System for blind/attended transfer in session initiation protocol (SIP)-based network and method of controlling the transfer

A method of controlling call transfer to a third terminal when a first Session Initiation Protocol (SIP)-based terminal and a second SIP-based terminal are communicating through an SIP server, the method comprising:

• pausing the call of the second terminal by transmitting a call waiting message to the second terminal upon the call waiting message for pausing a call of the second terminal being received from the first terminal, the pausing being performed by the SIP server;
• transmitting the call request message to the third terminal upon a call request message for a call of the third terminal being received from the first terminal, the transmitting being performed by the SIP server;
• determining whether a call transfer message has been received from the first terminal prior to receiving a call response message from the third terminal, the determining being performed by the SIP server;
• and
• performing the blind transfer by transmitting the call request message to the second terminal and the third terminal upon a call transfer message being received from the first terminal prior to receiving a call response message from the third terminal, the blind transfer being performed by the SIP server.

A system for a blind/attended transfer in a Session Initiation Protocol (SIP)-based network in which a call transfer to a third terminal is facilitated upon a first SIP-based terminal and a second SIP-based terminal communicating through an SIP server, the system comprising:

• the first terminal transmitting a call request message to the SIP server to establish a call with the third terminal that is a transfer object, after pausing a call with the second terminal by transmitting a call waiting message to the SIP server upon a call waiting function being activated, the first terminal determining whether a call transfer message has been received prior to receiving a call response message associated with the call request message from the SIP server, and performing the blind transfer with the third terminal by transmitting the call transfer message to the SIP server upon the call transfer message being received prior to receiving the call response message;
• the SIP server performing a call waiting procedure after transmitting the call waiting message to the second terminal upon the SIP server receiving the call waiting message from the first terminal, and transmitting the call request message to the third terminal upon the SIP server receiving the call request message from the first terminal after pausing the second terminal, the SIP server transmitting a call re-request message to the third terminal upon the SIP server receiving the call transfer message from the first terminal prior to receiving the call response message from the third terminal, and performing the blind transfer with the third terminal after terminating the call requested by the first terminal in response to a call-termination request message in response to the call request message from the third terminal;
• and
• the third terminal transmitting the call-termination request message to the SIP server in response to the call request message of the first terminal, upon the third terminal receiving the call transfer message of the first terminal after receiving the call request message of the first terminal, and performing the blind transfer by transmitting the call response message to the SIP server in response to the call request message of the first terminal.

A Session Initiation Protocol (SIP)-based terminal to perform a blind/attended transfer to a third terminal while communicating with a second terminal in an SIP-based network, the terminal comprising:

• a call controller transmitting a call request message to the third terminal, which is a transfer object, after pausing a call with the second terminal by transmitting a call waiting message to an SIP server upon a call waiting function being activated;
• a call-transfer determiner determining whether a call transfer function (Hook on) has been activated prior to receiving a call response message (200OK) from the SIP server;
• and
• a call-transfer processor performing the blind transfer with the third terminal by transmitting a call-transfer request message (REFER) to the SIP server for the blind transfer to the third terminal, upon the call transfer function being activated prior to receiving a call response message (200OK) from the SIP server.