NETWORK TERMS

A

Address – a DNS record (the "A record") that points a domain name to an IPv4 address

ACL

Access Control List – a list of rules that says who or what is allowed or blocked from using a network resource

AH

Authentication Header – an IPSec protocol that proves a packet is real and unchanged, but does not encrypt it

AP

Access Point – a device that lets Wi-Fi devices connect to a wired network

API

Application Programming Interface – a set of rules that lets one program talk to another program

APIPA

Automatic Private Internet Protocol Addressing – a 169.254.x.x address a device gives itself when it can't reach a DHCP server

ARP

Address Resolution Protocol – finds the MAC address that belongs to a known IP address on the local network

AUP

Acceptable Use Policy – a company's rules for how employees may use its networks and devices

BGP

Border Gateway Protocol – the routing protocol that swaps routes between large networks and holds the internet together

BNC

Bayonet Neill–Concelman – a twist-lock connector used with coaxial cable

BSSID

Basic Service Set Identifier – the unique MAC address of a wireless access point

BYOD

Bring Your Own Device – a policy that lets employees use their personal phones and laptops for work

CAM

Content-addressable Memory – fast memory in a switch that stores its table of MAC addresses and which port each one is on

CDN

Content Delivery Network – a group of servers around the world that deliver web content from a spot close to the user

CDP

Cisco Discovery Protocol – a Cisco-only protocol that lets directly connected Cisco devices learn about each other

CIA

Confidentiality, Integrity, and Availability – the three main goals of security: keep data private, keep it accurate, and keep it accessible

CIDR

Classless Inter-domain Routing – a way to write IP address ranges with a slash, like /24, instead of fixed classes

CLI

Command-line Interface – a text-based way to control a device by typing commands

CNAME

Canonical Name – a DNS record that makes one domain name an alias (nickname) of another

CPU

Central Processing Unit – the "brain" of a computer or device that carries out instructions

CRC

Cyclic Redundancy Check – a math check used to detect errors in data sent over a network

DAC

Direct Attach Copper – a cable with transceivers built into both ends, used for short, fast links between nearby devices

DAS

Direct-attached Storage – storage connected directly to one computer instead of shared over a network

DCI

Data Center Interconnect – the links that connect two or more data centers together

DDoS

Distributed Denial-of-service – an attack where many hacked devices flood a target so it goes offline

DHCP

Dynamic Host Configuration Protocol – automatically gives devices an IP address and other network settings

DLP

Data Loss Prevention – tools and policies that stop sensitive data from leaving an organization

DNS

Domain Name System – translates names like example.com into IP addresses

DNSSEC

Domain Name System Security Extensions – adds digital signatures to DNS answers so they can be trusted and not faked

DoH

DNS over Hypertext Transfer Protocol Secure – sends DNS lookups inside encrypted HTTPS traffic for privacy

DoS

Denial-of-service – an attack that overwhelms a system so real users can't use it

DoT

DNS over Transport Layer Security – encrypts DNS lookups using TLS (uses port 853)

DR

Disaster Recovery – the plan and steps for getting systems working again after a major failure or disaster

EAPoL

Extensible Authentication Protocol over LAN – carries login information between a device and a switch or access point in 802.1X

EIGRP

Enhanced Interior Gateway Routing Protocol – a Cisco routing protocol that mixes features of distance-vector and link-state protocols

EOL

End-of-life – the point when a vendor stops selling a product

EOS

End-of-support – the point when a vendor stops providing updates and help for a product

ESP

Encapsulating Security Payload – an IPSec protocol that encrypts data and can also check that it is genuine

ESSID

Extended Service Set Identifier – the name of a Wi-Fi network that is shared across several access points

EULA

End User License Agreement – the legal contract that explains how you are allowed to use software

FC

Fibre Channel – a high-speed technology used mainly to connect servers to SAN storage

FHRP

First Hop Redundancy Protocol – lets several routers share one virtual gateway so a backup takes over if one fails

FTP

File Transfer Protocol – moves files between computers, but does not encrypt them

GDPR

General Data Protection Regulation – a European Union law that protects people's personal data and privacy

GRE

Generic Routing Encapsulation – a tunneling protocol that wraps one packet inside another so it can cross a network

GUI

Graphical User Interface – a visual interface with windows, icons, and buttons

HTTP

Hypertext Transfer Protocol – the protocol used for web pages, with no encryption (port 80)

HTTPS

Hypertext Transfer Protocol Secure – the encrypted version of HTTP, used for safe web browsing (port 443)

IaaS

Infrastructure as a Service – a cloud service where you rent virtual servers, storage, and networking

IaC

Infrastructure as Code – setting up and managing infrastructure using code files instead of clicking through menus

IAM

Identity and Access Management – systems that control who users are and what they are allowed to access

ICMP

Internet Control Message Protocol – sends error and status messages; used by ping and traceroute

ICS

Industrial Control System – systems that run industrial equipment like factories and power plants

IDF

Intermediate Distribution Frame – a wiring closet on a floor or area that connects back to the MDF

IDS

Intrusion Detection System – watches network traffic and alerts you to suspicious activity, but does not block it

IoT

Internet of Things – everyday smart devices connected to the internet, like cameras and thermostats

IIoT

Industrial Internet of Things – IoT devices used in industrial settings like factories and utilities

IKE

Internet Key Exchange – sets up the secure connection and shares keys for IPSec

IP

Internet Protocol – the addressing and routing system that gets packets to the right place

IPAM

Internet Protocol Address Management – tools for planning, tracking, and managing IP addresses

IPS

Intrusion Prevention System – detects suspicious traffic and actively blocks it

IPSec

Internet Protocol Security – a set of protocols that encrypts and authenticates IP traffic, often used for VPNs

IS-IS

Intermediate System to Intermediate System – a link-state routing protocol used inside large networks

LACP

Link Aggregation Control Protocol – bundles several physical links into one logical link for more speed and backup

LAN

Local Area Network – a network covering a small area like a home, office, or building

LC

Local Connector – a small fiber-optic connector that clicks into place

LDAP

Lightweight Directory Access Protocol – looks up and manages information in a directory, such as Active Directory (port 389)

LDAPS

Lightweight Directory Access Protocol over SSL – the encrypted version of LDAP (port 636)

LLDP

Link Layer Discovery Protocol – a vendor-neutral way for connected devices to share information about themselves

MAC

Media Access Control – the unique hardware address built into a network card

MDF

Main Distribution Frame – the main wiring room where outside lines enter a building

MDIX

Medium Dependent Interface Crossover – a switch port feature that automatically adjusts for straight-through or crossover cables

MFA

Multifactor Authentication – proving who you are with two or more different types of proof, like a password plus a phone code

MIB

Management Information Base – a database of items that SNMP can monitor on a device

MPO

Multifiber Push On – a fiber connector that holds many fibers in one plug

MTBF

Mean Time Between Failure – the average time a device works before it breaks

MTTR

Mean Time To Repair – the average time it takes to fix a device after it breaks

MTU

Maximum Transmission Unit – the largest packet size a network link can carry (1500 bytes on standard Ethernet)

MX

Mail Exchange – a DNS record that says which server handles email for a domain

NAC

Network Access Control – checks a device's identity and health before letting it onto the network

NAS

Network-attached Storage – a file storage device that is shared over the network

NAT

Network Address Translation – lets devices with private IP addresses share a public IP address

NFV

Network Functions Virtualization – running network functions like firewalls and routers as software on regular servers

NIC

Network Interface Card – the hardware that connects a device to a network

NS

Name Server – a DNS record that lists which servers are in charge of a domain

NTP

Network Time Protocol – keeps the clocks on devices in sync

NTS

Network Time Security – adds security to NTP so time updates can be trusted

OS

Operating System – the main software that runs a computer, like Windows, macOS, or Linux

OSPF

Open Shortest Path First – a link-state routing protocol that finds the best path based on link cost

OSI

Open Systems Interconnection – a 7-layer model that explains how network communication works

OT

Operational Technology – hardware and software that controls physical equipment and processes

PaaS

Platform as a Service – a cloud service that gives developers a ready-made platform to build and run apps

PAT

Port Address Translation – a type of NAT that uses port numbers so many devices can share one public IP

PCI DSS

Payment Card Industry Data Security Standards – security rules for any business that handles credit card data

PDU

Power Distribution Unit – a power strip for server racks that spreads power to many devices

PKI

Public Key Infrastructure – the system of certificates, keys, and authorities that makes encryption and digital trust work

PoE

Power over Ethernet – sends electrical power and data over the same network cable

PSK

Pre-shared Key – a password that is shared ahead of time, like a Wi-Fi password

PTP

Precision Time Protocol – a very accurate way to sync clocks, more precise than NTP

PTR

Pointer – a DNS record that maps an IP address back to a name (reverse lookup)