1- We take the original data and pass it trough a coding schem (EDCE Codex) generating EDC bits

• The data and the EDC bits are concatenated and passed through the network
• The receiving end apllies the same codex, if it matches the EDC and then it passes the error check, otherwise there is an error
• Is not 100% reliable, some protocols may rarely miss some errors
• Bigger EDC fileds haver better chances at error detection

Parity Checking

-> Single Bit Parity: detects single bit errors - compute parity of d received bits - compares with received partity bit - if different than erros detected

-> Two Dimensional Bit Parity: detects and corrects single bit errors

Internet Checksum

• Detect errors in transmitted segment

Sender: -> treat contents on UDP segment as a 16-bit integers -> Checksum: addition of segment content -> Belongs in UDP checksum field

Receiver: -> computes checksum of received segment -> Checks if matches or not (being equal doesn't mean that there are more errors)

CRC

• CRC (Cyclic Redundancy Check) is an error-detection method used in networks and digital systems to verify if data transmitted has been corrupted during transmission.
• Before sending a block of data, the sender calculates a value called the CRC, based on the content of the data.
• This value is calculated using mathematical operations from binary algebra (polynomial division) and is appended to the end of the data.
• The receiver, upon receiving the data, performs the same calculation on the received data and compares it with the received CRC.
• If the values do not match, it means an error occurred during transmission.
• If they match, the data likely arrived intact.
• Is used in data link layer protocols (Layer 2), such as Ethernet.
• Detects common errors caused by noise and interference.
• Much more reliable than simple checksums or parity bits.