me of the network does not match user expectations or previous Chapter Nine Table 9-1: WLAN Troubleshooting - Narrowing down the Problem Problem identification Considerations Is it a connection problem? A major category of problems with WLANs relate to client station connections; individual users or groups of users may be unable to connect to previously accessible network resources. Is it a performance problem? The second major category of problems is perform- ance related; network coverage, speed or response time are not as expected or as previously experienced. How extensive is the problem? Does the problem affect just one device or is the same problem experienced by many? For example, if the problem is connectivity to the network, if only one client is affected, suspect the hardware and set-up of that device's NIC. If a whole BSS is affected, check the hardware and configuration of the access point. How regular is the problem? Does it occur continuously, at specific times of the day - for example around mid-day when staff are using a microwave oven in the lunch room? experience. These two categories of problems are considered in the following sections. Connectivity Problem Checklist Connectivity problems can have a root cause at the PHY or MAC level, for example due to physical or configuration problems with RF hardware, or at higher levels, for example due to a failure during the user authentication process. The checklist shown in Table 9-4 can be used as a starting point for diagnosing connectivity problems. Performance Problem Checklist Performance problems occur in WLANs either because a transmission is not reaching the receiving station with sufficient signal to noise ratio (SNR) to be properly detected and decoded, or because an access point is overloaded and unable to cope with the volume of traffic. In turn, SNR problems can be due to low signal (coverage holes) or high noise (interference). The checklist in Table 9-5 can be used as a starting point to address performance problems. Wireless LAN Trouble