Understanding Load Balancing for Wireless Radios
Load balancing distributes a workload across multiple wireless radios to achieve optimal utilization, maximize throughput, minimize response time, and avoid overload.
RF load balancing for access points has the ability to reduce network congestion over an area by distributing client sessions across access point radios with overlapping coverage. With load balancing, you can ensure that all access points on the network handle a proportionate share of wireless traffic, and that no single access point gets overloaded. Load balancing of access points is enabled by default in WLAN Service profiles—that means that all access points using a WLAN Service profile are load balanced.
This topic describes:
Why Would I Need Load Balancing?
As new clients arrive, load balancing distributes the clients among access points such that the access points share the client load. The wireless operating system, MSS, encourages clients to associate with the least loaded (by client count) access point, so that clients are well distributed across access points. This way, no one access point is more overloaded and there is less interruption of wireless services on the network. For example, in an auditorium or lecture hall, there might be a large number of clients in a relatively small amount of space. While a single access point might be sufficient for providing an RF signal to the entire area, more access points might be required to deliver enough aggregate bandwidth for all of the clients. When additional access points are installed in the room, RF load balancing spreads clients evenly across the access points, increasing the available aggregate bandwidth by increasing the number of access points. Without load balancing, you could still have two access points in a classroom, but all clients have associated to just one access point.
When Would I Avoid Load Balancing?
We do not recommend load balancing for low-latency applications such as voice or live-streaming (unbuffered) video. Load balancing is not advisable for voice transmission because load balancing can impact roam times, which can impact voice quality for roaming clients. Load balancing can also make streaming video jittery with dropped frames.
How Load Balancing Works
The wireless operating system, MSS, balances the client load by adjusting how access points are perceived by clients advertising the same SSID. The capacity of an access point handling new clients is compared to other access points in the SSID. As new clients arrive, MSS encourages them to associate with the least loaded (by client count) access points, such that clients are well distributed across access points. By default, MSS only encourages clients to associate with an access point if there are access points available with capacity to accept more clients. Clients are never prevented from associating with an access point if it is the only one available.
Where Do I Configure Load Balancing?
Load balancing is enabled and configured in multiple places for several kinds of load balancing. The load balancing option discussed here applies to wireless access points and radios.
 | Note: Load balancing configured in Access profiles applies to the RADIUS servers configured within that profile. For details, see Creating and Managing Access Profiles. |
RF load balancing for access points is enabled by default in Juniper WLAN mobility domains, affecting all radios within that domain. You can, however, disable load-balancing in a WLAN Service profile. If you want an WLAN’s SSID on access points to be exempt from load balancing, you can indicate that a WLAN Service profile is Load Balancing Exempt—see the directions for Network Director Creating and Managing a WLAN Service Profile.
You can also assign a single access point to a specific load balance group when you add that access point to a controller—see Adding and Managing an Access Point.
