MTU (Maximum Transmission Unit) is an extremely large (no more than 1,500 bytes) amount of information that can be sent at a time through a network interface without the need for pre–compression or fragmentation.
MTU Network Protocols
Network protocols also have an MTU value. In order to avoid dividing the sent file into fragments when exceeding the permissible limit, the limit is lowered by 20 bytes in advance.
The protocols, whose function is to transmit data, are programmed for a maximum packet volume of no more than 65535. The main task of the IP layer is to divide the message exceeding the volume into smaller ones. In this case, several service fields are created, which, after the transfer is completed, reassemble the package into the source file.
At the moment when the IP receives the forwarded data packet, the verification of its compliance with the preset size begins. It should not be greater than the MTU value of the channel layer. In this case, the value of the “Do not fragment” bit must be set to 0. If the limit is exceeded as a result of the check, the blocks are divided into smaller ones.