Computer Networking & OSI Model Key Concepts

A complete list of vocabulary flashcards covering the OSI model, networking devices, protocols, ports, IP address formats, and key networking concepts.

OSI Model

A model that explains how data travels between devices by dividing network communication into 7 layers.

All People Seem To Need Data Processing

The mnemonic used to remember the 7 OSI layers from Layer 7 to Layer 1 (Application, Presentation, Session, Transport, Network, Data Link, Physical).

Application Layer (Layer 7)

The top layer of the OSI model that provides network services directly to end-user applications, utilizing protocols such as HTTP, HTTPS, FTP, DNS, and SMTP.

Presentation Layer (Layer 6)

The OSI layer that translates, encrypts, compresses, and formats data, associated with TLS/SSL, JPEG, and ASCII.

Session Layer (Layer 5)

The OSI layer that starts, manages, and ends communication sessions between devices.

Transport Layer (Layer 4)

The OSI layer that handles end-to-end data delivery using two major protocols: TCP and UDP.

Network Layer (Layer 3)

The OSI layer that routes data between networks using IP addresses, primarily operated on by routers.

Data Link Layer (Layer 2)

The OSI layer that handles communication between devices on the same local network using MAC addresses, primarily operated on by switches.

Physical Layer (Layer 1)

The OSI layer that transmits bits as electrical, light, or radio signals, involving Ethernet cables, fiber-optic cables, connectors, and radio signals.

Firewall

A network device or system used to filter network traffic and help prevent unwanted or unauthorized access based on IP addresses, ports, protocols, and rules.

Protocol

A set of rules that determines how devices communicate across a network.

DMZ (Demilitarized Zone)

A separate network area for systems that need outside access while helping protect the private internal network.

Router

A networking device that operates primarily at Layer 3 (Network) to route traffic between different networks using IP addresses.

Switch

A networking device that operates primarily at Layer 2 (Data Link) to connect devices on a local network and send data to the correct device using MAC addresses.

IPv4 Address

A 32-bit network address made of four decimal numbers separated by periods (such as 192.168.1.1).

IPv6 Address

A 128-bit network address made of hexadecimal values separated by colons (such as 2001:db8::1), created because available IPv4 address space was limited.

LAN (Local Area Network)

A network covering a small local area, such as a home, dorm, office, or school building.

WAN (Wide Area Network)

A network that connects networks across a large geographic area, with the Internet being the largest example.

WLAN (Wireless Local Area Network)

A local area network that uses wireless connections such as Wi-Fi.

VLAN (Virtual Local Area Network)

A way to logically separate devices into different networks even when they may share physical networking equipment.

TCP Three-Way Handshake

The process TCP uses to begin communication, consisting of three sequential steps: SYN, SYN-ACK, and ACK.

MAC Address (Media Access Control)

An identifier associated with a device's network interface, operating at Layer 2 (Data Link).

TCP (Transmission Control Protocol)

A connection-oriented protocol where key word is reliability, providing ordered data delivery for applications like web traffic, email, and file transfers.

UDP (User Datagram Protocol)

A connectionless protocol where key word is speed, sending data without guaranteeing delivery or order for applications like live video, voice calls, and online gaming.

Port Number Range

The full range of port numbers from 0 through 65,535, totaling 65,536 possible port numbers with 65,535 being the highest possible port number.

Port 21

The port commonly used by FTP for control connections.

Port 22

The port used by SSH.

Port 23

The port used by Telnet, which is considered insecure because it does not encrypt the session like SSH does.

Port 25

The port commonly used by SMTP.

Port 53

The port commonly used by DNS.

Port 80

The port used by HTTP by default.

Port 443

The default port used by HTTPS, which uses TLS encryption to secure HTTP communication (where 'S' stands for Secure).

TCP/IP Model

A four-layer network framework ordered from top to bottom as Application → Transport → Internet → Network Access.

Private IPv4 Address Ranges

Reserved IPv4 ranges consisting of 10.0.0.0–10.255.255.255 (10.x.x.x), 172.16.0.0–172.31.255.255 (172.16–31.x.x), and 192.168.0.0–192.168.255.255 (192.168.x.x).

ARP (Address Resolution Protocol)

A protocol that finds the MAC address associated with an IPv4 address on a local network (IP address → MAC address).