A question popped into my head today and after a quick few searches on google, I have no idea. When a device is sent a frame there is a layer 1 header/preamble saying the length and layer 2 protocol (I think please correct me if I'm wrong), but how does the NIC know where to start reading the data from? If it starts reading from the first 1 what happens if that 1 was just noise on the line? If any clarification is needed please ask. (Also no idea what tags to put for this.)
Ethernet sends seven octets of preamble (
10101010) to synchronize, and then a one octet SoF (Start of Frame) delimiter (
10101011). The next bit is the first bit of the frame. The frame has a four octet FCS (Frame Check Sequence) that is a CRC, and if the received CRC doesn't match the calculated CRC, then the frame is dropped as damaged.