In a network 101, a relay 104 makes a name search of a communication destination node 102d based on a request from a communication source node 102s according to a condition into which at least one or a plurality of information effective for identifying the communication destination node 102d, such as the running state, the use state, the positional information, and the information representing the characteristic of the communication destination node 102d, information representing the information held by the communication destination node 102d, and the like are combined. The relay 104 makes a reply by searching a database of a DNS, etc. for information identifying the communication destination node 102d, or obtains and replies the information by actually inquiring the communication destination node 102d at the time of an inquiry.