US 7,010,585 B2 · 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.

Claims11

Dependent claims

A DNS server to dynamically assign an IP address only to a terminal which is now conducting communications, the DNS server comprising:

means for holding a table in which FQDNs of terminals managed by the DNS server are registered in advance and a list of IP addresses to be broad cast to the terminals managed by the DNS server;
address conversion means for converting an IP address in the list of IP addresses to be broad cast to the terminals managed by the DNS server into one of an address of a data link layer and a network layer in the sense of OSI communications between the terminals managed by the DNS server, when the DNS server receives an inquiry of an FQDN;
and
registration means for registering the IP addresses in the table in correspondence with the FQDNs, wherein a terminal required to receive communication can receive it.

1 more element

A communication system comprising:

an external DNS server provided on a fire wall for managing a correspondence relationship between a FQDN and an IP address of a terminal, both of which are to be broad cast to the outside of the fire wall;
IP address conversion means NAT provided on the fire wall;
and
an internal DNS server provided in the fire wall and for managing a correspondence relationship between the FQDN and the IP address of the terminal, both of which are used in the fire wall,
wherein when there is an inquiry from inside the fire wall, the internal DNS server returns an IP address found from the correspondences relationship between the FQDN and the IP address of a terminal, both of which are used in the fire wall,
wherein when there is an inquiry from outside the fire wall, the external DNS server inquires of the internal DNS server an internal IP address corresponding to the FQDN and corresponds one of the IP addresses in an external broad cast list to an internal IP address of the terminal and registers an external IP address in correspondence with the FQDN, and
wherein the IP address conversion means NAT converts a destination IP address (external IP address) of a packet passing the firewall from outside to inside into the internal IP address, and a source IP address (internal IP address) of a packet passing the fire wall from inside to outside into the IP address of the NAT.

4 more elements

Dependencies are inferred from the claim text.

DNS server, DHCP server, terminal and communication system

Life of this patent

DNS server, DHCP server, terminal and communication system

Life of this patent

Abstract

Claims11