Redundancy means excessive, superfluous. In technology, redundancy procedures are used to safeguard data, transmission links, networks and devices. Redundancy is inextricably linked with availability and can refer equally to the redundancy of data, protocols, network infrastructures and system components.
- In data transmission and in data sets, redundancy is said to exist when part of the information content of a message can be eliminated without affecting the message content. There is no loss of information by omitting redundant data. In transmission engineering, redundancy is often added for error detection as check bits and parity bits.
- In transmission technology, redundancy is ensured by suitable redundancy protocols. These then determine a redundant transmission path if the transmission path used is overloaded or faulty. Well-known redundancy protocols are the Spanning Tree Protocol( STP), the Virtual Router Redundancy Protocol( VRRP) and Ethernet Automatic Protection Switching( EAPS).
- The requirement for the use of redundancy protocols is only possible if the network infrastructure provides alternative paths that are used in the event of a fault. This can be as with the bypass, where a direct parallel path is switched, or with the double ring structures, where the ring is operated in the opposite direction in the event of a fault. To ensure high availability or high availability, network infrastructures provide for redundant networks or links. With High Availability Seamless Redundancy( HSR) and Parallel Redundancy Protocol( PRP), there are two redundancy protocols for industrial networks that work with redundant networks.
- In the component and system area, redundancy refers to the use of multiple components, transmission links, servers with identical functions or an availability network. The components or devices operate completely in parallel, but one active device processes the applications, the other runs in standby and takes over the tasks of the active device in the event of a fault.
- In web terminology, redundancy stands for the more frequent presence of the same information or text passages. When evaluating web pages with a high redundant content, they are rated negatively. If redundancy refers to duplicated content, then it has a particularly negative effect. The same applies to doorway pages without their own information value.