Definitions Flashcards
DHCP
The Dynamic Host Configuration Protocol is a network management protocol used on Internet Protocol networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a client–server architecture.
67 68
DNS
Domain Name System (DNS) An Application-layer protocol that resolves computer and domain names to their IP addresses; it uses UDP port 53.
WAP
access point (AP) A wireless device that serves as the central connection point of a wireless LAN and mediates communication between wireless computers.
ad hoc mode
ad hoc mode Sometimes called “peer-to-peer mode,” it’s a wireless mode of operation typically used only in small or temporary installations. There’s no central device, and data travels from one device to another to reach the destination device.
Address Resolution Protocol (ARP)
An Internetwork-layer protocol used to resolve a host’s IP address to its MAC address. ARP uses a broadcast frame containing the target host’s IP address, and the host that’s assigned the address responds with its MAC address.
Authentication
The process of identifying who has access to the network. The most common form of authentication is a logon with a username and password.
Authorization
The process of granting or denying an authenticated user’s access to network resources.
Baseband
A type of signaling used in networks in which each bit of data is represented by a pulse of electricity (on copper media) or light (on fiber-optic media). These signals are sent at a single fixed frequency, using the medium’s entire bandwidth. LAN technologies use baseband signaling.
Basic input/output system (BIOS)
The firmware found on many PCs that is executed when the computer is powered on. Its primary task is to tell the CPU to perform certain tasks when power is
first applied to the computer, including initializing motherboard hardware, performing a power-on self-test (POST), and beginning the boot procedure.
Broadband
A type of signaling that uses analog techniques to encode binary 1s and 0s across a continuous range of values. Broadband signals move across the medium in the form of continuous electromagnetic or optical waves rather than discrete pulses. Signals flow at a particular frequency, and each frequency represents a channel of data, allowing multiple streams of data on a single wire. TV and cable Internet use broadband signaling.
Broadcast domain
The scope of devices to which broadcast frames are forwarded. Router interfaces delimit broadcast domains because they don’t forward broadcasts, whereas switches and hubs do.
Bus
A collection of wires that carry data from one place to another on a computer’s motherboard.
Byte
A collection of 8 bits that might represent a number or a printable character.
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
A media access method in which a device must first listen (carrier sense) to the medium to be sure no other device is transmitting. If two devices transmit at the same time (multiple access), a collision occurs and is detected (collision detection). In this case, all devices involved in the collision wait for a random period of time before transmitting again.
Clear to send (CTS)
A signal an AP generates in response to a request-to-send signal. A CTS signal indicates that the computer that sent an RTS can transmit data. See also access point (AP) and request to send (RTS).
Client
The term used to describe an OS designed mainly to access network resources, a computer’s primary role in a network (running user applications and accessing network resources), and software that requests network resources from servers.
Client-to-site VPN
mode A VPN mode that establishes a VPN connection between a single client computer and a VPN device.
Cloud computing
A networking model in which data, applications, and processing power are managed by servers on the Internet, and users of these resources pay for what they use rather than the equipment and software needed to provide resources.
Cloud storage
A data storage method in which some or all of an organization’s data is stored on servers located offsite and maintained by a storage hosting company.
Collision
The result of two or more devices on the same medium transmitting simultaneously when CSMA/CD is the media access method in use. See also Carrier Sense Multiple Access with Collision Detection (CSMA/CD).
Collision domain
The extent to which signals in an Ethernet bus topology network are propagated. All devices connected to a logical bus topology network are in the same collision domain. Switch and router ports delimit collision domains.
Data Link layer
Layer 2 in the OSI model is responsible for managing access to the network medium and delivery of data frames from sender to receiver or from sender to an intermediate device, such as a router. See also Open Systems Interconnection (OSI) reference model.
Dedicated bandwidth
A property of switches in which each port’s bandwidth is dedicated to the devices connected to the port.
Datagram
The unit of information used by UDP in the Transport layer. A datagram is passed up to the Application layer as data and passed down to the Internetwork layer, where it becomes a packet.
Deencapsulation
The process of stripping the header from a PDU as it makes its way up the communication layers before being passed to the next higher layer. See also protocol data unit (PDU).
Default gateway
The address configured in a computer’s IP address settings specifying the address of a router to which the computer can send packets addressed to devices on other networks.
Denial-of-service (DoS) attack
An attempt
to tie up network bandwidth or services so that network resources are rendered useless to legitimate users.
Disk striping with parity
A fault-tolerant disk configuration in which parts of several physical disks are linked in an array, and data and parity information are written to all disks in this array. If one disk fails, data can be reconstructed from the parity information written on the others.
- RAID 5 – Striping + Parity:
- RAID 6 – Striping with double parity
Distributed denial-of-service (DDoS) attacks
Attacks that use many systems to tie up network bandwidth or services so that network resources are rendered useless to legitimate users.
Dynamic disk
A disk configuration in Windows that can be divided into one or more volumes. You can create up to 1000 volumes per dynamic disk (although no more than 32 are recommended). A dynamic disk offers features that a basic disk doesn’t, namely RAID and disk spanning.
Dynamic Host Configuration Protocol (DHCP)
An Application-layer protocol used to configure a host’s IP address settings dynamically; it uses UDP ports 67 and 68.
Encapsulation
The process of adding header and trailer information to chunks of data.
Encryption
A technology that makes data unusable and unreadable to anyone except authorized users of the data.
Extended star topology
An extension of the physical star topology, in which a central switch or hub is the central connecting point for other switches or hubs that have computers and other network devices attached, forming a star of stars.
Fiber-optic cable
A cable type that carries data over thin strands of glass by using optical (light) pulses to represent bits.
File system
The method by which an OS stores, organizes, and manages access to files on a storage device, such as a hard drive.
File Transfer Protocol (FTP)
An Application-layer protocol used to transfer and manage files across a network; FTP uses TCP ports 20 and 21.
Firewall
A hardware device or software program that inspects packets going into or out of a network or computer and then discards or forwards packets based on a set of rules.
Flood
The process whereby a switch forwards a frame out all connected ports.
Flow control
A mechanism network protocols
use to prevent a destination device from becoming overwhelmed by data from a transmitting computer, resulting in dropped packets.
Frame
A packet with source and destination MAC addresses added and an error-checking code added to the back end. Frames are generated and processed by the network interface. See also packet.
Full-duplex mode
A communication mode in which a device can simultaneously transmit and receive data on the same cable connection. Switches can operate in full-duplex mode, but hubs can’t.
Guest OS
The operating system installed on a virtual machine.
Half-duplex mode
A communication mode in which a device can send or receive data but can’t do both simultaneously. Hubs operate only in half-duplex mode; switches can operate in both half-duplex and full-duplex modes.
Header
Information added to the front end of a chunk of data so that the data can be correctly interpreted and processed by network protocols.
Honeypot
A network device, such as a server, that has been installed as a decoy to lure potential attackers.
Hop
Each router a packet must go through to get to the destination network.
hosted virtualization
A process in which the hypervisor implements OS virtualization by being installed in a general-purpose host OS, such as Windows 10 or Linux, and the host OS accesses host hardware on behalf of the guest OS. See also virtualization.
Hotspot
A public Wi-Fi network that can usually be accessed without an encryption or authentication code.
Hub
A network device that performs the same function as a repeater but has several ports to connect a number of devices; sometimes called a multiport repeater. See also repeater.
Hypervisor
The component of virtualization software that creates and monitors the virtual hardware environment, which allows multiple VMs to share physical hardware resources.
infrastructure as a service (IaaS)
A category of cloud computing in which a company can use a provider’s storage or virtual servers as its needs demand; IaaS is also called “hosted infrastructure.”
infrastructure mode
An operational mode for Wi-Fi networks, in which wireless stations connect through a wireless access point before they can begin communicating with other devices.
Integrated development environment (IDE)
An application that allows you to write, edit, debug, and prepare programs for upload to a development board for execution by a microcontroller or microprocessor.
Internet
A worldwide public internetwork that uses standard protocols, such as TCP/IP, DNS, and HTTP, to transfer and view information.
Internet Control Message Protocol (ICMP)
An Internetwork-layer protocol used to send error, status, and control messages between systems or devices. It’s an encapsulated IP protocol, meaning it’s wrapped in an IP header.
Internet Message Access Protocol version 4 (IMAP4)
An Application-layer protocol used by an e-mail client to download messages from an e-mail server; IMAP4 operates on TCP port 143. IMAP4 also provides fault-tolerance features. It downloads only message headers from the server initially, and then downloads the message body and attachments after the message is selected.
Internet of Things (IoT)
Household or industrial objects that have embedded computer and communication devices that allow the objects to send and receive data to and from a computer network. Examples include lights, thermostats, refrigerators, and devices such as Google Home and Amazon Echo. IoT is the digitization of our everyday world through the use of networked microprocessors and microcontrollers along with sensors, actuators, motors, and other I/O devices, plus the software that makes it all work together.
Internet Protocol Security (IPsec)
An extension to IP working at the Internetwork layer that provides security by using authentication and encryption. It authenticates the identity of computers transmitting data with a password or some other form of credentials, and it encrypts data so that if packets are captured, the data will be unintelligible.
Internet Protocol version 4 (IPv4)
A connectionless Internetwork-layer protocol that provides source and destination addressing and routing for the TCP/IP protocol suite; IPv4 uses 32-bit dotted decimal addresses.
Internet Protocol version 6 (IPv6)
A connectionless Internetwork-layer protocol that provides source and destination addressing and routing for the TCP/IP protocol suite. IPv6 uses 128-bit hexadecimal addresses and has built-in security and QoS features.
internetwork
A networked collection of LANs tied together by devices such as routers. See also local area network (LAN).
intranet
A private network in which devices and servers are available only to users connected to the internal network.
Intrusion detection system (IDS)
Usually a component of a firewall, a hardware device or software that detects an attempted security breach and notifies the network administrator. An IDS can also take countermeasures to stop an attack in progress.
Intrusion prevention system (IPS)
A variation of an IDS that can take countermeasures if an attack is in progress.
IP address
A 32-bit dotted decimal address used by IP to determine the network a host resides on and to identify hosts on the network at the Internetwork layer.
IP address scope
A component of a DHCP server; it’s a range of IP addresses the server leases to clients requesting an IP address.
IP prefix
A value used to express how many bits of an IP address are network ID bits. The value is usually preceded by a / symbol, as in 192.168.1.24/27; in this example, 27 is the IP prefix.
IPv4 address
A 32-bit dotted decimal address containing a network ID, which specifies the network the computer is on, and a host ID, which uniquely identifies the computer on that network.
localhost
A reserved name that corresponds to the loopback address in an IP network.
logical topology
The path that data travels between computers on a network. The most common logical topologies are switched, bus, and ring.
Loopback address
An address that always refers to the local computer; in IPv4, it’s 127.0.0.1, and in IPv6 it’s ::1. This address is used to test TCP/IP functionality on the local computer.
malware
Any software designed to cause harm
or disruption to a computer system or otherwise perform activities on a computer without the consent of the computer’s owner.
Media Access Control (MAC) sublayer
The lower sublayer of the IEEE Project 802 model for the OSI model’s Data Link layer. It handles accessing network media and mapping between logical and physical network addresses for NICs.
media access method A set of rules governing how and when the network medium can be accessed for transmission. The rules ensure that data is transmitted and received in an orderly fashion, and all stations have an opportunity to communicate. Also called “media access control.”
Mesh topology
A topology in which each device in the network is connected to every other device, providing multiple pathways in the event of a device or cable failure.
Multicast address
An address that identifies a group of computers running a multicast application.
Multicasting
A network communication in which a packet is addressed so that more than one destination can receive it.
Network Address Translation (NAT)
A service that translates a private IP address to a public IP address in packets destined for the Internet, and then translates the public IP address in the reply to the private address. NAT is often used to allow using private IP addresses while connected to the Internet.
Network bandwidth
The amount of data that can be transferred on a network during a specific interval; usually measured in bits per second.
Network client software
The application or OS service that can request information stored on another computer.
Network File System (NFS)
The native Linux file-sharing protocol.
Network interface card (NIC)
A device that creates and mediates the connection between a computer and the network medium.
Network layer
Layer 3 of the OSI model handles logical addressing and routing of PDUs across internetworks. See also Open Systems Interconnection (OSI) reference model and protocol data unit (PDU).
network protocols
The software defining the rules and formats a computer must use when sending information across the network.
Packet
A chunk of data with source and destination IP addresses (as well as other IP information) added to it. Packets are generated and processed by network protocols.
Physical bus topology
A network topology in which a continuous length of cable connects one computer to another in daisy-chain fashion. There’s no central interconnecting device.
Physical layer
Layer 1, the bottom layer of the OSI model, transmits and receives signals and specifies the physical details of cables, NICs, connectors,
and hardware behavior. See also Open Systems Interconnection (OSI) reference model.
Physical ring topology
A cabling arrangement
in which each device is connected to another
device in daisy-chain fashion, and the last device connects back to the first device to form a ring. Used by token ring and FDDI, the physical ring is rarely used now.
Physical star topology
A network topology that uses a central device, such as a hub or switch, to interconnect computers in a LAN. Each computer has a single length of cable going from its NIC to the central device. It’s the most common physical topology in LANs.
Physical topology
The arrangement of cabling and how cables connect one device to another in a network. The most common physical topology is a star, but bus, ring, point-to-point, and mesh topologies are also used.
Platform as a service (PaaS)
A category of cloud computing in which a customer develops applications with the service provider’s development tools and infrastructure; PaaS is also called “hosted platform.” After applications are developed, they can be delivered to the customer’s users from the provider’s servers.
think BlueJ
Port number
A field in the Transport-layer protocol header that specifies the source and destination Application-layer protocols used to request data
(the source) and be the target of the request (the destination).
Port scanner
Software that determines which TCP and UDP ports are available on a computer or device.
Post Office Protocol version 3 (POP3)
An Application-layer protocol used by a client e-mail application to download messages from an e-mail server; POP3 uses TCP port 110.
private cloud
Cloud services that a company delivers to its own employees.
a type of deployment model
Promiscuous mode
An operational mode of a NIC in which all frames are read and processed rather than only broadcast and unicast frames addressed to the NIC. Protocol analyzer software sets a NIC to promiscuous mode so that all network frames can be read and analyzed.
Protocol data unit (PDU)
A unit of information passed as a self-contained data structure from one layer to another on its way up or down the network protocol stack.
public cloud
Cloud services delivered by a third- party provider.
ransomware
A type of malware that redirects you to a Web site warning that your system is infected and that you must install the vendor’s software or call a phone number to clean your system. Your system
is held hostage until you pay the perpetrator a fee to unlock the computer or decrypt your files.
redundant array of independent disks (RAID)
A storage configuration of two or more disks, usually in a fault-tolerant arrangement, so that if one disk fails, data is preserved and the server can continue to operate.
repeater
A network device that takes incoming signals and regenerates, or repeats, them to other parts of the network.
request to send (RTS)
A signal used in wireless networks indicating that a computer has data ready to send on the network. See also access point (AP) and clear to send (CTS).
router
A device that enables LANs to communicate with one another by forwarding packets from one LAN to another. Routers also forward packets from one router to another when LANs are separated by multiple routers.
Secure Shell (SSH)
A secure Application-layer protocol used to connect to a device across a network via a command-line interface; SSH uses TCP port 22.
segment
The unit of information used by TCP in the Transport layer. A segment is passed up to the Application layer as data and passed down to the Internetwork layer, where it becomes a packet.
server
The term used to describe an OS designed mainly to share network resources, a computer with the main role of giving client computers access to network resources, and the software that responds to requests for network resources from client computers.
service set identifier (SSID)
The name assigned to a wireless network that is configured on the wireless access point.
Session layer
Layer 5 of the OSI model is responsible for setting up, maintaining, and ending communication sequences (called sessions) across a network. See also Open Systems Interconnection (OSI) reference model.
Simple Mail Transfer Protocol (SMTP)
An Application-layer protocol used to send e-mail over the Internet; SMTP uses TCP port 25.
Simple Network Management Protocol (SNMP)
An Application-layer protocol used to monitor and manage network devices and gather statistics about network traffic. It operates on UDP ports 161 and 162.
software as a service (SaaS)
A category of cloud computing in which a customer pays for the use of applications that run on a service provider’s network; SaaS is also called “hosted applications.”
thinks apps that come on your phone
spam
Unsolicited e-mail. The harm in spam is
the loss of productivity created when people receive dozens or hundreds of spam messages daily and the resources wasted to receive and store spam on e-mail servers.
spoofed address
A source address inserted into a packet that is not the sender’s actual address.
spyware
A type of malware that monitors or controls part of your computer at the expense of your privacy and the gain of some third party. See also malware.
storage area network (SAN)
A high-speed, high-cost network storage solution for replacing locally attached drives on servers.
subnet mask
subnet mask: A 32-bit dotted decimal number, consisting of a contiguous series of binary 1 digits followed by a contiguous series of binary 0 digits, that determines which part of an IP address is the network ID and which part is the host ID.
subnets
Subdivisions of an IP network address space.
subnetting
subnetting A process that reallocates bits from an IP address’s host portion to the network portion, creating multiple smaller address spaces. See also subnets.
switch
A network device used to interconnect multiple computers; it reads the destination MAC address of an incoming frame to determine
on which switch port the destination device is located.
Telnet
An unsecure Application-layer protocol used to connect to a device across a network via a command-line interface; Telnet uses TCP port 23.
throughput
The actual amount of data transferred, not counting errors and acknowledgments.
Transmission Control Protocol (TCP)
A connection-oriented Transport-layer protocol designed for reliable transfer of information in complex internetworks.
Transmission Control Protocol/Internet Protocol (TCP/IP)
The most common protocol suite; TCP/IP is the default protocol in contemporary OSs and the protocol of the Internet.
Transport layer
Layer 4 of the OSI model is responsible for reliable delivery of data streams across a network. Layer 4 protocols break large streams of data into smaller chunks and use sequence numbers and acknowledgments to provide communication and flow control.
Tunneling
A common network protocol technique that allows transmitting a packet in a format that would otherwise be incompatible for the network architecture by encapsulating the packet in a compatible header format.
User Datagram Protocol (UDP)
A connectionless Transport-layer protocol designed for efficient communication of generally small amounts of data.
virtual machine (VM)
A software environment that emulates a physical computer’s hardware and BIOS.
virtual network
A network configuration created by virtualization software and used by virtual machines for network communication.
virtual private network (VPN)
A temporary or permanent connection across a public network that uses encryption technology to transmit and receive data. See also encryption.
virtualization
A process that creates a software environment to emulate a computer’s hardware and BIOS, allowing multiple OSs to run on the same physical computer at the same time.
Wi-Fi Protected Access (WPA)
A wireless security protocol that’s the successor to Wired Equivalent Privacy and has enhancements that make cracking the encryption code more difficult.
Wi-Fi Protected Access 2 (WPA2)
The successor to Wi-Fi Protected Access that uses Advanced Encryption Standard for the highest level of encryption; WPA2
is the most commonly used encryption standard for wireless networks
Wi-Fi Protected Access 3 (WPA3)
The strongest wireless encryption standard as of this writing. WPA3 uses the most current security methods while disallowing older, more vulnerable protocols.
Wired Equivalent Privacy (WEP)
A wireless security protocol that encrypts data so that unauthorized people receiving wireless network signals can’t interpret the data easily.
