Data-link layer uses some error control mechanism to ensure that frames (data bit streams) are transmitted with certain level of accuracy. But to understand how errors is controlled, it is essential to know what types of errors may occur.

Types of Errors

There may be three types of errors:

1. Single bit error

In a frame, there is only one bit, anywhere though, which is corrupt.

2. Multiple bits error

Frame is received with more than one bit in corrupted state.

3. Burst error

Frame contains more than one consecutive bits corrupted.

Error control mechanism may involve two possible ways:

  • Error detection
  • Error correction

Error Detecting Codes

Basic approach used for error detection is the use of redundancy, where additional bits are added to facilitate detection and correction of errors. Popular techniques are:

  • Simple Parity check
  • Two-dimensional Parity check
  • Cyclic redundancy check