An Internet Protocol (IP)/Internet Control Message Protocol (ICMP) fragmentation DDoS attack is a common form of volumetric denial of service (DoS) attack. In such an attack, datagram fragmentation mechanisms are used to overwhelm the network.

IP fragmentation occurs when IP datagrams are broken apart into small packets, then transmitted across a network, and finally reassembled into the original datagram as part of normal communications. This process is necessary to meet size limits that each network can handle. Such a limit is described as a maximum transmission unit (MTU).