Interactive end-of-chapter exercises

Computing an Internet checksum

Consider the two 16-bit words (shown in binary) below. Recall that to compute the Internet checksum of a set of 16-bit words, we compute the one's complement sum [1] of the two words. That is, we add the two numbers together, making sure that any carry into the 17th bit of this initial sum is added back into the 1's place of the resulting sum); we then take the one's complement of the result. Compute the Internet checksum value for these two 16-bit words:

   11010100   00110011      this binary number is 54323 decimal (base 10)

   11101100   00010100      this binary number is 60436 decimal (base 10)

Question List

1. What is the sum of these two 16 bit numbers? Don't put any spaces in your answer

2. Using the sum from question 1, what is the checksum? Don't put any spaces in your answer


1. The sum of 11010100 00110011 and 11101100 00010100 = 11000000   01001000

2. The internet checksum is the one's complement of the sum: 11000000   01001000 = 00111111   10110111

That's incorrect

That's correct

The answer was: 11000000   01001000

Question 1 of 2

The answer was: 00111111   10110111

Question 2 of 2

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