Networks and the Internet
The internet is the largest engineered system in human history. Understanding how data travels from your computer to a server and back — through protocols, routers, and cables — is essential for any software or systems engineer.
Key Concepts
TCP/IP and the Protocol Stack
TCP/IP is the foundation of internet communication. IP addresses route packets across networks. TCP ensures reliable delivery — if a packet is lost, it is re-sent. HTTP runs on top of TCP. The protocol stack layers each add their own responsibilities: physical → data link → network → transport → application.
DNS — The Internet's Phone Book
You type 'google.com' but routers need an IP address. DNS (Domain Name System) translates names to IPs. Your computer asks a DNS resolver, which asks root servers, then TLD servers (.com), then Google's authoritative server. The whole lookup takes milliseconds and the result is cached.
HTTPS and TLS
HTTPS = HTTP over TLS (Transport Layer Security). TLS uses asymmetric encryption (public/private key pairs) to establish a shared secret, then symmetric encryption for the actual data. The lock icon means: 1) you are connected to the real server, 2) your data is encrypted in transit.
🆕 Network Packet Simulator
Watch a data packet travel from client to server through routers. Click Send!
✅ Check Your Understanding
1. What does DNS do?
2. What does HTTPS add over HTTP?
3. What does TCP guarantee that IP alone does not?