Networks: latency, throughput and layered delivery
Đã giới thiệu| English | Ý nghĩa |
|---|---|
| throughput/ˈθruːpʊt/ | tăng lưu lượng |
| latency/ˈleɪtənsi/ | độ trễ |
What would explain this observation?
- A small message can arrive late on a high-bandwidth link. Capacity and delay measure different properties.
Build the model
- Packets carry addressed data through a network.
- A layered model separates responsibilities such as application meaning, transport delivery and network routing.
- Bandwidth describes capacity; throughput 吞吐量 is the achieved data rate; latency 延迟 is delay.
- throughput: Achieved rate of useful data transfer.
- latency: Delay experienced in communication.
Why can completion exceed file-size divided by link rate?
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Size/rate assumes the link carries only your file at full speed with no protocol work. Headers, acknowledgements, queueing behind other traffic and propagation delay all add time, so real completion is slower.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Transmission time depends on data size and rate.
- Total delay may also include propagation, processing and queueing.
- Encryption protects content under its assumptions but does not remove congestion or every metadata exposure.
In the lab: Trace a message route using a documented local model. Record payload size, units and measured time. Use school-approved networks and synthetic messages; do not scan or intercept another user traffic.
Which two habits make the investigation or model in this case more defensible?
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Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: an 8 megabit file crosses a 2 megabit/s link.
- Ideal transmission time = size/rate = 8/2 = 4 s.
- Protocol overhead, other users and latency can make observed completion slower.
Your turn: A 12 megabit file crosses a 3 megabit/s link. Calculate ideal transmission time.
A 12 megabit file crosses a 3 megabit/s link. Calculate ideal transmission time.
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The result is 4 s. Known: 12 megabits on a 3 megabit per second link. Use ideal time = size / rate. Time = 12/3 = 4 s. This is the lower bound before overhead and sharing.
Check the conclusion and its limits
- A megabyte is eight megabits before considering overhead.
- A faster rated link does not guarantee low latency or secure endpoints.
Not true: A high-bandwidth connection guarantees zero latency. Bandwidth is capacity - how much can flow per second. Latency is delay - how long one signal takes. A high-capacity link can still have high latency, for example a satellite connection.
- Packets carry addressed data through a network.
- Transmission time depends on data size and rate.
- Watch for: A megabyte is eight megabits before considering overhead.
Bandwidth is capacity - how much can flow per second.
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True. Bandwidth is capacity - how much can flow per second. Latency is delay - how long one signal takes. A high-capacity link can still have high latency, for example a satellite connection.
Achieved rate of useful data transfer: write the technical term.
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throughput means Achieved rate of useful data transfer.