A method of identifying a network condition between a pair of network devices, the method comprising: determining a first time period between receiving a first-received packet for an initial media frame and receiving a first-received packet for a subsequent media frame, wherein the packets are received at one of the devices via a network and each received packet comprises a timestamp; determining a second time period between the timestamp of the packet for the initial media frame and the timestamp of the packet for the subsequent media frame; and identifying a network condition in dependence on a difference between the first and second time periods.