Patent ID: 7957366

Claim:
An IP telephone apparatus connected to an ENUM server, to a DNS server, and to a call agent apparatus, the ENUM server storing a NAPTR (Naming Authority Pointer) resource record, the NAPTR resource record including a URI and a corresponding ENUM domain name, the DNS server storing an IP address corresponding to the URI, the call agent apparatus controlling a connection between the IP telephone apparatus and a call destination, the IP telephone apparatus comprising: a key pad configured to input a telephone number of the call destination; and a controller configured to generate an ENUM domain name based on the input telephone number, to transmit, to the ENUM server, the generated ENUM domain name, to determine whether a NAPTR resource record corresponding to the transmitted ENUM domain name is received from the ENUM server, to determine, when the NAPTR resource record is received from the ENUM server, whether the received NAPTR resource record indicates that the call destination can perform a communication based on a SIP (Session Initiation Protocol), to transmit, to the DNS server, a URI contained in the received NAPTR resource record when the received NAPTR resource record indicates that the call destination can perform a communication based on the SIP, to receive an IP address corresponding to the transmitted URI from the DNS server, to access the call destination for a call by a Peer-to-Peer communication via an IP network based on the SIP, using the received IP address, without using the call agent apparatus, to determine, when the received NAPTR resource record does not indicate that the call destination can perform a communication based on the SIP, whether the received NAPTR resource record indicates that the call destination can perform a communication via a PSTN (Public Switched Telephone Network), and to call the call destination via the PSTN without using the call agent apparatus and without using the DNS server, when the received NAPTR resource record indicates that the call destination can perform a communication via the PSTN, the controller being further configured to determine whether a message indicating that the call agent apparatus is unsuccessful in establishing communication with the call destination is received from the call agent apparatus, when the NAPTR resource record is not received from the ENUM server, wherein, when it is determined that the controller receives a message other than the message indicating that the call agent apparatus is unsuccessful in establishing communication with the call destination, the controller accesses the call destination for a call via the call agent apparatus without using the DNS, such that the communication between the call agent apparatus and the call destination is selected from one of being performed through the IP network and being performed through the PSTN.