|  | 8.12 | Troubleshooting the Network
| 8.12.4 | The need to check the following as physical and logical indicators of trouble: link lights, power lights, error displays, error logs and displays, and performance monitors
When isolating a problem, physical and logical indicators of trouble may exist. These indicators include the link light, power light, error display, error log and display, and performance monitors. Link lights should be a steady green or amber indicating that a device is connected to a network. The power light should also be a steady light. If this light is out on a machine, it could mean one of two things. (1) There is no power in the device or (2) the power light could have burned out. All aspects of the problem should be scoped before determining if the device has no power. Error displays often indicate a malfunction or a failure in a device. Errors can be viewed either as a dialog, which pops up, or in the LED error display of the device. Logs and error displays maintain a listing of errors that have occurred. Although error logs and displays do not provide a solution to the problem, some documentation is provided to help lead to a solution. Performance monitoring is a tool provided by Windows NT called the Network Monitor. This monitor provides information regarding data coming in and out of a workstation. It tracks the resources used by the components and applications. Performance monitoring is useful when trying to identify bottlenecks in the CPU, memory, disk I/O, network I/O, and error trends. This feature monitors real-time system performance and performance history. By using this monitor, an administrator can determine the capacity of the system and system configurations.