CRC = Cyclic Redundancy Check 11001 is the Generator 101101010111 is the Message The remainder after doing the division of the Message by the Generator we will call the redundancy bits. Since the redundancy bits are always n - 1 bits for an n bit Generator, here we will have the remainder being 5 -1 or 4 redundancy bits. Extend the orignal Message M with 4 bits. 101101010111 is the Message 0000 are the four extra 0 bits needed to get the entire Message + Redundancy bits that will be Transmitted by one computer to another computer. 101101010111 concatenated with 0000 is: 1011010101110000 11001 1011010101110000 10110 11001 ----- 1111 <--------- by even parity. Do NOT put the leading 0's in. 11001 1011010101110000 10110 11001 ----- 11111 <----------- Bring down next digit, enough digits to get 11001 another 5 bit string. ----- 110 <----------- Result of the EVEN parity, but not showing the leading 0's. 11001 1011010101110000 -- 10110 -- 11001 -- ----- 11111-- 11001-- ----- 11001 Bring down the next two digits, to get 5 digit string. 11001 1011010101110000 -- 10110 11001 <---------Generator ----- 11111 11001 <---------Generator ----- 11001 11001 Generator again ----- 00000 <------------- By even parity there were no 1's! 01110 <------------- Thus we need to bring down 5 digits! 11100 <----------- Oh, 5 digits was NOT enough, cauuse Generator --> 11001 the leading digits must be a 1. ----- 101 -- 11001 1011010101110000 -- 10110 11001 <--------- Generator ----- 11111 11001 <--------- Generator ----- 11001 11001 <--------- Generator again ----- 11100 <----------- Oh, 5 digits was NOT enough, cauuse Generator --> 11001 the leading digits must be a 1. ----- 10100 <--------------- Bring down last TWO DIGITS.. 11001 <--------------- Apply the GENERATOR for the ----- last time. 1101 THESE ARE THE ERROR CONTROL BITS that the CRC algorithm calculated. 1101 = the CRC bits. 101101010111 is the Message (the data to be sent). Concatenate 101101010111 adn 1101 and then TRANSMIT (T = the Transmitted) = 1011010101111101 mmmmmmmmmmmmEEEE m = message bits E = CRC error control bits