Abstract:
An IP communication interface device includes first and second connecting units, and first, second and third processors. The first processor coding first media data as B-channel data inputted to the first connecting unit from a circuit switched network, decoding packet-disassembled media data into which a packet of second media data inputted to the second connecting unit from a LAN is disassembled, and transmitting the decoded media data to the first connecting unit for forwarding as the first media data to the circuit switched network. The second processor packetizing first coded media data, disassembling the packer of the second media data, and transmitting as packet-disassembled media data to the first processor. The third processor generating second media data by adding header data to the packet-assembled media data of the second processors forwarding the second media data to the LAN via the second connecting unit, removing header data, and transmitting the header-less second media data to the second processor.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to a multi switched network system (IP communication network system) capable of reducing costs for equipment and operations by integrating a switched circuit network such as a telephone network with an IP (Internet Protocol) packet switched network such as the Internet or the Intranet, and more particularly to an IP communication interface device and a circuit switch for facilitating a construction of this IP communication network system. 
   With an advancement of a network technology as typified by broadening the band of a local area network (LAN) and an advancement of a PC technology as typified by attaining multifunctions of a personal computer (PC) and a speed-up of a CPU applied to the PC over the recent years, it is on the verge of actualization in terms of utilization that voice data are communicated at a high speed between the PCs on a plurality of LANs. 
   Owing to the advancements of those technologies, application software executed between the PCs on the Internet (including the Intranet as far as it is not used in a particularly limited terminology in this Specification) configured by the LANs and wide area networks (WANs) and a hardware system incorporating this package software, are rapidly put into the market. This system is known as [Internet telephony]. 
   In the IP communication network system known as Internet telephony, an integration of the data communications with the voice communications involves the use of a VoIP (Voice over Internet Protocol) technology. This VoIP technology is that voices (audio data) are segmented into frames at an interval of a short time (on the order of, e.g., 20 sec), and transmitted and received in the form of packets by adding IP headers thereto on a network (IP network) based on a network layer protocol, i.e., Internet Protocol (IP) used on the Internet. 
   Further, there is promoted a development of an interface device, incorporating a gateway function for executing a communication protocol conversion between the telephone network and the Internet, for actualizing the communications between the telephone network and the Internet. 
   Generally, the Internet telephony can be operated at a lower cost than a speech (voice communication) on the phone through the conventional telephone network, and therefore a spread of the IP communication network system and services thereof is being accelerated. 
   A transmission (transfer) standard in this IP communication network system is not yet, however, established. What exists at the present is just ITU-T Recommendation H.450.2 (H.323) that defines the services within the Internet and the services in the conventional telephone network. 
   With diversification and a scale-up of the infrastructures for the communications, the users tend to separately use the communication infrastructure optimal to the purpose. Under such circumstances, it is necessary and indispensable to construct a more economical intra-office communication network system by taking the Internet into the intra-office communication network system and utilizing it for the data communications and the voice communications as well. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is a primary object of the present invention to provide an IP communication network system, incorporating a gateway function for executing a communication protocol conversion between a telephone network (switched circuit network) and the Internet (IP packet switched network), for actualizing a variety of communications such as voice communications and data communications between the telephone network and the Internet. 
   It is another object of the present invention to provide an IP communication network system capable of its being easily introduced into an existing telephone network, especially an intra-office telephone network in order to actualize the variety of communications between the telephone network and the Internet. 
   To accomplish the above objects, according to a first aspect of the present invention, an IP communication interface device comprises first and second connecting units for making it possible to dispose between a switched circuit network and LAN connected to an IP packet switched network, a first processing unit for coding first media-corresponding data as B-channel data inputted to the first connecting unit from the switched circuit network, decoding packet-deassembled media-corresponding data into which a packet of second media-corresponding data inputted to the second connecting unit from the LAN is deassembled, and for transmitting the decoded media-corresponding data to the first connecting unit for forwarding the same data as the first media-corresponding data to the switched circuit network, a second processing unit for assembling the coded media-corresponding data coded by the first processing unit into a packet, deassembling the packet of the second media-corresponding data, and transmitting the same data as packet-deassembled media-corresponding data to the first processing unit, and a third processing unit for generating the second media-corresponding data by adding predetermined header data to the packet-assembled media-corresponding data assembled into a packet by the second processing unit, forwarding the second media-corresponding data to the LAN via the second connecting unit, removing the header data added to the second media-corresponding data inputted to the second connecting unit, and transmitting the second media-corresponding data with the header data removed to the second processing unit. 
   Based on this architecture, the first and second media-corresponding data may include voice data transmitted from a voice terminal having a voice communication function, facsimile data transmitted from a facsimile terminal having a facsimile communication function and data transmitted from a data terminal having a data communication function. 
   Further, the first and second processing units may be functionally divided corresponding to the voice data, the facsimile data and the data that correspond to the first and second media-corresponding data, and the IP communication interface device may further comprise a selecting unit for selecting the first functionally divided processing unit in accordance with a command given from the third processing unit. 
   The second processing unit, when the first media-corresponding data are the voice data or the facsimile data, may generate packet-assembled media-corresponding data to which an RTP for enabling a real time transport to be done is added. 
   The second processing unit, when the second media-corresponding data are the voice data or the facsimile data, may generate packet-deassembled media-corresponding data from which the RTP for enabling the real time transport to be done is removed. 
   The third processing unit, when the packet-assembled media-corresponding data generated by the second processing unit are the voice data or the facsimile data, may add a UDP header and an IP header as the header data, and, when the packet-assembled media-corresponding data are the essential data, may add a TCP header and an IP header as the header data. 
   The third processing unit, when the second media-corresponding data are the voice data or the facsimile data, may remove the UDP header and the IP header added as the header data, and, when the second media-corresponding data are the essential data, may remove the TCP header and the IP header added as the header data. 
   The third processing unit may identify a call control signal as D-channel data in accordance with a message based on a specified protocol, and may penetratingly transmit and receive the call control signal simply by adding and removing the TCP header and the IP header. 
   The first and second connecting units and the first, second and third processing units may be mounted in a package card. 
   According to a second aspect of the present invention, a circuit switch comprises a highway switch accommodating at least one of a voice terminal having a voice communication function, a facsimile terminal having a facsimile function and a data terminal having a data communication function, and including a time division multiplexing transmission path for transmitting data corresponding to media, a first connecting unit connected directly to the highway switch, a second connecting unit for accommodating a LAN line connected to an IP packet switched network, a first processing unit for coding first media-corresponding data as B-channel data inputted to the first connecting unit, decoding packet-deassembled media-corresponding data into which a packet of second media-corresponding data inputted to the second connecting unit is deassembled, and transmitting the decoded media-corresponding data to the first connecting unit in order to forward the same decoded media-corresponding data as the first media-corresponding data to the highway switch, a second processing unit for assembling the coded media-corresponding data coded by the first processing unit, deassembling the packet of the second media-corresponding data, and transmitting the second media-corresponding data as the packet-deassembled media-corresponding data to the first processing unit, and a third processing unit for generating the second media-corresponding data by adding predetermined header data to the packet-assembled media-corresponding data assembled into a packet by the second processing unit, forwarding the second media-corresponding data to the LAN via the second connecting unit, removing the header data added to the second media-corresponding data inputted to the second connecting unit, and transmitting the second media-corresponding data with the header data removed to the second processing unit. 
   According to a third aspect of the present invention, an IP communication network system includes a circuit switch comprising a highway switch accommodating at least one of a voice terminal having a voice communication function, a facsimile terminal having a facsimile function and a data terminal having a data communication function, and including a time division multiplexing transmission path for transmitting data corresponding to media, a first connecting unit connected directly to the highway switch, a second connecting unit for accommodating a LAN line connected to an IP packet switched network, a first processing unit for coding first media-corresponding data as B-channel data inputted to the first connecting unit, decoding packet-deassembled media-corresponding data into which a packet of second media-corresponding data inputted to the second connecting unit is deassembled, and transmitting the decoded media-corresponding data to the first connecting unit in order to forward the same decoded media-corresponding data as the first media-corresponding data to the highway switch, a second processing unit for assembling the coded media-corresponding data coded by the first processing unit, deassembling the packet of the second media-corresponding data, and transmitting the second media-corresponding data as the packet-deassembled media-corresponding data to the first processing unit, and a third processing unit for generating the second media-corresponding data by adding predetermined header data to the packet-assembled media-corresponding data assembled into a packet by the second processing unit, forwarding the second media-corresponding data to the LAN via the second connecting unit, removing the header data added to the second media-corresponding data inputted to the second connecting unit, and transmitting the second media-corresponding data with the header data removed to the second processing unit. 
   According to a fourth aspect of the present invention, an IP communication network system includes an IP communication interface device comprising first and second connecting units for making it possible to dispose between a switched circuit network and LAN connected to an IP packet switched network, a first processing unit for coding first media-corresponding data as B-channel data inputted to the first connecting unit from the switched circuit network, decoding packet-deassembled media-corresponding data into which a packet of second media-corresponding data inputted to the second connecting unit from the LAN is deassembled, and for transmitting the decoded media-corresponding data to the first connecting unit for forwarding the same data as the first media-corresponding data to the switched circuit network, a second processing unit for assembling the coded media-corresponding data coded by the first processing unit into a packet, deassembling the packet of the second media-corresponding data, and transmitting the same data as packet-deassembled media-corresponding data to the first processing unit, and a third processing unit for generating the second media-corresponding data by adding predetermined header data to the packet-assembled media-corresponding data assembled into a packet by the second processing unit, forwarding the second media-corresponding data to the LAN via the second connecting unit, removing the header data added to the second media-corresponding data inputted to the second connecting unit, and transmitting the second media-corresponding data with the header data removed to the second processing unit. 
   According to the present invention, it is feasible to provide the IP communication network system, incorporating the gateway function for executing the communication protocol conversion between the telephone network (switched circuit network) and the Internet (IP packet switched network), for actualizing the variety of communications such as the voice communications and the data communications between the telephone network and the Internet. 
   According to the present invention, it is also possible to provide the IP communication network system capable of its being easily introduced into the existing telephone network, especially the intra-office telephone network in order to actualize the variety of communications between the telephone network and the Internet. 
   As a result, according to the present invention, it is easier to construct the economical circuit switch and IP communication network system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These objects and advantages of the present invention will become more apparent and more readily appreciated from the following detailed description of the presently preferred exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a block diagram showing an architecture of an IP communication network system in one embodiment of the present invention; 
       FIG. 2  is an explanatory block diagram showing a first example of a private branch exchange (PBX) and an IP communication interface device and operations thereof; 
       FIG. 3  is a diagram showing a layout of a control unit and CODECs that are mounted as a package card in the IP communication interface device; 
       FIGS. 4A  to  4 D are explanatory diagrams showing a frame structure of a variety of packets transmitted and received between the IP communication interface device and a LAN line (Internet line); 
       FIG. 5  is an explanatory block diagram showing a second example of the PBX and the IP communication interface device and operations thereof; 
       FIG. 6  is an explanatory block diagram showing a third example of the PBX and the IP communication interface device and operations thereof; and 
       FIG. 7  is an explanatory block diagram showing a fourth example of the PBX and the IP communication interface device and operations thereof. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Next, embodiments of the present invention will hereinafter be discussed with reference to the accompanying drawings. 
   [Architecture of IP Communication Network System] 
     FIG. 1  shows an architecture of an IP communication network system in one embodiment of the present invention. Referring to  FIG. 1 , PBXs (private branch exchanges)  1 ,  2  configuring a telephone network as a switched circuit network respectively accommodate a plurality of terminal devices (which may be simply referred to as terminals in some cases)  3  and a plurality of terminals  4 . These terminal  3 ,  4  are each classified as a telephone terminal incorporating a voice communication function, and a facsimile (FAX) terminal having a FAX communication function, or a data terminal such as a personal computer (PC) having a data communication function. Note that the PBXs  1 ,  2  may also be main devices corresponding to typical PBXs. Further, the PBXs  1 ,  2  are connected to an ISDN relay line to a public switched network, however, their illustrations are herein omitted. 
   IP communication interface devices  5 ,  6  serve to connect the PBXs  1 ,  2  to local area networks (LANs)  7 ,  8 , respectively. The IP communication interface devices  5 ,  6 , which will hereinafter be described in depth, can be provided as package cards into the same boxes as those of the PBXs  1 ,  2 . Unique IP addresses are allocated to the IP communication interface devices  5 ,  6 . 
   In addition to the IP communication interface devices  5 ,  6 , data terminals (not shown) such as PCs each having the data communication function and routers  9 ,  10  serving as relay (routing) devices, are connected to the LANs  7 ,  8 . The LANs  7 ,  8  are configured based on a star network topology such as 10BASE-T (in which a trunk line transmission speed is 10 Mpbs, a base band modulation method is adopted, and a transmission medium involves the use of a twisted pair cable) or 100BASE-TX, and may also be configured by using other network topologies such as a bus network. 
   An Internet  11  as an IP packet switched network (IP network) is connected to the routers  9 ,  10 . This Internet  11  is strictly categorized as the Intranet when the IP packet switched network is an intra-office network, however, there is herein no particular distinction in terminology. Further, the Internet  11  is constructed of a leased line, ISDN LAN and WAN. The IP communication network system can be configured based on this architecture. 
   [First Example of Architectures and Operations of Private Branch Exchange and IP Communication Interface Device] 
   (Private Branch Exchange) 
   A first PBX  20  corresponding to the PBXs  1 ,  2  in IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 2 , includes a voice terminal (subscriber) control unit  21 , a highway switch  22 , a trunk control unit  23  and a central control unit  24 . 
   The voice terminal control unit  21  accommodates a voice terminal (telephone)  31  incorporating a voice communication function through a subscriber line, and is connected to the highway switch  22 . The voice terminal control unit  21  controls detection of calling, response and disconnection, controls a receipt of dialing and controls a calling signal with respect to the voice terminal  31 . The voice terminal control unit  21  also controls receiving operations when the voice terminal  31  is set on a receiving side. 
   The highway switch  22  is constructed of a time division multiplexing transmission path (Highway: HW) having [nB+D] (n=1˜31) channels, and has a capacity of, e.g., 2 Mbps (64 Kbps×32 time slots TS). The trunk control unit  23  accommodates an ISDN relay line of BRI (Basic Rate Interface, which is a basic interface having a transmission speed of 192 Kbps) or PRI (Primary Rate Interface, which is a primary group speed interface having a transmission speed of 1.544/2.048 Mbps) that is connected to the public switched network. The trunk control unit  23  serves to transmit and receive voice data (Bch data) of a B channel and control data (Dch data) of a D channel. Further, the trunk control unit  23  is connected directly to the highway switch  22 . 
   The central control unit  24  switches the lines by controlling the voice terminal control unit  21 , the highway switch  22  and the trunk control unit  23 , respectively. Moreover, the central control unit  24  executes setting, canceling and outputting of station data via a maintenance/operation interface (unillustrated). 
   (IP Communication Interface Device) 
   Next, a first IP communication interface device  40  corresponding to the IP communication interface devices  5 ,  6  in the IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 2 , includes a control unit  50  and a CODEC  60 . The control unit  50  and the CODEC  60  are constructed of an individual or one piece of package card, and this package card is mounted as the IP interface device  40  into the same box as that of the PBX  20  described above.  FIG. 3  is a diagram showing a layout of the control unit  50  and the CODECs  60 , which are mounted in the single package card. 
   The control unit  50  comprises a highway switch interface (that will hereinafter be abbreviated to HW-IF in some cases)  51 , a LAN interface (that will hereinafter be abbreviated to LAN-IF as the case may be)  52 , a signal processing unit  53  provided in a CPU (Central Processing Unit), and an internal bus  54 . The control unit  50  transmits and receives packets corresponding to media with an Internet line via a LAN line, which are voice packets in this example. Further, the control unit  50  is connected to the highway switch  22  of the PBX  20  and to the LANs  7 ,  8 , and controls the CODECs  60  to assemble and deassemble the packets of data corresponding to the media, i.e., the voice data in this example. 
   The HW-IF  51  connected directly to the highway of the highway switch  22  takes line data of 64 Kbps out of this highway (a transmission speed thereof is, e.g., 2 Mbps) and inserts the line data of 64 Kbps into the highway of the highway switch  22 . The LAN-IF  52  is connected to the LANs  7 ,  8  and controls electric/physical interfaces of the LAN lines in the LAN topology, i.e., 10BASE-T or 100BASE-TX in this example. The signal processing unit  53  establishes calls between connection type communications on the side of the switched circuit network of the PBX  20  and connectionless type communications on the side of the Internet, and processes an end call control signal. 
   Further, the CODEC  60  connected to the control unit  50  is constructed of a dropper/inserter (which hereinafter might be referred to as TS-CNTL)  61 , a dual port memory (which hereinafter might be termed DPRAM)  62 , a first processing unit  62  composed of a digital signal processor (DSP) and having a coding/decoding function, a second processing unit  64  provided in the CPU and having a packet assembling/deassembling function, and an internal bus  65 . The CODEC  60  assembles and deassembles the packet of the data corresponding to the media, i.e., the voice data in this example. 
   The TS-CONTL  61  takes the data out of a 64 Kbps time slot of an internal transmission path between the control unit  50  and the CODEC  60 , and inserts the data into the same time slot. The DPRAM  62  enables the signal processing unit  53  of the control unit  50  and the second processing unit  64  of the CODEC  60  to perform the internal communications therebetween. 
   The first processing unit  63  executes a process of coding continuous signals of the voice data taken out of the time slot in the TS-CNTL  61  into discrete signals of the voice packet to the Internet line. Further, the first processing unit  63  executes a process of decoding the voice packet forwarded from the Internet line into the continuous signals of the voice data, whereby the decoded signals can be inserted into the predetermined time slot in the TS-CNTL  61 . 
   The second processing unit  64  controls the first processing unit  63 , and executes the packet assembly including an addition of RTP (Real Time Transport Protocol) for enabling a real time transport to be carried out and a packet deassembly including an elimination of RTP. Note that the CODECs  60  are extensible corresponding to an increase in the number of output channels to the LANs  7 ,  8  from the IP communication interface device  40 . 
   The IP communication interface device  40  is connected directly to the highway of the highway switch  22  via the HW-IF  51 , and may therefore be treated as a [trunk device] embraced by the ISDN relay line as viewed from the PBX  20 . 
   (Operation) 
   In the first IP communication interface device  40  taking the architecture described above, the voice data (Bch data) are inputted via the HW-IF  51  of the control unit  50  to the TS-CNTL  61  of the CODEC  60  from the highway switch  22  of the PBX  20 . 
   The voice data inputted to the TS-CNTL  61  are coded in the first processing unit  63  and subjected to a voice compression and a silence compression according to ITU-T G.729 Annex A/B. The coded voice data, which have been thus compressed, are transmitted to the second processing unit  64  via the internal bus  65  from the first processing unit  63 . The second processing unit  64  adds RTP to the coded voice data, thereby assembling a voice packet. This voice packet is transferred to the signal processing unit  53  of the control unit  50  via the DPRAM  62  and the internal bus  54  as well. 
   The signal processing unit  53  assembles a voice packet by adding a UDP (User Datagram Protocol) header and an IP (Internet Protocol) header to the former voice packet received from the CODEC  60 , and forwards this assembled voice packet to the LAN lines connected to the LANs  7 ,  8  via the LAN-IF  52 . FIG.  4 (A) shows a frame structure of the voice packet on the LAN line and the Internet line. 
   Further, the control data (Dch data) of the call control signal etc corresponding to a TTC Standard JT-Q.931 message, are inputted to the signal processing unit  53  via the HW-IF  51  of the control unit  50  and the internal bus from the highway switch  22  of the PBX  20 . 
   The signal processing unit  53  assembles a control data packet based on a frame structure shown in FIG.  4 (D) by adding a TCP (Transmission Control Protocol) header and an IP header to the received control data. This control data packet is forwarded to the LAN lines connected to the LANs  7 ,  8  via the LAN-IF  52 . 
   On the other hand, when the voice packet is inputted to the IP communication interface device  40  from the LAN line, the voice packet is deassembled and decoded into Bch voice data through processing steps opposite to those described above. The Bch voice data are then transmitted to the highway switch  22  of the PBX  20 . 
   Further, when the control data packet is inputted to the IP communication interface device  40  from the LAN line, the packet is deassembled through processing steps opposite to those explained above into Dch control data, and the Dch control data are transmitted to the highway switch  22  of the PBX  20 . Namely, the IP communication interface device  40  transparently transmits and receives the control data between the PBX  20  and the LANs  7 ,  8 . 
   [Second Example of Architectures and Operations of Private Branch Exchange and IP Communication Interface Device] 
   (Private Branch Exchange) 
   A second PBX  20  corresponding to the PBXs  1 ,  2  in IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 5 , includes a facsimile (FAX) terminal control unit  25 , the highway switch  22 , the trunk control unit  23  and the central control unit  24 . 
   The FAX terminal control unit  25  accommodates a facsimile (FAX) terminal (telephone)  32  incorporating a FAX communication function through a FAX line, and is connected to the highway switch  22 . The FAX terminal control unit  25  controls a transmission, a receipt and a disconnection with respect to the FAX terminal  32 . 
   The highway switch  22  is constructed of a time division multiplexing transmission path (Highway: HW) having [nB+D] (n=1˜31) channels, and has a capacity of, e.g., 2 Mbps (64 Kbps×32 time slots TS). The trunk control unit  23  accommodates the ISDN relay line of BRI or PRI that is connected to the public switched network. The trunk control unit  23  serves to transmit and receive FAX data (Bch data) of the B channel and control data (Dch data) of the D channel. Further, the trunk control unit  23  is connected directly to the highway switch  22 . 
   The central control unit  24  switches the lines by controlling the FAX terminal control unit  25 , the highway switch  22  and the trunk control unit  23 , respectively. Moreover, the central control unit  24  executes setting, canceling and outputting of station data via the maintenance/operation interface (unillustrated). 
   (IP Communication Interface Device) 
   Next, a second IP communication interface device  40  corresponding to the IP communication interface devices  5 ,  6  in the IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 5 , includes the control unit  50  and a CODEC  70 . The control unit  50  and the CODEC  70  are constructed of an individual or one piece of package card, and this package card is mounted as the IP interface device  40  into the same box as that of the PBX  20  described above. A layout of the control unit  50  and the CODECs  70 , which are mounted in the single package card, is the same as that shown in FIG.  3 . 
   The control unit  50  comprises the highway switch interface (HW-IF) 51 , the LAN interface (LAN-IF) 52 , the signal processing unit  53  provided in the CPU, and the internal bus  54 . The control unit  50  transmits and receives packets corresponding to media with the Internet line via the LAN line, which are FAX packets in this example. Further, the control unit  50  is connected to the highway switch  22  of the PBX  20  and to the LANs  7 ,  8 , and controls the CODECs  70  to assemble and deassemble the packets of data corresponding to the media, i.e., the FAX data in this example. 
   The HW-IF  51  connected directly to the highway of the highway switch  22  takes line data of 64 Kbps out of this highway (the transmission speed thereof is, e.g., 2 Mbps) and inserts the line data of 64 Kbps into the highway of the highway switch  22 . The LAN-IF  52  is connected to the LANs  7 ,  8  and controls the electric/physical interfaces of the LAN lines in the LAN topology, i.e., 10BASE-T or 100BASE-TX in this example. The signal processing unit  53  establishes calls between the connection type communications on the side of the switched circuit network of the PBX  20  and the connectionless type communications on the side of the Internet, and processes the end call control signal. 
   Further, the CODEC  70  connected to the control unit  50  is constructed of a dropper/inserter (TS-CNTL)  71 , a dual port memory (DPRAM)  72 , a first processing unit  73  composed of a digital signal processor (DSP) and having a coding/decoding function, a second processing unit  74  provided in the CPU and having a packet assembling/deassembling function, and an internal bus  75 . The CODEC  70  assembles and deassembles the packet of the data corresponding to the media, i.e., the FAX data in this example. 
   The TS-CONTL  71  takes the data out of a 64 Kbps time slot of an internal transmission path between the control unit  50  and the CODEC  70 , and inserts the data into the same time slot. The DPRAM  72  enables the signal processing unit  53  of the control unit  50  and the second processing unit  74  of the CODEC  70  to perform the internal communications therebetween. 
   The first processing unit  73  executes a process of coding continuous signals of the FAX data taken out of the time slot in the TS-CNTL  71  into discrete signals of the FAX packet to the Internet line. Further, the first processing unit  73  executes a process of decoding the FAX packet forwarded from the Internet line into the continuous signals of the FAX data, whereby the decoded signals can be inserted into the predetermined time slot in the TS-CNTL  71 . 
   The second processing unit  74  controls the first processing unit  73 , and executes the packet assembly including the addition of RTP for enabling the real time transport to be carried out and a packet deassembly including the elimination of RTP. Note that the CODECs  70  are extensible corresponding to an increase in the number of output channels to the LANs  7 ,  8  from the IP communication interface device  40 . 
   The second IP communication interface device  40  is connected directly to the highway of the highway switch  22  via the HW-IF  51 , and may therefore be treated as the [trunk device] embraced by the ISDN relay line as viewed from the PBX  20 . 
   Operation 
   In the second IP communication interface device  40  taking the architecture described above, the FAX data (Bch data) having a transmission speed of G3 are inputted via the HW-IF  51  of the control unit  50  to the TS-CNTL  71  of the CODEC  70  from the highway switch  22  of the PBX  20 . 
   The FAX data inputted to the TS-CNTL  71  are coded based on a FAX relay method of FRP.11 in the first processing unit  73  having automatically detected inter-FAX-terminal signals. The coded FAX data are transmitted to the second processing unit  74  via the internal bus  75  from the first processing unit  73 . The second processing unit  74  adds RTP to the coded FAX data, thereby assembling a FAX packet. This FAX packet is transferred to the signal processing unit  53  of the control unit  50  via the DPRAM  72  and the internal bus  54  as well. 
   The signal processing unit  53  assembles a FAX packet by adding a UDP header and an IP header to the former FAX packet received from the CODEC  70 , and forwards this assembled FAX packet to the LAN lines connected to the LANs  7 ,  8  via the LAN-IF  52 . FIG.  4 (B) shows a frame structure of the FAX packet on the LAN line and the Internet line. 
   On the other hand, when the FAX packet is inputted to the IP communication interface device  40  from the LAN line, the FAX packet is deassembled and decoded into Bch FAX data through processing steps opposite to those described above. The Bch FAX data are then transmitted to the highway switch  22  of the PBX  20 . 
   Note that the processes of transmitting and receiving the control data (Dch data) of the call control signal etc corresponding to the TTC Standard JT-Q.931 message in this IP communication interface device  40 , are the same as those in the first IP communication interface device  40  described above. 
   [Third Example of Architectures and Operations of Private Branch Exchange and IP Communication Interface Device] 
   (Private Branch Exchange) 
   A third PBX  20  corresponding to the PBXs  1 ,  2  in IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 6 , includes a data terminal control unit  26 , the highway switch  22 , the trunk control unit  23  and the central control unit  24 . 
   The data terminal control unit  26  accommodates a data terminal  33  incorporating a data communication function through a data line, and is connected to the highway switch  22 . The data terminal control unit  26  controls a transmission and a receipt with respect to the data terminal  33 . 
   The highway switch  22  is constructed of a time division multiplexing transmission path (Highway: HW) having [nB+D] (n=1˜31) channels, and has a capacity of, e.g., 2 Mbps (64 Kbps×32 time slots TS). The trunk control unit  23  accommodates the ISDN relay line of BRI or PRI that is connected to the public switched network. The trunk control unit  23  serves to transmit and receive 64 Kbps non-limited digital data (Bch data) of the B channel and control data (Dch data) of the D channel. Further, the trunk control unit  23  is connected directly to the highway switch  22 . 
   The central control unit  24  switches the lines by controlling the data terminal control unit  26 , the highway switch  22  and the trunk control unit  23 , respectively. Moreover, the central control unit  24  executes setting, canceling and outputting of station data via the maintenance/operation interface (unillustrated). 
   (IP Communication Interface Device) 
   Next, a third IP communication interface device  40  corresponding to the IP communication interface devices  5 ,  6  in the IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 6 , includes the control unit  50  and a CODEC  80 . The control unit  50  and the CODEC  80  are constructed of an individual or one piece of package card, and this package card is mounted as the IP interface device  40  into the same box as that of the PBX  20  described above. A layout of the control unit  50  and the CODECs  80 , which are mounted in the single package card, is the same as that shown in FIG.  3 . 
   The control unit  50  comprises a highway switch interface (HW-IF)  51 , a LAN interface (LAN-IF)  52 , a signal processing unit  53  provided in the CPU, and an internal bus  54 . The control unit  50  transmits and receives packets corresponding to media with the Internet line via the LAN line, which are data packets in this example. Further, the control unit  50  is connected to the highway switch  22  of the PBX  20  and to the LANs  7 ,  8 , and controls the CODECs  80  to assemble and deassemble the packets of data corresponding to the media in this example. 
   The HW-IF  51  connected directly to the highway of the highway switch  22  takes line data of 64 Kbps out of this highway (a transmission speed thereof is, e.g., 2 Mbps) and inserts the line data of 64 Kbps into the highway of the highway switch  22 . The LAN-IF  52  is connected to the LANs  7 ,  8  and controls the electric/physical interfaces of the LAN lines in the LAN topology, i.e., 10BASE-T or 100BASE-TX in this example. The signal processing unit  53  establishes calls between the connection type communications on the side of the switched circuit network of the PBX  20  and the connectionless type communications on the side of the Internet, and processes the end call control signal. 
   Further, the CODEC  80  connected to the control unit  50  is constructed of a dropper/inserter (TS-CNTL)  81 , a dual port memory (DPRAM)  82 , a first processing unit  83  composed of a digital signal processor (DSP) and having a coding/decoding function, a second processing unit  84  provided in the CPU and having a packet assembling/deassembling function, and an internal bus  85 . The CODEC  80  assembles and deassembles the packet of the data corresponding to the media in this example. 
   The TS-CONTL  81  takes the data out of a 64 Kbps time slot of an internal transmission path between the control unit  50  and the CODEC  80 , and inserts the data into the same time slot. The DPRAM  82  enables the signal processing unit  53  of the control unit  50  and the second processing unit  84 , which will be explained later on, of the CODEC  80  to perform the internal communications therebetween. 
   The first processing unit  83  executes a process of coding continuous signals of the data taken out of the time slot in the TS-CNTL  81  into discrete signals of the data packet to the Internet line. Further, the first processing unit  83  executes a process of decoding the data packet forwarded from the Internet line into the continuous signals of the data, whereby the decoded signals can be inserted into the predetermined time slot in the TS-CNTL  81 . Note that the first processing unit  83  neither compresses nor extends the data, and, instead, there may be taken a process of merely letting the data through. 
   The second processing unit  84  controls the first processing unit  83 , and assembles and deassembles the packets. Note that the CODECs  80  are extensible corresponding to an increase in the number of output channels to the LANs  7 ,  8  from the IP communication interface device  40 . 
   The third IP communication interface device  40  described above is connected directly to the highway of the highway switch  22  via the HW-IF  51 , and may therefore be treated as a [trunk device] embraced by the ISDN relay line as viewed from the PBX  20 . 
   (Operation) 
   In the third IP communication interface device  40  taking the architecture described above, the 64 Kbps non-limited digital data (Bch data) excluding the FAX data having the transmission speed of G3 are inputted via the HW-IF  51  of the control unit  50  to the TS-CNTL  81  of the CODEC  80  from the highway switch  22  of the PBX  20 . 
   The data inputted to the TS-CNTL  81  are coded in the first processing unit  83 . The coded data are transmitted to the second processing unit  84  via the internal bus  85  from the first processing unit  83 . The second processing unit  84 , based on the coded data, assembles a data packet. This data packet is transferred to the signal processing unit  53  of the control unit  50  via the DPRAM  82  and the internal bus  54  as well. 
   The signal processing unit  53  assembles a data packet by adding a TCP header and an IP header to the former data packet received from the CODEC  80 , and forwards this assembled data packet to the LAN lines connected to the LANs  7 ,  8  via the LAN-IF  52 . FIG.  4 (C) shows a frame structure of the data packet on the LAN line and the Internet line. 
   On the other hand, when the data packet is inputted to the IP communication interface device  40  from the LAN line, the data packet is deassembled and decoded into Bch data through processing steps opposite to those described above. The Bch data are then transmitted to the highway switch  22  of the PBX  20 . 
   Note that the processes of transmitting and receiving the control data (Dch data) of the call control signal etc corresponding to the TTC Standard JT-Q.931 message in this IP communication interface device  40 , are the same as those in the first IP communication interface device  40  described above. 
   [Fourth Example of Architectures and Operations of Private Branch Exchange and IP Communication Interface Device] 
   (Private Branch Exchange) 
   A fourth PBX  20  corresponding to the PBXs  1 ,  2  in IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 7 , includes the voice terminal (subscriber) control unit  21 , the facsimile (FAX) terminal control unit  25 , the highway switch  22 , the trunk control unit  23  and the central control unit  24 . 
   The voice terminal control unit  21  accommodates a voice terminal (telephone)  31  corresponding to the communication terminal devices  3 ,  4  and incorporating a voice communication function through a subscriber line, and is connected to the highway switch  22 . The voice terminal control unit  21  controls detection of calling, response and disconnection, controls a receipt of dialing and controls a calling signal with respect to the voice terminal  31 . The voice terminal control unit  21  also controls receiving operations when the voice terminal  31  is set on a receiving side. 
   The FAX terminal control unit  25  accommodates a facsimile (FAX) terminal  32  corresponding to the communication terminal devices  3 ,  4  and incorporating a FAX communication function through a FAX line, and is connected to the highway switch  22 . The FAX terminal control unit  25  controls a transmission, a receipt and a disconnection with respect to the FAX terminal  32 . 
   The data terminal control unit  26  accommodates a data terminal  33  such as a PC corresponding to the communication terminal devices  3 ,  4  and incorporating a data communication function through a data line, and is connected to the highway switch  22 . The data terminal control unit  26  controls a transmission and a receipt with respect to the data terminal  33 . 
   The highway switch  22  is constructed of a time division multiplexing transmission path (Highway: HW) having [nB+D] (n=1˜31) channels, and has a capacity of, e.g., 2 Mbps (64 Kbps×32 time slots TS). The trunk control unit  23  accommodates the ISDN relay line of BRI or PRI that is connected to the public switched network. The trunk control unit  23  serves to transmit and receive the voice data, the FAX data or the data (Bch data) of the B channel and control data (Dch data) of the D channel. Further, the trunk control unit  23  is connected directly to the highway switch  22 . 
   The central control unit  24  switches the lines by controlling the voice terminal control unit  21 , the FAX terminal control unit  25 , the data terminal control unit  26 , the highway switch  22  and the trunk control unit  23 , respectively. Moreover, the central control unit  24  executes setting, canceling and outputting of station data via the maintenance/operation interface (unillustrated). 
   (IP Communication Interface Device) 
   Next, a fourth IP communication interface device  40  corresponding to the IP communication interface devices  5 ,  6  in the IP communication network system shown in  FIG. 1 , as illustrated in  FIG. 7 , includes the control unit  50  and a CODEC  90 . The control unit  50  and the CODEC  90  are constructed of an individual or one piece of package card, and this package card is mounted as the IP interface device  40  into the same box as that of the PBX  20  described above. A layout of the control unit  50  and the CODECs  90 , which are mounted in the single package card, is the same as that shown in FIG.  3 . 
   The control unit  50  comprises the highway switch interface (HW-IF)  51 , the LAN interface (LAN-IF)  52 , the signal processing unit  53  provided in the CPU, and the internal bus  54 . The control unit  50  transmits and receives packets corresponding to media with the Internet line via the LAN line, which are the voice packets, the FAX packets or the data packets. Further, the control unit  50  is connected to the highway switch  22  of the PBX  20  and to the LANs  7 , 8 , and controls the CODECs  90  to assemble and deassemble the packets of data corresponding to the media. 
   The HW-IF  51  connected directly to the highway of the highway switch  22  takes line data of 64 Kbps out of this highway (the transmission speed thereof is, e.g., 2 Mbps) and inserts the line data of 64 Kbps into the highway of the highway switch  22 . The LAN-IF  52  is connected to the LANs  7 ,  8  and controls the electric/physical interfaces of the LAN lines in the LAN topology, i.e., 10BASE-T or 100BASE-TX in this example. The signal processing unit  53  establishes calls between the connection type communications on the side of the switched circuit network of the PBX  20  and the connectionless type communications on the side of the Internet, and processes the end call control signal. 
   Further, the CODEC  90  connected to the control unit  50  is constructed of a dropper/inserter (TS-CNTL)  91 , a dual port memory (DPRAM)  92 , a first voice processing unit  931 , a first FAX processing unit  932  and a first data processing unit  933  each composed of a digital signal processor (DSP) and having a coding/decoding function, a second voice processing unit  941 , a second FAX processing unit  942  and a second data processing unit  943  each provided in the CPU and having a packet assembling/deassembling function, an internal bus  95  and a selector  96 . The CODEC  90  assembles and deassembles the packet of the data corresponding to the media. 
   The TS-CONTL  91  takes the data out of a 64 Kbps time slot of an internal transmission path between the control unit  50  and the CODEC  90 , and inserts the data into the same time slot. The DPRAM  92  enables the signal processing unit  53  of the control unit  50  and the second processing units  941 ,  942 ,  943  of the CODEC  90  to perform the internal communications therebetween. 
   The first voice processing unit  931  executes a process of coding continuous signals of the voice data taken out of the time slot in the TS-CNTL  91  into discrete signals of the voice packet to the Internet line. Further, the first voice processing unit  931  executes a process of decoding the voice packet forwarded from the Internet line into the continuous signals of the voice data, whereby the decoded signals can be inserted into the predetermined time slot in the TS-CNTL  91 . 
   The first FAX processing unit  932  executes a process of coding continuous signals of the FAX data taken out of the time slot in the TS-CNTL  91  into discrete signals of the FAX packet to the Internet line. Further, the first FAX processing unit  932  executes a process of decoding the FAX packet forwarded from the Internet line into the continuous signals of the FAX data, whereby the decoded signals can be inserted into the predetermined time slot in the TS-CNTL  91 . 
   The first data processing unit  933  executes a process of coding continuous signals of the data taken out of the time slot in the TS-CNTL  91  into discrete signals of the data packet to the Internet line. Further, the first data processing unit  933  executes a process of decoding the data packet forwarded from the Internet line into the continuous signals of the data, whereby the decoded signals can be inserted into the predetermined time slot in the TS-CNTL  91 . Note that the first data processing unit  933  neither encodes nor decodes the data, and, instead, there may be taken a process of merely letting the data through. 
   The second voice processing unit  941  and the second FAX processing unit  942  control the first voice processing unit  93   a  and the first FAX processing unit  932  corresponding thereto, and executes the packet assembly including the addition of RTP for enabling the real time transport to be carried out and a packet deassembly including the elimination of RTP. 
   The second data processing unit  943  controls the first data processing unit  933 , and executes the packet assembly and the packet deassembly. 
   The selector  96  receives a switching signal from the signal processing unit  53 , and selects the first voice processing unit  931  or the first FAX processing unit  932  or the first data processing unit  933  in accordance with a content of this switching signal, i.e., the media specified. Note that the CODECs  90  are extensible corresponding to an increase in the number of output channels to the LANs  7 ,  8  from the IP communication interface device  40 . 
   The fourth IP communication interface device  40  is connected directly to the highway of the highway switch  22  via the HW-IF  51 , and may therefore be treated as the [trunk device] embraced by the ISDN relay line as viewed from the PBX  20 . 
   (Operation) 
   In the fourth IP communication interface device  40  taking the architecture described above, the voice data, the FAX data having the transmission speed of G3, or the 64 Kbps non-limited digital data are inputted as the Bch data via the HW-IF  51  of the control unit  50  to the TS-CNTL  91  of the CODEC  90  from the highway switch  22  of the PBX  20 . 
   The signal processing unit  53  of the control unit  50  distinguishes between items of media data corresponding to the voice data, the FAX data and the data inputted from the highway switch  22  of the PBX  20  via the HW-IF  51 , and transmits a switching signal to the selector  96 . 
   The selector  96  receives the switching signal from the signal processing unit  53 , and selects the first voice processing unit  931 , or the first FAX processing unit  932  or the first data processing unit  933  in accordance with a content of this switching signal, i.e., the media specified. 
   To describe it in greater details, the signal processing unit  53  of the control unit  50 , when detecting a Dch signal in which a transmission capability data element as the media data is non-limited digital, transmits the switching signal to the selector  96  via the HW-IF  51  and TS-CNTL  91 . The selector  96  receiving the switching signal from the signal processing unit  53 , selects the first data processing unit  933  in accordance with the media specified. Further, the signal processing unit  53  of the control unit  50 , when detecting a Dch signal in which the transmission capability data element as the media data is not non-limited digital, transmits the switching signal to the selector  96  on the same route. Then, the selector  96  selects the first voice processing unit  931 . This process is the same irrespective of whether the IP communication interface device  40  is set on the transmitting side or on the receiving side. 
   The signal processing unit  53 , when detecting a NSF (Non Standard Facilities) or DIS (Digital Identification Signal) given from the FAX terminal  32  accommodated in the PBX  20 , identifies that the terminal is the FAX terminal  32  on the receiving side, and transmits the switching signal to the selector  96  on the same route as the above. Then, the selector  96  selects the first FAX processing unit  932 . At this time, the signal processing unit  53  transmits a [switching] Dch signal to the transmission-sided IP communication interface device  40  on the opposite side via the LAN line. 
   Further, the signal processing unit  53 , when detecting a normal end of the FAX procedure or a time-out of the switchover to FAX or a DCN (Disconnect) signal, transmits the switching signal to the selector  96 . Then, the selector  96  selects the first voice processing unit  931  from the first FAX processing unit  932 . Subsequently, the signal processing unit  53  transmits the [switching] Dch signal to the transmission-sided IP communication interface device  40  on the opposite side via the LAN line. 
   The signal processing unit  53 , when receiving the [switching] Dch signal transmitted from the IP communication interface device  40  on the opposite side, transmits the switching signal to the selector  96 , whereby the selector  96  selects the first FAX processing unit  932 . 
   The voice data inputted to the TS-CNTL  91  are coded in the first voice processing unit  931  through the selector  96  and subjected to the voice compression and the silence compression based on the ITU-T G.729 Annex A/B. The coded voice data, which have been thus compressed, are transmitted to the second processing unit  941  via the internal bus  95  from the first voice processing unit  931 . The second voice processing unit  6941  adds RTP to the coded voice data, thereby assembling a voice packet. This voice packet is transferred to the signal processing unit  53  of the control unit  50  via the DPRAM  92  and the internal bus  54  as well. 
   The signal processing unit  53  assembles the voice packet by adding a UDP header and an IP header to the former voice packet received from the CODEC  90 , and forwards this assembled voice packet to the LAN lines connected to the LANs  7 ,  8  via the LAN-IF  52 . The frame structure of the voice packet on the LAN line and the Internet line is as shown in FIG.  4 (A). 
   On the other hand, when the voice packet is inputted to the IP communication interface device  40  from the LAN line, the voice packet is deassembled and decoded into Bch voice data through processing steps opposite to those described above. The Bch voice data are then transmitted to the highway switch  22  of the PBX  20 . 
   The FAX data inputted to the TS-CNTL  91  are coded based on the FAX relay method of FRP.11 in the first FAX processing unit  932  having automatically detected inter-FAX-terminal signals through the selector  96 . The coded FAX data are transmitted to the second FAX processing unit  942  via the internal bus  95  from the first FAX processing unit  932 . The second FAX processing unit  942  adds RTP to the coded FAX data, thereby assembling a FAX packet. This FAX packet is transferred to the signal processing unit  53  of the control unit  50  via the DPRAM  92  and the internal bus  54  as well. 
   The signal processing unit  53  assembles a FAX packet by adding a UDP header and an IP header to the former FAX packet received from the CODEC  90 , and forwards this assembled FAX packet to the LAN lines connected to the LANs  7 ,  8  via the LAN-IF  52 . The frame structure of the FAX packet on the LAN line and the Internet line is as shown in FIG.  4 (B). 
   On the other hand, when the FAX packet is inputted to the IP communication interface device  40  from the LAN line, the FAX packet is deassembled and decoded into Bch FAX data through processing steps opposite to those described above. The Bch FAX data are then transmitted to the highway switch  22  of the PBX  20 . 
   The data inputted to the TS-CNTL  91  are coded as the necessity may arise in the first data processing unit  933  through the selector  96 . The coded data are transmitted to the second data processing unit  943  via the internal bus  95  from the first data processing unit  933 . The second data processing unit  943  assembles a data packet on the basis of the coded data. This data packet is transferred to the signal processing unit  53  of the control unit  50  via the DPRAM  92  and the internal bus  54  as well. 
   The signal processing unit  53  assembles a data packet by adding a TCP header and an IP header to the former data packet received from the CODEC  90 , and forwards this assembled data packet to the LAN lines connected to the LANs  7 ,  8  via the LAN-IF  52 . The frame structure of the data packet on the LAN line and the Internet line is as shown in FIG.  4 (C). 
   On the other hand, when the data packet is inputted to the IP communication interface device  40  from the LAN line, the data packet is deassembled and decoded into Bch data through processing steps opposite to those described above. The Bch data are then transmitted to the highway switch  22  of the PBX  20 . 
   Note that the process of transmitting and receiving the control data (Dch data) of the call control signals which correspond to the TTC Standard JT-Q.931 message in this IP communication interface device  40 , is the same as that in the first IP communication interface device  40  described above. 
   The function of the fourth IP communication interface device  40  explained above will be described more specifically. The function that will hereinafter be explained is the same as that of each of the first, second and third IP communication interface devices  40 . 
   The signal processing unit  53  of the control unit  50  extracts a forwarding target number, i.e., an office number and an extension number out of received number data elements of the call control signals (Q.931 message) serving as the Dch control data from the PBX  20 , then determines an IP address of a destination (addressee) of the connection on the basis of the office number, and executes address mapping. Subsequently, the signal processing unit  53  sets the determined IP address in the IP header, and transmits the voice packet or the FAX packet or the data packet to the LAN line via the LAN-IF  52 . On the other hand, the signal processing unit  53  of the control unit  50 , when receiving the voice packet or the FAX packet or the data packet from the LAN line via the LAN-IF  5 , extracts only the received number data elements of the call control signal, viz., executes a receiving process without performing the address mapping unlike the transmitting process. 
   Further, with respect to the Internet  11  in which the routers  9 ,  10  capable of controlling the priority of the voice packets are disposed, the signal processing unit  53  of the control unit  50 , indicates the routers  9 ,  10  to set the priority by use of TOS (Type of Service) fields of the IP headers, and restrains a delay of forwarding the voice packets. 
   The second voice processing unit  943  of the CODEC  90  rearranges a sequence of regeneration within a range of the accumulated voice packet data. Namely, the second voice processing unit  943 , if a transmission sequence of the voice data arrived is smaller than a transmission sequence of the accumulated voice packet data, regenerates the voice data by decoding in the smaller transmission sequence. 
   A PB (Push Button) signal received in in-channel band from the PBX  20  is temporarily received and encoded in the CODEC  90 , and the signal processing unit  53  of the control unit  50  converts it into a call control signal (Q.931 message) and transmits the call control signal to the LAN line. When the PB signals are inputted in the form of control data from the LAN line via the Internet line, the control unit  50  indicates the first voice processing unit  931  of the CODEC  90  to convert these signals into analog PB signals. The decoded PB signals are transmitted to the PBX  20  via the TS-CNTL  91  and the HW-IF  51  from the first voice processing unit  931 . 
   Software of the CPU of the control unit  50  provided with the signal processing unit  53  and software of the CPU of the CODEC  90  provided with the second processing units  941 ,  942 ,  943 , can be downloaded from outside via LAN ports based on TCP/IP (10BASE-T or 100BASE-TX). 
   Further, it is feasible to obtain statistic data, fault data and traced at a from outside via the LAN ports based on TCP/IP (10BASE-T or 100BASE-TX). Namely, in the IP communication interface device  40 , various items of statistic data such as the number of transmitted/received packets and a line activity ratio are collected and accumulated in order to grasp an operation state and actualize an effective utilization of the line. Further, the data about faults occurred during the operation are collected and accumulated as a log. The Dch data of the call control signals are collected and accumulated as the trace data for monitoring the transmitted/received data. 
   Although only a few embodiments of the present invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the preferred embodiments without departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined by the following claims.