DNS server, DHCP server, terminal and communication system

Abstract

The object of the present invention is to provide a DNS server and terminals both of which are capable of sending and receiving communication by means of a small number of IP addresses. In the case where a firewall is not provided, when the DNS server receives an inquiry of a FQDN, it sends a broad cast frame for searching a terminal to which an IP address is assigned via all the network devices. When a terminal monitors the broad cast frame and finds the FQDN to be its own FQDN, it returns the uni-cast frame to the DNS server. When the DNS server receives the uni-cast frame, it makes a look-up table and a reverse look-up table. As a result, the terminal can receive the communication by an ordinary method. In the case where the firewall is provided, by processing an IP address conversion between the external IP address and the internal address by the use of an IP address conversion means NAT in addition to making the look-up table and the reverse look-up table, the terminal can receive communication.

1 - 6 . (canceled)  
   
   
       7 . A DHCP server used when a terminal connected to a DNS server by means of a data link layer sends communication, characterized in that when the terminal requires the DHCP server to assign thereto an IP address with respect to the FQDN of the terminal, which can be broad cast to the outside, the DHCP server asks the DNS server about the IP address and registers one of the IP addresses to be broad cast in correspondence with the FQDN and returns the IP address to the terminal.  
   
   
       8 . A DHCP server as set forth in  claim 7 , wherein when the DHCP server receives an IP address release command from the terminal, it sends an IP address return command to the DNS server to make the DNS server delete the IP address corresponding to the FQDN of the DNS server.  
   
   
       9 . A DHCP server as set forth in  claim 7 , wherein when the terminal requires the DHCP server to assign an IP address thereto, it designates the FQDN of the terminal.