T 2.11 Insufficient route dimensioning

During planning of networks, server rooms or computer centres often the mistake is made of defining the functionality, capacity and/or technical security design from the present status. This approach fails to take account of the facts that

• the capacities of the network and computers will have to be extended in line with increases in data volumes or the use of new services;

• changes in technical standards may make architectural or technical security modifications necessary;

• the possibility that the network will need to be expanded can never be ruled out;

and

• new requirements imposed on a given network may make it necessary to lay other cables.

Examples

• Expansion of networks is possible only to the extent permitted by the installed cables or by the availability of space for additional cables. Especially where cables are accommodated in closed routing (piping, plaster-covered underfloor channels, etc.), even where space is available, it is often not possible to insert additional cables without damaging new or old cables. The only alternative is to pull the existing cables out of the route and re-lay all the cables, old and new, at the same time. The resulting disruption of operations and costs can be considerable.

• In the early stages of planning a computer centre the only criteria considered were aesthetic considerations. Infrastructural and security technical requirements were given less priority and were only specified after the basic construction work was complete. The completion of the building had to be extensively delayed because routes that were required were not available and the size and positioning of individual rooms did not match the requirements. Changes during later operations were very difficult to implement.

• After ten years of operations a complete new network structure and IT cabling were planned in a company. On investigation it turned out that renewal of the private branch exchange and the PBX cabling, which up to now had followed the same routing as the IT cabling, was planned for the following year. Without co-ordinating these two measures, work on the routing would have had to be duplicated and possibly the routes planned would have been too small.