A Frame Check Sequence (FCS) is the 4-byte field at the end of an Ethernet frame. It helps detect whether the frame was corrupted during transmission. section 6.2.4
The error-checking process works as follows:
- The sender calculates a checksum using an algorithm and appends it as the FCS. section 6.2.4
- The destination calculates its own checksum using the same algorithm. section 6.2.4
- Matching checksums indicate intact data; different checksums cause the receiver to discard the frame. section 6.2.4
Transmission interference
If electromagnetic interference changes bits while a frame is in transit, the receiver calculates a different checksum and discards the corrupted frame. section 6.2.4
