As this chapter explains, you must consider certain implications when designing, installing, and supporting a WLAN. It is imperative that you consider security vulnerabilities, such as passive monitoring, unauthorized access, and denial-of-service (DoS) attacks. Encryption and authentication, respectively, are ways to counteract passive monitoring and unauthorized access. The threat of a DoS attack is a bit more difficult to resolve, and it makes sense to have a “Plan B” in case the WLAN becomes inoperable, especially for mission-critical applications. Irregular propagation of radio signals through a facility and radio signal interference, coming from microwave ovens, cordless phones, and other devices, are unforeseen things that can reduce the performance of the WLAN. As a result, it is important to perform a wireless site survey before installing a WLAN. As part of deploying a WLAN, you also need to consider and possibly test for other implications, such as multipath propagation, roaming delays, battery limitations, and interoperability problems.