T 2.11 Insufficient route dimensioning

When planning networks, server rooms or computer centres, the mistake of basing the functionality, capacity, or technical security design on the current requirements only is made quite frequently. This approach fails to take account of the facts that:

• the capacities of the network and computers will have to be expanded as the volume of data increases or new services are added,
• changes in technical standards may make architectural or technical security modifications necessary.
• the network will need to be expanded often as the operational requirements change,
• new requirements imposed on a network may make it necessary to lay new cables.

Examples:

• Networks can only be expanded to the extent permitted by the existing cables installed and by the amount of space available for additional cables. Especially in closed cable routes (conduits, screed-covered underfloor channels, etc.), it is often impossible to pull additional cables through without damaging the new or old cables, even there is still space available. The only alternative in this case is to pull the existing cables out of the trays and re-install all cables, both old and new, at the same time. The resulting costs and disruptions to operations can be considerable.

• In the early planning stages for a computer centre, the only criteria considered were aesthetic aspects. Infrastructural and technical security requirements were given less priority and were only specified after the basic construction work was complete. The completion of the building was delayed extensively because 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 operation, one company planned a completely new network structure and new IT cabling. Upon inquiry, it turned out that the replacement of the telecommunications system and its 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, routing work would have been duplicated, and the routes planned may not have had enough capacity.