Overview
This lecture explains how data travels across networks and the Internet, highlighting key components like routers, firewalls, proxies, and data packet structure.
Data Packet Journey
- Clicking a web link starts the flow of information as data packets.
- Data is split into packets by the sender's system, each with sender and receiver addresses, packet type, and sometimes a proxy address.
- Packets enter the local area network (LAN), where multiple types of data packets coexist.
- The local router reads packet addresses and forwards them to appropriate networks.
Network Components and Functions
- Routers transfer packets between networks based on destination addresses.
- Router switches efficiently manage packet routing within larger networks.
- Proxies act as intermediaries to reduce Internet load and enforce security or access policies.
- Firewalls protect networks by blocking unwanted Internet traffic and preventing unauthorized data from leaving the intranet.
Internet Transmission
- Packets move from the protected intranet to the open Internet, which connects networks globally.
- The Internet has fewer controls, allowing for innovation but also posing risks like malicious data (e.g., "ping of death").
- Data can travel through various mediums: satellites, phone lines, wireless, or underwater cables.
- Delivery routes vary, sometimes causing delays known as "the world wide wait."
Final Delivery and Response
- Upon reaching the destination, packets must pass through another firewall, which filters traffic based on port numbers (e.g., port 80 for web, port 25 for mail).
- Packets are checked and unpacked by the web server, which processes requests and sends data back through the network path to the user's browser.
Key Terms & Definitions
- Packet — A small unit of data sent over a network, carrying addressing and routing information.
- Router — A device that directs data packets between computer networks.
- Router Switch — A high-speed device that routes packets in large networks efficiently.
- Proxy — An intermediary server that manages network requests for security and performance.
- Firewall — A security system that controls traffic between networks based on predefined rules.
- LAN (Local Area Network) — A network connecting computers within a limited area, like a building.
- Ping of Death — A type of network attack using oversized or malicious ping packets.
- Port — A logical access channel for network communications (e.g., port 80 for web traffic).
Action Items / Next Steps
- Review the flow of packets through LAN, proxies, firewalls, the Internet, and web servers.
- Understand key network components and their security functions for future lessons or assignments.