S 1.65 Renewal of IT cabling

Initiation responsibility: Planner, Building Services, Head of IT

Implementation responsibility: Building Services

The rapid progress in information technology and in particular the challenges presented by new IT applications often result in considerations of modernisation or complete replacement of existing IT cables in buildings containing older IT cabling.

The time and expense required to replace the existing IT cabling by completely new secondary and tertiary cabling must not be underestimated. Experience has shown that after an initial examination of the financial expense and organisational difficulties associated with a comprehensive modernisation project, the decision to use the existing IT cabling for as long as possible is usually made.

The IT cabling should only be completely renewed if it can safely be assumed that the business processes in the organisation will no longer be provided with enough support using the existing IT cabling. Examples of clear indications that the existing IT cabling cannot be used any more include:

• Installing additional cables to connect additional users results in constant disruptions of network operations.
• The existing network suffers from frequent network failures due to short-circuits in a token ring or the formation of loops from loose contacts on IBM IVS Type-1 Ethernet cables, for example.
• The existing cabling cannot meet the capacity demands any more, because entire floors are connected using IBM IVS Type-1 cabling, which has a maximum transmission rate of 10Mbit/sec, for example.

If the IT cabling is to be renewed, all planning steps required for an initial installation must be followed (see S 2.395 Requirements analysis for IT cabling). The requirements analysis and the assessment of the growth in demand are performed at the beginning in this case as well.

Note that when replacing older Type-1 cabling, the cable routes must be examined to determine whether they can be used as is with the new cables, especially in the tertiary area. Since Type-1 cables permit a maximum cable length of only 150 metres, it may be necessary to install additional floor distributors at a suitable location to limit the connection length of category 5 or higher cables to a maximum of 100 metres. In this case, the connection length is calculated as the sum of the length of the tertiary cable plus the length of the patch cable.

If an empty building is modernised, only a technical services plan need be created for the migration. In buildings used as office space and not just as warehouses, a modernisation plan must also be drawn up to migrate the existing IT cabling to an up-to-date cabling technology.

The plan must specify how the new IT cabling can be installed during business operations in such a way that business operations are interrupted as little as possible.

Review questions:

• When using existing cable routes: Are the connection lengths also admissible for the new cabling?