Error Detection And Correction Methods-Cont

Error Correction And Detection Method ™  CHECKSUM o    Error detection method used by the Higher Layers o    Like   VRC,   LRC,   CRC,   Checksum   is   also   based   on   the   concept   of redundancy One's Complement Finding one's complement -    Invert every 1 to 0 and 0 to 1 -    A and -A are one's complement of each other -    +A = 1010 ® -A = 0101 -    +0 = 0000 ® -0 = 1111 o    Error detection method used by the Higher Layers o    Like VRC, LRC, CRC, Checksum is also based on the concept of redundancy    CHECKSUM Generator

Error Correction And Detection Method ™  CHECKSUM o    Error detection method used by the Higher Layers o    Like   VRC,   LRC,   CRC,   Checksum   is   also   based   on   the   concept   of redundancy One's Complement Finding one's complement -    Invert every 1 to 0 and 0 to 1 -    A and -A are one's complement of each other -    +A = 1010 ® -A = 0101 -    +0 = 0000 ® -0 = 1111 o    Error detection method used by the Higher Layers o    Like VRC, LRC, CRC, Checksum is also based on the concept of redundancy ¾   CHECKSUM Generator

o    The sender subdivides data units into equal segments of 'n' bits(16 bits) o    These segments are added together using one's complement o    The total (sum) is then complemented and appended to the end of the original data unit as redundancy bits called CHECKSUM o    The extended data unit is transmitted across the network o    The receiver subdivides data unit as above and adds all segments together and complement the result o    If  the  intended  data  unit  is  intact,  total  value  found  by  adding  the  data segments and the checksum field should be zero o    If the result is not zero, the packet contains an error & the receiver rejects it Checksum Figure