Patent ID: 7602767

Claim:
An IP communication method for an IP communication system, the IP communication system including an IP terminal apparatus and an ENUM (Telephone Number Mapping) server, the IP terminal apparatus being connected to the IP communication network via an IP network, the ENUM server including a database to store NAPTR (Naming Authority Pointer) resource records corresponding to telephone number information of a destination IP terminal apparatus and returning the NAPTR resource records in response to a query from the IP terminal apparatus, the IP communication method comprising: storing, in a memory of the ENUM server, a keyword corresponding to the telephone number information of the destination IP terminal apparatus; generating, at the IP terminal apparatus, a query packet by adding an input keyword to a packet for inquiring NAPTR resource records of the destination IP terminal apparatus; transmitting, from the IP terminal apparatus to the ENUM server, the generated query packet; receiving, at the ENUM server from the IP terminal apparatus, the query packet with the added keyword regarding the destination IP terminal apparatus; comparing, at the ENUM server, the keyword included in the received query packet with the keyword of the destination IP terminal apparatus stored in the memory; retrieving, from the database of the ENUM server, corresponding NAPTR resource records, when the keyword included in the query packet is identical to the keyword stored on the ENUM server; generating, at the ENUM server, a reply packet that includes the NAPTR resource records; transmitting, from the ENUM server, the generated reply packet to the IP terminal apparatus from which the query packet is received regarding the destination IP terminal apparatus; receiving, at the IP terminal apparatus from the ENUM server, the reply packet that includes the NAPTR resource records of the destination IP terminal apparatus, when the keyword included in the query packet is identical to the keyword stored on the ENUM server; receiving, at the IP terminal apparatus from the ENUM server, a reply packet indicating that no NAPTR resource record of the destination IP terminal apparatus is available when the keyword included in the query packet is not identical to the keyword stored on the ENUM server; and generating, at the ENUM server, a reply packet indicating that no NAPTR resource record of the destination IP terminal apparatus is available when the keyword included in the query packet is not identical to the keyword stored on the ENUM server.