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 01000111 this binary number is 54343 decimal (base 10)
11010101 00101110 this binary number is 54574 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 11010100 01000111 and 11010101 00101110 = 10101001 01110110
2. The internet checksum is the one's complement of the sum: 10101001 01110110 = 01010110 10001001
That's incorrect
That's correct
The answer was: 10101001 01110110
The answer was: 01010110 10001001