Rejection means the number of rejected shares by mining pool during the process of submitting the shares to the mining pool. It may appear due to many factors such as network fluctuations. Rejection rate is the ratio of the total number of rejections to the sum of the total number of shares submitted. The smaller the ratio, the higher the efficiency of miners.
Generally speaking, rejection rate of mainstream currency is less than 1%. However, for some Altcoins, rejection rate will be relatively high due to the small number of nodes.
If rejection rate is high, it is recommended to check the network performance. Common scenarios include:
1) The rejection rates of all routers or switches are exceeding the standard: it is recommended to check the network overall, and try to replace the router or switch.
2) Individual machine exceeds the standard: it is recommended to replace the network cable and network port connected to the machine.