MTU Maximum Transmission Unit
Through the definition of the above MAC package, we now know that the standard Ethernet frame can transmit the maximum amount of data to reach the bytes, which is called the MTU (Maximum transmission unit, the maximum transmission unit). You have to be aware that the MTU of each network interface is different, so sometimes you will see the MTU of 1492 bytes on some web articles. However, on the Ethernet network, the standard is defined as the bytes.
IP packets can be up to 65535 bytes, bigger than the MTU! Since the gift (IP) is bigger than the box (MAC), how can it be put in? So, IP packets can be disassembled, and then put in the MAC Ah! Wait until the data is uploaded to the destination, and the host of the destination assembles him back. So, if the MTU can be larger, then the IP packet disassembly situation will be reduced, the packet and packet delivery between the waiting time (the number of times) will be reduced, you can increase the use of network bandwidth!
For this purpose, so Gigabit Ethernet network media to support Jumbo frame! This Jumbo frame is generally defined to 9000bytes. Then you would say, in that case, can our MTU be changed to 9000bytes? Does this reduce the disassembly of data packets to increase network usage? Yes, and you can change the MTU on a Linux system! However, if you consider the entire network, then we do not recommend that you modify this value. Why is it?
Does our packet always need to run on the Internet? You can't confirm that all the Internet media support that big MTU, right? If your 9000 bytes packet passes through a network media that does not support Jumbo frame, it is better that the network media (such as switch/router, etc.) will actively help you to reorganize and transfer, Close to the possible direct return of the package is invalid and discarded ~ This time can be embarrassing ~ So, MTU set to 9000 this kind of thing, probably only in the internal network environment to do ~ For example, a lot of internal cluster system (cluster) to their internal network environment MTU set to 9000, but the external adapter card can still be the original standard 1500 Oh! ^_^
That is, no matter how big your network media supports the MTU, you have to take into account all the network media that your packet needs to pass to the destination, and then decide your MTU setting. Because of this, we do not recommend that you modify the MTU of the standard Ethernet network!
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MTU Maximum Transmission Unit
