Information processing apparatus, information processing terminal, distribution method, time synchronization method

Abstract

This technology relates to an information processing device, an information processing terminal, a distribution method, and a time synchronization method which make it possible to easily set an appropriate time synchronization method for each of multiple devices. An information processing device, according to one aspect of this technology, distributes, in response to a request from a client device, information representing a time synchronization strategy set as a method for time synchronization between client devices forming the same group. This technology is applicable to a server connected to a network.

Description

Technical Field

[0001] The present technology relates to an information processing apparatus, an information processing terminal, a distribution method, and a time synchronization method, and particularly relates to an information processing apparatus, an information processing terminal, a distribution method, and a time synchronization method that enable an appropriate time synchronization method to be easily set for each device.

Background Art

[0002] There is an application that captures the state inside a space with a plurality of cameras installed in a specific space such as a store and recognizes the behavior of people inside the space. In a system that realizes such an application, since images captured at the same time are used for recognition at each time, settings for synchronizing the times of the respective cameras are required.

[0003] Technical skills are required to appropriately perform settings for synchronizing the times of multiple devices.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since technical skills are required, it is difficult for ordinary users to appropriately perform settings for synchronizing times. It is costly to rely on people with specialized knowledge.

[0006] In addition, since the settings for synchronizing times are performed for each device, the setting content of a certain device may not be the optimal setting when viewed as a whole device group.

[0007] When recognition is performed at each time based on images captured at the same time as described above, the recognition accuracy may decrease due to poor accuracy of time synchronization.

[0008] This technology has been made in view of such a situation, and enables an appropriate time synchronization method to be easily set for each device.

Means for Solving the Problem

[0009] An information processing apparatus according to one aspect of this technology includes a distribution unit that distributes information representing a time synchronization strategy designed as a method for time synchronization between the client devices forming the same group in response to a request from the client device.

[0010] An information processing terminal according to another aspect of this technology requests the time synchronization strategy from an information processing apparatus that manages the time synchronization strategy designed as a method for time synchronization between client devices forming the same group, and receives information representing the time synchronization strategy distributed in response to the request. It also includes a time synchronization unit that synchronizes time with the client devices forming the same group according to the time synchronization strategy.

[0011] In one aspect of this technology, information representing a time synchronization strategy designed as a method for time synchronization between client devices forming the same group is distributed in response to a request from the client device.

[0012] In another aspect of this technology, a time synchronization strategy is requested from an information processing apparatus that manages the time synchronization strategy designed as a method for time synchronization between client devices forming the same group, and information representing the time synchronization strategy distributed in response to the request is received. Also, time is synchronized with the client devices forming the same group according to the time synchronization strategy.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0014] <<Summary of the Present Technology>> When it is necessary to synchronize time among a plurality of client devices, the present technology distributes time synchronization strategy information from a server to each client device, and sets a time synchronization method for each client device according to the content of the time synchronization strategy.

[0015] An optimal time synchronization strategy is set for each client device forming a predetermined group, such as for each client device of the same type, for each client device used for the same purpose, and for each client device connected to the same network.

[0016] The time synchronization strategy is designed in advance by an administrator of the server that distributes the time synchronization strategy, etc. An optimal time synchronization strategy is selected from among a plurality of types of designed time synchronization strategies and distributed to each client device. For example, a time synchronization strategy is designed that represents which time source to use to set the time in the client device and how to adjust the time.

[0017] Thereby, it becomes possible to automatically set an appropriate time synchronization method for each client device.

[0018] Hereinafter, embodiments for carrying out the present technology will be described. The description will be made in the following order. 1. Time Synchronization in an Information Processing System 2. Application Examples of Time Synchronization 3. Configuration and Operation of the Time Synchronization Strategy Server 4. Configuration of Client Devices 5. Others

[0019] <<Time Synchronization in an Information Processing System>> <Configuration of the Information Processing System> FIG. 1 is a diagram showing a configuration example of an information processing system according to an embodiment of the present technology.

[0020] The information processing system in FIG. 1 is configured by connecting a plurality of client devices to a time synchronization strategy server 1 via a network 11 such as the Internet. In the example of FIG. 1, four client devices, namely client devices A1, A2, client devices B1, and B2, are shown.

[0021] For example, client devices A1, A2, client devices B1, and B2 are connected to a network 12, which is a network such as a LAN provided in a predetermined space such as a store. Client devices A1, A2, client devices B1, and B2 are each connected to the network 11 via the network 12. Various network devices such as a DHCP (Dynamic Host Configuration Protocol) server and a Hub are connected to the network 12.

[0022] Client devices A1 and A2 are client devices of the same group A, and client devices B1 and B2 are client devices of the same group B. For example, groups of client devices are formed according to each type of client device and each use of the client device.

[0023] Various devices serving as time sources are connected to the network 11 and the network 12. The devices serving as time sources transmit time information to client devices that require time synchronization according to a predetermined protocol.

[0024] The time synchronization strategy server 1 is an information processing device that manages the time synchronization strategies of each client device. The time synchronization strategy server 1 distributes (transmits) time synchronization strategy information, which is information on the time synchronization strategy, to each client device that is an information processing terminal, and causes the time synchronization method to be set according to the time synchronization strategy.

[0025] Figure 2 is a diagram showing an example of time synchronization strategy information.

[0026] As shown in Figure 2, the time synchronization strategy information includes time source information and time adjustment information.

[0027] The time source information is information that specifies what to use as the time source. Specifying to use an NTP (Network Time Protocol) server as the time source, specifying to use a PTP GM (Precision Time Protocol Grand Master) as the time source, specifying to use a GPS (Global Positioning System) as the time source, etc. are specified by the time source information. For example, when using an NTP server as the time source, the time in the client device is adjusted based on the time information acquired from the NTP server.

[0028] The time adjustment information is information that specifies how to adjust the time in the client device to match the time of the time source (the behavior of time adjustment). Examples of the behavior of time adjustment include Step adjustment and Slew adjustment. Step adjustment is a way of adjustment that immediately matches the time even if it jumps. Slew adjustment is a way of adjustment that gradually matches the time while changing the pace at which the time progresses so as not to jump. The proper use of Step adjustment and Slew adjustment, etc. are also specified by the time adjustment information.

[0029] Each client device synchronizes the time with other client devices in the same group according to the content of the time synchronization strategy information including such information.

[0030] In the example of FIG. 1, client devices A1 and A2, which are client devices of Group A, synchronize their times according to time synchronization strategy A. Client devices A1 and A2 synchronize their times in the same behavior based on the time information obtained from the same time source.

[0031] Also, client devices B1 and B2, which are client devices of Group B, synchronize their times according to time synchronization strategy B. Client devices B1 and B2 synchronize their times in the same behavior based on the time information obtained from the same time source. Time synchronization strategy A and time synchronization strategy B are time synchronization strategies with different types of time sources and time adjustment behaviors.

[0032] In this way, the time synchronization strategy server 1 can set the same time synchronization strategy for client devices in the same group.

[0033] Also, the time synchronization strategy server 1 can set different time synchronization strategies for client devices in different groups. Even for client devices connected to the same network (Network 12), if the groups to which the client devices belong are different, the time synchronization strategy server 1 can set different time synchronization strategies.

[0034] <Setting of Time Synchronization Strategy> FIG. 3 is a diagram showing the flow of setting the time synchronization strategy.

[0035] In FIG. 3, illustrations such as Network 11 are omitted. Client devices A1 and A2 are client devices for which time synchronization strategy A is set by the time synchronization strategy server 1 as described above. Client devices B1 and B2 are client devices for which time synchronization strategy B is set.

[0036] The DHCP server 2 is, for example, a server on the network 12. The DHCP server 2 performs tasks such as assigning IP addresses to client devices connected to the network 12, such as client devices A1, A2, client devices B1, B2, etc.

[0037] In such a state, when the client device 31 is added as a client device on the network 12, the client device 31 sends a DHCP Request to the DHCP server 2 as shown by the arrow #1.

[0038] In response to the incoming DHCP Request, the DHCP server 2 sends a DHCP Response to the client device 31 as shown by the arrow #2. The DHCP Response includes the IP address assigned to the client device 31 and the address of the time synchronization strategy server 1.

[0039] The client device 31 accesses the time synchronization strategy server 1 based on the address notified by the DHCP Response and sends a Subscribe as shown by the arrow #3. Subscribe is information representing a request for registration of a client device.

[0040] The time synchronization strategy server 1 sends time synchronization strategy information to the registered client device 31 as shown by the arrow #4.

[0041] The client device 31 that has received the time synchronization strategy information sent from the time synchronization strategy server 1 sets its internal time according to the time synchronization strategy and synchronizes the time with other client devices in the same group.

[0042] When a change occurs in the configured time synchronization strategy in response to the addition of the client device 31, the time synchronization strategy server 1 appropriately Push-distributes the updated time synchronization strategy to each of the client devices A1, A2, B1, and B2, as indicated by the arrows #5-1 to #5-4. In this way, the time synchronization strategy set by the time synchronization strategy server 1 is dynamically changed according to changes in the environment and the like.

[0043] Referring to the flowcharts of FIGS. 4 and 5, a series of processes during the distribution of the time synchronization strategy will be described.

[0044] The process shown in FIG. 4 starts, for example, when the power of the client device 31 is turned on and it is connected to the network 12, as indicated by the dashed arrow #11.

[0045] In step S1, the client device 31 sends a DHCP Request to the DHCP server 2.

[0046] In step S41, the DHCP server 2 receives the DHCP Request sent from the client device 31.

[0047] In step S42, the DHCP server 2 sends a DHCP Response to the client device 31. The DHCP Response includes the IP address assigned to the client device 31 and the address of the time synchronization strategy server 1.

[0048] In step S2, the client device 31 receives the DHCP Response sent from the DHCP server 2.

[0049] In step S3, the client device 31 sends a Subscribe to the time synchronization strategy server 1. The Subscribe includes device information indicating the type of the client device 31, the type of the application of the client device 31, and the like. For example, the use of the client device 31 is specified according to the type of the application.

[0050] In step S51, the time synchronization strategy server 1 receives the Subscribe sent from the client device 31.

[0051] In step S52, the time synchronization strategy server 1 selects a time synchronization strategy according to the Subscribe. In the example of FIG. 4, a time synchronization strategy that uses time source A among time source A and time source B as the time source and uses a predetermined time adjustment behavior is selected.

[0052] In step S53, the time synchronization strategy server 1 sends time synchronization strategy information to the client device 31.

[0053] In step S4, the client device 31 receives the time synchronization strategy information sent from the time synchronization strategy server 1.

[0054] In step S5, the client device 31 sets a time synchronization method according to the time synchronization strategy.

[0055] In step S6, the client device 31 communicates with the device serving as time source A, and receives in step S7 the time information sent from the device serving as time source A.

[0056] The device serving as time source A communicates with the client device 31 in step S71, and sends time information to the client device 31 in step S72.

[0057] By repeating the processes of steps S6, S7, S71, and S72, time synchronization is performed in the client device 31.

[0058] The same processes as the above processes are performed every time a client device is added.

[0059] When the client device 32 is connected to the network 12 as shown by the dashed arrow #12 in FIG. 5, the processes of the client device 32 performed in steps S21 to S27 are the same as the processes of steps S1 to S7.

[0060] Also, the processes of the DHCP server 2 performed in steps S43 and S44 are the same as the processes of steps S41 and S42. The processes of the time synchronization strategy server 1 performed in steps S54 to S56 are the same as the processes of steps S51 to S53. Redundant explanations will be omitted as appropriate.

[0061] In the example of FIG. 5, the time synchronization strategy using time source B among time source A and time source B as the time source and using a predetermined time adjustment behavior is selected as the time synchronization strategy of the client device 32. For the client device 32, time synchronization strategy information representing such a time synchronization strategy is transmitted in step S56.

[0062] In step S24, the client device 32 receives the time synchronization strategy information transmitted from the time synchronization strategy server 1.

[0063] In step S25, the client device 32 sets the time synchronization method according to the time synchronization strategy.

[0064] In step S26, the client device 32 communicates with the device serving as time source B and receives the time information transmitted from the device serving as time source B in step S27.

[0065] The device serving as time source B communicates with the client device 32 in step S81 and transmits time information to the client device 32 in step S82.

[0066] By repeating the processes of steps S26, S27, S81, and S82, time synchronization is performed in the client device 32.

[0067] With reference to the flowcharts of FIGS. 6 and 7, a series of processes at the time of dynamic change of the time synchronization strategy will be described.

[0068] As shown by the dashed arrow #21 in FIG. 6, when the client device 33 is connected to the network 12, the processes of the client device 33 performed in steps S101 to S107 are the same as the processes of steps S1 to S7.

[0069] Also, the processes of the DHCP server 2 performed in steps S121 and S122 are the same as the processes of steps S41 and S42. The processes of the time synchronization strategy server 1 performed in steps S131 to S133 are the same as the processes of steps S51 to S53. Redundant explanations will be omitted as appropriate.

[0070] In the example of FIG. 6, a time synchronization strategy using a predetermined time source and a predetermined time adjustment behavior is selected as the time synchronization strategy for the client device 33. For the client device 33, time synchronization strategy information representing such a time synchronization strategy is transmitted in step S133.

[0071] In step S104, the client device 33 receives the time synchronization strategy information transmitted from the time synchronization strategy server 1.

[0072] In step S105, the client device 33 sets the time synchronization method according to the time synchronization strategy.

[0073] In step S106 of FIG. 7, the client device 33 communicates with the device serving as the time source and receives, in step S107, the time information transmitted from the device serving as the time source.

[0074] In step S141, the device serving as the time source communicates with the client device 33 and transmits, in step S142, the time information to the client device 33.

[0075] By repeating the processes of steps S106, S107, S141, and S142, time synchronization is performed in the client device 33.

[0076] In the time synchronization strategy server 1, the environment is constantly monitored for things such as the failure of the time source and the recovery of the time source.

[0077] When a change occurs in the environment, such as the failure of the time source, in step S134, the time synchronization strategy server 1 detects this.

[0078] In step S135, the time synchronization strategy server 1 updates (changes) the time synchronization strategy according to the change in the environment.

[0079] In step S136, the time synchronization strategy server 1 transmits the time synchronization strategy information representing the updated time synchronization strategy to the client device 33.

[0080] In step S108, the client device 33 receives the time synchronization strategy information transmitted from the time synchronization strategy server 1. The client device 33 performs the same processes as described above, such as resetting the time synchronization method, and synchronizes the time according to the updated time synchronization strategy.

[0081] As described above, in the information processing system of FIG. 1, the time synchronization strategies of the respective client devices forming the same group are set by the time synchronization strategy server 1.

[0082] By setting the time synchronization strategy designed using their own know-how in the time synchronization strategy server 1, the administrator of the time synchronization strategy server 1 can set the optimal time synchronization strategy for each client device. Also, the administrator of the time synchronization strategy server 1 can appropriately change the setting of the time synchronization strategy.

[0083] Groups are not formed according to the type of client device, but are appropriately formed according to the use of the client device, such as the type of application realized by the client device and the type of service provided by the client device. In this case, the same time synchronization strategy is set for client devices with the same use.

[0084] Also, by distributing the time synchronization strategy in response to a Subscribe from the client device, it becomes possible to dynamically reflect the change in the time synchronization strategy in each client device.

[0085] <<Examples of Application of Time Synchronization>> <Example of Application 1: Application Example to a Mixed Environment of Sensing Cameras and Robots> FIG. 8 is a diagram showing an example in which time synchronization in an information processing system is applied to a mixed environment of sensing cameras and robots.

[0086] In the example of FIG. 8, the NTP server 51 and the PTP GM 52 are shown as the devices serving as the time source.

[0087] Also, in the example of FIG. 8, robots 61-1 and 61-2 and sensing cameras 62-1 and 62-2 are shown as client devices that require a time synchronization strategy. The robots 61-1 and 61-2 and the sensing cameras 62-1 and 62-2 are connected to a time synchronization strategy server 1, an NTP server 51, and a PTP GM 52 via networks 11, 12, etc., respectively. In the case of the above-described example, the robots 61-1 and 61-2 correspond to client devices A1 and A2, and the sensing cameras 62-1 and 62-2 correspond to client devices B1 and B2.

[0088] As indicated by the dashed arrows #21-1 and #21-2, for the robots 61-1 and 61-2 that form the same group, a time synchronization strategy for robots is set by the time synchronization strategy server 1. The time synchronization strategy for robots is a strategy that uses the NTP server 51, which is a time source with low load although not high precision. The behavior when synchronizing time using the time information of the NTP server 51 is also specified by the time synchronization strategy for robots.

[0089] On the other hand, as indicated by the dash-dotted arrows #22-1 and #22-2, for the sensing cameras 62-1 and 62-2 that form the same group, a time synchronization strategy for sensing cameras is set by the time synchronization strategy server 1. The time synchronization strategy for sensing cameras is a strategy that uses the PTP GM 52, which enables high-precision time synchronization even with high load. The behavior when synchronizing time using the time information of the PTP GM 52 is also specified by the time synchronization strategy for sensing cameras.

[0090] Thus, a time synchronization strategy using the NTP server 51, which can be said to be a strategy with low processing load and communication volume, is set as the time synchronization strategy for the robots 61-1 and 61-2 where time synchronization with millisecond-order accuracy is sufficient.

[0091] Also, a time synchronization strategy using the PTP GM 52, which can be said to be a strategy suitable for high-precision time synchronization, is set as the time synchronization strategy for the sensing cameras 62-1 and 62-2 that require high-precision time synchronization.

[0092] FIG. 9 is a diagram showing an example when a client device is added to the environment of FIG. 8.

[0093] As shown on the left side of FIG. 9, when robot 61-3 is added as a client device on network 12, time synchronization strategy server 1 acquires the device information transmitted from robot 61-3 at the time of transmitting Subscribe indicated by arrow #3. The process performed between robot 61-3 and DHCP server 2 before transmitting Subscribe is the same as the process described with reference to FIG. 3. Robot 61-3 corresponds to client device 31 in FIG. 3.

[0094] Based on the device information of robot 61-3, time synchronization strategy server 1 sets a time synchronization strategy for robots to robot 61-3 as shown by arrow #4. The time synchronization strategy set for robot 61-3 is the same as the time synchronization strategy set for robots 61-1 and 61-2 which are client devices in the same group.

[0095] As described above, the administrator of the client device does not need to manually set the time synchronization method for the added client device. The administrator can set an appropriate time synchronization strategy just by connecting the client device to the network.

[0096] <Application Example 2 Application Example of Intelligent Sensor System> ·Flow of Time Synchronization FIG. 10 is a diagram showing an example in which time synchronization in an information processing system is applied to an intelligent sensor system.

[0097] For example, the intelligent sensor system shown in FIG. 10 is a system for individual business operators. A plurality of sensing cameras (surveillance cameras) are installed in spaces such as stores and venues operated by individual business operators. Sensing cameras 62-1 and 62-2 are shown in the example of FIG. 10. For example, DHCP communication is performed between sensing cameras 62-1 and 62-2 and DHCP server 2.

[0098] The sensing cameras 62-1 and 62-2 acquire the time synchronization strategy from the time synchronization strategy server 1 and synchronize their times. In the example of FIG. 10, the illustration of the time synchronization strategy server 1 is omitted. The function of the time synchronization strategy server 1 may be provided in the cloud server 101.

[0099] The sensing cameras 62-1 and 62-2 each capture the state within a space such as a store and transmit the captured images to the cloud server 101 as indicated by the arrows #51-1 and #51-2. As shown in the speech balloon of the arrow #51-1, time stamps are added to the images transmitted by the sensing cameras 62-1 and 62-2. The time stamps are added based on the times managed by each of the sensing cameras 62-1 and 62-2.

[0100] Note that the time source used for the time synchronization of the sensing cameras 62-1 and 62-2 is a network device having the function of PTP GM.

[0101] Based on the images transmitted from the sensing cameras 62-1 and 62-2, the cloud server 101 performs recognition processes such as face recognition, person tracking, and action recognition. The results of the recognition processes are used for security, customer analysis, etc.

[0102] In the image processing of the cloud server 101, images with the same time stamp added are integrated, and the integrated images are treated as images capturing the state inside the store at each time. Therefore, if the times of the respective sensing cameras do not match, a degradation in recognition performance occurs in recognition processes such as integrating and using images from multiple cameras. In particular, in the recognition process for moving objects, high-precision time synchronization is required.

[0103] [[ID=D23]]Settings for realizing high-precision time synchronization are performed by the time synchronization strategy server 1.

[0104] FIG. 11 is a diagram showing an example of time synchronization.

[0105] In the example of FIG. 11, three Hubs, namely Hub102-1 to 102-3, are provided in the network to which the sensing cameras 62-1 and 62-2 are connected. The network to which Hub102-1 to 102-3 are connected is, for example, a network within a store. The three Hubs are provided in the order of Hub102-3, Hub102-2, and Hub102-1 at positions closer to the network 11.

[0106] A network device 103-1 having the function of PTP GM is connected to Hub102-1, and a network device 103-2 having the function of PTP GM is connected to Hub102-2. In this example, two network devices having the function of PTP GM are provided, and each is connected to a different Hub.

[0107] The sensing cameras 62-1 and 62-2 are connected to the same Hub102-1 as the network device 103-1.

[0108] In this state, it is assumed that the sensing cameras 62-1 and 62-2 acquire time information from a device serving as a time source and synchronize the time. If the accuracies of the PTP GM of the network devices 103-1 and 103-2 are the same, acquiring time information from the network device 103-1, which is a PTP GM with a shorter distance via the network, can improve the accuracy of time synchronization compared to acquiring time information from the network device 103-2.

[0109] In this case, as indicated by the arrows #61-1 and #61-2, the time synchronization strategy server 1 transmits time synchronization strategy information to the sensing cameras 62-1 and 62-2 and synchronizes the time based on the time information from the PTP GM of the network device 103-1.

[0110] The sensing cameras 62-1 and 62-2 synchronize the time based on the time information transmitted as indicated by the arrows #62-1 and #62-2 from the network device 103-1, respectively.

[0111] · Case with an added sensing camera FIG. 12 is a diagram showing an example of the case where a sensing camera is added to the store of FIG. 10.

[0112] In the example of FIG. 12, as shown by the dashed circle, a sensing camera 62-3, which is one sensing camera, is added. The reasons for adding the sensing camera include reducing dead spaces in the space and improving redundancy by increasing the overlap of images by multiple cameras.

[0113] As shown by arrow #51-3, the image captured by the sensing camera 62-3 is also stamped with a time stamp and transmitted to the cloud server 101.

[0114] FIG. 13 is a diagram showing an example of time synchronization in the configuration of FIG. 12.

[0115] In this example, the sensing camera 62-3 is connected to Hub102-3.

[0116] In the case of the configuration shown in FIG. 13, the time source with a uniform network distance from all sensing cameras is the PTP GM of the network device 103-2. It is desirable for all sensing cameras, including the previously installed sensing cameras 62-1 and 62-2, to obtain time information from the PTP GM of the network device 103-2 in terms of the accuracy of the overall time synchronization.

[0117] Although it is better for each sensing camera to obtain time information from the nearest time source, it is desirable for all sensing cameras to obtain time information from the PTP GM of the network device 103-2 for the following reasons. · The times of all sensing cameras do not conflict (if the time sources are different, there is a possibility that the times of the time sources do not match). Rather than having one sensing camera with a significantly inferior time synchronization accuracy, it is desirable that all sensing cameras be synchronized with a certain degree of accuracy.

[0118] In this case, as shown by arrows #61-1 to #61-3, the time synchronization strategy server 1 transmits time synchronization strategy information to the sensing cameras 62-1 to 62-3 and synchronizes the time based on the time information from the PTP GM possessed by the network device 103-2. That is, the sensing cameras 62-1 and 62-2 are instructed to update the time synchronization strategy.

[0119] The sensing cameras 62-1 to 62-3 synchronize their times respectively based on the time information transmitted as shown by arrows #62-1 to #62-3 from the network device 103-2.

[0120] Such dynamic settings for time synchronization are performed when various environmental changes occur, such as when a sensing camera is added, when the installation position of a sensing camera moves, or when the number of sensing cameras decreases due to a failure or the like, in addition to when a sensing camera is added.

[0121] By performing such settings, even if the store operator has no skills regarding time synchronization, it becomes possible to perform appropriate time synchronization settings.

[0122] <<Configuration and Operation of Time Synchronization Strategy Server 1>> <Configuration of Time Synchronization Strategy Server 1> FIG. 14 is a block diagram showing an example of the hardware configuration of the time synchronization strategy server 1.

[0123] The time synchronization strategy server 1 is realized by a computer having a configuration as shown in FIG. 14. The time synchronization strategy server 1 may also be realized by a plurality of computers.

[0124] The CPU (Central Processing Unit) 201, ROM (Read Only Memory) 202, and RAM (Random Access Memory) 203 are interconnected by a bus 204.

[0125] The bus 204 is further connected to an input / output interface 205. Connected to the input / output interface 205 are an input unit 206 consisting of a keyboard, a mouse, etc., and an output unit 207 consisting of a display, a speaker, etc.

[0126] Also, connected to the input / output interface 205 are a storage unit 208 consisting of a hard disk, a non-volatile memory, etc., a communication unit 209 consisting of a network interface, etc., and a drive 210 for driving a removable medium 211. Communication via the network 11 or the like is performed by the communication unit 209.

[0127] FIG. 15 is a block diagram showing a functional configuration example of the time synchronization strategy server 1.

[0128] At least a part of the functional units shown in FIG. 15 is realized by executing a predetermined program by the CPU 201 of FIG. 14. The functions of the time synchronization strategy server 1 in the intelligent sensor system described with reference to FIG. 10 and the like will be appropriately described.

[0129] As shown in FIG. 15, in the time synchronization strategy server 1, a Subscribe / Unsubscribe reception unit 221, a device survival monitoring unit 222, an external detection event reception unit 223, a network topology estimation unit 224, a time synchronization strategy determination unit 225, and a time synchronization strategy distribution unit 226 are realized.

[0130] The Subscribe / Unsubscribe reception unit 221 receives Subscribes from client devices that require time synchronization and devices that serve as time sources.

[0131] When the Subscribe / Unsubscribe reception unit 221 receives a Subscribe from a client device that requires time synchronization, it updates the client information based on the device information and additionally registers the client device that requires time synchronization. When a Subscribe is transmitted, device information is sent from the client device that requires time synchronization.

[0132] Client information is a database that holds a list of client devices that require time synchronization. The client information holds the IP address of the client device that requires time synchronization, the type of the device, the use of the device, and so on.

[0133] When an update occurs in the registered content of the client information, information indicating this is supplied to the network topology inference unit 224.

[0134] In addition, when the Subscribe / Unsubscribe reception unit 221 receives a Subscribe from a device that serves as a time source, it updates the time source information based on the device information and additionally registers the device that serves as a time source. When a Subscribe is transmitted, device information is sent from a device that serves as a time source, such as a network device having the function of an NTP server or a network device having the function of a PTP GM.

[0135] Time source information is a database that holds a list of devices that serve as time sources. The time source information holds the type of the time source, additional information according to the type of the time source, and so on. The types of the time source include NTP, PTP, GPS, and so on. The additional information includes information indicating the accuracy of each time source. When the type of the time source is NTP, information such as Stratum is also appropriately held.

[0136] When an update occurs in the registered content of the time source information, information indicating this is supplied to the network topology inference unit 224. The client information and the time source information are stored, for example, in the storage unit 208 (FIG. 14).

[0137] The Subscribe / Unsubscribe reception unit 221 receives an Unsubscribe from a subscribed device and deletes the registration. When a Subscribe is performed again from a subscribed device, the Subscribe / Unsubscribe reception unit 221 updates the registered contents of the client information and the time source information.

[0138] The device survival monitoring unit 222 monitors the survival status (whether it is operating normally or not) of the devices registered in the client information and the time source information.

[0139] As a method for monitoring the survival status, there is a method of monitoring based on whether there is a response to ping (RFC1122). Also, there is a method of monitoring based on whether the communication necessary for time synchronization is being performed. When the device to be monitored is a network device having the function of PTP GM, the survival status is monitored based on whether Sync messages, DelayReqest messages, etc. are being multicast.

[0140] When the device survival monitoring unit 222 determines that the device to be monitored does not exist, it deletes the registration of that device from the client information and the time source information. This makes it possible to prevent the registration of a device that has disappeared from the network without being unsubscribed from remaining.

[0141] The external detection event reception unit 223 functions as an interface for receiving Subscribe / Unsubscribe, addition of a device, deletion of a device, and change of the state of a device. Inputs through paths other than normal survival monitoring, such as addition of a device by manual input, are received by the external detection event reception unit 223. The external detection event reception unit 223 updates the client information and the time source information according to the received contents.

[0142] The network topology inference unit 224 infers the network topology based on the client information and the list of devices registered in the time source information. As the network topology, for example, how each device is arranged on the network is inferred.

[0143] For example, for each client device, the network topology is inferred by querying the delay time to the time source that is the acquisition source of the time information. The client device can usually measure the propagation delay to the time source according to the time synchronization protocol.

[0144] Also, for each client device, the network topology is inferred by querying whether the time source that is the acquisition source of the time information exists within the same LAN. The client device can infer whether the time source exists within the same LAN by issuing a ping (RFC1122) with a limited TTL (Time To Live) to the time source.

[0145] The network topology inference unit 224 appropriately updates the network topology information based on the inference result. The network topology information is a database that holds the inference result of the network topology inference unit 224.

[0146] FIG. 16 is a diagram showing an example of a network configuration.

[0147] In the example of FIG. 16, two LANs, LAN1 and LAN2, are shown. Client devices A to C on LAN1 are shown, and time sources 1 and 2 on LAN1 are shown. Also, client devices D and E on LAN2 are shown, and time source 3 on LAN2 is shown. It is also possible for client devices A to E to use time source 4, which is a time source external to LAN1 and LAN2.

[0148] The thickness of each straight line connecting the client device and the time source represents the reachability of the network. The thicker the straight line, the smaller the propagation delay.

[0149] When such each client device is registered in the client information and each time source is registered in the time source information, in the network topology estimation unit 224, based on the matrix of delay times as shown in FIG. 17, the network topology is estimated.

[0150] In the example of FIG. 17, since the time sources reachable from clients A to C are the same, it is estimated that clients A to C are arranged on the same LAN. Also, since the time sources reachable from clients D and E are the same, it is estimated that clients D and E are arranged on the same LAN.

[0151] In this way, based on the communication situation between each client device and the time source that is the acquisition source of the time information of each client device, the arrangement of each device on the network is estimated. Instead of the propagation delay time, the arrangement of each device on the network may be estimated based on other communication situations such as the communication error rate.

[0152] When an update occurs in the content of the network topology information representing such an estimation result, information indicating that is supplied to the time synchronization strategy determination unit 225.

[0153] The time synchronization strategy determination unit 225 determines the time synchronization strategy for each client device based on the network topology information. The optimal time synchronization strategy varies depending on the type of client device, the use of the client device, etc. For example, the time synchronization strategy for each type and use of the client device is designed by the administrator of the time synchronization strategy server 1 according to the network topology.

[0154] When there are multiple candidates for the time synchronization strategy, the actual time synchronization strategy to be used is determined based on the priorities set for each candidate. If the performance is insufficient when operating with the candidate of the time synchronization strategy with the highest priority, it may be switched to the candidate of the time synchronization strategy with the next highest priority, so that the time synchronization strategy to be set for each client device is determined.

[0155] In the intelligent sensor system described with reference to FIG. 10 and the like, for example, the time synchronization strategy is determined as follows.

[0156] (1) Selection of time source The time source is selected from among the time sources from which all sensing cameras can acquire time information as follows.

[0157] (1-1) If there is GPS, GPS is selected. If there is no GPS, PTP is selected. If there is no PTP either, NTP is selected. (1-2) When there are multiple applicable time sources by the selection method of (1-1), the time source with a small difference in propagation delay time from each sensing camera is selected. (1-3) When the selection cannot be narrowed down by the selection method of (1-2), the time source with a small propagation delay time from each sensing camera is selected.

[0158] (2) Selection of time adjustment behavior According to the application or the like, it is selected whether to perform step adjustment or slew adjustment for the time alignment.

[0159] The time synchronization strategy representing such selection content is determined by the time synchronization strategy determination unit 225 and registered in the time synchronization strategy list.

[0160] The time synchronization strategy list is a database that holds the time synchronization strategies of each client device determined by the time synchronization strategy determination unit 225. Whether the client devices have different or the same time synchronization strategies depends on the usage and environment. When an update occurs in the registration content of the time synchronization strategy list, information indicating this is supplied to the time synchronization strategy distribution unit 226.

[0161] The time synchronization strategy distribution unit 226 distributes time synchronization strategy information representing the time synchronization strategy of each client device to the subscribed client devices. When there is an update to the time synchronization strategy, the time synchronization strategy information is distributed to the target client devices.

[0162] <Operation of Time Synchronization Server 1> The processing of the time synchronization server 1 having the above configuration will be described.

[0163] · Update of Client Information / Time Source Information With reference to the flowcharts of FIGS. 18 and 19, the processing when a device is added will be described.

[0164] In step S301, the added device sends a Subscribe including device information.

[0165] In step S311, the Subscribe / Unsubscribe reception unit 221 receives the Subscribe sent from the added device.

[0166] If the added device is a client device, in step S312, the Subscribe / Unsubscribe reception unit 221 acquires a list of time sources (devices serving as time sources) from the time source information.

[0167] In step S313, the Subscribe / Unsubscribe reception unit 221 sends a list of time sources to the client device and requests measurement of the delay time.

[0168] In step S302, the client device receives the information sent from the Subscribe / Unsubscribe reception unit 221.

[0169] In step S303, the client device communicates with each of the time sources registered in the list and measures the delay time.

[0170] In step S304, the client device transmits a list of the delay times with each time source to the time synchronization strategy server 1.

[0171] In step S314, the Subscribe / Unsubscribe reception unit 221 receives the list of the delay times sent from the client device.

[0172] In step S315, the Subscribe / Unsubscribe reception unit 221 registers the information of the client device in the client information. The Subscribe / Unsubscribe reception unit 221 registers, as the information of the client device, the information of the delay time with each time source based on the list of the delay times sent from the client device.

[0173] When the added device is a client device, the client information is updated as described above.

[0174] On the other hand, when the added device is a time source, in step S321 of FIG. 19, the Subscribe / Unsubscribe reception unit 221 registers the information of the added time source in the time source information.

[0175] In step S322, the Subscribe / Unsubscribe reception unit 221 acquires the list of the client devices from the client information.

[0176] In step S323, the Subscribe / Unsubscribe reception unit 221 identifies existing client devices based on the list and causes the existing client devices to measure the delay time from the new time source.

[0177] In each existing client device, in response to the request from the Subscribe / Unsubscribe reception unit 221, the delay time from the new time source is measured. Information representing the measurement result is transmitted to the time synchronization strategy server 1 and acquired by the Subscribe / Unsubscribe reception unit 221.

[0178] In step S324, the Subscribe / Unsubscribe reception unit 221 registers the information on the delay time from the new time source, which was measured in the existing client devices, in the client information.

[0179] If the added device is a time source, the client information and the time source information are updated as described above.

[0180] · Setting of time synchronization strategy With reference to the flowchart of FIG. 20, a series of processes for setting the time synchronization strategy will be described.

[0181] When the client information is updated, in step S351, this is notified to the network topology inference unit 224.

[0182] Also, when the time source information is updated, in step S361, this is notified to the network topology inference unit 224.

[0183] In step S371, the network topology inference unit 224 receives the update notification of the client information.

[0184] In step S372, the network topology inference unit 224 receives the update notification of the time source information.

[0185] In step S373, the network topology estimation unit 224 generates a delay time matrix as described with reference to FIG. 17 based on the delay time between each client device and the time source included in the updated client information.

[0186] In step S374, the network topology estimation unit 224 estimates the network topology based on the delay time matrix, and updates the network topology information based on the estimation result.

[0187] When the network topology information is updated, in step S381, this is notified to the time synchronization strategy determination unit 225.

[0188] In step S391, the time synchronization strategy determination unit 225 receives a notification of the update of the network topology information.

[0189] In step S392, the time synchronization strategy determination unit 225 selects a time source for which the delay time from each client device becomes as uniform as possible based on the updated network topology information.

[0190] In step S393, the time synchronization strategy determination unit 225 changes the time source to be assigned to each client device (the time source for obtaining time information) based on the selection result of the time source, and updates the time synchronization strategy list.

[0191] When the time synchronization strategy list is updated, in step S401, this is notified to the time synchronization strategy distribution unit 226.

[0192] In step S411, the time synchronization strategy distribution unit 226 receives a notification of the update of the time synchronization strategy information.

[0193] In step S412, the time synchronization strategy distribution unit 226 acquires the time source that is the acquisition source of the time information of each client device from the time synchronization strategy list.

[0194] If there is a client device whose time source, which is the acquisition source of the time information, has changed, in step S413, the time synchronization strategy distribution unit 226 distributes time synchronization strategy information to the client device whose time source has changed. Here, the time synchronization strategy information to be distributed is the updated time synchronization strategy information including the time source information specifying the new time source.

[0195] Through the above processing, it becomes possible to determine the optimal time synchronization strategy for the overall operation of the client devices in consideration of requirements such as time synchronization according to the application, and to set it for each client device. For example, even for client devices existing within the same network, it is possible to set different time synchronization strategies for each client device with different applications.

[0196] By improving the accuracy of time synchronization, it becomes possible to improve the performance of applications and services realized using the client devices.

[0197] In addition, it becomes possible to make each client device's time synchronization strategy follow various environmental changes such as changes in the arrangement or number of client devices. Also, it becomes possible to automatically perform the follow-up of the time synchronization strategy without the operation of the administrator.

[0198] Since the time synchronization strategy settings of multiple client devices are performed by the time synchronization strategy server 1, it becomes possible to centrally perform the maintenance of the time synchronization strategy. For example, by the administrator of the time synchronization strategy server 1 changing the time synchronization strategy settings, the change can be reflected in all target client devices.

[0199] Since there is no need to individually maintain the time synchronization strategy settings of each client device, the maintenance of the time synchronization strategy becomes easier.

[0200] <<Configuration of Client Device>> FIG. 21 is a block diagram showing an example of the functional configuration of a client device.

[0201] Each functional configuration shown in FIG. 21 is realized by a CPU of a computer having the configuration shown in FIG. 14, which is mounted on each client device, executing a predetermined program. Each client device is mounted with a computer having the configuration shown in FIG. 14, together with a hardware configuration corresponding to the type of the client device. Hereinafter, the configuration of the computer shown in FIG. 14 will be appropriately cited as the configuration of the client device and described.

[0202] As shown in FIG. 21, in the client device, a time synchronization strategy acquisition unit 251, a time synchronization unit 252, and a control unit 253 are realized.

[0203] The time synchronization strategy acquisition unit 251 communicates with the time synchronization strategy server 1 by controlling the communication unit 209 (FIG. 14), and receives the time synchronization strategy information distributed from the time synchronization strategy server 1. The time synchronization strategy information acquired from the time synchronization strategy server 1 is supplied to the time synchronization unit 252.

[0204] The time synchronization unit 252 synchronizes the time with other client devices in the same group according to the time synchronization strategy represented by the time synchronization strategy information supplied from the time synchronization strategy acquisition unit 251.

[0205] For example, the time synchronization unit 252 acquires time information from a time source specified by the time synchronization strategy. Also, the time synchronization unit 252 adjusts the time in the client device according to the behavior specified by the time synchronization strategy. The time synchronization unit 252 outputs the time information in the client device to the control unit 253.

[0206] The control unit 253 controls each part of the client device according to the time managed by the time synchronization unit 252.

[0207] For example, when the type of the client device is a robot, the control unit 253 performs control such as driving the driving unit according to the time managed by the time synchronization unit 252.

[0208] Also, when the type of the client device is a sensing camera, the control unit 253 controls the camera to perform shooting. The control unit 253 adds a time stamp representing the time managed by the time synchronization unit 252 to the image obtained by shooting, and transmits it to the cloud server 101.

[0209] <<Others>> <Other application examples> FIG. 22 is a diagram showing other application examples.

[0210] In the example shown in FIG. 22, three smartphones are shown as client devices. By synthesizing (joining together) the images taken by the cameras mounted on the three smartphones, for example, a 360-degree omnidirectional image is generated. The application example shown in FIG. 22 is an application example of time synchronization to a 360-degree camera as an application.

[0211] The generation of the omnidirectional image may be performed within the smartphone, or may be performed on a server on the network 11. Spatial surveying may be performed by synthesizing the images taken by the cameras mounted on the three smartphones.

[0212] In such an application, in order to synthesize the images taken by a plurality of client devices without contradiction, it is necessary to match the shooting timings or attach correct time stamps to the images obtained by shooting.

[0213] In the example of FIG. 22, as time sources, there are an NTP server 51 on the network 11 and a time source of the mobile phone network 13. The client device connected to the mobile phone network 13 can acquire time information from network devices such as base stations.

[0214] The three smartphones are all client devices that can be connected to the mobile phone network 13. In the example of FIG. 22, as shown by the dashed arrow #101, according to the time synchronization strategy set by the time synchronization strategy server 1, the three smartphones acquire time information from the mobile phone network 13 and synchronize their times.

[0215] FIG. 23 is a diagram showing an additional example of a client device participating in the 360-degree camera application.

[0216] As shown in the lower right of FIG. 23, assume that a laptop-type PC is added as a client device participating in the 360-degree camera application. The PC is a client device that cannot be connected to the mobile phone network 13.

[0217] In this case, in order to prevent contradictions in the times of all client devices participating in the 360-degree camera application, the time synchronization strategy is updated to use the NTP server 51 as the time source. That is, the time synchronization strategy of each of the three smartphones that had previously participated in the 360-degree camera application is also updated.

[0218] The three smartphones and one PC each acquire time information from the NTP server 51 and synchronize their times according to the time synchronization strategy set by the time synchronization strategy server 1. Note that the NTP server 51 is a time source available to all client devices, including the PC, participating in the 360-degree camera application.

[0219] By updating the time synchronization strategy in response to the addition of client devices, it becomes possible to improve the accuracy of the 360-degree camera application.

[0220] <Others> The above-described series of processes can be executed either by hardware or by software. When the series of processes is executed by software, the program constituting the software is installed in a computer incorporated in dedicated hardware, or in a general-purpose personal computer or the like.

[0221] The program to be installed is recorded and provided on a removable medium 211 shown in FIG. 14, which consists of an optical disk (such as a CD-ROM (Compact Disc-Read Only Memory), a DVD (Digital Versatile Disc), etc.) or a semiconductor memory. Further, it may be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital broadcasting. The program can be installed in advance in the ROM 202 or the storage unit 208.

[0222] The program executed by the computer may be a program in which processing is performed in time series in accordance with the order described in this specification, or a program in which processing is performed in parallel or at a necessary timing such as when a call is made.

[0223] In this specification, a system means a collection of a plurality of components (devices, modules (parts), etc.), and it does not matter whether all the components are in the same housing. Therefore, a plurality of devices housed in separate housings and connected via a network, and a single device in which a plurality of modules are housed in one housing are both systems.

[0224] Note that the effects described in this specification are merely examples and are not limiting, and there may be other effects.

[0225] The embodiments of the present technology are not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present technology.

[0226] For example, the present technology can adopt a cloud computing configuration in which one function is shared and jointly processed by multiple devices via a network.

[0227] In addition, each step described in the above flowchart can be executed by one device or can be shared and executed by multiple devices.

[0228] Furthermore, when a single step includes multiple processes, the multiple processes included in that single step can be executed by one device or can be shared and executed by multiple devices.

[0229] <Example of configuration combination> The present technology can also adopt the following configuration.

[0230] (1) An information processing apparatus including a distribution unit that distributes information representing a time synchronization strategy designed as a method of time synchronization between the client devices forming the same group in response to a request from a client device. Information processing apparatus. (2) The group is formed by the client devices used for the same purpose, The distribution unit distributes information representing the time synchronization strategy designed according to the application to the client devices forming the same group. The information processing apparatus according to (1) above. (3) When the time synchronization strategy is updated in response to a change in the environment, the distribution unit distributes information representing the updated time synchronization strategy to the client devices forming the group. The information processing apparatus according to (1) or (2) above. (4) Even when the client devices forming different groups are connected to the same network, the distribution unit distributes information representing different time synchronization strategies to the client devices forming each group. The information processing apparatus according to any one of (1) to (3) above. (5) The time synchronization strategy designed for each group is changed according to the input by the administrator. The information processing apparatus according to any one of (1) to (4) above. (6) Further comprising an inference unit that infers the network layout relationship between each of the client devices and the time source that is the acquisition source of the time information of each of the client devices based on the communication status between them. The information processing apparatus according to any one of (1) to (5) above. (7) Further comprising a time synchronization strategy determination unit that determines the time synchronization strategy for each of the client devices based on the layout relationship, The distribution unit distributes information representing the determined time synchronization strategy. The information processing apparatus according to (6) above. (8) The information representing the time synchronization strategy includes at least information specifying the type of the time source and information specifying the method of time adjustment using the time information acquired from the time source. The information processing apparatus according to any one of (1) to (7) above. (9) An information processing apparatus, In response to a request from a client device, distributes information representing a time synchronization strategy designed as a method of time synchronization between the client devices forming the same group. Distribution method. (10) A time synchronization strategy acquisition unit that requests the time synchronization strategy from an information processing apparatus that manages the time synchronization strategy designed as a method of time synchronization between client devices forming the same group and receives the information representing the time synchronization strategy distributed in response to the request, A time synchronization unit that synchronizes time with the client devices forming the same group according to the time synchronization strategy. An information processing terminal comprising. (11) The group is formed by the client devices used for the same purpose, The time synchronization strategy acquisition unit receives information representing the time synchronization strategy designed according to the purpose and distributed to the client devices forming the group. The information processing terminal according to (10) above. (12) When the time synchronization strategy acquisition unit receives information representing the updated time synchronization strategy distributed when the time synchronization strategy is updated according to changes in the environment. The information processing terminal according to (10) or (11) above. (13) The information representing the time synchronization strategy includes at least first information specifying the type of time source and second information specifying how to adjust the time using the time information obtained from the time source. The information processing terminal according to any one of (10) to (12) above. (14) The time synchronization unit synchronizes the time by using the time information obtained from the time source specified by the first information in the manner of adjustment specified by the second information. The information processing terminal according to (13) above. (15) An information processing terminal requests the time synchronization strategy from an information processing device that manages the time synchronization strategy designed as a method for time synchronization between client devices forming the same group, receives information representing the time synchronization strategy distributed in response to the request, and synchronizes the time with the client devices forming the same group according to the time synchronization strategy. Time synchronization method.

Explanation of reference numerals

[0231] 1 Time Synchronization Strategy Server, 2 DHCP Server, 31 Client Device, 51 NTP Server, 52 PTP GM, 61-1 to 61-3 Robot, 62-1, 62-2 Sensing Camera, 101 Cloud Server, 221 Subscribe / Unsubscribe Reception Unit, 222 Device Survival Monitoring Unit, 223 External Detection Event Reception Unit, 224 Network Topology Inference Unit, 225 Time Synchronization Strategy Determination Unit, 226 Time Synchronization Strategy Distribution Unit, 251 Time Synchronization Strategy Acquisition Unit, 252 Time Synchronization Unit, 253 Control Unit

Claims

1. A distribution unit that distributes information representing a time synchronization strategy designed according to the application as a method for time synchronization between client devices for client devices forming the same group, where the group is formed by the client devices used for the same application An information processing device.

2. The information processing device according to claim 1, wherein when an update of the time synchronization strategy occurs according to a change in the environment, the distribution unit distributes information representing the updated time synchronization strategy to the client devices forming the group.

3. The information processing device according to claim 1, wherein even when client devices forming different groups are connected to the same network, the distribution unit distributes information representing different time synchronization strategies to the client devices forming each group. The information processing device according to claim 1.

4. The information processing device according to claim 1, wherein the time synchronization strategy designed for each group is changed according to an input by an administrator. The information processing device according to claim 1.

5. The information processing device according to claim 1, further comprising an estimation unit that estimates the arrangement relationship on the network between the client device and the time source based on the communication status between each client device and the time source that is the acquisition source of the time information of each client device. The information processing device according to claim 1.

6. The information processing device according to claim 5, further comprising a time synchronization strategy determination unit that determines the time synchronization strategy of each client device based on the arrangement relationship, and the distribution unit distributes information representing the determined time synchronization strategy. The information processing device according to claim 5.

7. The information representing the time synchronization strategy includes at least information specifying the type of the time source and information specifying the method of adjusting the time using the time information acquired from the time source. The information processing device according to claim 1.

8. An information processing device distributes information representing a time synchronization strategy designed according to the application as a method for time synchronization between client devices for client devices forming the same group, where the group is formed by the client devices used for the same application A distribution method.

9. A time synchronization strategy acquisition unit that receives information representing the time synchronization strategy distributed from an information processing device that manages the time synchronization strategy designed according to the application as a method for time synchronization between client devices forming the same group, A time synchronization unit that synchronizes time with the client devices forming the same group according to the time synchronization strategy is provided, wherein the group is formed by the client devices used for the same purpose information processing terminal.

10. The time synchronization strategy acquisition unit receives information representing the updated time synchronization strategy that is distributed when the time synchronization strategy is updated according to changes in the environment The information processing terminal according to claim 9.

11. The information representing the time synchronization strategy includes at least first information specifying the type of time source and second information specifying how to adjust the time using the time information obtained from the time source The information processing terminal according to claim 9.

12. The time synchronization unit synchronizes time by using the time information obtained from the time source specified by the first information in the manner of adjustment specified by the second information The information processing terminal according to claim 11.

13. An information processing terminal receives information representing the time synchronization strategy distributed from an information processing device that manages a time synchronization strategy designed according to the application as a method for time synchronization between client devices forming the same group, synchronizes time with the client devices forming the same group according to the time synchronization strategy, wherein the group is formed by the client devices used for the same purpose time synchronization method.

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