MTU

The MTU (Maximum Transmission Unit) is the size of the largest datagram that can be sent over a network.

If a datagram is larger than an MTU, the datagram must be fragmented into multiple smaller datagrams.

Default MTU Sizes

Most network technologies have default MTU sizes which may be changed by the network administrator.

The term PMTU (Path MTU) is sometimes used to describe the MTU along an entire network path. The PMTU will always be equal to the smallest MTU along the entire path which the datagram must travel.