Patent Publication Number: US-2016234263-A1

Title: Management system, communication system, management method, and recording medium

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a management system, a communication system, a management method, and a recording medium. 
     2. Description of the Related Art 
     In recent years, in accordance with, for example, a demand for reducing travel cost and time, a communication system which provides calling and conferencing over a communication network such as the Internet or a dedicated line or the like has become popular. In this kind of communication system, when a communication between communication terminals is started, content data such as image data and audio data are sent and received, and thus, communications between sites are realized. 
     Further, a method is known in which, responding to a connection request from a video phone, a currently available operator terminal is selected, and a communication channel for video and audio is established between the selected operator terminal and the video phone (refer to Patent Document 1). 
     According to Patent Document 1, it is disclosed that in the case where two or more terminals are waiting for a communication to start, a call is automatically provided for the terminal whose waiting time is the longest. 
     However, if a method is used in which the call is automatically provided for the terminal whose waiting time is the longest, then, there is a problem that, when a communication session between terminals are disrupted, the disrupted communication session can only be reestablished after a call is provided for a terminal that had requested a communication to start before the disruption. 
     SUMMARY OF THE INVENTION 
     A management system according to the present invention includes a management unit configured to, when communication between a communication-start-requesting-source communication terminal and a destination communication terminal is disrupted, store specifying information for specifying the communication-start-requesting-source communication terminal, and a selection unit configured to, when a plurality of the communication terminals are requesting a communication start with the destination communication terminal, select one of the plurality of the communication terminals to be connected to the destination communication terminal based on the specifying information stored by the management unit. 
     As described above, according to the present invention, when reconnecting to reestablish the communications between communication terminals after the communication has been disrupted, it becomes possible to make the reconnection before a call is provided for a communication terminal that had requested a call to start before the disruption. 
     CITATION LIST 
     Patent Document 
     [Patent Document 1] Japanese Laid-Open Patent Application No. 2005-064860 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a communication system according to an embodiment. 
         FIG. 2  is an external view of a terminal according to an embodiment. 
         FIG. 3  is a hardware configuration diagram of a terminal according to an embodiment. 
         FIG. 4  is a hardware configuration diagram of a management system, a relay apparatus, a program providing system, or a maintenance system according to an embodiment. 
         FIG. 5  is a software configuration diagram of a terminal according to an embodiment. 
         FIG. 6  is a functional block diagram of a terminal and a management system included in a communication system according to an embodiment. 
         FIG. 7A  is a conceptual diagram of a terminal management table managed by a management system.  FIG. 7B  is a conceptual diagram of a waiting information management table managed by the management system. 
         FIG. 8  is a sequence diagram illustrating a process of starting a communication. 
         FIG. 9  is a flowchart illustrating a process of selecting a terminal. 
         FIG. 10  is a sequence diagram illustrating a process of reconnection of a terminal. 
         FIG. 11  is a flowchart illustrating a process of selecting a terminal. 
         FIG. 12  is a flowchart illustrating a process of selecting a terminal. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, referring to the drawings, an embodiment of the present invention will be described in detail. It should be noted that, in the following, “communication terminal” may be simply described as “terminal”, and “communication management system” may be simply described as “management system”. 
     &lt;&lt;Overall Configuration of Communication System  1 &gt; 
       FIG. 1  is a schematic diagram of a communication system  1  according to an embodiment of the present invention. As shown in  FIG. 1 , the communication system  1  includes a plurality of terminals ( 10   aa ,  10   ab , . . . ), displays ( 120   aa ,  120   ab , . . . ) for the terminals ( 10   aa ,  10   ab , . . . ), a plurality of relay apparatuses ( 30   a ,  30   b ,  30   c ,  30   d ,  30   e ), a management system  50 , a program providing system  90 , and a maintenance system  100 . A video conference, or the like, between remote places can be realized by having communication of image data or audio data as an example of content data performed by the communication system  1 . It should be noted that a plurality of routers ( 70   a ,  70   b ,  70   c ,  70   d ,  70   ab ) select an optimal route of the content data. 
     The terminals ( 10   aa ,  10   ab ,  10   ac , . . . ), the relay apparatus  30   a , and the router  70   a  are connected to each other and are capable of communicating with each other via a LAN  2   a . The terminals ( 10   ba ,  10   bb ,  10   bc , . . . ), the relay apparatus  30   b , and the router  70   b  are connected to each other and are capable of communicating with each other via a LAN  2   b . Further, the LAN  2   a  and the LAN  2   b  are connected to each other and are capable of communicating with each other by a dedicated line  2   ab  including the router  70   ab . Further, the LAN  2   a , the LAN  2   b , and the dedicated line  2   ab  are provided in a predetermined area X. It should be noted that the devices are not necessarily connected to each other by the dedicated line, but they may be directly connected to the Internet  2   i.    
     The terminals ( 10   ca ,  10   cb ,  10   cc , . . . ), the relay apparatus  30   c , and the router  70   c  are connected to each other and are capable of communicating with each other via a LAN  2   c . The LAN  2   c  is provided in a predetermined area Y. 
     The terminals ( 10   da ,  10   db ,  10   dc , . . . ), the relay apparatus  30   d , and the router  70   d  are connected to each other and are capable of communicating with each other via a LAN  2   d . The LAN  2   d  is provided in a predetermined area Z. The area X, the area Y, and the area Z may be in the same country or in different countries. 
     The area X, the area Y, and the area Z are connected to each other and are capable of communicating with each other via the Internet  2   i  through respective routers ( 70   ab ,  70   c ,  70   d ). It should be noted that a call center is located in the area Z. Each terminal  10  in the area X and the area Y can receive a reception service by connecting to terminals ( 10   da ,  10   db ,  10   dc , . . . ) in the call center. 
     It should be noted that, in the following, an arbitrary terminal of the terminals ( 10   aa ,  10   ab , . . . ) is described a “terminal  10 ”, an arbitrary display of the displays ( 120   aa ,  120   ab , . . . ) is described as a “display  120 ”, and an arbitrary relay apparatus of the relay apparatuses ( 30   a ,  30   b ,  30   c ,  30   d ,  30   e ) is described as a “relay apparatus  30 ”. Further, an arbitrary router of the routers ( 70   a ,  70   b ,  70   c ,  70   d ,  70   ab ) is described as a “router  70 ”. 
     Further, the management system  50 , the program providing system  90 , and the maintenance system  100  are connected to the Internet  2   i . It should be noted that the management system  50 , the program providing system  90 , and the maintenance system  100  may be located in the areas (X, Y, Z), or may be located in an area other than the areas (X, Y, Z). 
     Further, a communication network  2  according to the present embodiment includes the LAN  2   a , the LAN  2   b , the dedicated line  2   ab , the Internet  2   i , LAN  2   c , and the LAN  2   d . In the communication network  2 , there may be an area in which not only wired communication is performed, but also wireless communication such as communication via WiFi (Wireless Fidelity), Bluetooth (registered trade mark), a mobile telephone network or the like is performed. 
     Further, in  FIG. 1 , a set of four numbers shown under each terminal  10 , the relay apparatus  30 , the management system  50 , each router  70 , the program providing system  90 , or the maintenance system  100  illustrates a typical IP address of IPv4 in a simplified manner. For example, an IP address of the terminal  10   aa  is “1. 2. 1. 3”. Further, instead of IPv4, IPv6 may be used. However, for the purpose of simplicity, IPv4 is used in the description. 
     Further, in each terminal  10 , when a video conference application  1031  or a reception application  1032  which will be described later is started, communications between users become available by sending and receiving content data including audio data or image data. Further, the terminal  10  sends and receives call data by using a predetermined communication method (a call control method for connecting or disconnecting with a destination, and a coding method for IP packetizing the call data). It should be noted that, in the following, “application” may be abbreviated as “appl” for short. 
     Further, as the call control method described above, (1) SIP (Session Initiation Protocol), (2) H.323, (3) enhanced SIP protocol, (4) protocol for instant messenger, (5) protocol utilizing a MESSAGE method of SIP, (6) protocol of Internet Relay Chat (IRC), (7) protocol enhanced from a protocol for instant messenger, or the like, can be listed. The above (4) protocol for instant messenger is a protocol used for, for example, (4-1) Extensible Messaging and Presence Protocol (XMPP), (4-2) ICQ (registered trademark), AIM (registered trademark), or Skype (registered trademark). Further, the above (7) Jingle, for example, is a protocol enhanced from the protocol for instant messenger. 
     &lt;&lt;Hardware Configuration of the Embodiment&gt;&gt; 
     Next, a hardware configuration of the present embodiment will be described.  FIG. 2  is an external view of a terminal  10  according to an embodiment. As shown in  FIG. 2 , the terminal  10  includes a housing  1100 , an arm  1200 , and a camera housing  1300 . In a front wall  1120  of the housing  1100 , there is an air intake surface  1121  formed with a plurality of air intake holes, and, in a rear wall  1110  of the housing  1100 , there is an air exhaust surface formed with a plurality of air exhaust holes. With the above arrangement, by driving a cooling fan embedded in the housing  1100 , it becomes possible to take in air in front of the terminal  10  through the air intake surface  1121 , and to exhaust the air to the rear of the terminal  10  through the air exhaust surface. In a right side wall  1130  of the housing  1100 , a sound pickup hole  1131  is formed, and, by using a built-in mike  114  which will be described later, sound such as voice, sound of things, noise, etc., can be picked up. 
     In the right wall  1130  side of the housing  1100 , an operation panel  1150  is formed. In the operation panel  1150 , there are a plurality of operation buttons ( 108   a  through  108   e ), a power supply switch  109 , and an alarm lamp  119 , which will be described later. Also, a sound output surface  1151  is formed in the operation panel  1150 , which is formed by a plurality of sound output holes used for passing output sound from a built-in speaker  115  which will be described later. Further, in the left wall  1140  side of the housing  1100 , a housing unit  1160  is formed as a concave portion for housing the arm  1200  and the camera housing  1300 . In the right wall  1130  of the housing  1100 , a plurality of connection ports ( 1132   a  through  1132   c ) are formed for electrically connecting cables for an external device connection interface  118  which will be described later. On the other hand, in the left wall  1140  of the housing  1100 , a connection port is formed for electrically connecting a cable  120   c  of a display  120  for a display interface (I/F)  117 . 
     It should be noted that, in the following, an arbitrary operation button of the operation buttons ( 108   a  through  108   e ) will be described as an “operation button  108 ”, and an arbitrary connection port of the connection ports ( 1132   a  through  1132   c ) will be described as a “connection port  1132 ”. 
     Next, the arm  1200  is attached to the housing  1100  via a torque hinge  1210 , and is capable of rotating in an up-and-down direction within a range of tilt angle θ 1  of 135 degrees with respect to the housing  1100 .  FIG. 2  illustrates a state in which the tilt angle is 90 degrees. 
     In the camera housing  1300 , there is a built-in camera  112  which will be described later and is capable of taking images of a user, a document, a room, etc. Further, in the camera housing  1300 , a torque hinge  1310  is formed. Further, the camera housing  1300  is attached to the arm  1200  via the torque hinge  1310 , and is capable of rotating in a right-and-left direction within a range of +/−180 degrees of pan angle θ 2 , and rotating in an up-and-down direction within a range of +/−45 degrees of tilt angle θ 3 , with respect to the arm  1200 , assuming that  FIG. 2  illustrates a state in which θ 2  and θ 3  are zero degrees. 
     It should be noted that an external view of the terminal  10  is not limited to the view shown in  FIG. 2 , which is just an example. As another example, the terminal  10  may be a general-purpose computer, a mobile phone terminal, a projector, an electronic white board, digital signage, or the like (refer to terminals ( 10   ac ,  10   cc ) in  FIG. 1 ). When a computer used for the terminal  10  does not include a mike and a camera, an external mike and an external camera can be connected to the computer. Further, in the case where the terminal  10  is a mobile telephone terminal, or the like, the terminal  10  may be connected to the Internet  2   i  through wireless communication utilizing a wireless LAN, a mobile telephone network, etc. As described above, a general-purpose computer or a mobile telephone terminal can be used as a terminal  10  according to the present embodiment. Further, in the case where a general-purpose computer is used as a terminal  10 , an application may be installed beforehand which causes the computer to perform processes of the terminal  10  which will be described later. 
     It should be noted that external views of the management system  50 , the program providing system  90 , and the maintenance system  100  are the same as an external view of a typical server computer, and thus, descriptions of the external views will be omitted. 
       FIG. 3  is a hardware configuration of a terminal  10  according to an embodiment. The terminal  10  includes a central processing unit (CPU)  101  for controlling overall operations of the terminal  10 , a read only memory (ROM)  102  in which programs used for driving the CPU  101  such as an initial program loader are stored, a random access memory (RAM)  103  which is used for a work area of the CPU  101 , a flash memory  104  in which programs for the terminal  10 , and various kinds of data including image data, audio data, etc., are stored, a solid state drive (SSD)  105  which controls writing and reading the various data to and from the flash memory  104  according to the control of the CPU  101 , a media interface  107  which controls writing and reading data to and from a recording medium  106  including a flash memory, an integrated circuit (IC) card, etc., the operation buttons  108  operated for, for example, selecting a destination of the terminal  10 , the power supply switch  109  for switching ON/OFF the power supply of the terminal  10 , and a network interface (I/F)  111  for performing data transmission by utilizing the communication network  2 . 
     Further, the terminal  10  includes the built-in camera  112  which captures image data by taking an image of a subject according to the control of the CPU  101 , an imaging element interface  113  which controls driving of the camera  112 , the built-in mike  114  for inputting sound, a built-in speaker  115  for outputting sound, a sound input/output interface  116  for processing input/output of an audio signal between the mike  114  and the speaker  115  according to the control of the CPU  101 , the display interface (I/F)  117  for transmitting image data to the external display  120  according to the control of the CPU  101 , the external device connection interface (I/F)  118  for connecting various external devices, the alarm lamp  119  for indicating an error of various functions of the terminal  10 , and a bus line  110  such as an address bus, a data bus, etc., for electrically connecting the above elements as shown in  FIG. 3 . 
     The display  120  is a display unit which includes a liquid crystal or an organic electroluminescence (EL) panel used for displaying a subject image, or the like. Further, the display  120  is connected to the display I/F  117  via the cable  120   c . The cable  120   c  may be a cable for an analog RGB (VGA) signal, a cable for a component video, or a cable for a signal of High-Definition Multimedia Interface (HDMI) (registered trademark) or Digital Video Interactive (DVI). 
     The camera  112  includes a lens and a solid-state image sensing device which is used for converting light into electricity and computerizing the subject image, and as the solid-state image sensing device, Complementary Metal Oxide Semiconductor (CMOS), Charge Coupled Device (CCD), etc., are used. 
     To the external device connection I/F  118 , via a Universal Serial Bus (USB) cable, or the like, which is inserted into the connection port  1132  of the housing  1100 , external devices such as an external camera, an external mike, and an external speaker can be electrically connected. In the case where the external camera is connected, according to the control of the CPU  101 , priority is given to the external camera to be driven over the built-in camera  112 . Similarly, in the case where an external mike is connected or an external speaker is connected, according to the control of the CPU  101 , priority is given to the external mike or the external speaker over the built-in mike  114  or the built-in speaker  115 , respectively. 
     It should be noted that the recording medium  106  is detachable from the terminal  10 . Further, it is not limited to the flash memory  104  that is used, and, Electrically Erasable and Programmable ROM (EEPROM), or the like may be used as long as it is a non-volatile memory to/from which data are written/read according to the control of the CPU  101 . 
       FIG. 4  is a hardware configuration diagram of a management system  50  according to an embodiment. The management system  50  includes a CPU  201  for controlling overall operations of the management system  50 , a ROM  202  in which programs used for driving the CPU  201  such as an IPL are stored, a RAM  203  which is used for a work area of the CPU  201 , a HD  204  for storing various data including programs for the management system  50 , etc., a hard disk drive (HDD)  205  for controlling various data reading and data writing of the HD  204  according to the control of the CPU  201 , a medium drive  207  for controlling data reading and data writing (storage) of a recording medium  206  including a flash memory, a display  208  for displaying various information items including a cursor, a menu, a window, a character, or an image, a network interface (I/F)  209  for performing data communications by using the communication network  2 , a keyboard  211  including a plurality of keys for inputting a character, a numerical value, various instructions, etc., a mouse  212  for selecting and executing various instructions, selecting a process target, moving the cursor, or the like, a compact disc read only memory (CD-ROM) drive  214  for controlling various data reading of a CD-ROM  213  as an example of a detachable recording medium, and a bus line  210  such as an address bus, a data bus, etc., for electrically connecting the above elements as shown in  FIG. 4 . 
     On the other hand, the relay apparatus  30 , the program providing system  90 , and the maintenance system  100  have similar hardware configurations as the above management system  50 , and thus, the descriptions will be omitted. 
       FIG. 5  is a software configuration of a terminal  10  according to an embodiment. As shown in  FIG. 5 , an OS  1020 , the video conference application  1031 , and the reception application  1032  are held in a work area  1010  of the RAM  103 . The OS  1020  and the applications ( 1031 ,  1032 ) are installed in the terminal  10 . 
     Further, the OS  1020  provides basic functions, and is basic software which controls the entire terminal  10 . The video conference application  1031  is an application for connecting with another terminal  10  and performing the video conference. The reception application  1032  is an application for connecting with a terminal  10  of a call center, and communicating with an operator. 
     It should be noted that the above applications ( 1031 ,  1032 ) are just examples, and other applications may be installed. In the case where the other applications are installed, the other applications may be stored in the program providing system  90 , and the other applications may be downloaded according to a request from the terminal  10 . Further, in the case where two or more video conference applications are installed, video conference applications with different protocols such as the above (1) through (7) may be installed. 
     &lt;&lt;Functional Configuration of Embodiment&gt;&gt; 
     Next, a functional configuration of the communication system of the present embodiment will be described. 
       FIG. 6  is a functional block diagram of a terminal  10  and a management system  50  included as a part of a communication system  1  according to an embodiment. It should be noted that, in  FIG. 6 , the terminal  10  and the management  50  are connected to perform data communications via a communication network  2 . 
     &lt;Functional Configuration of Communication Terminal&gt; 
     The terminal  10  includes a sending and receiving unit  11 , an operation input receiving unit  12 , a display control unit  13 , and a storing and reading unit  19 . The above units are functions which are realized by any one of the elements shown in  FIG. 3  which operates according to instructions from the CPU  101  which executes a program read from the flash memory  104  and written to the RAM  103 . 
     Further, the terminal  10  includes a memory unit  1000  including a ROM  102 , a RAM  103 , and a flash memory  104  as shown in  FIG. 3 . 
     Next, the functional configuration of the terminal  10  will be described in detail. It should be noted that when the functional configuration of the terminal  10  is described, relations between functions and main elements of the elements shown in  FIG. 3 , which are used for realizing the functions, will also be described. 
     The sending and receiving unit  11  is realized by instructions from the CPU  101  and the network I/F  111 , and performs sending and receiving various data (or information) to and from a terminal, an apparatus, a system, etc., with which the sending and receiving unit  11  communicates. 
     The operation input accepting unit  12  is realized by instructions from the CPU  101 , the operation buttons ( 108   a ,  108   b ,  108   c ,  108   d ,  108   e ) and the power supply switch  109 , and accepts various inputs or various selections made by a user. 
     The display control unit  13  is realized by instructions from the CPU  101  and the display I/F  117 , and controls outputting an image from the display  120  based on image data sent from the communication destination terminal  10 . 
     The storing and reading unit  19  is realized by instructions from the CPU  101  and the SSD  105  or by instructions from the CPU  101 , and performs a process of storing various data in the memory unit  1000  and reading the various data stored in the memory unit  1000 . 
     &lt;Functional Configuration of Management System&gt; 
     The management system  50  includes a sending and receiving unit  51 , a management unit  53 , a session control unit  58 , and a storing and reading unit  59 . The above units are functions or means which are realized by any one of elements shown in  FIG. 4  which operates according to instructions from the CPU  201  which executes a program for the management system  50  read from the HD  204  and written to the RAM  203 . Further, the management system  50  includes a memory unit  5000  including the HD  204 . In the memory unit  5000 , the databases (DB) including corresponding tables as shown below are included. 
     (Terminal Management Table) 
       FIG. 7A  is a conceptual diagram illustrating a terminal management table. In the memory unit  5000 , a terminal management database (DB)  5002  including a terminal management table as shown in  FIG. 7A  is included. In the terminal management table, for each communication ID of a terminal  10 , a destination name (terminal name) when the terminal  10  is a destination, an operating state of the terminal  10 , and an IP address of the terminal  10  are associated with the communication ID and stored. It should be noted that the communication ID is information for identifying the terminal  10  as a communication destination in the communication system  1 . The communication ID is not limited as long as it can identify the terminal  10  as a communication destination, and identification information of the terminal  10 , account information of a user of the terminal  10 , etc., are included as the communication ID. In the following, the descriptions will be continued assuming that communication IDs of the terminals ( 10   aa ,  10   ab ,  10   ac ,  10   db ) are “ 01   aa ,  01   ab ,  01   bc ,  01   db ”, respectively. Further, an operation state “OFFLINE” indicates a state in which the terminal  10  is not connected to the management system  50 . An operation state “ONLINE” indicates a state in which the terminal  10  is connected to the management system  50 . An operation state “ONLINE (TALKING)” indicates a state in which the terminal  10  is connected to the management system  50 , and is communicating with another terminal  10 . 
     (Waiting Information Management Table) 
       FIG. 7B  is a conceptual diagram illustrating a waiting information management table. In the memory unit  5000 , a waiting information management database (DB)  5012  including a waiting information management table as shown in  FIG. 7B  is included. In the waiting information management table, with respect to the communication ID of the terminal  10  of an operator as a communication destination, a communication ID of a terminal  10  of a customer as a start requesting source which is waiting for a start of talking with the operator, accepting time of start request, and connection type information are associated with the communication ID of the terminal  10  of the operator, and stored. In the above connection type information, “N/W Error” which indicates a reconnection after disruption due to a network error, and “Normal” which indicates a connection other than the “N/W Error” are included. It should be noted that, as a network error, an error in which the terminal  10  is disconnected from the communication network  2  due to lack of bandwidth between the terminals  10  can be listed. 
     &lt;Functional Configuration of Management System&gt; 
     Next, a functional configuration of the management system  50  will be described in detail. It should be noted that when the functional configuration of the management system  50  is described, relations between functions and main elements of the elements shown in  FIG. 4 , which are used for realizing the functions of the management system  50 , will be also described. 
     The sending and receiving unit  51  is realized by instructions from the CPU  201  and the network I/F  209 , and performs sending and receiving various data (or information) to and from a terminal, an apparatus, or a system via the communication network  2 . 
     The management unit  53  is realized by instructions from the CPU  201  and performs a process of updating an operation state in the terminal management table in order to reflect the latest operation state. 
     The session control unit  58  is realized by instructions from the CPU  201 , and controls a session for sending and receiving content data between the terminals  10 . In the above control, establishing a session, controlling the terminal  10  to participate in the established session, and terminating the session are included. Further, the session control unit  58  performs measurement of a communication bandwidth of the communication network  2  between the terminals  10 . 
     The storing and reading unit  59  is realized by instructions from the CPU  201  and the HDD  205  or by instructions from the CPU  201 , and performs a process of storing various data in the memory unit  5000  and reading the various data stored in the memory unit  5000 . 
     &lt;&lt;Processes and Operations of Communication System  1 &gt;&gt; 
     Next, processes and operations of the communication system  1  will be described. 
     First, a process will be described in which a destination terminal  10   db  becomes available to start new communication and a terminal  10   aa  as a start requesting source which has been waiting for a start of communication with the terminal  10   db  starts the communication.  FIG. 8  is a sequence diagram illustrating a process of starting communication. In each of the terminals ( 10   aa ,  10   ab ,  10   ac ), when a reception application  1032  is started, corresponding sending and receiving unit  11  sends a request to the management system  50  for starting communication with a terminal  10   db  of an operator. The terminal  10   ac , which has sent a request for starting communication the earliest, is in communication with the terminal  10   db . On the other hand, the terminal  10   aa  and the terminal  10   ab  are waiting for the start of the communication with the terminal  10   db . At this time, the waiting information management table is in a state shown in  FIG. 7B . 
     When the operation input accepting unit  12  of the terminal  10   db  accepts a request for terminating the communication with the terminal  10   ac , the sending and receiving unit  11  sends a request for terminating the communication to the management system  50  (step S 21 ). In the request for terminating the communication, a communication ID “ 01   db ” of the terminal  10   db  itself and a communication ID “ 01   ac ” of the terminal  10   ac  of the communication destination are included. 
     The session control unit  58  of the management system  50 , based on the communication ID included in the request for terminating the communication, terminates a session for sending content data between the terminals ( 10   ac ,  10   db ) (step S 22 ). With the above process, the communication between the terminals ( 10   ac ,  10   db ) is terminated. 
     When the communication between the terminals ( 10   ac ,  10   db ) is terminated, the management unit  53  updates operation states associated with the communication IDs of the terminals ( 10   ac ,  10   db ) from “ONLINE (TALKING)” to “ONLINE” (step S 23 ). 
     When the operation state of the terminal  10   db  is updated to “ONLINE” and the terminal  10   db  moves to a state in which new communication can be started, the session control unit  58  of the management system  50  selects a communication ID of a terminal  10  which should be connected to the terminal  10   db  from the communication IDs of the terminals  10  of the communication start requesting sources stored in the waiting information management table (step S 24 ). A process of step S 24  will be described referring to  FIG. 9 .  FIG. 9  is a flowchart illustrating a process of selecting a terminal  10 . 
     First, the session control unit  58 , referring to a field of connection type information of the waiting information management table, determines whether “N/W Error” is recorded (step S 24 - 1 ). In the case where it is determined that the “N/W Error” is recorded (YES in step S 24 - 1 ), the storing and reading unit  59  selects and reads a communication ID, which is associated with the connection type information “N/W Error”, of the communication start requesting sources associated with the communication ID “ 01   db ” of the destination in the waiting information management table (step S 24 - 2 ). In the case where it is determined that “N/W Error” is not recorded (NO in step S 24 - 1 ), the storing and reading unit  59  selects and reads a communication ID, whose accepting time is the earliest, of the communication start requesting sources associated with the communication ID “ 01   db ” of the destination in the waiting information management table (step S 24 - 3 ). 
     When the communication ID is read in step S 24 - 2  or in step S 24 - 3 , the storing and reading unit  59  removes a record from the waiting information management table in which record the read communication ID is included (step S 24 - 4 ). 
     In the following, the description is continued in the case where the communication ID “ 01   aa ” of the communication start requesting source terminal  10   aa , whose accepting time is the earliest, is read from the waiting information management table shown in  FIG. 7B  in step S 24 - 3 . It should be noted that, in this case, due to the process of step S 24 - 4 , the waiting information management table moves to a state as shown in Table 1. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 COMMUNICATION- 
                   
                   
               
               
                   
                 START- 
               
               
                 DESTINATION 
                 REQUESTING- 
               
               
                 COMMUNICA- 
                 SOURCE 
                 ACCEPT- 
                 CONNECTION 
               
               
                 TION 
                 COMMUNICATION 
                 ING 
                 TYPE 
               
               
                 ID 
                 ID 
                 TIME 
                 INFORMATION 
               
               
                   
               
             
            
               
                 01db 
                 01ab 
                 10:32 
                 Normal 
               
               
                   
               
            
           
         
       
     
     Next, the session control unit  58  selects a relay apparatus  30  which relays image data and audio data between the terminal  10   aa  identified by the communication ID “ 01   aa ” read in step S 24 - 3  and the corresponding destination terminal  10   db  (step S 25 ). As a method for selecting the relay apparatus  30 , a known method is used, including a selection method based on loads of the relay apparatuses  30 , a selection method based on the location information of the terminals ( 10   aa ,  10   db ), or the like. In the following, the description will be continued in the case where the relay apparatus  30   e  is selected in step S 25 . 
     The sending and receiving unit  51  of the management system  50  sends relay apparatus connecting information for connecting the selected relay apparatus  30   e  to the communication start requesting source terminal  10   aa  (step S 26 ). In the relay apparatus connecting information, an IP address of the relay apparatus  30   e , authentication information, a port number, a session ID of a session for sending content data between the terminals ( 10   aa ,  10   db ), etc., can be included. Further, the sending and receiving unit  51  of the management system  50  sends to the destination terminal  10   db  communication start requesting information for requesting start of the communication between the terminals ( 10   aa ,  10   db ) and the relay apparatus connecting information for connecting to the relay apparatus  30   e  (step S 27 ). 
     The sending and receiving unit  11  of the terminal  10   aa  is connected to the relay apparatus  30   e  by transmitting the relay apparatus connecting information to the relay apparatus  30   e  (step S 28 ). 
     When the terminal  10   aa  is connected to the relay apparatus  30   e , the sending and receiving unit  11  transmits image data based on an image taken by the camera  112  of the terminal  10   aa  and audio data based on sound collected by the mike  114 , and requests for image data and audio data transmitted by the communication destination terminal  10   db.    
     The sending and receiving unit  11  of the terminal  10   db  is connected to the relay apparatus  30   e  by transmitting to the relay apparatus  30   e  the relay apparatus connecting information transmitted from the management system  50  (step S 29 ). When the terminal  10   db  is connected to the relay apparatus  30   e , the sending and receiving unit  11  transmits image data based on an image taken by the camera  112  of the terminal  10   db  and audio data based on a sound collected by the mike  114 , and requests for image data and audio data transmitted by the communication destination terminal  10   aa.    
     When terminals ( 10   aa ,  10   db ) are connected to the relay apparatus  30   e , a session between the terminals ( 10   aa ,  10   db ) is established. The relay apparatus  30   e  transmits the image data and the audio data transmitted from one of the terminals ( 10   aa ,  10   db ) to the other of the terminals ( 10   db ,  10   aa ). With the above process, it becomes possible for the terminals ( 10   aa ,  10   db ) to transmit the image data and the audio data to each other. 
     Next, referring to  FIG. 10 , a process will be described in which, after the communication of the terminal  10   aa  is disconnected due to an error of the communication network  2 , the terminal  10   aa  is reconnected.  FIG. 10  is a sequence diagram illustrating a process of reconnecting the terminal  10 . 
     The session control unit  58  of the management system  50  measures a communication bandwidth of the communication network between the terminals ( 10   aa ,  10   db ) after the communication is established between the terminals ( 10   aa ,  10   db ) in the management system  50 . A known method is used for measuring the communication bandwidth. In the case where time when the measured communication bandwidth is equal to zero Mbps exceeds a predetermined threshold, the session control unit  58  detects that the communication between the terminals ( 10   aa ,  10   db ) is disrupted due to a network error (step S 41 ). 
     When the above disruption is detected, the storing and reading unit  59  stores, in the waiting information management table, accepting time and connection type information which are associated with the communication ID “ 01   aa ” of the terminal  10   aa  which is a start requesting source of the disrupted communication and the communication ID “ 01   db ” of the communication destination terminal  10   db  (step S 42 ). With the above process, a request of the terminal  10   aa  for reconnection with the terminal  10   db  is accepted without having the request transmitted to the management system  50  by the terminal  10   aa . Here, as the accepting time, the time when the disrupted communication between the terminals ( 10   aa ,  10   db ) is detected by the session control unit  58  is recorded. Further, as the connection type information, “N/W Error” indicating a reconnection necessitated by a network error is recorded. Table 2 shows the waiting information management table updated by the process of step S 42 . 
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 COMMUNICATION- 
                   
                   
               
               
                   
                 START- 
               
               
                 DESTINATION 
                 REQUESTING- 
               
               
                 COMMUNICA- 
                 SOURCE 
                 ACCEPT- 
                 CONNECTION 
               
               
                 TION 
                 COMMUNICATION 
                 ING 
                 TYPE 
               
               
                 ID 
                 ID 
                 TIME 
                 INFORMATION 
               
               
                   
               
             
            
               
                 01db 
                 01ab 
                 10:32 
                 Normal 
               
               
                 01db 
                 01aa 
                 10:36 
                 N/W Error 
               
               
                   
               
            
           
         
       
     
     When the communication disruption is detected, the storing and reading unit  59  updates operation states associated with the communication IDs of the terminals ( 10   ac ,  10   db ) from “ONLINE (TALKING)” to “ONLINE” (step S 43 ). 
     When the operation state of the terminal  10   db  is updated to “ONLINE” and the terminal  10   db  moves to a state in which new communication can be started, the session control unit  58  of the management system  50  selects, according to processes a communication ID of a terminal  10  which should be connected to the terminal  10   db  from the communication IDs of the terminals  10  of the communication start requesting sources stored in the waiting information management table (step S 44 - 1  through S 44 - 4 , refer to  FIG. 9 ). 
     In this case, according to a process of step S 44 - 2 , the communication ID “ 01   aa ” of the communication start requesting source associated with the connection type information “N/W Error” is read from the waiting information management table of Table 2. In other words, a higher priority is given to the terminal  10   aa  waiting for reconnection after the network error than the terminal  10   ab  whose accepting time is the earliest, and the terminal  10   aa  is selected as a connecting destination for the terminal  10   db.    
     Subsequently, the terminals ( 10   aa ,  10   db ) are reconnected to each other according to the control of the management system  50 . Processes of the reconnection of the terminals ( 10   aa ,  10   db ) are similar to the processes of the above steps S 25  through S 29 , and thus, the description will be omitted (steps S 45  through S 49 ). 
     Modified Embodiment A 
     Next, a modified embodiment A is another embodiment of the present invention, and the difference from the above embodiment will be described. 
     In step S 42 , the storing and reading unit  59 , at the timing of storing the connection type information “N/W Error” in the waiting information management table, stores a number of times (number of disruptions) the communication of the terminals ( 10   aa ,  10   db ) is disrupted due to a network error before any one of the terminals ( 10   aa ,  10   db ) transmits a termination request, in an area of the memory unit  5000  different from the waiting information management table. 
       FIG. 11  is a flowchart illustrating a process of selecting a terminal  10  in the modified embodiment A. In the case where it is determined that the connection type information “N/W Error” is recorded in the waiting information management table (YES in step S 44 - 1 ), the session control unit  58  determines whether the number of disruptions stored in the memory unit  5000  is equal to or less than a predetermined threshold value (e.g., three times) (step S 44 -A). 
     In the case where it is determined that the number of disruptions is equal to or less than the predetermined threshold value, the storing and reading unit  59  selects and reads the communication ID “ 01   aa ” which is associated with the connection type information “N/W Error” of the communication IDs of the start requesting sources associated with the destination communication ID “ 01   db ” in the waiting information management table of Table 2 (step S 44 - 2 ). On the other hand, in the case where it is determined that the number of disruptions is more than the predetermined threshold value, the storing and reading unit  59  selects and reads the communication ID “ 01   ab ” whose accepting time is the earliest of the communication IDs of the start requesting sources associated with the destination communication ID “ 01   db ” in the waiting information management table of Table 2 (step S 44 - 3 ). In other words, when the number of disruptions of the communication of the terminal  10   aa  due to a network error exceeds the predetermined threshold value, a higher priority is no longer given to the terminal  10   aa  to be selected as a connection destination of the terminal  10   db . According to the modified embodiment A, it becomes possible to prevent from blocking for a long time the connection of another terminal  10   ab  which has been waiting for the start of communication with the terminal  10   db.    
     Modified Embodiment B 
     Next, a modified embodiment B is another embodiment of the present invention, and the difference from the above embodiments will be described. 
     In step S 42 , the storing and reading unit  59 , at the timing of storing the connection type information “N/W Error” in the waiting information management table, stores time when the disruption is detected (disruption time) in an area of the memory unit  5000  different from the waiting information management table. 
       FIG. 12  is a flowchart illustrating a process of selecting a terminal  10  in the modified embodiment B. In the case where it is determined that the connection type information “N/W Error” is recorded in the waiting information management table (YES in step S 44 - 1 ), the session control unit  58  determines whether time from the disruption time stored in the memory unit  5000  to the current time is equal to or less than a predetermined threshold value (e.g., three minutes) (step S 44 -B). 
     In the case where it is determined that the time is equal to or less than the predetermined threshold value, the storing and reading unit  59  reads the communication ID “ 01   aa ” which is associated with the connection type information “N/W Error” of the communication IDs of the start requesting sources associated with the destination communication ID “ 01   db ” in the waiting information management table of Table 2 (step S 44 - 2 ). On the other hand, in the case where it is determined that the time is greater than the predetermined threshold value, the storing and reading unit  59  selects and reads the communication ID “ 01   ab ” whose corresponding accepting time is the earliest of the communication IDs of the start requesting sources associated with the destination communication ID “ 01   db ” in the waiting information management table of Table 2 (step S 44 - 3 ). In other words, when the predetermined time elapses after the communication of the terminal  10   aa  is disconnected due to a network error, a higher priority is no longer given to the terminal  10   aa  to be selected as a connection destination of the terminal  10   db . According to the modified embodiment B, it becomes possible to prevent from blocking for a long time the connection of the terminal  10   ab  which has been waiting for a start of communication with the terminal  10   db  when the terminal  10   aa  is unable to reconnect for a long time. 
     Effect of Embodiment 
     When communication between the communication start requesting source terminal  10   aa  and the destination terminal  10   db  is disrupted, the waiting information management database (DB)  5012  of the management system  50  (an example of a management means) stores connection type information “N/W Error” (an example of specifying information) used for specifying the communication start requesting terminal  10   aa . When two or more terminals ( 10   aa ,  10   ab ) are requesting a start of communication with the above destination terminal  10   db , the session control  58  (an example of a selection means) selects from the terminals ( 10   aa ,  10   ab ) the terminal  10   aa  which should be connected to the destination terminal  10   db . With the above operations, after the communication between the terminals ( 10   aa ,  10   db ) is disrupted, it becomes possible to establish a reconnection between the terminals ( 10   aa ,  10   db ) before a call is provided for the terminal  10   ab  which has requested a start of communication beforehand. 
     It should be noted that in the management system  50 , the waiting information management database (DB)  5012  stores the connection type information “N/W Error” when the communication is disrupted before a communication terminating request is received. In the case where the terminals  10  are communicating with each other via a communication network  2  such as the Internet or a mobile telephone network, when the bandwidth becomes insufficient due to a network environment change, the communication may be disrupted unintentionally without a termination request from the terminals. According to the above embodiment, it becomes possible to give a higher priority of reconnection to the terminal  10  which has been disconnected unintentionally. 
     The waiting information management database (DB)  5012  stores the connection type information “N/W Error” associated with the communication ID (an example of identifying information) of the communication start requesting source terminal  10 . The session control unit  58  selects the terminal  10  which is identified by the communication ID associated with the connection type information “N/W Error” in the waiting information management database (DB)  5012  as the terminal  10  to be connected to the destination terminal  10 . With the above operations, the terminal  10  which should be reconnected can be easily identified. 
     According to the modified embodiment A, in the management system  50 , in the case where the number of communication disruptions before receiving the communication terminating request is equal to or less than the predetermined threshold value, the session control unit  58  selects the terminal  10  of two or more terminals  10  which should be connected to the destination terminal  10  based on the connection type information “N/W Error” stored in the waiting information management database (DB)  5012 . According to the modified embodiment A, it becomes possible to prevent from blocking for a long time the connection of the terminal  10   ab  which has been waiting for the start of communication with the terminal  10   db  when the terminal  10   aa  is repeatedly disconnected. 
     According to the modified embodiment B, in the case where the elapsed time after the communication is disrupted is less than the predetermined time, the session control unit  58  selects the terminal  10  of two or more terminals  10  which should be connected to the destination terminal  10  based on the connection type information “N/W Error” stored in the waiting information management database (DB)  5012 . According to the modified embodiment B, it becomes possible to prevent from blocking for a long time the connection of the terminal  10   ab  which has been waiting for a start of communication with the terminal  10   db  when the terminal  10   aa  is unable to reconnect for a long time. 
     The session control unit  58  (an example of a detection means) detects a disruption of the communication session between the terminals  10  based on a measurement result of the communication bandwidth between the terminals  10 . When the session control unit  58  detects the disruption, the waiting information management database (DB)  5012  stores the connection type information “N/W Error” used for specifying the terminal  10  which is a communication start requesting source. With the above operations, when communication is disrupted, the connection type information “N/W Error” can be automatically stored in the waiting information management database (DB)  5012 . 
     When the terminal  10  which should be connected is selected by the session control unit  58 , the management system  50  performs call control for connecting the selected terminal  10  with the destination terminal  10 . With the above operations, the management system  50  can establish a reconnection between the terminals  10  without receiving a reconnection request from the terminals  10 . 
     &lt;&lt;Supplementary Description of Embodiments&gt;&gt; 
     It should be noted that the management system  50  in the above embodiments may include a single computer, or include two or more computers to which corresponding units (functions or means) are arbitrarily assigned. 
     Further, a recording medium in which a terminal program, a relay apparatus program, and a communication management program of the communication system  1  are stored, an HD  204  in which the above programs are stored, and a program providing system  90  including the HD  204  can be provided as program products in the country or abroad. 
     In the communication system  1 , the “video conference” is used as a term which can be replaced by “TV conference”. 
     Further, in the above communication system  1 , as an example of the communication system  1 , a case of a video conference system has been described, but the case is not limited to it. The communication system  1  may be, for example, an audio conference system or a personal computer (PC) screen sharing system. Further, the communication system  1  may be a communication system of an Internet protocol (IP) telephone, an Internet phone, or a mobile telephone. In the above cases, for example, the terminal  10  corresponds to a phone such as a mobile telephone terminal. 
     Further, the management system  50  may connect, based on a request of a terminal  10 , etc., the destination terminal  10  with a terminal  10  which is different from the terminal  10  waiting for the reconnection according to the “N/W Error”. 
     The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on and claims the benefit of priority of Japanese Priority Application No. 2015-022901 filed on Feb. 9, 2015, the entire contents of which are hereby incorporated herein by reference.