 6a UTP cabling. Maximum cable length of 100 m.
8
Q
10 Gigabit Ethernet (10 GbE)
A
Currently (2015) the fastest Ethernet designation available, with a number of fiber-optic and copper standards.
9
Q
100BaseFX
A
An Ethernet LAN designed to run on fiber-optic cabling. Runs at 100 Mbps and uses baseband signaling. Maximum cable length is 400 m for half-duplex and 2 km for full-duplex
10
Q
100BaseT
A
An Ethernet LAN designed to run on UTP cabling. Runs at 100 Mbps, uses baseband signaling, and uses two pairs of wires on CAT 5 or better cabling.
11
Q
100BaseT4
A
An Ethernet LAN designed to run on UTP cabling. Runs at 100 Mbps and uses four-pair CAT 3 or better cabling. Made obsolete by 100BaseT.
12
Q
100BaseTX
A
The technically accurate but little-used name for 100BaseT
13
Q
110 Block
A
Also known as a 110-punchdown block, a connection gridwork used to link UTP and STP cables behind an RJ-45 patch panel.
14
Q
110-Punchdown Block
A
The most common connection used on the back of an RJ-45 jack and patch panels.
15
Q
802 Committee
A
The IEEE committee responsible for all Ethernet standards.
16
Q
802.1X
A
A port-authentication network access control mechanism for networks.
17
Q
802.3 (Ethernet)
A
See Ethernet: Name coined by Xerox for the first standard of network cabling and protocols. Ethernet is based on a bus topology. The IEEE 802.3 subcommittee defines the current Ethernet specifications.
18
Q
802.3ab
A
The IEEE standard for 1000BaseT.
19
Q
802.3z
A
The umbrella IEEE standard for all versions of Gigabit Ethernet other than 1000BaseT.
20
Q
802.11
A
See IEEE 802.11.
21
Q
802.11a
A
A wireless standard that operates in the frequency range of 5 GHz and offers throughput of up to 54 Mbps.
22
Q
802.11a-ht
A
802.11a-ht, and the corresponding 802.11g-ht standard, are technical terms for mixed mode 802.11a/802.11g operation. In mixed mode, both technologies are simultaneously supported
23
Q
802.11b
A
The first popular wireless standard, operates in the frequency range of 2.4 GHz and offers throughput of up to 11 Mbps.
24
Q
802.11g
A
Currently (2015) the wireless standard with the widest use, operates on the 2.4-GHz band with a maximum throughput of 54 Mbps
25
802.11g-ht
802.11g-ht, and the corresponding 802.11a-ht standard, are technical terms for mixed mode 802.11a/802.11g operation. In mixed mode, both technologies are simultaneously supported
26
802.11i
A wireless standard that added security features.
27
802.11n
An updated 802.11 standard that increases transfer speeds and adds support for multiple in/multiple out (MIMO) by using multiple antennas. 802.11n can operate on either the 2.4- or 5-GHz frequency band and has a maximum throughput of 400 Mbps.
28
802.16
A wireless standard (also known as WiMAX) with a range of up to 30 miles.
29
1000BaseCX
A Gigabit Ethernet standard using unique copper cabling, with a 25-m maximum cable distance.
30
1000BaseLX
A Gigabit Ethernet standard using single-mode fiber cabling, with a 5-km maximum cable distance.
31
1000BaseSX
A Gigabit Ethernet standard using multimode fiber cabling, with a 220- to 500-m maximum cable distance
32
1000BaseT
A Gigabit Ethernet standard using CAT 5e/6 UTP cabling, with a 100-m maximum cable distance
33
1000BaseTX
Short-lived gigabit-over-UTP standard from TIA/EIA. Considered a competitor to 1000BaseT, it was simpler to implement but required the use of CAT 6 cable
34
1000BaseX
An umbrella Gigabit Ethernet standard. Also known as 802.3z. Comprises all Gigabit standards with the exception of 1000BaseT, which is under the 802.3ab standard.
35
A Records
A list of the IP addresses and names of all the systems on a DNS server domain.
36
AAA
(Authentication, Authorization, and Accounting) A security philosophy wherein a computer trying to connect to a network must first present some form of credential in order to be authenticated and then must have limitable permissions within the network. The authenticating server should also record session information about the client.
37
Acceptable Use Policy
A document that defines what a person may and may not do on an organization’s computers and networks.
38
Access Control
All-encompassing term that defines the degree of permission granted to use a particular resource. That resource may be anything from a switch port to a particular file to a physical door within a building.
39
A clearly defined list of permissions that specifies what actions an authenticated user may perform on a shared resource
40
Access Control Server (ACS)
Cisco program/process/server that makes the decision to admit or deny a node based on posture assessment. From there, the ACS directs the edge access device to allow a connection or to implement a denial or redirect.
41
Access Port
Regular port in a switch that has been configured as part of a VLAN. Access ports are ports that hosts connect to. They are the opposite of a trunk port, which is only connected to a trunk port on another switch.
42
Active Directory
A form of directory service used in networks with Windows servers. Creates an organization of related computers that share one or more Windows domains.
43
Activity Light
An LED on a NIC, hub, or switch that blinks rapidly to show data transfers over the network
44
Ad Hoc Mode
A wireless networking mode where each node is in direct contact with every other node in a decentralized free-for-all. Ad hoc mode is similar to the mesh topology
45
Address Resolution Protocol (ARP)
A protocol in the TCP/IP suite used with the command-line utility of the same name to determine the MAC address that corresponds to a particular IP address.
Used to resolve ip addresses into MAC addresses
46
Administrative Accounts
pecialized user accounts that have been granted sufficient access rights and authority to manage specified administrative tasks. Some administrative accounts exist as a default of the system and have all authority throughout the system. Others must be explicitly assigned the necessary powers to administer given resources.
47
ADSL (Asymmetric Digital Subscriber Line)
48
Advanced Encryption Standard (AES)
A block cipher created in the late 1990s that uses a 128-bit block size and a 128-, 192-, or 256-bit key size. Practically uncrackable.
49
Adware
A program that monitors the types of Web sites you frequent and uses that information to generate targeted advertisements, usually pop-up windows
50
Agent
In terms of posture assessment, refers to software that runs within a client and reports the client’s security characteristics to an access control server to be approved or denied entry to a system.
51
Aggregation
A router hierarchy in which every router underneath a higher router always uses a subnet of that router’s existing routes
52
Air Gap
The act of physically separating a network from every other network.
53
Amplification
The aspect of a DoS attack that makes a server do a lot of processing and responding.
54
Angled Physical Contact (APC)
Fiber-optic connector that makes physical contact between two fiber-optic cables. It specifies an 8-degree angle to the curved end, lowering signal loss. APC connectors have less connection degradation from multiple insertions compared to other connectors.
55
Anti-Malware Program
Software that attempts to block several types of threats to a client including viruses, Trojan horses, worms, and other unapproved software installation and execution.
56
Antivirus
Software that attempts to prevent viruses from installing or executing on a client. Some antivirus software may also attempt to remove the virus or eradicate the effects of a virus after an infection.
57
Anycast
A method of addressing groups of computers as though they were a single computer. Anycasting starts by giving a number of computers (or clusters of computers) the same IP address. Advanced routers then send incoming packets to the closest of the computers.
58
Application Layer
59
Application/Context Aware
Advanced feature of some stateful firewalls where the content of the data is inspected to ensure it comes from, or is destined for, an appropriate application. Context-aware firewalls look both deeply and more broadly to ensure that the data content and other aspects of the packet are appropriate to the data transfer being conducted. Packets that fall outside these awareness criteria are denied by the firewall
60
Application Programming Interface (API)
Shared functions, subroutines, and libraries that allow programs on a machine to communicate with the OS and other programs.
61
Approval Process
One or more decision makers consider a proposed change and the impact of the change, including funding. If the change, the impact, and the funding are acceptable, the change is permitted.
62
Archive
The creation and storage of retrievable copies of electronic data for legal and functional purposes.
63
Area ID
Address assigned to routers in an OSPF network to prevent flooding beyond the routers in that particular network. See also Open Shortest Path First (OSPF).
64
Groups of logically associated OSPF routers designed to maximize routing efficiency while keeping the amount of broadcast traffic well managed. Areas are assigned a 32-bit value that manifests as an integer between 0 and 4294967295 or can take a form similar to an IP address, for example, “0.0.0.0.”
65
ARP
66
ARP Cache Poisoning
A man-in-the-middle attack, where the attacker associates his MAC address with someone else’s IP address (almost always the router), so all traffic will be sent to him first. The attacker sends out unsolicited ARPs, which can either be requests or replies
67
arping
A command used to discover hosts on a network, similar to ping, but that relies on ARP rather than ICMP. The arping command won’t cross any routers, so it will only work within a broadcast domain. See also Address Resolution Protocol (ARP) and ping.
68
Asset Management
Managing each aspect of a network, from documentation to performance to hardware.
69
Asymmetric Digital Subscriber Line (ADSL)
A fully digital, dedicated connection to the telephone system that provides download speeds of up to 9 Mbps and upload speeds of up to 1 Mbps.
70
Asymmetric-Key Algorithm
An encryption method in which the key used to encrypt a message and the key used to decrypt it are different, or asymmetrical
71
Asynchronous Transfer Mode (ATM)
A network technology that runs at speeds between 25 and 622 Mbps using fiber-optic cabling or CAT 5 or better UTP
72
Attenuation
The degradation of signal over distance for a networking cable.
73
Authentication
A process that proves good data traffic truly came from where it says it originated by verifying the sending and receiving users and computers
74
Authentication Server (AS)
In Kerberos, a system that hands out Ticket-Granting Tickets to clients after comparing the client hash to its own
75
Authoritative DNS Servers
DNS servers that hold the IP addresses and names of systems for a particular domain or domains in special storage areas called forward lookup zones. They also have reverse lookup zones.
76
Authoritative Name Servers
Another name for authoritative DNS servers. DNS servers that hold the IP addresses and names of systems for a particular domain or domains in special storage areas called forward lookup zones. They also have reverse lookup zones.
77
Authorization
A step in the AAA philosophy during which a client’s permissions are decided upon
78
Automatic Private IP Addressing (APIPA
A networking feature in operating systems that enables DHCP clients to self-configure an IP address and subnet mask automatically when a DHCP server isn’t available
79
Autonomous System (AS)
One or more networks that are governed by a single protocol, which provides routing for the Internet backbone
80
Backup Designated Router (BDR)
A second router set to take over if the designated router fails.
81
Bandwidth
A piece of the spectrum occupied by some form of signal, whether it is television, voice, fax data, and so forth. Signals require a certain size and location of bandwidth to be transmitted. The higher the bandwidth, the faster the signal transmission, thus allowing for a more complex signal such as audio or video. Because bandwidth is a limited space, when one user is occupying it, others must wait their turn. Bandwidth is also the capacity of a network to transmit a given amount of data during a given period.
82
Bandwidth Saturation
When the frequency of a band is filled to capacity due to the large number of devices using the same bandwidth.
83
Banner Grabbing
When a malicious user gains access to an open port and uses it to probe a host to gain information and access, as well as learn details about running services
84
Baseband
Digital signaling that has only one signal (a single signal) on the cable at a time. The signals must be in one of three states: one, zero, or idle
85
Baseline
Static image of a system’s (or network’s) performance when all elements are known to be working properly
86
Basic NAT
A simple form of NAT that translates a computer’s private or internal IP address to a global IP address on a one-to-one basis
87
Basic Rate Interface (BRI)
The basic ISDN configuration, which consists of two B channels (which can carry voice or data at a rate of 64 Kbps) and one D channel (which carries setup and configuration information, as well as data, at 16 Kbps)
88
Basic Service Set (BSS
In wireless networking, a single access point servicing a given area
89
Basic Service Set Identifier (BSSID
Naming scheme in wireless networks
90
Baud
One analog cycle on a telephone line
91
Baud Rate
The number of bauds per second. In the early days of telephone data transmission, the baud rate was often analogous to bits per second. Due to advanced modulation of baud cycles as well as data compression, this is no longer true.
92
Bearer Channel (B Channel)
A type of ISDN channel that carries data and voice information using standard DS0 channels at 64 Kbps.
93
Biometric
Human physical characteristic that can be measured and saved to be compared as authentication in granting the user access to a network or resource. Common biometrics include fingerprints, facial scans, retinal scans, voice pattern recognition, and others.
94
Bit Error Rate Test (BERT)
An end-to-end test that verifies a T-carrier connection
95
Block
Access that is denied through to or from a resource. A block may be implemented in a firewall, access control server, or other secure gateway
96
Blocks
Contiguous ranges of IP addresses that are assigned to organizations and end users by IANA. Also called network blocks.
97
Block Cipher
An encryption algorithm in which data is encrypted in “chunks” of a certain length at a time. Popular in wired networks
98
BNC Connector
A connector used for 10Base2 coaxial cable. All BNC connectors have to be locked into place by turning the locking ring 90 degrees
99
BNC Coupler
Passive connector used to join two segments of coaxial cables that are terminated with BNC connectors
100
Bonding
Two or more NICs in a system working together to act as a single NIC to increase performance
101
Bootstrap Protocol (BOOTP)
A component of TCP/IP that allows computers to discover and receive an IP address from a DHCP server prior to booting the OS. Other items that may be discovered during the BOOTP process are the IP address of the default gateway for the subnet and the IP addresses of any name servers.
102
Border Gateway Protocol (BGP-4)
An exterior gateway routing protocol that enables groups of routers to share routing information so that efficient, loop-free routes can be established
103
Botnet
A group of computers under the control of one operator, used for malicious purposes.
104
Bps (Bits Per Second)
A measurement of how fast data is moved across a transmission medium. A Gigabit Ethernet connection moves 1,000,000,000 bps
105
Bridge
A device that connects two networks and passes traffic between them based only on the node address, so that traffic between nodes on one network does not appear on the other network. For example, an Ethernet bridge only looks at the MAC address. Bridges filter and forward frames based on MAC addresses and operate at Layer 2 (Data Link layer) of the OSI seven-layer model.
106
Bridge Loop
A negative situation in which bridging devices (usually switches) are installed in a loop configuration, causing frames to loop continuously. Switches using Spanning Tree Protocol (STP) prevent bridge loops by automatically turning off looping ports
107
Bridged Connection
An early type of DSL connection that made the DSL line function the same as if you snapped an Ethernet cable into your NIC
108
Bridging Loop
A physical wiring of a circuitous path between two or more switches, causing frames to loop continuously. Implementing Spanning Tree Protocol (STP) in these devices will discover and block looped paths
109
BYOD
Bring Your Own Device A trend wherein users bring their own network-enabled devices to the work environment. These cell phones, tablets, notebooks, and other mobile devices must be easily and securely integrated and released from corporate network environments using on-boarding and off-boarding technologies.
110
Broadband
Analog signaling that sends multiple signals over the cable at the same time. The best example of broadband signaling is cable television. The zero, one, and idle states exist on multiple channels on the same cable
111
Broadcast
A frame or packet addressed to all machines, almost always limited to a broadcast domain
112
Broadcast Address
The address a NIC attaches to a frame when it wants every other NIC on the network to read it. In TCP/IP, the general broadcast address is 255.255.255.255. In Ethernet, the broadcast MAC address is FF-FF-FF-FF-FF-FF.
113
Broadcast Domain
A network of computers that will hear each other’s broadcasts. The older term collision domain is the same but rarely used today
114
Broadcast Storm
The result of one or more devices sending a nonstop flurry of broadcast frames on the network.
115
Brute Force
A type of attack wherein every permutation of some form of data is tried in an attempt to discover protected information. Most commonly used on password cracking.
116
Bus Topology
A network topology that uses a single bus cable that connects all of the computers in a line. Bus topology networks must be terminated to prevent signal reflection.
117
BCP
Business Continuity Planning The process of defining the steps to be taken in the event of a physical corporate crisis to continue operations. Includes the creation of documents to specify facilities, equipment, resources, personnel, and their roles.
118
Butt Set
Device that can tap into a 66- or 110-punchdown block to see if a particular line is working
119
Byte
Eight contiguous bits, the fundamental data unit of personal computers. Storing the equivalent of one character, the byte is also the basic unit of measurement for computer storage. Bytes are counted in powers of two.
120
CAB Files
Short for “cabinet files.” These files are compressed and most commonly used during Microsoft operating system installation to store many smaller files, such as device drivers.
121
Cable Certifier
A very powerful cable testing device used by professional installers to test the electrical characteristics of a cable and then generate a certification report, proving that cable runs pass TIA/EIA standards
122
Cable Drop
Location where the cable comes out of the wall at the workstation location
123
Cable Modem
A bridge device that interconnects the cable company’s DOCSIS service to the user’s Ethernet network. In most locations, the cable modem is the demarc
124
Cable Stripper
Device that enables the creation of UTP cables
125
Cable Tester
A generic name for a device that tests cables. Some common tests are continuity, electrical shorts, crossed wires, or other electrical characteristics.
126
Cable Tray
A device for organizing cable runs in a drop ceiling
127
Cache
A special area of RAM that stores frequently accessed data. In a network there are a number of applications that take advantage of cache in some way
128
Cache-Only DNS Servers (Caching-Only DNS Servers)
DNS servers that do not have any forward lookup zones. They resolve names of systems on the Internet for the network, but are not responsible for telling other DNS servers the names of any clients.
129
Cached Lookup
The list kept by a DNS server of IP addresses it has already resolved, so it won’t have to re-resolve an FQDN it has already checked
130
Caching Engine
A server dedicated to storing cache information on your network. These servers can reduce overall network traffic dramatically
131
CAN
Campus Area Network A network installed in a medium-sized space spanning multiple buildings
132
CNAME
Canonical Name Less common type of DNS record that acts as a computer’s alias.
133
Capture File
A file in which the collected packets from a packet sniffer program are stored.
134
CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance
135
CSMA/CD
Carrier Sense Multiple Access with Collision Detection
136
CAT 3
Category 3 wire, a TIA/EIA standard for UTP wiring that can operate at up to 16 Mbps
137
CAT 4
Category 4 wire, a TIA/EIA standard for UTP wiring that can operate at up to 20 Mbps. This wire is not widely used, except in older Token Ring networks
138
CAT 5
Category 5 wire, a TIA/EIA standard for UTP wiring that can operate at up to 100 Mbps
139
CAT 5e
Category 5e wire, a TIA/EIA standard for UTP wiring with improved support for 100 Mbps using two pairs and support for 1000 Mbps using four pairs
140
CAT 6
Category 6 wire, a TIA/EIA standard for UTP wiring with improved support for 1000 Mbps
141
Category (CAT) Rating
A grade assigned to cable to help network installers get the right cable for the right network technology. CAT ratings are officially rated in megahertz (MHz), indicating the highest-frequency bandwidth the cable can handle.
142
CCITT
(Comité Consutatif Internationale Téléphonique et Télégraphique)
European standards body that established the V standards for modems.
143
Central Office
Building that houses local exchanges and a location where individual voice circuits come together
144
Certificate
A public encryption key signed with the digital signature from a trusted third party called a certificate authority (CA). This key serves to validate the identity of its holder when that person or company sends data to other parties
145
Certifier
A device that tests a cable to ensure that it can handle its rated amount of capacity
146
Chain of Custody
A document used to track the collection, handling, and transfer of evidence
147
CHAP
Challenge Handshake Authentication Protocol A remote access authentication protocol. It has the serving system challenge the remote client, which must provide an encrypted password
148
Change Management
The process of initiating, approving, funding, implementing, and documenting significant changes to the network
149
Change Management Documentation
A set of documents that defines procedures for changes to the network
150
Change Management Team
Personnel who collect change requests, evaluate the change, work with decision makers for approval, plan and implement approved changes, and document the changes
151
Change Request
A formal or informal document suggesting a modification to some aspect of the network or computing environment
152
Channel
A portion of the wireless spectrum on which a particular wireless network operates. Setting wireless networks to different channels enables separation of the networks.
153
Channel Bonding
Wireless technology that enables wireless access points (WAPs) to use two channels for transmission
154
CSU/DSU
CSU/DSU (Channel Service Unit/Data Service Unit)
155
Checksum
A simple error-detection method that adds a numerical value to each data packet, based on the number of data bits in the packet. The receiving node applies the same formula to the data and verifies that the numerical value is the same; if not, the data has been corrupted and must be re-sent
156
Cipher
A series of complex and hard-to-reverse mathematics run on a string of ones and zeroes in order to make a new set of seemingly meaningless ones and zeroes.
157
Cipher Lock
A door unlocking system that uses a door handle, a latch, and a sequence of mechanical push buttons
158
Ciphertext
The output when cleartext is run through a cipher algorithm using a key
159
Circuit Switching
The process for connecting two phones together on one circuit
160
Cladding
The part of a fiber-optic cable that makes the light reflect down the fiber
161
CoS
Class of Service A prioritization value used to apply to services, ports, or whatever a quality of service (QoS) device might use
162
Class License
Contiguous chunk of IP addresses passed out by the Internet Assigned Numbers Authority (IANA)
163
CIDR
Classless Inter-Domain Routing Method of categorizing IP addresses in order to distribute them. See also Subnetting
164
Classless Subnet
A subnet that does not fall into the common categories such as Class A, Class B, and Class C
165
Client
A computer program that uses the services of another computer program; software that extracts information from a server. Your autodial phone is a client, and the phone company is its server. Also, a machine that accesses shared resources on a server.
166
Client-to-Site
A type of VPN connection where a single computer logs into a remote network and becomes, for all intents and purposes, a member of that network
167
Client/Server
A relationship in which client software obtains services from a server on behalf of a user.
168
Client/Server Application
An application that performs some or all of its processing on an application server rather than on the client. The client usually only receives the result of the processing
169
Client/Server Network
A network that has dedicated server machines and client machines
170
Closed-Circuit Television (CCTV)
A self-contained, closed system in which video cameras feed their signal to specific, dedicated monitors and storage devices
171
Cloud Computing
Using the Internet to store files and run applications. For example, Google Docs is a cloud computing application that enables you to run productivity applications over the Internet from your Web browser.
172
Cloud/Server Based
Remote storage and access of software, especially anti-malware software, where it can be singularly updated. This central storage allows users to access and run current versions of software easily, with the disadvantage of it not running automatically on the local client. The client must initiate access to and launching of the software
173
Coaxial Cable
A type of cable that contains a central conductor wire surrounded by an insulating material, which in turn is surrounded by a braided metal shield. It is called coaxial because the center wire and the braided metal shield share a common axis or centerline
174
Cold Site
A location that consists of a building, facilities, desks, toilets, parking, and everything that a business needs except computers
175
Collision
The result of two nodes transmitting at the same time on a multiple access network such as Ethernet. Both frames may be lost or partial frames may result
176
Collision Light
A light on some older NICs that flickers when a network collision is detected.
177
CIFS
Common Internet File System The protocol that NetBIOS used to share folders and printers. Still very common, even on UNIX/Linux systems
178
Community Cloud
A private cloud paid for and used by more than one organization
179
Complete Algorithm
A cipher and the methods used to implement that cipher
180
Computer Forensics
The science of gathering, preserving, and presenting evidence stored on a computer or any form of digital media that is presentable in a court of law
181
Concentrator
A device that brings together at a common center connections to a particular kind of network (such as Ethernet) and implements that network internally
182
Configuration Management
A set of documents, policies, and procedures designed to help you maintain and update your network in a logical, orderly fashion
183
Configuration Management Documentation
Documents that define the configuration of a network. These would include wiring diagrams, network diagrams, baselines, and policy/procedure/configuration documentation
184
Connection-Oriented
Network communication between two hosts that includes negotiation between the hosts to establish a communication session. Data segments are then transferred between hosts, with each segment being acknowledged before a subsequent segment can be sent. Orderly closure of the communication is conducted at the end of the data transfer or in the event of a communication failure. TCP is the only connection-oriented protocol in the TCP/IP suite
185
Connection-Oriented Communication
A protocol that establishes a connection between two hosts before transmitting data and verifies receipt before closing the connection between the hosts. TCP is an example of a connection-oriented protocol.
186
Connectionless
A type of communication characterized by sending packets that are not acknowledged by the destination host. UDP is the quintessential connectionless protocol in the TCP/IP suite.
187
Connectionless Communication
A protocol that does not establish and verify a connection between the hosts before sending data; it just sends the data and hopes for the best. This is faster than connection-oriented protocols. UDP is an example of a connectionless protocol.
188
Console Port
Connection jack in a switch used exclusively to connect a computer that will manage the switch.
189
Content Switch
Advanced networking device that works at least at Layer 7 (Application layer) and hides servers behind a single IP
190
Contingency Planning
The process of creating documents that set about how to limit damage and recover quickly from an incident
191
Continuity
The physical connection of wires in a network
192
Continuity Tester
Inexpensive network tester that can only test for continuity on a line
193
Convergence
Point at which the routing tables for all routers in a network are updated
194
Core
The central glass of the fiber-optic cable that carries the light signal
195
Cost
An arbitrary metric value assigned to a network route with OSFP capable routers
196
Counter
A predefined event that is recorded to a log file.
197
CWDM
Coarse Wavelength Division Multiplexing An optical multiplexing technology in which a few signals of different optical wavelength could be combined to travel a fairly short distance
198
CRC
Cyclic Redundancy Check A mathematical method used to check for errors in long streams of transmitted data with high accuracy
199
Crimper
Also called a crimping tool, the tool used to secure a crimp (or an RJ-5 connector) onto the end of a cable.
200
Cross-Platform Support
Standards created to enable terminals (and now operating systems) from different companies to interact with one another
201
Crossover Cable
A specially terminated UTP cable used to interconnect routers or switches, or to connect network cards without a switch. Crossover cables reverse the sending and receiving wire pairs from one end to the other.
202
Crosstalk
Electrical signal interference between two cables that are in close proximity to each other
203
CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance Access method used mainly on wireless networks. Before hosts send out data, they first listen for traffic. If the network is free, they send out a signal that reserves a certain amount of time to make sure the network is free of other signals. If data is detected on the wire, the hosts wait a random time period before trying again. If the wire is free, the data is sent out.
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CSMA/CD
Carrier Sense Multiple Access with Collision Detection Access method that Ethernet systems use in wired LAN technologies, enabling frames of data to flow through the network and ultimately reach address locations. Hosts on CSMA/CD networks first listen to hear of there is any data on the wire. If there is none, they send out data. If a collision occurs, then both hosts wait a random time period before retransmitting the data
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CSU/DSU
Channel Service Unit/Data Service Unit A piece of equipment that connects a T-carrier leased line from the telephone company to a customer’s equipment (such as a router). It performs line encoding and conditioning functions, and it often has a loopback function for testing
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CPE
Customer-Premises Equipment The primary distribution box and customer-owned/managed equipment that exists on the customer side of the demarc
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Daily Backup
Also called a daily copy backup, makes a copy of all files that have been changed on that day without changing the archive bits of those files
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Daisy-chain
A method of connecting together several devices along a bus and managing the signals for each device
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Data Backup
The process of creating extra copies of data to be used in case the primary data source fails
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DES
Data Encryption Standard
A symmetric-key algorithm developed by the U.S. government in the 1970s and formerly in use in a variety of TCP/IP applications. DES used a 64-bit block and a 56-bit key. Over time, the 56-bit key made DES susceptible to brute-force attacks
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Data Link Layer
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DOCSIS
Data Over Cable Service Interface Specification The unique protocol used by cable modem networks
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Datagram
A connectionless transfer unit created with User Datagram Protocol designed for quick transfers over a packet-switched network
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DB-25
A 25-pin, D-shaped subminiature connector, typically use in parallel and older serial port connections
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DB-9
A 9-pin, D-shaped subminiature connector, often used in serial port connections
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De-encapsulation
The process of stripping all the extra header information from a packet as the data moves up a protocol stack
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Dead Spot
A place that should be covered by the network signal but where devices get no signal
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dB
Decibel A measurement of the quality of a signal
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Dedicated Circuit
A circuit that runs from a breaker box to specific outlets
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Dedicated Line
A telephone line that is an always open, or connected, circuit. Dedicated telephone lines usually do not have telephone numbers
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Dedicated Server
A machine that does not use any client functions, only server function
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Default
A software function or operation that occurs automatically unless the user specifies something else
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Default Gateway
In a TCP/IP network, the IP address of the router that interconnects the LAN to a wider network, usually the Internet. This router’s IP address is part of the necessary TCP/IP configuration for communicating with multiple networks using IP.
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D Channel
Delta Channel A type of ISDN line that transfers data at 16 Kbps
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Demarc
A device that marks the dividing line of responsibility for the functioning of a network between internal users and upstream service providers
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Demarc Extension
Any cabling that runs from the network interface to whatever box is used by the customer as a demarc
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DMZ
Demilitarized Zone A lightly protected or unprotected subnet network positioned between an outer firewall and an organization’s highly protected internal network. DMZs are used mainly to host public address servers (such as Web servers)
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Demultiplexer
Device that can extract and distribute individual streams of data that have been combined together to travel along a single shared network cable
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DoS
Denial of Service An effort to prevent users from gaining normal use of a resource
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DR
Designated Router The main router in an OSPF network that relays information to all other routers in the area
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Destination Port
A fixed, predetermined number that defines the function or session type in a TCP/IP network
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Device Driver
A subprogram to control communications between the computer and some peripheral hardware
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Device ID
The last six digits of a MAC address, identifying the manufacturer’s unique serial number for that NIC
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Device Types/Requirements
With respect to installing and upgrading networks, these determine what equipment is needed to build the network and how the network should be organized
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DHCP Lease
Created by the DHCP server to allow a system requesting DHCP IP information to use that information for a certain amount of time
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DHCP Relay
A router process that, when enabled, passes DHCP requests and responses across router interfaces. In common terms, DHCP communications can cross from one network to another within a router that has DHCP relay enabled and configured
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DHCP Scope
The pool of IP addresses that a DHCP server may allocate to clients requesting IP addresses or other IP information like DNS server addresses
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DHCP Snooping
Switch process that monitors DHCP traffic, filtering out DHCP messages from untrusted sources. Typically used to block attacks that use a rogue DHCP server
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Dial-up Lines
Telephone lines with telephone numbers; they must dial to make a connection, as opposed to a dedicated line
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Differential Backup
Similar to an incremental backup in that it backs up the files that have been changed since the last backup. This type of backup does not change the state of the archive bit.
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DiffServ
Differentiated Services The underlying architecture that makes quality of service (QoS) work
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DIG
Domain Information Groper Command-line tool in non-Windows systems used to diagnose DNS problems
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DS1
Digital Signal 1 The signaling method used by T1 lines, which uses a relatively simple frame consisting of 25 pieces: a framing bit and 24 channels. Each DS1 channel holds a single 8-bit DS0 data sample. The framing bit and data channels combine to make 193 bits per DS1 frame. These frames are transmitted 8000 times/sec, making a total throughput of 1.544 Mbp
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DSP
Digital Signal Processor A specialized microprocessor-like device that processes digital signals at the expense of other capabilities, much as the floating-point unit (FPU) is optimized for math functions. DSPs are used in such specialized hardware as high-speed modems, multimedia sound cards, MIDI equipment, and real-time video capture and compression
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Digital Signature
An encrypted hash of a private encryption key that verifies a sender’s identity to those who receive encrypted data or messages
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DSL
Digital Subscriber Line A high-speed Internet connection technology that uses a regular telephone line for connectivity. DSL comes in several varieties, including Asymmetric (ADSL) and Symmetric (SDSL), and many speeds. Typical home-user DSL connections are ADSL with a download speed of up to 9 Mbps and an upload speed of up to 1 Kbps
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Dipole Antenna
The standard straight-wire antenna that provides most omnidirectional function.
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DC
Direct Current A type of electric circuit where the flow of electrons is in a complete circle
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DSSS
Direct-Sequence Spread-Spectrum
A spread-spectrum broadcasting method defined in the 802.11 standard that sends data out on different frequencies at the same time
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Directional Antenna
An antenna that focuses its signal more towards a specific direction; as compared to an omnidirectional antenna that radiates its signal in all directions equally
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Disaster Recovery
The means and methods to recover primary infrastructure from a disaster. Disaster recovery starts with a plan and includes data backups
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DAC
Discretionary Access Control Authorization method based on the idea that there is an owner of a resource who may at his or her discretion assign access to that resource. DAC is considered much more flexible than mandatory access control (MAC)
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Disk Mirroring
Process by which data is written simultaneously to two or more disk drives. Read and write speed is decreased but redundancy, in case of catastrophe, is increased. Also known as RAID level 1. See also Duplexing
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Disk Striping
Process by which data is spread among multiple (at least two) drives. It increases speed for both reads and writes of data, but provides no fault tolerance. Also known as RAID level 0
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Disk Striping with Parity
Process by which data is spread among multiple (at least three) drives, with parity information as well to provide fault tolerance. The most commonly implemented type is RAID 5, where the data and parity information is spread across three or more drives
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Dispersion
Diffusion over distance of light propagating down fiber cable
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Distance Vector
Set of routing protocols that calculates the total cost to get to a particular network ID and compares that cost to the total cost of all the other routes to get to that same network ID
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DCS
Distributed Control System A small controller added directly to a machine used to distribute the computing load
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DCF
Distributed Coordination Function One of two methods of collision avoidance defined by the 802.11 standard and the only one currently implemented. DCF specifies strict rules for sending data onto the network media. See also Point Coordination Function (PCF)
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DDoS
Distributed Denial of Service Multicomputer assault on a network resource that attempts, with sheer overwhelming quantity of requests, to prevent regular users from receiving services from the resource
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DDoS Attack
Distributed Denial of Service Attack A DoS attack that uses multiple (as in hundreds or up to hundreds of thousands) of computers under the control of a single operator to conduct a devastating attack
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DLL
Dynamic Link Library A file of executable functions or data that can be used by a Windows application. Typically, a DLL provides one or more particular functions, and a program accesses the functions by creating links to the DLL
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DNS Domain
A specific branch of the DNS name space. Top-level DNS domains include .com, .gov, and .edu.
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DNS Resolver Cache
A cache used by Windows DNS clients to keep track of DNS information
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DNS Root Servers
The highest in the hierarchy of DNS servers running the Internet
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DNS Server
Domain Naming System: A system that runs a special DNS server program
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DNS Tree
A hierarchy of DNS domains and individual computer names organized into a tree-like structure, the top of which is the root
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Document
A medium and the data recorded on it for human use; for example, a report sheet or book. By extension, any record that has permanence and that can be read by a human or a machine
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Documentation
A collection of organized documents or the information recorded in documents. Also, instructional material specifying the inputs, operations, and outputs of a computer program or system
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Domain
A term used to describe a grouping of users, computers, and/or networks. In Microsoft networking, a domain is a group of computers and users that shares a common account database and a common security policy. For the Internet, a domain is a group of computers that shares a common element in their DNS hierarchical name
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Domain Controller
A Microsoft Windows Server system specifically configured to store user and server account information for its domain. Often abbreviated as “DC.” Windows domain controllers store all account and security information in the Active Directory directory service
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DNS
Domain Name System A TCP/IP name resolution system that resolves host names to IP addresses
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Domain Users and Groups
Users and groups that are defined across an entire network domain
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Door Access Controls
Methodology to grant permission or to deny passage through a doorway. The method may be computer-controlled, human-controlled, token-oriented, or many other means
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Dotted Decimal Notation
Shorthand method for discussing and configuring binary IP addresses
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Download
The transfer of information from a remote computer system to the user’s system. Opposite of upload
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Drive Duplexing
Also called disk duplexing or drive duplexing, similar to mirroring in that data is written to and read from two physical drives for fault tolerance. In addition, separate controllers are used for each drive, for both additional fault tolerance and additional speed. Considered RAID level 1. See also Disk Mirroring.
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Drive Mirroring
The process of writing identical data to two hard drives on the same controller at the same time to provide data redundancy
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DS0
The digital signal rate created by converting analog sound into 8-bit chunks 8000 times a second, with a data stream of 64 Kbps. This is the simplest data stream (and the slowest rate) of the digital part of the phone system
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DS1
The signaling method used by T1 lines, which uses a relatively simple frame consisting of 25 pieces: a framing bit and 24 channels. Each DS1 channel holds a single 8-bit DS0 data sample. The framing bit and data channels combine to make 193 bits per DS1 frame. These frames are transmitted 8000 times/sec, making a total throughput of 1.544 Mbp
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(DSLAM
DSL (Digital Service Lines) Access Multiplexer A device located in a telephone company’s central office that connects multiple customers to the Internet
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DSL Modem
A device that enables customers to connect to the Internet using a DSL connection. A DSL modem isn’t really a modem—it’s more like an ISDN terminal adapter—but the term stuck, and even the manufacturers of the devices now call them DSL modems
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DSP
Digital Signal Processor A specialized microprocessor-like device that processes digital signals at the expense of other capabilities, much as the floating-point unit (FPU) is optimized for math functions. DSPs are used in such specialized hardware as high-speed modems, multimedia sound cards, MIDI equipment, and real-time video capture and compression
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Duplexing
Also called disk duplexing or drive duplexing, similar to mirroring in that data is written to and read from two physical drives for fault tolerance. In addition, separate controllers are used for each drive, for both additional fault tolerance and additional speed. Considered RAID level 1. See also Disk Mirroring.
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Dynamic Addressing
A way for a computer to receive IP information automatically from a server program. See also Dynamic Host Configuration Protocol (DHCP)
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DAI
Dynamic ARP Inspection Cisco process that updates a database of trusted systems. DAI then watches for false or suspicious ARPs and ignores them to prevent ARP cache poisoning and other malevolent efforts
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DDNS
Dynamic DNS A protocol that enables DNS servers to get automatic updates of IP addresses of computers in their forward lookup zones, mainly by talking to the local DHCP server
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DHCP
Dynamic Host Configuration Protocol A protocol that enables a DHCP server to set TCP/IP settings automatically for a DHCP client
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Dynamic NAT
Type of NAT in which many computers can share a pool of routable IP addresses that number fewer than the computers
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Dynamic Port Numbers
Port numbers 49152–65535, recommended by the IANA to be used as ephemeral port numbers
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Dynamic Routing
Process by which routers in an internetwork automatically exchange information with other routers. Requires a dynamic routing protocol, such as OSPF or RIP
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Dynamic Routing Protocol
A protocol that supports the building of automatic routing tables, such as OSPF or RIP
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E-mail
Electronic Mail Messages, usually text, sent from one person to another via computer. E-mail can also be sent automatically to a large number of addresses, known as a mailing list.
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E-mail Alert
Notification sent by e-mail as a result of an event. A typical use is a notification sent from an SNMP manager as a result of an out of tolerance condition in an SNMP managed device
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E-mail Client
Program that runs on a computer and enables a user to send, receive, and organize e-mail
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E-mail Server
Also known as mail server, a server that accepts incoming e-mail, sorts the e-mail for recipients into mailboxes, and sends e-mail to other servers using SMTP
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E1
The European counterpart of a T1 connection that carries 32 channels at 64 Kbps for a total of 2.048 Mbps—making it slightly faster than a T1
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E3
The European counterpart of a T3 line that carries 16 E1 lines (512 channels), for a total bandwidth of 34.368 Mbps—making it a little bit slower than an American T3
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EAP-TLS
Extensible Authentication Protocol with Transport Layer Security A protocol that defines the use of a RADIUS server as well as mutual authentication, requiring certificates on both the server and every client
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EAP-TTLS
A protocol similar to EAP-TLS but only uses a single server-side certificate
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Edge
A hardware device that has been optimized to perform a task in coordination with other edge devices and controllers
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Edge Router
Router that connects one Autonomous System (AS) to another
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Effective Permissions
The permissions of all groups combined in any network operating system
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EMI
Electromagnetic Interference Interference from one device to another, resulting in poor performance in the device’s capabilities. This is similar to having static on your TV while running a hair dryer, or placing two monitors too close together and getting a “shaky” screen
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Electronic Discovery
The process of requesting and providing electronic and stored data and evidence in a legal way
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ESD
Electrostatic Discharge The movement of electrons from one body to another. ESD is a real menace to PCs because it can cause permanent damage to semiconductors
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Emulator
Software or hardware that converts the commands to and from the host machine to an entirely different platform. For example, a program that enables you to run Nintendo games on your PC
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