[$] So you think you understand IP fragmentation? What is IP fragmentation, why is it important, and do people understand it? The answer to that last question is "not as well as they think". This article will also answer the rest of those questions and introduce https://valerieaurora.org/fragquiz.html , a game that I wrote to allow players to guess how IP packets will behave when they are too large for the network. As evidence that IP fragmentation is not well-understood, a room full of networking experts played fragquiz and got a score that was nowhere close to perfect. In addition, I will describe a new algorithm for fragmentation avoidance, which some colleagues and I developed, that helped motivate development of fragquiz. https://lwn.net/Articles/960913/