Patent Publication Number: US-9420226-B2

Title: Apparatus, system, and method of managing data transmission, and recording medium storing data transmission management program

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. §119 to Japanese Patent Application No. 2012-136801, filed on Jun. 18, 2012, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     The present invention generally relates to an apparatus, system, and method of managing data transmission, each of which is capable of determining whether to accept or reject a request for starting communication between or among a plurality of transmission terminals, and a data transmission management program stored in a non-transitory recording medium. 
     2. Description of the Related Art 
     With the need for reducing costs or times associated with business trips, more companies are moving towards data transmission systems provided with teleconference or videoconference (“conference”) capabilities to carry out communication among a plurality of transmission terminals. For example, the videoconference systems allow transmission of contents data such as image data and/or sound data among a plurality of videoconference terminals through a communications network such as the Internet to carry out videoconference. 
     When communication is managed using a management server, for example, as described in Japanese Patent Application Publication No. 2005-109922-A (Registration No. 4292544), the user cannot freely change the time to start or end, as the management server manages communication based on the scheduled information. 
     While the management server can allow the user to freely change the time to start or end the conference without requiring the user to change the scheduled information, for example, as described in Japanese Patent Application Publication No. 2011-199845-A, the management system may not be able to manage communication based on the scheduled information, as communication may not be based on the scheduled information. For example, the management system may start communication between a request transmission terminal and a counterpart transmission terminal in response to a request from the request transmission terminal, not based on the scheduled information. In such case, the counterpart transmission terminal, which starts communication with the request transmission terminal, may not be able to start communication with the other transmission terminal based on the scheduled information. 
     SUMMARY 
     In view of the above, one aspect of the present invention is to provide an apparatus, system, and a method, each of which is capable of determining whether to accept or reject a communication start request for starting communication between a first transmission terminal and a second transmission terminal, and a non-transitory recording medium storing the instructions which, when executed by a processor, cause the processor to perform the method. For example, the transmission management system obtains first reservation identification information for identifying communication reserved for the first transmission terminal and second reservation identification information for identifying communication reserved for the second transmission terminal, respectively, and determines whether to accept or reject the communication start request based on a match between the first reservation identification information and the second reservation identification information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein: 
         FIG. 1  is a schematic block diagram illustrating a configuration of a transmission system, according to an example embodiment of the present invention; 
         FIG. 2  is an illustration for explaining transmission or reception of data such as image data, sound data, or management data, performed by the transmission system of  FIG. 1 ; 
         FIG. 3  is a perspective view illustrating the outer appearance of a transmission terminal of the transmission system of  FIG. 1 ; 
         FIG. 4  is a schematic block diagram illustrating a hardware structure of the transmission terminal of  FIG. 1 ; 
         FIG. 5  is a schematic block diagram illustrating a hardware structure of any one of the transmission management system, relay device, program providing system, and maintenance system of the transmission system of  FIG. 1 ; 
         FIG. 6  is a schematic block diagram illustrating a functional structure of the transmission system of  FIG. 1 ; 
         FIG. 7  is an example data structure of a relay device management table, managed by the management system of  FIG. 6 ; 
         FIG. 8  is an example data structure of a terminal authentication management table, managed by the management system of  FIG. 6 ; 
         FIG. 9  is an example data structure of a terminal management table, managed by the management system of  FIG. 6 ; 
         FIG. 10  is an example data structure of a session management table, managed by the management system of  FIG. 6 ; 
         FIG. 11  is an example data structure of a reservation management table, managed by the management system of  FIG. 6 ; 
         FIG. 12  is a data sequence diagram illustrating operation of establishing communication among two or more terminals of the transmission system of  FIG. 1 , according to an example embodiment of the present invention; 
         FIG. 13  is an illustration of a reservation registration screen, displayed at the terminal of  FIG. 3 ; 
         FIG. 14  is a data sequence diagram illustrating operation of processing a request for starting communication with a counterpart terminal, performed by the transmission system of  FIG. 1 , according to an example embodiment of the present invention; 
         FIG. 15  is a flowchart illustrating operation of determining whether to accept or reject a communication start request, performed by the transmission management system of  FIG. 6 , according to an example embodiment of the present invention; 
         FIGS. 16A and 16B  are illustration of example screens having messages, generated by the management system of  FIG. 6 , according to an example embodiment of the present invention; 
         FIG. 17  is a flowchart illustrating operation of managing information regarding a session established between or among a plurality of transmission terminals, according to an example embodiment of the present invention; 
         FIG. 18  is a data sequence diagram illustrating operation of processing a request for ending communication with a counterpart terminal, performed by the transmission system of  FIG. 1 , according to an example embodiment of the present invention; and 
         FIG. 19  is an illustration for explaining candidate information, according to an example embodiment of the present invention. 
     
    
    
     The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     In describing example embodiments shown in the drawings, specific terminology is employed for the sake of clarity. However, the present disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. 
     In the following description, illustrative embodiments will be described with reference to acts and symbolic representations of operations (e.g., in the form of flowcharts) that may be implemented as program modules or functional processes including routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types and may be implemented using existing hardware at existing network elements or control nodes. Such existing hardware may include one or more Central Processing Units (CPUs), digital signal processors (DSPs), application-specific-integrated-circuits, field programmable gate arrays (FPGAs) computers or the like. These terms in general may be referred to as processors. 
     Unless specifically stated otherwise, or as is apparent from the discussion, terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical, electronic quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
       FIG. 1  is a schematic block diagram illustrating a transmission system, according to an example embodiment of the present invention.  FIG. 2  is an illustration for explaining transmission or reception of data such as image data, sound data, or management data, performed by the transmission system of  FIG. 1 . 
     In one example, the transmission system  1  functions as a data providing system that transmits contents data from one transmission terminal to another transmission terminal in one direction through a transmission management system  50 . In another example, the transmission system  1  functions as a two-way communication system that exchanges various information including image data and/or sound data between or among two or more of a plurality of transmission terminals  10  each of which functions as a communication terminal, through the transmission management system  50  that functions as a communication management system. When functioning as the communication system, the transmission system  1  may be implemented as a videoconference system, video teleconference system, voice conference system, voice teleconference system, or personal computer screen sharing system. 
     In the following examples, it is assumed that the transmission system  1  of  FIG. 1  is implemented as the videoconference system, which is one example structure of the communication system. Based on this assumption, the transmission management system  50  is implemented as the videoconference communication management system, which is one example structure of the communication management system. Further, the transmission terminal  10  is implemented as the videoconference communication terminal, which is one example structure of the communication terminal. However, the use of transmission system  1  is not limited to the following examples such that the transmission system  1  may be implemented as the transmission system or the communication system as described above. 
     The transmission system  1  of  FIG. 1  includes a plurality of transmission terminals  10   aa ,  10   ab ,  10   ba ,  10   bb ,  10   ca ,  10   cb ,  10   da , and  10   db , and a plurality of displays  120   aa ,  120   ab ,  120   ba ,  120   bb ,  120   ca ,  120   cb ,  120   da , and  120   db , a plurality of relay devices  30   a ,  30   b ,  30   c , and  30   d , a transmission management system  50 , a program providing system  90 , and a maintenance system  100 . 
     The transmission terminal  10  transmits or receives contents data such as image data and/or sound data to or from another transmission terminal  10 . In this example, it is assumed that a moving image is transmitted as the image data. Alternatively, a still image, or both of the still image and the moving image, may be transmitted as the image data. 
     For the descriptive purposes, in this example, any number of the plurality of terminals  10   aa  to  10   db  may be collectively or each referred to as the terminal  10 . Any number of the plurality of displays  120   aa  to  120   db  may be collectively or each referred to as the display  120 . Any number of the plurality of relay devices  30   a ,  30   b ,  30   c , and  30   d  may be collectively or each referred to as the relay device  30 . The transmission management system  50  may be referred to as the “management system”  50 . 
     The terminal  10  that transmits data to another terminal  10  to carry out videoconference may be referred to as the request terminal  10 . The terminal  10  that receives data from another terminal  10  to carry out videoconference may be referred to as the counterpart terminal  10 . For example, the request terminal  10  includes any terminal  10  that requests another terminal  10  to start videoconference, and the counterpart terminal  10  includes any terminal  10  that is associated with the request terminal  10  to start videoconference. 
     As illustrated in  FIG. 2 , in the transmission system  1 , the terminals  10  each establish a management data session “sei” with the management system  50  to start transmission and reception of various types of management data “M” with the management system  50 . Further, in this example, the terminals  10  each establish contents data sessions “sed” with the relay device  30  to transmit or receive contents data with the relay device  30 . The contents data sessions include at least one session “I” to transmit image data, and a session “V” to transmit sound data such as voice data. In this example, the contents data session may be referred to as the image and/or sound data session. 
     Referring back to  FIG. 1 , the terminal  10  transmits or receives contents data such as image data and sound data to or from a counterpart terminal  10  to establish communication with the counterpart terminal  10 . As described below, the terminal  10  transmits or receives image data in addition to sound data. Alternatively, the terminal  10  may transmit or receive only sound data. The relay device  30  relays contents data such as image data or sound data between or among the terminals  10 . For example, the relay device  30  may be implemented by a router or any device that provides the function of router. The management system  50  centrally manages various information regarding the terminal  10  or the relay device  30 . 
     The plurality of routers  70   a  to  70   d ,  70   ab , and  70   cd , which may be collectively or each referred to as the router  70 , selects a route that is most suitable for transmitting contents data such as image data and sound data. 
     The program providing system  90  includes a hard disk device (HD)  204  ( FIG. 5 ), which stores a terminal control program that causes the terminal  10  to perform various functions or operations. For example, the program providing system  90  sends the terminal control program to the terminal  10  through the Internet  2   i  to cause the terminal  10  to install the terminal control program. Further, the RD  204  of the program providing system  90  may store a relay control program that causes the relay device  30  to perform various functions or operations. For example, the program providing system  90  sends the relay control program to the relay device  30  through the Internet  2   i  to cause the relay device  30  to install the relay control program. Further, the RD  204  of the program providing system  90  may store a transmission management program that causes the management system  50  to perform various functions or operations. For example, the program providing system  90  sends the transmission management program to the management system  50  to cause the management system  50  to install the transmission management program. 
     The maintenance system  100  is implemented as one or more computers capable of maintaining, managing, fixing, or upgrading at least one of the terminal  10 , relay device  30 , management system  50 , and program providing system  90 . Assuming that the maintenance system  100  is provided within a country, and the terminal  10 , relay device  30 , management system  50 , and program providing system  90  are each installed outside the country, the maintenance system  100  maintains, manages, fixes, or upgrades at least one of the terminal  10 , relay device  30 , management system  50 , and program providing system  90 , remotely through the communications network  2 . The maintenance system  100  may manage maintenance of at least one of the terminal  10 , relay device  30 , management system  50 , and program providing system  90  without using the communications network  2 . For example, a machine type number, a manufacturing number, customer information, maintenance and repair information, and failure log information may be maintained at the maintenance system  100  without using the communications network  2 . 
     Still referring to  FIG. 1 , the terminals  10   aa  and  10   ab , the relay device  30   a , and the router  70   a  are connected to a local area network (LAN)  2   a . The terminals  10   ba  and  10   bb , the relay device  30   b , and the router  70   b  are connected to a LAN  2   b . The LAN  2   a  and the LAN  2   b  are connected to a leased line  2   ab  in which the router  70   ab  is provided. It is assumed that these devices including the terminals  10   aa  to  10   bb  are located in an area A. For example, assuming that the area is any area in Japan, the LAN  2   a  could be located within an office in a city such as Tokyo, and the LAN  2   b  could be located within an office in another city such as Osaka. 
     The terminals  10   ca  and  10   cb , the relay device  30   c , and the router  70   c  are connected to a LAN  2   c . The terminals  10   da  and  10   db , the relay device  30   d , and the router  70   d  are connected to a LAN  2   d . The LAN  2   c  and the LAN  2   d  are connected to a leased line  2   cd  in which the router  70   cd  is provided. It is assumed that these devices including the terminals  10   ca  to  10   db  are located in an area B apart from the area A. For example, assuming that the area is any area in the United States, the LAN  2   c  could be located within an office in a city such as New York, and the LAN  2   d  could be located within an office in another city such as Washington, D.C. The area A and the area B are connected through the Internet  2   i , via the routers  70   ab  and  70   cd.    
     The management system  50  and the program providing system  90  are connected through the Internet  2   i  to the terminal  10  and the relay device  30 . Any one of the management system  50  and the program providing system  90  may be located at any location within or outside any one of the area A and the area B. 
     In this example, the communications network  2  includes the LAN  2   a , LAN  2   b , leased line  2   ab , Internet  2   i , leased line  2   cd , LAN  2   c , and LAN  2   d . Any one or any portion of these lines or any other lines that may be included in the communications network  2  may be implemented as wired network or wireless network such as Wireless Fidelity (WiFi) network or Bluetooth (Registered Trademark) network. 
     As shown in  FIG. 1 , the terminal  10 , the relay device  30 , the management system  50 , the router  70 , the program providing system  90 , and the maintenance system  100  are each provided with four digit numbers. These four digit numbers separated by dots are the simple expressions of IP addresses respectively assigned to any one of the devices shown in  FIG. 1 , each of which has a function of communication device. For example, the IP address of the terminal  10   aa  is “1.2.1.3”. For simplicity, it is assumed that the IP address is expressed in IPv4. Alternatively, the IP address may be expressed in IPv6. 
     Further, in this example, the terminal  10  may be communicated in various ways. For example, at least two different terminals  10  that are located at different rooms in the same office, or at least two different terminals  10  that are located at different offices that are remotely located from one another, may communicate with one another. In another example, at least two different terminals  10  that are located in the same room may communicate with one another. In another example, one terminal  10  that is located indoor and another terminal  10  that is located outdoor, or at least two different terminals  10  that are both located outdoor, may communicate with one another. When the terminal  10  is located outdoor, the terminal  10  communicates with the other terminal  10  through a wireless network such as a wireless network designed for a mobile phone. 
     &lt;Hardware Structure of Transmission System&gt; 
     Referring now to  FIGS. 3 and 4 , a hardware structure of the terminal  10  is explained according to an example embodiment of the present invention.  FIG. 3  is a perspective view illustrating the outer appearance of the terminal  10 .  FIG. 4  is a schematic block diagram illustrating a hardware structure of the terminal  10 . In  FIG. 3 , the longitudinal direction of the terminal  10  is referred to as X direction. The direction orthogonal to the X direction, which is the horizontal direction of the terminal  10 , is referred to as the Y direction. The direction orthogonal to the X direction and the Y direction is referred to as the Z direction. 
     As illustrated in  FIG. 3 , the terminal  10  includes a body  1100 , an arm  1200 , and a camera housing  1300 . The body  1100  includes a backside wall  1110  having a plurality of air intake holes that are formed over the nearly entire surface of the intake surface of the backside wall  1110 . The body  1100  further includes a front sidewall  1120  provided with an exhaust surface  1121  having a plurality of exhaust holes over the nearly entire surface of the exhaust surface  1121 . When a cooling fan that is provided within the body  1100  is driven, air flows in through the intake holes of the intake surface and out through the exhaust holes of the exhaust surface  1121 . The body  1100  further includes a right side wall  1130  formed with a sound pickup hole  1131 . Through the sound pickup hole  1131 , a microphone  114  ( FIG. 4 ) of the terminal  10  is able to catch sounds such as human voice or any sound including noise. 
     The body  1100  has an operation panel  1150 , which is provided at a front surface toward the right side wall  1130 . The operation panel  1150  includes a plurality of operation keys  108   a  to  108   e  (“the operation key  108 ”), a power switch  109 , an alarm lamp  119 , and a plurality of sound output holes  1151 . Through the sound output holes  1151 , a speaker  115  ( FIG. 4 ) of the terminal  10  is able to output sounds such as sounds generated based on human voice. The body  1100  further includes a holder  1160 , which is provided at the front surface toward the left sidewall  1140 . The holder  1160 , which has a concave shape, accommodates therein the arm  1200  and the camera housing  1300 . The right side wall  1130  is further provided with a plurality of connection ports  1132   a  to  1132   c  (“connection ports  1132 ”). The connection ports  1132  allow electrical connection to an external device through an outside device connection I/F  118  ( FIG. 4 ). The body  1100  further includes a left sidewall  1140 , which is provided with a connection port to connect the external display  120  to the display I/F  117  through a cable  120   c.    
     The arm  1200  is fixed to the body  1100  via a torque hinge  1210 . With the torque hinge  1210 , the arm  1200  can be rotated in directions of up and down with respect to the body, while making a tilt angle θ 1  of up to 135 degrees.  FIG. 3  illustrates the case where the tilt angle θ 1  is 90 degrees. 
     The camera housing  1300  incorporates therein the camera  112  ( FIG. 4 ) that takes an image of an object. The object may be a part of a user, document, or a room where the terminal  10  is located. The camera housing  1300  is provided with a torque hinge  1310 . The camera housing  1300  is fixed to the arm  1200  through the torque hinge  1310 . With the torque hinge  1310 , the camera housing  1300  can be rotated with respect to the arm  1200 , in the direction of up, down, right, and left, such that the camera housing  1300  is kept at a desired position. More specifically, the camera housing  1300  can be rotated, while making a pan angle θ 2  from about −180 degrees to 180 degrees in the direction right and left, and a tilt angle θ 3  that ranges from about −45 degrees to +45 degrees in the direction of up and down. In  FIG. 3 , the pan angle θ 2  and the tilt angle θ 3  are each 0 degree. 
     The relay device  30 , the management system  50 , the program providing system  90 , and the maintenance system  100  are each implemented by a general-purpose computer such as a personal computer or a server computer. For simplicity, explanation of the outer appearance of the computer is omitted. 
     Referring to  FIG. 4 , the terminal  10  includes a central processing unit (CPU)  101 , a read only memory (ROM)  102 , a random access memory (RAM)  103 , a flash memory  104 , a solid state drive (SSD)  105 , a medium drive  107 , the operation key  108 , the power switch  109 , a network interface (I/F)  111 , the camera  112 , an imaging element interface (I/F)  113 , the microphone  114 , the speaker  115 , a sound input/output interface (I/O I/F)  116 , the display interface (I/F)  117 , the outside device connection interface (I/F)  118 , and an alarm lamp  119 , which are electrically connected through a bus  110  such as an address bus or data bus. The CPU  101  controls entire operation of the terminal  10 . The ROM  102  stores therein a control program for execution by the CPU  101 , such as an initial program loader (IPL). The RAM  103  functions as a work area of the CPU  101 . The flash memory  104  stores therein various data such as the terminal control program, image data, or sound data such as voice data. The SSD  105  controls reading or writing of various data with respect to the flash memory  104  under control of the CPU  101 . The medium drive  107  controls reading or writing of various data with respect to a removable recording medium  106  such as a flash memory. The operation key  108  allows the user to input a user instruction, for example, by allowing the user to select a communication destination such as the counterpart terminal  10 . The power switch  109  allows the user to switch on or off the power of the terminal  10 . The network I/F  111  allows the terminal  10  to transmit data through the communications network  2 . 
     The camera  112  takes an image of an object to obtain image data under control of the CPU  101 . The imaging element I/F  113  controls operation of the camera  112 . The microphone  114  catches sounds such as voice of the user at the terminal  10 . The speaker  115  outputs sounds such as sounds generated based on voice of the user at the counterpart terminal  10 . The sound I/O I/F  116  controls input or output of sound signals such as voice signals with respect to the microphone  114  and the speaker  115  under control of the CPU  101 . The display I/F  117  transmits image data to the display  120  under control of the CPU  101 . The outside device connection I/F  118  controls connection of the terminal  10  to various types of outside device. The alarm lamp  119  generates notification when an error is detected in the terminal  10 . 
     The display  120  may be implemented by a liquid crystal display (LCD) or an organic light emitting display, which displays various data such as an image of an object or an operation icon. As illustrated in  FIGS. 3 and 4 , the display  120  is connected to the display I/F  117  through the cable  120   c . The cable  120   c  may be implemented by an analog RCB (VGA) signal cable, a component video cable, a high-definition multimedia interface (HDMI) signal cable, or a digital video interactive (DVI) signal cable. 
     The camera  112  includes a plurality of devices such as a lens system, and a solid-state image sensing device that photo-electrically converts a light to generate an image of an object. For example, the solid-state image sensing device includes a complementary metal oxide semiconductor (CMOS) or a charge coupled device (CCD). 
     The outside device connection I/F  118  may be connected to an outside device such as an external camera, external microphone, or external speaker through a universal serial bus (USB) cable that is connected through the port  1132  of the body  1100  ( FIG. 3 ). When the external camera is connected to the terminal  10 , the CPU  101  causes the terminal  10  to capture an image using the external camera, rather than the camera  112  that is incorporated in the terminal  10 . When the external microphone or the external speaker is connected to the terminal  10 , the CPU  101  causes the terminal  10  to use the external microphone or the external speaker in replace of the incorporated microphone  114  or the incorporated speaker  115 . 
     The recording medium  106 , which can be freely attached to or detached from the terminal  10 , includes any desired type of recording medium. In alternative to the flash memory  104 , any nonvolatile memory that is readable and writable under control of the CUP  101  may be used such as Electrically Erasable and Programmable ROM (EEPROM). 
     In alternative to the outer appearance of  FIG. 3  or the hardware structure of  FIG. 4 , the terminal  10  may be implemented in various other ways. For example, the terminal  10  may be implemented by a desktop or a notebook computer. The camera or the microphone may be incorporated in the terminal  10  or connected to the terminal  10 . 
     The terminal control program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium  106  in any format that is installable or executable by a general-purpose computer. Once the terminal control program is written onto the recording medium, the recording medium may be distributed. Further, the terminal control program may be stored in any desired memory other than the flash memory  104 , such as the ROM  102 . 
       FIG. 5  illustrates a hardware structure of the management system  50  of  FIG. 1 . The management system  50  includes a CPU  201 , a ROM  202 , a RAM  203 , the HD  204 , a hard disk drive (HDD)  205 , a medium drive  207 , a display  208 , a network interface (I/F)  209 , a keyboard  211 , a mouse  212 , a CD-ROM drive  214 , and a clock  215 , which are electrically connected through a bus  210  such as an address bus or a data bus. 
     The CPU  201  controls entire operation of the management system  50 . The ROM  202  stores a control program for execution by the CPU  201 , such as an IPL. The RAM  203  functions as a work area of the CPU  201 . The HD  204  stores therein various data such as the transmission management program. The HDD  205  controls reading or writing of various data with respect to the HD  204  under control of the CPU  201 . The medium drive  207  controls reading or writing of various data with respect to a removable recording medium  206  such as a flash memory. The display  208  displays various data such as a cursor, menu, window, character, or image. The network I/F  209  allows the management system  50  to transmit data through the communications network  2 . The keyboard  211  includes a plurality of keys, each of which is used for inputting a user instruction through a character, a numeral, or a symbol. The mouse  212  allows the user to input a user instruction including, for example, selection or execution of a specific instruction, selection of an area to be processed, and instruction of cursor movement. The CD-ROM drive  214  controls reading or writing of various data with respect to a CD-ROM  213 . In alternative to the CD-ROM  213 , any removable recording medium may be used. The clock  215  may be implemented by an internal clock of the management system  50 , which is capable of counting a time period. 
     The transmission management program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium  206  or the CD-ROM  213  in any format that is installable or executable by a general-purpose computer. Once the transmission management program is written onto the recording medium, the recording medium may be distributed. Further, the transmission management program may be stored in any desired memory other than the HD  204 , such as the ROM  202 . 
     The relay device  30  is substantially similar in hardware structure to the management system  50  of  FIG. 5 , except for replacement of the management program with a relay device control program that is used for controlling the relay device  30 . The relay device control program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium  206  or the CD-ROM  213  in any format that is installable or executable by the general-purpose computer. Once the relay device control program is written onto the recording medium, the recording medium may be distributed. Further, the relay device control program may be stored in any desired memory other than the HD  204 , such as the ROM  202 . 
     The program providing system  90  is substantially similar in hardware structure to the management system  50  of  FIG. 5 , except for replacement of the management program with a program providing program that is used for controlling the program providing system  90 . The program providing program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium  206  or the CD-ROM  213  in any format that is installable or executable by the general-purpose computer. Once the program providing program is written onto the recording medium, the recording medium may be distributed. Further, the program providing program may be stored in any desired memory other than the HD  204 , such as the ROM  202 . 
     The maintenance system  100  is substantially similar in hardware structure to the management system  50  of  FIG. 5 , except for replacement of the management program with a maintenance program that is used for controlling the maintenance system  100 . The maintenance program may be written onto a recording medium that is readable by a general-purpose computer such as the recording medium  206  or the CD-ROM  213  in any format that is installable or executable by the general-purpose computer. Once the maintenance program is written onto the recording medium, the recording medium may be distributed. Further, the maintenance program may be stored in any desired memory other than the HD  204 , such as the ROM  202 . 
     Other examples of removable recording medium, which may be used in replace of the CD-ROM  213 , include, but not limited to, compact disc recordable (CD-R) disc, digital versatile disc (DVD), and blue ray disc. 
     &lt;Functional Structure of Transmission System&gt; 
     Next, a functional structure of the transmission system of  FIG. 1  is explained according to an example embodiment of the present invention.  FIG. 6  is a schematic block diagram illustrating functional structures of the transmission system  1 . As illustrated in  FIG. 6 , the terminal  10 , the relay device  30 , and the management system  50  exchange data with one another through the communications network  2 . In  FIG. 6 , the program providing system  90  and the maintenance system  100  of  FIG. 1  are omitted. 
     &lt;Functional Structure of Terminal&gt; 
     The terminal  10  includes a data transmitter/receiver  11 , an operation input  12 , a login request  13 , an imaging unit  14 , a sound input  15   a , a sound output  15   b , a display control  16 , and a memory control  19 . These units shown in  FIG. 6  correspond to a plurality of functions or functional modules, which are executed according to an instruction of the CPU  101  ( FIG. 4 ) that is generated according to the terminal control program being loaded from the flash memory  104  onto the RAM  103 . The terminal  10  further includes a memory  1000  that may be implemented by the flash memory  104  and the RAM  103  of  FIG. 4 . 
     Referring now to  FIGS. 4 and 6 , a functional structure of the terminal  10  is explained according to an example embodiment of the present invention. More specifically, in this example, the operations or functions that are performed by the terminal  10 , which include the operations or functions performed by the units shown in  FIG. 6 , are performed in relation to one or more hardware devices of the terminal  10  that are shown in  FIG. 4 . 
     The data transmitter/receiver  11 , which may be implemented by the network OF  111  ( FIG. 4 ) under control of the CPU  101 , transmits or receives various data or information to or from another terminal, device, or system, through the communications network  2 . In this example, the data transmitter/receiver  11  starts receiving the operation state information that indicates the operation state of each candidate counterpart terminal  10  from the management system  50 , before starting communication with any counterpart terminal  10 . The operation state of the candidate terminal  10  indicates whether the candidate terminal  10  is online or offline. When the terminal  10  is online, the operation state of the candidate terminal  10  further indicates whether the candidate terminal  10  is available for communication (“communication OK”), the candidate terminal  10  is having communication with the other terminal (“communicating”), or the candidate terminal  10  is not available as the user leaves the seat. The operation state of the candidate terminal  10  may further indicate whether the candidate terminal  10  is online but in trouble or error (“online, communicating, trouble”), the candidate terminal  10  is online but not capable of outputting image data such that only sound data is output, or the candidate terminal  10  is online but in mute state (“online, mute”) such that sound data is not output. For example, when the cable  120   c  is disconnected from the terminal  10 , the operation state of the candidate terminal  10  is assumed to be in the trouble state. For the descriptive purposes, in the following examples, it is assumed that the operation state information indicates whether the candidate terminal  10  is online (“online”) or offline (“offline”), and if online, whether the candidate terminal  10  is communicating (“communicating”). 
     The operation input  12  receives a user instruction input by the user through the operation key  108  or the power switch  109  ( FIG. 4 ), under control of the instructions received from the CPU  101 . For example, when the user selects “ON” using the power switch  109 , the operation input  12  receives a user instruction for turning the power on, and causes the terminal  10  to turn on the power. 
     The operations or functions of the login request  13  are performed according to an instruction received from the CPU  101  ( FIG. 4 ). When the power of the terminal  10  is turned on, the login request  13  automatically causes the data transmitter/receiver  11  to send login request information that requests the login process, and a current IP address of the terminal  10 , to the management system  50  through the communications network  2 . When the power of the terminal  10  is turned off according to a user instruction received from the user through the power switch  109 , the login request  13  causes the data transmitter/receiver  11  to send current operation state information of the terminal  10  to the management system  50 , which indicates that the power of the terminal  10  is turned of After the operation state information is sent, the operation input  12  turns off the power of the terminal  10 . As the operation state information of the terminal  10  is sent every time the power is turned off, the management system  50  is able to know that the terminal  10  is offline in realtime. 
     The operations or functions of the imaging unit  14  of the terminal  10  are performed by the camera  112  and the imaging element I/F  113  according to an instruction received from the CPU  101  ( FIG. 4 ). The imaging unit  14  takes an image of an object to output image data of the object. 
     The operations or functions of the sound input  15   a  of the terminal  10  are performed by the sound I/O I/F  116  according to an instruction received from the CPU  101 , in cooperation with the microphone  114 . After the microphone  114  converts sounds of the user at the terminal  10  to a sound signal, the sound input  15   a  inputs the sound signal in the form of sound data for further processing. The operations or functions of the sound output  15   b  of the terminal  10  are performed by the sound I/O I/F  116  according to an instruction received from the CPU  101 , in cooperation with the speaker  115 . The sound output  15   b  outputs a sound signal of sound data that is received from the counterpart terminal  10  through the speaker  115 . 
     The operations or functions of the display control  16  of the terminal  10  are performed by the display I/F  117  according to an instruction received from the CPU  101  ( FIG. 4 ). The display control  16  controls transmit of image data, which is generated based on image data received from the counterpart terminal  10 , to the display  120 . 
     The memory control  19  is implemented by the SSD  105  of  FIG. 4  according to an instruction received from the CPU  101 . The memory control  19  stores various data in the memory  1000 , or reads out various data from the memory  1000 . The memory  1000  stores therein various data such as terminal identification (ID) information for identifying the terminal  10 , and a password for authenticating a user at the terminal  10 . The memory  1000  further stores therein image data and/or sound data that is received as the terminal  10  communicates with a counterpart terminal  10  such that the image data and/or sound data are overwritten. Before the image data is overwritten, an image generated based on the image data is displayed onto the display  120 . Before the sound data is output, sounds generated based on the sound data is output through the speaker  150 . 
     In this example, any one of the terminal ID of the terminal  10  and the relay device ID of the relay device  30  includes any type of identification information that can be expressed by any language, character, symbol, mark, or any combination of language, character, symbol, and mark. 
     &lt;Functional Structure of Relay Device&gt; 
     Now, a functional structure of the relay device  30  is explained. The relay device  30  includes a data transmitter/receiver  31 , a relay unit  32 , and a memory control  39 . These units shown in  FIG. 6  correspond to a plurality of functions or functional modules, which are executed according to an instruction of the CPU  201  ( FIG. 5 ) that is generated according to the relay device control program being loaded from the HD  204  onto the RAM  203 . The relay device  30  further includes a memory  3000  that may be implemented by the RAM  203  and/or the HD  204  ( FIG. 5 ). 
     (Functional Structure of Relay Device) 
     Next, a functional structure of the relay device  30  is explained according to an example embodiment of the present invention. More specifically, in this example, the operations or functions that are performed by the relay device  30 , which include the operations or functions performed by the units shown in  FIG. 6  are performed in cooperation with one or more hardware devices of the relay device  30  that are shown in  FIG. 5 . 
     The data transmitter/receiver  31 , which may be implemented by the network I/F  209  ( FIG. 5 ), transmits or receives various data or information to or from another terminal, device, or system, through the communications network  2 , under control of instructions received from the CPU  201 . 
     The relay unit  32 , which may be implemented by instructions received from the CPU  201  ( FIG. 5 ), relays contents data between or among the terminals  10  through the data transmitter/receiver  31 , in the contents data session “sed”. 
     The memory control  39  is implemented by the HDD  205  of  FIG. 5  according to an instruction received from the CPU  201 . The memory control  39  stores various data in the memory  3000 , or reads out various data from the memory  3000 . 
     &lt;Functional Structure of Management System&gt; 
     The management system  50  includes a data transmitter/receiver  51 , a terminal authenticator  52 , a state manager  53 , a relay device selector  56 , a session manager  57 , a memory control  59 , a reservation extractor  61 , a reservation determiner  62 , and a generator  63 . These units shown in  FIG. 6  correspond to a plurality of functions or functional modules, which are executed according to an instruction of the CPU  201  ( FIG. 5 ) that is generated according to the transmission management program being loaded from the RD  204  onto the RAM  203 . The management system  50  further includes a memory  5000 , which may be implemented by the HD  204  ( FIG. 5 ). 
     (Relay Device Management Table) 
     The memory  5000  includes a relay device management database (DB)  5001 , which stores therein a relay device management table of  FIG. 7 . The relay device management table of  FIG. 7  stores the IP address of the relay device  30  for each relay device ID of the relay device  30 . For example, for the relay device  30   a  having the relay terminal ID “111a”, the relay device management table of  FIG. 7  indicates that the IP address of the relay device  30   a  is “1.2.1.2”. 
     (Terminal Authentication Management Table) 
     The memory  5000  further includes a terminal authentication management database (DB)  5002 , which stores a terminal authentication management table of  FIG. 8 . The terminal authentication management table of  FIG. 8  stores a plurality of terminal IDs respectively assigned to the terminals  10  that are managed by the management system  50 , in association with a plurality of passwords that are previously determined for the respective terminals  10 . For example, referring to the terminal authentication management table of  FIG. 8 , the terminal  10   aa  having the terminal ID “01aa” is assigned with the password “aaaa”. 
     (Terminal Management Table) 
     The memory  5000  further includes a terminal management database (DB)  5003 , which stores a terminal management table of  FIG. 9 . The terminal management table of  FIG. 9  stores, for each one of the terminal IDs assigned to the terminals  10 , the terminal name to be used for communication with the terminal  10 , the operation state of the terminal  10 , and the IP address of the terminal  10 . For example, for the terminal  10   aa  having the terminal ID “01aa”, the terminal management table of  FIG. 9  indicates that the terminal name is “Japan Tokyo Office AA terminal”, the operation state is online (“ONLINE”), and the IP address of the terminal  10   aa  is “1.2.1.3”. 
     (Session Management Table) 
     The memory  5000  further includes a session management database (DB)  5005 , which stores a session management table of  FIG. 10 . The session management table of  FIG. 10  stores information regarding each of the sessions that are currently carried out by at least two terminals  10  of the transmission system  1 . More specifically, for each session ID that uniquely identifies each contents data session “sed” being carried, the session management table of  FIG. 10  stores a reservation ID that identifies a reserved conference that corresponds to the contents data session “sed”, a relay device ID of the relay device  30  that transmits or receives contents data such as image data and sound data through the contents data session “sed”, a terminal ID of each one of the terminals  10  currently participating in the contents data session “sed”. For example, referring to the session management table of  FIG. 10 , the contents data session having the session ID “se03” is a session to carry out a conference that is previously scheduled with the reservation ID “rsv08”, using the relay device  30  having the relay device ID “111c” that relays contents data between the terminal  10   ae  having the terminal ID “01ae” and the terminal  10   dc  having the terminal ID “01dc”. For any contents data session that is not established to carry out a reserved conference, the “reservation ID” field remains blank. 
     (Reservation Management Table) 
     The memory  5000  further stores a reservation management database (DB)  5009 , which stores a reservation management table of  FIG. 11 . The reservation management table of  FIG. 11  is used to manage various information regarding a conference that is previously scheduled as a reserved conference. The reservation management table of  FIG. 11  stores, for each of the reservation IDs that uniquely identifies a reserved conference, the date and time at which the reserved conference is scheduled to start, the date and time at which the reserved conference is scheduled to end, the conference name to be used for identifying the reserved conference, and the terminal ID of each one of the terminals  10  that are registered as the terminals  10  participating in the reserved conference. For example, referring to the reservation management table of  FIG. 11 , the conference assigned with the reservation ID “rsv03” is scheduled to start at “2011/11/10, 15:00 PM” and end at “2011/11/10, 17:00 PM”. The conference has the conference name “Security meeting”. The terminal IDs of the participating terminals  10  are “01ca” and “01db”. The reservation ID, the start date/time, the end date/time, the conference name, and the terminal ID of the reservation management table may be managed by the management system  50 , according to an instruction received through the terminal  10 , for example, by adding or deleting the contents in each data field through the memory control  59 . 
     (Functional Structure of Management System) 
     Next, a functional structure of the management system  50  is explained according to an example embodiment of the present invention. In this example, the operations or functions that are performed by the management system  50 , which include the operations or functions performed by the units shown in  FIG. 6 , are performed in relation to one or more hardware devices of the management system  50  that are shown in  FIG. 5 . 
     The data transmitter/receiver  51 , which may be implemented by the network I/F  209  ( FIG. 5 ) according to an instruction received from the CPU  201 , transmits or receives various data or information to or from another terminal, device, or system through the communications network  2 . More specifically, in one example, the data transmitter/receiver  51  functions as a connection controller, which transmits relay device connection information to the terminal  10  to control connection between the terminal  10  and the relay device  30 . In another example, the data transmitter/receiver  51  functions as a receiver, which receives communication start request information to accept a request to start communication between or among the terminals  10 . In another example, the data transmitter/receiver  51  functions as an output unit, which transmits response information indicating a response with respect to the communication start request, to the terminal  10 . 
     Under control of the CPU  201  ( FIG. 5 ), the terminal authenticator  52  obtains a terminal ID and a password from the login request information that is received from the data transmitter/receiver  51 . Using the terminal ID and the password as a search key, the terminal authenticator  52  searches the terminal authentication management DB  5002  ( FIG. 8 ) to determine whether the obtained set of terminal ID and password is registered. Based on the search result, the terminal authenticator  52  determines whether the user at the terminal  10  or the terminal  10  is allowed for access. 
     The state manager  53 , which operates according to an instruction received from the CPU  201  ( FIG. 5 ), manages the operation state of the terminal  10  such as the operation state of the request terminal  10  that sends the login request information, using the terminal management table stored in the terminal management DB  5003  ( FIG. 9 ). The terminal management DB  5003  stores therein the terminal ID of the terminal  10 , the operation state of the terminal  10 , and the IP address of the terminal  10 , in association with one another. For example, when the power of the terminal  10  is switched from the ON state to the OFF state according to a user instruction received through the power switch  109 , the state manager  53  receives the operation state information of the terminal  10  indicating that the terminal  10  is turned off, from the terminal  10 . Based on the operation state information of the terminal  10 , the state manager  53  changes the operation state information of the terminal  10  that is stored in the terminal management DB  5003  from the on-line state to the off-line state. 
     The relay device selector  56 , which operates according to the instructions received from the CPU  201  ( FIG. 5 ), selects one of the relay devices  30  that is used to relay contents data between or among the plurality of terminals  10  through the contents data session “sed”. 
     The session manager  57 , which operates according to the instructions received from the CPU  201  ( FIG. 5 ), generates a session ID for identifying the contents data session “sed”, as the contents data session “sed” is newly established between or among the terminals  10 . The session manager  57  stores the session ID, the reservation ID that uniquely identifies the reserved conference on which the contents data session “sed” is based, and the terminal ID of each one of the terminals  10  participating in that session, in a corresponding manner, in the session management DB  5005  ( FIG. 10 ) of the memory  5000 . The session manager  57  further stores, for each session ID, the relay device ID of the relay device  30  that is selected by the relay device selector  56  as a relay device that relays contents data, in the session management DB  5005  ( FIG. 10 ). 
     The memory control  59  is implemented by the HDD  205  of  FIG. 5  according to an instruction received from the CPU  201 . The memory control  59  stores various data in the memory  5000 , or reads out various data from the memory  5000 . 
     The reservation extractor  61 , which operates according to the instructions received from the CPU  201  ( FIG. 5 ), searches the reservation management table stored in the reservation management DB ( FIG. 11 ) using a reservation ID obtained from the request terminal  10 , which requests for starting communication with the counterpart terminal  10 , to obtain the terminal ID of one or more terminals  10  that are stored in association with the reservation ID of the request terminal  10 . The reservation extractor  61  further searches the reservation management table stored in the reservation management DB ( FIG. 11 ) using a reservation ID obtained from the counterpart terminal  10  to obtain the terminal ID of one or more terminals  10  that are stored in association with the reservation ID of the counterpart terminal  10 . The reservation extractor  61  may further search the reservation management table ( FIG. 11 ) using the reservation ID as a search key to extract additional information regarding the reserved conference, such as the date/time at which the reserved conference is scheduled to start, the date/time at which the reserved conference is scheduled to end, and a name of the reserved conference. 
     The reservation determiner  62 , which operates according to the instructions received from the CPU  201  ( FIG. 5 ), determines whether the reservation ID associated with the request terminal  10 , which is extracted by the reservation extractor  61 , matches the reservation ID associated with the counterpart terminal  10 . The reservation determiner  62  further determines whether to accept or reject the communication start request, based on the determination result indicating whether the reservation IDs match between the request terminal  10  and the counterpart terminal  10 . 
     The generator  63 , which operates according to the instruction received from the CPU  201  ( FIG. 5 ), generates a message in response to the communication start request received from the terminal  10 . 
     &lt;Operation of Transmission System&gt; 
     Referring now to  FIGS. 12 and 13 , operation of transmitting or receiving various management data in preparation for communication by the terminal  10   aa , performed by the transmission system of  FIG. 1 , is explained according to an example embodiment of the present invention.  FIG. 12  is a data sequence diagram illustrating operation of registering a conference to be performed between or among the plurality of terminals  10 . In  FIG. 12 , the management data is transmitted or received through the management data session “sei” of FIG.  2 .  FIG. 15  is an illustration of an example registration screen to be displayed to the user at the request terminal  10   aa.    
     Referring to  FIG. 12 , at S 21 , the user at the request terminal  10   aa  turns on the power of the request terminal  10   aa  through the power switch  109  ( FIG. 4 ). The operation input  12  of the request terminal  10   aa  ( FIG. 6 ) turns on the power of the request terminal  10   aa.    
     At S 22 , as the power of the request terminal  10   aa  is turned on, the login request  13  of the request terminal  10   aa  automatically causes the data transmitter/receiver  11  to send the login request information that requests the login process to the management system  50  through the communications network  2 . The login request information includes a terminal ID that identifies the request terminal  10   aa , and a password associated with the terminal ID of the request terminal  10   aa . The terminal ID and the password may be obtained by the memory control  19  from the memory  1000 , and sent to the data transmitter/receiver  11 . At the time of sending the login request information from the request terminal  10   aa  to the management system  50 , the request terminal  10   aa  sends an IP address of the request terminal  10   aa  such that the management system  50  can obtain the IP address of the request terminal  10   aa.    
     At S 23 , the terminal authenticator  52  of the management system  50  searches the terminal authentication management table ( FIG. 8 ) stored in the memory  5000  using the terminal ID and the password of the login request information received through the data transmitter/receiver  51 , to determine whether the terminal ID and the password stored in the terminal authentication management table matches the terminal ID and the password of the login request information. When it is determined that the terminal ID and the password of the login request information matches the terminal ID and the password stored in the terminal authentication management DB  5002 , the terminal authenticator  52  determines that the terminal  10   aa  is authenticated. 
     At S 24 , when the terminal authenticator  52  authenticates that the login request information is received from the authenticated terminal  10 , the state manager  53  of the management system  50  stores the operation state and the IP address of the terminal  10   aa , with respect to the terminal ID and the terminal name of the terminal  10   aa  in the terminal management table ( FIG. 9 ) to create or update a record of the terminal  10   aa . Using the terminal management table of  FIG. 9 , which stores the operations state of online and the terminal IP address of “1.2.1.3” in association with the terminal ID “01aa” and the terminal name “AA Terminal”, various information regarding the terminal  10   aa  can be managed. 
     At S 25 , the data transmitter/receiver  51  of the management system  50  sends the authentication result obtained by the terminal authenticator  52  to the request terminal  10   aa  that has sent the login request information through the communications network  2 . As described above, in this example, it is assumed that the terminal authenticator  52  determines that the terminal  10   aa  is an authenticated terminal. 
     At S 26 , the display control  16  of the terminal  10   aa  displays a registration screen of  FIG. 13  on the display  120   aa . Through the registration screen, the user at the terminal  10   aa  inputs various information regarding a conference to be registered. The operation input  12  receives a user input including, for example, the conference name, the start date/time, the end date/time, and one or more terminals  10  that are scheduled to participate in the conference. 
     At S 27 , the data transmitter/receiver  11  of the terminal  10   aa  transmits conference reservation registration information (“reservation registration information”) to request for registering a conference, to the management system  50 . More specifically, the conference reservation registration information includes various information obtained through the user input, such as the conference name, the start date/time, the end date/time, and the terminal ID of each of the terminals  10  that are scheduled to participate in that conference. At S 28 , when the data transmitter/receiver  51  of the management system  50  receives the reservation registration information, the memory control  59  stores the received reservation registration information, such as the conference name, the start date/time, the end date/time, and the terminal IDs of the participating terminals  10 , in the registration management table of  FIG. 11 , in association with a reservation ID that identifies the reserved conference that is registered. In this example, the reservation ID may be generated at the management system  50  or at the terminal  10   aa , when registering the conference. For example, assuming that the user at the terminal  10   aa  inputs various information as illustrated in  FIG. 13 , the reservation management table of  FIG. 11  stores, for the reservation ID “rsv02”, the start date/time “2011/11/10 13:30”, the end date/time “2011/11/10 14:50”, the conference name “Strategy Meeting”, and the terminal IDs “01aa” “01ab” and “01db” that respectively correspond to the terminal  10   aa , the terminal  10   ab , and the terminal  10   db . The operation of registering the conference ends at S 28 . 
     Referring now to  FIG. 14 , operation of starting communication based on reservation, in response to a request received from the terminal  10   aa , performed by the communication system  1 , is explained according to an example embodiment of the present invention.  FIG. 14  is a data sequence diagram illustrating operation of starting communication between the terminal  10   aa  and the terminal  10   db . In  FIG. 14 , various management data is transmitted or received through a management data session “sei”. 
     In this example, the memory  1000  of the terminal  10   aa  stores a terminal name and a terminal ID for each one of one or more candidate counterpart terminals  10 . The display control  16  causes the display  120   aa  to display the terminal name of each one of the candidate counterpart terminals, which are stored in the memory  1000 . 
     As the user at the request terminal  10   aa  uses the operation key  108  of  FIG. 3  to select the terminal  10   db  as a counterpart terminal, at S 41 , the operation input  12  receives a user instruction for starting communication with the counterpart terminal  10   db.    
     At S 42 , the data transmitter/receiver  11  of the terminal  10   aa  transmits start request information, which requests starting of communication, to the management system  50 . The start request information includes the terminal ID “01aa” of the request terminal  10  that requests for starting communication, and the terminal ID “01db” of the counterpart terminal  10   db  that is selected by the request terminal  10   aa . The data transmitter/receiver  51  of the management system  50  receives the communication start request information (“communication start request”), which requests to start communication between the terminal  10   aa  and the terminal  10   db.    
     At S 43 , the management system  50 , which receives the communication start request, determines whether to accept the communication start request based on information regarding reservation of communication, as described below referring to  FIGS. 15 and 16 .  FIG. 15  is a flowchart illustrating operation of determining whether to accept a communication start request.  FIG. 16  is an illustration of example messages that may be generated by the generator  63 , in response to the communication start request. 
     Referring to  FIG. 15 , at S 43 - 1 , the reservation extractor  61  searches the reservation management table ( FIG. 11 ) using the terminal ID “01aa” of the request terminal  10   aa  as a search key to obtain the reservation ID of a reserved conference of the request terminal  10   aa , based on the start date/time of the reserved conference. In this example, the reservation extractor  61  obtains information regarding the current date/time based on the output of the clock  215  ( FIG. 5 ), and determines whether there is any reserved conference for the request terminal  10   aa  in the reservation management table ( FIG. 11 ) that is scheduled to start in less than five minutes, based on the start date/time of the reserved conference. Based on determination that there is at least one reserved conference that is scheduled to start in less than five minutes, the reservation extractor  61  extracts a reservation ID associated with the reserved conference that is scheduled to start in less than five minutes. By extracting information regarding the reserved conference that is scheduled to start in less than five minutes, the management system  50  may prevent the terminal  10  from starting communication that is not based on the reserved conference, just before the reserved conference is about to start. Alternatively, the reservation extractor  61  of the management system  50  may be programmed to start operation of determining whether there is any reserved conference that is scheduled to start soon at any desired time. For example, the reservation extractor  61  may extract the reserved conference, which is scheduled to start in less than 30 minutes. In another example, the reservation extractor  61  may extract the reserved conference, which is scheduled to start at any time on the same date. 
     At S 43 - 2 , the reservation extractor  61  searches the reservation management table 
     ( FIG. 11 ) using the terminal ID “01db” of the counterpart terminal  10   db  as a search key to extract a reservation ID of the counterpart terminal  10   db , which is associated with the reserved conference that is scheduled to start in less than 5 minutes, in a substantially similar manner as described above referring to S 43 - 1 . 
     At S 43 - 3 , the reservation determiner  62  determines whether the reservation ID is extracted, respectively, for the request terminal  10   aa  and the counterpart terminal  10   db , based on whether the reservation ID is extracted at S 43 - 1  and S 43 - 2 . When it is determined that the reservation ID is not extracted for each one of the request terminal  10   aa  and the counterpart terminal  10   db  (“NO” at S 43 - 3 ), the operation proceeds to S 43 - 4 . At S 43 - 4 , the reservation determiner  62  determines whether one of the reservation ID for the request terminal  10   aa  (extracted at S 43 - 1 ) or the reservation ID for the counterpart terminal  10   db  (extracted at S 43 - 2 ) is extracted. When it is determined that there is one of the reservation ID for the request terminal  10   aa  or the reservation ID for the counterpart terminal  10   db , which is extracted (“YES” at S 43 - 4 ), the operation proceeds to S 43 - 6 - 1 . At S 43 - 6 - 1 , the reservation determiner  62  determines to reject the communication start request, so that the user at one of the request terminal  10  or the counterpart terminal  10  having the reserved conference is able to start communication based on the reserved conference on time. 
     At S 43 - 9 - 1 , the generator  63  generates a message indicating that the communication start request is rejected. In one example, assuming that the reservation ID is extracted only for the counterpart terminal  10   db , the generator  63  may generate a message (A- 1 ) of  FIG. 16A  with the terminal name of the counterpart terminal  10   db  having the reserved conference. In another example, when the reservation ID is extracted only for the request terminal  10   aa , the generator  63  may generate a message (A- 2 ) of  FIG. 16A  with information regarding the reserved conference extracted for the request terminal  10   aa  such as the conference name, the start date/time, and the end date/time. In another example, when the reservation ID that is extracted for either one of the request terminal  10   aa  or the counterpart terminal  10   db  is associated with the reserved conference having the start date/time before the current date/time, the generator  63  further generates a message indicating a time period until the start date/time of the reserved conference, for example, as illustrated in (A- 3 ) and (A- 4 ) of  FIG. 16A . 
     Referring back to S 43 - 4 , when it is determined that there is no reservation ID for the request terminal  10   aa  or the counterpart terminal  10   db  (“NO” at S 43 - 4 ), the operation proceeds to S 43 - 6 - 2 . At S 43 - 6 - 2 , the reservation determiner  62  determines that there is no reserved conference for the request terminal  10   aa  or the counterpart terminal  10   db , and determines to accept the communication start request. 
     At S 43 - 9 - 2 , the generator  63  generates a message confirming that communication will be started with the counterpart terminal  10   db , for example, in response to the user selection of the “START” key, as illustrated in (B) of  FIG. 16B . 
     Referring back to S 43 - 3 , when it is determined that the reservation ID is extracted, respectively, for the request terminal  10   aa  and the counterpart terminal  10   db  (“YES” at S 43 - 3 ), the operation proceeds to S 43 - 5 . At S 43 - 5 , the reservation determiner  62  determines whether the reservation ID associated with the request terminal  10   aa  matches the reservation ID associated with the counterpart terminal  10   db . When it is determined that the reservation ID for the request terminal  10   aa  matches the reservation ID for the counterpart terminal  10   db (“YES” at S 43 - 5 ), the reservation determiner  62  determines that the request terminal  10   aa  and the counterpart terminal  10   db  are scheduled to participate in the same reserved conference, and the operation proceeds to S 43 - 6 - 3 . At S 43 - 6 - 3 , the reservation determiner  62  determines to accept the communication start request. 
     At S 43 - 9 - 3 , the generator  63  generates a message indicating that the communication can start, with the terminal name of the counterpart terminal  10   db , the conference name of the reserved conference, the start date/time, the end date/time, and the “START” key allowing the user to start communication, as illustrated in (C- 1 ) of  FIG. 16B . In another example, when the reservation IDs that are common to the request terminal  10   aa  and the counterpart terminal  10   db  are associated with the reserved conference having the start date/time before the current date/time, the generator  63  may further generate a message indicating a time period until the start date/time of the reserved conference, for example, as illustrated in (C- 2 ) of  FIG. 16B . 
     At S 43 - 5 , when it is determined that the reservation ID associated with the request terminal  10   aa  does not match the reservation ID associated with the counterpart terminal  10   db (“NO” at S 43 - 5 ), the operation proceeds to S 43 - 6 - 4 . At S 43 - 6 - 4 , the reservation determiner  62  determines to reject the communication start request, so that the user at one of the request terminal  10  or the counterpart terminal  10  having the reserved conference is able to start communication based on the reserved conference on time. 
     At S 43 - 9 - 5 , the generator  63  generates a message indicating that the communication start request is rejected, for example, as illustrated in (A- 2 ) of  FIG. 16A . More specifically, assuming that the request terminal  10   aa  has the reserved conference, the message includes the conference name of the reserved conference associated with the request terminal  10   aa , the start date/time, and the end date/time. When the reserved conference having the extracted reservation ID has the start date/time before the current date/time, the generator  63  may generate a message indicating a time period until the start date/time of the reserved conference, for example, as illustrated in (A- 4 ) of  FIG. 16A . 
     Referring back to  FIG. 14 , at S 44 , the data transmitter/receiver  51  of the management system  50  sends a response including the terminal ID “01aa” of the request terminal  10   aa , the terminal ID “01db” of the counterpart terminal  10   db , and the message generated at any one of S 43 - 9 - 1 , S 43 - 9 - 2 , S 43 - 9 - 3 , and S 43 - 9 - 5 . When the reservation ID associated with the request terminal  10   aa  and the reservation ID associated with the counterpart terminal  10   db  match (“YES” at S 43 - 5 ), the data transmitter/receiver  51  sends the response that further includes the reservation ID that is common to the request terminal  10   aa  and the counterpart terminal  10   db.    
     At S 45 , based on the response received from the management system  50 , the data transmitter/receiver  11  of the request terminal  10   aa  receives the response in response to the communication start request. The terminal  10   aa  causes the display control  16  to display the message included in the response on the display  120   aa , for example, as illustrated in  FIGS. 16A and 16B . 
     More specifically, in case the response indicates to reject the communication start request, as the user at the terminal  10   aa  selects the “OK” key in any one of the messages (A- 1 ), (A- 2 ), (A- 3 ), and (A- 4 ) of  FIG. 16A , the operation input  12  accepts confirmation from the user that the communication is not started. In case the response indicates to accept the communication start request, as the user at the terminal  10   aa  selects the “START” key in any one of the messages (B), (C- 1 ), and (C- 2 ) of  FIG. 16B , the operation input  12  accepts confirmation from the user that the communication is started. For the descriptive purposes, in this example, it is assumed that the operation input  12  accepts confirmation from the user that the communication is started. 
     At S 46 , the data transmitter/receiver  11  of the request terminal  10   aa  sends confirmation information to the management system  50 , which indicates that confirmation of the communication start request is received with the terminal ID “01aa” of the request terminal  10   aa  and the terminal ID “01db” of the counterpart terminal  10   db . When the reservation ID is received at S 44 , the data transmitter/receiver  11  transmits the confirmation information including the received reservation ID to the management system  50 . 
     At S 47 , based on the confirmation information, the data transmitter/receiver  51  of the management system  50  accepts confirmation from the request terminal  10   aa  to start communication. The state manager  53  of the management system  50  refers to the terminal management table ( FIG. 9 ) to specify a record associated with the terminal IDs “01aa” and “01db” of the terminals  10   aa  and  10   db , which are obtained from the confirmation information, and change the operation state “field” to “COMMUNICATING”. 
     At S 48 , the session manager  57  manages initiation of a contents data session “sed”, using the session management table ( FIG. 10 ). More specifically, the session manager  57  adds the terminal IDs “01aa” and “01db” of the terminals  10   aa  and  10   db , which start communication, to the session management table ( FIG. 10 ). 
     Referring now to  FIG. 17 , operation of managing information regarding a session, performed by the management system  50 , is explained according to an example embodiment of the present invention. 
     At S 48 - 1 , the session manager  57  determines whether the session management table ( FIG. 10 ) stores the reservation ID, which matches the reservation ID included in the confirmation information. In this example, when it is determined that the reservation ID is not included in the confirmation information, the session manager  57  determines that the reservation ID that matches the reservation ID of the confirmation information is not stored. When it is determined that the reservation ID that matches the reservation ID of the confirmation information is not stored (“NO” at S 48 - 1 ), the operation proceeds to S 48 - 2 . At S 48 - 2 , the session manager  57  generates a session ID for identifying a contents data session “sed” to be established to start communication based on reservation. 
     At S 48 - 3 , the relay device selector  56  selects the relay device  30 , which relays contents data to be transmitted or received between the terminals  10   aa  and  10   db  through the contents data session “sed”. More specifically, the relay device selector  56  arbitrarily selects a relay device ID from the relay device IDs stored in the relay device management table ( FIG. 7 ). 
     At S 48 - 4 , the session manager  57  stores the session ID generated at S 48 - 2 , the reservation ID included in the confirmation information, the relay device ID selected at S 48 - 3 , and the terminal IDs “10aa” and “10db” of the terminals  10   aa  and  10   db , in the session management table ( FIG. 10 ), in association with one another. 
     When it is determined that the reservation ID that matches the reservation ID of the confirmation information is stored (“YES” at S 48 - 1 ), the operation proceeds to S 48 - 5 . At S 48 - 5 , the session manager  57  specifies a record having the reservation ID of the confirmation information in the session management table ( FIG. 10 ), and adds the terminal IDs “01aa” and “01db” of the terminals  10   aa  and  10   db , in the terminal ID field of the specified record, such that the terminal IDs “01aa” and “01db” are stored in association with the reservation ID of the confirmation information. 
     At S 48 - 6 , the session manager  57  searches the session management table ( FIG. 10 ) using the reservation ID of the confirmation information as a search key to extract the session ID and the relay device ID that are stored for the reservation ID. 
     Referring back to  FIGS. 14 , at S 49 - 1  and S 49 - 2 , the data transmitter/receiver  51  of the management system  50  sends the relay device connection information, which is to be used for connecting the relay device  30 , respectively, to the terminals  10   aa  and  10   db . The relay device  30  may be selected at S 48 - 3  or extracted at S 48 - 6 . The relay device connection information includes, for example, the IP address of the relay device  30  that may be read from the relay device management table ( FIG. 7 ), authentication information, a port number, etc. The relay device connection information further includes the session ID generated at S 48 - 2  or extracted at S 48 - 6 . With the relay device connection information, the terminals  10   aa  and  10   db  are able to connect the relay device  30  to transmit or receive the contents data through the relay device  30 . 
     At S 50 , the data transmitter/receiver  51  of the management system  50  transmits the relay start request information that requests for starting relay for the request terminal  10   aa , to the relay device  30  selected at S 48 - 3  or extracted at S 48 - 6 . The relay start request information includes the IP addresses of the terminal  10   aa  and the terminal  10   db , and the session ID generated at S 48 - 2  or extracted at S 48 - 6 . The memory control  39  of the relay device  30  stores the received session ID, and the IP addresses of the terminals  10   aa  and  10   db in the memory  3000 . The relay unit  32  relays contents data transmitted from the request terminal  10   aa  to the terminal  10   db  via the data transmitter/receiver  31 , using the IP address of the terminal  10   db  stored in the memory  3000 . The relay unit  32  further relays contents data transmitted from the terminal  10   db  to the terminal  10   aa  via the data transmitter/receiver  31 , using the IP address of the terminal  10   aa  stored in the memory  3000 . More specifically, the contents data session “sed” is established between the terminal  10   aa  and the terminal  10   db  to exchange contents data. 
     Referring now to  FIG. 18 , operation of processing a request for leaving from the contents data session “sed” received from the request terminal  10   db , performed by the transmission system  1  of  FIG. 1 , is explained according to an example embodiment of the present invention. In this example, it is assumed that the request terminal  10   db  requests to leave from the contents data session “sed” after the contents data session “sed” is established among the terminals  10   aa ,  10   ab , and  10   db , to end the conference. In this example illustrated in  FIG. 18 , various management data is transmitted or received through the management data session “sei”. 
     At S 61 , as the user at the request terminal  10   db  presses the operation key  108  ( FIG. 4 ), the operation input  12  ( FIG. 6 ) of the request terminal  10   db  receives a user instruction for ending communication with the counterpart terminals  10   aa  and  10   ab . At S 62 , the data transmitter/receiver  11  of the request terminal  10   db  transmits the end request information to the management system  50 . The end request information includes the terminal ID “01db” of the request terminal  10   db , and the session ID identifying the contents data session “sed” from which the terminal  10   db  wants to leave. 
     At S 63 , the state manager  53  of the management system  50  specifies a record in the terminal management table ( FIG. 9 ) stored in the terminal management DB  5003 , which corresponds to the terminal ID “01db” of the request terminal  10   db  that is included in the end request information to manage the specified record. More specifically, the state manager  53  changes the operation state of the terminal  10   db  from “Communicating” to “Online”. 
     At S 64 , the session manager  57  of the management system  50  refers to the session management table ( FIG. 10 ) stored in the session management DB  5005  to delete the terminal ID “01db” of the request terminal  10   db , from the “Terminal ID” data field of the specified record. 
     In case all of the terminal IDs are deleted from the “Terminal ID” data field of the session management table, the session manager  57  extracts the reservation ID in the record associated with the terminal ID “01db”. At S 65 , the memory control  59  deletes the record having the reservation ID from the reservation management table ( FIG. 11 ). This results in deletion of the reservation information regarding the communication that ends, from the reservation management table. 
     At S 66 , the data transmitter/receiver  51  of the management system  50  transmits the end information including the IP address of the request terminal  10   db  and the session ID to the relay device  30 . 
     At S 66 , the memory control  39  of the relay device  30  deletes the IP address of the terminal  10   db , which is stored in the memory  3000  in association with the received session ID. With this deletion, the relay unit  32  stops relaying contents data, which may be received from the terminal  10   db , to the terminals  10   ab  and  10   aa , through the data transmitter/receiver  31 . The relay unit  32  further stops relaying contents data, which may be received from the terminal  10   ab  or  10   aa , to the terminal  10   db , through the data transmitter/receiver  31 . 
     Through operation of  FIG. 18 , the terminal  10   db  leaves from the contents data session “sed” to end communication with the terminals  10   aa  and  10   db.    
     In the above-described example, the reservation determiner  62  of the management system  50  determines whether the reservation ID associated with the request terminal  10  matches the reservation ID associated with the counterpart terminal  10 . When they do not match, the reservation determiner  62  determines to reject the communication start request, for example, as described above referring to S 43 - 6 - 4 . More specifically, the communication start request for starting communication between the request terminal and the counterpart terminal is rejected unless the communication to be started is based on the reserved conference that is common to the request terminal and the counterpart terminal. This prevents the counterpart terminal from accepting the communication stat request when the counterpart terminal is about to start communication based on the reserved conference. 
     In another example, the reservation determiner  62  of the management system  50  determines to accept the communication start request, when none of the reservation ID associated with the request terminal  10  and the reservation ID associated with the counterpart terminal  10  are extracted, for example, as described above referring to S 43 - 6 - 2 . When the communication start request, not based on the reserved conference, is received, the management system  50  is able to determine whether to accept or reject the communication start request. 
     Further, in this example, when it is determined to accept the communication start request, the data transmitter/receiver  51  of the management system  50  transmits the relay device connection information to the terminal  10 , so as to control connection between or among the terminals  10 . 
     Furthermore, the management system  50  manages the relay device ID for each one of a plurality of relay devices  30  relaying contents data through the contents data session “sed”, using the session management table ( FIG. 10 ). The data transmitter/receiver  51  of the management system  50  transmits the relay device connection information to the terminal  10 , which is used to connect the relay device  30  having the relay device ID extracted from the session management table ( FIG. 10 ). This allows the management system  50  to effectively control connections among the terminals  10 , even when there are more than two terminals  10  that are communicating based on the reserved conference. 
     Further, in this example, the reservation extractor  61  of the management system  50  extracts the reservation ID based on the start date/time and the end date/time of the reserved conference. This prevents the terminal  10  from starting communication not based on the reserved conference, when the terminal  10  is about to start communication based on the reserved conference. 
     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims. 
     Further, in any one of the above-described examples, any one of the terminals  10  may be identified using any information other than the terminal ID for identifying the terminal  10 , as long as each user who operates the terminal  10  can be identified. In one example, the terminal  10  may be identified using a user ID that uniquely identifies the user who operates the terminal  10 . In such case, at S 22  of  FIG. 12 , the management system  50  receives the login request information including the user  1 D and the password, from the terminal  10 . The management system  50  manages various information regarding the user, using the user ID. For example, the session management table of  FIG. 10  may store, for each session being carried out, the session ID, the reservation ID, the relay device ID, and one or more user IDs each identifying the user who is participating in the session using the terminal  10 . The reservation management table of  FIG. 11  may store, for each reserved conference that is registered, the start date/time, the end date/time, the conference name, and one or more user IDs each identifying the user who is scheduled to attend in the reserved conference. Through managing various information based on the user ID that uniquely identifies the user, the management system  50  is able to manage information by user even when one user is using more than one terminal  10  or even when one terminal  10  is shared by more than one user. 
     Furthermore, in any one of the above-described examples, the terminal  10  that requests for registration of a conference, and the terminal  10  that requests to start communication based on the reserved conference may be different. 
     Further, the relay device  30 , the management system  50 , the program providing system  90 , and the maintenance system  100  may be each implemented by a single computer. Alternatively, any number of parts, functions, or modules of the relay device  30 , the management system  50 , the program providing system  90 , and the maintenance system  100  may be classified into a desired number of groups to be carried out by a plurality of computers. In case the program providing system  90  is implemented by the single computer, the program to be provided by the program providing system  90  may be transmitted, one module by one module, after dividing into a plurality of modules, or may be transmitted at once. In case the program providing system  90  is implemented as a plurality of computers, each computer may transmit each module that is stored in its memory, after the program is divided into a plurality of modules. 
     A recording medium storing any one of the terminal control program, relay device control program, and transmission management program, or a storage device such as the HDD  204  that stores any one of the terminal control program, relay device control program, and transmission management program, or the program providing system  90  provided with the HD  204  storing any one of the terminal control program, relay device control program, and transmission management program, may be distributed within the country or to another country as a computer program product. 
     Further, in the above-described examples, the relay device  1 P address of the relay device  30  and the terminal IP address of the terminal  10  are respectively managed using the relay device management table of  FIG. 7  and the terminal management table of  FIG. 9 . Alternatively, the relay device  30  and the terminal  10  may each be managed using any other identification information or using any other tables. For example, when the relay device  30  or the terminal  10  needs to be identified on the communications network  2 , the relay device  30  or the terminal  10  may be managed using Fully Qualified Domain Name (FQDN). In such case, the transmission system  1  is provided with a domain name system (DNS) server that obtains the IP address that corresponds to the FQDN of the relay device  30  or the terminal  10 . In view of this, identification information for identifying the relay device  30  on the communications network  2  may not only include the identification information that identifies the relay device  30  on the communications network  2 , but also identification information that identifies a node on the communications network  2  to which the relay device  30  is connected, or identification information that identifies a node on the communications network  2  from which the relay device  30  is connected. Similarly, identification information for identifying the terminal  10  on the communications network  2  may not only include the identification information that identifies the terminal  10  on the communications network  2 , but also identification information that identifies a node on the communications network  2  to which the terminal  10  is connected, or identification information that identifies a node on the communications network  2  from which the terminal  10  is connected. 
     In the above-described examples, the transmission system  1  of  FIG. 1  is treated as a videoconference system. Alternatively, the transmission system  1  of  FIG. 1  may be implemented as a teleconference system such as the IP teleconference system or the Internet teleconference system. Alternatively, the transmission system  1  of  FIG. 1  may be implemented as a car navigation system. For example, the request terminal  10  may be implemented as a car navigation system that is installed onto an automobile. The counterpart terminal  10  may be implemented as a management terminal or server at a management center that manages the car navigation system or a car navigation system that is installed onto another automobile. Alternatively, the transmission system  1  may be implemented as a screen sharing system. 
     In another example, the transmission system  1  of  FIG. 1  may be implemented as a communication system having a portable phone. In such case, the terminal  10  is implemented as the portable phone. For example, as illustrated in  FIG. 19 , the terminal  10 , or the portable phone  310 , includes a body  310 - 1 , a menu screen display button  310 - 2 , a display section  310 - 3 , a microphone  310 - 4  provided at a lower portion of the body, and a speaker  310 - 5  provided at an upper portion of the body. When selected, the menu screen display button  310 - 2  causes the display section  310 - 3  to display a menu screen in which various icons each indicating a specific application program are displayed. In this example, the display section  310 - 3  displays a candidate terminal list that lists a plurality of terminal names together with a plurality of icons each reflecting the operation state of each candidate terminal. Since the terminal  10  in this example is implemented as a portable phone  310 , the name of a user who owns the specific terminal, or a nickname of the user, is displayed as the terminal name. The display section  310 - 3  is a touch panel screen, which allows the user to select one of the plurality of terminal names being displayed by the display section  310 - 3 . When a specific terminal name, or a user name, is selected, the portable phone  310  starts communication with the specific terminal that is selected in a substantially similar manner as described above. 
     Further, in the above-described examples, the transmission system  1  is implemented as a videoconference system for use at offices. Other examples of use of the transmission system  1  include, but not limited to, meetings, casual conversation among family members or friends, and distribution of information in one direction. 
     Further, any of the above-described devices or units can be implemented as a hardware apparatus, such as a special-purpose circuit or device, or as a hardware/software combination, such as a processor executing a software program. 
     The present invention can be implemented in any convenient form, for example using dedicated hardware, or a mixture of dedicated hardware and software. The present invention may be implemented as computer software implemented by one or more networked processing apparatuses. The network can comprise any conventional terrestrial or wireless communications network, such as the Internet. The processing apparatuses can compromise any suitably programmed apparatuses such as a general purpose computer, personal digital assistant, mobile telephone (such as a WAP or 3G-compliant phone) and so on. Since the present invention can be implemented as software, each and every aspect of the present invention thus encompasses computer software implementable on a programmable device. The computer software can be provided to the programmable device using any storage medium for storing processor readable code such as a floppy disk, hard disk, CD ROM, magnetic tape device or solid state memory device. 
     The hardware platform includes any desired kind of hardware resources including, for example, a central processing unit (CPU), a random access memory (RAM), and a hard disk drive (HDD). The CPU may be implemented by any desired kind of any desired number of processor. The RAM may be implemented by any desired kind of volatile or non-volatile memory. The HDD may be implemented by any desired kind of non-volatile memory capable of storing a large amount of data. The hardware resources may additionally include an input device, an output device, or a network device, depending on the type of the apparatus. Alternatively, the HDD may be provided outside of the apparatus as long as the HDD is accessible. In this example, the CPU, such as a cashe memory of the CPU, and the RAM may function as a physical memory or a primary memory of the apparatus, while the HDD may function as a secondary memory of the apparatus. 
     In one example, the present invention may reside in a transmission management system including: a receiver to receive a communication start request, which requests to start communication between a first transmission terminal and a second transmission terminal; a reservation obtainer to obtain first reservation identification information for identifying communication reserved for the first transmission terminal, and second reservation identification information for identifying communication reserved for the second transmission terminal; and a reservation determiner to accept the communication start request when the first reservation identification information matches the second reservation identification information, and to reject the communication start request when the first reservation identification information does not match the second reservation identification information. 
     For example, the receiver may correspond to the data transmitter/receiver  51  of the management system  50 , which may be implemented by the network I/F  209  which operates in cooperation with the CPU  201 . The reservation obtainer may correspond to the reservation extractor  61  of the management system  50 , which operates according to the instructions received from the CPU  201 . The reservation determiner corresponds to the reservation determiner  62 , which operates according to the instructions received from the CPU  201 . 
     More specifically, when the transmission system allows a request transmission terminal to start communication with a counterpart transmission terminal not based on reservation, in response to a communication start request received from the request transmission terminal, the counterpart transmission terminal may not be able to start communication based on reservation. In view of this, in one example, the reservation determiner  62  of the management system  50  rejects the communication start request, unless the reserved communication reserved for the request transmission terminal  10  matches the reserved communication reserved for the counterpart transmission terminal  10 . More specifically, the communication start request, which is not based on reservation that is common to the request transmission terminal  10  and the counterpart transmission terminal  10 , is rejected. This prevents the counterpart transmission terminal from not being able to start communication based on reservation due to communication not based on reservation. 
     The reservation determiner may further determine whether to accept or reject the communication start request, based on whether the first reservation identification information or the second reservation identification information is obtained. 
     More specifically, when the reservation IDs are not extracted for both of the request terminal and the counterpart terminal, the management system  50  is able to allow communication to be established between the request terminal and the counterpart terminal. When at least one of the reservation ID of the request terminal or the reservation ID of the counterpart terminal is extracted, the management system  50  prevents the request terminal or the counterpart terminal to start communication so as to allow the request terminal or the counterpart terminal to start communication based on reservation. 
     In one example, the transmission management system further includes a reservation manager to store reservation identification information for identifying specific communication reserved for one or more transmission terminals, in association with identification information of the one or more transmission terminals, to generate the reservation information. For example, the reservation manager corresponds to the reservation management DB  5009 , storing the reservation management table. 
     In another example, the transmission management system further includes a connection controller to control connection of a relay device that relays data to be transmitted or received between the first transmission terminal and the second transmission terminal, with respect to the first transmission terminal and the second transmission terminal, respectively, when the reservation determiner accepts the communication start request. For example, the connection controller corresponds to the data transmitter/receiver  51  of the management system  50 , which operates in cooperation with the CPU  201 . 
     In another example, the transmission management system may further include a relay device manager to store, for each one of a plurality of relay devices, relay device identification information for identifying the relay device. The connection controller selects one of the plurality of relay devices to relay data between the first transmission terminal and the second transmission terminal. For example, the relaying device manager corresponds to the relay device management DB  5001 . 
     In another example, the reservation manager further stores, for each one of the reservation identification information identifying the reserved communication, start time information indicating a time at which the reserved communication starts, and end time information indicating a time at which the reserved communication ends. The reservation obtainer obtains the reservation identification information based on the start time information and the end time information. 
     In another example, the present invention may reside in a transmission system including any one of the above-described transmission management system, and one or more transmission terminals. 
     In another example, the present invention may reside in a method of determining whether to accept a communication start request, the method including: receiving a communication start request, which requests to start communication between a first transmission terminal and a second transmission terminal; obtaining first reservation identification information for identifying communication reserved for the first transmission terminal, and second reservation identification information for identifying communication reserved for the second transmission terminal, respectively, using reservation information regarding communication reserved for at least the first transmission terminal and the second transmission terminal; and determining whether to accept or reject the communication start request based on a match between the first reservation identification information and the second reservation identification information. The determining accepts the communication start request when the first reservation identification information matches the second reservation identification information. The determining rejects the communication start request when the first reservation identification information does not match the second reservation identification information. 
     In another example, the present invention may reside in a non-transitory recording medium storing a plurality of instructions which, when executed by a processor, cause the processor to perform any one of the above-described methods.