Abstract:
A Voice over Internet Protocol (VoIP) system includes at least one Internet Protocol (IP) terminal setting up a call through a switching system according to a signaling protocol, and at least one computer terminal capable of remotely accessing the IP terminal. The IP terminal sets up the call by exchanging a signaling message with a counterpart IP terminal when the computer terminal has remotely accessed the IP terminal, by transmitting a packet received through the call to the computer terminal, and by transmitting a packet received from the computer terminal to the counterpart IP terminal. A subscriber can receive and originate a call by accessing the subscriber&#39;s IP terminal irrespective of the subscriber&#39;s location.

Description:
PRIORITY 
       [0001]    This application claims priority under 35 U.S.C. §119 (a) to a Korean patent application filed in the Korean Intellectual Property Office on Jul. 1, 2008, and assigned Serial No. 2008-0063615, the contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to a call processing method and apparatus in a Voice over Internet Protocol (VoIP) system, and more particularly, to one which can allow a subscriber to receive/originate a call by accessing the subscriber&#39;s Internet Protocol (IP) terminal irrespective of the subscriber&#39;s location. 
         [0004]    2. Description of the Related Art 
         [0005]    At present, a variety of services are being provided to subscribers through such networks as wired and wireless Internet networks due to developing network and electronic technologies. A representative service is a VoIP service that supports a telephone call, including images and sounds, over the Internet. 
         [0006]    Compared to a conventional Public Switched Telephone Network (PSTN) service, the VoIP service has desirable features such as lower cost and various types of multimedia services. 
         [0007]    Previously, the Internet was not regarded as being suitable for real-time information exchange such as a conventional voice call conversation through the PSTN since it is a packet network designed for transmitting and receiving data. That is, it was previously believed that real-time property could not be ensured during the transmission of a voice packet since the voice packet in the packet network can be damaged or delayed by other data packets. 
         [0008]    However, when telephone service can be provided over the Internet network, i.e. the packet network, telephone charges may be cheaper than the PSTN service. Furthermore, a multimedia telephone service can be provided by simultaneously exchanging video and data based on the characteristics of the packet network. Accordingly, extensive research has been conducted on technologies that enable telephone service over the Internet, and a plurality of protocols for setting up a call over the Internet, such as H.323, Session Initiation Protocol (SIP) and Media Gateway Control Protocol (MGCP or MEGACO), and a packet-exchanging protocol, such as Real-time Transport Protocol (RTP), have been developed. 
         [0009]    At present, a voice and video call service is being provided using a VoIP service between computers, a computer and an Internet Protocol (IP) terminal, and IP terminals, which can access the network based on such a protocol. 
         [0010]    Due to the commercial launching of such VoIP services, a program capable of controlling the function of an IP terminal is installed in a computer, which is not configured to provide a VoIP service, so that the computer can be used as an auxiliary device of the IP terminal. For example, a computer can be used to control the IP terminal to originate or receive a call or to control some additional functions of the IP terminal for the sake of user convenience. 
         [0011]    According to that conventional method, even though the computer can act as an auxiliary device to control the calling function of the IP terminal, the IP terminal is required to remain in a predetermined location since it performs the calling function. As a result, the location of the IP terminal and thus functions supported by the computer are compromised. 
         [0012]    For example, when a VoIP service subscriber moves out of an area where the IP terminal is located, a VoIP service cannot be used. Neither may the subscriber answer an incoming call on the IP terminal or originate an outgoing call using the IP terminal. Therefore, the subscriber is subjected to an increasing burden of telephone charges. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention has been made to solve the foregoing problems in the prior art, and an aspect of the present invention is to provide a call processing method and apparatus in a VoIP system, in which a subscriber can receive and originate a call by accessing an IP terminal at a remote location from an area where the IP terminal is located. 
         [0014]    An aspect of the present invention is to provide a call processing method and apparatus in a VoIP system, in which the subscriber can set up an incoming call on an IP terminal or originate an outgoing call using the IP terminal at a remote location from an area where the IP terminal is located. 
         [0015]    According to the present invention, the VoIP system includes at least one IP terminal setting up a call through a switching system according to a signaling protocol, and at least one computer terminal capable of remotely accessing the IP terminal. The IP terminal sets up the call by exchanging a signaling message with a counterpart IP terminal when the computer terminal has remotely accessed the IP terminal, by transmitting a packet received through the call to the computer terminal, and by transmitting a packet received from the computer terminal to the counterpart IP terminal. 
         [0016]    The IP terminal stores authentication information of a subscriber, and perform authentication by comparing input information received from the computer terminal with the authentication information when remote access is requested from the computer terminal. 
         [0017]    The computer terminal requests the IP terminal for remote access and transmits input information, which is inputted through an authentication pop-up window from the subscriber, to the IP terminal. 
         [0018]    The IP terminal converts into relay mode when the computer terminal has remotely accessed the IP terminal, and transmits a first setup request message including originating information to the computer terminal, wherein a call setup request message received from the counterpart IP terminal includes the originating information. 
         [0019]    The IP terminal transmits a response-for-setup message to the counterpart IP terminal when the call setup request message is received, and the computer terminal outputs setup request notification information including the originating information to a subscriber, wherein the originating information is included in the first setup request message. 
         [0020]    The IP terminal transmits the call setup request message including destination information, to the counterpart IP terminal when a second setup request message including the destination information is received from the computer terminal, and transmits a ring-back message to the computer terminal when a response-for-setup message is received. The computer terminal outputs ring-back information included in the ring-back message, to the subscriber. 
         [0021]    The IP terminal sets up the call by transmitting a call answer message to the counterpart IP terminal when an answer message is received from the computer terminal, and the computer terminal transmits a packet including audio or video data, to the counterpart IP terminal, and outputs audio or video data received from the counterpart IP terminal, to the subscriber. 
         [0022]    According to the present invention, the IP terminal of the VoIP system includes a remote access manager for converting mode into relay mode by processing authentication when remote access is requested from a computer terminal over a network, a call-setting section for setting up a call by exchanging a signaling message with a counterpart IP terminal, and exchanging a message corresponding to the signaling message with the computer terminal, and a packet processor for transmitting a packet including audio or video data to the computer terminal, and transmitting a packet received from the computer terminal through the call. 
         [0023]    The call-setting section transmits a response-for-setup message to the counterpart IP terminal and a first setup request message including originating information to the computer terminal when a call setup request message including the originating information is received from the counterpart IP terminal, and sets up the call by transmitting a call answer message to the counterpart IP terminal when an answer message is received. 
         [0024]    The call-setting section transmits a call setup request message including destination information to the counterpart IP terminal when a second setup request message including the destination information is received from the computer terminal, and sets up the call with the counterpart IP terminal when a call answer message is received. 
         [0025]    According to the present invention, the computer terminal of the VoIP system includes a remote connector for requesting remote access to a corresponding IP terminal over a network when the remote access is requested from a subscriber and for transmitting information inputted from the subscriber, to the IP terminal, a message processor, when the computer terminal has remotely-accessed the IP terminal, for outputting setup request notification information including originating information, included in a first setup request message received from the IP terminal, transmitting an answer message to the IP terminal when the subscriber answers the first setup request message, and transmitting a second setup request message, including destination information inputted from the subscriber, to the IP terminal, and a data processor for outputting audio or video data, included in a packet received from the IP terminal, and transmitting a packet, including audio or video data inputted from the subscriber, to the IP terminal. 
         [0026]    According to the present invention, the call processing method in the VoIP system includes performing authentication, at an IP terminal, when remote access is requested from a computer terminal over a network, converting into relay mode when the authentication is completed, transmitting a first setup request message including originating information to the computer terminal when a call setup request message is received from a counterpart IP terminal over the network, transmitting a call answer message to the counterpart IP terminal and setting up a call when an answer message in response to the first setup request message is received from the computer terminal, transmitting a packet received through the call, to the computer terminal, and transmitting a packet, received from the computer terminal, to the counterpart IP terminal through the call. 
         [0027]    The call processing method further includes transmitting a response-for-setup message to the counterpart IP terminal when the call setup request message is received. 
         [0028]    The step of performing authentication includes requesting the computer terminal for input information when remote access is requested, and comparing the input information with previously stored authentication information. 
         [0029]    The call processing method further includes outputting, at the computer terminal, setup request notification information including originating information when the first setup request message including the originating information is received, and transmitting, at the computer terminal, an answer message to the IP terminal when the subscriber answers the first setup request message. 
         [0030]    According to the present invention, the call processing method in the VoIP system includes performing, at an IP terminal, authentication when remote access is requested from a computer terminal over a network, converting into relay mode when the authentication is completed, transmitting a call setup request message including originating information to a counterpart IP terminal, wherein the originating information is included in a second setup request message received from the computer terminals, transmitting an answer message to the computer terminal and setting up a call when a call answer message is received from the counterpart IP terminal, transmitting a packet, received through the call, to the computer terminal, and transmitting a packet, received from the computer terminal, to the counterpart IP terminal through the call. 
         [0031]    The call processing method further includes transmitting a ring-back message including ring-back information to the computer terminal when a response-for-setup message is received from the counterpart IP terminal. 
         [0032]    According to the present invention, the call processing method in the VoIP system includes requesting, at a computer terminal, an IP terminal for remote access over a network in response to a request from a subscriber, outputting setup request notification information including originating information, which is included in a first setup request message received from the IP terminal, transmitting an answer message to the IP terminal when the subscriber answers the first setup request message, transmitting a packet including audio or video data, input from the subscriber, to the IP terminal, and outputting audio or video data included in a packet received via the IP terminal from a counterpart IP terminal, which corresponds to the originating information. 
         [0033]    The call processing method further includes transmitting a second setup request message, including destination information inputted from the subscriber, to the IP terminal, and outputting ring-back information included in a ring-back message received from the IP terminal. 
         [0034]    The call processing method further includes outputting an authentication pop-up window when information input is requested from the IP terminal, and transmitting information, which is input from the subscriber using the authentication pop-up window, to the IP terminal to enable authentication. 
         [0035]    According to the present invention, a VoIP service is provided through the IP terminal using the computer terminal, which the subscriber has used for only an auxiliary purpose. 
         [0036]    Since the subscriber can process an incoming call on the subscriber&#39;s IP terminal and originate a call using the IP terminal irrespective of his/her location, the subscriber can realize reduced telephone charges. 
         [0037]    For example, the subscriber can receive an incoming call on the IP terminal or originate a call using the IP terminal at a remote location out of an office where the IP terminal is placed. Accordingly, the subscriber at the remote location can have a telephone call in the same manner as in the office, and perform a voice and video call using the IP terminal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    The above and other aspects, features and other advantages of preferred embodiments of the present invention will be more apparent from the detailed description taken in conjunction with the accompanying drawings, in which: 
           [0039]      FIG. 1  illustrates a VoIP system in accordance with the present invention; 
           [0040]      FIG. 2  illustrates an IP terminal in accordance with the present invention; 
           [0041]      FIG. 3  illustrates a computer terminal in accordance with the present invention; 
           [0042]      FIG. 4A  illustrates a first embodiment of a call processing method of a VoIP system in accordance with the present invention; 
           [0043]      FIG. 4B  illustrates a second embodiment of a call processing method of a VoIP system in accordance with the present invention; and 
           [0044]      FIG. 5  illustrates a call processing method of a VoIP system in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0045]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of a call processing method and apparatus in a VoIP system are shown. In the following description, a detailed description of known functions and components incorporated herein will be omitted for the sake of clarity and conciseness. 
         [0046]      FIG. 1  illustrates a VoIP system in accordance with the present invention. 
         [0047]    Referring to  FIG. 1 , the VoIP system includes a plurality of IP terminals  200 - 1  and  200 - 2 , a computer terminal  300  and a switch system  300  connected over a network. 
         [0048]    The switching system relays a signaling message to an originating or receiving part such as a Private Branch eXchange (PBX) or a key phone. The signaling message is used to set up a call for providing a VoIP service such as an audio and video call service. 
         [0049]    For example, the switching system  100  functions as a soft switch, relays a signaling message between originating and receiving parts, in which the signaling message is used for setting, changing and disconnecting a call between VoIP gateways, which are accessed by a plurality of the IP terminals  200 - 1  and  200 - 2  or telephone terminals access. The switching system  100  also interfaces with an application server such as a separate charging server, a Short Message Service (SMS) server and a Multimedia Messaging Service (MMS) server. 
         [0050]    An IP terminal  200 - 1  or  200 - 2  (or a computer terminal  300  realizing a VoIP service function) sets up a call for providing a VoIP service over the network and exchanges a packet (corresponding to audio and video information inputted from subscribers) through the call. 
         [0051]    In other words, the IP terminal  200 - 1  or  200 - 2  sets up a call by exchanging a signaling message with a counterpart through the switching system  100 , generates a packet including audio and video information of the subscriber, and outputs sounds and images of the subscriber while transmitting the audio and video information through the call. 
         [0052]    For example, the IP terminal  200 - 1  sets up a call by exchanging a signaling message with the counterpart IP terminal  200 - 2  in normal mode. In relay mode, when a signaling message such as a call setup request message is received, the IP terminal  200 - 1  transmits a call answer message to the counterpart IP terminal  200 - 2  and a setup request message to the computer terminal  300  connected over the network. When a call answer message in response to a call setup request message is received, the IP terminal  200 - 1  transmits an answer message to the computer terminal  300 . 
         [0053]    In addition, when a call with the counterpart IP terminal  200 - 2  is set up in relay mode, the IP terminal  200 - 1  transmits a packet including audio or video information, received from the counterpart IP terminal  200 - 2 , to the computer terminal  300 , and a packet received from the computer terminal  300  to the counterpart IP terminal  200 - 2 . In other words, the IP terminal  200 - 1  relays the packets between the computer terminal  300  and the counterpart IP terminal  200 - 2 . 
         [0054]    The computer terminal  300  accesses, for example, the IP terminal  200 - 1  over the network in response to the request from the subscriber, and transmits a setup request message to the IP terminal  200 - 1 . The setup request message includes address information of the IP terminal  200 - 1 , inputted by the subscriber. 
         [0055]    When the setup request message is received in relay mode where the computer terminal  300  is connected, the IP terminal  200 - 1  sets address information of the IP terminal  200 - 1 , included in the setup request message, as destination address information and then transmits a call setup request message to the switching system  100 . 
         [0056]    The switching system  100  transmits the call setup request message according to the destination address information included in the call setup request message. 
         [0057]    When the call setup request message is received, the IP terminal  200 - 1  checks the mode. If the mode is relay mode, the IP terminal  200 - 1  transmits a call answer message in response to the call setup request message to the counterpart IP terminal  200 - 2  through the switching system  100 , and transmits a setup request message, including originating address information, to the computer terminal  300 . 
         [0058]    In addition, when the call answer message is received, the IP terminal  200 - 2  checks the mode. If the mode is relay mode, the IP terminal  200 - 2  transmits an answer message, including ring-back information, to the computer terminal  300 . 
         [0059]      FIG. 2  illustrates an IP terminal  200  in accordance with the present invention. 
         [0060]    Referring to  FIG. 2 , the IP terminal  200  includes an audio input/output  210 , a keypad  220 , a camera  230 , a display  240 , a network interface  260 , a memory  250  and a central processing unit. The central processing unit includes a call-setting section  271 , a packet processor  272  and a remote access manager  273 . 
         [0061]    The audio input/output  210  corresponds to a handset of a common telephone terminal. The audio input/output  210  provides audio data using voice information input from the subscriber and outputs voice information from the counterpart subscriber. 
         [0062]    The keypad  220  is configured with a plurality of keys or a touch screen, which allows the subscriber to make a call setup request by inputting destination address information or to answer an incoming call setup request received from the counterpart IP terminal. 
         [0063]    The camera  230  provides video data by taking an image of the subscriber when the VoIP system is providing a video call service. 
         [0064]    The display  240  outputs video data, i.e., an image of the counterpart subscriber received from the counterpart IP terminal. 
         [0065]    The network interface  260  allows the IP terminal  200  to access the switching system  100  and the counterpart IP terminal, or to access the computer terminal  300 . 
         [0066]    The memory  250  stores such information as an operating program of the IP terminal  200 , subscriber information and call history information. 
         [0067]    The subscriber information corresponds to authentication information and personal information of the subscriber using the IP terminal  200  when the subscriber accesses the computer terminal  300  at a remote location. The authentication information can be identification (ID) and password. 
         [0068]    The central processing unit transmits a call setup request message to the counterpart IP terminal having the destination address information through the switching system when the subscriber makes a call setup request using the keypad  220 , and sets up a call when a call answer message is received. Then, the central processing unit transmits a packet through the call to the counterpart IP terminal. The packet includes audio data inputted through the audio input/output  210  and video data inputted from the camera  230 . 
         [0069]    When a call setup request message is received, the central processing unit transmits the call answer message to the counterpart IP terminal. When the call is set up, the central processing unit transfers audio data in the packet, received from the counterpart IP terminal, to the audio input/output  210  and video data to the display  240 . 
         [0070]    When the call setup request is received from the subscriber, the call-setting section  271  of the central processing unit transmits an invite message to the switching system according to the destination address information if the call setup request message such as a signaling protocol, is a Session Initiation Protocol (SIP). When a 200 OK message is received from the destination IP terminal, the central processing unit sets up the call. 
         [0071]    Below, a description will be given of the case where the signaling protocol is the SIP. It should be understood, however, that the same explanation can be applied to other types of protocol. 
         [0072]    That is, the call-setting section  271  sets up the call by exchanging the signaling message with the counterpart IP terminal according to the signaling protocol. 
         [0073]    The packet processor  272  exchanges a packet, such as a Real-time Transport Protocol (RTP) packet, including audio and video data through the call set up by the call-setting section  271 . In other words, the packet processor  272  generates a packet including audio and video data, transmits the packet through the call, and outputs the audio and video data of the packet, received from the counterpart IP terminal, by transferring the data to the audio input/output  210  and the display  240 . 
         [0074]    The remote access manager  273  manages the remote access of the subscriber and the mode of the terminal, such as normal mode and relay mode. 
         [0075]    When the subscriber performs remote access using the computer terminal  300 , the remote access manager  273  performs an authentication process based on authentication information stored in the memory  250 , and converts to relay mode after the authentication is completed. 
         [0076]    In relay mode, due to the remote access by the subscriber through the remote access manager  273 , when a call setup request message such as an invite message is received through the switching system  100 , the call-setting section  271  transmits a response-for-setup message such as a  180  ringing message, to the counterpart IP terminal and a first setup request message to the remotely-accessed computer terminal  300 . The first setup request message includes the originating address information that is included in the call setup request message. 
         [0077]    In addition, when an answer message from the computer terminal  300  is received, the call-setting section  271  sets up the call by transmitting a call answer message, such as a 200 OK message, to the originating IP terminal  200 . 
         [0078]    When a second setup request message including destination address information is received from the computer terminal  300 , the call-setting section  271  transmits a call setup request message, including the destination address information as destination information, to the destination IP terminal through the switching system  100 . 
         [0079]    In addition, when a response-for-setup message is received from the destination IP terminal  200 , the call-setting section  271  transmits a ring-back message including ring-back information to the computer terminal  300 . When a call answer message is received, the call-setting section  271  sets up a call with the destination IP terminal  200 . 
         [0080]    When a call is set up in relay mode, the packet processor  272  relays a packet exchanged through the call to the computer terminal  300 . Specifically, the packet processor  272  transmits audio and video data of the packet, received through the call, to the computer terminal  300  while transmitting a packet including audio and video data, received from the computer terminal  300 , to the counterpart IP terminal. 
         [0081]      FIG. 3  illustrates a computer terminal  300  in accordance with the present invention. 
         [0082]    Referring to  FIG. 3 , the computer terminal  300  includes a camera  310 , a microphone  320 , a speaker  330 , an input  340 , a video output, a network connector  360 , and a central processing unit  370 , which is the same as the central processing unit  270 . The camera  310  provides video data by photographing the image of the subscriber, the microphone  320  provides audio data using audio inputted from the subscriber, and the speaker  330  outputs voice information. The input  340  is configured with a keyboard or a mouse for allowing the subscriber to input information, and the video output  350  is configured with, for example, a monitor for outputting video information. 
         [0083]    The network connector  360  is configured with, for example, a Local Area Network (LAN) card, which allows the terminal to access the network. The central processing unit  370  allows the subscriber to access the IP terminal  200  at a remote location, and to set up a call through the IP terminal  200  so that the subscriber can be provided with VoIP service. The central processing unit  370  includes a remote connector  371  for allowing the subscriber to perform remote access, a message processor  372  for processing a message exchanged between the computer terminal  300  and the IP terminal  200 , and a data processor  373  for exchanging audio and video data with the IP terminal  200 . 
         [0084]    The remote connector  371 , the message processor  372  and the data processor  373  may be installed in the central processing unit  370  as application programs, or may be separately configured. 
         [0085]    In the following description of the present invention, well-known components of the computer terminal  300  will not be described in detail for the sake of clarity and conciseness. 
         [0086]    When the subscriber requests remote access to the IP terminal  200  through the input  340 , the remote connector  371  remotely accesses the IP terminal  200  through the network connector  360 . 
         [0087]    For example, when the subscriber inputs the IP address of the IP terminal  200 , the remote connector  371  accesses the IP terminal  200  and outputs an authentication pop-up window on the video output  350  so that the remote access manager  273  of the IP terminal  200  can perform an authentication process. 
         [0088]    Specifically, the remote access manager  273  of the IP terminal  200  requests authentication information to perform the authentication process in response to remote access of the computer terminal  300 . When a request for authentication information from the IP terminal  200  is received, the remote connector  371  outputs the authentication pop-up window on the video output  350  so that the subscriber can input the authentication information, and when the subscriber inputs the authentication information on the authentication pop-up window using the input  340 , transmits the input authentication information to the remote access manager  273 . 
         [0089]    Then, the remote access manager  273  of the IP terminal  200  performs authentication by comparing the input authentication information from the computer terminal  300  with authentication information stored in the memory  250 . 
         [0090]    After the authentication is completed, the remote connector  371  remotely sets up a call through the IP terminal  200 , thereby converting into remote access mode so that a VoIP service can be provided. 
         [0091]    When converted into remote access mode or in the remotely-accessed state, when a first setup request message, including destination address information, is received from the IP terminal  200 , the message processor  372  outputs notification information on a pop-up window or a voice signal to notify that a call has been requested on the IP terminal  200  of the subscriber. 
         [0092]    When the subscriber answers the call setup request using the input  340 , the message processor  372  transmits an answer message to the IP terminal  200 . 
         [0093]    In remote access mode, when the subscriber makes a call setup request by inputting destination address information using the input  340 , the message processor  372  transmits a second setup message to the IP terminal  200 . 
         [0094]    In remote access mode, the data processor  373  outputs audio data received from the IP terminal  200  by transferring the audio data to the speaker  330 , and outputs video data by transferring the video data to the video display  350 . 
         [0095]    The data processor  373  transmits audio data received through the microphone  320  and video data received from the camera  310  to the IP terminal  200 . 
         [0096]    Therefore, the subscriber can set up an incoming call on the IP terminal  200  or originate a call with the IP terminal  200  using the computer terminal  300  at a remote location, and can realize VoIP service through the call set up using the IP terminal  200 . 
         [0097]      FIG. 4A  illustrates a first embodiment of a call processing method of the VoIP system in accordance with the present invention, and describes processing of an incoming call on the IP terminal  200 - 1  using the computer terminal  300  at a remote location. Referring to  FIG. 4A , the second IP terminal  200 - 2  transmits a call setup request message to the switching system  100  in response to a request from the subscriber in S 100 . The call setup request message includes IP address information of the first IP terminal  200 - 1  as destination address information. 
         [0098]    The switching system  100  transmits a call setup request message to the second IP terminal  200 - 2  by detecting destination address information of the call setup request message in S 110 . 
         [0099]    Due to a relay mode in which the computer terminal  300  has remotely accessed the IP terminal  200 - 1 , when the call setup request message is received, the first IP terminal  200 - 1  transmits a response-for-setup message to the second IP terminal  200 - 2  through the switching system  100  in S 120  and S 130 . 
         [0100]    When the response-for-setup message is received, the second IP terminal  200 - 2  notifies the response-for-setup to the subscriber by outputting ring-back information. 
         [0101]    Then, the first IP terminal  200 - 1  transmits a first setup request message including originating address information of the call setup request message to the computer terminal  300  in S 140 . When the first setup request message is received, the computer terminal  300  outputs telephone call setup request notification information to the subscriber in S 150 . In this case, the computer terminal  300  can output the telephone call setup request notification information on a pop-up window or a voice signal. 
         [0102]    When the subscriber checks the telephone call setup request notification information and answers, for example, by clicking an answer button on the pop-up window in S  160 , the computer terminal  300  transmits an answer message to the first IP terminal  200 - 1  in S 170 . 
         [0103]    When the answer message is received from the computer terminal  300 , the first terminal  200 - 1  transmits a call answer message to the second IP terminal  200 - 2  through the switching system  100  in S 180  and S 190 . 
         [0104]    Then, the first IP terminal  200 - 1  and the second IP terminal  200 - 2  set up a call in S 200 . 
         [0105]    When the call is set up, the second IP terminal  200 - 2  transmits a packet including audio and video data through the call to the first IP terminal  200 - 1  in S 210 , and the first IP terminal  200 - 1  transmits (i.e., relays) the packet received on the telephone call to the computer terminal in S 220 . 
         [0106]    The computer terminal  300  outputs the audio and video data, included in the packet received from the first IP terminal  200 - 1 , on the speaker  330  and the video output  350  in S 230 . 
         [0107]    In addition, the computer terminal  300  receives audio data from the subscriber using the microphone  320  and video data using the camera  310  in S 240 , and transmits a packet including the audio and video data to the first IP terminal  200 - 1  in S 250 . 
         [0108]    The first IP terminal  200 - 1  transmits the packet, received from the computer terminal  300 , on the telephone call to the second IP terminal  200 - 2  in S 260 , and the second IP terminal  200 - 2  outputs the audio and video data included in the packet. 
         [0109]      FIG. 4B  illustrates a second embodiment of a call processing method of the VoIP system in accordance with the present invention, and describes a case where the computer terminal  300  makes a call setup request through the IP terminal  200 , which the computer terminal  300  has remotely accessed. Referring to  FIG. 4B , when the subscriber generates a call setup request by inputting destination address information on the input  340  in S 300 , the computer terminal  300  transmits a second setup request message including the destination address information to the first IP terminal  200 - 1  in S 310 . 
         [0110]    The first IP terminal  200 - 1  transmits a call setup request message to the second IP terminal  200 - 2  through the switching system  100  in S 320  and S 330 . In this case, the call setup request message includes the destination address information of the second setup request message as destination information. 
         [0111]    When the call setup request message is received, the second IP terminal  200 - 2  transmits a response-for-setup message to the first IP terminal  200 - 1  through the switching system  100  in S 340  and S 350 . 
         [0112]    When the response-for-setup message is received, the first IP terminal  200 - 1  transmits a ring-back message (i.e., a progress message) including ring-back information to the computer terminal  300  in S 360 , and the computer terminal  300  outputs the ring-back information from the ring-back message in S 370 . 
         [0113]    When the subscriber answers an incoming call (Hook off), the second IP terminal  200 - 2  transmits a call answer message to the first IP terminal  200 - 1  through the switching system  100  in S 380  and S 390 . 
         [0114]    When the call answer message is received, the first IP terminal  200 - 1  transmits an answer message to the computer terminal  300  in S 400 , and sets up a call with the second IP terminal  200 - 2  in S 410 . 
         [0115]    After the call is set up, the computer terminal  300  receives audio data from the subscriber using the microphone  320  and video data using the camera  310  in S 420 , and transmits a packet including the audio and video data to the first IP terminal  200 - 1  in S 430 . 
         [0116]    The first IP terminal  200 - 1  transmits the packet, received from the computer terminal  300 , through the call to the second IP terminal  200 - 2  in S 440 , and the second IP terminal  200 - 2  outputs the audio and video data from the packet. 
         [0117]    When the call is set up, the second IP terminal  200 - 2  transmits a packet including audio and video data through the call to the first IP terminal  200 - 1  in S 450 , and the first IP terminal  200 - 1  transmits (i.e., relays) the packet received through the call to the computer terminal  300  in S 460 . 
         [0118]    The computer terminal  300  outputs the audio and video data, included in the packet received from the first IP terminal  200 - 1 , on the speaker  330  and the video output  350  in S 470 . 
         [0119]      FIG. 5  illustrates a call processing method of a VoIP system in accordance with the present invention. Referring to  FIG. 5 , the subscriber requests in S 500  a remote access using the computer terminal  300  from a remote location where the IP terminal  200 - 1  is not located. In this case, the subscriber can request the remote access using IP address information of the IP terminal  200 - 1 . When the remote access is requested, the IP terminal  200 - 1  performs an authentication process in S 510 . 
         [0120]    Specifically, the IP terminal  200 - 1  requests, in response to the remote access request, the computer terminal  300  to input authentication information. The computer terminal  300  outputs an authentication pop-up window requesting the subscriber to input the authentication information, and transmits the authentication information, input from the subscriber, to the IP terminal  200 - 1 . 
         [0121]    Then, the IP terminal  200 - 1  performs the authentication process by comparing the received authentication information with previously-stored authentication information. 
         [0122]    After the authentication process is completed, the IP terminal  200 - 1  converts into relay mode, and determines whether a call setup message is received through the switching system  100  in S 520 . 
         [0123]    When the call setup request message is received, the IP terminal  200  transmits a response-for-setup message to the counterpart IP terminal  200 - 2  according to destination address information of the call setup request message, and a first setup request message including originating address information to the computer terminal  300  in S 530 . When the call setup request message is not received, the process proceeds to S 590 , which will be discussed below. 
         [0124]    The computer terminal  300  outputs setup request notification information to the subscriber in S 540 . The setup request notification information includes the originating address information, which is included in the first setup request message. When the subscriber answers the setup request, the computer terminal  300  transmits an answer message to the IP terminal  200 - 1  in S 550 . 
         [0125]    When the answer message is received from the computer terminal  300 , the IP terminal  200 - 1  transmits a call answer message to the counterpart IP terminal  200 - 2  through the switching system  100  in S 560 , and establishes a call in S 570 . 
         [0126]    The IP terminal  200 - 1  transmits audio and video data included in a packet received from the counterpart IP terminal  200 - 2  to the computer terminal  300  and a packet including audio and video data received from the computer terminal  300  to the counterpart IP terminal  200 - 2  in S 580 . In other words, the IP terminal  200 - 1  relays a packet from the counterpart IP terminal  200 - 2  to the computer terminal  300  while transmitting a packet from the computer terminal  300  to the counterpart IP terminal  200 - 2 . 
         [0127]    Afterwards, the IP terminal  200 - 1  determines whether a second setup request message including destination address information is received from the computer terminal  300  in S 590 . 
         [0128]    When it is determined that the second setup request message is received from the computer terminal  300 , the IP terminal transmits a call setup request message, in which the destination address information included in the second setup request message is set as destination information, to the counterpart IP terminal  200  through the switching system  100  in S 600 . When it is determined that the second setup request message is not received from the computer terminal  300 , the process ends. 
         [0129]    When a response-for-setup message is received from the counterpart IP terminal  200 - 2 , the IP terminal  200 - 1  transmits a ring-back message including ring-back information to the computer terminal  300  in S 610 . When a call answer message is received, the IP terminal  200 - 1  sets up a call with the counterpart IP terminal  200  in S 620 . 
         [0130]    The IP terminal  200 - 1  transmits audio and video data included in a packet received from the counterpart IP terminal  200  through the call to the computer terminal  300  and a packet including audio and video data received from the computer terminal  300  to the counterpart IP terminal  200  in S 630 . In other words, the IP terminal  200 - 1  relays the packet received from the counterpart IP terminal  200 - 2  to the computer terminal  300  while relaying the packet received from the computer terminal  300  to the counterpart IP terminal  200 . 
         [0131]    While the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents.