Modern and performance/server grade network interface have the capability of using transmit and receive buffer description ring into the main memory. They use direct memory access (DMA) to transfer packets from the main memory to carry packets independently from the CPU.

The usual default buffering values for regular desktop NICs are 256 or 512 bytes. High performances NICs can achieve up to 4096 and/or 8192 bytes.

To view the capability and the current values of your interface, you’ll need “ethtool”. Simply do the following command :

 ethtool -g eth0

This will output something like this :

 Ring parameters for eth0:
Pre-set maximums:
RX: 4096
RX Mini: 0
RX Jumbo: 0
TX: 4096
Current hardware settings:
RX: 256
RX Mini: 0
RX Jumbo: 0
TX: 256 

We can see here that both RX and TX values are set to 256 but the interface have the capability of 4096 bytes.

To increase the buffers, do the following :

 ethtool -G eth0 rx 4096 tx 4096