Maximum transmission unit.
(1) (Maximum Transmission Unit, Maximum Transfer Unit) The largest frame size that can be transmitted over the network. For example, an Ethernet MTU is 1,500 bytes. Messages longer than the MTU must be divided into smaller frames. The layer 3 network protocol, typically IP, extracts the MTU from the layer 2 data link protocol such as Ethernet, and fragments the messages into that frame size so that they can travel over the lower layer. See path MTU.
Maximum Transmission Unit. In Internet Protocol version 6 (IPv6), all networks must support a packet of at least 1280 octets. The recommendation, however, is that all networks be configured to support an MTU of 1500 octets or greater in order to support encapsulation of Ethernet payloads without incurring fragmentation. See also encapsulate, Ethernet, fragmentation, IPv6, octet, packet, and payload.