MTU: the maximum capacity of a connection for data packets.

MTU stands for maximum data unit, and is generally used to describe the largest packet size that can be sent over a network connection.

While they are not the same thing, and are not necessarily directly connected, MTU and bandwidth often correlate with each other.

This happens simply because both are defined by size. MTU, after all, defines just how big of a piece of data can fit in a connection, and bandwidth is a measure of how much can fit in a given time; it makes sense, then, that a connection with a large MTU can fit large amounts of data, thus lending itself to a higher bandwidth with its high MTU.

So what happens when data is too big to fit through the connection, i.e. the data packet is bigger than the MTU?

Let us assume a connection has an MTU of 1500 bytes (the largest packet of data that can fit through the connection is 1500 bytes) and we send through a 15 KB (15000 bytes).

So what happens to the file now? It still goes through, but in pieces determined by the network.

In this case, our hypothetical computer breaks it into 1000 byte pieces (15 of them) each of which has a 40 byte header sent automatically to help the receiving connection assemble it correctly.

This happens automatically, and the only way to notice is the small decrease in connection speed as it goes through all of these motions.

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