IP communication method, IP terminal apparatus, ENUM server and IP communication system

An IP terminal apparatus connected to an ENUM server via an IP network, the IP terminal apparatus comprising:

• a generator that adds an input keyword to a packet for inquiring NAPTR resource records of a destination IP terminal apparatus to generate a query packet;
• a transmitter that transmits the generated query packet to the ENUM server;
• and
• a receiver that receives, from the ENUM server, a reply packet including the NAPTR resource records of the destination IP terminal apparatus, when the keyword included in the query packet is identical to a keyword stored on the ENUM server.

An ENUM server having a database to store registered NAPTR resource records corresponding to telephone number information of an IP terminal apparatus and returning the NAPTR resource records in response to a query from an IP terminal apparatus, the ENUM server comprising:

• a memory that stores a keyword corresponding to telephone number information of a destination IP terminal apparatus;
• a receiver that receives, from the IP terminal apparatus, the query packet with the added keyword regarding the destination IP terminal apparatus;
• a comparing unit that compares the keyword added to the received query packet with the keyword of the destination IP terminal apparatus stored in the memory;
• a retriever that retrieves, from the data base, corresponding NAPTR resource records, when the added keyword is identical to the keyword stored in the memory;
• a generator that generates a reply packet including the NAPTR resource records;
• and
• a transmitter that transmits the generated reply packet to the IP terminal apparatus from which the query packet is received regarding the destination IP terminal apparatus.

An IP communication system comprising:

• an IP terminal apparatus that is connected to the IP communication system via an IP network;
• and
• an ENUM server that has a database to store registered NAPTR resource records corresponding to telephone number information of an IP terminal apparatus and that returns the NAPTR resource records in response to a query from an IP terminal apparatus,
• the IP terminal apparatus further comprising:
• a generator that generates a query packet that adds an input keyword to a packet for inquiring NAPTR resource records of a destination IP terminal apparatus;
• a transmitter of the generated query packet to the ENUM server;
• and
• a receiver that receives a reply packet that includes the NAPTR resource records of the destination IP terminal apparatus from the ENUM server, when the keyword included in the query packet is identical to a keyword stored on the ENUM server,
• the ENUM server further comprising:
• a memory that stores the keyword corresponding to the telephone number information of the destination IP terminal apparatus;
• a receiver that receives, from the IP terminal apparatus, the query packet with the added keyword regarding the destination IP terminal apparatus;
• a comparing unit that compares the keyword added to the received query packet with the keyword of the destination IP terminal apparatus stored in the memory;
• a retriever that retrieves corresponding NAPTR resource records from the database, when the added keyword is identical to the keyword of the destination IP terminal apparatus stored in the memory;
• a generator that generates a reply packet including the NAPTR resource records;
• and
• a transmitter that transmits the generated reply packet to the IP terminal apparatus from which the query packet is received regarding the destination IP terminal apparatus.