The enterprise wireless market started with fat or autonomous APs. These were perfect for small scale wireless networks with limited clients per access point. Indeed, each fat AP needed to be individually configured for radio parameters, access services, security and control. Clearly, that approach was not suitable for deployments in mid to large enterprises or organizations. It became obvious that some type of centralized AP control was needed and the WLAN controller was developed.
The WLAN controller (a rack mounted appliance or server) works with thin APs that retrieve their firmware and configuration from the WLAN controller which offers a single point of management for the entire wireless network. The WLAN controller also acts as a switch and as a firewall for all the wireless traffic that is tunneled through the controller. This offers single point of control and termination for all wireless traffic. WLAN controllers require powerful appliances so they can also perform advanced functions such as radio parameters auto-configuration (channel selection, power emission, etc.), intrusion detection and prevention, spectrum monitoring and analysis.
That being said, the “controller” option has never been an end in itself. It was the only means at that time, in the early 2000s, to convince the largest customers to embrace the WLAN technology and deploy WLAN networks that were able to meet the challenges they faced around centralized control, security, and resiliency. At that time, indeed, the limitations and costs of physical components in the APs could only lead to a centralized approach. Since then, chipsets, memories and processors have evolved to become more powerful and economical. Today, it is possible to virtualize the controller, deploy it and run it in a distributed way in the APs themselves with coordinated intelligence. This is the choice Alcatel-Lucent Enterprise (ALE) has made: Smart and advanced APs are managed as a single system or cluster and handle the control and forwarding planes in a distributed and coordinated manner.
Lower CAPEX
Controller-based architectures involve high upfront capital expenses. They also involve high licensing and maintenance costs. The most obvious benefit of the distributed control architecture is the CAPEX that is reduced since no controller is required. The saving is even more significant for deployments that involve multiple controllers for redundancy or load-sharing purposes.
Additionally, the Alcatel-Lucent Enterprise licensing model foresees one single license per AP for management. This single license includes all features required today for a state of the art wireless network (intrusion detection, firewalling, deep packet inspection…), thus reducing software costs. It also brings simplicity and clarity in comparison with traditional licensing models that come with controllers and charge licensing fees per feature.
Lower OPEX
Increased resiliency
No traffic bottleneck and decreased latency
Better scalability
When the maximum number of APs that a controller can manage is reached, deploying additional APs requires an additional controller. The distributed control architecture offers much better scalability: No controller equipement is needed, regardless of the size of the deployment.
Last but not least, the distributed control architecture is certainly the shortest route to the next breakthrough in enterprise wireless technology: Cloud Wi-Fi.
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