DNS server, DHCP server, terminal and communication system

• US 20010023459A1
• Filed: 02/28/2001
• Published: 09/20/2001
• Est. Priority Date: 03/14/2000
• Status: Active Grant

• Current Assignee: DDI Corporation (TTM Technologies Incorporated)
• Original Assignee: DDI Corporation (TTM Technologies Incorporated)
• Inventors: Asami, Tohru
• Granted Patent: US 7,010,585 B2
• Time in Patent Office: Days
• US Class Current: 709/245
• CPC Class Codes: H04L 61/00 Network arrangements, protocols or services for addressing or naming
• CPC Class Codes: H04L 61/2514 between local and global IP addresses
• CPC Class Codes: H04L 61/2564 for a higher-layer protocol, e.g. for session initiation protocol [SIP]
• CPC Class Codes: H04L 61/2571 for identification, e.g. for authentication or billing charging arrangements H04L12/14
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 61/4552 Lookup mechanisms between a plurality of directories; Synchronisation of directories, e.g. metadirectories
• CPC Class Codes: H04L 61/5014 using dynamic host configuration protocol [DHCP] or bootstrap protocol [BOOTP]

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.

Claims

1. 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 the list of IP addresses to be broad cast to the outside;

address conversion means for converting one of the IP addresses in the list to be broad cast to the outside 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 the FQDN; and

registration means for registering the IP addresses in the table in correspondence with the FQDNs,

wherein the terminal required to receive communication can receive it.

2. A DNS server as set forth in

claim 1

, wherein the table includes a look-up table and a reverse look-up table.

3. A DNS server as set forth in

claim 1

, wherein when the DNS server receives an inquiry of the FQDN, the address conversion means sends a broad cast frame for searching a terminal to which the IP address is assigned and when it has an answer to the broad cast frame, it determines to register the IP address in correspondence with the FQDN.

4. A DNS server as set forth in

claim 3

, wherein the broad cast frame sent by the address conversion means includes at least an IP address to be assigned to the terminal, a net mask to be assigned to the terminal, and the FQDN of the terminal.

5. A terminal to which an IP address is dynamically assigned by a DNS server, characterized in that a terminal corresponding to the FQDN of a broad cast frame sent by the DNS server initializes a network device receiving the broad cast frame by the IP address and the net mask given by the broad cast frame.

6. A terminal as set forth in

claim 5

, wherein the terminal sends an IP address return command to the DNS server when there are no communications for a previously predetermined time.

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.

10. A communication system comprising:

an external DNS server provided on a fire wall for managing a correspondence relationship between the FQDN and the IP address of a terminal, both of which are to be broad cast to the outside;

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 a 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 the external broad cast list to the internal IP address of the terminal and registers the 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.

11. A communication system as set forth in

claim 10

, wherein when there is no communications for a predetermined time, the IP address conversion means sends an IP address return command to the external DNS server and deletes the external IP address corresponding to the FQDN and stops processing the IP address conversion.

12. A communication system as set forth in

claim 10

, wherein when the NAT receives a communication sending packet from an internal terminal, the external DNS server receives an external IP address request and when it receives the external IP address request, it asks the internal DNS server and gets the FQDN corresponding to the internal IP address of the terminal and registers the external IP address corresponding to the FQDN and directs the NAT to process the IP address conversion between the external IP address and the internal IP address.

13. A communication system as set forth in

claim 10

, further comprising means for holding a table in which the FQDNs of the terminals to be managed by the external DNS server are registered in advance and the list of IP addresses to be broad cast to the outside, wherein the table includes a look-up table and a reverse look-up table.

14. A communication system as set forth in

claim 12

, wherein when the external DNS server registers the external IP address corresponding to the FQDN in the table, it prevents an DNS server on an external Internet from caching the registered information of the FQDN and the external IP address.