UDP checksum

Sender:

• treat segment contents as sequence of 16-bit integers

• checksum: addition (1’s complement sum) of segment contents

• sender puts checksum value into UDP checksum field

Receiver:

• compute checksum of received segment

• check if computed checksum equals checksum field value:

  • NO - error detected
  • YES - no error detected. But maybe errors nonethless? More later ….

Goal: detect “errors” (e.g., flipped bits) in transmitted segment

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