Patent Description:
Precision time protocol (PTP) defined in IEEE <NUM> is known as a means for performing time synchronization between devices on a network with high accuracy of microseconds or more. In PTP, a message to be exchanged to establish synchronization between the PTP master and the PTP slave is defined. Hereinafter, a network relay compatible with PTP is also referred to as a PTP compatible device. Furthermore, a master synchronized with a reference time of a global positioning system (GPS) or the like is called a grand master.

The PTP compatible device includes a PTP master and a PTP slave. One PTP compatible device may operate as both the PTP master and the PTP slave. For example, a relay compatible with PTP operates as a PTP master for a certain device to perform time synchronization of the device, and performs time synchronization as a PTP slave for another device. Furthermore, each PTP compatible device connected to the relay can also be switched to either the PTP master or the PTP slave.

Furthermore, a PTP compatible device such as a relay can remove variations in packet delay (jitter) in the network by using a boundary clock (BC) function. However, synchronization performance of a synchronization circuit of the network relay is generally optimized on the premise of direct connection with a cable, and thus synchronization cannot be performed in a poor (for example, a packet drop rate is high, a delay jitter amount is large, or the like) network environment in many cases. In a case where the motivation characteristics of the relay are not suitable for the characteristics of the network line, there is a case where synchronization as a PTP slave cannot be performed, and even if the BC function is enabled, a jitter of the network line cannot be removed, and devices of the entire system cannot be synchronized.

It is desirable to enable the BC function of the PTP compatible device that has a characteristic of easy time synchronization in the provided network line. However, it is difficult to select an optimal PTP compatible device on the basis of the characteristic with respect to network line quality. IEEE <NUM> defines PTP via a local area network (LAN), and IEEE <NUM> v2 further defines PTP compatible with a wide area network (WAN), but does not define characteristics related to the time synchronization of the PTP compatible device in a network environment. Furthermore, SMPTE (Society of Motion Picture and Television Engineers) <NUM>-<NUM> defines a PTP broadcast profile, but does not define characteristics related to time synchronization of a PTP compatible device in a network environment.

For example, a device for selecting an optimal path between a PTP master and a PTP slave by monitoring performance of a network path using an examination packet has been proposed (see Patent Document <NUM>), but path selection is not performed on the basis of characteristics of a PTP compatible device.

Furthermore, a method of evaluating a synchronization feature of a PTP compatible device by packet drop and guaranteeing network line quality on the basis of a pattern of the packet drop has been proposed (see Patent Document <NUM>), but the method is not a method of processing a characteristic in a network environment that can be a determination criterion for enabling the BC function. Note that, in this method, the quality of the entire network line is improved in accordance with a device having the lowest synchronization performance to thereby prevent deterioration of synchronization accuracy, and thus cost effectiveness is not realistic.

Non-patent document "<NPL>) compares Boundary Clock and VLAN Priority to analyze their contribution to precise clock synchronization. Non-patent document "<NPL>et al) describes how multiple Ordinary Clocks can share the same time information and to act transparently to the external system as one Boundary Clock.

An object of the present disclosure is to provide an information processing apparatus, an information processing method, and a computer program for processing characteristic information regarding easiness of time synchronization of a device in a network environment.

The present disclosure has been made in view of the above problems, and the invention disclosed herein is defined by the appended claims. A first aspect thereof is an information processing apparatus including
a control unit that associates a boundary clock function retaining device having a boundary clock function with network environment resistance index information indicating resistance to a network environment related to time synchronization of the boundary clock function retaining device.

The network environment resistance index information is information indicating accuracy of the time synchronization of the boundary clock function retaining device corresponding to network environment information indicating the network environment. Alternatively, the network environment resistance index information is the network environment resistance index information is information indicating the network environment in a case where accuracy of the time synchronization of the boundary clock function retaining device is equal to or more than a predetermined value.

Furthermore, the network environment information indicating the network environment is network load information indicating strength of a network load related to the boundary clock function retaining device. The network load information is information generated on the basis of packet transfer jitter information indicating a packet transfer jitter and packet transfer delay information indicating a packet transfer delay. The packet transfer jitter information has a higher contribution rate to the network load information than the packet transfer delay information.

The control unit determines, from among a plurality of the boundary clock function retaining devices connected to a first network line, a first intra-network line master device that performs time synchronization with a second intra-network line device connected by a second network line different from the first network line on the basis of the network environment resistance index information associated with each of the boundary clock function retaining devices.

Furthermore, a second aspect of the present disclosure is an information processing method including
a control step of associating a boundary clock function retaining device having a boundary clock function with network environment resistance index information indicating resistance to a network environment related to time synchronization of the boundary clock function retaining device.

Furthermore, a third aspect of the present disclosure is a computer program described in a computer-readable form, the computer program causing a computer to function as
a control unit that associates a boundary clock function retaining device having a boundary clock function with network environment resistance index information indicating resistance to a network environment related to time synchronization of the boundary clock function retaining device.

The computer program according to the third aspect of the present disclosure is such that a computer program described in a computer-readable format so as to implement predetermined processing on a computer is defined. In other words, by installing the computer program according to the third aspect of the present disclosure in a computer, a cooperative action is exerted on the computer, and similar operation and effect to those of the information processing apparatus according to the first aspect of the present disclosure can be obtained.

According to the present disclosure, it is possible to provide an information processing apparatus, an information processing method, and a computer program that define network environment resistance index information indicating a system to a network environment regarding time synchronization of a device that has a boundary clock function and is compatible with PTP, and perform processing such as determination of on/off of the boundary clock function of each device, setting of master/slave, and domain change on the basis of the network environment resistance information of each device.

Note that the effects described in the present disclosure are merely examples, and the effects brought by the technology disclosed in the present description are not limited thereto. Furthermore, in addition to the above-described effects, the present disclosure may further exhibit additional effects.

Other objects, features, and advantages of the present disclosure will become apparent from a more detailed description based on embodiments described below and the accompanying drawings.

Hereinafter, the present disclosure will be described in the following order with reference to the drawings.

<FIG> schematically illustrates a configuration example of a time synchronization system <NUM> that performs time synchronization on the basis of PTP. In the illustrated time synchronization system <NUM>, a first base <NUM>, a second base <NUM>, and a third base <NUM> are interconnected via a wide area network line <NUM>. When the packet transfer of each base <NUM> to <NUM> is performed via the wide area network line <NUM>, it is assumed that packet drop or a delay jitter occurs.

The base here refers to a site that constructs a small-scale network line such as a LAN. The site may be one building, one floor in a building, or a studio. Each base includes a network line laid in the base and an intra-network line device interconnected via the network line. In <FIG> (and drawings referred to in the following description), illustration of network lines in a base is omitted, and a configuration in which each intra-network line device is connected to a network relay that relays the wide area network line <NUM> is illustrated. In each base (or in a network line), basically, a master device synchronized with a reference time (an intra-network line master device, and hereinafter, also referred to as a "site PTP master" in the present description) is installed, and other intra-network line devices on the same base can synchronize with the reference time through the intra-network line master device. Furthermore, the master device that is equipped with a time source (basically, a GPS receiver) and acquires the reference time by itself is referred to as a grand master (GM). A base having the grand master is a GM base, and a base not having the grand master is a non-GM base. In the time synchronization system <NUM> illustrated in <FIG>, the first base <NUM> is a GM base and the second base <NUM> and the third base <NUM> are non-GM bases. Time synchronization of the time synchronization system <NUM> is achieved by the second base <NUM> and the third base <NUM> performing time synchronization with the first base <NUM>.

The first base <NUM> includes a grand master <NUM>, a device <NUM>, and a network relay <NUM> connected to another site via the wide area network line <NUM>. Furthermore, the second base <NUM> includes a device <NUM>, a device <NUM>, and a network relay <NUM> connected to another site via the wide area network line <NUM>. Furthermore, the third base <NUM> includes a device <NUM>, a device <NUM>, a device <NUM>, and a network relay <NUM> connected to another site via the wide area network line <NUM>. Note that each site <NUM> to <NUM> may further include a device (not illustrated).

Each device (including a grand master and a network relay) in each site <NUM> to <NUM> includes one or more ports for connecting to another device or the wide area network line <NUM>. Each device can switch to one of the PTP master and the PTP slave to operate. Furthermore, in a case of a device that includes a plurality of ports and is simultaneously connected to a plurality of devices like a network relay, it is assumed that a relationship between the PTP master and the PTP slave can be set with a device connected at each port (for example, one network relay can be the PTP slave for a certain device and meanwhile can be the PTP master for another device). In addition, it is assumed that the network relay having a BC function can determine on/off of the BC function for each port.

In the first base <NUM> that is a GM base, the grand master <NUM> is synchronized with a reference time supplied from a clock source such as GPS. The network relay <NUM> operates as the PTP slave with respect to the grand master <NUM>, and performs time synchronization with the grand master <NUM>. Furthermore, the device <NUM> operates as the PTP slave and performs time synchronization with the network relay <NUM> as the PTP master.

In the non-GM base, for example, a device having a boundary clock (BC) function with the highest network environment resistance index among the devices in the non-GM base is selected as the site PTP master. Note that the network environment resistance index is information indicating accuracy of time synchronization of the BC function with respect to the network environment, and details thereof will be described later. The site PTP master performs time synchronization with the reference time as the PTP slave for a device (for example, a device in the GM base) that is time-synchronized with the reference time, and then provides the reference time in its own base.

In the second base <NUM>, since the network relay <NUM> has the BC function with the highest network environment resistance index for the wide area network line <NUM>, it is selected as the site PTP master. Therefore, the network relay <NUM> performs time synchronization as the PTP slave with respect to the network relay <NUM> in the GM base <NUM>, and operates as the PTP master with respect to the device <NUM> and the device <NUM> in the second base <NUM>, and the device <NUM> and the device <NUM> perform time synchronization with the network relay <NUM>.

In the third base <NUM>, since the device <NUM> has the BC function with the highest network environment resistance index for the wide area network line <NUM>, it is selected as the site PTP master. Therefore, the device <NUM> operates as the PTP slave with respect to the network relay <NUM> in the GM base <NUM>, and performs time synchronization with the reference time. In addition, the device <NUM> can be connected to the device <NUM>, which is the site PTP master, through an external analog interface to perform time synchronization. The device <NUM> operates as the PTP master in another domain, and the network relay <NUM> performs, as the PTP slave, time synchronization with the device <NUM>. Furthermore, the network relay <NUM> operates as the PTP master for the device <NUM>, and the device <NUM> performs, as the PTP slave, time synchronization with the network relay <NUM>.

Note that, in <FIG>, in a case where the PTP compatible device is operating as the PTP master with respect to a peer, "M" is entered in the port connected to the peer, and in a case where the PTP compatible device is operating as the PTP slave with respect to a peer, "S" is entered in the port connected to the peer (the same applies to other drawings). Furthermore, in order to identify the domain of the time synchronization, the ports are colored with different shades of gray for each domain. In the example illustrated in <FIG>, the first base <NUM>, the second base <NUM>, and the device <NUM> of the third base <NUM> belong to the same domain that is time-synchronized by the grand master <NUM>. Furthermore, the device <NUM>, the device <NUM>, and the network relay <NUM> in the third base <NUM> belong to a domain different from the domain described above in which the device <NUM> performs time synchronization as the PTP master. Furthermore, although the "domain" is also defined in IEEE <NUM> standard, in the present description, the "domain" is an identifier indicating a set including a plurality of devices that performs time synchronization and interacts with each other by using PTP.

A delay jitter occurs when a packet is transferred on a network. By using the BC function of the PTP compatible device, a network jitter can be removed. For example, the BC function is implemented in the network relay. However, since the synchronization performance of the synchronization circuit of the network relay is generally optimized on the premise of direct connection with a cable, it is often not possible to perform time synchronization with the grand master as the PTP slave in a case where the network environment is poor or in a case where synchronization characteristics of the devices are not suitable for the characteristics of the network line. Even if the BC function of the network relay is enabled, there arises a problem that a jitter of the network line cannot be removed and the devices of the entire time synchronization system cannot be time-synchronized.

This problem will be discussed with reference to a time synchronization system <NUM> illustrated in <FIG>. The illustrated time synchronization system <NUM> includes two sites of a first base <NUM> that is a GM base and a second base <NUM> that is a non-GM base. The first base <NUM> includes a grand master <NUM>, a device <NUM>, and a network relay <NUM>. Furthermore, the second base <NUM> includes a device <NUM>, a device <NUM>, and a network relay <NUM>. The sites are connected by a wide area network line <NUM>.

Time synchronization in the first base <NUM> that is a GM base is achieved by a procedure similar to that of the time synchronization system <NUM> described above. Here, synchronization characteristics of the network relay <NUM> on the second base <NUM> side are not suitable for the characteristics of the wide area network line <NUM>, the network relay <NUM> cannot perform time synchronization with the network device <NUM> in the GM base <NUM> as a PTP slave. Therefore, even if the BC function of the network relay <NUM> is enabled, the jitter of the wide area network line <NUM> cannot be removed, and thus the devices of the entire time synchronization system <NUM> cannot be synchronized. In <FIG>, a "×" mark is attached to a device that cannot perform time synchronization.

It is desirable to enable the BC function of the PTP compatible device having network environment resistance, which can easily perform time synchronization even with the provided wide area network line <NUM>. Regarding the index indicating the network environment resistance of the PTP compatible device, there is no definition in IEEE <NUM> v2 or SMPTE <NUM>-<NUM>. Furthermore, the index indicating network environment resistance is not described in a catalog as a product specification of the PTP compatible device. Thus, it is difficult to select an optimal PTP compatible device on the basis of the characteristic with respect to the network line quality.

Accordingly, in the present disclosure, index data representing network environment resistance (also referred to as the "network environment resistance index information" in the present description) among the synchronization performance in the PTP compatible device, and an evaluator and an evaluation method for deriving the index are defined. The network environment resistance index information according to the present disclosure is characteristic information that is not defined by technical standards related to time synchronization such as IEEE <NUM> v2 and SMPTE <NUM>-<NUM>, and is not a product specification described in a product catalog.

Specifically, a management device that manages the network environment resistance index information of each PTP compatible device having the BC function in association with each PTP compatible device is installed in the time synchronization system. Among the respective sites constituting the time synchronization system, while time synchronization is possible in a site (GM base) where the grand master exists, in a site (a non-GM base) where the grand master does not exist, highly accurate time synchronization may not be achieved via a device (for example, a network relay) that does not have sufficient network environment resistance index information for a provided network line. On the other hand, in the present disclosure, a PTP compatible device having sufficient network environment resistance index information for a provided network line is selected as a device that performs time synchronization with a device in a time-synchronized network line such as a GM base on the basis of the network environment resistance index information of each PTP compatible device in the site (in particular, the non-GM base) managed by the management device. In this manner, according to the present disclosure, devices in each site that is a non-GM base can perform time synchronization with devices in the GM base, and the time synchronization of the devices of the entire time synchronization system can be achieved.

Furthermore, according to the present disclosure, in a site (for example, a non-GM base), in a case where a certain PTP compatible device is selected as a device that performs time synchronization with a PTP compatible device of a GM base on the basis of the network environment resistance index information, the BC function corresponding to two ports to be PTP paths is determined to be turned off among a plurality of ports of the network relay with the BC function (for example, the network relay <NUM> in the non-GM base <NUM> of the time synchronization system <NUM>) passed through the PTP path connecting the selected device and the GM base. Thus, the device (for example, the device <NUM> in the non-GM base <NUM> of the time synchronization system <NUM>) selected as the PTP master in the non-GM base can perform time synchronization with the device (for example, the network relay <NUM>) in the GM base. Note that, in the present description, a PTP path means a path for performing time synchronization, and by connecting one device (PTP slave) to the other device (PTP master (including the grand master)) through the PTP path, the one device can perform time synchronization with the other device.

Furthermore, according to the present disclosure, it is possible to perform time synchronization with the site PTP master by being directly connected to the site PTP master in the same site that performs time synchronization with the grand master in a site (for example, a non-GM base), and it is possible to determine a device (for example, the device <NUM> in the non-GM base <NUM> of the time synchronization system <NUM>) in the non-GM base as the PTP master (in another domain) in the same site.

Furthermore, according to the present disclosure, in a site (for example, a non-GM base), a PTP path connecting a PTP master and a PTP slave can be determined on the basis of the network environment resistance index information of each PTP compatible device having the BC function. For example, in the non-GM base <NUM> of the time synchronization system <NUM>, a PTP path connecting the device <NUM> to be a PTP master and the device <NUM> to be a PTP slave is determined on the basis of the network environment resistance index information of each device.

Furthermore, according to the present disclosure, in a site (for example, a non-GM base), on/off of the BC function corresponding to two ports of the PTP path can be determined among the plurality of ports included in the network relay (for example, the network relay <NUM> in the non-GM base <NUM> of the time synchronization system <NUM>) having the BC function and existing in the PTP path on the basis of the network environment resistance index information of each PTP compatible device having the BC function.

Furthermore, according to the present disclosure, a PTP domain of the network relay and a predetermined device existing in the PTP path among respective devices in the non-GM base can be determined on the basis of the PTP path.

As described above, according to the present disclosure, it is possible to enable the BC function of each PTP compatible device having the BC function and select the PTP master in the non-GM base on the basis of the network environment resistance index information of each PTP compatible device in a site (for example, a non-GM base). When the system configuration of the provided network line changes, the PTP master in the non-GM base is determined again. The change in the system configuration includes a change in the network environment, a change in the network environment resistance index information of at least a part of PTP compatible devices in the non-GM base, replacement of the devices in the non-GM base, increase of the devices, and removal of some devices.

The selection of the PTP master in a site (for example, a non-GM base) based on the network environment resistance index information according to the present disclosure is performed when the site is activated.

Furthermore, according to the present disclosure, in a case where a failure occurs in at least one of a plurality of PTP compatible devices having the BC function and existing in a site (for example, a non-GM base), the PTP master in the non-GM base can be selected on the basis of the network environment resistance index information of each of the remaining PTP compatible devices having the BC function in which no failure has occurred.

According to the present disclosure, it is possible to determine whether or not each PTP compatible device having the BC function is a device capable of performing time synchronization with predetermined or higher accuracy on the basis of the network environment resistance index information of each PTP compatible device having the BC function and the information indicating the network environment.

<FIG> schematically illustrates a configuration example of an evaluation system <NUM> that measures the network environment resistance index information of a device. The illustrated evaluation system <NUM> includes a grand master <NUM> and a measurement target device <NUM> disposed across a network emulator <NUM>, and an evaluator <NUM> that evaluates the network environment resistance index information of the device <NUM>.

The device <NUM> as an evaluation target is assumed to be the PTP compatible device having the BC function. The network emulator <NUM> is a device that emulates (reproduces) a network environment of a network line that is assumed to be provided in a time synchronization system in which the device <NUM> is actually used. When packet transfer is performed by the grand master <NUM> and the device <NUM>, the network emulator <NUM> imparts a network load such as a network jitter or a packet loss rate, and reproduces a network environment of an actually provided network line.

A synchronization signal is transferred between the grand master <NUM> and the device <NUM> via a PTP path on the network emulator <NUM>. Then, the evaluator <NUM> measures a phase difference, a frequency shift, and the like of the synchronization signal on the device <NUM> side with respect to the synchronization signal transmitted from the grand master <NUM> using, for example, an oscilloscope. In the example illustrated in <FIG>, the evaluator <NUM> compares black burst (BB) signals from the grand master <NUM> and the device <NUM> to measure the phase difference and the frequency shift. The strength of the network load in which the phase difference or the frequency deviation that can be observed by the evaluator <NUM> is within the allowable value defined in SMPTE <NUM>-<NUM> is defined as the network environment resistance index information.

That is, the network environment resistance index information in the present disclosure can be defined as information indicating the accuracy of time synchronization of the PTP compatible device having the BC function corresponding to the network environment, or network environment information indicating the network environment in a case where the accuracy of time synchronization of the PTP compatible device having the BC function is equal to or higher than a predetermined value.

The network environment information includes network load information indicating the strength of the network load related to time synchronization of the PTP compatible device having the BC function. The strength of the network load is a value defined on the basis of values such as the magnitude of delay distribution such as a jitter and packet loss defined by a general network tester, and the ratio of the packet loss rate (burst loss, random loss, or the like). That is, packet load information is information defined on the basis of at least one of packet transfer jitter information or packet transfer delay information. In a case where the packet load information is defined on the basis of both the packet transfer jitter information and the packet transfer delay information, the network environment resistance index information is defined according to the following Expression (<NUM>) so that the packet transfer jitter information has a higher contribution rate than the packet transfer delay information. [Expression <NUM>] <MAT>.

In the above Expression (<NUM>), α > β represents that the packet transfer jitter information has a higher contribution rate than the packet transfer delay information. Supplemental description will be made on the contribution rates of the packet transfer jitter and the packet transfer delay. In particular, in a case where the delay in a transfer direction from the PTP master to the PTP slave is different from the delay in a transfer direction from the PTP slave to the PTP master, the contribution rate of the packet transfer jitter information in the network environment resistance index information of the PTP compatible device increases. Furthermore, a component of an absolute delay amount in the packet transfer delay is canceled by authority of the PTP, and thus it is not taken into consideration much in the network environment resistance index information.

Note that, in this technical field, the packet transfer jitter may be expressed as "±<NUM> milliseconds" or may be expressed by distribution. Therefore, the packet transfer jitter may be handled as data indicating the packet transfer jitter width (for example, if ±<NUM> milliseconds, the packet transfer jitter width is <NUM> milliseconds). In addition, a round trip time (RTT) may be used for the packet transfer delay.

Furthermore, the network environment information may include information indicating the number of hops (the number of devices that need to pass through the PTP path) from the target PTP compatible device to the grand master. A point of setting the time synchronization system on the basis of the network environment resistance index information in consideration of the number of hops will be described in Section G below.

In the present disclosure, a management device manages the network environment resistance index information measured for each PTP compatible device having the BC function included in the time synchronization system in association with the PTP compatible device. The management device may acquire the network environment resistance index information measured for each PTP compatible device from the evaluator <NUM>, but the management device may be equipped with the evaluator <NUM>.

In this section, a procedure of selecting a PTP slave and a procedure of performing time synchronization using the network environment resistance index information according to the present disclosure will be described.

<FIG> schematically illustrates a configuration example of a time synchronization system <NUM> including the management node <NUM>. However, in <FIG>, in order to simplify the drawing, only a base <NUM> that is a non-GM base not having a grand master is drawn, and a GM base having a grand master and a network line (or provided on the base <NUM>) sandwiched between the GM base and the base <NUM> are not illustrated.

The management node <NUM> corresponds to the "management device" described above, and manages the network environment resistance index information for the provided network line of each PTP compatible device having the BC function and existing in the time synchronization system <NUM> in association with the PTP compatible device. Furthermore, the management node <NUM> determines on/off of the BC function corresponding to the port of each PTP compatible device having the BC function and selects a site PTP master in the site. The location of the management node <NUM> is not limited as long as it is a place where Internet Protocol (IP) access to each device of the time synchronization system <NUM> can be performed. For example, the management node <NUM> may be installed in any site in the time synchronization system <NUM>.

The base <NUM> includes four devices <NUM> to <NUM> and a network relay <NUM> connected to another site (not illustrated in <FIG>) via a provided network line (not illustrated in <FIG>). Each of the devices <NUM> to <NUM> and the network relay <NUM> is a PTP compatible device having the BC function, and is a target for evaluating the network environment resistance index information. The devices <NUM> to <NUM> having the BC function are desirably time synchronization devices that are connected through the external analog interface and perform time synchronization. On the other hand, the device <NUM> is a PTP compatible device not having the BC function, and is not evaluated for the network environment resistance index information. Although depending on the application field of the time synchronization system <NUM>, many of devices such as a broadcasting device and a server correspond to PTP compatible devices not having the BC function. The number of PTP compatible devices not having the BC function is the largest. Furthermore, it is also assumed that the device <NUM> is not a time synchronization device.

<FIG> illustrates a state in which the management node <NUM> manages the network environment resistance index information of each device in association with the device. The location of the evaluator (not illustrated in <FIG>) is not limited as long as it can measure the network environment resistance index information of each device in the time synchronization system <NUM>. For example, the functions of the evaluator in the management node <NUM> may be implemented.

In <FIG>, the evaluator measures the network environment resistance index information by reproducing a provided network line (not illustrated in <FIG>) by the network emulator for each of the devices <NUM> to <NUM> and the network relay <NUM> as evaluation targets for the network environment resistance index information. Details of the measurement method have already been described in the section C described above, and thus will be omitted here. The evaluator outputs the measured network environment resistance index information of each device <NUM> to <NUM> and the network relay <NUM> to the management node <NUM>. Then, the management node <NUM> manages the network environment resistance index information of each device <NUM> to <NUM> acquired from the evaluator in association with each device <NUM> to <NUM> and the network relay <NUM>. The function of the management node <NUM> can be achieved, for example, in a form in which an information processing apparatus such as a computer executes a predetermined computer program.

The network environment resistance index information is as described in detail in section C described above. A method of expressing the network environment resistance index information is arbitrary. Hereinafter, in order to simplify the description, it is assumed that the network environment resistance index information is expressed by three types of index values of "L (Low)", "M (Middle)", and "H (High)".

In the time synchronization system <NUM>, evaluation results of the network environment resistance index information of M, M, H, and L are measured for the device <NUM>, the device <NUM>, the device <NUM>, and the network relay <NUM>, respectively. The management node <NUM> manages the network environment resistance index information in association with each of the device <NUM>, the device <NUM>, and the device <NUM>. Furthermore, the management node <NUM> selects a device to be a site PTP master by enabling the BC function in the base <NUM> on the basis of each device <NUM> to <NUM> that is the PTP compatible device having the BC function and the network environment resistance index information of the network relay <NUM>. The site PTP master performs time synchronization as a PTP slave with respect to the device on the GM base side, and then provides the reference time in its own base. In the example illustrated in <FIG>, the device <NUM> whose network environment resistance index information indicates a highest index value "H" can be set as the site PTP master in the base <NUM>.

<FIG> illustrates an operation example of selecting a PTP slave and performing intra-site synchronization in the time synchronization system <NUM>. However, in <FIG>, a GM base <NUM> having a grand master and a network line <NUM> sandwiched between the GM base <NUM> and the base <NUM> are additionally illustrated. The GM base <NUM> includes a grand master <NUM> and a network relay <NUM>.

Time synchronization in the GM base <NUM> is achieved by a procedure similar to that of the time synchronization system <NUM> described above. In the example illustrated in <FIG>, on the base <NUM> side, the network relay <NUM> whose network environment resistance index information is "L" is selected as the site PTP master. Thus, the network relay <NUM> performs time synchronization as a PTP slave with respect to the network device <NUM> in the GM base <NUM>, and operates as a PTP master with respect to the devices <NUM> to <NUM> in the base <NUM>, and the devices <NUM> to <NUM> performs time synchronization with the network relay <NUM>. However, even if the BC function of the network relay <NUM> is enabled, the jitter of the wide area network line <NUM> cannot be removed because the network environment resistance index is not sufficient, and the devices <NUM> to <NUM> cannot perform the time synchronization with the network device <NUM> in the GM base <NUM> with high accuracy. In <FIG>, a "×" mark is attached to a device that cannot perform time synchronization.

Accordingly, as illustrated in <FIG>, the management node <NUM> selects the device <NUM> associated with the highest index value "H" of the network environment resistance index information in the base <NUM> as the site PTP master in the base <NUM>, and enables the BC function of the device <NUM>. Furthermore, the management node <NUM> turns off the BC function corresponding to two ports of the network relay <NUM> to be the PTP path connecting the device <NUM> and the GM base <NUM>. In <FIG>, the port of the network relay <NUM> with the BC function turned off is represented in a blank state in which neither "M" indicating that it operates as a PTP master with respect to the peer nor "S" indicating that it operates as a PTP slave with respect to the peer is written. Thus, the device <NUM> as a PTP slave can perform time synchronization with the network relay <NUM> on the GM base <NUM> side as a PTP master.

Subsequently, as illustrated in <FIG>, the management node <NUM> selects the device <NUM> that is the site PTP master and the device <NUM> capable of time synchronization through the external analog interface as the PTP master of another domain (in <FIG>, the ports are colored with different shades of gray for each time synchronization domain). This is because if the device <NUM> remains in the same domain as that of the GM base <NUM>, the device <NUM> receives, as a PTP slave, the PTP packet from which the jitter is not removed from the GM base <NUM> and performs the time synchronization inaccurately. In this case, the device <NUM> gives priority to the time information using the PTP packet over the accurate time information acquired from the device <NUM> through the analog interface. Therefore, it is necessary to prevent the device <NUM> having the medium network environment resistance index information from directly performing the time synchronization with the network relay <NUM> in the GM base <NUM>.

Subsequently, as illustrated in <FIG>, the management node <NUM> changes the domains of the other devices <NUM> and <NUM> in the base <NUM> to the same domains as that of the device <NUM>. Thus, it is possible to prevent the devices <NUM> and <NUM> from receiving the PTP packet from which the jitter is not removed from the network relay <NUM> in the GM base <NUM> and performing the time synchronization. It is necessary to prevent the devices <NUM> and <NUM> associated with the medium index value "M" of the network environment resistance index information from being directly time-synchronized with the network relay <NUM>.

Subsequently, as illustrated in <FIG>, the management node <NUM> changes the domain using the PTP path to which the device <NUM> after changing the domain is connected. That is, the network relay <NUM> switches to operate as a PTP slave to the device <NUM> (in the diagram, "S" indicating that it is a PTP slave is entered in the port connected to the device <NUM>). Consequently, the network relay <NUM> can perform, as a PTP slave, time synchronization with the device <NUM> set as the site PTP master.

Subsequently, as illustrated in <FIG>, the management node <NUM> changes the domain through the path to which the devices <NUM> and <NUM> after the domain change are connected. In the diagram, among the plurality of ports included in the network relay <NUM>, the ports respectively connected to the devices <NUM> and <NUM> are colored in gray of the same shade to represent the same domain as that of the device <NUM>. With this domain change, the devices <NUM> and <NUM> can perform time synchronization with the network relay <NUM> time-synchronized with the device <NUM> as PTP slaves.

A result of performing on/off setting of the BC function and domain setting corresponding to the port of each device in the time synchronization system <NUM> through the operation procedure illustrated in <FIG> is as illustrated in <FIG>.

Referring to <FIG>, in the non-GM base <NUM>, the device <NUM> whose network environment resistance index information has the highest index value "H" belongs to the same domain as that of the GM base <NUM> and can perform time synchronization with the network device <NUM>.

Furthermore, other devices in the non-GM base <NUM> whose network environment resistance index information has a medium or lower index value do not directly perform time synchronization with the PTP packet from which the jitter is not removed from the network relay <NUM> in the GM base <NUM>. The device <NUM> can be connected to the device <NUM> through the external analog interface to perform time synchronization. Furthermore, the device <NUM> is selected as another PTP master in the non-GM base <NUM>, and the PTP path <NUM> connecting the PTP master and the PTP slave is determined in this another domain.

Referring to <FIG>, the network relay <NUM> is set to operate as a PTP slave for the device <NUM> (in the diagram, "S" indicating that it is a PTP slave is entered in the port connected to the device <NUM>), and thus the network relay <NUM> performs time synchronization with the device <NUM>. Furthermore, the network relay <NUM> is set to operate as a PTP master for the device <NUM> and the device <NUM> (in the diagram, "M" indicating that it is a PTP master is entered in the ports connected to the device <NUM> and the device <NUM>), and thus the device <NUM> and the device <NUM> perform time synchronization with the network relay <NUM>.

In this manner, all devices <NUM> to <NUM> in the non-GM base <NUM> can synchronize with the reference time.

According to the present disclosure, in a case where a failure occurs in a time synchronization system, the on/off setting of the BC function corresponding to each port of each PTP compatible device having the BC function, domain setting, and the like are dynamically changed, and time synchronization of the entire system can be maintained even after the failure occurs. For example, in a case where a failure occurs in at least one of a plurality of PTP compatible devices having the BC function and existing in the non-GM base, a PTP compatible device that performs time synchronization with a PTP compatible device of the GM base is reselected on the basis of the network environment resistance index information of each of the remaining PTP compatible devices having the BC function in which no failure has occurred.

A dynamic setting change process when a failure occurs will be described with a time synchronization system <NUM> illustrated in <FIG> as an example. The illustrated time synchronization system <NUM> includes two sites including a first base <NUM> that is a GM base and a second base <NUM> that is a non-GM base, and includes a management node <NUM>. The first base <NUM> includes a grand master <NUM> and a network relay <NUM>. Furthermore, the second base <NUM> includes devices <NUM> to <NUM> and a network relay <NUM>. Furthermore, the sites are connected by a wide area network line <NUM>.

The management node <NUM> corresponds to the "management device" described above, and manages the network environment resistance index information for the provided wide area network line <NUM> of each PTP compatible device having the BC function and existing in the time synchronization system <NUM> in association with the PTP compatible device, and performs determination of on/off of the BC function corresponding to each port of each PTP compatible device having the BC function, selection of the site PTP master in the site, and setting of the domain.

The devices <NUM> to <NUM> and the network relay <NUM> in the second base <NUM> are both PTP compatible devices, and the devices <NUM> to <NUM> and the network relay <NUM> have the BC function, but the device <NUM> does not have the BC function. Therefore, the devices <NUM> to <NUM> and the network relay <NUM> are management targets of the network environment resistance index information by the management node <NUM>, but the device <NUM> is not a management target.

In the state illustrated in <FIG>, the device <NUM> is selected as the site PTP master of the second base <NUM>, belongs to the same domain as that of the GM base <NUM>, and is time-synchronized with the network device <NUM> in the GM base <NUM>. Furthermore, other devices in the non-GM base <NUM> are set in another domain different from that of the GM base <NUM>. In this another domain, the device <NUM> is selected as the PTP master. Furthermore, the network relay <NUM> is set to operate as a PTP slave for the device <NUM> (in the diagram, "S" indicating that it is a PTP slave is entered in the port connected to the device <NUM>), and is set to operate as a PTP master for the device <NUM> and the device <NUM> (in the diagram, "M" indicating that it is a PTP master is entered in each of the device <NUM> and the port connected to the device <NUM>).

The location of the management node <NUM> is not limited as long as it is a place where IP access to each device of the time synchronization system <NUM> can be performed. The management node <NUM> can detect whether a failure has occurred in each device in the time synchronization system <NUM> by IP communication check using a ping command or the like. In the example illustrated in <FIG>, the management node <NUM> detects a failure of the device <NUM>.

The device <NUM> before the failure has been selected as the current site PTP master of the second base <NUM>, belongs to the same domain as that of the GM base <NUM>, and is time-synchronized with the network device <NUM> in the GM base <NUM>. Accordingly, the management node <NUM> compares the network environment resistance index information associated with each of the other devices <NUM> and <NUM> in which no failure has occurred and the network relay <NUM>, and selects the next candidate of the site PTP master. In the example illustrated in <FIG>, the management node <NUM> sets the device <NUM> associated with the next highest index value "M" of the network environment resistance index information as the next candidate of the site PTP master. Then, the management node <NUM> turns off the BC function corresponding to the port of the network relay <NUM> that becomes the PTP path connecting the device <NUM> that is the next candidate for the site PTP master and the GM base <NUM>.

Next, as illustrated in <FIG>, the management node <NUM> changes the setting of the device <NUM> to the PTP slave in the same domain as that of the GM base <NUM>. Thus, the device <NUM> can perform time synchronization with the network device <NUM> on the GM base <NUM> side.

Next, as illustrated in <FIG>, the management node <NUM> sets again the device <NUM> capable of time synchronization through an analog interface external to the device <NUM> as the PTP master of another domain. By changing the domain, the device <NUM> having the medium network environment resistance index information is prevented from receiving the PTP packet from which the jitter is not removed from the network relay <NUM> in the GM base <NUM> and performing the time synchronization. Furthermore, the network relay <NUM> is set again to operate as a PTP slave for the device <NUM> (in the diagram, the port connected to the device <NUM> is changed from "M" to "S"). Consequently, the network relay <NUM> can perform, as a PTP slave, time synchronization with the device <NUM> set as the PTP master of another domain. Furthermore, the device <NUM> can perform, as a PTP slave, time synchronization with the network relay <NUM> time-synchronized with the device <NUM>.

Through the operation procedure when a failure occurs as illustrated in <FIG>, on/off of the BC function and the domain corresponding to each port of each device in the time synchronization system <NUM> are reset as illustrated in <FIG>.

Referring to <FIG>, in the non-GM base <NUM>, a device <NUM> set as a new site PTP master on the basis of the associated network environment resistance index information can be changed to the same domain as that of the GM base <NUM> and perform time synchronization with the network device <NUM> in the GM base <NUM>. Further, the device <NUM> can be connected to the device <NUM> through the external analog interface to perform time synchronization. In addition, the device <NUM> is reset to the PTP master of another domain in the non-GM base <NUM>, and the network relay <NUM> performs time synchronization with the device <NUM>. Furthermore, the device <NUM> performs time synchronization with the network relay <NUM>.

In this manner, in a case where a failure occurs in the device in the non-GM base <NUM> (the device <NUM> set as the site PTP master), each device in the non-GM base <NUM> can synchronize with the reference time by resetting on/off of the BC function and the domain corresponding to each port of each device in the time synchronization system <NUM>.

According to the present disclosure, on the basis of the network environment resistance index information of each PTP compatible device in a site (for example, a non-GM base), the BC function of each PTP compatible device having the BC function in the time synchronization system is enabled, and dynamic setting such as selection of a PTP master in the non-GM base is performed. The dynamic setting using the network environment resistance index information is performed at various timings such as at the time of start of operation of the system (or when the system is started), at the time of change in the network environment, at the time of change in the system configuration, and at the time of change in the network environment resistance index information. The change in the system configuration includes a change in the network environment, a change in the network environment resistance index information of at least a part of PTP compatible devices in the non-GM base, replacement of the devices in the non-GM base, increase of the devices, and removal of some devices.

Hereinafter, a process of performing dynamic setting using the network environment resistance index information at each timing will be described using the time synchronization system <NUM> illustrated in <FIG> as an example.

At the time of start of operation, for example, the devices <NUM> to <NUM> corresponding to use equipment such as a broadcasting device are brought into a studio corresponding to the second base <NUM> that is a non-GM base, each connected to the network relay <NUM>, and prepared before the start of operation. <FIG> illustrates an operation example of the time synchronization system <NUM> when use of the studio is started, that is, when operation of the second base <NUM> is started.

In the time synchronization system <NUM>, the devices <NUM> to <NUM> and the network relay <NUM> are PTP compatible devices having the BC function, but the device <NUM> is a PTP compatible device not having the BC function. Therefore, the devices <NUM> to <NUM> and the network relay <NUM> are management targets of the network environment resistance index information by the management node <NUM>, but the device <NUM> is not a management target (as described above). Before the start of the system operation, all the BC functions corresponding to the ports of the respective devices in the second base <NUM> are turned off, and the master/slave and the domain are not set.

An evaluator (not illustrated) reproduces the provided wide area network line <NUM> for each of the devices <NUM> to <NUM> and the network relay <NUM> as evaluation targets for the network environment resistance index information, and measures the network environment resistance index information. Details of the measurement method have already been described in the section C described above, and thus will be omitted here. In the example illustrated in <FIG>, the network environment resistance index information of M, M, H, and L is measured for the device <NUM>, the device <NUM>, the device <NUM>, and the network relay <NUM>, respectively. The evaluator outputs the measured network environment resistance index information of each device <NUM> to <NUM> and the network relay <NUM> to the management node <NUM>.

The management node <NUM> manages the network environment resistance index information of each device <NUM> to <NUM> acquired from the evaluator in association with each device <NUM> to <NUM> and the network relay <NUM>. Then, when the use of the studio is started, that is, when the operation of the second base <NUM> is started, the management node <NUM> sets the device <NUM> associated with the highest index value "H" of the network environment resistance index information in the second base <NUM> as the site PTP master.

In the studio corresponding to the second base <NUM> which is a non-GM base, the devices <NUM> to <NUM> corresponding to use equipment such as a broadcasting device are connected to the network relay <NUM>. Then, at the time of start of operation, the environment of the wide area network line <NUM> is in a normal state, and time synchronization can be performed with respect to the network relay <NUM> on the GM base <NUM> side in any of the devices <NUM> to <NUM> having the BC function. In such a case, it is assumed that the management node <NUM> starts using the studio by arbitrarily setting the device <NUM> as the site PTP master and performing time synchronization of each device in the non-GM base <NUM>, without knowing the network environment resistance index information of each device <NUM> to <NUM>.

However, during use of the studio, that is, during operation of the second base <NUM>, due to a dynamic change in the line status such as an increase in congestion degree of the wide area network line <NUM>, as illustrated in <FIG>, there is a case where the device <NUM> currently set as the site PTP master cannot perform time synchronization on the second base <NUM>. In <FIG>, a mark "×" is attached to the device <NUM> that cannot perform the time synchronization.

During use of the studio, that is, during operation of the second base <NUM>, the management node <NUM> constantly monitors congestion of the provided wide area network line <NUM>. The management node <NUM> can monitor congestion of the wide area network line <NUM> on the basis of, for example, a result of measuring a jitter or a packet loss rate in the wide area network line <NUM>.

Accordingly, upon detecting that the time synchronization cannot be performed with high accuracy in the second base <NUM> due to the increase in the congestion degree of the wide area network line <NUM>, the management node <NUM> compares the network environment resistance index information associated with each of the other devices <NUM> and <NUM> and the network relay <NUM> in the second base, and selects the next candidate of the site PTP master. In the example illustrated in <FIG>, the management node <NUM> selects the device <NUM> with which the next highest index value "M" of the network environment resistance index information is associated as the next candidate for the site PTP master, and changes the setting of PTP master/PTP slave of each device and the on/off setting of the BC function corresponding to the port of each device.

The system configuration may change after the use of the studio is started, that is, after the operation of the second base <NUM> is started. The change in the system configuration here includes replacement or removal of some used equipment, addition of equipment, change in network connection between pieces of equipment, and the like. <FIG> illustrates an example in which the network relay <NUM> is replaced with a new network relay <NUM> in the time synchronization system illustrated in <FIG>. It is assumed that the new network relay <NUM> is a PTP compatible device having the BC function and is an evaluation target of the network environment resistance index information by the management node <NUM>.

The evaluator (not illustrated) reproduces the provided wide area network line <NUM>, measures the network environment resistance index information of the network relay <NUM>, and outputs the network environment resistance index information to the management node <NUM>. In the example illustrated in <FIG>, the network environment resistance index information of "H (High)" is measured for the new network relay <NUM>. The management node <NUM> manages the network environment resistance index information acquired from the evaluator in association with the new network relay <NUM>. Note that, also in a case where any of the devices <NUM> to <NUM> is replaced or in a case where a new PTP compatible device having the BC function is added to the second base, the network environment resistance index information regarding the new device is similarly measured and associated with the device.

Then, the management node <NUM> compares the network environment resistance index information associated with each device <NUM> to <NUM> and the new network relay <NUM>, and resets the new network relay <NUM> associated with the highest index value "H" of the network environment resistance index information in the second base <NUM> as the site PTP master.

As described in item F-<NUM> described above, the network environment resistance index information of each device used in the site is measured in advance before the start of operation, and the management node <NUM> manages the network environment resistance index information in association with the device. However, the network environment resistance index information once measured is not necessarily constant, and the network environment resistance index information may change with the lapse of time depending on the device. For example, while the time required before time synchronization is very long, there may be a device in which settings can be changed so that the network environment resistance index information becomes high once the time synchronization is performed.

In the example illustrated in <FIG>, before the start of the system operation, pieces of the network environment resistance index information of M, M, M, and L are measured for the device <NUM>, the device <NUM>, the device <NUM>, and the network relay <NUM>, respectively, but after temporary time synchronization is performed in the second base, the network environment resistance index information of the device <NUM> changes from "M" to the highest index value "H". A method for detecting a temporal change in the network environment resistance index information of each device is arbitrary. For example, the network environment resistance index information of each device may be periodically measured using an evaluator during system operation. Alternatively, the management node <NUM> may be notified of the network environment resistance index information as setting information of the device.

Then, upon detecting that the setting of the network environment resistance index information of the device <NUM> is changed from "M" to the highest index value "H" after the time synchronization is performed in the second base <NUM>, the management node <NUM> resets the device <NUM> to the site PTP master.

The network environment resistance index information based on the measurement method described in item C described above is information indicating easiness of time synchronization measured for each device with respect to the network line interposed between the sites. However, the easiness of time synchronization may vary depending on the network configuration in the site where the device is installed.

For example, there is a case where network relays are cascaded to install more devices in a site. In such a case, the number of hops to the grand master varies depending on the installation location of the device. An increase in the number of hops causes a jitter and packet loss, and it is assumed that the resistance of the device to the network environment or the easiness of time synchronization is reduced.

The influence of the network configuration (the number of hops to the grand master) on the time synchronization will be considered with a time synchronization system <NUM> illustrated in <FIG> as an example. The illustrated time synchronization system <NUM> includes two sites, a first base <NUM> that is a GM base and a second base <NUM> that is a non-GM base, and includes a management node <NUM>. The first base <NUM> includes a grand master <NUM> and a network relay <NUM>. Furthermore, the second base <NUM> includes devices <NUM> to <NUM> and two network relays <NUM> and <NUM>.

Describing the network configuration in the second base <NUM>, the network relay <NUM> is connected to the first base <NUM> through a wide area network line <NUM>. Furthermore, the network relay <NUM> is cascade-connected to the network relay <NUM>. The device <NUM> and the device <NUM> are connected to the network relay <NUM>, and the device <NUM> and the device <NUM> are connected to the network relay <NUM>.

Each of the devices <NUM> to <NUM> is a PTP compatible device having the BC function, and is an evaluation target of the network environment resistance index information. It is assumed that the evaluator (not illustrated) reproduces the provided wide area network line <NUM> to measure the network environment resistance index information of respective devices <NUM> to <NUM>, and obtains respective results of M, M, H, and L. The evaluator outputs the measured network environment resistance index of the respective devices <NUM> to <NUM> to the management node <NUM>, and the management node <NUM> manages respective pieces of the network environment resistance index information in association with the devices <NUM> to <NUM>.

In a case where the number of hops to the grand master is not considered, the management node <NUM> sets the device <NUM> associated with the highest index value "H" of the network environment resistance index information in the second base <NUM> as the site PTP master. However, since the device <NUM> is connected to the network relay <NUM> cascade-connected to the network relay <NUM> and has a large number of hops, the time synchronization with the network device <NUM> in the GM base <NUM> may not be possible due to the jitter generated in the device <NUM>. In <FIG>, a mark "×" is attached to the device <NUM> that cannot perform the time synchronization.

On the other hand, the network environment resistance index information of the device <NUM> is "M", which is lower than that of the device <NUM>. However, since the device <NUM> is connected to the network relay <NUM>, has a small number of hops to the grand master <NUM>, and is closer to the grand master <NUM>, time synchronization with the grand master <NUM> is easier than with the device <NUM>. Accordingly, as illustrated in <FIG>, the management node <NUM> adds the number of hops to the grand master to the network environment resistance index information measured for each device (see paragraph <NUM>), and selects the device <NUM> as the site PTP master in consideration of the number of hops to the grand master <NUM>. Thus, the device <NUM> as a PTP slave can perform time synchronization with the network relay <NUM> on the first base <NUM> side as the PTP master.

Subsequently, as illustrated in <FIG>, the management node <NUM> sets the device <NUM> capable of time synchronization with the device <NUM> through the external analog interface as the PTP master of another domain (in <FIG>, ports are colored with different shades of gray for each time synchronization domain). This is to prevent the device <NUM> from receiving the PTP packet from which the jitter is not removed from the network relay <NUM> in the first base <NUM> that is the GM base and performing time synchronization if the original domain is maintained. It is necessary to prevent time synchronization of the device <NUM> with the network relay <NUM>. Furthermore, at the same time, the management node <NUM> sets the network relay <NUM> to operate as a PTP slave for the device <NUM> (in the diagram, "S" indicating that it is a PTP slave is entered in the port connected to the device <NUM>). Consequently, the network relay <NUM> can perform, as a PTP slave, time synchronization with the device <NUM> set as the PTP master.

Subsequently, as illustrated in <FIG>, the management node <NUM> sets the network relay <NUM> as the PTP master of the another domain described above (in the diagram, "M" indicating that it is a PTP master is entered in one of the ports cascade-connected to the network relay <NUM> among the plurality of ports included in the network relay <NUM>). Furthermore, the management node <NUM> sets the network relay <NUM> as the PTP slave of the another domain described above (in the diagram, "S" indicating that it is a PTP slave is entered in one of the ports cascade-connected to the network relay <NUM> among the plurality of ports included in the network relay <NUM>). Consequently, the network relay <NUM> can perform time synchronization with the network relay <NUM>. Moreover, the management node <NUM> sets the network relay <NUM> as the PTP master in the another domain described above (in the diagram, "M" indicating that it is a PTP master is entered in each of the ports connected to the device <NUM> and the device <NUM> among the plurality of ports included in the network relay <NUM>), and sets each of the devices <NUM> and <NUM> as the PTP slave in the another domain described above (in the diagram, "S" indicating that it is a PTP slave is entered in each of the ports of the device <NUM> and the device <NUM>). Consequently, the device <NUM> and the device <NUM> can perform time synchronization with the network relay <NUM>.

Through the operation procedure as illustrated in <FIG>, on/off setting of the BC function and the domain setting corresponding to the port of each device in the time synchronization system <NUM> are as illustrated in <FIG>.

Referring to <FIG>, the device <NUM> with a small number of hops to the grand master <NUM> belongs to the same domain as that of the first base <NUM> that is the GM base and can perform time synchronization with the network device <NUM> in the GM base <NUM>.

Furthermore, the device <NUM> can perform time synchronization with the device <NUM> through the external analog interface. Then, the management node <NUM> sets the device <NUM> as a site PTP master of another domain, sets the network relay <NUM> as a PTP slave for the device <NUM>, sets the network relay <NUM> as a PTP slave for the network relay <NUM>, and sets the device <NUM> and the device <NUM> as PTP slaves for the network relay <NUM>. Thus, time synchronization can be performed even in another domain set in the second base <NUM>.

In this manner, regardless of the network configuration in the second base <NUM> that is a non-GM base, all the devices <NUM> to <NUM> can perform time synchronization with the network devices <NUM> in the GM base <NUM>.

In this section, a setting process for time synchronization performed by the management node as a main body in the time synchronization system will be described.

<FIG> illustrates an example of a setting processing procedure for time synchronization performed in the time synchronization system in the form of a flowchart. This processing procedure can be applied to achieve time synchronization in a time synchronization system that includes various network configurations including a GM base and one or more non-GM bases and including a management node that manages the network environment resistance index information of a device in each site.

First, the management node collects the network environment resistance index information of each PTP compatible device having the BC function (step S2701).

Then, the management node checks whether there is a device having a network environment resistance index and capable of performing time synchronization with the grand master for the quality of the provided network line (step S2702).

Here, in a case where there is no device having a network environment resistance index and capable of performing time synchronization (No in step S2702), it is necessary to take a measure for enabling time synchronization. In the processing procedure illustrated in <FIG>, a system administrator or the like is suggested to improve the quality of the network line or introduce or replace with a device having a higher network environment resistance index (step S2703), and the processing returns to step S2701.

On the other hand, in a case where there is a device having a network environment resistance index and capable of performing time synchronization (Yes in step S2702), the management node sets the BC function corresponding to the port on the PTP path connecting the device having the highest network environment resistance index information and the device to be the PTP master to off (step S2704). Consequently, the above-described device having the highest network environment resistance index information can perform, as the site PTP master, time synchronization with the device such as the grand master.

Next, the management node collects information of the above-described device (site PTP master) having the highest network environment resistance index information and a device that can perform time synchronization through the external analog interface (step S2705), and checks whether or not such a device exists (step S2706). The device to be checked in steps S2705 and S2706 is a PTP compatible device having the BC function.

In a case where a device that can perform time synchronization is not found through the external analog interface (No in step S2706), it is necessary to further take a measure for enabling time synchronization. In the processing procedure illustrated in <FIG>, the system administrator or the like is suggested to add the PTP compatible device having the BC function or change the connection of the external analog interface (step S2707), and the processing returns to step S2705.

In a case where the corresponding device has been found (Yes in step S2707), the management node changes the device to the PTP master and newly sets a domain (step S2708).

Then, the management node newly sets a domain in the port connected to the device set as the PTP master in step S2708 (step S2709), and ends this processing. In the newly set domain, each device can perform time synchronization with the PTP master. Therefore, time synchronization can be implemented in the entire time synchronization system.

<FIG> illustrates another example of a setting processing procedure for time synchronization performed in the time synchronization system in the form of a flowchart. This processing procedure can be applied to achieve time synchronization when a failure occurs in a time synchronization system that includes various network configurations including a GM base and one or more non-GM bases and including a management node that manages the network environment resistance index information of a device in each site.

First, the management node examines the status of a device in which the BC function does not normally operate among the PTP compatible devices having the BC function or a network line (step S2801), and checks whether there is a device that does not perform time synchronization exists (step S2802).

Here, in a case where there is no device that does not perform time synchronization (No in step S2802), the processing returns to step S2801.

On the other hand, in a case where there is a device that does not perform time synchronization (Yes in step S2802), the management node collects the network environment resistance index information of each PTP compatible device having the BC function (step S2803).

Then, the management node checks whether there is a device having a network environment resistance index and capable of performing time synchronization with the grand master for the quality of the provided network line (step S2804).

Here, in a case where there is no device having a network environment resistance index and capable of performing time synchronization (No in step S2804), it is necessary to take a measure for enabling time synchronization. In the processing procedure illustrated in <FIG>, a system administrator or the like is suggested to improve the quality of the network line or introduce or replace with a device having a higher network environment resistance index (step S2805), and the processing returns to step S2803.

On the other hand, in a case where there is a device having a network environment resistance index and capable of performing time synchronization (Yes in step S2804), the management node sets the BC function corresponding to the port on the PTP path connecting the device having the highest network environment resistance index information and the device to be the PTP master to off (step S2806). Consequently, the above-described device having the highest network environment resistance index information can perform, as the site PTP master, time synchronization with the device such as the grand master.

Next, the management node collects information of the above-described device (site PTP master) having the highest network environment resistance index information and a device that can perform time synchronization through the external analog interface (step S2807), and checks whether or not such a device exists (step S2808). The device to be checked in steps S2807 and S2808 is a PTP compatible device having the BC function.

In a case where a device that can perform time synchronization is not found through the external analog interface (No in step S2808), it is necessary to further take a measure for enabling time synchronization. In the processing procedure illustrated in <FIG>, the system administrator or the like is suggested to add the PTP compatible device having the BC function or change the connection of the external analog interface (step S2809), and the processing returns to step S2807.

In a case where the corresponding device has been found (Yes in step S2808), the management node changes the device to the PTP master and newly sets a domain (step S2810).

Then, the management node newly sets a domain in the port connected to the device set as the PTP master in step S2810 (step S2811), and ends this processing. In the newly set domain, each device can perform time synchronization with the PTP master. Therefore, even in a case where a failure occurs, the management node can implement time synchronization in the entire time synchronization system by changing the setting of the BC function or the setting of the domain on the basis of the network environment resistance index information.

The effects of the present disclosure will be summarized.

The present disclosure has been described in detail above with reference to specific embodiments.

In the present description, the embodiment in which the present disclosure is applied to a system that performs time synchronization on a network has been mainly described.

The present disclosure can be applied to evaluate a possibility to use the BC function of the PTP compatible device when time synchronization is performed in a base and between bases. Furthermore, the present disclosure can also be used when evaluating resistance of each network relay to a network environment in various types of network systems.

Claim 1:
An information processing apparatus comprising
a control unit (<NUM>) that determines whether a device has a boundary clock function with network environment resistance index information indicating that an accuracy of time synchronization of the boundary clock function with respect to the network environment is equal to or more than a predetermined value,
wherein the information processing apparatus is characterized by that the control unit is configured to control the boundary clock function to turn on/off on the basis of the network environment resistance index information.