Patent Publication Number: US-11381458-B2

Title: Network management device, control circuit, and recording medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of International Application PCT/JP2017/042537, filed on Nov. 28, 2017, and designating the U.S., the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a network management device that manages the configuration of a wireless ad hoc network. 
     2. Description of the Related Art 
     In maintaining or managing a wireless ad hoc network, knowing the configuration of that wireless ad hoc network is of importance to the administrator. A network configuration estimation device may be used to allow the administrator to know the configuration of a wireless ad hoc network. Japanese Patent No. 6091378 discloses a network configuration estimation device that analyzes the emission patterns of radio waves emitted by respective nodes in a wireless ad hoc network, determines that a pair of nodes that each emit a radio wave within a certain time period has a link therebetween, that is, such pair of nodes are nodes adjacent to each other, and thus estimates the configuration of the wireless ad hoc network. 
     However, the above conventional network configuration estimation device may determine that multiple nodes, located distant from each other having no link therebetween in reality, have a link therebetween when the nodes each emit a radio wave incidentally within a certain time period. Or, the above conventional network configuration estimation device may determine that a pair of nodes located adjacent to each other has no link therebetween due to no radio wave being emitted by the nodes during observation. This presents a problem of decrease in accuracy of estimation of the network configuration. 
     The present invention has been made in view of the foregoing, and it is an object of the present invention to provide a network management device that provides reduction in decrease in accuracy of estimation of the network configuration. 
     SUMMARY OF THE INVENTION 
     To solve the aforementioned problems and achieve the object, a network management device according to the present invention includes: a metric calculation unit to calculate, using location information of a plurality of nodes constituting a network, metrics for respective combinations of the nodes; a false detection determination unit to determine, using the metrics and using link estimation information being information indicating a combination of the nodes presumed that has a link therebetween, a falsely detected link corresponding to a combination of the nodes indicated as having a link therebetween in the link estimation information, but presumed that has no link therebetween in reality; and a non-detection determination unit to determine, using the metrics and the link estimation information, an undetected link corresponding to a combination of the nodes indicated as having no link therebetween in the link estimation information, but presumed that has a link therebetween in reality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example of the configuration of a network management system according to a first embodiment. 
         FIG. 2  is a diagram illustrating an overview of the processing of the network management system according to the first embodiment. 
         FIG. 3  is a diagram illustrating functional blocks of the network management device according to the first embodiment. 
         FIG. 4  is a chart illustrating an example of location information table according to the first embodiment. 
         FIG. 5  is a chart illustrating an example of link estimation table according to the first embodiment. 
         FIG. 6  is a chart illustrating an example of link presence-absence table according to the first embodiment. 
         FIG. 7  is a diagram illustrating an example of the processing of a false detection determination unit, of a threshold setting unit, and of a non-detection determination unit according to the first embodiment. 
         FIG. 8  is a diagram illustrating an example configuration of the control circuit of the first embodiment. 
         FIG. 9  is a flowchart illustrating an example of control of the network management device according to the first embodiment. 
         FIG. 10  is a diagram illustrating functional blocks of a network management device according to a second embodiment. 
         FIG. 11  is a diagram illustrating an example of the configuration of a network management system according to a third embodiment. 
         FIG. 12  is a diagram illustrating an overview of the processing of the network management device according to the third embodiment. 
         FIG. 13  is a diagram illustrating functional blocks of the network management device according to the third embodiment. 
         FIG. 14  is a diagram illustrating an example of calculation of a significance value, of the network management device according to the third embodiment. 
         FIG. 15  is a flowchart illustrating an example of control of the network management device according to the third embodiment. 
         FIG. 16  is a diagram illustrating functional blocks of a network management device according to a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A network management device according to embodiments of the present invention will be described in detail below with reference to the drawings. Note that these embodiments are not intended to limit the scope of this invention. 
     First Embodiment 
       FIG. 1  is a diagram illustrating an example of the configuration of a network management system according to a first embodiment. A network management system  500  includes a network management device  100 , a network configuration estimation device  200 , and a location information output device  300 . The network management system  500  manages a network. The network management device  100  is connected to each of the network configuration estimation device  200  and the location information output device  300 . The network configuration estimation device  200  generates a link estimation table, which provides information indicating a network configuration, and outputs the link estimation table to the network management device  100 . The location information output device  300  outputs a location information table, which provides information indicating the locations of respective nodes, to the network management device  100 . The link estimation table is also referred to as link estimation information. 
       FIG. 2  is a diagram illustrating an overview of the processing of the network management system  500  according to the first embodiment. The network  10  illustrated in  FIG. 2  is a network managed by the network management system  500 , and is a wireless ad hoc network including nodes N−1 to N−8. Note that although the present embodiment assumes the nodes from nodes N−1 to N−8, the number of the nodes in the present embodiment is not limited. In the present embodiment, the nodes are each referred to as node N when no distinction is made among the nodes N−1 to N−8. In  FIG. 2 , a solid arrow connecting nodes N indicates a normally detected link, which denotes a combination of nodes determined that has a link therebetween in the link estimation information, and presumed that has a link therebetween also in reality. A broken line arrow connecting nodes N indicates a falsely detected link. A dashed-and-dotted line arrow connecting nodes N indicates an undetected link. A falsely detected link denotes a combination of nodes indicated as having a link therebetween in the link estimation information, but presumed that has no link therebetween in reality. Moreover, in other words, a falsely detected link denotes a combination of nodes indicated as having a link therebetween in the link estimation information, which information is nevertheless presumed to be incorrect. An undetected link denotes a combination of nodes indicated as having no link therebetween in the link estimation information, but presumed that has a link therebetween in reality. Moreover, in other words, an undetected link denotes a combination of nodes indicated as having no link therebetween in the link estimation information, which information is nevertheless presumed to be incorrect. 
     In the state illustrated in  FIG. 2( a ) , the network management system  500  has not estimated the configuration of the network  10 , and therefore, relationships of links among the nodes N−1 to N−8 in the network  10  are unknown. As illustrated in  FIG. 2( b ) , estimation of the network configuration of the network  10  by the network configuration estimation device  200  provides a network configuration that represents relationships of links between the nodes included in the network  10 . As illustrated in  FIG. 2( b ) , the network configuration estimated may include a falsely detected link or an undetected link. As illustrated in  FIG. 2( c ) , the network management device  100  of the present embodiment deletes the falsely detected link or links from, and adds the undetected link(s) to, the network configuration estimated by the network configuration estimation device  200 . 
     The network configuration estimation device  200  estimates the condition of a link between nodes based on nodes that are continuously emitting a radio wave, and outputs information on the link estimated, to the network management device  100 . The location information output device  300  outputs node location information to the network management device  100 . The network management device  100  detects a falsely detected link and an undetected link using the link estimation table, which provides information indicating the network configuration estimated by the network configuration estimation device  200 , and the node location information obtained from the location information output device  300 . The network management device  100  deletes the falsely detected link(s) from, and adds the undetected link(s) to, the link estimation table. 
       FIG. 3  is a diagram illustrating functional blocks of the network management device  100  according to the first embodiment. The network management device  100  includes a metric calculation unit  101 , a link determination unit  102 , a false detection determination unit  103 , a threshold setting unit  104 , a non-detection determination unit  105 , and a link correction unit  106 . 
     The metric calculation unit  101  calculates a metric of each of all possible combinations of the nodes using the node location information obtained from the location information table output by the location information output device  300 . The term “combinations of nodes” refers to the combinations of all nodes that can form a link therebetween, and the number of combinations of nodes for M nodes is M×(M−1)/2. A metric is the distance between nodes. Or, a metric is a combination of channel information and distance information. Or, a metric is a propagation loss calculated using a combination of channel information and distance information. Channel information is obtained from topographic information and from measurement data. Topographic information is, for example, three-dimensional map data including the longitude, the latitude, and the altitude for a region containing all the nodes. Measurement data includes, for example, the distance between points and the propagation loss between points measured at multiple points in a region containing all the nodes. A propagation loss is proportional to the square of the distance between nodes. However, in a case in which a shield exists between nodes or in a similar case, the propagation loss will be proportional to an X-th power of the distance between nodes. The channel information is, for example, the value of X obtained from topographic information and from measurement data. The link determination unit  102  generates a link presence-absence table using information in the link estimation table, which is a table listing the combinations of nodes that respectively form links, output by the network configuration estimation device  200 . In addition, the link determination unit  102  generates the link presence-absence table using the metrics of all possible combinations of the nodes calculated by the metric calculation unit  101 . The link presence-absence table is also referred to as link presence-absence information. 
     The false detection determination unit  103  determines that a link having a metric that is an outlier is a falsely detected link, based on the metrics of the detected links in the link presence-absence table. Alternatively, the false detection determination unit  103  determines that a link having a metric that is an outlier is a falsely detected link using link estimation information and metrics. An outlier is, for example, a value of metric of a link beyond the standard deviation calculated on the assumption that the distribution of metric can be classified as a certain distribution. The threshold setting unit  104  stores, as a threshold, the maximum value of the metrics of the links after deletion of the falsely detected link(s). The non-detection determination unit  105  outputs, as an undetected link, the link of a combination of nodes having a metric less than or equal to the threshold that has been set to the threshold setting unit  104 , among the combination(s) of nodes between which no link has been detected. The link correction unit  106  outputs, to the outside world, a link presence-absence table generated by deleting the falsely detected link(s) from, and adding the undetected link(s) to, the link presence-absence table output by the link determination unit  102 . The link correction unit  106  also outputs, to the outside world, link estimation information generated by deleting the falsely detected link(s) and adding the undetected link(s). 
       FIG. 4  is a chart illustrating an example of the location information table according to the first embodiment. The location information table is output by the location information output device  300 . The location information output device  300  includes, for example, the node location information manually entered by the administrator of the network. Alternatively, the location information output device  300  automatically obtains the node location information. Examples of the method of automatically obtaining the node location information by the location information output device  300  include a method in which the location information output device  300  compares the phase difference of a radio wave observed by multiple antennas included in the location information output device  300 , and estimates the incoming direction of that radio wave, thus to obtain the node location information. The location information table includes the name of a node, the X coordinate of the node, the Y coordinate of the node, and the Z coordinate of the node. An X coordinate, a Y coordinate, and a Z coordinate are, for example, coordinates of a coordinate system having the X-, Y-, and Z-directions arbitrarily determined with respect to a certain point serving as the reference point; or values of three-dimensional coordinates with respect to the origin that is the coordinate point where the location information output device  300  is located. This configuration allows the location information table to contain three-dimensional location information of each node. The location information table includes M rows of data when M nodes exist. 
       FIG. 5  is a chart illustrating an example of the link estimation table according to the first embodiment. The link estimation table provides information indicating the combinations of nodes presumed that have a link therebetween. The link estimation table is output by the network configuration estimation device  200 . The network configuration estimation device  200  analyzes emission patterns of radio waves emitted by respective nodes to estimate the network configuration, and then outputs an estimation result as the link estimation table. An example of estimating a network configuration by analysis of emission patterns of radio waves emitted by respective nodes is, as the method described in Patent Literature 1, to separate the information on the radio wave emitted by a node into control information for communication connection of nodes, and user information to be sent after establishment of communication connection, and to use a characteristic of the control information and a characteristic of the user information, thus to estimate the network configuration. The link estimation table includes information on a node A and on a node B. The node A and the node B are, respectively, one node and the other node of a combination of two nodes. The link estimation table stores information on the node A and on the node B corresponding to a combination of nodes presumed, by the network configuration estimation device  200 , that has a link therebetween. The combinations of nodes stored in the link estimation table as the node A and as the node B include combinations of nodes corresponding to the falsely detected link(s) and to the undetected link(s). The link estimation table includes data of as many nodes A and nodes B as the number of combinations of nodes presumed that have a link therebetween. 
       FIG. 6  is a chart illustrating an example of the link presence-absence table according to the first embodiment. The link presence-absence table is output by the link determination unit  102 . The link presence-absence table includes information on the node A, the node B, the metric, and whether a link exists. The node A and the node B are, respectively, one node and the other node of a combination of two nodes. The metric column contains the value of the distance between the node A and the node B. The column of the information on whether a link exists contains information of “present” for a combination of nodes listed in the link estimation table, and contains information of “absent” for a combination of nodes not listed in the link estimation table. The link presence-absence table includes M×(M−1)/2 rows of data when M nodes exist. 
       FIG. 7  is a diagram illustrating an example of the processing of the false detection determination unit  103 , the threshold setting unit  104 , and the non-detection determination unit  105  according to the first embodiment.  FIG. 7( a )  is a graph having a vertical axis representing the propagation loss between a pair of link-detected nodes, and a horizontal axis representing the metric thereof. It is seen that the false detection determination unit  103  determines the links of the respective combinations of nodes having a metric ranging from  90  to  100  to be falsely detected links, among the links listed as detected in the link presence-absence table. In addition, the threshold setting unit  104  stores a value of 80 as the threshold, which value is the maximum value of the metrics of the links after deletion of the falsely detected links. 
       FIG. 7( b )  is a graph having a vertical axis representing the propagation loss between a pair of link-undetected nodes, and a horizontal axis representing the metric thereof. It is seen that the non-detection determination unit  105  determines the links of the respective combinations of nodes having a metric less than or equal to 80, set by the threshold setting unit  104  as the threshold, to be undetected links, among the links of the respective combinations of nodes listed as undetected. 
     A hardware configuration of the metric calculation unit  101 , the link determination unit  102 , the false detection determination unit  103 , the threshold setting unit  104 , the non-detection determination unit  105 , and the link correction unit  106  according to the first embodiment will now be described. The metric calculation unit  101 , the link determination unit  102 , the false detection determination unit  103 , the threshold setting unit  104 , the non-detection determination unit  105 , and the link correction unit  106  are implemented in a processing circuit that is an electronic circuit that performs the processing thereof. 
     This processing circuit may be a dedicated hardware element, or a control circuit including a memory and a central processing unit (CPU) that executes a program stored in the memory. In this regard, the memory is, for example, a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), or a flash memory; a magnetic disk, an optical disk, or the like. In a case in which this processing circuit is a control circuit including a CPU, this control circuit is, for example, a control circuit  900  configured as illustrated in  FIG. 8 . 
     As illustrated in  FIG. 8 , the control circuit  900  includes a processor  900   a  being a CPU, and a memory  900   b . In a case in which the processing circuit is implemented by the control circuit  900  illustrated in  FIG. 8 , the functionality is implemented by the processor  900   a  by reading and executing a program or programs corresponding to the processes, stored in the memory  900   b . The memory  900   b  is also used as a temporary memory in the processing performed by the processor  900   a.    
     An operation of the network management device  100  according to the first embodiment will now be described.  FIG. 9  is a flowchart illustrating an example of control of the network management device according to the first embodiment. Note that the flowchart illustrated in  FIG. 9  may be modified to change the processing order, or to perform some processing in parallel, as necessary and appropriate. 
     The metric calculation unit  101  calculates a metric for each of all the combinations of nodes that are connectable to each other, based on the location information of all the nodes received from the location information output device  300  (step S 01 ). 
     The link determination unit  102  generates a link presence-absence table from the link estimation table obtained from the network configuration estimation device  200 , and from the metric information obtained from the metric calculation unit  101  (step S 02 ). 
     The false detection determination unit  103  determines the falsely detected link(s) based on the distribution of the metric for the combination(s) of nodes indicated as “link present” in the link presence-absence column of the link presence-absence table (step S 03 ). 
     The threshold setting unit  104  sets, as the threshold, the maximum value of the metrics of the links after deletion of the falsely detected link(s) from the information on the detected links (step S 04 ). 
     The non-detection determination unit  105  determines the link(s) having a metric less than or equal to the threshold to be undetected link(s) (step S 05 ). 
     The link correction unit  106  rewrites the link presence-absence table output by the link determination unit  102  to change the link presence-absence information of a link that has been determined to be a falsely detected link by the false detection determination unit  103 , to information indicating “link absent”, and to change the link presence-absence information of a link that has been determined to be an undetected link by the non-detection determination unit  105 , to information indicating “link present”. The link correction unit  106  then outputs the resultant link presence-absence table (step S 06 ). In addition, the link correction unit  106  deletes the falsely detected link(s) from, and adds the undetected link(s) to, the link estimation table, and outputs the updated link estimation table. 
     As described above, in the present embodiment, the metric calculation unit  101  calculates a metric using the location information obtained from the location information output device  300 . The link determination unit  102  generates the link presence-absence table from the metrics and from the link estimation table obtained from the network configuration estimation device  200 . The false detection determination unit  103  makes a determination of a falsely detected link. The threshold setting unit  104  sets the maximum metric value as the threshold among the links after deletion of the falsely detected link(s). The non-detection determination unit  105  determines each of the link(s) of the combination(s) of nodes having a metric less than or equal to the threshold set by the threshold setting unit  104  the undetected link. The link correction unit  106  deletes the falsely detected link(s) and adds the undetected link(s). Thus, the network management device  100  can reduce decrease in accuracy of estimation of the network configuration. 
     Second Embodiment 
       FIG. 10  is a diagram illustrating functional blocks of a network management device according to a second embodiment. Note that the elements having the same functionality as the corresponding elements of the first embodiment are designated by the same reference characters as the first embodiment, and duplicate description thereof will be omitted. A network management device  100   a  includes a location information output unit  107  and a network configuration output unit  108  in addition to the functional units similar to the corresponding functional units of the first embodiment. The location information output unit  107  has functionality similar to the functionality of the location information output device  300  of the first embodiment. The network configuration output unit  108  has functionality similar to the functionality of the network configuration estimation device  200  of the first embodiment. 
     The location information output unit  107  and the network configuration output unit  108  according to the second embodiment are implemented in a processing circuit similar to the processing circuit of the first embodiment. 
     In the present embodiment, the inclusion of the location information output unit  107  and the network configuration output unit  108  in the network management device  100   a  allows the location information of each node and the link information to be input from the inside of the network management device  100   a . By using the node location information and the network configuration estimation information, the network management device  100   a  can provide an advantage similar to the advantage of the first embodiment. 
     Third Embodiment 
       FIG. 11  is a diagram illustrating an example of the configuration of a network management system according to a third embodiment. Note that the elements having the same functionality as the corresponding elements of the first embodiment are designated by the same reference characters as the first embodiment, and duplicate description thereof will be omitted. A network management system  500   a  includes a network management device  100   b , the network configuration estimation device  200 , and the location information output device  300 . The network management device  100   b  is connected to the network configuration estimation device  200  and to the location information output device  300 . The network management device  100   b  outputs a significance value of each node taking into consideration the falsely detected link(s) and the undetected link(s). 
       FIG. 12  is a diagram illustrating an overview of the processing of the network management device  100   b  according to the third embodiment. The network configuration estimation device  200  estimates the network configuration through an operation similar to the operation of the first embodiment. The network management device  100   b  estimates the network configuration as illustrated in  FIG. 12( b )  from the state of the network of  FIG. 12( a ) , and outputs a significance value of each node taking into consideration the presence of falsely detected link(s) and undetected link(s) as illustrated in  FIG. 12( c ) . 
       FIG. 13  is a diagram illustrating functional blocks of the network management device  100   b  according to the third embodiment. The network management device  100   b  includes the metric calculation unit  101 , the link determination unit  102 , the false detection determination unit  103 , the threshold setting unit  104 , the non-detection determination unit  105 , a graph generation unit  109 , a significant node search unit  110 , and a significance calculation unit  111 . The graph generation unit  109  generates a network graph from the link presence-absence information obtained from the link determination unit  102 . Note that the graph generation unit  109  may generate a network graph from information after deletion of the falsely detected link(s) from the link estimation information. The significant node search unit  110  searches for a significant node from the network graph generated. The significance calculation unit  111  calculates a significance value for each node from the information of the significant node that has been found. A significant node is a node that will significantly affect the network upon failure of that node in the network. 
     The graph generation unit  109 , the significant node search unit  110 , and the significance calculation unit  111  according to the third embodiment are implemented in a processing circuit similar to the processing circuit of the first embodiment. 
       FIG. 14  is a diagram illustrating an example of calculation of a significance value, of the network management device  100   b  according to the third embodiment. The graph generation unit  109  deletes the falsely detected link(s) determined by the false detection determination unit  103 , from the link presence-absence table output from the link determination unit  102 , and thus generates a graph of the network.  FIG. 14( a )  illustrates the network graph using a solid line for a normally detected link, and a dotted line for a falsely detected link.  FIG. 14( b )  illustrates the network graph using a solid line for a normally detected link, and a dashed-and-dotted line for an undetected link of the network graph. The graph in this example may be output in a format such as an adjacency matrix or an edge list depending on the representation method. 
       FIGS. 14( c ) to 14( f )  illustrate an operation in which the significant node search unit  110  searches for a significant node, and the significance calculation unit  111  adds significance values. The significant node search unit  110  adds one undetected link having the minimum metric to the network graph generated by the graph generation unit  109 , and then searches for a significant node. Examples of significant node include a node that would cause a graph to become a disconnected graph upon removal of the node that is found, from the graph, and a node whose centrality, such as betweenness centrality, is the highest. A betweenness centrality is a ratio of the number of links formed by the node that is found, to the number of links after removal of the link(s) formed by the node that is found, from all the links in the network graph. Note that there may be more than one significant node. 
     The significance calculation unit  111  prepares in advance the significance values of the nodes in tabular form, and adds the significance value for the significant node found by the significant node search unit  110 . Examples of the method to add a significance value include a method of addition using a score, which is 1 for the significant node, and 0 for the other nodes, and a method to add values respectively calculated for all the nodes in the network graph, such as in a case of betweenness centrality. Alternatively, another applicable method is to weight the significance value on every addition operation. In the case of addition of a significance value using a score that is 1 for the significant node, and 0 for the other nodes, examples of weighting a significance value include a method to add a value that is incremented by 1 each time the score of the significant node is added for the significant node. The significant node search unit  110  and the significance calculation unit  111  continue the search for a significant node and the calculation of the significance value until all the undetected link(s) is/are added to the network graph. In addition, the significance calculation unit  111  outputs the information of the significance of each node. The significance value output by the significance calculation unit  111  may be the value in the table of significance without change, or may be a value converted from the value in the table of significance. The information of the significance output by the significance calculation unit  111  is also referred to as significance information. The significant node search unit  110  may also count the number of times of determining a node to be a significant node on a per-node basis. In addition, the significance calculation unit  111  may include the number of times of determining a node to be a significant node, in the significance information. 
     An operation of the network management device  100   b  will now be described.  FIG. 15  is a flowchart illustrating an example of control of the network management device  100   b  according to the third embodiment. Note that the flowchart illustrated in  FIG. 15  may be modified to change the processing order, or to perform some processing in parallel, as necessary and appropriate. The process from steps S 01  to S 05  of this flowchart is the same as the corresponding process of the flowchart of  FIG. 9 . 
     The graph generation unit  109  generates, from the link presence-absence table output by the link determination unit  102 , a graph of the network using the link(s) determined by the false detection determination unit  103  to be falsely detected (step S 07 ). 
     The significant node search unit  110  adds one undetected link having the minimum metric to the graph generated (step S 08 ), and searches for a significant node (step S 09 ). 
     The significance calculation unit  111  prepares in advance the significance value for each node in tabular form, and adds the significance value for the significant node found (step S 10 ). 
     When all the undetected links are added (step S 11 , Yes), the significance calculation unit  111  calculates the significance value for each node from the table of significance, and outputs the significance values (step S 12 ). When all the undetected links have not yet been added (step S 11 , No), the process returns to step S 08 . 
     As described above, the network management device  100   b  deletes the falsely detected link(s) obtained from the false detection determination unit  103  from, and adds the undetected link(s) obtained from the non-detection determination unit  105  to, the network graph generated by the graph generation unit  109 . In addition, the network management device  100   b  searches for a significant node by the significant node search unit  110 , and calculates the significance value for each node by the significance calculation unit  111 . This operation enables a user to identify a significant node in the network configuration, and to maintain or manage the network configuration even when the network configuration estimated by the network configuration estimation device  200  is defective. 
     Fourth Embodiment 
       FIG. 16  is a diagram illustrating functional blocks of a network management device according to a fourth embodiment. Note that the elements having the same functionality as the corresponding elements of the third embodiment are designated by the same reference characters as the third embodiment, and duplicate description thereof will be omitted. A network management device  100   c  includes the location information output unit  107  and the network configuration output unit  108  in addition to the functional units similar to the corresponding functional units of the third embodiment. 
     In the present embodiment, the network management device  100   c  includes the location information output unit  107  and the network configuration output unit  108 , and this configuration allows the location information of each node and the link information to be input from the inside of the network management device  100   c . By using the node location information and the network configuration estimation information, the network management device  100   c  can provide an advantage similar to the advantage of the third embodiment. 
     The configurations described in the foregoing embodiments are merely examples of various aspects of the present invention. These configurations may be combined with a known other technology, and moreover, a part of such configurations may be omitted and/or modified without departing from the spirit of the present invention. 
     A network management device according to the present invention provides an advantage in being capable of reducing decrease in accuracy of estimation of the network configuration.