[toast0]

The client is in the best position to manage the handoff because it knows which aps it can hear and is configured to connect to. I've seen some APs that will disconnect clients with low signals strength, but the AP doesn't know if the client can actually see something else. Zero handoff addresses this by having all APs listening to the same channel, with synchronized security parameters; whichever AP receives the packet gets to send replies. The down side is you end up with a larger coverage area but the same channel capacity as a single AP.