Abstract:
To implement a key telephone system through an IP (Internet protocol) network, if real-time broadcast information is transmitted by multicast communications, restriction to prevent a rapid increase in network traffic is received, an additional special protocol is required, and it is hard to ensure the confidentiality of information. If real-time broadcast information is transmitted by unicast communications, transmission processing is centralized on a broadcast information transmission apparatus, the traffic becomes enormous, and a broad communication band and a high processing capability become necessary. Therefore, a transmission dedicated apparatus is provided between a broadcast information transmission apparatus and a terminal for distributing the transmission function and traffic. The broadcast information transmission apparatus needs only to manage the transmission dedicated apparatus. A plurality of terminals, etc., can be connected to the transmission dedicated apparatus. Further, a transmission dedicated apparatus can also be connected as a subordinate node to the transmission dedicated apparatus.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a traffic distribution method and a traffic distribution system of an IP key telephone which implement a key telephone system through an IP (Internet protocol) network.  
         [0003]     2. Description of the Related Art  
         [0004]      FIG. 11  is a block diagram to show the configuration of a multicast communication system disclosed in JP-A-2003-32300. This system implements a multicast data communication system having advanced security for preventing a problem of generating a large number of meaningless tables in network nodes by attack of a malicious user or the like.  
         [0005]     In the multicast data communication system, each of reception hosts  222 - 1  to  222 - 4  sends a reception request packet to a transmission host  200  at regular time intervals. A relay node  221  receiving the reception request packet and then receiving a transmission table generation packet and a data packet from the transmission host  200  prepares a transmission table to the transmission host  200  if the transmission table does not exist, and then registers the addresses of the reception hosts  222 - 1  to  222 - 4  and the arrival times of the reception request packets and sends a reception request packet to the transmission host  200  at regular time intervals. The relay node  221  receiving a data packet from the transmission host  200  copies and transmits the data packet only to the reception host corresponding to the arrival time of the reception request packet registered in the transmission table being within a given time from the arrival time of the data packet.  
         [0006]     Generally, in the case of transmitting broadcast information in real time from a broadcast information transmission apparatus through the IP network to a key telephone system, the following problems are encountered. For example, in order to execute multicast communications disclosed in JP-A-2003-32300, it becomes necessary to add protocols such as DVMRP (Distance-Vector Multicast Routing Protocol) of protocol RFC 1075 for constructing a multicast tree and IGMP (Internet Group Management Protocol) of protocol RFC 1112 (paragraph [0003] in JP-A-2003-32300). Then, a communication network containing components such as routers connected through the IP network must be managed, namely, a communication network management problem (problem 1) is involved. The IGMP is a protocol to control a host group formed for receiving transmission in IP multicast for efficiently transmitting the same data to a plurality of hosts. The protocol is used to transfer information concerning the group between multicast routers, such as participating or withdrawing one host in or from the group.  
         [0007]     The communication network management problem (problem 1) in the multicast communications will be further discussed. If multicast transmission is conducted, communication protocol restriction on the network is received. That is, in the general IP network, a multicast packet cannot be through a router and thus it also becomes necessary to change the setting of the router to execute the multicast communications. However, if the setting is changed, a multicast packet flies around to each network separated by the router and the traffic is increased rapidly. Thus, usually the network manager does not permit such router setting change and therefore restriction on execution of the multicast communications (namely, communication cannot be conducted through the router) occurs.  
         [0008]     If the network manager permits transmission from a specific multicast transmission source and approves router setting change, it becomes necessary to change the settings of all routers involved in relay. Since the IP network is constructed intricately like meshes, it is extremely difficult to always manage the setting of each router with no mistakes. If the setting management is erroneous, the possibility of occurrence of a leak of secret information to a network outside the transmission range is large and load on the management is large. If a multicast packet is transmitted via a router outside management of ISP (Internet service provider), setting change is made impossible.  
         [0009]     In the IP network of the backbone network, generally a precaution against a sudden increase in traffic caused by a rapid increase in communication amount is taken to ensure stable communications. Thus, there is a problem of a sudden increase in traffic (problem 2), namely, multicast communications of simultaneously sending the same communication contents from one communication party (broadcast information transmission apparatus) to a plurality of communication parties (key telephone systems) are hard to use in the IP network because of involving a sudden increase in traffic of the IP network spread like meshes.  
         [0010]     Further, since the same information is simultaneously sent (broadcast) to a plurality of communication parties (key telephone systems) in the multicast communications, the possibility that the communication contents will also be leaked to third parties (personal computer, router, server, framework, etc.,) connected to the IP network other than concerned parties in the multicast communications is large and confidentiality is hard to hold, namely, a secret information leak problem (problem 3) is involved.  
         [0011]     Further, in the multicast communications, essentially the information flow from a superior node (for example, broadcast information transmission apparatus) to subordinate nodes (for example, terminals) is managed and thus it is difficult to deal with different requests for broadcast information, made by a large number of subordinate nodes in detail and there is an information flow problem (problem 4) of being hard to send information to the superior node.  
         [0012]     In contrast to the multicast communications of simultaneously broadcasting the same communication contents from one communication party (broadcast information transmission apparatus) to a plurality of communication parties (key telephone systems), unicast communications of separately sending the same communication contents (broadcast information) from one communication party (broadcast information transmission apparatus) to other communication parties (key telephone systems) are available. There is also a large problem in the unicast communications.  
         [0013]     When broadcast information is transmitted in the unicast communications, one broadcast information transmission apparatus transmits the broadcast information to a large number of destinations (key telephone systems) at the same time and thus there is a transmission processing centralization problem (problem 5), namely, the transmission processing is centralized on the broadcast information transmission apparatus of the superior node and load on the broadcast information transmission apparatus becomes large. Further, since the broadcast information is transmitted to a large number of destinations (key telephone systems) at the same time, the traffic also becomes enormous in the IP network and there is a traffic amount increase problem (problem 6) of receiving traffic amount restriction. Also, there is a broadband and high transmission processing capability problem (problem 7), namely, transmission processing cannot be accomplished unless a broadcast information transmission apparatus having a sufficiently broad communication band and a high transmission processing capability is used.  
         [0014]     JP-A-2003-32300 is referred to as a related art.  
         [0015]     As mentioned above, the multicast communications disclosed in JP-A-2003-32300 has the communication network management problem (problem 1), the problem of a sudden increase in traffic (problem 2), the secret information leak problem (problem 3), the information flow problem (problem 4). The unicast communications has the transmission processing centralization problem (problem 5), the traffic amount increase problem (problem 6), and the broadband and high transmission processing capability problem (problem 7).  
       SUMMARY OF THE INVENTION  
       [0016]     An object of the invention is to solve the problems described above. Basically, while the features of the unicast communications not involving the problems of the multicast communications are utilized, the problems of the unicast communications (problems 5, 6, and 7) are solved and the broadband and high transmission processing capability problem is also solved by circumventing transmission processing centralization and traffic amount increase by distributing transmission processing.  
         [0017]     In A traffic distribution system according to the invention, a transmission dedicated apparatus is provided between a broadcast information transmission apparatus and a destination (key telephone system). The destination information data concerning the area that the transmission dedicated apparatus takes charge of is stored in the transmission dedicated apparatus, the data is accessed, a transmission function to the destination is provided, a node management function for connection to the broadcast information transmission apparatus in a superior node and connection to the area to which the destination in a subordinate node (for example, key telephone system) belongs is provided, and a LAN interface for transferring information (message) transferred between the broadcast information transmission apparatus and the destination (key telephone system) and connection to an IP network is provided.  
         [0018]     Accordingly, the need for the broadcast information transmission apparatus to be involved in details of destinations is eliminated. Information exchange between the broadcast information transmission apparatus and the transmission dedicated apparatus is placed only in the extremely limited range and the transmission dedicated apparatus takes charge of information exchange with each destination. Accordingly, the load on the broadcast information transmission apparatus is distributed to the transmission dedicated apparatus and is decreased, leading to solution to the above-described problems.  
         [0019]     According to the traffic distribution method and system of an IP key telephone of the invention, the transmission dedicated apparatus is provided between the broadcast information transmission apparatus and a destination (key telephone system), so that it is made possible to distribute the function by the transmission dedicated apparatus. Since the invention is embodied based on the unicast communications not involving the problems of the multicast communications, the above-described problems of the multicast communications (problems 1, 2, 3, and 4) are not involved. Moreover, to eliminate the drawbacks of the unicast communications, namely, the transmission processing centralization problem in the superior node (problem 5), the traffic amount increase problem (problem 6), and the broadband and high transmission processing capability problem (problem 7), transmission processing is distributed to a subordinate node, transmission processing centralization and traffic amount increase are circumvented, and the broadband and high transmission processing capability problem is also solved. Accordingly, the IP key telephone system connected through the IP network is made possible. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a block diagram to show a traffic distribution method and system of an IP key telephone according to a first embodiment of the invention;  
         [0021]      FIGS. 2A and 2B  are drawings of subordinate node information stored in a broadcast information transmission apparatus and a transmission dedicated apparatus of components in  FIG. 1 ;  
         [0022]      FIG. 3  is a block diagram to show the internal configuration of the transmission dedicated apparatus of the main part of the invention, one component in  FIG. 1 ;  
         [0023]      FIG. 4  is a block diagram to show a traffic distribution method and system of an IP key telephone according to a second embodiment of the invention;  
         [0024]      FIGS. 5A, 5B  and  5 C are drawings of subordinate node information stored in a broadcast information transmission apparatus and a transmission dedicated apparatus of components in  FIG. 4 ;  
         [0025]      FIG. 6  is a network block diagram to show a traffic distribution method and system of an IP key telephone according to a third embodiment of the invention;  
         [0026]      FIG. 7  is a setting description drawing of superior agent, stored in transmission dedicated apparatus R 1  and R 2  and terminals K 1 A, K 1 B, K 2 A, and K 2 B in  FIG. 6 ;  
         [0027]      FIG. 8  is a sequence diagram of registration message processing in the network configuration in  FIG. 6 ;  
         [0028]      FIGS. 9A, 9B  and  9 C are registration description drawings of subordinate node destination information data stored in broadcast information transmission apparatus Si and the transmission dedicated apparatus R 1  and R 2  in  FIG. 6 ;  
         [0029]      FIG. 10  is a sequence diagram of transmission message processing to provide information notification in the network configuration in  FIG. 6 ; and  
         [0030]      FIG. 11  is a block diagram to show the configuration of a network in a related art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     On the basis of taking the advantages of unicast communications, a transmission dedicated apparatus is provided between a broadcast information transmission apparatus and a terminal of a destination (key telephone system) for distributing the function. That is, unicast communications are conducted between the broadcast information transmission apparatus and the transmission dedicated apparatus, between the transmission dedicated apparatus and another transmission dedicated apparatus of a subordinate node, and between the transmission dedicated apparatus and the terminal.  
         [0032]     In the description that follows, SIP (session initiation protocol, communication control protocol used with IP telephone, etc., RFC 3261, RFC 3265) of IP (Internet protocol) proposed by IETF (Internet Engineering Task Force) is used. RFC 3261 is a basic protocol of SIP and RFC 3265 is a protocol defining details of registration (SUBSCRIBE) and information notification (NOTIFY).  
       First Embodiment  
       [0033]      FIG. 1  is a block diagram of a first embodiment of the invention to show the basic configuration of the invention. A broadcast information transmission apparatus S 1 , a transmission dedicated apparatus R 1 , and a terminal K 1  are provided, and broadcast information is transmitted by means of unicast communications. The transmission dedicated apparatus R 1  has the effect of distributing and decreasing load on the broadcast information transmission apparatus S 1  in the superior node on which traffic is centralized. Subordinate node registration messages IK 1 R 1   a  and IR 1 S 1   a , subordinate node registration acknowledge messages IS 1 R 1   a  and IR 1 K 1   a , information notification messages IS 1 R 1   b  and IR 1 K 1   b , and information notification acknowledge messages IK 1 R 1   b  and IR 1 S 1   b  are transmitted between these apparatuses (S 1 , R 1 , K 1 ).  
         [0034]     The subordinate node registration message is information to register (subscribe) an apparatus in a subordinate node in an apparatus in a superior node. The subordinate node registration acknowledge message is information (Acknowledge Subscription: Receipt for subscription) issued from the apparatus in the superior node acknowledging that subordinate node registration is complete to the apparatus in the subordinate node. The information notification message (notify) is provided for sending broadcast transmission information (broadcast contents) from the apparatus in the superior node to the apparatus in the subordinate node. The information notification acknowledge message is sent from the apparatus in the subordinate node to the apparatus in the superior node to inform the apparatus in the superior node that the broadcast transmission information has been received (Acknowledge Notification: Receipt for notify).  
         [0035]     The operation in  FIG. 1  is as follows. Upon reception of a subordinate node registration message IK 1 R 1   a  for requesting broadcast transmission from the terminal K 1  in the subordinate node connected to the node of the transmission dedicated apparatus R 1 , the transmission dedicated apparatus R 1  sends a subordinate node registration message IR 1 S 1   a  for requesting broadcast transmission to the broadcast information transmission apparatus S 1  in the superior node. Upon reception of the message, the broadcast information transmission apparatus S 1  registers (subscribes) the transmission dedicated apparatus R 1  and prepares for the information to be transmitted. Then, the broadcast information transmission apparatus S 1  sends a subordinate node registration acknowledge message IS 1 R 1   a  to the transmission dedicated apparatus R 1  as a receipt, informing the transmission dedicated apparatus R 1  that the registration is complete. The transmission dedicated apparatus R 1  prepares for the information to be transmitted. Then, the transmission dedicated apparatus R 1  sends a subordinate node registration acknowledge message IR 1 K 1   a  to the terminal K 1 , informing the terminal K 1  that the registration is complete.  
         [0036]     After completion of the registration, the broadcast information transmission apparatus S 1  transmits specified broadcast information to the transmission dedicated apparatus R 1  with an information notification message IS 1 R 1   b  at regular time intervals. The transmission dedicated apparatus R 1  stores the broadcast information transmitted with the information notification message IS 1 R 1   b  and at the same time, sends an information notification acknowledge message IR 1 S 1   b  to the broadcast information transmission apparatus S 1 , informing the broadcast information transmission apparatus S 1  that the information notification message IS 1 R 1   b  has been received. The transmission dedicated apparatus R 1  transmits the stored broadcast information to the terminal K 1  with an information notification message IR 1 K 1   b  at regular time intervals. Upon reception of the broadcast information, the terminal K 1  sends an information notification acknowledge message IK 1 R 1   b  to the transmission dedicated apparatus R 1 , informing the transmission dedicated apparatus R 1  that the information notification message IR 1 K 1   b  has been received.  
         [0037]     As the operation is performed as described above, unicast communications are conducted for transmission between the broadcast information transmission apparatus Si and the transmission dedicated apparatus R 1  and the transmission dedicated apparatus R 1  transmits the stored broadcast information to the terminal K 1  with the information notification message IR 1 K 1   b  at regular time intervals, so that the traffic and transmission processing centralized on the superior node (broadcast information transmission apparatus S 1 ) in the related art can be distributed to the subordinate node (transmission dedicated apparatus R 1 ).  
         [0038]      FIGS. 2A and 2B  are destination information drawings to represent an example of subordinate node information stored as destination information in the broadcast information transmission apparatus S 1  and the transmission dedicated apparatus R 1  of the components in  FIG. 1 . In  FIGS. 2A and 2B , the identifiers of the destinations (R 1  and K 1 ) for determining destinations, the node types (R and K) representing the types of apparatus at destinations, the validity term (for example, the number of days) to register the transmission information, the dialog mode (Dig 1 , Dig 2 ), and transmission request pattern representing pattern of transmitted broadcast information (PG 1 ) are stored.  
         [0039]      FIG. 3  shows the internal configuration of the transmission dedicated apparatus R of the main part of the invention. The transmission dedicated apparatus R includes a destination information data section  21 , a data access processing section  22 , a transmission function section  23 , a node management function section  24 , a message transmission and reception section  25 , and a LAN interface section  28 .  
         [0040]     The destination information data section  21  has a function of recording information concerning a subordinate node and a transmission request pattern indicating what broadcast information is requested by the subordinate node ( FIGS. 2A and 2B ) . The data access processing section  22  has a function of executing data registration, deletion, update, search, or reference in a unified way. The transmission function section  23  has a function of instructing the message transmission and reception section  25  to execute message transmission of broadcast information to subordinate node based on the destination information data. The node management function section  24  has a function of analyzing a message received by the message transmission and reception section  25 , adding, deleting, or updating a superior or subordinate node, and instructing the message transmission and reception section  25  to transmit a response message indicating that registration has been executed.  
         [0041]     The message transmission and reception section  25  has a function of receiving a message through the LAN interface section  28 , analyzing the message according to the protocol, passing the processing result to the node management function section  24 , and transmitting a message according to the protocol based on transmission processing information received from the transmission function section  23 . The LAN interface section  28  is connected to other nodes (the broadcast information transmission apparatus S 1  and the terminal K 1 ) through the IP network by an information transmission line  39  and has a function of interfacing with the message transmission and reception section  25 .  
         [0042]     A destination information input/output signal  31  is transmitted between the destination information data section  21  and the data access processing section  22 . A destination search and reference signal  32  is transmitted between the data access processing section  22  and the transmission function section  23 . An information control signal  33  is transmitted between the data access processing section  22  and the node management function section  24 . A transmission instruction signal  34  is transmitted between the transmission function section  23  and the message transmission and reception section  25 . A broadcast information signal  35  is transmitted between the node management function section  24  and the message transmission and reception section  25 . A transmission-reception signal  38  is transmitted between the message transmission and reception section  25  and the LAN interface section  28 . The LAN interface section  28  is connected to other nodes (the broadcast information transmission apparatus S 1 , subordinate transmission dedicated apparatus R 2 , and the terminal K 1 ) through the IP network by the information transmission line  39 .  
         [0043]     The destination information input/output signal  31  is a signal for executing registration, deletion, update, search, or reference input/output of the destination information data shown in  FIGS. 2A and 2B . The destination search and reference signal  32  is a signal for searching for or referencing the broadcast information transmission destination. The information control signal  33  is a signal for controlling registration, deletion, and update of destination information or transmission information. The transmission instruction signal  34  is a signal for instructing the message transmission and reception section  25  to transmit the broadcast information specified by the transmission function section  23 .  
         [0044]     The broadcast information signal  35  is a signal for transferring the broadcast information received by the message transmission and reception section  25  through the IP network from the broadcast information transmission apparatus S 1  to the node management function section  24 . The transmission-reception signal  38  is a signal for transmitting and receiving information through the LAN interface section  28 . The information transmission line  39  connects the transmission dedicated apparatus R to other nodes (the broadcast information transmission apparatus S 1 , subordinate transmission dedicated apparatus R 2 , and the terminal K 1 ) through the IP network.  
       Second embodiment  
       [0045]      FIG. 4  is a block diagram to show a second embodiment of the invention. Components identical with or similar to those previously described with reference to  FIG. 1  are denoted by the same reference numerals in  FIG. 4 . A broadcast information transmission apparatus S 1 , a transmission dedicated apparatus R 1 , and a terminal K 1  are provided. A transmission dedicated apparatus R 2  is connected to the transmission dedicated apparatus R 1 , and a terminal K 2  is connected to the transmission dedicated apparatus R 2 . The configuration in  FIG. 4  differs from the configuration in  FIG. 1  in that the transmission dedicated apparatus R 2  takes charge of transmission to the terminal K 2  for decreasing load on the transmission dedicated apparatus R 1 . That is, the transmission dedicated apparatus R 1  has the effect of decreasing load on the broadcast information transmission apparatus S 1  in the superior node, and the transmission dedicated apparatus R 2  has the effect of decreasing load on the transmission dedicated apparatus R 1  in the superior node.  
         [0046]     Subordinate node registration messages IK 1 R 1   a , IR 1 S 1   a , IK 2 R 2   a , and IR 2 R 1   a , subordinate node registration acknowledge messages IS 1 R 1   a , IR 1 K 1   a , IR 1 R 2   a , and IR 2 K 2   a , information notification messages IS 1 R 1   b , IR 1 K 1   b , IR 1 R 2   b , and IR 2 K 2   b , and information notification acknowledge messages IK 1 R 1   b , IR 1 S 1   b , IK 2 R 2   b , and IR 2 R 1   b  are transmitted between these apparatuses (S 1 , R 1 , K 1 , R 2 , K 2 ).  
         [0047]      FIGS. 5A, 5B  and  5 C show subordinate node information stored as destination information in the broadcast information transmission apparatus S 1  and the transmission dedicated apparatus R 1  and R 2  of the components in  FIG. 4 . The registration description in the broadcast information transmission apparatus S 1  shown in  FIG. 5A , the identifiers of the transmission dedicated apparatus R 1  and R 2  are registered under the destination identifier. The apparatus types of transmission dedicated apparatus R 1  and R 2  are registered under the node type. How many days the registration is valid in the transmission dedicated apparatus R 1  and R 2  is registered under the registration validity term. The dialog modes used for the transmission dedicated apparatus R 1  and R 2  are registered under the dialog. The transmission request patterns showing the types of broadcast information to be transmitted to the transmission dedicated apparatus R 1  and R 2  are registered under the transmission request pattern. The registration description in each of the transmission dedicated apparatus R 1  and R 2  shown in  FIGS. 5B and 5C  is similar to the registration description in the broadcast information transmission apparatus S 1  shown in FIG. SA.  
       Third Embodiment  
       [0048]      FIG. 6  is a network block diagram to show a traffic distribution method and system of an IP key telephone according to a third embodiment of the invention. An SIP proxy server P, a broadcast information transmission apparatus S 1 , and transmission dedicated apparatus R 1  and R 2  are provided, and transmission target ranges DS 1 , DS 1 B, DR 1 , DR 1 B, DR 2 , and DR 2 B are shown. The SIP proxy server P receives an SIP request from a terminal K or another SIP proxy server and transfers the SIP request to the broadcast information transmission apparatus S 1  or acts as proxy of the broadcast information transmission apparatus S 1 . The broadcast information transmission apparatus S 1  transmits information to the transmission dedicated apparatus R 1  contained in the transmission target range DS 1 . The transmission dedicated apparatus R 1  transmits information to two terminals K 1 A and K 1 B contained in the transmission target ranges DR 1  and the transmission dedicated apparatus R 2  connected through a router RU for relay. The transmission dedicated apparatus R 2  transmits information to two terminals K 2 A and K 2 B contained in the transmission target ranges DR 2 . The functions of the components are the same as those previously described with reference to  FIG. 4 .  
         [0049]     Use of the two transmission dedicated apparatus R 1  and R 2  makes it possible to decrease load on the transmission dedicated apparatus R 1  and distribute the processing capability of the transmission dedicated apparatus R 1 . To furthermore decrease the load and distribute the processing capability, it is also possible to provide a transmission dedicated apparatus R 3  (not shown) in a subordinate node to the transmission dedicated apparatus R 2 . As a transmission dedicated apparatus R in a subordinate node is added, it is made possible to upsize the system while the load on the superior node is minimized. Further, transmission target range DS 1 B, DR 1 B, DR 2 B, etc., can be added to the broadcast information transmission apparatus S 1  as required.  
         [0050]      FIG. 7  is a registration setting description drawing concerning superior agent (node), stored in the transmission dedicated apparatus R 1  and R 2  and the terminals K 1 A, K 1 B, K 2 A, and K 2 B in  FIG. 6 . The registration in the transmission dedicated apparatus R 1  indicates that the transmission source is the broadcast information transmission apparatus S 1  and that the transmission apparatus directly connected to the transmission dedicated apparatus R 1  is the broadcast information transmission apparatus S 1 . The registration in each of the terminal K 1 A and K 1 B indicates that the transmission source is the broadcast information transmission apparatus S 1  and that the transmission apparatus directly connected to the terminal K 1 A, K 1 B is the transmission dedicated apparatus R 1 . The terminals K 1 A and K 1 B register the transmission request pattern (PG 1 ) in the transmission dedicated apparatus R 1 . Therefore, the transmission dedicated apparatus R 1  transmits only the already registered transmission request pattern (PG 1 ) of the transmission information transmitted from the broadcast information transmission apparatus S 1  to the terminals K 1 A and K 1 B.  
         [0051]     The registration in the transmission dedicated apparatus R 2  indicates that the transmission source is the broadcast information transmission apparatus S 1  and that the transmission apparatus directly connected to the transmission dedicated apparatus R 2  is the transmission dedicated apparatus R 1 . The registration in each of the terminal K 2 A and K 2 B indicates that the transmission source is the broadcast information transmission apparatus S 1  and that the transmission apparatus directly connected to the terminal K 2 A, K 2 B is the transmission dedicated apparatus R 2 . The terminals K 2 A and K 2 B register the transmission request pattern (PG 2 ) in the transmission dedicated apparatus R 2 . Therefore, the transmission dedicated apparatus R 2  transmits only the already registered transmission request pattern (PG 2 ) of the transmission information transmitted through the transmission dedicated apparatus R 1  from the broadcast information transmission apparatus S 1  to the terminals K 2 A and K 2 B.  
         [0052]     The case where using SIP (RFC 3261, RFC 3265), each subordinate node is registered using a SUBSCRIBE message and broadcast information is transmitted using a NOTIFY message will be discussed with  FIGS. 8, 9 , and  10 . The specific detailed description of the subscribe and notify messages is given in SIP (RFC 3265/draft-ietf-simple-presence-07.txt) and therefore only the main part is shown in the description to follow.  
         [0053]      FIG. 8  shows a registration message processing sequence in the network configuration in  FIG. 6  the broadcast information transmission apparatus S 1  as the superior node is already registered (subscribed) to the transmission dedicated apparatus R 1  for transmission between them. The transmission dedicated apparatus R 1  in the superior node is already registered to the transmission dedicated apparatus R 2  for transmission between them.  
         [0054]     A subordinate node registration message IK 1 AR 1   a  called subscribe for making a request for registering (subscribing to) transmission is issued from the terminal K 1 A in the subordinate node to the transmission dedicated apparatus R 1 . The subordinate node registration message IK 1 AR 1   a  contains the transmission request information pattern (PG 1 ) and node information of the terminal K 1 A (K 1 @K 1 A-IP), which is registered as destination contact (registration number R 1 - 1  in  FIG. 9B ).  
         [0055]     Upon reception of the message, the transmission dedicated apparatus R 1  sends a subordinate node registration message IR 1 S 1   a   1  called subscribe to the broadcast information transmission apparatus (presence agent) S 1 . The subscribe message contains the transmission request information pattern (PG 1 ) and node information of the transmission dedicated apparatus R 1  (K 1 @R 1 -IP), which is registered as destination contact (registration number S 1 - 1  in  FIG. 9A ). The broadcast information transmission apparatus S 1  accomplishes registration and sends a subordinate node registration acknowledge message IS 1 R 1   a   1  to the transmission dedicated apparatus R 1 , which then informs the terminal K 1 A that registration of the terminal K 1 A is complete.  
         [0056]     That is, the transmission dedicated apparatus R 1  is registered in the broadcast information transmission apparatus S 1  based on the subordinate node registration message IR 1 S 1   a   1  and the subordinate node registration acknowledge message IS 1 R 1   a   1 . Registration of the terminal K 1 A is accomplished in the transmission dedicated apparatus R 1  based on the subordinate node registration message IK 1 AR 1   a  and a subordinate node registration acknowledge message IR 1 K 1 Aa. Accordingly, the transmission dedicated apparatus R 1  establishes subscription with the superior node (broadcast information transmission apparatus S 1 ) (transmission registration is complete).  
         [0057]     Subsequently, a subordinate node registration message IK 1 BR 1   a  called subscribe message for making a request for registering (subscribing to) transmission is issued from the terminal K 1 B in the subordinate node to the transmission dedicated apparatus R 1 . Upon reception of the message, the transmission dedicated apparatus R 1  checks on destination information data to see if the transmission request information pattern (PG 1 ) contained in the subscribe message is already stored for the terminal K 1 . If it is unregistered, it is registered in the transmission dedicated apparatus R 1  (registration number R 1 - 2 ). In this registration (registration number R 1 - 2  in  FIG. 9B ), destination information data containing the destination contact (sip:K 1 @K 1 B-IP), the node type (K), the subscribe validity term (for example, 100 seconds), and the transmission request information pattern (PG 1 ) is stored.  
         [0058]     At the same time, a subordinate node registration acknowledge message IR 1 K 1 Ba is sent to the terminal K 1 B and registration of the terminal K 1 B is complete. Registration of the transmission dedicated apparatus R 1  in the broadcast information transmission apparatus S 1  is already complete based on the subordinate node registration message IR 1 S 1   a   1  and the subordinate node registration acknowledge message IS 1 R 1   a   1 . That is, the transmission dedicated apparatus R 1  establishes subscription with the broadcast information transmission apparatus S 1  in the superior node.  
         [0059]     Likewise, a subordinate node registration message IK 2 AR 2   a  (subscribe message) is issued from the terminal K 2 A to the transmission dedicated apparatus R 2 . The subscribe message contains the transmission request information pattern (PG 2 ) and node information of the terminal K 2 A (K 2 @K 2 A-IP), which is registered as destination contact (registration number R 2 - 1 ). The transmission dedicated apparatus R 2  accomplishes registration and sends a subordinate node registration message IR 2 R 1   a  to the transmission dedicated apparatus R 1  as a subscribe message.  
         [0060]     Then, since the transmission request pattern (PG 2 ) of the terminal K 2 A differs from the already stored pattern (PG 1 ), the transmission dedicated apparatus R 1  accomplishes registration of the transmission dedicated apparatus R 2  (registration number R 1 - 3 ) and transmits a subordinate node registration message IR 1 S 1   a   2  to the broadcast information transmission apparatus S 1  as a subscribe message setting the transmission request pattern (PG 2 ) and node information of the transmission dedicated apparatus R 1  (K 2 @R 1 -IP). Upon reception of the subordinate node registration message IR 1 S 1   a   2  as a subscribe message, the broadcast information transmission apparatus S 1  stores the destination contact to transmit broadcast information (sip:K 2 @R 1 -IP), the node type (R), the validity term (for example, 60 seconds), the dialog (Dig 4 ) specifying the dialog mode, and the transmission request pattern (PG 2 ) as destination information data (registration number S 1 - 2 ).  
         [0061]     At the same time as storing the destination information data, the broadcast information transmission apparatus S 1  transmits a subordinate node registration acknowledge message IS 1 R 1   a   2 A 2  to the transmission dedicated apparatus R 1 . Upon reception of the message, the transmission dedicated apparatus R 1  validates registration of the transmission dedicated apparatus R 2  (registration number R 1 - 3 ) and immediately transmits a subordinate node registration acknowledge message IR 1 R 2   a  to the transmission dedicated apparatus R 2 . Upon reception of the message, the transmission dedicated apparatus R 2  validates registration of the terminal K 2 A (registration number R 2 - 1 ) and transmits a subordinate node registration acknowledge message IR 2 K 2 Aa to the terminal K 2 A. Accordingly, the transmission dedicated apparatus R 2  establishes subscription with the superior node (broadcast information transmission apparatus S 1 ) (contacts with the superior node for transmission).  
         [0062]     Subsequently, a subordinate node registration message IK 2 BR 2   a  for making a request for registering transmission as a subscribe message is issued from the terminal K 2 B in the subordinate node to the transmission dedicated apparatus R 2 . Upon reception of the registration request, the destination contact (sip:K 2 @K 2 B-IP), the node type (K), the validity term (for example, 60 seconds), the dialog (Dig 7 ) of the dialog mode, and the transmission request pattern (PG 2 ) are registered in the transmission dedicated apparatus R 2  (registration number R 2 - 2 ). Since the transmission dedicated apparatus R 2  has already established subscription with the transmission dedicated apparatus R 2  (superior node) for the transmission request pattern (PG 2 ), the registration (registration number R 2 - 2 ) is validated immediately and a subordinate node registration acknowledge message IR 2 K 2 Ba is sent to the terminal K 2 B. Registration of the terminal K 2 B is complete. Registration of the transmission dedicated apparatus R 2  in the broadcast information transmission apparatus S 1  is already complete based on the subordinate node registration messages IR 2 R 1   a  and IR 1 S 1   a   2  and the subordinate node registration acknowledge messages IS 1 R 1   a   2  and IR 1 R 2   a.    
         [0063]      FIGS. 9A, 9B  and  9 C show the subordinate node registration description registered in subordinate nodes as the result of the registration message processing in  FIG. 8 . The subordinate nodes to the broadcast information transmission apparatus S 1  are registered in (a), the subordinate nodes to the transmission dedicated apparatus R 1  are registered in (b), and the subordinate nodes to the transmission dedicated apparatus R 2  are registered in (c). The registration in the registration numbers S 1 - 1  and S 1 - 2  is as follows: The identifiers of the transmission dedicated apparatus R 1  and R 2  are registered under the destination contact; the transmission dedicated apparatus R under the type; 100 seconds and 60 seconds, for example, under the registration validity term; Dig 1  and Dig 4  under the dialog (dialog mode); and PG 1  and PG 2  under the transmission request pattern.  
         [0064]     In  FIG. 9B , the registration numbers R 1 - 1  to R 1 - 3  of the subordinate nodes to the transmission dedicated apparatus R 1  are included and the registration is as follows: The identifiers of the terminals K 1 A and K 1 B and the transmission dedicated apparatus R 2  are registered under the destination contact (destination information); two terminals K and one transmission dedicated apparatus R under the type; 100 seconds, 100 seconds, and 60 seconds, for example, under the registration validity term; Dig 1 , Dig 3 , and Dig 5  under the dialog (dialog mode); and PG 1 , PG 1 , and PG 2  under the transmission request pattern.  
         [0065]     In  FIG. 9C , the registration numbers R 2 - 1  and R 2 - 2  of the subordinate nodes to the transmission dedicated apparatus R 2  are included and the registration is as follows: The identifiers of the terminals K 2 A and K 2 B are registered under the destination contact (destination information); two terminals K under the type; 60 seconds and 60 seconds, for example, under the registration validity term; Dig 6  and Dig 7  under the dialog (dialog mode); and PG 2  and PG 2  under the transmission request pattern.  
         [0066]      FIG. 10  shows a transmission message processing sequence in the network configuration in  FIG. 6 . In  FIGS. 9A-9C , the transmission dedicated apparatus R 1  is already registered in the broadcast information transmission apparatus S 1  of the presence agent. Then, an information notification message IS 1 R 1   b   1  called NOTIFY is sent to the transmission dedicated apparatus R 1 . The information notification message IS 1 R 1   b   1  contains notify message setting the transmission request patterns (PG 1  and PG 2 ) of the destination contacts (sip:K 1 @R 1 -IP and sip:K 2 @R 1 -IP) of the destination information data registered in the registration numbers S 1 - 1  and S 1 - 2  in  FIG. 9A . Upon reception of the message, the transmission dedicated apparatus R 1  sends an information notification acknowledge message IR 1 S 1   b   1  to the broadcast information transmission apparatus S 1  to inform the broadcast information transmission apparatus S 1  that the message has been received. Upon reception of the information notification acknowledge message IR 1 S 1   b   1 , the broadcast information transmission apparatus S 1  stops resending the notify message to the transmission dedicated apparatus R 1 .  
         [0067]     The transmission dedicated apparatus R 1  stores the contents of the transmission request patterns (PG 1  and PG 2 ) in the notify message received with the information notification message IS 1 R 1   b   1  as the destination information data. The transmission dedicated apparatus R 1  sends notify messages setting transmission information (PG 1  to K 1 A and K 1 B and PG 2  to R 2 ) to the destination contacts (sip:K 1 @K 1 A-IP, sip:K 1 @K 1 B-IP, and sip:K 2 @R 2 -IP, registration numbers R 1 - 1 , R 1 - 2 , and R 1 - 3  in  FIG. 9B ) stored as the destination information data at regular time intervals as it sends information notification messages IR 1 K 1 Ab, IR 1 K 1 Bb, and IR 1 R 2   b  to the terminals K 1 A and K 1 B and the transmission dedicated apparatus R 2 .  
         [0068]     Upon reception of the messages, the terminals K 1 A and K 1 B and the transmission dedicated apparatus R 2  send information notification acknowledge messages IK 1 AR 1   b , IK 1 BR 1   b , and IR 2 R 1   b  to the transmission dedicated apparatus R 1  to inform the transmission dedicated apparatus R 1  that the messages have been received. Upon reception of the information notification acknowledge messages, the transmission dedicated apparatus R 1  stops resending the notify messages to the terminals K 1 A and K 1 B and the transmission dedicated apparatus R 2 . The terminals K 1 A and K 1 B display reception of the transmission information (PG 1 ).  
         [0069]     The transmission dedicated apparatus R 2  stores the transmission information according to the transmission pattern (PG 2 ) in the notify message received with the information notification message IR 1 R 2   b  as destination information data. When already stored transmission information exists, it is updated with the most recent transmission information (PG 2 ). The transmission dedicated apparatus R 2  sends notify messages setting transmission information (PG 2 ) to the destination contacts (sip:K 2 @K 2 A-IP and sip:K 2 @K 2 B-IP, registration numbers R 2 - 1  and R 2 - 2  in  FIG. 9C ) stored as the destination information data at regular time intervals as it sends information notification messages IR 2 K 2 Ab and IR 2 K 2 Bb to the terminals K 2 A and K 2 B.  
         [0070]     Upon reception of the messages, the terminals K 2 A and K 2 B send information notification acknowledge messages IK 2 AR 2   b  and IK 2 BR 2   b  to the transmission dedicated apparatus R 2  to inform the transmission dedicated apparatus R 2  that the messages have been received. Upon reception of the information notification acknowledge messages IK 2 AR 2   b  and IK 2 BR 2   b , the transmission dedicated apparatus R 2  stops resending the notify messages. The terminals K 2 A and K 2 B display reception of the transmission information (PG 2 ).  
         [0071]     According to the multicast communications in the related art example, in  FIG. 6 , the transmission dedicated apparatus R 1  and R 2  do not exist and the broadcast information transmission apparatus S 1  transmits information collectively to the terminals K 1 A, K 1 B, K 2 A, and K 2 B by multicast communications. That is, the communication network management problem (problem 1), the problem of a sudden increase in traffic (problem 2), and the secret information leak problem (problem 3) in the multicast communications described above are involved. As shown in  FIGS. 9A-9C , according to the invention, any desired information can be transmitted in any desired format separately to each of the terminals K 1 A, K 1 B, K 2 A, and K 2 B according to their respective transmission requests and dialogs (dialog modes).  
         [0072]     In contrast, according to the multicast communications in the related art, the broadcast information transmission apparatus S 1  transmits the same information in the same format collectively to the terminals K 1 A, K 1 B, K 2 A, and K 2 B, and the information transmitted to the terminals K 1 A and K 1 B is also transmitted to the terminals K 2 A and K 2 B desiring transmission of different information. That is, the secret information leak problem (problem 3) and the information flow problem (problem 4) of being unable to transmit necessary information only to the necessary locations in the multicast communications described above arise. In contrast, in the invention, the problems do not arise.  
         [0073]     In the unicast communications in the related art, the transmission processing centralization problem (problem 5) described above arises. According to the invention, the broadcast information transmission apparatus S 1  and the transmission dedicated apparatus R 1  and R 2  take charge of their respective transmission target ranges DS 1 , DR 1 , and DR 2  and transmit information separately to the terminals K 1 A, K 1 B, K 2 A, and K 2 B by unicast communications, so that the transmission processing centralization problem (problem 5) does not arise.  
         [0074]     The broadcast information transmission apparatus S 1  and the transmission dedicated apparatus R 1  and R 2  take charge of their respective transmission target ranges DS 1 , DR 1 , and DR 2 . Separate unicast communications occurring here occur in the transmission target ranges DS 1 , DR 1 , and DR 2  in a transmission manner, so that the traffic amount increase problem (problem 6) described above does not arise either in the invention. Further, the broadcast information transmission apparatus S 1  and the transmission dedicated apparatus R 1  and R 2  take charge of their respective transmission target ranges DS 1 , DR 1 , and DR 2  for transmitting information, so that the broadband and high transmission processing capability problem (problem 7) described above does not arise either in the invention. The advantages will be easily understood from the description previously given with reference to  FIG. 6 .