title: Calculating a 8-bit internet checksum
body: <p><a href="https://i.stack.imgur.com/9IPjU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9IPjU.png" alt="enter image description here"></a></p>
  
  <p>How would I compute the 8-bit internet checksum of this data? </p>
  
  <p>From what I've found so far, to compute the checksum you would add the sums of each of the data parts and then use the 1st compliment on this result sum. But when I try this I get:</p>
  
  <p><code>00000011</code> + <code>00000100</code> = <code>00000111</code>(x = 3 + 4)</p>
  
  <p><code>00000111</code> + <code>00000101</code> = <code>00001100</code>(y = x + 5)</p>
  
  <p><code>00001100</code> + <code>00000110</code> = <code>00010010</code>(y + 6)</p>
  
  <p>Applying the 1st compliment would get me: <code>11101101</code> which is not the correct result comparing with what is expected above.</p>
  
  <p>Is my method approaching this calculation wrong?</p>