Today it's possible to virtualize the controller. By running it in a distributed way, smart APs can manage themselves with coordinated intelligence.
WLAN controllers (a rack mounted appliance or server) works with thin APs that retrieve their firmware and configuration from the WLAN controller: a single point of management for the entire wireless network. It also acts as a switch and as a firewall for all the wireless traffic that is tunneled through the controller: a single point of control and termination for all wireless traffic.
Today it's possible to virtualize the controller and deploy it and run it in a distributed way in the APs themselves with coordinated intelligence. 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.
A Unified Management and Distributed Control solution eliminates the previously required controller from wireless deployment architectures, offering many potential benefits to organizations and their IT departments.
Lower CAPEX: Controller-based architectures involve high upfront capital expenses. They also involve high licensing and maintenance costs. With a distributed control architecture, CAPEX is reduced as no controller is required.
Lower OPEX: No controllers means less equipment to operate and manage providing several OPEX benefits: less rack space, less power and cooling requirements, no maintenance fees (especially for unused backup controllers), and, basically, less equipment to be monitored by the IT department.
Increased resiliency: In a centralized controller-based architecture, the controller is a single point of failure for the entire wireless network impacting all wireless traffic when the controller fails. The only way to minimize the impact is to add additional redundant controllers, but this comes at a cost. With a distributed control architecture, that single point of failure does not exist. Indeed, the controller function is no longer centralized but shared by all APs in the domain of management.
No traffic bottleneck and decreased latency: The WLAN is expected today to connect bandwidth-hungry and/or latency sensitive applications. Over the years, the technology has improved to provide increasing levels of throughput with IEEE standards 802.11a/b/g/n and now 802.11ac. With the distributed control approach, the traffic is no longer tunneled to centralized equipment but directly bridged into the local Ethernet switch.
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.