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What is IP Fragmentation?

When data travels across a network, it moves in discrete chunks called packets. Every network has a limit on how large those packets can be, known as the Maximum Transmission Unit (MTU). IP fragmentation is what happens when a packet exceeds that limit and needs to be split into smaller pieces to make it to its destination. 

Each fragment travels independently and may take a different path to the destination, where they’re reassembled in the correct order. If any fragment fails to arrive, the entire original packet has to be transmitted again. 

Fragmentation can cause problems, like reducing network performance and creating complications for firewalls and other security tools. This is because of the challenge of inspecting traffic that arrives in pieces. For this reason, modern networks generally try to avoid it by determining the optimal packet size before sending via a process known as path MTU discovery.