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Computer Networks · Module 2 of 10

OSI and TCP/IP models

Understand layered network models.

📖 Key ideas

  1. OSI has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.
  2. TCP/IP has 4 layers: Link, Internet, Transport, Application.
  3. Each layer serves the one above.
  4. Encapsulation adds headers as data moves down.
  5. PDUs: bits, frames, packets, segments, data.
💡 Real-life example: Network layers are a postal system: letter, envelope, sorting office, delivery van.
OSI model7-layer reference model
TCP/IP model4-layer internet model
EncapsulationAdding headers per layer
PDUProtocol Data Unit