Attack source tracing identifies attacks by sampling received packets. A proper packet sampling ratio can reduce the errors in attack packet identification and packet rate calculation. A small sampling ratio makes the attack source tracing result accurate, but increases CPU usage.
For example, when the sampling ratio is set to 1, the attack source tracing result is accurate, but the CPU usage is high because every packet is analyzed. Therefore, balance between the attack defense precision and CPU usage when setting a sampling ratio.