5. ERROR DETECTION
In networking, error detection refers to the
techniques used to detect noise or other
impairments introduced into data while it is
transmitted from source to destination.
Error detection minimizes the probability of
passing incorrect frames to the destination,
known as undetected error probability
6. Types of Error
Error
Burst
Error
Single-
Bit Error
If the signal is carrying binary encoded data,
such changes can alter the meaning of the data.
These errors can be divided into two types-
7. In a single-bit error, only one bit in the
data unit has changed.
Note:
Single-Bit Error
8. A burst error means that 2 or more bits
in the data unit have changed.
Note:
Burst Error
9. Error detection uses the concept of
redundancy, which means adding
extra bits for detecting errors at the
destination.
Redundancy
13. Simple Parity Checking
Even Parity:1 is added
to the block if it
contains an odd
number of 1’s and 0 is
added if it contains an
even number of 1’s.
16. Simple parity check can detect all
single-bit errors. It can detect burst
errors only if the total number of
errors in each data unit is odd.
Note:
19. The last error detection method we discuss here is
called the checksum. The checksum is used in the
Internet by several protocols although not at the
data link layer.
However, we briefly discuss it here to complete
our discussion on error checking.
Checksum
20. We can make the job of the receiver easier if
we send the negative (complement) of the sum,
called the checksum.
In this case, we send (7, 11, 12,0,6, -36). The
receiver can add all the numbers received
(including the checksum).
If the result is 0, it assumes no
error; otherwise, there is an error.
Checksum