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Recall that UDP and TCP use 1s complement for their checksums. a. Suppose you ha

ID: 3629205 • Letter: R

Question

Recall that UDP and TCP use 1s complement for their checksums.

a. Suppose you have the following three 8-bit bytes: 10010101, 11000101, 10000101. What is the 1s complement of the sum of these 8-bit bytes? (Note that although TCP and UDP use 16-bit words in computing the checksum, for this problem you are being asked to consider 8-bit sums.) Show all the work. (6 points)

b. Why is it that UDP takes the 1s complement of the sum; that is, why not just use the sum?

c. With the 1s complement scheme, is it possible that a 1-bit error will go undetected? (If your answer is “yes”, please give an example; if your answer is “no”, please explain why).

d. Is it possible that a 2-bit error will go undetected? Please justify your answer.

Explanation / Answer

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