Computer Networks Cheat Sheet
OSI vs TCP/IP Layers Diagram
OSI Layer
TCP/IP Layer
Examples of Protocols
7. Application
Application
HTTP, FTP, DNS, SMTP
6. Presentation
(part of Application)
TLS/SSL, JPEG, GIF
5. Session
(part of Application)
RPC, NetBIOS
4. Transport
Transport
TCP, UDP
3. Network
Internet
IP, ICMP
2. Data Link
Link
Ethernet, Wi-Fi, ARP
1. Physical
Physical
Cables, Fiber, Radio (Wi-Fi signals)
Key Networking Principles
- Encapsulation: Data moves down the stack, each layer adds its own header.
- De-encapsulation: Data moves up the stack, headers are removed.
- DNS: Translates domain names (e.g., www.google.com) into IP addresses.
- End-to-End Principle: Intelligence (error correction, encryption) should reside at the edges, not in the
core.
- Error Correction: Both Data Link (Ethernet, Wi-Fi) and Transport layer (TCP) may provide it.
Quick Quiz Review (Q1–Q10):
1. Dial-up connection between computers.
2. DNS translates names to IPs.
3. Internet stack based on layers.
4. Error correction at Data Link & Transport (True).
5. Sockets connect Application ↔ Transport.
6. DNS is Application layer.
7. Transport protocols: TCP, UDP.
8. Data travels down stack via Encapsulation.
9. End-to-End principle: at edges of network.
10. Hubs/Bridges/Routers differ by OSI layer.
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