S 6.103 Redundancies for the primary cabling

Initiation responsibility: Head of IT

Implementation responsibility: Head of IT

On large properties, several buildings are often connected in a star-shaped network to a computer centre located in one of the buildings. It should be examined, at least for the most important buildings, whether redundant primary IT cabling should be installed on separate trays.

It should also be examined whether or not redundant connections to IT or telecommunication providers should be installed. To achieve true redundancy in this case, it must be clarified with the provider whether the connections to the carrier network are actually made at different locations (local exchanges).

Whether or not redundant primary cabling or redundant connection to providers is necessary depends on the availability requirements of the organisation.

Parallel operation

Inside the buildings, it must be ensured using suitable active network components that the redundant lines are automatically used in parallel during operations. This maintains redundancy while increasing the capacity. However, it must be noted in this case that the failure of one line results in reduced transmission capacity. This reduced capacity must be taken into account in the contingency planning concept.

Switching over

If the technology used or the services implemented using the cabling do not permit parallel operation of the redundant lines, operation must be switched over to the corresponding replacement line when the line in use malfunctions. The switchover can be performed manually or automatically.

If parallel operation is not possible, operation should be switched over to the replacement lines at regular, reasonable intervals, even if no malfunction has actually occurred. This serves as a test of the functionality of the replacement lines. The test intervals should be derived from the availability requirements.

Surveillance

Redundant communication links can generally only efficiently increase the level of availability if the functionality of the links is monitored. Monitoring is used to detect malfunctions, bottlenecks, and other irregularities early so that problems can be eliminated quickly or prevented entirely. Without monitoring, amongst other risks, there is an increased risk of not detecting failed lines and there only being an apparent redundancy, but no actual redundancy.