What's the matter?

MTU (Maximum Transmission Unit) – the maximum amount of information (no more than 1500 bytes) that can be sent at once through a network interface without the need for prior compression or fragmentation.

Network protocols MTU

Network protocols also have an MTU value. To avoid splitting the sent file into fragments when the permissible limit is exceeded, the limit is lowered by 20 bytes in advance.

Protocols whose function is to transfer data are programmed for a maximum packet size of no more than 65535. The main task of the IP layer is to divide messages that exceed the size limit into smaller ones. This creates several service fields, which reassemble the packet into the original file after the transfer is complete.

When the IP receives a transmitted data packet, it begins to check whether it complies with the preset size. It must not be larger than the MTU value of the channel level. At the same time, the “Do not fragment” bit must be set to 0. If the check reveals that the limit has been exceeded, the blocks are broken down into smaller ones.