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:


   01000001   00010010      this binary number is 16658 decimal (base 10)

   00101011   11001110      this binary number is 11214 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




Solution


1. The sum of 01000001 00010010 and 00101011 11001110 = 01101100   11100000

2. The internet checksum is the one's complement of the sum: 01101100   11100000 = 10010011   00011111



That's incorrect

That's correct

The answer was: 01101100   11100000

Question 1 of 2

The answer was: 10010011   00011111

Question 2 of 2

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