Load Balancing

The load balancing feature can be controlled from within ZoneDirector's web interface to balance the number of clients per radio on adjacent APs. "Adjacent APs" are determined by ZoneDirector at startup by measuring the RSSI during channel scans. After startup, ZoneDirector uses subsequent scans to update the list of adjacent radios periodically and when a new AP sends its first scan report. When an AP leaves, ZoneDirector immediately updates the list of adjacent radios and refreshes the client limits at each affected AP.

Once ZoneDirector is aware of which APs are adjacent to each other, it begins managing the client load by sending desired client limits to the APs. These limits are “soft values” that can be exceeded in several scenarios, including: (1) when a client’s signal is so weak that it may not be able to support a link with another AP, and (2) when a client’s signal is so strong that it really belongs on this AP.

The APs maintain these desired client limits and enforce them once they reach the limits by withholding probe responses and authentication responses on any radio that has reached its limit.

Key points on load balancing:

• These rules apply only to client devices; the AP always responds to another AP that is attempting to set up or maintain a mesh network.
• Load balancing does not disassociate clients already connected.
• Load balancing takes action before a client association request, reducing the chance of client misbehavior.
• The process does not require any time-critical interaction between APs and ZoneDirector.
• Provides control of adjacent AP distance with safeguards against abandoning clients.
• Can be disabled on a per-WLAN basis; for instance, in a voice WLAN, load balancing may not be desired due to voice roaming considerations.
• Background scanning must be enabled on the WLAN for load balancing to work.