Computer Networks – How Devices Communicate and Share Data

💡 What is a Computer Network?

A computer network is a group of connected devices (computers, phones, servers) that share resources, such as files, internet, printers, or apps.

Key goals of networking: 

 ✅ Communication
✅ File and data sharing
✅ Internet access
✅ Centralized management
✅ Remote access and control

Without networks, the internet, email, social media, and cloud services wouldn’t exist.

 Common Network Types 

1. Local Area Network (LAN) – Covers small areas like homes, schools, or offices. Example: School computer lab.

2. Wide Area Network (WAN) – Connects cities or countries. The internet is the biggest WAN.

3. Metropolitan Area Network (MAN) – Covers cities or large campuses.

4. Wireless Networks (WLAN) – Uses Wi-Fi instead of cables to connect devices.

5. Personal Area Network (PAN) – Connects devices around one person (e.g., phone + Bluetooth headset).

🔧 Basic Networking Devices

Router – Connects multiple networks and manages traffic. Your home router connects you to the internet.

Switch – Connects devices within a LAN and sends data only where needed.

Modem – Connects your local network to your internet provider.

Access Point – Extends wireless signals.

Firewall – Monitors traffic for security and filters unauthorized access.

🌐 IP Address and DNS 

An IP address is a unique number assigned to every device on a network. It’s like a home address for data delivery.

IPv4 uses numbers like 192.168.1.1
IPv6 uses longer codes to support more devices

DNS (Domain Name System) converts website names (like ardiland.com) into IP addresses. It’s like a phonebook for the internet.

🔁 How Data Travels in a Network

Data moves in small units called packets. Each packet includes:

• Sender’s IP

• Receiver’s IP

• Data being sent

• Instructions to rebuild it in order

When you visit a site:

1. Your browser sends a request

2. DNS converts the domain to an IP

3. Router sends data to the server

4. Server responds with a webpage

5. Your browser displays it

🧩 Important Network Protocols

HTTP/HTTPS – Used for websites
TCP/IP – Core communication protocol of the internet
FTP – Transfers files
SMTP/IMAP – Handles email sending/receiving
DHCP – Assigns IP addresses automatically
DNS – Resolves domain names
VPN – Secures private network access over the internet

Protocols ensure that devices understand and handle data the same way.

🔐 Network Security Essentials

Networks need protection from:

• Hackers

• Malware

• Unauthorized users

• Data theft

Common security tools:

• Firewalls

• Antivirus software

• Network segmentation

• Encryption (e.g., HTTPS, VPNs)

• User authentication and strong passwords

For Ethiopian businesses and government offices, network security is critical to avoid data breaches or attacks.

🔌 Wired vs Wireless Networks

Wired Networks

• Faster and more stable

• Used in offices and data centers

• Requires Ethernet cables

Wireless Networks

• More convenient (no cables)

• Common in homes, schools, cafes

• Depends on signal strength and interference

📚 Real-World Uses of Networking in Ethiopia

 ✅ Internet cafes and libraries using LAN to share printers
✅ Hospitals using intranets to manage patient data
✅ Schools offering Wi-Fi across campus
✅ Banks using secure private networks to transfer transactions
✅ Homes using routers for internet, streaming, and remote work

💼 Career Roles That Use Networking

• IT Support Technician

• Network Administrator

• Cybersecurity Analyst

• System Engineer

• Data Center Technician

• Telecom Field Engineer