A deployed WLAN can be evaluated for many reasons -- the criteria really depend on the type and purpose of the evaluation. Here are some examples.
WLAN performance can be measured and compared to site survey predictions or defined coverage/capacity needs. Such an evaluation usually involves surveying the site, taking measurements like link speed, signal strength, noise floor, and signal-to-noise ratio at regular intervals and key locations (e.g., data rate boundaries, apparent dead spots).
It may also involve measuring client performance metrics like throughput and handoff latency when roaming. If the WLAN must support voice, the tester might also measure jitter and call quality. Here, some possible criteria are minimum acceptable signal and data rate throughout a required coverage area, maximum acceptable handoff latency and noise floor, or ability to support a targeted number of users at a given bandwidth.
WLAN activities can also be compared to a defined security policy or an industry regulation like HIPAA or PCI. During such an evaluation, the site may be surveyed manually, looking for unknown devices (rogue APs). It is often more effective to monitor the site full-time using a WIPS to detect unauthorized devices, connections to banned destinations (e.g., ad hocs, neighbor APs), security policy violations (e.g., unencrypted sessions), and suspicious activity (e.g., DoS attacks, hacker tool signatures). Penetration tests may also be run to spot AP and client vulnerabilities (e.g., open ports, weak passwords, exploitable bugs).
Here again, criteria depends on the evaluation's goal. For example, a security audit counts the number of rogue APs, policy violations, etc., to determine how close the WLAN came to meeting established requirements, while a vulnerability assessment gathers information needed to remediate problems and compare current and past results to verify fixes.
To learn more, check out searchNetworking's WLAN All-in-One Guide and consult the chapters that cover WLAN design, security, and performance.
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