Efficiency versus Delay for a Sliding-Window Data-Link Control Protocol

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This Demonstration gives the efficiency of a sliding-window data-link control protocol as a function of the delay between a sender and a receiver. The link rate, frame (or packet) size and window size (in frames) are adjustable parameters. This link is assumed to be error free.


Data-link control protocols are used to ensure reliable and efficient data transmission in computer networks by managing the flow of data between a sender and a receiver. Sliding-window data-link control protocols operate in two regimes: the large and small window. The efficiency is 100% in the large-window regime and decreases as the delay increases in the small-window case. The threshold is a function of the delay, link rate, frame (or packet) size and window size (in frames). This Demonstration showcases the threshold effect and how it changes with the adjustable parameters.


Contributed by: Victor S. Frost (August 25)
(University of Kansas)
Open content licensed under CC BY-NC-SA


The following parameter definitions and relationships are used:

is the link rate (b/s),

is the effective transmission rate in bits/sec = ,

is the efficiency,

is the one-way delay (sec),

is the window size,

is the frame size (bits).

If , then (large-window case).

If , then (small-window case).


[1] A. Leon-Garcia and I. Widjaja, Communication Networks: Fundamental Concepts and Key Architectures, 2nd ed., Boston: McGraw Hill, 2004.

[2] A. Tanenbaum and D. J. Wetherall, Computer Networks, 5th ed., Boston: Pearson Prentice Hall, 2011.


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