Module Review
Congratulations on completing the Network Foundations module! You now have the mental model required to understand every other concept in this course.
1. Key Takeaways
- Abstraction is Key: The OSI Model (7 layers) and TCP/IP Model (4 layers) exist to separate concerns. Application developers shouldn’t worry about voltage levels.
- The Hourglass: The Internet runs on IP. It is the narrow waist that connects every app to every physical medium.
- Packet Switching Won: Circuit switching (Phone network) is inefficient for bursty data. Packet switching (Internet) uses Statistical Multiplexing to share bandwidth efficiently.
- Physics Matters: Latency isn’t just one number. It’s Propagation (Speed of Light) + Transmission (Bandwidth) + Queuing (Congestion).
- Redundancy: Modern data centers use Spine-Leaf topologies to ensure consistent latency and high availability.
2. Cheat Sheet
| Concept | Definition | Key Metric |
|---|---|---|
| OSI Layer 7 | Application (HTTP, DNS) | User Experience |
| OSI Layer 4 | Transport (TCP, UDP) | Reliability, Ports |
| OSI Layer 3 | Network (IP) | Routing, Logical Address |
| OSI Layer 2 | Data Link (Ethernet) | MAC Address, Framing |
| Bandwidth | Max capacity of the link | Bits per Second (bps) |
| Throughput | Actual data transfer rate | Bits per Second (bps) |
| Latency | Time from Source to Dest | Milliseconds (ms) |
| Full-Duplex | Send & Receive simultaneously | 2x Bandwidth |
3. Flashcards
Test your memory. Click to flip.
🤔
Which OSI Layer handles Routing and Logical Addressing?
Layer 3 (Network Layer)
Protocols: IPv4, IPv6, ICMP.
📦
Why is Packet Switching better for the Internet than Circuit Switching?
Statistical Multiplexing
It handles "bursty" traffic better by allowing users to share bandwidth dynamically.
⏳
If you double the cable length, which type of delay increases?
Propagation Delay
Speed of light is constant. More distance = more time. Bandwidth doesn't help.
🏗️
What is the "Waist" of the Internet Hourglass?
IP (Internet Protocol)
Every network device must speak IP. It connects diverse Apps to diverse Hardware.
🔄
Which topology is used in modern Data Centers for deterministic latency?
Spine-Leaf
Every Leaf connects to every Spine. Maximum 3 hops between any two servers.
4. Next Steps
Now that we understand the foundations, we will dive deep into the hardware.