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Automated performance monitoring and proactive management to maintain quality-of-service targets and service level agreements (SLAs) is a necessary ingredient of any mission-critical wireless LAN (WLAN).
| Using WIPS to monitor QoS |
| To learn about using Wireless Intrusion Prevention Systems (WIPS) to monitor quality of service (QoS), see this SearchSecurity.com Wireless Lunchtime Learning tip on using WIPS to monitor WLAN performance. | |
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As you say, many WLANs that were built to support data applications offer best-effort performance. Of course that does not mean that quality of service was ignored during their design – in fact, many data WLANs were carefully planned to deliver target data rates and signal strengths in defined coverage areas. However, without continuous monitoring and active response to performance problems, network operators cannot reasonably expect QoS targets to be attained most of the time, much less guarantee or prove that SLAs have been met.
Clearly, many steps are required to create and operate a highly-reliable WLAN, from rigorous design and proper instrumentation to monitoring processes and tools that enable not just reactive but proactive performance management. The 7/24 wireless quality assurance systems like those that you mention are important because they don't simply set QoS levels and try to meet them – they actually measure delivered QoS in the live WLAN and help operators react to correct impending problems and satisfy SLAs.
For example, most WLAN controllers and management systems poll APs for traffic counters to generate maintain historical performance statistics. When something goes seriously wrong, WLAN controllers may react – for example, by increasing power on adjacent APs when another AP goes down or usage thresholds are reached. While this keeps the WLAN operating and gives you a feel for past performance, it doesn't ensure that QoS targets are being achieved. Clients could be connected at high data rates but still receive too little airtime or too much interference to keep users and applications happy.
WLAN quality assurance systems can offer added functionality. For starters, they can scan the air full-time to obtain a near-real-time view of WLAN performance. Second, they can compare actual performance to defined targets, triggering events that speed corrective actions – either manually or through execution of defined rules – before users and applications are significantly impacted. Third, quality assurance systems can run automated, periodic performance tests to measure end-to-end throughput, latency, and jitter – in other words, measuring what users and applications are truly experiencing.
Of course, if your WLAN is not designed to manage call admission, prioritize traffic, or deliver high-throughput, or low latency a quality assurance system won't magically meet SLAs that require that kind of network infrastructure. However, full-time, automated, service-level monitoring and real-time response systems can play an essential role in helping a well-designed WLAN to operate at its best.
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