Dictionary · Networking Fundamentals
MTU
MTU — Maximum Transmission Unit
Data units · Intermediate
The largest packet or frame payload a link can carry. A common Ethernet value is 1500 bytes. Larger packets must be fragmented or dropped if the sender cannot reduce them.
If a packet is bigger than the next link allows, it has to be split or discarded. Path problems sometimes show up as small tests succeeding while large transfers fail.
Example: A tunnel reduces the usable size below 1500 bytes, so hosts must learn a smaller limit or the tunnel must adjust packets.
Common misconception
- The familiar 1500-byte Ethernet value is not a universal Internet limit. Tunnels and other links can be smaller.