How the Internet Works

Lesson objectives

By the end of the week, learners should be able to:

1. Describe how data becomes packets on the internet.
2. Explain why packets are routed rather than sent whole.
3. Name three reasons routing happens across multiple paths.
4. Trace a packet journey from sender to receiver across routers.
5. Define latency as the delay caused by processing and transmission.

Key vocabulary

• Packet: a small segment of data travelling independently.
• Routing: directing packets along the best available path.
• Router: a device forwarding packets toward destinations.
• Latency: the delay before a packet reaches its destination.
• Best available path: the current optimal route given conditions.
• Reassembly: combining arriving packets back into a complete file.
• Transmission delay: time spent on the physical medium.
• Processing delay: time spent handling the packet at each node.

Common misconceptions

• "The internet sends whole files as one piece." Files break into packets for efficient routing.
• "A router sends everything straight to one place." Routing uses multiple paths dynamically.
• "Latency disappears once you reach your target." Latency returns when reassembly adds time.

Teacher activities

1. Starter: show a single file split into three pieces and ask what happens during travel.
2. Explain packets as smaller than the original file and model splitting a file into three.
3. Name three reasons routing uses multiple paths: load balancing, resilience and speed.
4. Trace one packet journey across two routers on paper.
5. Define latency as the sum of transmission and processing delays.
6. Close with the trace task and exit question about packet splitting.

Student activities

1. Answer the starter and explain why packets make travel efficient.
2. Explain why files break into packets and give one benefit.
3. Name three reasons routing uses multiple paths in their own words.
4. Trace a packet journey across two routers and label each stop.
5. Define latency as the combination of transmission and processing delays.
6. Answer the exit question in one sentence about why splitting helps.

Practical / learning evidence

A packet trace worksheet showing sender, three routers, a failed-route recovery and latency breakdown. Plus a one-paragraph packet definition statement. Hand in both for marking.

Resources and preparation

Blank trace template, sample files and a router diagram. Offline route: paper versions, no device needed. Display any diagram carefully and avoid touching network equipment.

Assessment for learning

Inspect the trace for correct routing steps and a sensible latency breakdown. Mark the packet definition for accurate wording. Flag any learner who thinks packets travel as whole files.

Inclusion and homework

Provide the blank trace prefilled in the first router box for learners who need scaffolding. Allow oral completion for the latency breakdown. Extend confident learners with four routers and a second packet definition. Homework: name one advantage of splitting a file into packets over sending the whole file.