Networking and OSI Basics

How does the internet work?

The OSI Model

The Open Systems Interconnection (OSI) model explains how data travels across networks in 7 layers:

Layer 7 - Application

• What users interact with


• HTTP, FTP, SMTP, DNS


• Web browsers, email clients

Layer 6 - Presentation



• Data formatting and encryption


• SSL/TLS, JPEG, ASCII

Layer 5 - Session



• Managing connections


• Authentication, reconnection

Layer 4 - Transport



• Reliable data transfer


• TCP (reliable), UDP (fast)


• Port numbers

Layer 3 - Network



• Routing between networks


• IP addresses


• Routers

Layer 2 - Data Link



• Local network communication


• MAC addresses


• Switches, bridges

Layer 1 - Physical



• Actual cables and signals


• Ethernet, WiFi, fiber

Key Protocols

DHCP (Dynamic Host Configuration Protocol)

Automatically assigns IP addresses to devices on a network.

DNS (Domain Name System)

Translates domain names (google.com) to IP addresses.

ARP (Address Resolution Protocol)

Maps IP addresses to MAC addresses on local networks.

MAC Addresses

Physical hardware addresses, unique to each network interface.

IP Addresses

Logical addresses for routing between networks.

How Data Travels

1. Application creates data
2. Data is segmented and given port numbers
3. IP addresses are added for routing
4. MAC addresses are added for local delivery
5. Data becomes electrical/optical signals
6. Process reverses at destination

Interactive Version

For a more hands-on learning experience: https://www.hackers-game.com/2020/11/07/networking-and-osi-basics/

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