DTR/DSR Flow Control is a flow control method that is part of the RS232 standard. It uses two pins on the RS232 connector, DTR (Data Terminal Ready) and DSR (Data Set Ready). These two control lines allow the receiver and the transmitter to signal each other about their readiness to communicate.

When the transmitting device is ready to send data it raises its DTR line to indicate that it is ready. The receiving device then raises its DSR line to confirm that it is ready to accept the data. This back-and-forth signaling makes sure that the data will only be sent when both of the devices are prepared to handle it and have signaled this to each other.

This type of flow control is good as it helps prevent data loss or buffer overflow by ensuring that the receiver is ready before transmission begins, which makes it a reliable way to manage data transfer between devices.