A Maximum Transmission Unit (MTU) is the largest packet size or frame that can be sent along a link. The MTU is specified in octets and is used by TCP to determine the maximum size of a packet per transmission. A large MTU provides less overhead because packet headers and acknowledgments are not consuming space and bandwidth. However, this could lead to retransmissions or drops if a hop does not support it. On the contrary, a small MTU is not as efficient as overhead increases with packet headers and acknowledgments.
Generally speaking, the MTU across the Internet is 1,500 bytes. As such, most devices limit packet size to roughly 1,472 bytes, allowing for additional overhead and remaining under the 1,500-byte limit. Additional overhead might be added as the packet goes through different hops. The IEEE 802.3 standard also specifies 1,500 bytes as the standard payload.