Checksumming: Cyclic Redundancy Check View data bits, D, as a binary number Choose r+1 bit pattern( generator , G o Goal: choose r crc bits, R, such that o <D, R> exactly divisible(polynomial division by g(modulo 2 e Receiver knows G, divides <D, R> by G. If non-zero remainder: error detected! e Can detect all burst errors less than r+1 bits o Widely used in practice (ATM, HDLC d bits ← r bits bit D: data bits to be sent R: CRC bits, pattern D* 2 XOR R mathematica formula 5: DatChecksumming: Cyclic Redundancy Check  View data bits, D, as a binary number  Choose r+1 bit pattern (generator), G  Goal: choose r CRC bits, R, such that  <D,R> exactly divisible (polynomial division) by G (modulo 2)  Receiver knows G, divides <D,R> by G. If non-zero remainder: error detected!  Can detect all burst errors less than r+1 bits  Widely used in practice (ATM, HDLC) 5: DataLink Layer 5-8