What is VRC and LRC - Vertical and Longitudinal Redundancy Check


While transmission of data in networking, data can be corrupted or some bits gets corrupt during transmission. For reliability of those errors in communication data must be orgnized and corrected. At Data link layer we can implement error correction or at Transport layer we can diagnose and correct it (both layers are from OSI model). Lets talk about VRC and LRC Error detection techniques.

VRC and LRC
VRC stands for Vertical Redundancy Check (VRC) and  as usual LRC stands for Longitudinal Redundant check.

Vertical Redundancy Check

Another name of vertical redundancy check is parity check. Least Expensive Mechanism. So in this mechanism when error detect a parity bit is append to the data unit so the total number of bits becomes even including parity bit.

Longitudinal Redundancy Check

This method is bit different rather then VRC. In this method Block of bits organized in tables e.g rows and columns. calculate the parity bit for each column and the set of this parity bit is also sending with original data. From the block of parity we can check the redundancy.


Example of VRC and LRC

Calculate the VRC and LRC for the following bit pattern using even parity:
← 0100110 1110001 1100101 0000000.

Solution:

DATA
VRC
0100110
01001101
1110001
11100010
1100101
11001010
0000000
00000000

DATA
0100110
1110001
1100101
0000000
LRC  0110010

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