A master controller comprising: a processing resource ; and a memory resource storing machine-readable instructions to cause the processing resource to: create a plurality of groups of access points, APs , connected to a plurality of local controllers , wherein the groups are created such that each group comprises APs on the same AP channel or the same subgroup of AP channels; move a first subset of the plurality of APs which is connected to a first local controller of the plurality of local controllers to at least one other local controller of the plurality of local controllers ; upgrade the first local controller ; move APs associated with a group among the plurality of groups of APs to the upgraded first local controller ; upgrade the APs associated with the group of the first local controller ; move a second subset of the plurality of APs which is connected to a second local controller of the plurality of local controllers to at least one other local controller of the plurality of local controllers ; upgrade the second local controller ; move APs associated with a second group among the plurality of groups of APs to the second local controller ; and upgrade the plurality of APs of the second group. a processing resource ; and a memory resource storing machine-readable instructions to cause the processing resource to: create a plurality of groups of access points, APs , connected to a plurality of local controllers , wherein the groups are created such that each group comprises APs on the same AP channel or the same subgroup of AP channels; move a first subset of the plurality of APs which is connected to a first local controller of the plurality of local controllers to at least one other local controller of the plurality of local controllers ; upgrade the first local controller ; move APs associated with a group among the plurality of groups of APs to the upgraded first local controller ; upgrade the APs associated with the group of the first local controller ; move a second subset of the plurality of APs which is connected to a second local controller of the plurality of local controllers to at least one other local controller of the plurality of local controllers ; upgrade the second local controller ; move APs associated with a second group among the plurality of groups of APs to the second local controller ; and upgrade the plurality of APs of the second group. create a plurality of groups of access points, APs , connected to a plurality of local controllers , wherein the groups are created such that each group comprises APs on the same AP channel or the same subgroup of AP channels; move a first subset of the plurality of APs which is connected to a first local controller of the plurality of local controllers to at least one other local controller of the plurality of local controllers ; upgrade the first local controller ; move APs associated with a group among the plurality of groups of APs to the upgraded first local controller ; upgrade the APs associated with the group of the first local controller ; move a second subset of the plurality of APs which is connected to a second local controller of the plurality of local controllers to at least one other local controller of the plurality of local controllers ; upgrade the second local controller ; move APs associated with a second group among the plurality of groups of APs to the second local controller ; and upgrade the plurality of APs of the second group. <EOS>