Day 1: How the Internet Works | Networking for Developers

Today's Objective

Learn the core concepts of How the Internet Works and apply them in practical exercises.

The Full Request Journey

Most developers use the internet every day and can't explain how it works. This matters because understanding the journey helps you debug connection failures, DNS issues, and slow page loads.

The 7-step journey

1. You type: https://github.com
2. DNS lookup: 'What IP is github.com?'
   → Resolver queries root → TLD → authoritative DNS
   → Returns: 140.82.112.3
3. TCP handshake to 140.82.112.3:443
   → SYN → SYN-ACK → ACK
4. TLS handshake (HTTPS)
   → Exchange certificates
   → Agree on encryption
5. HTTP GET / request sent
6. Server processes request
7. HTTP 200 response with HTML
   → Browser parses HTML
   → Fetches CSS, JS, images
   → Renders the page

DNS in the terminal

# See DNS resolution
dig github.com
nslookup github.com

# Trace the full DNS path
dig +trace github.com

# Check what DNS server you're using
cat /etc/resolv.conf
nscurl -s https://dns.google/resolve?name=github.com | python3 -m json.tool

💡

When a site won't load, your first question should be: 'Is this a DNS issue or a connection issue?' Run dig github.com. If it returns an IP, DNS is working. Then try curl -v https://github.com to test the connection.

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Day 1 Checkpoint

Before moving on, confirm understanding of these key concepts:

What is the core concept introduced in this lesson?
How does the main technique or tool work in practice?
What common mistakes should be avoided?
How would this apply in a real-world project?
What is the next logical step to build on this knowledge?

How the Internet Works

Today's Objective

The Full Request Journey

Supporting References & Reading

Go deeper with these external resources.

Day 1 Checkpoint