How the Internet Works

By the end, you can

• Explain how packet switching works and why it is more scalable than circuit switching.
• Describe the role of routers and why no single central computer controls the internet.
• Explain why packets carry sequence numbers and how the receiver uses them to reassemble the message.
• Name the four TCP/IP layers in order and state what each one does and what PDU it handles.
• Trace the encapsulation journey: data → segment → packet → frame, and explain de-encapsulation.
• State the end-to-end principle and identify which functions belong in the core versus at the end hosts.
• Distinguish bandwidth from latency and explain why they are independent.