Maximum transmission unit

The maximum size of a network-layer packet that a link can carry in one frame without fragmentation. It depends on the link technology and configuration.

IP fragmentation: The division of an IP packet into smaller fragments so it can cross a link with a lower MTU. IPv4 routers may fragment packets that exceed an outgoing link’s MTU.
Internet Protocol: The network-layer protocol suite that carries datagrams across interconnected networks. MTU is defined against the size of an IP packet carried by a link.
Jumbo frame: An Ethernet frame carrying a payload larger than the standard Ethernet MTU of 1,500 bytes. Jumbo frames raise the usable MTU when all relevant network equipment supports them.
Frame size: The total number of bytes in a link-layer frame, including its header and any trailer. Frame size may include link-layer fields that are not counted in the network-layer MTU.
Path MTU discovery: A method for finding the smallest MTU along a route between two network endpoints. It lets senders size packets for the narrowest link without relying on router fragmentation.
IP packet: A network-layer data unit containing an IP header and payload, routed between hosts. Its total size is compared with the link’s MTU.
Ethernet: A family of wired networking technologies that carries frames over local-area networks. Its common 1,500-byte MTU is a familiar baseline for network configuration.
Bandwidth-delay product: The amount of data that can be in transit on a link, calculated from bandwidth and round-trip delay. It limits efficient data in flight, not the size of an individual packet.
Internet Control Message Protocol: A network-layer protocol used by hosts and routers to exchange control and error messages. ICMP messages can report that a packet exceeds a link’s MTU.
Ethernet frame: A link-layer unit that carries a payload and framing information across an Ethernet network. The Ethernet payload carries the IP packet whose size must fit the link MTU.

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