Knowledge checks


Congestion control versus flow control.



Consider the five images below.  Indicate which of these images suggest the need for flow control (the others would suggest the need for congestion control).




 

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1/5

Two congested senders.



Consider the figure below, which shows the application-to-application throughput achieved when two senders are competing at a shared bottleneck link.  Suppose that when the overall arrival rate,  lambdain' (for each sender) is close to R/2, the throughput to the application layer (at each receiver), lambdaout, is equal to 0.8 *  lambdain'.

What fraction of the packets transmitted at the sender are retransmissions?




 

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2/5

Network-assisted or end-end congestion control?



Which of the following actions are used in network-assisted congestion control (say versus end-end congestion control) to signal congestion. Check all that apply.




 

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3/5

Network-assisted or end-end congestion control (2)?



Which of the following actions are associated with end-end congestion control (say versus network-assisted congestion control). Check all that apply.




 

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4/5

Different approaches towards congestion control.



Use the pulldown menu to match a congestion control approach to how the sender detects congestion.



Question List:
Answer List:
  1. delay-based
  2. network-assisted
  3. end-end

 

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5/5

We gratefully acknowledge the programming and problem design work of John Broderick (UMass '21), which has really helped to substantially improve this site.

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