The physical link: free-recall review
Free-recall prompts across the physical-link unit. Answer each in your own words first, then reveal the model answer and compare.
Retrieval beats re-reading. For each prompt, say or write a full answer from memory before you open the model answer — the effort of recall is what makes the numbers and mechanisms stick.
Reconstruct the unit’s spine — the latency floor, the Shannon ceiling, bandwidth-delay product, the bufferbloat mechanism, why RoCE needs a lossless fabric, and the three-question model — without looking back at the lessons.
- 01Why doesn't buying more bandwidth reduce page-load latency, and what actually does?
- 02State Shannon's theorem and the engineering consequence of its two terms.
- 03What is the bandwidth-delay product and why does a high-BDP path need window scaling?
- 04Explain bufferbloat — the mechanism, the symptom, and why a faster uplink does not fix it.
- 05Why does RoCE require a lossless Ethernet fabric, and what two mechanisms provide it?
- 06What three questions decode any unfamiliar link technology, and what does each tell you?
If you could reconstruct each answer from memory, you hold the unit’s spine: bandwidth and latency are independent (only a shorter path or faster medium lowers the floor); Shannon caps bits/s with a linear B term and a logarithmic SNR term; BDP says how many bytes must be in flight and window scaling lets TCP get there; bufferbloat is hidden congestion from oversized buffers, cured by AQM not by more bandwidth; RoCE trades the kernel for a lossless fabric guarded by PFC and ECN; and any new link technology yields 80% of its behaviour to medium, encoding, and frame format.
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