Patent ID: 7903602

Claim:
A method of setting up a packet switched (PS) call connection to a PS network by a mobile communication terminal, the method comprising: attempting the PS call connection; establishing the PS call connection and receiving DNS server information from the PS network; attempting a connection to a domain name system (DNS) server using the received DNS server information after the mobile communication terminal is PS call-connected to the PS network; deciding by the mobile communication terminal a validity of the DNS server information based on whether the mobile communication terminal is able to access the DNS server for the PS network; maintaining the PS call connection if the DNS server information is decided to be valid; and releasing the PS call connection based on a request for a PS call disconnection if the DNS server information is decided to be not valid, wherein the request for a PS call disconnection is from the mobile communication terminal to the PS network, the DNS server information includes an IP address of the DNS server, the validity deciding step includes: enabling the mobile communication terminal to attempt the connection to the DNS server using the IP address; and determining that the DNS server information is valid if the connection to the DNS server succeeds or invalid if the connection to the DNS server fails, in the enabling step, the mobile communication terminal attempts a transmission control protocol (TCP) connection to a 53 rd port of the DNS server, and the method further comprising releasing the TCP connection if the mobile communication terminal succeeds in the TCP connection.