IP fragmentation

IP fragmentation is an Internet Protocol (IP) process that breaks packets into smaller pieces (fragments), so that the resulting pieces can pass through a link with a smaller maximum transmission unit (MTU) than the original packet size.

Applications are recommended to refrain from sending packets larger than 576 bytes unless they have prior knowledge that the remote host is capable of accepting or reassembling them.

[4] Fragmented packets with a total reassembled size larger than 1500 bytes may optionally be silently discarded.

[5] Thus, senders typically use two approaches to decide the size of IP packets to send over the network.

As of 2020[update], IP fragmentation is considered fragile and often undesired due to its security impact.

An example of the fragmentation of a protocol data unit in a given layer into smaller fragments.
The fragmentation algorithm in IPv4.
An example of IPv4 multiple fragmentation. The fragmentation takes place on two levels: in the first one the maximum transmission unit is 4000 bytes, and in the second it is 2500 bytes.