JP4787815B2 - Communication terminal device and control method thereof - Google Patents

Description

  The present invention relates to ITU-T recommendation T.264 via a SIP proxy server device. The present invention relates to a communication terminal apparatus that performs image communication by 38 communication and a control method thereof.

  Generally, it is connected to a packet network such as the Internet. 38, a network facsimile apparatus that exchanges facsimile messages with a partner apparatus via a packet network by exchanging a message for call control (hereinafter referred to as “T38 communication procedure”). A call control channel; Data communication channels for exchanging 38 data (two channels for upstream and downstream channels are required; see FIGS. 13 and 14) must be prepared separately.

  However, opening a plurality of ports in this way may lead to a security hole, so security sensitive users want to perform T38 communication (so-called “IP-FAX communication”) using as few ports as possible. There is a request.

For example, in Patent Documents 1 and 2, the same channel as the call control channel is used. A technique is disclosed in which 38 data transfer can be made to pass through a firewall or NAT. Moreover, since only one communication channel is used, it is advantageous in terms of security.
JP 2001-292267 A Japanese Patent Application No. 2003-319265

  On the other hand, there is a demand for maintaining a high level of security by always performing communication via a proxy server device, instead of directly communicating with a device existing in an external network.

  For such a request, the techniques disclosed in Patent Documents 1 and 2 cannot be applied.

  This is because the SIP proxy server device is T.264. Since 38 packets are not passed, This is because 38 packets can only be communicated directly between terminals as shown in FIG.

  Therefore, there is a problem that it is necessary to make a hole in the firewall and security is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a communication terminal device capable of appropriately performing T38 communication via a SIP proxy server device and a control method thereof.

  The present invention relates to ITU-T recommendation T.264 via a SIP proxy server device. 38 is a communication terminal device that performs image communication by 38 communication, and establishes a call control channel that performs call control of communication with a partner terminal via a SIP proxy server device, and then establishes communication with the partner terminal via the call control channel. Communication control means for performing image communication by sequentially arranging T38 data according to the T38 communication procedure in the INFO message exchanged in accordance with the progress of the T38 communication procedure and exchanging the INFO message with the partner terminal. It is provided.

  In addition, the communication control means arranges a keyword indicating that the T38 communication using the INFO message is provided in the header information of the message transmitted to the counterpart terminal during call control, and communicates with the counterpart terminal during call control. The function is negotiated between the two.

  Further, the communication control means, when the communication load with the proxy server device is larger than a predetermined value before the start of the T38 communication using the INFO message, the packet of the T38 data to be arranged in the INFO message during the T38 communication The size is set to a small value.

  Further, the communication control means, when the packet arrival time with the proxy server device is larger than a predetermined value before the start of the T38 communication using the INFO message, the T38 data placed in the INFO message during the T38 communication. The packet size is set to a small value.

  Further, the communication control means stops the T38 communication and shifts to the recommunication state when the communication load with the proxy server device is larger than a predetermined value before the start of the T38 communication using the INFO message. It is what you do.

  Further, the communication control means stops the T38 communication when the communication load with the proxy server device is larger than a predetermined value before the start of the T38 communication using the INFO message, and makes another proxy server device It is used for re-communication.

  In addition, the ITU-T recommendation T.264 via the SIP proxy server device. 38. A communication terminal device control method for performing image communication by 38 communication, wherein when a call control channel for performing call control of communication with a partner terminal is established via a SIP proxy server device, the partner terminal is connected via the call control channel The T38 data according to the T38 communication procedure is sequentially arranged in the INFO message exchanged with the communication terminal according to the progress of the T38 communication procedure, and the INFO message is exchanged with the partner terminal so that the image communication is performed. It is a thing.

  Therefore, according to the present invention, T38 data can be exchanged using the INFO message, which is a call control message that can be exchanged with the counterpart terminal via the SIP proxy server device. There is an effect that T38 communication can be performed via the server device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an example of a communication system according to an embodiment of the present invention.

  This communication system is connected to a packet network PN such as the Internet, and controls communication between network facsimile apparatuses FXa and FXb, SIP proxy server apparatus SV, packet network PN and general public network PSTN having a T38 communication function. It consists of a gateway device GW and a group 3 facsimile device GX connected to the general public network PSTN.

  In this communication system, T38 communication performed between the network facsimile apparatus FXa and the network facsimile apparatus FXb is performed via the SIP proxy server apparatus SV. Further, the network facsimile apparatuses FXa and FXb can perform facsimile communication with the group 3 facsimile apparatus GX via the gateway apparatus GW.

  FIG. 2 shows an example of the configuration of the network facsimile apparatus FX (FXa, FXb).

  In the figure, a system control unit 1 performs various control processes such as a control process of each part of the network facsimile apparatus FX and a facsimile transmission control procedure process. The system memory 2 is executed by the system control unit 1. The control processing program and various data necessary for executing the processing program are stored, and the work area of the system control unit 1 is configured. The parameter memory 3 is unique to the network facsimile apparatus FX. The clock circuit 4 outputs current time information.

  The scanner 5 is for reading a document image at a predetermined resolution, the plotter 6 is for recording and outputting an image at a predetermined resolution, and the operation display unit 7 operates the network facsimile apparatus FX. It consists of various operation keys and various displays.

  The encoding / decoding unit 8 encodes and compresses the image signal, and also decodes the encoded and compressed image information into the original image signal. The image storage device 9 performs encoding and compression. This is for storing a large number of image information in the selected state.

  The packet network interface circuit 10 is for connecting the network facsimile apparatus FX to the packet network PN, and the packet network transmission control unit 11 performs various operations with other data terminal apparatuses via the packet network PN. This is for executing communication control processing (including T38 communication control processing for T38 communication) of various predetermined protocol suites for exchanging data.

  The system control unit 1, the system memory 2, the parameter memory 3, the clock circuit 4, the scanner 5, the plotter 6, the operation display unit 7, the encoding / decoding unit 8, the image storage device 9, and the packet network transmission control unit 11 is connected to the internal bus 12, and data exchange between these elements is mainly performed via the internal bus 12.

  Here, in this embodiment, basically, data exchange between terminals connected to the packet network PN is performed by a transmission protocol up to a transport layer called TCP / IP and a higher level than that. A combination with a layer communication protocol (so-called protocol suite) is applied. For example, in the exchange of e-mail data, a communication protocol called SMTP (Simple Mail Transfer Protocol) is applied as an upper layer communication protocol, and SIP (Session Initiation Protocol) is applied as a call control procedure for T38 communication.

  Also, MIME (Multi Purpose Mail Extension) that defines communication protocols such as TCP / IP and SIP and a method for encoding a message exchanged with a partner terminal at the time of communication is issued by each IETF. Specified by the RFC document. For example, RFC is defined as RFC793, IP is defined as RFC793, SIP is defined as RFC3856, RFC3857, RFC3858, RFC3994, etc., and MIME is defined as RFC2045-2049.

  In this embodiment, when T38 communication is performed between the network facsimile apparatus FXa and the network facsimile apparatus FXb, as shown in FIG. 3, the call control message and T38 communication data (T38) are transmitted via the SIP proxy server apparatus SV. Data).

  As described above, the SIP proxy server apparatus SV discards even if it receives T38 data. That is, since the SIP proxy server apparatus SV does not proxy T38 data, a call control channel for exchanging call control messages is set. Even if the T38 data communication channel is used as it is, T38 data communication cannot be performed.

  Therefore, in this embodiment, T38 data is exchanged using the INFO message of the call control message. The INFO message is guaranteed to carry user-specified data because the user data portion included in the INFO message is guaranteed not to be interpreted by the SIP proxy server apparatus SV.

  In other words, the T38 data encapsulated in the INFO message is exchanged between the network facsimile apparatus FXa and the network facsimile apparatus FXb via the SIP proxy server apparatus SV, so that the network facsimile apparatus FXa and the network facsimile apparatus FXb are exchanged. The T38 communication can be realized in a state where security is ensured.

  The T38 data arranged in the user data of the INFO message is, for example, image information (image data) or the like that is binary data, and therefore is encoded according to MIME.

  An example of the communication procedure in this case is shown in FIG. In this case, the network facsimile apparatus FXa makes a call to the network facsimile apparatus FXb to perform T38 communication.

  First, the network facsimile apparatus FXa requests the SIP proxy server apparatus SV to establish a call control TCP / UDP channel with the network facsimile apparatus FXb. As a result, the SIP proxy server apparatus SV establishes a call control channel between the network facsimile apparatus FXa and the network facsimile apparatus FXb.

  Next, the network facsimile apparatus FXa transmits an INVITE message, which is a request for establishing a T38 communication session, to the network facsimile apparatus FXb via the SIP proxy server apparatus SV, whereby the network facsimile apparatus FXb receives the INVITE message. If “200” is received, “200” indicating a normal response is transmitted to the network facsimile apparatus FXa via the SIP proxy server apparatus SV.

  The network facsimile apparatus FXa that has received “200” transmits an ACK message for notifying permission of session establishment to the network facsimile apparatus FXb via the SIP proxy server apparatus SV.

  As a result, the information exchange related to the communication operation is completed between the network facsimile apparatus FXa and the network facsimile apparatus FXb, and thereafter, T38 data for T38 communication is appropriately exchanged using the INFO message. Image information is communicated from the facsimile apparatus FXa to the network facsimile apparatus FXb.

  In this communication operation, the call control procedure negotiates that the T38 communication using the INFO message is performed between the network facsimile apparatus FXa and the network facsimile apparatus FXb. Such negotiation is performed as follows. Done.

  First, as shown in FIG. 5, the network facsimile machine FXa includes a keyword “special” indicating that it has a communication function for performing T38 communication using an INFO message, in the header information of the INVITE message, in the User-Agent field. At the end of.

  Thereby, the network facsimile apparatus FXb can recognize that the counterpart terminal has a communication function for performing T38 communication using the INFO message.

  On the other hand, when transmitting “200” as a normal response, the network facsimile apparatus FXb describes the keyword “special” similar to FIG. 5 at the end of the User-Agent field of the message header information (not shown).

  In this way, the terminal performs T38 communication using the INFO message by the keyword (in this case, “special”) described in a specific field of the message header information (in this case, “User-Agent field”). If the other terminal side includes a specific keyword in the specific field of the message header information of the received call control message, the other terminal is notified. It can be recognized that (the transmission side of the received message) has a communication function for performing T38 communication using the INFO message.

  In the exchange of the INFO message, the transmission of the INFO message and the normal response “200” from the side that has received the INFO message form a set, and communication of one T38 data is performed.

  FIG. 6 shows an example of a general T38 communication procedure. In this figure, it is performed after a communication path (communication channel) is established between the transmission side (network facsimile apparatus FXa in the example of FIG. 4) and the reception side (network facsimile apparatus FXb in the example of FIG. 4). The communication procedure in the T38 session is shown (that is, the call control procedure is omitted).

  The outline of the T38 communication procedure will be described. First, when a communication path between the transmission side and the reception side is established, the reception side makes the ITU-T recommendation T.30. A signal (T30IND: CED) corresponding to a predetermined tone signal CED (called station identification signal) of 30 procedures is transmitted to the transmitting side, and a signal corresponding to a flag signal (T30IND: Flag) is followed by group 3 facsimile transmission. It is a procedure signal, a signal NSF for notifying its own optional transmission function, a signal CSI for notifying its own identification signal, and a signal for notifying its standard transmission function A signal (V21HDLC: NSF / CSI / DIS) corresponding to each DIS is sequentially transmitted to the transmission side.

  Thereby, the transmitting side knows the identification signal and the transmission function of the receiving side, and based on the notified transmission function, sets the transmission function and modem speed to be used at that time. Next, the transmitting side is a group 3 facsimile transmission procedure signal following the signal (T30IND: Flags) corresponding to the flag signal, and notifies the signal TSI for notifying its own terminal identification signal and the transmission function to be used. The signal (V21HDLC: TSI / DCS) respectively corresponding to the signal DCS for transmission is transmitted to the receiving side.

  Thereby, when the receiving side receives the signal (V21HDLC: TSI / DCS), it acquires the identification information of the counterpart terminal (transmitting side) and the transmission function used at that time.

  Then, the receiving side is a group 3 facsimile transmission procedure signal following the signal (T30IND: Flags) corresponding to the flag signal, and a signal (V21HDLC: CFR) corresponding to the signal CFR for notifying that the reception preparation is completed. ) To the sender.

  In this way, when the image information is ready to be transmitted, the transmitting side transmits a signal (T30IND: Speed) corresponding to a training signal for modem retraining to the receiving side, and then transmits The image data of the image information is divided into a plurality of pieces, and each divided image information is transmitted to the receiving side as packet data (indicated as “V.17 non ECM: Image data” in FIG. 6).

  When the transmission of the image information is completed, a signal (T30IND: Flags) corresponding to the flag signal is transmitted to the receiving side, and the signal EOP corresponding to the group 3 facsimile procedure signal, which indicates that the image information transmission is terminated, is supported. A signal (V21HDLC: EOP) is transmitted to the receiving side.

  On the other hand, when the receiving side receives the signal (T30IND: Speed), the receiving side shifts to preparation for receiving the image information. When the receiving side receives the packet carrying the image information, the divided image information included in the received information is sequentially taken out and the combined image information is received. And the image information is stored in the image storage device 9. In this case, since the signal (V21HDLC: EOP) is received as the post-transmission signal after receiving the image information, it is confirmed that the reception of the image information is completed.

  If the reception result of the image information at that time is good, the reception side is a group 3 facsimile procedure signal following the signal corresponding to the flag signal (T30IND: Flags), and the reception of the image information is normally completed. A signal (V21HDLC: EOP) corresponding to the signal MCF indicating the fact is transmitted to the transmission side.

  Thereby, the transmission side recognizes that the image information has been normally received on the reception side. After this, the transmission side receives the signal (V21HDLC: DCN) corresponding to the signal DCN for instructing line restoration, which is a group 3 facsimile procedure signal, following the signal corresponding to the flag signal (T30IND: Flags). Send to.

  In the communication procedure of FIG. 4, the T38 data arranged in the user data of the INFO message is the respective signal element shown in FIG. In FIG. 4, for convenience of explanation, it is described that the first INFO message is transmitted from the network facsimile apparatus FXa to the network facsimile apparatus FXb. However, according to the communication procedure of FIG. It is transmitted from the facsimile apparatus FXb to the network facsimile apparatus FXa.

  That is, first, an INFO message carrying a signal (T30IND: CED) from the network facsimile apparatus FXb is transmitted to the network facsimile apparatus FXa via the SIP proxy server apparatus SV, and then a signal (T30IND: Flag) is transmitted from the network facsimile apparatus FXb. Is transmitted to the network facsimile apparatus FXa via the SIP proxy server apparatus SV.

  Thereafter, signals constituting the procedure of FIG. 6 are similarly exchanged between the network facsimile apparatus FXa and the network facsimile apparatus FXb.

  By arranging T38 data in the user data of the INFO message in this way, T38 communication can be performed between the network facsimile apparatus FXa and the network facsimile apparatus FXb via the SIP proxy server apparatus SV, and security is improved. Image communication is possible.

  FIG. 7 shows an example of the operation of the network facsimile apparatus FX (FXa, FXb).

  First, a call control channel is established with a partner terminal (process 101). Next, a call control message is exchanged using the established call control channel to negotiate a communication function or the like (process 102).

  In this negotiation, it is checked whether or not the partner apparatus has a T38 communication function using an INFO message exchanged using the call control channel (decision 103). In the above example, it is checked whether or not the keyword “special” is described in the “User-Agent field” of the message header information.

  When the result of determination 103 is YES, the communication procedure of FIG. 4 is executed, and T38 communication is performed using an INFO message exchanged using the call control channel (process 104).

  When the result of determination 103 is NO, a T38 data transmission channel is established according to the conventional communication procedure shown in FIG. 14 (process 105), and the T38 data transmission channel established in process 105 is used. Data transfer is performed (process 106).

  By the way, when T38 communication is performed using an INFO message exchanged using the call control channel, the communication traffic of the SIP proxy server apparatus SV increases by the amount of the communication.

  Therefore, when the network load with the SIP proxy server apparatus SV is high, it is preferable to reduce the transmission rate of T38 data.

  An example of the processing in that case is shown in FIG.

  First, a call control channel is established with a partner terminal (process 201). Next, a call control message is exchanged using the established call control channel to negotiate a communication function or the like (process 202).

  In this negotiation, it is checked whether or not the partner apparatus has a T38 communication function using an INFO message exchanged using the call control channel (decision 203). In the above example, it is checked whether or not the keyword “special” is described in the “User-Agent field” of the message header information.

  When the result of determination 203 is YES, it is checked whether the network is heavily loaded (determination 204). The network load can be measured, for example, by providing a measuring device or detecting a loss rate (packet loss rate) of packets exchanged with the SIP proxy server device SV in a call control procedure. When the packet loss rate is larger than a predetermined value, it can be determined that the network is heavily loaded.

  When the result of determination 204 is YES, the transmission rate of the T38 data is set low by increasing the transfer interval of the packets constituting the INFO message to some extent (processing 205). Further, when the result of determination 204 is NO, processing 205 is not executed.

  Then, the processing shifts to processing 206, the communication procedure of FIG. 4 is executed, and T38 communication is performed using an INFO message exchanged using the call control channel.

  When the result of determination 203 is NO, a T38 data transmission channel is established according to the conventional communication procedure shown in FIG. 14 (process 207), and the T38 data transmission channel established in process 207 is used. Data transfer is performed (process 208).

  Further, when the network is heavily loaded, an increase in network traffic can also be suppressed by reducing the size of the packet carrying the INFO message.

  An example of the processing in that case is shown in FIG.

  First, a call control channel is established with a partner terminal (process 301). Next, a call control message is exchanged using the established call control channel to negotiate a communication function or the like (process 302).

  In this negotiation, it is checked whether or not the partner apparatus has a T38 communication function using an INFO message exchanged using the call control channel (decision 303). In the above example, it is checked whether or not the keyword “special” is described in the “User-Agent field” of the message header information.

  When the result of determination 303 is YES, it is checked whether the network is heavily loaded (determination 304). For the measurement of the network load, the method described in the explanation of FIG. 8 can be adopted.

  When the result of determination 304 is YES, the size of the packet constituting the INFO message is set to a small value (process 305). Further, when the result of determination 304 is NO, processing 305 is not executed.

  Then, the process proceeds to processing 306, the communication procedure of FIG. 4 is executed, and T38 communication is performed using an INFO message exchanged using the call control channel.

  If the result of determination 303 is NO, a T38 data transmission channel is established according to the conventional communication procedure shown in FIG. 14 (process 307), and the T38 data transmission channel established in process 307 is used. Data transfer is performed (process 308).

  In addition, when the network is heavily loaded, communication is temporarily stopped, and when the network load is reduced, the communication operation is performed again, so that communication at the time of heavy load can be performed. Can be avoided.

  An example of the processing in that case is shown in FIG.

  First, a call control channel is established with a partner terminal (process 401). Next, a call control message is exchanged using the established call control channel to negotiate a communication function or the like (process 402).

  In this negotiation, it is checked whether or not the partner apparatus has a T38 communication function using an INFO message exchanged using the call control channel (decision 403). In the above example, it is checked whether or not the keyword “special” is described in the “User-Agent field” of the message header information.

  When the result of determination 403 is YES, it is checked whether the network is heavily loaded (determination 404). For the measurement of the network load, the method described in the explanation of FIG. 8 can be adopted.

  When the result of determination 404 is NO, the communication procedure of FIG. 4 is executed, and T38 communication is performed using an INFO message exchanged using the call control channel (process 405).

  On the other hand, when the result of determination 404 is YES, the communication operation is temporarily stopped (process 406). Then, the process waits until the load on the network becomes low (YES loop of determination 407). When the load on the network decreases (the result of determination 407 is NO), the process returns to process 401 to perform communication operation again.

  If the result of determination 403 is NO, a T38 data transmission channel is established according to the conventional communication procedure shown in FIG. 14 (process 408), and the T38 data transmission channel established in process 408 is used. Data transfer is performed (process 409).

  Further, when a plurality of SIP proxy server devices SV are provided (not shown), even if the network load with a certain SIP proxy server device SV is high, other SIP proxy server devices SV ( In some cases, the T38 communication may be performed by using the latter SIP proxy server device SV.

  An example of the processing in that case is shown in FIG.

  First, a call control channel is established with a partner terminal (process 501). Next, a call control message is exchanged using the established call control channel to negotiate a communication function or the like (process 502).

  In this negotiation, it is checked whether or not the partner apparatus has a T38 communication function using an INFO message exchanged using the call control channel (decision 503). In the above example, it is checked whether or not the keyword “special” is described in the “User-Agent field” of the message header information.

  When the result of determination 503 is YES, it is checked whether the network is heavily loaded (determination 504). For the measurement of the network load, the method described in the explanation of FIG. 8 can be adopted.

  When the result of determination 504 is NO, the communication procedure of FIG. 4 is executed, and T38 communication is performed using an INFO message exchanged using the call control channel (process 405).

  On the other hand, when the result of determination 404 is YES, the communication operation is temporarily stopped (process 406). Then, another SIP proxy server apparatus SV is selected (process 507), the process returns to process 501, and a communication operation using the SIP proxy server apparatus SV selected in process 507 is performed.

  If the result of determination 503 is NO, a T38 data transmission channel is established according to the conventional communication procedure shown in FIG. 14 (process 508), and the T38 data transmission channel established in process 508 is used. Data transfer is performed (process 509).

  FIG. 12 shows an example of still another process of the network facsimile apparatus FX.

  First, a call control channel is established with a partner terminal (process 601). Next, a call control message is exchanged using the established call control channel to negotiate a communication function or the like (process 602).

  In this negotiation, it is checked whether or not the partner apparatus has a T38 communication function using an INFO message exchanged using the call control channel (decision 603). In the above example, it is checked whether or not the keyword “special” is described in the “User-Agent field” of the message header information.

  When the result of determination 603 is YES, the packet arrival time to the SIP proxy server apparatus SV is measured (process 604). For measuring the packet arrival time, an application using ICMP (Internet Control Protocol; refer to RFC 4443) can be used.

  Then, it is checked whether or not the packet arrival time measured in the process 604 is larger than a predetermined threshold t (decision 605). Here, an appropriate value can be adopted as the value of the threshold value t.

  When the result of determination 605 is YES, the transmission rate of the T38 data is set low by increasing the transfer interval of the packets constituting the INFO message to some extent (processing 606). Further, when the result of determination 605 is NO, processing 606 is not executed.

  Then, the process proceeds to processing 607, the communication procedure of FIG. 4 is executed, and T38 communication is performed using an INFO message exchanged using the call control channel.

  When the result of determination 603 is NO, a T38 data transmission channel is established according to the conventional communication procedure shown in FIG. 14 (process 608), and the T38 data transmission channel established in process 608 is used. Data transfer is performed (process 609).

  As described above, according to the present invention, the T38 communication is performed using the INFO message exchanged using the call control channel. Therefore, the network facsimile apparatus FXa and the network are connected via the SIP proxy server apparatus SV. T38 communication can be realized between the facsimile machines FXb, and as a result, security when performing T38 communication can be improved.

The block diagram which showed an example of the communication system concerning one Example of this invention. The block diagram which showed an example of the structure of the network facsimile apparatus FX (FXa, FXb). The block diagram which illustrated the outline of the communication mode of a present Example. The sequence diagram which showed an example of the basic transmission procedure of a present Example using SIP proxy server apparatus SV. Schematic which showed an example of the SIP message header. T.A. The sequence diagram which showed an example of the communication procedure in 38 sessions. 6 is a flowchart showing an example of processing of the network facsimile apparatus. 10 is a flowchart showing another example of processing of the network facsimile apparatus. 10 is a flowchart showing still another example of processing of the network facsimile apparatus. 10 is a flowchart showing still another example of processing of the network facsimile apparatus. 10 is a flowchart showing still another example of processing of the network facsimile apparatus. The flowchart which showed another example of the process of a network facsimile apparatus. The block diagram which showed the outline of the communication aspect of basic T38 communication. The sequence diagram which showed an example of the conventional basic transmission procedure using SIP proxy server apparatus SV.

Explanation of symbols

FX, FXa, FXb Network facsimile equipment SV SIP proxy server equipment

Claims (7)

ITU-T recommendation T.264 via the SIP proxy server device. A communication terminal device for performing image communication by 38 communication,
When a call control channel for performing call control of communication with a partner terminal is established via the SIP proxy server device, an INFO message exchanged with the partner terminal via the call control channel is transferred to T38 according to the T38 communication procedure. A communication terminal apparatus comprising communication control means for performing image communication by sequentially arranging data according to the progress of a T38 communication procedure and exchanging the INFO message with a partner terminal.   The communication control means arranges a keyword indicating that it has a function of performing T38 communication using an INFO message in the header information of a message transmitted to the counterpart terminal during call control, and communicates with the counterpart terminal during call control. The communication terminal apparatus according to claim 1, wherein the function is negotiated.   When the communication load with the proxy server device is larger than a predetermined value before the start of T38 communication using the INFO message, the communication control means sets the packet size of T38 data to be arranged in the INFO message during T38 communication. 3. The communication terminal apparatus according to claim 1, wherein the communication terminal apparatus is set to a small value.   If the packet arrival time with the proxy server device is larger than a predetermined value before the start of T38 communication using the INFO message, the communication control means may set the packet size of T38 data to be arranged in the INFO message during T38 communication. The communication terminal apparatus according to claim 1 or 2, wherein is set to a small value.   If the communication load with the proxy server device is larger than a predetermined value before the start of T38 communication using an INFO message, the communication control means stops T38 communication and shifts to a recommunication state. The communication terminal device according to claim 1 or 2, characterized by the above.   When the communication load with the proxy server device is larger than a predetermined value before the start of T38 communication using the INFO message, the communication control unit stops the T38 communication and uses another proxy server device. The communication terminal apparatus according to claim 1 or 2, wherein re-communication is performed. ITU-T recommendation T.264 via the SIP proxy server device. 38. A control method of a communication terminal device for performing image communication by 38 communication,
When a call control channel for performing call control of communication with a partner terminal is established via the SIP proxy server device, an INFO message exchanged with the partner terminal via the call control channel is transferred to T38 according to the T38 communication procedure. A method of controlling a communication terminal apparatus, wherein data is sequentially arranged according to the progress of a T38 communication procedure, and image communication is performed by exchanging the INFO message with a partner terminal.