Chapter 21 Load Balancing
Imagine a coffee shop in a crowded business district that offers free wireless connectivity to its customers. The coffee shop owner can’t possibly know how many connections his NWA will have at any given moment. As such, he decides to put a limit on the bandwidth that is available to his customers but not on the actual number of connections he allows. This means anyone can connect to his wireless network as long as the NWA has the bandwidth to spare. If too many people connect and the NWA hits its bandwidth cap then all new connections must basically wait for their turn or get shunted to the nearest identical AP.
The following figure depicts an NWA with a hard bandwidth limit of 6 Megabits per second (Mbps). Bandwidth up to 6 Mbps is considered “balanced”. More than that and it becomes “overloaded”; the AP must then work harder to serve each client.
Figure 160 Load Balancing by Traffic Level Example
Y
R
G
B
The yellow (Y), green (G) and blue (B) laptops are each using approximately 2 Mbps. Altogether, they consume the AP’s entire “balanced” bandwidth allotment. When the red (R) laptop tries to make a connection, the AP (which does not want to overload itself) denies it if an identical AP is in range that can take on the burden of the new connection.
Note: If no other APs with matching settings are in range of the NWA, then it will still accept the connection despite becoming overloaded.
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