JP6661362B2 - Control device, control method, communication system and program - Google Patents

Description

  The present invention relates to a control device, a control method, a communication system, and a program.

  In recent years, networking of projectors, cameras, printers, and the like has advanced, and the number of opportunities for performing data communication by directly connecting to an external network such as an Internet Protocol (IP) communication network has increased. Have been. That is, when directly connecting to an external network such as an IP communication network, a network device having security weakness such as a low firmware version can be attacked by a malicious third party such as a cracker. For example, a cracker may take control of the device with the vulnerability of the network device, which may cause a malfunction, failure, reception of inappropriate data, and the like.

  In Patent Document 1, as a method of updating firmware in a communication node, a download host device detects a communication node connected to its own station, divides each communication node into groups, and designates each communication node as a group. It is disclosed to download updated versions of firmware.

JP 2006-215803 A

  However, in a conventional communication system, there is a possibility that a communication node with low security connects to an external device. That is, the security of the communication system may not be sufficient.

  The present invention has been made in view of the above problems, and has as its object to provide a technique for improving the security of a communication system.

In order to achieve the above object, a control device according to one embodiment of the present invention has the following configuration. That is,
A control device in a communication system including a plurality of communication devices,
Collection means for collecting security information of the plurality of communication devices;
Selecting means for selecting one device based on security information of each of the plurality of communication devices;
Requesting means for requesting one device selected by the selecting means to receive predetermined data corresponding to each of the plurality of communication devices from an external device;
It is characterized by having.

  According to the present invention, it is possible to improve security of a communication system.

FIG. 1 is a diagram illustrating a configuration example of a communication system according to a first embodiment. FIG. 4 is a diagram illustrating a correspondence table between each node and a firmware version according to the first embodiment. FIG. 2 is a diagram illustrating an example of an internal configuration of a control node and a communication node according to the first embodiment. 5 is a flowchart illustrating a processing procedure of a control node according to the first embodiment. 5 is a flowchart illustrating a processing procedure of the communication node according to the first embodiment. 5 is a sequence chart showing a firmware download operation according to the first embodiment. FIG. 9 is a diagram illustrating a configuration example of a communication system according to a second embodiment. FIG. 13 is a diagram showing a correspondence table between each node according to the second embodiment, presence / absence of a proxy response function, and firmware version. FIG. 9 is a diagram illustrating an example of an internal configuration of a control node and a communication node according to the second embodiment. 5 is a sequence chart showing a firmware download operation according to the first embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. Note that the configurations shown in the following embodiments are merely examples, and the present invention is not limited to the illustrated configurations.

(First embodiment)
In this embodiment, among the nodes constituting the communication system, one node having a high security level is selected, the selected node downloads the firmware, and the downloaded firmware is transmitted to another node via the control node. An example of distribution will be described.

<Communication system configuration>
FIG. 1 is a diagram illustrating a configuration example of a communication system according to the first embodiment. The communication system 100 includes four communication nodes (communication devices) 101 to 104, a control node (control device) 105, and an AV Source 130. The AV Source 130 is an AV (Audio Video) content source connected to the control node 105. The control node 105 and the four communication nodes 101 to 104 constitute a network projector. Note that the AV Source 130 may be outside the system, and the number of communication nodes is not limited to four, but may be more or less than four.

  The communication system 100 has a configuration in which a multi-projection system using a network projector is used as an example.A control node 105 distributes AV (Audio Video) content to each network projector through a wireless LAN (Local Area Network) to display an image. I do. Here, when performing multi-projection using the wireless LAN, the access point function of the control node 105 is enabled, and the video is distributed to each of the communication nodes 101 to 104.

  In the communication system 100, each of the nodes 101 to 105 is configured by a local network, and is connected to an external network 120 via an AP (Access Point) 111 when performing firmware download or the like from the FWDL server 110. Here, the local network is defined as a network that is not connected to an outside line, including a wired or wireless network. Further, the external network 120 is defined as a network connected to an external line including a wired or wireless network such as an IP communication network, a public network, and a dedicated line.

  The external network 120 includes a person, such as a cracker 140, that invades the network and performs destruction or falsification. Therefore, when the firmware is downloaded, if a weak communication node among the nodes 101 to 105 in the communication system 100 connects to the external network 120, there is a possibility that the cracker 140 may take over. In the present embodiment, an attack from the cracker 140 is prevented by the control node 105 determining the nodes 101 to 105 to be connected to the external network 120 based on security information of each of the nodes 101 to 105, for example, security level information.

  Here, in describing the present invention, a network projector is assumed as the control node 105 and the communication nodes 101 to 104, but is not limited thereto. For example, a communication device having a network function such as a printer or a camera may be used. Also, the wireless LAN has been described as an example of the communication function, but the present invention is not limited to this, and a wired LAN communication system including a network router, a network hub, and the like may be used.

<Firmware version of each node>
Next, FIG. 2 is a correspondence table of each node and firmware version according to the first embodiment. The control node 105 has a function of collecting security level information of each of the communication nodes 101 to 104. When performing a firmware update of the entire system in the communication system 100, the control node 105 obtains security level information of each of the nodes 101 to 105. Here, the security level information is assumed to be firmware version information 200 for simplification.

  From the collected firmware version information 200, the control node 105 selects the communication nodes 104 as the communication nodes 101 to 105 having the highest security level as the substitute device for downloading the firmware. In addition, not only the node having the highest security level but also any one of nodes having a predetermined security level or higher may be selected. The communication node 104 connects to the FWDL server 110 registered in its own station as a specified connection destination via the AP 111, downloads firmware, and distributes the firmware to the other nodes 101 to 103 and 105.

  Here, the security level information is the firmware version information 200, but this is not a limitation. For example, the security level information is compatible with IPv6 (Internet Protocol Version 6) and the presence or absence of the IPsec (Security Architecture for the Internet Protocol) function. You may judge from. Furthermore, the connection destination reliability information stored in each communication node may be used, or a combination of these may be used. That is, the security level information is at least one of the version information of the firmware installed in the own device, the presence / absence of IPv6, the presence / absence of IPsec, or the reliability information of the connection destination stored in the own device. You may. Here, the reliability information of the connection destination may be information indicating whether or not encrypted communication such as SSL (Secure Sockets Layer) is possible.

<Node configuration>
FIG. 3 is a diagram illustrating an example of an internal configuration of the control node and the communication node according to the first embodiment. Reference numeral 300 denotes a node, which indicates one of the control node 105 and the communication nodes 101 to 104. The node 300 includes a communication unit 301, an external network connection unit 302, a proxy device selection unit 303, a security level collection unit 304, an address / data bus 305, a security level notification unit 306, a proxy operation notification unit 307, a memory 308, a processor 309, An AV data processing unit 310 and a projection unit 311 are provided.

  The processor 309 is used for controlling each functional block. The memory 308 is a memory space shared by each functional block. The address / data bus 305 is used for exchanging data between functional blocks. The communication unit 301 is a communication unit for AV data communication between each of the nodes 101 to 105 or with the AV source 130. The control node 105 and the communication nodes 101 to 104 store the AV data received by the communication unit 301 in the temporary memory 308, generate an image in the AV data processing unit 310, and project the image from the projection unit 311.

  The control node 105 distributes the AV data received from the AV Source 130 from the communication unit 301 to the other communication nodes 101 to 104. Furthermore, control data to each of the communication nodes 101 to 104 for performing multi-projection is also transmitted and received via the communication unit 301. Here, the communication unit 301 is configured by a wired LAN, a wireless LAN, or both. For connection to the AV Source 130, an interface such as HDMI (registered trademark) (High-Definition Multimedia Interface) or USB (Universal Serial Bus) may be provided in addition to the wired LAN and the wireless LAN.

  In the communication system 100, when executing the firmware update of all the nodes 101 to 105, the control node 105 generates a security level notification request by the security level collection unit 304, and the communication nodes 101 to 104 via the communication unit 301. Send to The communication nodes 101 to 104 that have received the security level notification request transmit the security level information such as the firmware version generated by the security level notification unit 306 to the control node 105.

  The control node 105 stores the security level information received for each of the nodes 101 to 105 in the memory 308. Next, the control node 105 refers to the security level information of each of the communication nodes 101 to 104 including its own station from the memory 308 by the proxy device selecting unit 303 and compares the communication node with the highest security level as a proxy device. select. In the example of FIG. 2, the communication node 104 is selected as a substitute device.

  Further, the control node 105 generates a proxy operation notification such as firmware download by the proxy operation notification unit 307, and transmits the proxy notification to the selected proxy device (communication node 104). The proxy device (communication node 104) that has received the proxy operation notification makes settings for connecting to the specified FWDL server 110 by the external network connection unit 302, and downloads firmware from the FWDL server 110 beyond the external network 120. The proxy device (communication node 104) distributes the downloaded firmware to each of the nodes 101 to 103 and 105.

  Here, it is assumed that the control node 105 and the communication nodes 101 to 104 configuring the communication system 100 may selectively mount only the functional blocks used in the internal block configuration 300. For example, the communication nodes 101 to 104 may not have the security level collection unit 304 and the proxy operation notification unit 307 used in the control node 105.

<Process of control node>
FIG. 4 is a flowchart illustrating a processing procedure of the control node according to the first embodiment. In S400, the security level collection unit 304 of the control node 105 transmits a security level information notification request to each of the communication nodes 101 to 104, and collects security level information from each of the communication nodes 101 to 104.

  In S401, the proxy device selection unit 303 of the control node 105 makes a comparison with reference to the security level information collected from each of the communication nodes 101 to 104 and the security level information of its own station. In S402, the proxy device selection unit 303 of the control node 105 determines a proxy device that is the node with the highest security level in the communication system 100 based on the comparison result in S401. In the example of FIG. 2, the proxy device is determined as the communication node 104.

  In S403, the proxy operation notification unit 307 of the control node 105 notifies the proxy device selected in S402 that the proxy device is connected to the FWDL server 110, which is the default connection destination, and performs a proxy operation of downloading firmware. Here, a series of proxy operations are stored in the communication nodes 101 to 104, and the proxy device may execute the stored operations in response to the proxy operation notification from the control node 105.

<Process of communication node>
FIG. 5 is a flowchart illustrating a processing procedure of the communication node according to the first embodiment. In S500, the security level notification units 306 of the communication nodes 101 to 104 notify the security level information of the own station to the control node 105.

  In S501, one of the communication nodes 101 to 104 receives the proxy operation notification from the control node 105. Here, it is assumed that the communication node 104 has received the proxy operation notification. The communication node 104 that has received the proxy operation notification recognizes that its own station has been selected as the proxy device. In S502, the communication unit 301 of the communication node 104 disconnects all connections in the local network with the other communication nodes 101 to 103 and the control node (015) in the communication system.

  In S503, the external network connection unit 302 of the communication node 104 connects to the external network 120 via the AP 111. In S504, the communication unit 301 of the communication node 104 downloads firmware from the FWDL server 110.

  In S505, after completing the download in S504, the external network connection unit 302 of the communication node 104 disconnects the connection with the AP 111, and the communication unit 301 of the communication node 104 reconnects to the local network of the communication system 100. That is, it reconnects with the control node 105 having the access point function. In S506, the communication unit 301 of the communication node 104 distributes the downloaded firmware to the control node 105 and the other communication nodes 101 to 103. Accordingly, when the proxy device has a function of maintaining connections with a plurality of networks at the same time, when connecting to an external network, communication with the local network is disconnected, and the security of the system during downloading can be further enhanced.

<Processing sequence>
FIG. 6 is a sequence chart showing a firmware download operation according to the first embodiment. In S600, the control node 105 requests notification of the security level information to each of the communication nodes 101 to 104, and in S601 to S604, each of the communication nodes 101 to 104 receives the notification. In S605 to S608, each of the communication nodes 101 to 104 transmits security level information.

  In S609, the control node 105 receives the security level information transmitted from each of the communication nodes 101 to 104. In S610, the control node 105 compares the security level information of its own station with the security level information of each of the communication nodes 101 to 104 collected in S609. In S611, the control node 105 selects a substitute device as a result of the comparison in S609. Here, the communication node 104 is selected as a substitute device.

  In S612, the control node 105 notifies the communication node 104 selected as the substitute device of an instruction to connect to the FWDL server 110 as a default connection destination and download the firmware. In S613, the communication node 104 receives the instruction, and thereby the communication node 104 recognizes that its own station has been selected as the substitute device.

  In S614, the communication node 104 disconnects the connection with the local network of the communication system 100 and connects with the FWDL server 110 over the external network 120. Although the sequence chart does not describe the AP 111, the connection with the FWDL server 110 is performed through the AP 111. In S615, the communication node 104 requests a firmware download to the FWDL server 110, and downloads the firmware in S616.

  In S617, after the completion of the firmware download in S616, the communication node 104 disconnects the connection with the FWDL server 110 and performs the connection with the local network of the communication system 100 again. In S618, the communication node 104 transmits the downloaded firmware to the control node 105. In S619, the control node 105 transmits the received firmware to each of the communication nodes 101 to 103 other than the communication node 104 (other than the communication device functioning as a substitute device). In S620 to S622, each of the communication nodes 101 to 103 receives the firmware transmitted from the control node 105.

  The firmware download method according to the first embodiment has been described above. When the firmware used by the control node 105 and the firmware used by the communication nodes 101 to 104 are different, the proxy device may be requested to perform a proxy download operation of the firmware.

  Further, in the communication system 100, the example in which the control node 105 controls the selection of the substitute device and the update operation of the firmware has been described, but the other communication nodes 101 to 104 that have received the operation from the user or received the notification have These controls may be performed.

  Furthermore, the control node 105 or each of the communication nodes 101 to 104 is not limited to connecting to the external network only at the time of downloading firmware, and may also connect at the time of obtaining network contents or uploading contents. That is, it goes without saying that the processing of the present embodiment is also applied to these situations.

  According to the present embodiment, when downloading a firmware in a communication system in which a plurality of communication nodes operate in conjunction with each other, it is possible to suppress communication nodes having a low security level from being connected to an external network, and thus perform a firmware update operation safely. It becomes possible.

(Second embodiment)
<Communication system configuration>
FIG. 7 is a diagram illustrating a configuration example of a communication system according to the second embodiment. As in the first embodiment, an operation of the communication system 700 including one control node 705 and a plurality of communication nodes 701 to 704 at the time of downloading firmware will be described.

  The difference from the communication system 100 of the first embodiment is that the control node 705 and the communication nodes 701 to 704 configuring the communication system 700 are each in a normal mode (operation with an external device) which is a mode at the time of operation with normal power consumption. This is a point that switching between a first mode that can be connected) and a standby mode (a second mode that cannot be connected to an external device) that is a mode at the time of power saving operation can be performed. In the normal mode, it is possible to connect to a connection destination via an external network, and in the standby mode, communication is possible in the communication system and power consumption is lower than in the normal mode.

  In the normal mode, each of the nodes 701 to 705 constituting the network projector can transmit and receive AV data and project an image in a multi-projection operation or the like.

  On the other hand, in the standby mode, each of the nodes 701 to 705 is, for example, in a state where only the communication unit 301 is activated. Note that a part of the processing unit other than the communication unit 301 may be operating, and may be any operation mode that consumes less power than the normal mode.

  In the standby mode, each of the nodes 701 to 705 checks the connection between the devices and transmits and receives status information of the devices. In the standby mode, communication I / Fs (Interfaces) such as a wireless LAN and a wired LAN in the communication unit 301 are used, and communication I / Fs such as BLE (Bluetooth Low Energy) that can communicate only with a local network are used. Only / F may be used.

  In the communication system 700 of FIG. 7, one node (the communication node 703 in this example) selected by the control node 705 operates in the normal mode, and the other nodes (the communication nodes 701, 702, and 704 in this example) 705) operates in a standby mode and has a system standby function. In the system standby state, it is possible to check the connection of the nodes 701 to 705 in the communication system 700 and make an inquiry about the status or the like by a tablet operated by the user or an application mounted on the nodes 701 to 705.

  In addition, in response to these inquiries, one normal mode communication node in the communication system 700 (the communication node 703 in this example) becomes the master station of the system standby, and another node (the communication node in this example) that replies to the inquiry. 701, 702, 704, and the control node 705).

  When downloading the firmware in the communication system 700, the control node 705 selects a communication node having the highest security level (for example, the communication node 703) among the nodes 701 to 705 having the proxy response function as a substitute device. Then, the proxy device downloads the firmware. Also, the communication node 703 serving as a substitute device becomes the master station of the system standby, switches the other nodes 701, 702, 704, and 705 to the standby mode, and then connects to the FWDL server 110. After downloading the firmware, the communication node 703 disconnects the connection with the external network 120, switches the other nodes 701, 702, 704, and 705 to the normal mode, and distributes the downloaded firmware.

  By performing such control, when the communication node 703 is connected to the external network 120, the risk that the other nodes 701, 702, 704, and 705 are accessed by crackers or the like is reduced, and the system has Safety can be improved. Further, the communication node 703 can connect to the external network 120 while maintaining the connection with the communication system 700.

<Response response function and firmware version of each node>
FIG. 8 is a diagram illustrating a correspondence table between each node according to the second embodiment, the presence / absence of the proxy response function 800, and the firmware version (security level 200). In the present embodiment, in the communication system 700, the control node 705 collects, from each of the communication nodes 701 to 704, information on the presence or absence of the proxy device function in addition to the security level information of each node. In each of the nodes 701 to 705, the nodes having the proxy response function are the control node 705, the communication node 702, and the communication node 703 in the example of FIG. The communication node 703 has the highest firmware version among these, and the communication node 703 is selected as a substitute device. Further, the communication node 703 can transmit a mode switching notification to the other nodes 701, 702, 704, and 705 as a master station in the system standby state. By making the selection in consideration of the presence or absence of the proxy response function, a node having a high security level but not having the proxy response function is not selected, so that re-execution of the process can be prevented.

<Node configuration>
FIG. 9 is a diagram illustrating an example of an internal configuration of a control node and a communication node according to the second embodiment. A node 900 indicates one of the control node 705 and the communication nodes 701 to 704. The node 900 further includes an operation mode switching unit 901 and a proxy response processing unit 902 in addition to the configuration of the node 300 described in FIG. 3 of the first embodiment.

  The operation mode switching unit 901 switches between a normal mode and a standby mode mounted on each of the nodes 701 to 705. More specifically, in response to a control notification from another node, all the functional blocks are activated in the normal mode, and a specific communication I / F (such as BLE) in the communication unit 301 is activated in the standby mode. ) Activates some functional blocks. Here, the communication unit 301 can perform simple communication processing such as transmission and reception of control packets between the nodes 701 to 705.

  When the communication system 700 is in the system standby state, the proxy response processing unit 902 causes the communication node 703 serving as a master station to make an inquiry to each of the other nodes 701, 702, 704, 705 from a tablet or the like operated by the user. On behalf of.

  Further, the communication unit 301 according to the second embodiment has a communication I / F with lower power consumption as compared with a wireless LAN such as BLE and a wired LAN that perform communication only within the communication system 700. And perform communication with the master station in the standby mode.

  Here, the control node 705 and the communication nodes 701 to 704 configuring the communication system 700 may include only functional blocks used in the internal block configuration 900. For example, the communication node 701 and the communication node 704 without the proxy response function do not include the proxy response processing unit 902.

<Processing sequence>
FIG. 10 is a sequence chart showing a firmware download operation according to the second embodiment. In S1000, the control node 705 requests each of the communication nodes 701 to 704, as node information, firmware version information and information indicating the presence or absence of the proxy response function. In S1001 to S1004, each of the communication nodes 701 to 704 receives a request for node information. In S1006 to S1009, each of the communication nodes 701 to 704 transmits node information.

  In S1009, the control node 705 receives the node information transmitted from each of the communication nodes 701 to 704. In S1010, the control node 705 compares the node information of its own station with the node information of each of the communication nodes 701 to 704 collected in S1009. As described above, the firmware versions of the nodes having the proxy response function (the communication nodes 702, 703, and the control node 705) are compared. In S1011, the control node 705 selects a substitute device as a result of the comparison in S1010. Here, as shown in FIG. 8, the communication node 703 having the proxy response function and having the highest firmware version is selected as the substitute device.

  In S1012, the control node 705 notifies the communication node 703 selected as the substitute device of an instruction to connect to the FWDL server 110, which is the default connection destination, and download the firmware. In S1013, the communication node 703 receives the notification, and recognizes that the own station has been selected as the substitute device. Further, it recognizes that its own station is the master station in the system standby mode in the communication system 700.

  In S1014, the communication node 703 transmits a standby mode transition notification to the control node 705 and the communication nodes 701, 702, 704. In steps S1015 to S1018, the nodes 701, 702, 704, and 705 that have received the standby transition notification transition to the standby mode in steps S1019 to S1022, respectively. By shifting a node other than the proxy device to the standby mode, it is possible to prevent an attack on the node from the external network.

  In S1023, the communication node 703 connects to the FWDL server 110 via the external network 120. In S1024, the communication node 703 requests the FWDL server 110 to download the firmware, and in S1025, downloads the firmware. In S1026, the communication node 703 disconnects the connection with the FWDL server 110 via the external network 120 after the firmware download in S1025 is completed.

  In S1027, the communication node 703 transmits a normal mode transition notification to the control node 705 and the communication nodes 701, 702, 704. In S1028 to S1031, the nodes 701, 702, 704, and 705 that have received the normal mode transition notification transition to the normal mode in S1032 to S1035. In S1036, the communication node 703 transmits the downloaded firmware to the control node 705. In S1037, the control node 705 transmits the firmware received from the communication node 703 to each of the communication nodes 701, 702, 704. In S1038 to S1040, each of the communication nodes 701, 702, and 704 receives the firmware transmitted from the control node 705.

  As described above, in the communication system 700 according to the second embodiment, the firmware can be downloaded in the system standby state while maintaining the connection with the local area in the communication node 703 serving as the substitute device.

(Other embodiments)
The present invention supplies a program for realizing one or more functions of the above-described embodiments to a system or an apparatus via a network or a storage medium, and one or more processors in a computer of the system or the apparatus read and execute the program. This processing can be realized. Further, it can also be realized by a circuit (for example, an ASIC) that realizes one or more functions.

  100: local network, 101 to 104: communication node, 105: control node, 110: FWDL server, 111: AP, 120: external network, 130: AV Source, 140: cracker, 303: proxy device selection unit, 304: security Level collection unit, 306: Security level notification unit

Claims (18)

A control device in a communication system including a plurality of communication devices,
Collection means for collecting security information of the plurality of communication devices;
Selecting means for selecting one device based on security information of each of the plurality of communication devices;
Requesting means for requesting one device selected by the selecting means to receive predetermined data corresponding to each of the plurality of communication devices from an external device;
A control device comprising:   The control device according to claim 1, wherein the request unit requests the one device selected by the selection unit to transmit the predetermined data to the control device. First receiving means for receiving the predetermined data from one device selected by the selecting means;
A first transmission unit that transmits the predetermined data received by the first reception unit to the plurality of communication devices other than the one device selected by the selection unit;
The control device according to claim 1 or 2, further comprising:   The selection unit selects one device from the plurality of communication devices and the control device based on security information of the control device and security information of each of the plurality of communication devices. The control device according to any one of claims 1 to 3, wherein The collecting means further collects information indicating the presence or absence of a function of responding to the inquiry to the other communication device on behalf of the other communication device from the plurality of communication devices,
The apparatus according to claim 1, wherein the selecting unit selects one device based on security information of the control device, security information of each of the plurality of communication devices, and information indicating presence or absence of the function. Item 5. The control device according to any one of Items 1 to 4 . The security information is at least one of version information of firmware installed in the own device, presence / absence of IPv6 installation, presence / absence of IPsec installation, and reliability information of a connection destination of the own device. Item 6. The control device according to any one of Items 1 to 5 . 7. The control device according to claim 6 , wherein the reliability information of the connection destination is information indicating whether or not encrypted communication is possible. The control device according to any one of claims 1 to 7 , wherein the predetermined data is firmware corresponding to each of the plurality of communication devices. Communication system including a control device and a plurality of communication apparatus according to any one of claims 1 8. The communication device,
Notifying means for notifying the control device of the security information of the own device,
Connection means for connecting to the external device in response to a request from the control device;
Second receiving means for receiving the predetermined data from the external device;
The communication system according to claim 9 , further comprising: The communication system according to claim 10 , further comprising a second transmission unit that transmits the predetermined data received by the second reception unit to the control device. Said notification means, communication system according to claim 10 or 11, wherein the notifying the security information in response to a request from the control device. The communication device,
In response to a request from the control device, a disconnecting unit that disconnects the connection with the control device and another communication device,
After the reception of the predetermined data is completed, reconnection means for reconnecting with the control device and another communication device,
The communication system according to any one of claims 8 to 12 , further comprising: The communication device,
Wherein the first mode and the external device connectable, according to any one of claims 8 to 13, further comprising a switching means for switching said second mode with an external device can not connect Communication system. The communication system according to claim 14 , wherein the second mode has lower power consumption than the first mode. The communication device,
16. The communication according to claim 14 , further comprising an instruction unit for instructing another communication device to switch from the first mode to the second mode when receiving the predetermined data. system. A control method of a control device in a communication system including a plurality of communication devices,
Collection means for collecting security information of the plurality of communication devices,
Selecting means for selecting one device based on security information of each of the plurality of communication devices;
Requesting means for requesting the one device selected in the selecting step to receive predetermined data corresponding to each of the plurality of communication devices from an external device;
A control method comprising: Program for operating a control device according to any one of the computer claims 1-8.

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