The transmit end shifts M leftward by four bits, and divides the resulting number by P. Any alternatives would be greatly appreciated. Right now all I can come up with is remaking the VM and then deleting (forcefully if need be) the old one, or god forbid formatting my HDD. The following example illustrates the CRC calculation process:Īssume that g(x) is CRC-4, which equals X 4 + X + 1, and the source data M is 10110011. Chkdsk was also unable to find any errors. If there is no remainder, no error occurs during data transmission. When receiving the data, the receive end divides the data by P using modulo-2 division.
#Bittorrent data error cyclic redundancy check code
The transmit end appends the R-bit check code to the original data and sends the data to the receive end.If the check code length is less than R bits, zeros are prepended to it to ensure that the length is R bits. Then, a modulo-2 division operation (an XOR operation) is performed to divide the (K+R)-bit number obtained after the addition of zeros by P, and cyclic calculation is performed until an order of a remainder is less than R.The transmit end first appends R zeros to the original K-bit data, which is equivalent to shifting the original data to the left by R bits.Before communication, the transmit end and receive end agree on a divisor P, that is, the value of a polynomial.Obtaining and checking the check code by using the divisor consist of the following steps: The value of these polynomials is the divisor of modulo 2 division.
For example, a standard Ethernet frame ends with a 4-byte frame check sequence (FCS) for error detection. Therefore, CRC has become the most commonly used error detection method in the computer information and communications fields. CRC has advantages over other error detection methods in terms of speed, cost, and correctness. Wesley Peterson, a mathematician and computer scientist, in 1961. The receive end performs the same calculation to check whether the data changes.ĬRC was first proposed by W. Their implementation is similar: The transmit end calculates a check code for data using a certain algorithm, and sends the check code and data to the receive end. There are many error detection methods, such as parity check, checksum check, and CRC check. To resolve this problem, the receive end needs to perform error detection on the received data and accepts the data only when it is correct. Bit errors (0 changed to 1 or 1 changed to 0) may occur in transmitted data due to transmission media faults or external interference, causing incorrect data on the receive end.