| 摘要 |
An intermediate station produces, for an altered packet that includes multiple cells from a received packet and one or more altered cells that are substituted for the corresponding cells of the received packet, a DELTA -CRC remainder that is combined with the CRC remainder included in the received packet to produce a CRC remainder for the altered packet. The station first produces for each altered cell a bit pattern that has zeros in the bit positions in which the bits of the altered cell and the corresponding received cell match and ones in the bit position in which the two cells do not match. The station next encodes the bit patterns in accordance with the CRC code and produces corresponding DELTA -CRC values. It then manipulates the DELTA -CRC values to produce the DELTA -CRC remainder, and combines the DELTA -CRC remainder with the CRC remainder in the received packet. The result is the CRC remainder for the altered packet.
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