Strategies for Error Detection
- Send only enough extra information to detect an error; then request a re-transmission from the source. This is called ARQ (automatic repeat request). In this case, both the sender and receiver may take part in re-transmitting lost information.
- Check sum is a simple type of redundancy check that is used to detect errors in data. This
is created by calculating the binary values in a packet of data and storing the
results with the data. When the data is received at the other end of the
network then the new check sum is calculated and compared with the existing
check sum.
- Parity bit check is appended to a block of data and is seen as the simplest error detection mechanism. A parity bit is appended to the original data bits to create an even or odd number. There are two techniques used and they are:
- In even parity, a parity bit is selected so that the character has an even number of 1s.
- In odd parity, the parity bit is selected so that the character has an odd number of 1s.
- CRC which stands for Cyclic Redundancy Check operates on blocks of data and is commonly used in many form of communication. They are so called because the check code is a redundancy and the algorithm is based on cyclic codes. It provides a high level of error detection with speed and is easy to use.