This read-only INTEGER (0..3136000) reports the port's clock rate in bits per second, defaulting to 1544000 for loopback. An admin reads this to verify the serial port is actually running at the bit rate expected for the circuit. For example, a port unexpectedly reporting the loopback default of 1544000 bps instead of the provisioned production rate would tell an admin the port may still be sitting in a loopback or test configuration.