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:
11110110 00001110 this binary number is 62990 decimal (base 10)
00110101 11110001 this binary number is 13809 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 11110110 00001110 and 00110101 11110001 = 00101100 00000000
2. The internet checksum is the one's complement of the sum: 00101100 00000000 = 11010011 11111111
That's incorrect
That's correct
The answer was: 00101100 00000000
The answer was: 11010011 11111111