Network communication apparatus, communication system and communication method

A network terminal apparatus in a type of directly connecting to a packet communication network, with an interface for connecting to a circuit under an environment of an SIP terminal network, and a capability of carrying out facsimile transmission/reception, carries out a call control method according to SIP, transmits and receives an SDP added to a message body of an SIP, and carries out, in a same session, both a call control session transmitting and receiving an SIP message and an SDP and a T.38 session transmitting and receiving a T.38 signal.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to a network communication apparatus, a communication system and a communication method, and, in particular, to a network communication apparatus, a communication system and a communication method in which the network communication apparatus is in a packet network direct connectable type, has an interface for connecting to a LAN circuit under network environment for SIP terminals, and has a capability to carry out facsimile transmission/reception.

2. The Description of the Related Art

In general, in a network communication apparatus in a packet network direct connectable type having an interface for connecting to a local area network under environment of a network for SIP terminals and having a capability of carrying out facsimile transmission/reception, it is necessary to establish a data channel for each of both directions for carrying out data transfer for the purpose of mutual communication between network communication apparatuses (see Japanese Laid-open Patent Application No. 2001-292267).

SUMMARY OF THE INVENTION

Further, it is necessary to carry out call connection first for the purpose of establishing a data channel, and, therefore, it is necessary to establish one call connection channel and two data channels. For the call connection channel, normally a Well-known port is allocated, while, a data channel is dynamically determined during a call connection procedure. Thereby, in a case where communication is carried out via a firewall, or in a case where a network communication apparatus carries out communication via a NAT (network address translation), a port for the thus-determined data channel may not be one with which data cannot pass through the firewall or the NAT, whereby communication may not be carried out.

An object of the present invention is to provide a network communication apparatus, a communication system and a communication method by which data transmission can be carried out with the use of a call connection channel under SIP environment.

According to the present invention, a network communication apparatus in a type of directly connectable with to a packet communication network, having an interface for connecting to a circuit under an environment of a communication network for SIP terminals, and having a capability of carrying out facsimile transmission/reception, includes: a call control part carrying out a call control process in an SIP; and an SDP control part transmitting and receiving an SDP added to a message body of the SIP, wherein: the network communication apparatus carries out, in a same session, both a call control session transmitting and receiving an SIP message and an SDP, and a T.38 session transmitting and receiving a T.38 signal.

In this configuration, since a same channel as a call connection channel once established for an SIP is also used to carry out T.38 data transfer, and thus, data can be transferred with the use of a Well-known port, it is possible to reduce a required resource such as a memory, and also, T.38 data transfer can be carried out properly even in a case where communication is carried out via a firewall, or in a case where the network communication apparatus carries out communication via a NAT.

The network communication apparatus may further include: a determining part determining whether or not the SIP session and the T.38 session can be carried out in a same session, wherein: in a case of requesting carrying out of the SIP session and the T.38 session in a same session and determining previously that data transfer can be carried out in a same session, the network communication apparatus omits transmission of a BYE message and a responding message therefor in the SIP.

In this configuration, since it can be determined whether a terminal in a counterpart has a same capability as that of an own terminal by adding terminal information to an SPD, and then, a procedure of a BYE (finish) message in the SIP and a responding message (200 OK) thereto can be omitted, it is possible to carry out finishing processing within a shorter time.

The network communication apparatus may further include: a determining part determining whether or not the SIP session and the T.38 session can be carried out in a same session, wherein: in a case of once requesting carrying out of the SIP session and the T.38 session in a same session while not being able to determine that data transfer can be carried out in a same session, the communication apparatus receives a BYE message in the SIP after completion of T.38 communication, and transmits a responding message therefor.

In this configuration, since it can be determined whether a terminal in a counterpart does not have a same capability as that of an own terminal by adding terminal information to an SPD, it is possible to determine whether or not a procedure of a BYE (finishing) message in the SIP and a responding message (200 OK) thereto is necessary, and, it is possible to also carry out communication with the use of a normal sequence when it is determined that the above-mentioned procedure is necessary.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to accompanying figures, a preferred embodiment of the present invention are described next in detail.

FIG. 1shows a network system according to an embodiment of the present invention. In this network system, call control or such for network communication is carried out under an SIP (session initiation protocol: see RFC3261 for details) environment basically.

As shown inFIG. 1, to a local area network LAN, two T38 terminal apparatuses TT1and TT2which carry out internet facsimile communication in a real-time type in compliance with ITU-T recommendation T.38 (acting as a calling-side T38 terminal apparatus and a called-side T38 terminal apparatus), a work station WS for carrying out various sorts of data processing (including data communication under the SIP environment), a VoIP telephone terminal TL for carrying out voice communication via an IP network such as the local area network LAN and an analog telephone terminal TLa are connected. Also, to the local area network LAN, a VoIP terminal adapter TA for carrying out interface conversion for the analog telephone terminal TLa for enabling the analog terminal TLa to carry out voice communication via an IP network such as the local area network LAN, and an SIP server apparatus SV having functions of a proxy server, a redirect server and a registration server are connected. Also, a configuration is provided such that communication with a group 3 facsimile apparatus GX which is connected with an analog public network PSTN and also with the local area network LAN via a VoIP gateway GW, is made possible.

The VoIP terminal adapter TA has a call control function under the SIP environment.

FIG. 2shows one example of a configuration of each of the T38 terminal apparatuses TT (TT1and TT2).

InFIG. 2, a system control part1carries out various sorts of control processing such as processing of controlling various parts of the T38 terminal apparatus TT, processing of real-time transmission control procedure (procedure in compliance with the ITU-T recommendation T.38) and so forth. A system memory2stores control processing programs executed by the system control part1, various sorts of data required by the system control part1to execute the processing programs, and so forth, and also, provides a work area for the system control part1. A parameter memory3stores various sorts of information unique to the T38 terminal apparatus TT. A clock circuit4outputs current time information.

A scanner5reads original image information with a predetermined resolution. A plotter6carries out recording output of an image with a predetermined resolution. An operation and display part7is used for operating this facsimile apparatus and includes various sorts of keys, and various sorts of display devices.

A coder/decoder8carries out coding and compression of an image signal and decoding once coded and compressed image information into an image signal. An image storage device29stores many sets of image information in a coded and compressed state.

A LAN interface circuit12connects the T38 terminal apparatus TT to the local area network LAN, and, enables transmission/reception of various sorts of data via the local area network LAN. A TCP/IP packet analysis part13obtains received information from a TCP/IP packet once received via the IP network interface circuit12, as a result of analyzing it, in a TCP mode. A UDP packet analysis part14obtains received information from a UDP packet once received via the IP network interface circuit12, as a result of analyzing it, in an UDP mode.

A group 3 protocol information generation part15converts received information output from the TCP/IP packet analysis part13into corresponding group 3 transmission procedure signal information in a TCP mode, and also, converts received information output from the UDP packet analysis part14into corresponding group 3 transmission procedure signal information in a UDP mode, in a real-time transmission procedure.

A group 3 protocol information obtaining part16obtains group 3 facsimile transmission procedure information to be transmit in a real-time transmission procedure. A TPC/IP packet conversion part17converts group 3 facsimile transmission procedure information output from the group 3 protocol information obtaining part16into TCP/IP packet data in a TCP mode, and, an output thereof is provided to the IP network interface circuit12.

A UDP packet conversion part18converts group 3 facsimile transmission procedure information output from the group 3 protocol information obtaining part16into UDP packet data in an UDP mode, and, an output thereof is provided to the IP network interface circuit12.

An SIP/SDP communication control part19carries out call control processing or such with the use of an SIP and an SDP (session description protocol; see RFC2327 for details).

These system control part1, system memory2, parameter memory3, clock circuit4, scanner5, plotter6, operation and display part7, coding and decoding part8, image storage part9, group 3 protocol information generation part15, group 3 protocol information obtaining part16and SIP/SDP communication control part19are connected with an internal bus20, and, data transmission/reception thereamong are carried out mainly with the use of the internal bus20.

FIG. 3shows one example of a basic transmission procedure applied when communication is carried out mutually between the T38 terminal apparatuses TT1and TT2under the SIP environment.

First, the calling-side T38 terminal apparatus establishes a call control channel (channel for carrying out call control) with the called-side T38 terminal apparatus with the use of the SIP server apparatus SV.

Then, the calling-side terminal apparatus transmits a message INVITE to the called-side T38 terminal apparatus. Then, the called-side T38 terminal apparatus, when it can respond thereto, responds to the message INVITE with a message 200 (OK). Thereby, the calling-side T38 terminal apparatus determines that communication can be carried out, and thus transmits a message ACK to the called-side T38 terminal apparatus. Thereby, a call is established between the calling-side T38 terminal apparatus and the called-side T38 terminal apparatus.

After that, the calling-side T38 terminal apparatus and the called-side T38 terminal apparatus establish T38 data channels (channel for data transmission) for each of these T38 terminal apparatuses for the purpose of data transmission and data reception therebetween. After that, with the use of the thus-established T38 data channels, T38 packets are transmitted/received, and thus, image information communication is carried out therebetween.

After the image information communication is finished, a message BYE is transmitted from the calling-side T38 terminal apparatus to the called-side T38 terminal apparatus with the use of the call control channel. The called-side T38 terminal apparatus returns a responding message (200 OK) to the calling-side T38 terminal apparatus. Thereby, the call control connection between the calling-side T38 terminal apparatus and the called-side T38 terminal apparatus is finished.

In this transmissions procedure, a port number allocated for the T38 data channel is dynamically changed, and thus, is not fixed. Thereby, when the T38 terminal apparatus carries out communication via a firewall or via a NAT, a packet of the thus-set port number may not pass through the firewall or the NAT.

In order to solve this problem, according to the embodiment of the present invention, as shown inFIG. 4, data communication is made to be carried out with the use of a port same as that of the call control channel. For this purpose, the calling-side T38 terminal apparatus sets an SDP, in which setting is made such that a port of the call control channel may also be allocated for a data transmission channel, in a body of the message INVITE, when transmitting the message INVITE to the called-side T38 terminal apparatus.

In other words, in the SIP message (the message INVITE, the responding message thereto, or such), the SDP is added to the message body thereof, and then, a data channel is established according to the contents of the thus-added SDP. Then, after the port same as that of the call control channel is also allocated for the data channel in each of both the calling-side T38 terminal apparatus and the called-side T38 terminal apparatus, no data channel is newly established, and, the call control channel is used as it is also for exchanging T38 packets (data transfer).

Further, according to the recommendation for SIP (RFC3261), after the message INVITE is transmitted and the responding massage thereto is received, the ACK message is transmitted from the side from which the INVITE message has been transmitted. In this case, after the ACK message is received, it is determined that T38 communication is started, and, a message transferred through the call control channel after that is determined as being a T38 packet.

Furthermore, as shown inFIG. 5, in the SDP, a manufacture code is set. With the use of the manufacture code, determination as to what functions each terminal has is carried out between the own terminal and the counterpart terminal. When it is determined therefrom that the functions of each terminal are same therebetween, the call connection is finished without transmitting a message BYE after the data communication is finished.

In this case, since a message BYE and a responding message thereto (200 OK) are once transmitted and received at a time of finishing communication in SIP communication as part of the data communication, the communication finish can be already recognized mutually between the counterparts therewith. Therefore, a procedure for finishing the call control (with a further message BYE and a responding message thereto) can thus be omitted.

In other words, in the case where a same port is allocated for both a call control channel and a data channel, it is difficult to determine whether a received packet therethrough is an SIP message or a T.38 message. Therefore, according to the embodiment of the present invention, when it is previously recognized from arbitrary information that the counterpart terminal has a capability of carrying out communication via the same port, transmission and reception of a message BYE and a responding message thereto (200 OK) as a call control finishing procedure is omitted, and thus, communication with the use of the same port used for both SIP call control and T.38 data transfer is finished properly without carrying out transmission and reception of a message BYE as a call control finishing procedure, as shown inFIG. 4.

As shown inFIG. 4, according to the embodiment of the present invention, as mentioned above, in comparison to the procedure described above with reference toFIG. 3, the procedure to establish other new data channels are omitted, and also, transmission and reception of the message BYE and the responding message thereto (200 OK) as the call control finishing procedure is omitted.

FIG. 6shows one example of communication processing of the calling-side T38 terminal apparatus.

First, a call control channel is established with the called-side T38 terminal apparatus in Step101. With the use of the thus-established call control channel, a message INVITE is transmitted in Step102, and a responding message thereto (200 OK) is received in Step103.

Then, it is determined whether or not a port number same as a port number allocated for the call control channel is also allocated for a data transmission channel, in Step104. When a result of the determination of Step104is Yes, data transfer is carried out with the use of the call control channel, in Step105.

After the data transfer is completed, it is determined whether or not a manufacture code in an SPD received from the called-side T38 terminal apparatus is same as a value set in the own apparatus, in Step107. When a result of the determination of Step107is Yes, since a call finishing procedure is not carried out, the current operation is finished.

When a result of the determination of Step107is No, a predetermined call finishing sequence is carried out with the use of the call control channel in Step108, and then, the current operation is finished.

When a result of the determination Step104is No, a channel for data transmission is newly established in Step109, and data transfer is carried out with the use of the thus-established channel for data transmission in Step110. Then, after the data transfer is completed, Step108is carried out, a predetermined call finishing sequence is carried out with the use of the call control channel, and then, the current operation is finished.

FIG. 7shows one example of communication processing of the called-side T38 terminal apparatus.

First, a call control channel is established with the calling-side T38 terminal apparatus in Step201. With the use of the thus-established call control channel, a message INVITE is received in Step202, and a responding message thereto (200 OK) is transmitted in Step203.

Then, it is determined whether or not a port number same as a port number allocated for the call control channel is also allocated for a data transmission channel, in Step204. When a result of the determination of Step204is Yes, data transfer is carried out with the use of the call control channel, in Step205.

After the data transfer is completed, it is determined whether or not a manufacture code in an SPD received from the calling-side T38 terminal apparatus is same as a value set in the own apparatus, in Step207. When a result of the determination of Step207is Yes, since a call finishing procedure is not carried out, the current operation is finished.

When a result of the determination of Step207is No, a predetermined call finishing sequence is carried out with the use of the call control channel in Step208, and then, the current operation is finished.

When a result of the determination Step204is No, a channel for data transmission is newly established in Step209, and data transfer is carried out with the use of the thus-established channel for data transmission in Step210. Then, after the data transfer is completed, Step208is carried out, a predetermined call finishing sequence is carried out with the use of the call control channel, and then, the current operation is finished.

Thus, according to the embodiment of the present invention, transfer of T.38 data is carried out with the use of a channel same as a call control channel established originally for SIP. As a result, data transfer can be carried out with the use of a Well-known port, and thereby, it is possible to reduce a required resource such as a memory, and also, it is possible to carry out T.38 data transfer properly even in a case where communication is carried out via a firewall or a NAT.

Further, since it is possible to check as to whether or not a counterpart terminal has a capability same as that of an own terminal by adding terminal information in an SPD, it becomes possible to omit a procedure of a BYE (finishing) message and a responding message thereto (200 OK) which is normally necessary. Thereby, it becomes possible to reduce a time required for carrying out a finishing procedure.

Furthermore, since it is possible to check as to whether or not a counterpart terminal has a capability same as that of an own terminal by adding terminal information in an SPD, it becomes possible to determine that the counterpart terminal does not have the same capability. Thereby, it is possible to determine whether or not a procedure of a BYE (finishing) message and a responding message thereto (200 OK) is necessary, and, it is possible to apply a normal sequence if it is then determined that the procedure for a BYE (finishing) message and a responding message thereto (200 OK) is necessary.

The present application is based on the Japanese Priority Application No. 2003-319265, filed on Sep. 11, 2003, the entire contents of which are hereby incorporated herein by reference.