The process includes acquiring, from a relay device that relays a packet between a first communication device and a second communication device, a plurality of first delay times generated by a round trip of the packet between the first communication device and the relay device, and a plurality of second delay times generated by a round trip of the packet between the second communication device and the relay device, sorting separately the plurality of first delay times and the plurality of second delay times based on a length of a delay time, and calculating device delay times based on a first delay calculation that calculates a difference between each of the plurality of first delay times and each of the plurality of second delay times in a same rank after the sorting.