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Transmission delay

Transmission delay is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Transmission delay rather than just read about it. In short: In a network based on packet switching, transmission delay (or store-and-forward delay, also known as packetization delay or serialization delay) is the amount of time required to push all the packet's bits into the wire. In other words, this is the delay caused by the data-rate of the link.

Key takeaways

  • Transmission delay belongs to computer science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Transmission delay to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Transmission delay from memory before moving on to harder problems.

Reference excerpt

In a network based on packet switching, transmission delay (or store-and-forward delay, also known as packetization delay or serialization delay) is the amount of time required to push all the packet's bits into the wire. In other words, this is the delay caused by the data-rate of the link. Transmission delay is a function of the packet's length and has nothing to do with the distance between the two nodes. This delay is proportional to the packet's length in bits. It is given by the following formula:

D T = N / R {\displaystyle D_{T}=N/R} seconds where:

D T {\displaystyle D_{T}} is the transmission delay in seconds;

N {\displaystyle N} is the number of bits;

R {\displaystyle R} is the rate of transmission (say, in bits per second). Most packet switched networks use store-and-forward transmission at the input of the link. A switch using store-and-forward transmission will receive (save) the entire packet to the buffer and check it for CRC errors or other problems before sending the first bit of the packet into the outbound link. Thus, store-and-forward packet switches introduce a store-and-forward delay at the input to each link along the packet's route.

See also End-to-end delay Processing delay Queuing delay Propagation delay Network delay Round-trip delay

References Kurose, J.F; Ross, K.W. (2013). Computer Networking: A Top-down Approach. Pearson. ISBN 9780132856201.

External links Java Applet Network Delays

Worked examples

Example 1 — a first encounter with Transmission delay

Start with the simplest possible case. Write down what Transmission delay claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Transmission delay before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Transmission delay ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Transmission delay

In research
Transmission delay appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Transmission delay in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Transmission delay is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer network stubs, Computer networks engineering, so understanding it makes those chapters shorter.
In everyday life
Look for Transmission delay outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Transmission delay in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Transmission delay means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Transmission delay out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Transmission delay in simple terms?

In a network based on packet switching, transmission delay (or store-and-forward delay, also known as packetization delay or serialization delay) is the amount of time required to push all the packet's bits into the wire. In other words, this is the delay caused by the data-rate of the link.

Why does Transmission delay matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Transmission delay?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Transmission delay.

Tags

  • Computer network stubs
  • Computer networks engineering

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