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:
10000011 10010111 this binary number is 33687 decimal (base 10)
01101010 10111001 this binary number is 27321 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 10000011 10010111 and 01101010 10111001 = 11101110 01010000
2. The internet checksum is the one's complement of the sum: 11101110 01010000 = 00010001 10101111
That's incorrect
That's correct
The answer was: 11101110 01010000
The answer was: 00010001 10101111