Installation guide

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delayed_ack=0-1000
The time, in milliseconds, to delay sending ACK packets in response to
received data for the specified range of network services. The default is
200 milliseconds.
Setting this option to 0 (zero) sends an ACK packet back acknowledge the
received data immediately. Setting it to any other value means that the
ACK packet will be sent after the specified time. If the network services
generate new data during that time, the ACK packet will be sent along
with the data packet.
You can use this setting to avoid congestion and reduce network traffic,
However, do not change this option from its default setting unless you
have a solid understanding of network services and data transmission, or
have been instructed to make the change.