Patent Publication Number: US-2023134812-A1

Title: Network management apparatus, method, and program

Description:
TECHNICAL FIELD 
     The present embodiment relates to a network management apparatus, a method, and a program. 
     BACKGROUND ART 
     There are techniques for simulatively generating a failure in a building, a communication cable, a communication apparatus, or a communication medium on a physical layer which realizes a service by a communication network and, when simulating an effect of the failure on the service, specifying the effect on the service using a same method regardless of a type of the service or a type of the NW (for example, refer to NPL 1). 
     The technique disclosed in NPL 1 described above does not provide means of specifying a candidate of a location on the physical layer having caused a failure that occurred on a transmission layer or a service layer on top of a logical layer. 
     In addition, there are techniques for specifying a physical layer object that is multiply used by a logical layer in an apparatus, a core wire, a building, or a cable on a physical layer to be a cause of a failure on the logical layer in order to specify a candidate of a location on the physical layer having caused the failure (for example, refer to NPL 2). 
     CITATION LIST 
     Non Patent Literature 
     
         
         [NPL 1] “A Study on Method of Visualization for Multiple Network Structure” (ICM Meeting, March 2019) 
         [NPL 2] “Study on Method of Identifying Affected Equipment to Support Recovery Operation in a Large-scale Disaster” (ICM Meeting, January 2020) 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     When a failure location is specified using the technique disclosed in NPL 2 described above by specifying a physical layer object that is multiply used by a logical layer in an apparatus, a core wire, a building, or a cable on a physical layer to be a cause of a failure on the logical layer, a physical resource such as a housing building or a high-order apparatus in which a plurality of failure passes are housed in a communication network is likely to be specified as a candidate of a suspicious facility as the failure location. In other words, there is a possibility that a plurality of physical resources of which a degree of multiplicity is the same may end up being specified as a failure location. 
     The present invention has been made in consideration of the circumstances described above and an object thereof is to provide a network management apparatus, a method, and a program capable of specifying, in detail, a candidate of a facility to be a cause of a failure having occurred on a logical layer of a communication network. 
     Means for Solving the Problem 
     A network management apparatus according to an aspect of the present invention includes: a storage apparatus which stores information indicating a correspondence relationship among an information object related to a logical layer of a network configuration, an information object related to a physical layer, and an information object related to a facility layer that is an object in which the information object related to the physical layer is housed; an acquiring unit which acquires, from the storage apparatus, an information object related to a plurality of occurrence paths of a failure in the logical layer of the network configuration; and a retrieving unit which retrieves, as a candidate of a facility to be a failure cause, information objects related to the facility layer and the physical layer commonly associated with the information object related to the plurality of occurrence paths of the failure having been acquired by the acquiring unit among information objects related to the facility layer stored in the storage apparatus, which calculates, for each of the retrieved information objects related to the candidate of a facility to be the failure cause, the number of information objects which are associated with the object and which are related to the plurality of occurrence paths of the failure as a multiplicity, and which calculates, for each of the retrieved information objects related to the candidate of a facility to be the failure cause, a proportion of the multiplicity with respect to the number of information objects in the logical layer which are affected when the failure occurs in the object. 
     A network management method according to an aspect of the present invention is a network management method carried out by a network management apparatus including: a storage apparatus which stores information indicating a correspondence relationship among an information object related to a logical layer of a network configuration, an information object related to a physical layer, and an information object related to a facility layer that is an object in which the information object related to the physical layer is housed, the network management method including; acquiring, from the storage apparatus, an information object related to a plurality of occurrence paths of a failure in the logical layer of the network configuration; and retrieving, as a candidate of a facility to be a failure cause, information objects related to the facility layer and the physical layer commonly associated with the acquired information object related to the plurality of occurrence paths of the failure among information objects related to the facility layer stored in the storage apparatus. 
     Effects of the Invention 
     According to the present invention, a candidate of a facility to be a cause of a failure having occurred on a logical layer of a communication network can be specified in detail. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram showing, in a table format, an example of objectification of a facility layer in a network configuration to be applied to a network management apparatus according to an embodiment of the present invention. 
         FIG.  2    is a diagram showing, in a table format, an example of objectification of a physical layer in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  3    is a diagram showing, in a table format, an example of objectification of a Logical Device layer in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  4    is a diagram showing, in a table format, an example of objectification of a communication layer in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  5    is a diagram showing an application example of a facility Entity and a physical Entity to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  6    is a diagram showing an application example of a physical Entity and a logical Entity to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  7    is a diagram showing an example of objectification of a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  8    is a diagram showing an example of designation of a failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  9    is a diagram showing an example of retrieval of a physical resource used by a failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  10    is a diagram showing, in a table format, an example of a retrieval result of a physical resource used by a failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  11    is a diagram showing, in a table format, an example of a retrieval result of a facility resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  12    is a diagram showing an example of specification of a pass that is affected when a failure occurs in a physical resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  13    is a diagram showing, in a table format, an example of a failure rate of a physical resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  14    is a diagram showing, in a table format, an example of a candidate of a failure location based on a failure rate of a physical resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
         FIG.  15    is a diagram showing an example of a software configuration of the network management apparatus according to the embodiment of the present invention. 
         FIG.  16    is a sequence chart showing an example of procedures for registering facility information by the network management apparatus according to the embodiment of the present invention. 
         FIG.  17    is a diagram showing, in a table format, an example of Spec (facility layer and physical layer) of facility information retained by the network management apparatus according to the embodiment of the present invention. 
         FIG.  18    is a diagram showing, in a table format, an example of Spec (logical layer) of facility information retained by the network management apparatus according to the embodiment of the present invention. 
         FIG.  19    is a diagram showing an example of use of a Spec class and an Entity class by the network management apparatus according to the embodiment of the present invention. 
         FIG.  20    is a diagram showing, in a table format, an example of a schema of a Specificication table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
         FIG.  21    is a diagram showing, in a table format, an example of a schema of a SpecCharacteristic table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
         FIG.  22    is a diagram showing, in a table format, an example of a schema of an Entity table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
         FIG.  23    is a diagram showing, in a table format, an example of a schema of a CharacteristicValue table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
         FIG.  24    is a diagram showing an example of a configuration that functions with an input of a failure location in the network management apparatus according to the embodiment of the present invention. 
         FIG.  25    is a diagram showing an example of a configuration that functions with a retrieval of a physical resource in the network management apparatus according to the embodiment of the present invention. 
         FIG.  26    is a flow chart showing an example of processing procedures from an input of a failure pass to a retrieval of physical and facility resources by the network management apparatus according to the embodiment of the present invention. 
         FIG.  27    is a diagram showing, in a table format, an example of types of an array of failure location Entities to be applied by the network management apparatus according to the embodiment of the present invention. 
         FIG.  28    is a flow chart showing an example of processing procedures of a retrieval of a PP Entity by the network management apparatus according to the embodiment of the present invention. 
         FIG.  29    is a flow chart showing an example of processing procedures of a retrieval of PD and PL Entities by the network management apparatus according to the embodiment of the present invention. 
         FIG.  30    is a flow chart showing an example of processing procedures of a retrieval of a PS Entity by the network management apparatus according to the embodiment of the present invention. 
         FIG.  31    is a flow chart showing an example of processing procedures of a retrieval of an AS Entity by the network management apparatus according to the embodiment of the present invention. 
         FIG.  32    is a flow chart showing an example of processing procedures of a retrieval of a physical resource to be commonly used by the network management apparatus according to the embodiment of the present invention. 
         FIG.  33    is a diagram showing, in a table format, an example of types of a multiple/failure rate Entity to be applied by the network management apparatus according to the embodiment of the present invention. 
         FIG.  34    is a diagram showing, in a table format, an example of an array of failure location Entities to be applied by the network management apparatus according to the embodiment of the present invention. 
         FIG.  35    is a block diagram showing an example of a hardware configuration of the network management apparatus according to the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
     In a network management apparatus according to an embodiment of the present invention, each constituent element of a facility layer, a physical layer, and a logical layer of a communication network is objectified using a unified information object (hereinafter, simply referred to as an object). 
     In addition, the network management apparatus uses a connection between respective objects to specify, in the facility layer and the physical layer, a candidate of a facility that is a cause of a failure having occurred in the logical layer. An object of the facility layer houses an object of the physical layer. 
     Accordingly, a candidate of a facility to be a cause of a failure having occurred in a network constituted by a plurality of layers with different protocols and media types can be specified. 
     Next, an outline of the network management apparatus according to the embodiment of the present invention will be described in (1) to (13) below. 
     (1) The network management apparatus objectifies, according to an object (Spec, Entity (information object)) based on conventional art, a target NW in a descending order from an upper layer in a logical layer, a physical layer, and a facility layer. 
     The facility layer is, for example, a building or a cable. In the present embodiment, a building and a communication cable in the facility layer are respectively retained as a building object and a cable object. The building is not particularly limited as long as the building is a building or a facility which houses a communication apparatus. In addition, the cable is not particularly limited as long as the cable is a facility which houses a communication medium. 
     The physical layer is, for example, a network apparatus, a communication port, or a communication medium. In the present embodiment, a network apparatus, a communication port, and a communication medium in the physical layer are respectively retained as an apparatus object, a port object, and a medium object. 
     The logical layer corresponds to, for example, a point object and a line or plane object. In the present embodiment, a generation location or a termination of communication in the logical layer is retained as a point object, and communication between such point objects and a communication-enabled range between the point objects are respectively retained as a line or plane object. 
     The physical layer and the facility layer described above may be referred to as a physical layer and a facility layer in a narrow sense which are included in a physical layer in a broad sense. 
     (2) An operator designates a plurality of line objects that corresponding to a communication pass on which a failure has occurred (sometimes referred to as a failure pass) and sets a failed state. 
     (3) The network management apparatus acquires point objects constituting the line object designated in (2). 
     (4) The network management apparatus iteratively retrieves point objects of a lower layer included in the point object acquired in (3) and interrupts processing when there are no point objects. 
     (5) The network management apparatus acquires a port object included in point objects obtained by the time of interruption of processing in (4). 
     (6) The network management apparatus retrieves an apparatus object and a medium object belonging to the port object acquired in (5). 
     (7) The network management apparatus acquires a building object including the apparatus object (a building object housing the apparatus object) acquired in (6). 
     (8) The network management apparatus acquires a cable object including the medium object (a cable object housing the medium object) acquired in (6). 
     (9) The network management apparatus performs the procedures of (3) to (8) with respect to the plurality of line objects designated in (2) and acquires a building object, a cable object, an apparatus object, and a medium object used by the line objects. 
     (10) Among building objects, cable objects, apparatus objects, and medium objects commonly used by line objects, there are those multiply used by other line objects. The network management apparatus retains and outputs the number of multiple uses (multiplicity) and relevant objects of the facility and physical layers. 
     (11) The network management apparatus calculates, with respect to the building object, the cable object, the apparatus object, and the medium object acquired in (9), a proportion (failure rate) of the number of line objects (multiplicity) in which a failure has occurred with respect to the number of communication passes that are affected when a failure occurs in the physical resource. 
     (12) The network management apparatus outputs a multiplicity and a failure rate for each object of the facility and physical layers retained in (10). 
     (13) The network management apparatus highlights and displays the objects acquired in (9) in accordance with the multiplicity and the failure rate of each object. 
     Next, objectification of a network configuration will be described. A method of objectification of a facility layer will now be described. The objectification is also described in, for example, Japanese Patent Application No. 2018-196853 and PCT/JP2019/040978. 
       FIG.  1    is a diagram showing, in a table format, an example of objectification of a facility layer in a network configuration to be applied to a network management apparatus according to an embodiment of the present invention. 
     As shown in  FIG.  1   , due to application of a PS (Physical Structure) Entity and an AS (Aggregate Section) Entity, the configuration of the facility layer is retained in a unified format. 
     As shown in  FIG.  1   , Entity names in the facility layer are classified into PS and AS. 
     As shown in  FIG.  1   , PS signifies a facility such as a housing building, or a manhole. Various “attributes: description” related to a PS are as follows. 
     (First) status: an attribute indicating a state of the PS Entity (normal: true, failure: false) 
     (Second) pdList: an array of PD Entities included in the PS Entity 
     (Third) asList: an array of AS Entities included in the PS Entity 
     (Fourth) Position: two-dimensional coordinates indicating a position of the PS Entity 
     As shown in  FIG.  1   , an AS (Aggregate Section) signifies a cable, a communication line, a cable tunnel/service tunnel, or the like. Various “attributes: description” related to an AS are as follows. 
     (First) status: an attribute indicating a state of the AS Entity (normal: true, failure: false) 
     (Second) plList: an array of PL Entities included in the AS Entity 
     (Third) position: two-dimensional coordinates indicating a position of the AS Entity 
     A PS of the facility layer corresponds to the building object described above, and an AS of the facility layer corresponds to the cable object described above. 
     Next, objectification of a physical layer will be described. 
       FIG.  2    is a diagram showing, in a table format, an example of objectification of a physical layer in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     As shown in  FIG.  2   , due to application of a PD (Physical Device) Entity, a PP (Physical Port) Entity, a PL (Physical Link) Entity, and a PC (Physical Connector) Entity, the configuration of the physical layer is retained in a unified format. 
     As shown in  FIG.  2   , Entity names in the physical layer are classified into PD, PP, PL, and PC. 
     As shown in  FIG.  2   , a PD signifies an apparatus. Various “attributes: description” related to a PD are as follows. 
     (First) status: an attribute indicating a state of the PD (normal operation: true, abnormal operation: false) 
     (Second) ppList: an array of PPs included in the PD 
     (Third) position: two-dimensional coordinates indicating a position of the PD 
     PP signifies a communication port included in the apparatus. Various “attributes: description” related to a PP are as follows. 
     (First) status: an attribute indicating a state of the PP (normal operation: true, abnormal operation: false) 
     (Second) position: two-dimensional coordinates indicating a position of the PD 
     PL signifies a core wire of the cable. Various “attributes: description” related to a PL are as follows. 
     (First) status: an attribute indicating a state of the PL (normal operation: true, abnormal operation: false) 
     (Second) pcList: an array of PCs included in the PL 
     PC signals a connector for connecting the cable. Various “attributes: description” related to a PC are as follows. 
     (First) status: an attribute indicating a state of the PC (normal operation: true, abnormal operation: false) 
     (Second) ppList: an array of PPs included in the PC 
     A PD on the physical layer corresponds to the apparatus object described above, a PP on the physical layer corresponds to the port object described above, and a PL and a PC on the physical layer correspond to the medium object described above. 
     Next, objectification of a logical layer will be described. 
       FIGS.  3  and  4    are diagrams showing, in a table format, an example of objectification of a logical layer in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     As shown in  FIGS.  3  and  4   , due to application of a TPE (Termination Point Encapsulation) Entity, an NFD (Network Forwarding Domain) Entity, a TL (Topological Link) Entity, and an FRE (Forwarding Relationship Encapsulation) (LC (Link Connect), XC (Cross(X) Connect), and NC (Network Connect)) Entity, a configuration of a logical layer is retained in a unified format. 
     As shown in  FIG.  4   , an FRE Entry is classified into an LC (Link Connect) Entity, an XC (Cross(X) Connect) Entity, and an NC (Network Connect) Entity. 
     A TL signifies connectivity (in a Logical Device layer) between apparatuses. Various “attributes: description” related to a TL are as follows. 
     (First) endPointList: an array of TPE Entities constituting the TL Entity 
     (Second) status: an attribute indicating a state of the TL Entity (normal operation: true, abnormal operation: false) 
     An NFD signifies a transferable range (in a Logical Device layer) in an apparatus. Various “attributes: description” related to an NFD are as follows. 
     (First) endPointList: an array of TPE Entities constituting the NFD Entity 
     (Second) Status: an attribute indicating a state of the NFD Entity (normal operation: true, abnormal operation: false) 
     A TPE signifies a termination of communication. Various “attributes: description” related to a TPE are as follows. 
     (First) tpeRefList: an array of TPE Entities including a TPE Entity of a corresponding lower layer (1 array in the embodiment) 
     (Second) ppRefList: an array of PP Entities corresponding to the TPE Entity (1 array in the embodiment) 
     (Third) status: an attribute indicating a state of the TPE Entity (normal operation: true, abnormal operation: false) 
     (Fourth) layerName: a name of the layer 
     A TL in the logical layer corresponds to the line object described above. An NFD in the logical layer corresponds to the line object or the plane object described above. A TPE in the logical layer corresponds to the point object described above. 
     An LC in an FRE signifies connectivity (in a communication layer) between apparatuses. Various “attributes: description” related to an LC are as follows. 
     (First) endPointList: an array of TPE Entities constituting the LC Entity 
     (Second) status: an attribute indicating a state of the LC Entity (normal operation: true, abnormal operation: false) 
     (Third) layerName: a name of the layer 
     An XC signifies connectivity (in a communication layer) inside an apparatus. Various “attributes: description” related to an XC are as follows. 
     (First) endPointList: an array of TPE Entities constituting the XC Entity 
     (Second) status: an attribute indicating a state of the XC Entity (normal operation: true, abnormal operation: false) 
     (Third) layerName: a name of the layer 
     An NC signifies End-End connectivity (in a communication layer) which is formed by an LC and an XC. Various “attributes: description” related to an XC are as follows. 
     (First) endPointList: an array of TPE Entities constituting the LC or the XC 
     (Second) status: an attribute indicating a state of the NC Entity (normal operation: true, abnormal operation: false) 
     (Third) userList: an array of character strings retaining a subscriber name or an URL (Uniform Resource Locator) of an IF (interface) for acquiring a subscriber name 
     (Fourth) layerName: a name of the layer 
     An LC and an XC in the logical layer corresponds to the line object or the plane object described above. In addition, an NC in the logical layer corresponds to a communication object having an array of point objects storing all point objects between a start point and an end point on the logical layer. 
     Next, an application example of a facility Entity and a physical Entity will be described.  FIG.  5    is a diagram showing an application example of a facility Entity and a physical Entity to be applied to the network management apparatus according to the embodiment of the present invention. 
     As shown in  FIG.  5   , a Physical Resource is classified into a physical layer and a facility layer. 
     In the example shown in  FIG.  5   , the physical layer of the Physical Resource has a PD (NW apparatus), a PD (CTF (Cable termination Frame: a termination apparatus of an optical fiber)), a PL (core wire), a PC (connector), and a PP (port). The PD (NW apparatus) and the PD (CTF) include the PP (port) and the PC (connector) is attached to both ends of the PL (core wire). 
     The PD (NW apparatus) and the PD (CTF) can communicate with each other when the PP (port) on the PD (NW apparatus) side is connected to the PC (connector) at one end of the PL (core wire) and the PP (port) on the PD (CTF) side is connected to the PC (connector) at the other end of the PL (core wire). The same applies to a connection between PDs (CTFs). 
     In the example shown in  FIG.  5   , the facility layer of the Physical Resource has a PS (station building), a PD (NW apparatus), a PD (CTF), and an Aggregate Section (cable). 
     The Aggregate Section is an object having the PL (core wire) in plurality. 
     In the example shown in  FIG.  5   , the PS (station building) is provided with the PD (NW apparatus) and the PD (CTF). Accordingly, PSs (station buildings) can communicate with each other. For example, the PD (CTF) inside a first PS (station building) and the PD (CTF) inside a second PS (station building) become capable of PS (station building) communication via the Aggregate Section (cable). 
     Next, an application example of a physical Entity and a logical Entity will be described.  FIG.  6    is a diagram showing an application example of a physical Entity and a logical Entity to be applied to the network management apparatus according to the embodiment of the present invention. 
     In the example shown in  FIG.  6   , a Physical Resource has a physical layer and a Logical Resource has a communication layer and a Logical Device layer. The Logical Device layer corresponds to an object in a lower layer with respect to the logical layer. The physical layer corresponds to an object in a lower layer with respect to the Logical Device layer. In the example shown in  FIG.  6   , in the physical layer, PPs in a Physical Device are respectively connected to PCs at one end and another end of a PL. 
     The corresponding logical layer has a TPE, an XC, and an LC, and the Logical Device layer has a TPE, an NFD, and a TL. In  FIG.  6   , an object is depicted by an arrow in a lower layer with respect to a point object in a given layer. 
     In the example shown in  FIG.  6   , the Physical Device in the physical layer respectively corresponds to the XC in the logical layer and the NFD in the Logical Device layer. 
     In the example shown in  FIG.  6   , the PP in the Physical Device layer respectively corresponds to the TPE in the logical layer and the TPE in the Logical Device layer. The same applies to the PC attached to the PL. 
     In the example shown in  FIG.  6   , the PL in the physical layer respectively corresponds to the LC in the logical layer and the TL in the Logical Device layer. In addition, in the example shown in  FIG.  6   , one NC is formed by the XC and the LC in the logical layer. 
     Next, an example of objectification of a network configuration will be described.  FIG.  7    is a diagram showing an example of objectification of a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
       FIG.  7    shows, with an apparatus provided in a building A as an upper device, facility, physical, and logical layers of a network configuration between the apparatus provided in the building A and apparatuses provided in buildings B to E. The Logical Device layer will not be described. 
     In the example shown in  FIG.  7   , the logical layer on which the apparatuses are realized is provided with TPEs and FREs (LC, XC, and NC) including TPE_apparatuses_ 1 _ 1 ,  1 _ 2 ,  2 _ 1 ,  2 _ 2 ,  3 _ 1 ,  4 _ 1 ,  5 _ 1 , and  6 _ 1  and FRE (LC)_apparatuses_ 1  to  4 . One end of the FRE (LC)_apparatus_ 1  is provided with the TPE_apparatus_ 1 _ 1  and another end is provided with the TPE_apparatus_ 3 _ 1 . One end of the (LC)_apparatus_ 2  is provided with the TPE_apparatus_ 1 _ 2  and another end is provided with the TPE_apparatus_ 4 _ 1 . One end of the FRE (LC)_apparatus_ 3  is provided with the TPE_apparatus_ 2 _ 1  and another end is provided with the TPE_apparatus_ 5 _ 1 . One end of the FRE (LC)_apparatus_ 4  is provided with the TPE_apparatus_ 2 _ 2  and another end is provided with the TPE_apparatus_ 6 _ 1 . 
     The physical layer on which the apparatuses are realized is provided with PPs, PDs, and PLs including PP_apparatuses_ 1 _ 1 ,  1 _ 2 ,  2 _ 1 ,  2 _ 2 ,  3 _ 1 ,  4 _ 1 ,  5 _ 1 , and  6 _ 1 , PD_apparatuses_ 1  to  6 , and PL_apparatuses_ 1  to  4 . One end of the PL_apparatus_ 1  is provided with the PD_apparatus_ 1  and another end is provided with the PD_apparatus_ 3 . One end of the PL_apparatus_ 2  is provided with the PD_apparatus_ 1  and another end is provided with the PD_apparatus_ 4 . One end of the PL_apparatus_ 3  is provided with the PD_apparatus_ 2  and another end is provided with the PD_apparatus_ 5 . One end of the PL_apparatus_ 4  is provided with the PD_apparatus_ 2  and another end is provided with the PD_apparatus_ 6 . 
     The facility layer on which the facilities are realized is provided with PSs and ASs including PSs_A to E and ASs__ 1  to  7 . The ASs__ 1 ,  2 ,  4 , and  6  are connected in series. The AS_ 3  is connected to a connecting portion of the ASs__ 2  and  4 , the AS_ 5  is connected to a connecting portion of the ASs__ 4  and  6 , and the AS_ 7  is connected to a connecting portion of the ASs__ 1  and  2 . 
     The PS_A and the PS_B are connected by the ASs__ 1  to  3 . The PS_A and the PS C are connected by the ASs__ 1 ,  2 ,  4 , and  5 . The PS_A and the PS_D are connected by the ASs__ 1 ,  2 ,  4 , and  6 . The PS_A and the PS_E are connected by the ASs__ 1  and  7 . 
     The TPE_apparatuses_ 1 _ 1 ,  1 _ 2 ,  2 _ 1 ,  2 _ 2 ,  3 _ 1 ,  4 _ 1 ,  5 _ 1 , and  6 _ 1  of the logical layer correspond one-to-one with the PP_apparatuses_ 1 _ 1 ,  1 _ 2 ,  2 _ 1 ,  2 _ 2 ,  3 _ 1 ,  4 _ 1 ,  5 _ 1 , and  6 _ 1  of the physical layer. 
     The FRE (LC)_apparatuses_ 1  to  4  of the logical layer correspond one-to-one with the PL_apparatuses_ 1  to  4  of the physical layer. The PL_apparatus_ 1  corresponds to the ASs__ 1  to  3  of the facility layer. The PL_apparatus_ 2  corresponds to the ASs__ 1 ,  2 ,  4 , and  5  of the facility layer. The PL_apparatus_ 3  corresponds to the ASs__ 1 ,  2 ,  4 , and  6  of the facility layer. The PL_apparatus_ 4  corresponds to the ASs__ 1  and  7  of the facility layer. 
     The PD_apparatuses_ 1  and  2  of the physical layer correspond to the PS_A of the facility layer. The PD_apparatuses_ 3  to  6  of the physical layer correspond one-to-one with the PSs B, C, D, and E of the facility layer. 
     Next, an example of designation of a failure pass related to physical resource retrieval will be described.  FIG.  8    is a diagram showing an example of designation of a failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     Here, as shown in  FIG.  8   , it is assumed that a failure has occurred in the FRE (LC)_apparatuses_ 1 ,  2 , and  3  on the apparatus (logical layer). In the present embodiment, the FRE (LC)_apparatuses_ 1 ,  2 , and  3  are designated as three failure passes, and a building, a cable, and an apparatus cable which are physical resources used by the passes are retrieved. 
       FIG.  9    is a diagram showing an example of retrieval of a physical resource used by a failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     The physical resources used by a failure pass are retrieved according to (1) to (6) below. 
     (1) A physical resource retrieving unit  15  retrieves TPEs constituting the three failure passes (FREs (LCs)). 
     (2) The physical resource retrieving unit  15  retrieves a PPort (PP) corresponding to the TPE obtained in (1). 
     (3) The physical resource retrieving unit  15  retrieves a PD to which the PPort obtained in (2) belongs. 
     (4) The physical resource retrieving unit  15  retrieves a PS to which the PD obtained in (3) belongs. 
     (5) The physical resource retrieving unit  15  retrieves a PL at which the PPort obtained in (2) terminates. 
     (6) The physical resource retrieving unit  15  retrieves an AS to which the PL obtained in (5) belongs. 
       FIG.  10    is a diagram showing, in a table format, an example of a retrieval result of a physical resource used by a failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     Results retrieved according to (1) to (6) described above with respect to the physical resources used by the failure pass FRE (LC)_apparatuses_ 1 ,  2 , and  3  shown in  FIG.  9    are as follows.
         Results retrieved with respect to the FRE (LC)_apparatus_ 1         

     Results retrieved according to (1): TPE_apparatuses_ 1 _ 1  and  3 _ 1   
     Results retrieved according to (2): PP_apparatuses_ 1 _ 1  and  3 _ 1   
     Results retrieved according to (3): PD_apparatuses_ 1  and  3   
     Results retrieved according to (4): PS_A and B 
     Results retrieved according to (5): PL_apparatus_ 1   
     Results retrieved according to (6): ASs__ 1 ,  2 , and  3 
         Results retrieved with respect to the FRE (LC)_apparatus_ 2         

     Results retrieved according to (1): TPE_apparatuses_ 1 _ 2  and  4 _ 1   
     Results retrieved according to (2): PP_apparatuses_ 1 _ 2  and  4 _ 1   
     Results retrieved according to (3): PD_apparatuses_ 1  and  4   
     Results retrieved according to (4): PS_A and C 
     Results retrieved according to (5): PL_apparatus_ 2   
     Results retrieved according to (6): ASs__ 1 ,  2 ,  4 , and  5 
         Results retrieved with respect to the FRE (LC)_apparatus_ 3         

     Results retrieved according to (1): TPE_apparatuses_ 2 _ 1  and  5 _ 1   
     Results retrieved according to (2): PP_apparatuses_ 2 _ 1  and  5 _ 1   
     Results retrieved according to (3): PD_apparatuses_ 2  and 
     Results retrieved according to (4): PS_A and D 
     Results retrieved according to (5): PL_apparatus_ 3   
     Results retrieved according to (6): ASs__ 1 ,  2 ,  4 , and  6   
     Next, retrieval of a physical resource commonly (multiply) used by a plurality of failure passes will be described. 
       FIG.  11    is a diagram showing, in a table format, an example of a retrieval result of a facility resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     In this case, PSs, ASs, and PDs multiply used by a plurality of failure passes among physical and facility resources used by failure passes are retrieved. 
     In the example shown in  FIG.  11   , the PD_apparatus_ 1  is commonly used by two failure pass FRE (LC)_apparatuses_ 1  and  2 , the AS_ 4  is commonly used by two failure pass FRE (LC)_apparatuses_ 2  and  3 , and the PS_A and the ASs__ 1  and  2  are commonly used by three failure pass FRE (LC)_apparatuses_ 1  to  3  (refer to a, b, and c in  FIG.  11   ). In this case, multiplicity (multiplicity  2  or  3 ) which corresponds to the number of failure passes being entities of use is indicated (refer to d in  FIG.  11   ). In this case, examples where multiplicity is less than 1 are omitted. 
       FIG.  12    is a diagram showing an example of specification of a pass that is affected when a failure occurs in a physical resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention.  FIG.  13    is a diagram showing, in a table format, an example of a failure rate of a physical resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     In this case, a failure rate is calculated for each physical resource (PD, PS, and AS) which is commonly used by a plurality of failure passes. The failure rate is represented by expression (1) below. As shown in  FIG.  13   , information related to a calculated failure rate is constituted by a resource type, a resource name, multiplicity, and a failure rate being associated with each other. 
       Failure rate=multiplicity/the number of passes affected when a failure occurs in a resource commonly used by a plurality of failure passes  Expression (1)
 
     For example, passes (hereinafter, sometimes referred to as affected passes) that are affected when a failure occurs in a PD commonly used by a plurality of failure passes are specified according to (1) to (3) below. 
     (1) Retrieve a PP belonging to the PD commonly used by the plurality of failure passes 
     (2) Retrieve a TPE corresponding to the PP retrieved in (1) 
     (3) Retrieve an FRE (LC) having the TPE retrieved in (2) 
     Since the affected passes in a case where a failure occurs in the PD_apparatus_ 1  which is commonly used by a plurality of failure passes as shown in  FIG.  11    are the FRE (LC)_apparatuses_ 1  and  2  as shown in  FIG.  12   , the number of affected passes is 2. In addition, multiplicity thereof is 2. Therefore, the failure rate is 1.0. 
     In addition, since the affected passes in a case where a failure occurs in the PS_A or the AS_ 1  which is commonly used by a plurality of failure passes as shown in  FIG.  11    are the FRE (LC)_apparatuses_ 1  to  4 , the number of affected passes is 4. In addition, multiplicity thereof is 3. Therefore, the failure rate is 0.75. 
     Since the affected passes in a case where a failure occurs in the AS_ 2  which is commonly used by a plurality of failure passes as shown in  FIG.  11    are the FRE (LC)_apparatuses_ 1  to  3 , the number of affected passes is 3. In addition, multiplicity thereof is 3. Therefore, the failure rate is 1.0. 
     Since the affected passes in a case where a failure occurs in the AS_ 4  which is commonly used by a plurality of failure passes as shown in  FIG.  11    are the FRE (LC)_apparatuses_ 2  and  3 , the number of affected passes is 2. In addition, multiplicity thereof is 2. Therefore, the failure rate is 1.0. 
       FIG.  14    is a diagram showing, in a table format, an example of a candidate of a failure location based on a failure rate of a physical resource sharing a common failure pass in a network configuration to be applied to the network management apparatus according to the embodiment of the present invention. 
     Five rows of information shown in  FIG.  13    which represent information on a failure rate related to each physical resource commonly used by a plurality of failure passes are subjected to descending order processing in an order of the failure rate and importance, and pieces of information that are promising as a candidate of a failure location can be sorted in upper rows to be presented to a user. 
     In the example shown in  FIG.  14   , first, among the five rows of information shown in  FIG.  13   , a total of three rows of information related to resource names “AS_ 2 ”, “PS_A”, and “AS_ 1 ” of which the failure rate is “3” are sorted higher than a total of two rows of information related to resource names “PD_apparatus_ 1 ” and “AS_ 4 ” of which the failure rate is “2”. 
     Next, among the three rows of information of which the failure rate is “3”, the source name “AS_ 2 ” having a highest failure rate of “1.0” is sorted highest. Therefore, when there are a plurality of pieces of information with a same multiplicity among the information shown in  FIG.  13   , information with a high failure rate can be sorted higher to be presented to the user as a promising candidate of a failure location. 
     Next, a configuration of the network management apparatus will be described. 
       FIG.  15    is a diagram showing an example of a functional configuration of the network management apparatus according to the embodiment of the present invention. 
     In the example shown in  FIG.  15   , a network management apparatus  10  can be configured as a computer including a central processing unit (CPU), a program memory, and an arithmetic memory. As shown in  FIG.  15   , as functions necessary for implementing the present embodiment, the network management apparatus  10  includes a facility information registering unit  11 , a Spec DB (database)  12 , an Entity DB  13 , a failure pass Entity acquiring unit  14 , a physical resource retrieving unit  15 , and an NW configuration display unit  16 . Processing performed by these elements will be described later. 
     The facility information registering unit  11 , the failure pass Entity acquiring unit  14 , the physical resource retrieving unit  15 , and the NW configuration display unit  16  can be realized by having the CPU execute a program stored in a program memory. The Spec DB  12  and the Entity DB  13  can be realized by a storage apparatus such as a non-volatile memory. The NW configuration display unit  16  can be realized by using a display apparatus such as a liquid crystal display. 
     It should be noted that, although the network management apparatus  10  can be configured by hardware, the network management apparatus  10  can also be realized by a known computer in which a program including procedures shown in flow charts to be described later has been installed via a medium or a communication line and which is either a combination of the computer and the Spec DB  12  and the Entity DB  13  or the computer including the Spec DB  12  and the Entity DB  13 . Details of the hardware configuration of the network management apparatus  10  will be described later. 
     Next, details of the network management apparatus  10  will be described. 
     First, registration of facility information (Spec (Specification) and an Entity) will be described.  FIG.  16    is a sequence chart showing an example of procedures for registering facility information by the network management apparatus according to the embodiment of the present invention. 
     First, when an operator performs an operation related to the registration of facility information (Spec) along a management screen, the facility information (Spec) is registered to the Spec DB  12  and, as a result of the registration, a code is returned to the management screen and a registration result is returned to an operator-side display screen. 
     Next, a Spec (physical layer) of the facility information will be described.  FIG.  17    is a diagram showing, in a table format, an example of Spec (facility layer and physical layer) of facility information retained by the network management apparatus according to the embodiment of the present invention. 
     In the physical layer, an attribute that is unique information such as an apparatus name or a cable type is retained in the Spec DB  12  as information in which a Spec (Specification) class (an attribute indicating a characteristic is defined) has been instantiated. 
     Specifically, the following Spec classes are defined. 
     The Specs are mainly used to display an NW configuration. 
     “Spec name: meaning” in the facility layer is as follows.
         PS Spec (Physical Structure Specification): an attribute unique to each PS is defined   AS Spec (Aggregate Section Specification): an attribute unique to each AS is defined       

     “Spec name: meaning” in the physical layer is as follows.
         PD Spec (Physical Device Specification): an attribute unique to each PD is defined   PP Spec (Physical Port Specification): an attribute unique to each PP is defined   PL Spec (Physical Link Specification): an attribute unique to each PL is defined   PC Spec (Physical Connector Specification): an attribute unique to each PC is defined       

     Next, a Spec (logical layer) of the facility information will be described.  FIG.  18    is a diagram showing, in a table format, an example of Spec (logical layer) of facility information retained by the network management apparatus according to the embodiment of the present invention. 
     In the logical layer, an attribute (a VLAN ID (Virtual LAN IDentifier), an IP address (Internet Protocol address), a wavelength number, or the like) which is unique to each layer is retained in the Spec DB  12  as information in which each Spec class has been instantiated. Specifically, the following Spec classes are defined. 
     “Spec name: meaning” in the logical layer is as follows.
         TL Spec (Topological Link Specification): an attribute unique to each TL is defined   NFD Spec (Network Forwarding Domain Specification): an attribute unique to each NFD is defined   TPE Spec (Termination Point Encapsulation Specification): an attribute unique to each TPE is defined   NC Spec (Network Connection Specification): an attribute unique to each NC is defined   LC Spec (Link Connect Specification): an attribute unique to each LC is defined   XC Spec (Cross (X) Connect Specification): an attribute unique to each XC is defined       

     Next, a method of use of a Spec class and an Entity class (a class of which an attribute value is defined) will be described.  FIG.  19    is a diagram showing an example of use of a Spec class and an Entity class by the network management apparatus according to the embodiment of the present invention. 
     As shown in  FIG.  19   , an attribute common to a layer and a value thereof are retained in the Entity DB  13  as information in which an Entity class has been instantiated. 
     A single Specification class in a Spec class is associated with n-number of SpecCharacteristic classes and n-number of Entity classes. A SpecCharacteristic class includes a name, valueFrom, valueTo, and Type to be described later. 
     An Entity class includes “status: String” and “position (int, int)”. A single Entity class is associated with n-number of CharacteristicValue classes (an external class of the Entity class which stores any one specific characteristic having been realized among characteristics defined in the SpecCharacteristic class). 
     A CharacteristicValue class includes a CharacteristicName and a Value to be described later. 
     An attribute name that is unique to the layer is retained in the Spec DB  12  as information in which a SpecCharacteristic class (an external class of a Specification class) has been instantiated. 
     An attribute value that is unique to the layer is retained in the Spec DB  12  as information in which a CharacteristicValue has been instantiated. It should be noted that an attribute name is defined in the SpecCharacteristic class. 
     Next, schemas of the Spec DB and the Entity DB will be described.  FIG.  20    is a diagram showing, in a table format, an example of a schema of a Specificication table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
     Schemas (column name: type) of the Specificication table retained in the Spec DB  12  are as follows (refer to Specificication in  FIG.  19   ).
         Entity: external key   SpecCharacteristic: external key       

       FIG.  21    is a diagram showing, in a table format, an example of a schema of a SpecCharacteristic table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
     Schemas (column name: type) of the SpecCharacteristic table retained in the Spec DB  12  are as follows (refer to SpecCharacteristic in  FIG.  19   ).
         Name: String   ValueFrom: int   ValueTo: int   Type: String       

       FIG.  22    is a diagram showing, in a table format, an example of a schema of an Entity table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
     Schemas (column name: type) of the Entity table retained in the Entity DB  13  are as defined in Entity. 
       FIG.  23    is a diagram showing, in a table format, an example of a schema of a CharacteristicValue table of facility information which is defined by the network management apparatus according to the embodiment of the present invention. 
     Schemas (column name: type) of the CharacteristicValue table retained in the Entity DB  13  are as follows (refer to CharacteristicValue in  FIG.  19   ).
         SpecCharacteristic (external key): —   CharacteristicName: String   value: String       

     Next, a registration method of a Spec will be described. 
     (1) Spec of facility information shown in  FIGS.  17  and  18    is created as a table in the Spec DB  12  in formats of Specification and SpecCharacteristic shown in  FIG.  19   . For example, with respect to PS Spec shown in  FIG.  17   , the SpecCharacteristic table shown in  FIG.  19    is managed as a plurality of tables by an external key. The SpecCharacteristic table is constituted of four attributes (refer to  FIG.  19   ), namely, name (a name of a characteristic), valueFrom (an upper limit of a specific value allowed by the characteristic), valueTo (a lower limit of the specific value allowed by the characteristic), and type (a type of the specific value of the characteristic). 
     (2) An attribute necessary for a unique value in the logical layer to be stored in the Spec DB  12  is set to the name attribute (refer to  FIG.  19   ) of SpecCharacteristic. 
     (3) A type set by the name attribute is set to the type attribute (refer to  FIG.  19   ) of SpecCharacteristic. 
     (4) When a prerequisite for a value to be set to an attribute necessary for a unique value in the logical layer to be stored in the Spec DB  12  is required, the condition is set to the valueFrom and valueTo attributes (refer to  FIG.  19   ) of SpecCharacteristic. 
     Next, a registration method of an Entity will be described. 
     (1) The attributes of Entities described in  FIGS.  1  to  4    are created as a table in the Entity DB  13 . For example, in the case of the PD, PP, or PS Entity (refer to  FIGS.  1  and  2   ), a table is created by schemas constituted of two attributes, namely, a status and coordinates. 
     (2) A value common to the logical layer is stored in a record of a corresponding table in the Entity DB  13 . 
     (3) With an attribute necessary for a unique value in the logical layer to be stored, an attribute name set to the name attribute of SpecCharacteristic of a corresponding Spec is set to the CharacteristicName attribute of CharacteristicValue and a value thereof is set to the value attribute of CharacteristicValue (refer to  FIG.  19   ). 
     Next, an input of a failure location or the like will be described. 
     First, a correspondence relationship between an input (use case) of a failure location and functional units will be described.  FIG.  24    is a diagram showing an example of a configuration that functions with an input of a failure location in the network management apparatus according to the embodiment of the present invention. 
     As shown in  FIG.  24   , in an input of a failure location, the facility information registering unit  11  and the Entity DB  13  function. 
     Next, processing by the failure pass Entity acquiring unit  14  will be described. 
     (1) For example, among a drawing object displayed by the NW configuration display unit  16  on a display screen of the network configuration, the failure pass Entity acquiring unit  14  enables an operator to designate, one at a time, a plurality of failure passes via a GUI (Graphical User Interface) in accordance with an operation to an input apparatus such as a keyboard or a mouse. 
     (2) The failure pass Entity acquiring unit  14  acquires, with respect to one of the drawing objects of the plurality of designated failure passes, an Entity ID unique to each Entity from the Entity DB  13 . 
     (3) The failure pass Entity acquiring unit  14  accesses the Entity DB  13  using the acquired Entity ID as a key and acquires an Entity (hereinafter, sometimes referred to as a failure pass Entity) which corresponds to the failure pass. The acquired result is stored in a failure location Entity array. 
     Next, retrieval of a physical resource used by a failure pass will be described. 
       FIG.  25    is a diagram showing an example of a configuration that functions with a retrieval of a physical resource in the network management apparatus according to the embodiment of the present invention. 
     As shown in  FIG.  25   , in the retrieval of a physical resource, the Entity DB  13 , the failure pass Entity acquiring unit  14 , and the physical resource retrieving unit  15  function. 
     Next, processing from an input of a failure pass to a retrieval of a physical resource used by a failure pass will be described. 
       FIG.  26    is a flow chart showing an example of processing procedures from an input of a failure pass to a retrieval of physical and facility resources by the network management apparatus according to the embodiment of the present invention. 
     The physical resource retrieving unit  15  sets an index “i=1” and performs processing of S 11  to S 16  below until a condition “i&lt;failure pass Entity ID array length” is satisfied. 
     The physical resource retrieving unit  15  acquires a failure pass Entity corresponding to the failure pass Entity ID [i] from the Entity DB  13  (S 11 ). S 11  corresponds to an input of a failure pass. 
     The physical resource retrieving unit  15  acquires a PP Entity corresponding to the failure pass Entity acquired in S 11  from the Entity DB  13  (S 12 ). 
     The physical resource retrieving unit  15  acquires PD and PL Entities having the PP Entity acquired in S 12  from the Entity DB  13  (S 13 ). 
     The physical resource retrieving unit  15  acquires a PS Entity having the PD Entity acquired in S 13  from the Entity DB  13  (S 14 ). 
     The physical resource retrieving unit  15  acquires an AS Entity having the PL Entity acquired in S 13  from the Entity DB  13  (S 15 ). Processing from S 12  to S 15  corresponds to a retrieval of a physical resource used by a failure pass. Details of the processing from S 12  to S 15  will be provided later. 
     The physical resource retrieving unit  15  stores the PD, PS, and AS Entities acquired in S 13  to S 15  in a failure location Entity array (S 16 ). 
     After S 16 , when the index-related condition described above is not satisfied, the physical resource retrieving unit  15  sets an index “i=i+1” and returns to S 11 . When the condition is satisfied, the processing is terminated. 
     Next, a type of a failure location Entity array will be described.  FIG.  27    is a diagram showing, in a table format, an example of types of an array of failure location Entities to be applied by the network management apparatus according to the embodiment of the present invention. 
     Types of a failure pass Entity name, a PS EntityList (array), an AS EntityList (array), and a PD EntityList (array) of an array of failure location Entities are as follows. 
     (1) Failure pass Entity name: Object type 
     (2) PS EntityList (array): PS Entity type (array) 
     (3) AS EntityList (array): AS Entity type (array) 
     (4) PD EntityList (array): PD Entity type (array) 
     Next, as details of S 12 , a retrieval of a PP Entity will be described.  FIG.  28    is a flow chart showing an example of processing procedures of a retrieval of a PP Entity by the network management apparatus according to the embodiment of the present invention. 
     The physical resource retrieving unit  15  acquires an endPointList included in a failure pass Entity (LC or NC) from the Entity DB  13  (S 12   a ). Alternatively, in S 12   a , a failure pass Entity (XC) may be designated by an input operation by the operator and the physical resource retrieving unit  15  may acquire an endPointList included in the failure pass Entity (XC) from the Entity DB  13 . 
     The physical resource retrieving unit  15  sets an index “i=1” and performs processing of S 12   b  to S 12   d  below until a condition “i&lt;endPointList array length” is satisfied. 
     The physical resource retrieving unit  15  acquires an instance of a TPE Entity from the index i of the endPointList array from the Entity DB  13  and stores the acquired instance in a tpe instance (the instance of the TPE Entity) variable (S 12   b ). 
     The physical resource retrieving unit  15  determines whether or not a tpeRefList attribute included in the instance of the TPE Entity is null (S 12   c ). 
     When a determination of “Yes” is made in S 12   c , the physical resource retrieving unit  15  acquires an instance of a TPE Entity from an endPointList [i] array included in the tpe instance variable from the Entity DB  13  and stores the acquired instance in the tpe instance variable (S 12   d ). 
     After S 12   d , when the condition described above is not satisfied, the physical resource retrieving unit  15  sets an index “i=i+1” and returns to S 12   b.    
     When a determination of “No” is made in S 12   c , the physical resource retrieving unit  15  acquires an instance (also sometimes referred to as a PP instance) of a PP Entity from a ppRefList [i] array included in the tpe instance variable from the Entity DB  13  and stores the acquired instance in pPort (a pp instance variable) (S 12   e ). 
     When the condition described above is satisfied after S 12   d  or, after S 12   e , the physical resource retrieving unit  15  returns pPort to the processing in S 13  (S 12   f ) and the processing in S 12  is terminated. 
     Next, as details of S 13 , a retrieval of PD and PL Entities having the PP Entity retrieved in S 12  will be described.  FIG.  29    is a flow chart showing an example of processing procedures of a retrieval of PD and PL Entities by the network management apparatus according to the embodiment of the present invention. 
     The physical resource retrieving unit  15  stores the PP Entity retrieved in S 12  in the pp instance variable (S 13   a ). 
     The physical resource retrieving unit  15  extracts one record of an array (a pd.ppList array (refer to  FIG.  2   )) of PP Entities included in a PD Entity from the Entity DB  13  and stores the record in a pd instance (an instance of the PD Entity). 
     In addition, the physical resource retrieving unit  15  determines whether or not the PP instance retrieved in S 12  is included in the pd.ppList array (S 13   b ). 
     When a determination of “Yes” is made in S 13   b , the physical resource retrieving unit  15  stores the PD instance including the PP instance in a pdList array (S 13   c ). When a determination of “No” is made in S 13   b , a transition is made to S 13   b  related to another record of the pd.ppList array. 
     After S 13   c , S 13   b  and S 13   c  are iterated with respect to each record of the pd.ppList array until a condition “pd!=NULL” is satisfied or, in other words, records of the pd.ppList array being a determination target are exhausted. Accordingly, the retrieval of PD Entities having the PP Entity is performed. 
     When the condition “pd!=NULL” is satisfied after S 13   c , the physical resource retrieving unit  15  extracts one record of an array (a pc.ppList array (refer to  FIG.  2   )) of PP Entities included in a PC Entity from the Entity DB  13  and stores the record in a pc instance (an instance of the PC Entity). 
     In addition, the physical resource retrieving unit  15  determines whether or not the pp instance is included in the pc.ppList array (S 13   d ). 
     When a determination of “Yes” is made in S 13   d , the physical resource retrieving unit  15  stores the PC instance including the PP instance in a pcList array (S 13   e ). When a determination of “No” is made in S 13   d , a transition is made to S 13   d  related to another record of the pc.ppList array. 
     After S 13   e , the physical resource retrieving unit  15  extracts one record of an array (a pl.pcList array (refer to  FIG.  2   )) of PC Entities included in a PL Entity from the Entity DB  13  and stores the record in a pl instance (an instance of the PL Entity). 
     In addition, the physical resource retrieving unit  15  determines whether or not the pc instance is included in the pl.pcList array (S 13   f ). 
     When a determination of “Yes” is made in S 13   f , the physical resource retrieving unit  15  stores the PL instance including the PC instance in a plList array (S 13   g ). When a determination of “No” is made in S 13   f , a transition is made to S 13   f  related to another record of the pl.pcList array. 
     After S 13   g , S 13   f  and S 13   g  are iterated with respect to each record of the pl.pcList array until a condition “pl!=NULL” is satisfied or, in other words, records of the pl.pcList array being a determination target are exhausted. Accordingly, the retrieval of PL Entities having the PC Entity is performed. 
     By respectively performing a retrieval of a PC Entity including a PP Entity and a retrieval of a PL Entity including the PC Entity, as a result, a retrieval of the PL Entity including the PP Entity is performed. 
     When the condition “pl!=NULL” described above is satisfied after S 13   g , S 13   d  and S 13   e  are iterated with respect to each record of the pc.ppList array until a condition “pc!=NULL” is satisfied or, in other words, records of the pc.ppList array being a determination target are exhausted. Accordingly, the retrieval of PC Entities having the PP Entity is performed. 
     When the condition “pc!=NULL” is satisfied, the physical resource retrieving unit  15  returns the pdList after being stored in S 13   c  to the processing in S 14  and the processing in S 16 , returns the plList after being stored in S 13   g  to the processing in S 15  (S 13   h ), and the processing in S 13  is terminated. 
     Next, as details of S 14 , a retrieval of a PS Entity included in the PD Entity retrieved in S 13  will be described. 
       FIG.  30    is a flow chart showing an example of processing procedures of a retrieval of a PS Entity by the network management apparatus according to the embodiment of the present invention. 
     The physical resource retrieving unit  15  extracts one record of the pdList retrieved in S 13  and stores the record in a pd instance variable. 
     The physical resource retrieving unit  15  extracts one record of an array (a ps.pdList array (refer to  FIG.  1   )) of PD Entities included in a PS Entity from the Entity DB  13  and stores the record in a ps instance (an instance of the PS Entity). 
     In addition, the physical resource retrieving unit  15  determines whether or not the pd instance is included in the ps.pdList array (S 14   a ). 
     When a determination of “Yes” is made in S 14   a , the physical resource retrieving unit  15  stores the PS instance including the PD instance in a psList array (S 14   b ). When a determination of “No” is made in S 14   b , a transition is made to S 14   a  related to another record of the ps.pdList array. 
     After S 14   b , S 14   a  and S 14   b  are iterated with respect to each record of the ps.pdList array until a condition “ps!=NULL” is satisfied or, in other words, records of the ps.pdList array being a determination target are exhausted. 
     When the condition “ps!=NULL” described above is satisfied after S 14   b , S 14   a  and S 14   b  are iterated with respect to each record of the pdList array until a condition “pd!=NULL” is satisfied or, in other words, records of the pdList array being a target are exhausted. Accordingly, the retrieval of PS Entities having the PD Entity is performed. 
     When the condition “pd!=NULL” is satisfied, the physical resource retrieving unit  15  returns psList to the processing in S 16  (S 14   c ) and the processing in S 14  is terminated. 
     Next, as details of S 15 , a retrieval of an AS Entity having the PL Entity retrieved in S 13  will be described.  FIG.  31    is a flow chart showing an example of processing procedures of a retrieval of an AS Entity by the network management apparatus according to the embodiment of the present invention. 
     The physical resource retrieving unit  15  stores the plList Entity retrieved in S 13  in a pl instance variable (S 15   a ). 
     The physical resource retrieving unit  15  extracts one record of an array (an as.plList array) of PL Entities included in an AS Entity from the Entity DB  13  and stores the record in an as instance (an instance of the AS Entity). 
     In addition, the physical resource retrieving unit  15  determines whether or not the pl instance is included in the as.plList array (S 15   b ). 
     When a determination of “Yes” is made in S 15   b , the physical resource retrieving unit  15  stores the AS instance including the PL instance in an asList array (S 15   c ). When a determination of “No” is made in S 15   c , a transition is made to S 15   b  related to another record of the as.plList array. 
     After S 15   c , S 15   b  and S 15   c  are iterated with respect to each record of the as.plList array until a condition “as!=NULL” is satisfied or, in other words, records of the as.plList array being a determination target are exhausted. 
     When the condition “as!=NULL” described above is satisfied after S 15   c , the physical resource retrieving unit  15  returns asList to the processing in S 16  (S 15   d ) and the processing in S 15  is terminated. Accordingly, the retrieval of AS Entities having the PL Entity is performed. In addition, as described above, as S 16 , the physical resource retrieving unit  15  stores the pdList, the psList, and the asList acquired in S 13  to S 15  in a failure location Entity array. 
     Next, retrieval of a physical resource commonly used by a plurality of failure passes will be described.  FIG.  32    is a flow chart showing an example of processing procedures of a retrieval of a physical resource to be commonly used by the network management apparatus according to the embodiment of the present invention. 
     The physical resource retrieving unit  15  acquires the failure location Entity array stored in S 16  from the Entity DB  13  (S 21 ). 
     The physical resource retrieving unit  15  sets an index “j=1” and S 22  to S 24  below are iterated until a condition causing an element j of an array of a processing target among the acquired failure location Entity array becomes null. 
     The physical resource retrieving unit  15  determines, for each object of PD, PS, and AS EntityList arrays corresponding to the element j of the failure location Entity array, whether or not the object is present in a multiple/failure rate Entity array that is a processing target (S 22 ). 
     When a determination of “Yes” is made in S 22 , the physical resource retrieving unit  15  updates the multiplicity of the corresponding object in the multiple/failure rate Entity array by adding 1 thereto and stores the updated multiplicity in the multiple/failure rate Entity array that is a processing target (S 23 ). 
     When a determination of “No” is made in S 22 , the physical resource retrieving unit  15  sets the multiplicity of the corresponding object in the multiple/failure rate Entity array to 1 and stores the multiplicity in the multiple/failure rate Entity array that is a processing target (S 24 ). 
     After S 23  or S 24 , when the condition described above related to the index j is not satisfied, the physical resource retrieving unit  15  sets an index “j=j+1” and returns to S 22 . 
     After S 23  or S 24 , when the condition described above related to the index j is satisfied, the physical resource retrieving unit  15  calculates, for each object stored in the multiple/failure rate Entity array that is a processing target, the number of passes to be affected when a failure occurs in the object and stores “multiplicity/number of affected passes” in the failure rate of the multiple/failure rate Entity array (S 25 ). 
     The physical resource retrieving unit  15  returns the corresponding object in the multiple/failure rate Entity array and the multiple/failure rate Entity array in which the multiplicity and the failure rate related to the object are stored and the processing is terminated. Accordingly, a retrieval of a physical resource which is commonly used by a plurality of failure passes and calculation of a failure rate of the physical resource are performed. Alternatively, for example, a calculating unit that differs from the physical resource retrieving unit  15  may be provided in the network management apparatus  10  and processing related to the multiplicity and the failure rate may be performed by the calculating unit. 
       FIG.  33    is a diagram showing, in a table format, an example of types of an array of a multiple/failure rate Entity to be applied by the network management apparatus according to the embodiment of the present invention. 
     Types of a multiple Entity and multiplicity of the multiple/failure rate Entity arrays are as follows. 
     (1) Multiple Entity: Object 
     (2) Multiplicity: Int 
     (3) Failure rate: float 
       FIG.  34    is a diagram showing, in a table format, an example of an array of failure location Entities to be applied by the network management apparatus according to the embodiment of the present invention. 
     A failure pass Entity name, a PS EntityList, an AS EntityList, and a PD EntityList which are related to an array index “1” in the failure location Entity array shown in  FIG.  34    are as follows. 
     Failure pass Entity name: FRE (LC)_apparatus_ 2   
     PS EntityList: PS_A, PS_D 
     AS EntityList: AS_ 2   
     PD EntityList: PD_apparatus_ 3 , PD_apparatus_ 4   
     A failure pass Entity name, a PS EntityList, an AS EntityList, and a PD EntityList which are related to an array index “2” in the failure location Entity array shown in  FIG.  34    are as follows. 
     Failure pass Entity name: FRE (LC)_apparatus_ 3   
     PS EntityList: PS_A, PS_F 
     AS EntityList: AS_ 2   
     PD EntityList: PD_apparatus_ 5 , PD_apparatus_ 6   
     In this example, with respect to the PS EntityList and the AS EntityList, PS_A and AS_ 2  are respectively multiply present between the array indices “1” and “2” (refer to a and b in  FIG.  34   ), and PS_A and AS_ 2  correspond to physical resources multiply used by a plurality of failure passes (the FRE (LC)_apparatus_ 2  and the FRE (LC)_apparatus_ 3 ). It should be noted that, in the example described above, the PD EntityList is not multiply present between the array indices “1” and “2” (refer to c in  FIG.  34   ). 
     The NW configuration display unit  16  highlights and displays a drawing object corresponding to the physical resource retrieved by the physical resource retrieving unit  15  in S 12  to S 15  by, for example, distinguishing colors on a screen so that the drawing object is distinguished from a drawing object corresponding to other resources in the network configuration. 
     For example, the NW configuration display unit  16  acquires all Entities of the facility layer and the physical layer in the network configuration from the Entity DB  13  and acquires pieces of Spec information corresponding to all of the Entities from the Spec DB  12  as a Spec array. 
     The NW configuration display unit  16  acquires two-dimensional coordinates (refer to  FIGS.  1  to  3   ) indicating a position of each Entity from the Entity DB  13  and displays a drawing object of the facility layer and the physical layer at a position corresponding to the acquired coordinates on the screen. Drawing based on coordinate information of an object is also described in WO 2019/167801. 
     In this case, among the two-dimensional coordinates, the NW configuration display unit  16  acquires two-dimensional coordinates indicating a position of the PD, PS, and AS Entities stored in the failure location Entity array in S 16  and highlights and displays a drawing object at this position in, for example, red so that the drawing object is distinguished from other objects. 
     In addition, among the drawing objects, the NW configuration display unit  16  highlights and displays a drawing object corresponding to a physical resource (a physical layer and a facility layer) used by a plurality of failure passes in, for example, blue so that the drawing object is distinguished from other objects. 
     Furthermore, colors to be highlighted and displayed may be distinguished from each other in accordance with a magnitude of multiplicity and a magnitude of a failure rate at the same multiplicity. In addition, among information objects to be highlighted and displayed, information objects related to the same multiplicity may be displayed by distinguishing tones or the like so that magnitudes of the failure rate are distinguished. 
       FIG.  35    is a block diagram showing an example of a hardware configuration of the network management apparatus according to the embodiment of the present invention. 
     In the example shown in  FIG.  35   , the network management apparatus  10  according to the embodiment described above is constituted of, for example, a server computer or a personal computer and includes a hardware processor  111 A such as a CPU. In addition, with respect to the hardware processor  111 A, a program memory  111 B, a data memory  112 , an input/output interface  113 , and a communication interface  114  are connected via a bus  120 . 
     The communication interface  114  includes, for example, one or more wireless communication interface units and enables transmission and reception of information to and from the communication network NW. As the wireless interface, for example, an interface adopting a low-power wireless data communication standard such as wireless LAN (Local Area Network) is used. 
     An input device  20  and an output device  30  to be used by an operator which are annexed to the network management apparatus  10  are connected to the input/output interface  113 . 
     The input/output interface  113  performs processing of fetching operation data input by the operator through the input device  20  which is a keyboard, a touch panel, a touchpad, a mouse, or the like and outputting output data to the output device  30  including a display device using liquid crystals or organic EL (Electro Luminescence) and causes the output device  30  to display the output data. It should be noted that devices built into the network management apparatus  10  may be used as the input device  20  and the output device  30  and, in addition, an input device and an output device of another information terminal that is capable of communicating with the network management apparatus  10  via the network NW may be used. 
     As a non-transitory tangible storage medium, the program memory  111 B uses, for example, a combination of a non-volatile memory that enables random write and read such as an HDD (hard disk drive) or an SSD (solid state drive) and a non-volatile memory such as a ROM (read only memory) and stores a program necessary for executing various steps of control processing according to the embodiment. 
     As a tangible storage medium, the data memory  112  uses, for example, a combination of the non-volatile memory described above and a volatile memory such as a RAM (random access memory) and is used to store various pieces of data acquired and created while performing the various steps of processing. 
     The network management apparatus  10  according to the embodiment of the present invention can be constituted of, as software-based processing functional units, a data processing apparatus including the facility information registering unit  11 , the Spec DB  12 , the Entity DB  13 , the failure pass Entity acquiring unit  14 , the physical resource retrieving unit  15 , and the NW configuration display unit  16  shown in  FIG.  15   . 
     The Spec DB  12  and the Entity DB  13  can be constructed by using the data memory  112  shown in  FIG.  35   . However, these regions are not essential components inside the network management apparatus  10  and, for example, the regions may be provided in an external storage medium such as an USB (universal serial bus) memory or in a storage apparatus such as a database server arranged in the cloud. 
     All of the processing functional units in the respective units of the facility information registering unit  11 , the failure pass Entity acquiring unit  14 , the physical resource retrieving unit  15 , and the NW configuration display unit  16  can be realized by having the hardware processor  111 A read a program stored in the program memory  111 B and execute the program. It should be noted that a part of or all of the processing functional units may be realized by various other formats including an Application Specific Integrated Circuit (ASIC) or a Field-Programmable Gate Array (FPGA). 
     As described above, when a failure occurs on a logical layer of a communication network, the network management apparatus according to the embodiment of the present invention is capable of specifying a candidate of a facility to be a failure cause by retrieving an object of a physical layer and a facility layer which corresponds to a failure pass. 
     In addition, when a failure occurs on a plurality of passes, the network management apparatus can retrieve an object of the physical layer and the logical layer which is multiply used by a plurality of failure passes. 
     Furthermore, the network management apparatus calculates, for each information object related to the candidate of a facility to be the failure cause, the number of information objects which are associated with the object and which are related to a plurality of occurrence paths of the failure as a multiplicity and calculates, for each information object related to the candidate of a facility to be the failure cause, a failure rate being a proportion of the multiplicity with respect to the number of information objects in the logical layer which are affected when the failure occurs in the object, and information that is promising as a candidate of the failure location can be specified based on the failure rate. 
     In addition, the method described in each embodiment can be stored, as a program (software means) which can be executed by a computer, in a recording medium such as a magnetic disk (a Floppy disk (registered trademark), a hard disk, or the like), an optical disc (a CD-ROM, a DVD, an MO, or the like), or a semiconductor memory (a ROM, a RAM, a Flash memory, or the like) or transmitted and distributed using a communication medium. The program to be stored on the medium side includes a configuration program that causes software means (including tables and data structures in addition to an executable program) to be executed by a computer to be constructed in the computer. The computer that realizes the present apparatus executes the processing described above by reading the program recorded in the recording medium and, in some cases, constructing the software means using the configuration program, and causing the software means to control operations. A recording medium as used in the present specification is not limited to a recording medium for distribution and includes a storage medium such as a magnetic disk or a semiconductor memory provided in a device inside the computer or connected to the computer via a network. 
     The present invention should not be limited to the embodiments described above and can be modified in various ways in an implementation stage without departing from the scope of the invention. In addition, the respective embodiments may be implemented in combination, in which case combined effects can be produced. Furthermore, the embodiments described above include various inventions and the various inventions can be extracted according to combinations selected from the plurality of disclosed constituent elements. For example, even when some constituent elements are deleted from all of the constituent elements described in the embodiments, when the problem can be solved and the effects can be produced, a configuration from which the constituent elements have been deleted can be extracted as an invention. 
     REFERENCE SIGNS LIST 
     
         
           11  Facility information registering unit 
           12  Spec DB (database) 
           13  Entity DB 
           14  Failure pass Entity acquiring unit 
           15  Physical resource retrieving unit 
           16  NW configuration display unit