Frame check sequence: 4-byte field that contains the cyclic redundancy check (CRC)
value. The CRC computation is based on the following fields: source address,
destination address, QTag prefix, length/type, LLC data and PAD (that is, all fields
except the preamble, SFD). The generating polynomial is the following:
The CRC value of a frame is computed as follows:
● The first 2 bits of the frame are complemented
● The n-bits of the frame are the coefficients of a polynomial M(x) of degree (n – 1). The
first bit of the destination address corresponds to the xn – 1 term and the last bit of the
data field corresponds to the x0 term
● M(x) is multiplied by x32 and divided by G(x), producing a remainder R(x) of degree
≤ 31
● The coefficients of R(x) are considered as a 32-bit sequence
● The bit sequence is complemented and the result is the CRC
● The 32-bits of the CRC value are placed in the frame check sequence. The x32 term is
the first transmitted, the x0 term is the last one
看得很晕,不知道有谁可以讲解下。。