In an information communication system, information communication devices exchange an IP packet over IP networks. When performing a predetermined packet exchanging procedure in which the number of router hops is limited to a predetermined control value or less, each of the information communication devices monitors Time-To-Live values designated in the headers of IP packets received over a period of time from the start of the predetermined packet exchanging procedure to immediately before the end of the predetermined packet exchanging procedure to continuously update the maximum Time-To-Live value of the monitored Time-To-Live values, and checks whether the maximum Time-To-Live value does not exceed the control value.