S 6.18 Provision of redundant lines

Initiation responsibility: Head of IT Section; staff responsible for the individual IT applications

Implementation responsibility: Head of Site/Bldg Technical Service; administrator

Redundant wiring means that, apart from the lines used for normal operation, additional lines are provided between appropriate points in the network. Such lines should be run over an alternate route. This will make it possible to switch to a redundant line in case of malfunction. Such switching can be effected automatically or manually. Automatic switching must be indicated to a unit which will arrange for fault clearing on the normal line.

The working order of redundant lines must be tested by their actual use at reasonable intervals. Dimensioning, test intervals and the basic need for redundant lines depend directly on the availability requirements of the network. Similarly, account must be taken of the relation between the activation time of the redundant line and the recovery time of the normal line. When answering such questions, it is crucial to know whether the lines are operated by the public sector (TELEKOM) or by the private sector.

• As regards public-sector lines, the user has no influence on their protection. The public network generally provides a sufficient number of redundant lines. In most instances it will suffice, in case of failure of a line (either a fixed connection or a switched line), to restore the connection by setting up a switched line. Provision of redundant fixed connections is usually too expensive and, in most cases, is not absolutely required.

• In a private network, the operator can significantly influence the security of lines. In most cases, cost considerations result in no redundant lines being provided. In private networks, however, redundant lines entail no current expenditure in addition to the cost of production