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Internet, web and networks I · Lesson 08 / 10

Why does a page take time?

A small file can take time; a large file can arrive quickly. Separate waiting time from transfer.

Learning paths14 min

Let's discover together

  1. 1

    Latency describes delay; transfer rate describes data per time. Milliseconds (ms) and megabytes per second (MB/s) measure different things. Mbps uses bits; here we use decimal MB and MB/s.

  2. 2

    Fictional model: fixed wait of 100 ms, a 2 MB file and constant rate of 4 MB/s. Transfer = 2 ÷ 4 s = 500 ms; total = 600 ms. At 8 MB/s, the total is 350 ms, not 300.

  3. 3

    A usable cached copy can avoid a new transfer. Revalidation asks whether a copy is still usable; 304 allows reuse without a new body. Not every request uses cache, and no-store requests that the response not be stored.

  4. 4

    Real networks vary and involve reused connections, concurrency and processing. Do not treat the model as a speed test. One measurement does not prove a cause; compare observations under similar conditions.

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✦
YOUR MISSION

Calculate a simple model and recognize caching and measurement limits.

Now it's your turn

Discovery workshop

Observe before concluding

Use only the model: wait 100 ms, file 2 MB, first 4 MB/s, then 8 MB/s.
Build your answers and check when you are ready.
A moment to understand

Did this calculation measure your internet?

I need a hint

Return to the evidence: what was observed and what is still unknown?

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Take it with you

Calculate the same model for 1 MB at 4 MB/s. Then explain why neither result measures your home connection.

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