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:
01100000 11101000 this binary number is 24808 decimal (base 10)
01011000 11010101 this binary number is 22741 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 01100000 11101000 and 01011000 11010101 = 10111001 10111101
2. The internet checksum is the one's complement of the sum: 10111001 10111101 = 01000110 01000010
That's incorrect
That's correct
The answer was: 10111001 10111101
The answer was: 01000110 01000010