Computer Systems and Networks

Computer Systems and Networks

1. How data moves through a network

   • Data Packets
     • Data is broken into small chunks (packets) to be sent across a network. Why? If part of the data gets lost, you only need to resend the lost packets, not the entire file. For example, When you send an email, the message is split into packets. If 1 packet is lost, only that packet is resent.
   • Routing
     • Routers decide which path the packet takes to get to its destination. Why? The shortest path isn’t always available, so routers pick the "next best" path. For example, Imagine driving to school but one road is blocked, so Google Maps finds a new route.
   • Redundancy
     • Multiple paths exist for packets to travel. If one path fails, another path is used. Why? It makes the network more reliable. For example, If one bridge in a city is closed, cars use a different bridge.
   • When you see a network diagram, follow the arrows to see where the data flows. Watch for multiple paths (that’s redundancy!) and understand what happens if one path fails.

2. Network Components

   • Computing Devices
     • Devices like phones, laptops, tablets, and IoT devices. These are the "users" of the network. They send and receive information. For example, Your phone connects to a Wi-Fi router to access the Internet.
   • Input/Output Devices
     • Devices that send and receive data, like keyboards, screens, microphones, and speakers. They allow humans to interact with the system. For example, your keyboard is an input device; your screen is an output device.
   • Networking Devices
     • Routers connects multiple networks and decides where data should go. Switches connects devices within the same network (like your home Wi-Fi). Access Points are wireless devices that let phones and laptops connect to Wi-Fi.
     • Exam Tip: "Be ready to identify and explain the role of a router, switch, or access point in a network scenario."

3. Network Protocols

   • IP (Internet protocol)
     • Every device on a network has a unique address (like a house address) called an IP address. Example: 192.168.1.1 — This might be the IP of your Wi-Fi router. Version: IPv4 (32-bit addresses) and IPv6 (128-bit addresses for more devices).
   • TCP (Transmission Control Protocol)
     • Ensures packets are delivered in the correct order. If a packet is lost, it asks for a resend. For example, when watching a YouTube video, if some packets are missing, TCP makes sure they’re resent so you get the full video.
   • UDP(User Datagram Protocol)
     • Fast but "risky" protocol. It doesn’t check for missing packets. We can see this in video games and live streams, it's better to keep things fast than to wait for missing packets.
   • Exam Tip: "Be ready to explain the difference between TCP and UDP. TCP guarantees delivery, but UDP is faster and good for live streaming or online gaming."

4. Fault Tolerance & Redundancy

   • Redundancy
     • Multiple backup paths exist so data can still move even if one path fails. For example, If one undersea cable breaks, data is rerouted through another cable.
   • Fault Tolerance
     • The ability of a network to keep working, even when something breaks. How? By using redundancy. Multiple paths means data can still flow. For example, one router breaks, data can still move through another route.
   • Exam Tip: "If you see a network diagram with multiple paths, that’s redundancy. If one path is broken and data still flows, that’s fault tolerance."

5. Analyzing Network Diagrams

   • Mark the text strategy
     • Step 1: Highlight key devices (routers, switches, endpoints) on the diagram. Step 2: Follow the arrows to see where the packets flow. Step 3: Check if there’s redundancy. Are there multiple paths for the data to follow?
   • What to look for in a diagram
     • Where is the router? What paths exist for packets to travel? If a link is "cut," will the network still work?
   • Exam Tip: "On test day, you'll see a network diagram with a scenario like 'If this connection is removed, will data still flow?' Look for redundancy and paths that still exist."