Net.ipv4.tcp_rmem: TCP Receive Buffer Tuning for Linux

The parameter 'net.ipv4.tcp_rmem' is a kernel parameter that determines the minimum, default, and maximum size of the receive buffer for a TCP socket. The receive buffer is a memory area used by the kernel to store incoming data from a network connection until the application is ready to read it.

The 'net.ipv4.tcp_rmem' parameter is a three-value tuple that specifies the minimum, default, and maximum size of the receive buffer, in bytes. The format of the tuple is as follows:

'net.ipv4.tcp_rmem = min_size default_size max_size'

The default value of the parameter on most Linux systems is:

'net.ipv4.tcp_rmem = 4096 87380 6291456'

This means that the minimum receive buffer size is 4 KB, the default size is 87,380 bytes, and the maximum size is 6 MB.

The value of the 'net.ipv4.tcp_rmem' parameter can be adjusted to optimize the performance of TCP connections, depending on the network conditions and the type of application. Increasing the size of the receive buffer can help reduce packet loss and improve throughput, but it also increases memory usage and can lead to bufferbloat. Conversely, decreasing the buffer size can reduce memory usage but may result in slower performance and increased packet loss.