This question already has an answer here:
I just had an answer deleted by @Flexo that meets the criteria "barely more than a link to an external site". Those with sufficient privileges can see it here: different between CRC8 , CRC16 and CRC32?
All of the questions posed are answered completely, and much more, in the tutorial that I linked to. In my opinion, that is an excellent and complete answer, and it is very useful for others looking at those sorts of questions to be directed to that tutorial. In fact the questioner said exactly that: "Thanks for the link. It is very useful. I didnt find any good links like this."
So basically, I disagree with the criteria: "barely more than a link to an external site" being applied without thought or inspection. Such answers should be permitted when they are in fact answers and useful to others. There is no value in repeating the tutorial or parts of the tutorial in the answer.