1. Maharshi Dayanand Saraswati University
Presentation Topic: Cyclic Redundancy Check
Subject : Computer Networks
Class: MCA1
Presented by : Shivangi Tak Submitted to: Praful Sir
4. What is Error Detection ?
Networks must be able to transfer data from one device
to another with complete accuracy.
Data can be corrupted during transmission.
For reliable communication, errors must be detected
and corrected.
5.
6. Cyclic Redundancy Check
CRC or Cyclic Redundancy Check is a method of
detecting errors in the communication channel.
CRC uses Generator Polynomial which is available on
both sender and receiver side.
7. CRC Generation At Sender Side
1.Find the Length of Divisor ‘L’
2.Append 0 ‘L-1’bits to the original bits
3.Perform Binary Digit Operation
4.Remainder of the division=CRC A B A XOR B
0 0 0
0 1 1
1 0 1
1 1 0
8. A B A XOR B
0 0 0
0 1 1
1 0 1
1 1 0
1 Find the Length of Divisor ‘L’
2 Append 0 ‘L-1’bits to the original bits
3 Perform Binary Digit Operation
4 Remainder of the division=CRC
Finally, Cyclic Redundancy
check will be generated as
shown.
9. The sender performs a division operation
on the bits being sent and calculates the
remainder. Before sending the actual bits,
the sender adds the remainder at the end
of the actual bits.
(Data Bits+ Remainder)
11. At The Receiver Side
Receiver divides received data (data + CRC) with
generator.
If remainder is zero, data is correctly received.
Else, there is error.
12. A B A XOR B
0 0 0
0 1 1
1 0 1
1 1 0
Therefore, the remainder is all zeros.
Hence, the data received has no
error.
13. Advantages of CRC
1. Cyclic codes have a very good performance in detecting
single-bit errors, double errors, an odd number of errors.
2. They can easily be implemented in hardware and
software.
3. They are especially fast when implemented in hardware.
4. This has made cyclic codes a good candidate for many
networks.