NODE DEVICE AND COMMUNICATION METHOD USED IN DISRUPTION/DELAY/DISCONNECT TOLERANT NETWORK

A node device (1A) receives a second ACK list during contact with an adjacent node (1B) and updates a first ACK list and a first summary vector based on the second ACK list. The first summary vector indicates messages that have been stored in the node device (1A). During the contact with the adjacent node (1B), the first summary vector is sent to the adjacent node (1B) prior to transmission of the messages. The first ACK list and the second ACK list indicate ACK messages that have been recognized by the node device (1A) and the adjacent node (1B), respectively. Each ACK message indicates a message that has already been delivered to its final destination node through a DTN (100). Accordingly, it is possible, for example, to prevent copies of a message that has already arrived at its final destination node from being spread within a Disruption Tolerant Network.