A method for monitoring performance of a plurality of wireless networks created by a plurality of wireless access points and connected client devices, said wireless networks being wireless local area networks, said method comprising: receiving network performance data relating to at least some of the client devices from the plurality of wireless access points, wherein the network performance data comprises sets of data transfer rate metrics, each set relating to data sessions travelling between a wireless interface of one of the plurality of wireless access points and a wireless interface of a client device connected to said wireless access point; receiving device characteristic information relating to each connected client device; and analysing the performance data to identify trends in client devices which are experiencing wireless network performance degradation due to interoperability problems, wherein the analysing further comprises the steps of: for each set of data transfer rate metrics: identifying within that set, a subset of flows having reduced performance; determining the client devices associated with the identified subset of flows; grouping the determined client devices according to a device type; upon determining a group of client devices that is poorly performing, performing a finer level analysis by sorting the client devices in the group according to an operating system version or a hardware revision; and determining, for the client devices in the group and as a result of the finer level analysis, a device property among the operating system version and the hardware revision, which is indicative of a device interoperability issue. receiving network performance data relating to at least some of the client devices from the plurality of wireless access points, wherein the network performance data comprises sets of data transfer rate metrics, each set relating to data sessions travelling between a wireless interface of one of the plurality of wireless access points and a wireless interface of a client device connected to said wireless access point; receiving device characteristic information relating to each connected client device; and analysing the performance data to identify trends in client devices which are experiencing wireless network performance degradation due to interoperability problems, wherein the analysing further comprises the steps of: for each set of data transfer rate metrics: identifying within that set, a subset of flows having reduced performance; determining the client devices associated with the identified subset of flows; grouping the determined client devices according to a device type; upon determining a group of client devices that is poorly performing, performing a finer level analysis by sorting the client devices in the group according to an operating system version or a hardware revision; and determining, for the client devices in the group and as a result of the finer level analysis, a device property among the operating system version and the hardware revision, which is indicative of a device interoperability issue. for each set of data transfer rate metrics: identifying within that set, a subset of flows having reduced performance; determining the client devices associated with the identified subset of flows; grouping the determined client devices according to a device type; upon determining a group of client devices that is poorly performing, performing a finer level analysis by sorting the client devices in the group according to an operating system version or a hardware revision; and determining, for the client devices in the group and as a result of the finer level analysis, a device property among the operating system version and the hardware revision, which is indicative of a device interoperability issue. identifying within that set, a subset of flows having reduced performance; determining the client devices associated with the identified subset of flows; grouping the determined client devices according to a device type; upon determining a group of client devices that is poorly performing, performing a finer level analysis by sorting the client devices in the group according to an operating system version or a hardware revision; and determining, for the client devices in the group and as a result of the finer level analysis, a device property among the operating system version and the hardware revision, which is indicative of a device interoperability issue.