Computer networksLesson 2 of 2 in the course Transport layer

Network Congestion: Effects, Control, and Mitigation

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Network congestion occurs when traffic demands more processing or transmission capacity than a network node or link can provide. This lesson explains how limited capacity affects service and why congestion can sometimes lead to a much more serious condition: congestive collapse.

Network resources are limited. Routers have finite processing capacity, and links can carry only a certain amount of data per second. When many flows compete for those resources, packets may wait in queues or be discarded.

All flashcards

What is offered load?
The traffic that users and applications attempt to send into a network.
What is useful throughput?
The traffic successfully delivered through a network.
How does flow control differ from congestion control?
Flow control prevents a sender from overwhelming a particular receiver; congestion control limits traffic entering shared network resources.
What is max-min fairness?
An allocation in which no flow's rate can be increased without reducing the rate of another flow that has an equal or lower rate.
What is a link price in a congestion-control model?
A value associated with a link's capacity constraint that can guide the sending rates of flows using that link.

Quiz questions

  1. What problem does flow control address, as distinct from congestion control?Answer: It prevents a sender from overwhelming a particular receiver.
  2. How does Random Early Detection (RED) signal building congestion?Answer: It probabilistically drops packets as the average queue length rises.
  3. What does Explicit Congestion Notification (ECN) use to signal congestion?Answer: A packet mark, with support from the communicating hosts.
  4. What is the purpose of admission control?Answer: To refuse a new connection when accepting it could make congestion likely.
  5. Why can wireless packet loss lead TCP to reduce its sending rate unnecessarily?Answer: TCP may interpret losses caused by interference as evidence of congestion.

Based on the Wikipedia article Network congestion, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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