How the Internet Works
Explore packet delivery, network types, routing, and file permissions
What Are Packets?
When you send data over the internet (email, photo, video), it doesn't travel as one big chunk. Instead, it's broken into small pieces called packets.
Why packets?
- Efficiency: Multiple data streams can share the same network
- Reliability: If one packet is lost, only that piece needs resending
- Speed: Packets can take different routes to reach destination faster
- Error Checking: Each packet has checksums to verify data integrity
Packet Structure:
- Header: Source IP, Destination IP, Packet number, Protocol
- Payload: The actual data being sent
- Footer: Error-checking information
📦 Interactive Packet Delivery Simulator
Send a packet from your computer to a website! Click "Send Packet" to watch it travel through routers.
📋 Packet Journey Log:
Click "Send Packet" to start the journey!
LAN vs WAN
Networks come in different sizes. Understanding the difference helps you secure the right areas!
🏠 Interactive LAN vs WAN Comparison
Click the tabs to compare Local Area Networks and Wide Area Networks.
LAN Characteristics:
- Coverage: Single building or campus (up to a few kilometers)
- Speed: Very fast (1-10 Gbps typical)
- Ownership: You own and control it
- Examples: Home network, school network, office
- IP Range: Private (192.168.x.x, 10.x.x.x)
- Cost: Low (one-time equipment purchase)
- Security: Easier to control (you manage it)
WAN Characteristics:
- Coverage: Global (cities, countries, continents)
- Speed: Variable (depends on distance and infrastructure)
- Ownership: ISPs and telecom companies own infrastructure
- Examples: The Internet, corporate networks spanning cities
- IP Range: Public (unique globally routable addresses)
- Cost: Ongoing (monthly ISP fees)
- Security: Complex (data travels through many hands)
File Permissions (Linux/Unix)
Every file on a system has permissions that control who can read, write, or execute it. This is critical for security!
Three Permission Types:
- Read (r): View the file contents
- Write (w): Modify or delete the file
- Execute (x): Run the file as a program/script
Three User Categories:
- Owner: The user who created the file
- Group: Users who belong to the file's group
- Others: Everyone else on the system
🔐 Interactive File Permissions Tool
Adjust permissions and see both numeric (755) and symbolic (rwxr-xr-x) formats!
IP Addressing Basics
Every device on a network needs an address, just like houses need street addresses!
IPv4 Format: Four numbers (0-255) separated by dots: 192.168.1.100
Private IP Ranges (for LANs):
192.168.0.0to192.168.255.255(most home networks)10.0.0.0to10.255.255.255(large organizations)172.16.0.0to172.31.255.255(medium businesses)
Public IPs: Unique addresses visible on the internet, assigned by ISPs
Routing: How Packets Find Their Way
Routers are like smart traffic directors. They look at a packet's destination IP and decide the best path to send it.
What routers do:
- Read the packet's destination IP address
- Check their routing table (map of networks)
- Forward packet to the next router closer to destination
- Repeat until packet arrives!
Routing Protocols: Routers communicate with each other to learn the network topology and find optimal paths (BGP, OSPF, RIP)
Key Takeaways
- ✅ Data travels in packets (small chunks) for efficiency and reliability
- ✅ LANs are local networks you control; WANs span cities/countries
- ✅ Routers direct packets using IP addresses and routing tables
- ✅ File permissions control who can access files (read/write/execute)
- ✅ Private IPs are for internal networks; public IPs are globally unique
- ✅ Understanding these basics helps you secure networks properly!