|  | 8.11 | Network Power Supply Issues: Surge Suppressors and Uninterruptible Power Supply (UPS) Functions
| 8.11.3 | UPS: for certain LAN devices

The problem of sags and brownouts can best be addressed by the use of uninterruptible power supplies (UPS). The extent to which UPS must be provided for a LAN depends on factors such as the budget, the types of services the LAN provides, the frequency of regional power outages, and the typical length and duration of power outages, when they do occur. At a minimum, every network file server should have a source of backup power. If power wiring hubs are required, then they must also be supported with backup power. Finally, in extended star topology networks, where internetworking devices such as bridges and routers are used, power backup must be provided to them, as well, in order to avoid failures in the system. Where possible, power backup should also be provided for all work areas. As every network administrator knows, it does little good to have an operational server and wiring system, if they cannot ensure that computers will not go down before users can save their spreadsheets and word processing files.