Abstract:
The objective of the invention is to enable sharing, between layers in a network in which the layers are used to perform communications, resource information and information required for using paths. A network control system includes: a lower layer information storage unit, a lower layer control information conversion unit, an upper layer information storage unit, an upper layer control information conversion unit, an integrated layer information storage unit and a layer integration unit. The layer integration unit integrates, as virtual links, the information of flows, which are representative of communications among terminals in the lower layer, with the network information of the upper layer, thereby constituting the network information of the integrated layer. Further, the layer integration unit performs reciprocal exchanges of network information among the integrated layer information storage unit, the lower layer information storage unit and the upper layer information storage unit, said reciprocal exchanges including a process of giving, as the attribute information of the ports of the upper layer, label information required for using the virtual link provided by the lower layer.

Description:
TECHNICAL FIELD 
     Description of Related Application 
       [0001]    The present invention is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-221235, filed on Oct. 30, 2014, and the entire contents stated in the application are incorporated herein by reference. 
         [0002]    The present invention relates to a network control system, a control device, a network information management method, and a program, and particularly relates to a network control system, a control device, a network information management method, and a program for performing communication by using a plurality of layers. 
       BACKGROUND ART 
       [0003]    PTL 1 describes an example of a system for controlling a multilayer network. A policy-based communication management system in PTL 1 includes, in each layer of a communication network constituted of a plurality of access networks and a core network: a means that stores a management policy; and a policy management means that manages a layer in accordance with the management policy. Further, in the policy-based communication management system, the policy management means searches for the management policy upon occurrence of an event on a layer. The policy management means includes: a means that issues an action request to a policy management means on a server layer while assuming that the own layer serves as a client and the other layer serves as the server layer, when an action of a management policy matching with a condition of the event is not an action of the own layer. The policy management means further includes: a means that returns a response to an action request to a policy management means on a client layer, when the action is not an action of the own layer as a result of searching for the management policy by the policy management means having received the action request as a server layer. The policy management means further includes: a means that performs policy management in accordance with the management policy of the own layer, when being notified of an execution result of an action request from the other layer. 
         [0004]    PTL 2 discloses a virtual network connection device that is expected to be able to facilitate setting work in connecting two virtual networks. PTL 2 discloses a method of copying mapping information indicating a correspondence relationship of a virtual link between two virtual networks and physical interface information associated with the virtual link and rewriting the mapping information as needed. The method thereby facilitates setting of a control device controlling a virtual network to be connected. 
       CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Unexamined Patent Application Publication No. 2002-84280 
     PTL 2: Japanese Unexamined Patent Application Publication No. 2013-157855 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    The following analysis is given according to the present invention. A first problem in PTL 1 is that there is not disclosed means that knows resource information on a certain layer from another layer. This is because the policy-based communication management system in PTL 1 implements control of each layer as a policy and performs inter-layer linkage in a form of request and response for policy application. 
         [0006]    In addition, a second problem in PTL 1 is that there is not disclosed handover of label information necessary in using a new path generated on a lower layer. In general, a network is constituted of various devices and a control means varies for each layer and each domain. Thus, label information for using a path provided by a lower layer also varies. Without means of sharing this information, a method of using a path of a lower layer is unknown from an upper layer, and inter-layer linkage and automatization thereof are almost impossible. 
         [0007]    An object of the present invention is to provide a network control system, a control device, a network information management method, and a program that can contribute to sharing inter-layer resource information and information necessary for using a path in a network for performing communication using a plurality of layers. 
       Solution to Problem 
       [0008]    According to a first aspect, provided is a network control system. The system includes: lower layer data transfer unit that performs communication of a lower layer; a lower layer information storage unit that stores network information of the lower layer; a lower layer control information conversion unit that updates, based on network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit, network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit; an upper layer data transfer unit that performs communication of an upper layer; an upper layer information storage unit that stores network information of the upper layer; an upper layer control information conversion unit that updates, based on network information in the upper layer information storage unit and a setting and a status of a switch for an upper layer, network information in the upper layer information storage unit and a setting and a status of the upper layer data transfer unit; an integrated layer information storage unit that stores network information of an integrated layer obtained by integrating network information of the lower layer with network information of the upper layer; and a layer integration unit that configures network information of the integrated layer by integrating network information of the upper layer with information on a flow representing point-to-point communication of the lower layer as a virtual link, and performs reciprocal exchange of network information in the integrated layer information storage unit, in the lower layer information storage unit, and in the upper layer information storage unit, the reciprocal exchange including processing of assigning, as attribute information of a port of an upper layer, label information necessary for using a virtual link provided by a lower layer. 
         [0009]    According to a second aspect, provided is a control device connected with a lower layer data transfer unit that performs communication of a lower layer and an upper layer data transfer unit that performs communication of an upper layer. The device includes: a lower layer data transfer unit that performs communication of the lower layer; a lower layer information storage unit that stores network information of the lower layer; a lower layer control information conversion unit that updates, based on network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit, network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit; an upper layer data transfer unit that performs communication of the upper layer; an upper layer information storage unit that stores network information of the upper layer; an upper layer control information conversion unit that updates, based on network information in the upper layer information storage unit and a setting and a status of a switch for an upper layer, network information in the upper layer information storage unit and a setting and a status of the upper layer data transfer unit; an integrated layer information storage unit that stores network information of an integrated layer obtained by integrating network information of the lower layer with network information of the upper layer; and a layer integration unit that configures network information of the integrated layer by integrating network information of the upper layer with information on a flow representing point-to-point communication of the lower layer as a virtual link, and performs reciprocal exchange of network information in the integrated layer information storage unit, in the lower layer information storage unit, and in the upper layer information storage unit, the reciprocal exchange including processing of assigning, as attribute information of a port of an upper layer, label information necessary for using a virtual link provided by a lower layer. 
         [0010]    According to a third aspect, provided is a network information management method, by a control device connected with a lower layer data transfer unit that performs communication of a lower layer and an upper layer data transfer unit that performs communication of an upper layer. The control device includes: a lower layer information storage unit that stores network information of the lower layer; a lower layer control information conversion unit that updates, based on network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit, network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit; an upper layer information storage unit that stores network information of the upper layer; an upper layer control information conversion unit that updates, based on network information in the upper layer information storage unit and a setting and a status of a switch for an upper layer, network information in the upper layer information storage unit and a setting and a status of the upper layer data transfer unit; and an integrated layer information storage unit that stores network information of an integrated layer obtained by integrating network information of the lower layer with network information of the upper layer. 
         [0011]    The method includes steps of: 
         [0012]    configuring network information of the integrated layer by integrating network information of the upper layer with information on a flow representing point-to-point communication of the lower layer as a virtual link; and performing reciprocal exchange of network information in the integrated layer information storage unit, in the lower layer information storage unit, and in the upper layer information storage unit, the reciprocal exchange including processing of assigning, as attribute information of a port of an upper layer, label information necessary for using a virtual link provided by a lower layer. 
         [0013]    According to a fourth aspect, provided is a computer program executed by a control device, configured by a computer, connected with a lower layer data transfer unit that performs communication of a lower layer and an upper layer data transfer unit that performs communication of an upper layer. The computer includes: a lower layer information storage unit that stores network information of the lower layer; a lower layer control information conversion unit that updates, based on network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit, network information in the lower layer information storage unit and a setting and a status of the lower layer data transfer unit; an upper layer information storage unit that stores network information of the upper layer; an upper layer control information conversion unit that updates, based on network information in the upper layer information storage unit and a setting and a status of a switch for an upper layer, network information in the upper layer information storage unit and a setting and a status of the upper layer data transfer unit; and an integrated layer information storage unit that stores network information of an integrated layer obtained by integrating network information of the lower layer with network information of the upper layer. 
         [0014]    The program includes processes of: 
         [0015]    configuring network information of the integrated layer by integrating network information of the upper layer with information on a flow representing point-to-point communication of the lower layer as a virtual link; and performing reciprocal exchange of network information in the integrated layer information storage unit, in the lower layer information storage unit, and in the upper layer information storage unit, the reciprocal exchange including processing of assigning, as attribute information of a port of an upper layer, label information necessary for using a virtual link provided by a lower layer. Note that the program may be recorded in a computer-readable (non-transient) storage medium. In other words, the present invention may be also embodied as a computer program product. 
       Advantageous Effects of Invention 
       [0016]    The present invention makes it possible to contribute to sharing inter-layer resource information and information necessary for using a path in a network for performing communication using a plurality of layers. In other words, the present invention also intends to convert a network control system and a control device to include a function of integrated display through visualization with a more preferred mode. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is a diagram illustrating a configuration of a system according to a first example embodiment of the present invention; 
           [0018]      FIG. 2  is a flowchart representing an operation of the system according to the first example embodiment of the present invention; 
           [0019]      FIG. 3  is a flowchart representing an operation when the system according to the first example embodiment of the present invention accepts a setting of boundary information; 
           [0020]      FIG. 4  is a flowchart representing an operation when the system according to the first example embodiment of the present invention accepts a setting of a flow of a lower layer; 
           [0021]      FIG. 5  is a flowchart representing a flow setting operation of an integrated layer performed by the system according to the first example embodiment of the present invention; 
           [0022]      FIG. 6  is a flowchart representing a flow setting operation of an upper layer performed by the system according to the first example embodiment of the present invention; 
           [0023]      FIG. 7  is a diagram for describing a creation process of network information of the integrated layer to be created by the system according to the first example embodiment of the present invention; 
           [0024]      FIG. 8  is a diagram illustrating a configuration of a system according to a second example embodiment of the present invention; 
           [0025]      FIG. 9  is a diagram illustrating an example of boundary information for use in the second example embodiment of the present invention; 
           [0026]      FIG. 10  is a diagram illustrating an example of attribute information of ports covered in the second example embodiment of the present invention; 
           [0027]      FIG. 11  is a diagram illustrating an example of flow information to be stored in a network database for integrated layer (NWDB for integrated layer) according to the second example embodiment of the present invention; and 
           [0028]      FIG. 12  is a diagram illustrating an example of flow information set in an OpenFlow switch according to the second example embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Example Embodiment 
       [0029]    Now, a first example embodiment of the present invention is described in detail with reference to the drawings.  FIG. 1  is a diagram illustrating a configuration of a network control system according to the first example embodiment of the present invention. Referring to  FIG. 1 , a configuration is illustrated in which a computer  100 A is connected with a lower layer data transfer unit  500  that performs communication of a lower layer and upper layer data transfer units  501  and  502  that each perform communication of an upper layer via the lower layer data transfer unit  500 . 
         [0030]    The computer  100 A (central processing unit; processor; data processing device) includes an integrated layer information storage unit  302 , a layer integration unit  200 , a lower layer information storage unit  300 , an upper layer information storage unit  301 , a lower layer control information conversion unit  400 , and an upper layer control information conversion unit  401 . 
         [0031]    The lower layer information storage unit  300  stores (holds) network information of a lower layer. The “network information of a lower layer” herein includes network topology information (hereinafter, referred to as “topology information”) and flow information representing point-to-point communication. The topology information is described by using a connection relationship between nodes or ports, links, and the like of a lower layer. In addition, in the present example embodiment, the “network information of a lower layer” also includes information on some of packets flowing through a network, and attribute information of the packets. These pieces of the network information are registered by the lower layer control information conversion unit  400  to be described later, and may be registered and updated by a person, a program, or the like. 
         [0032]    The lower layer control information conversion unit  400  acquires information relating to a setting and a status (hereinafter, “setting/status information”) of the lower layer data transfer unit  500  under management of the own unit. The lower layer control information conversion unit  400  then converts the information into network information and stores the network information in the lower layer information storage unit  300 . In addition, when storing (registration), updating, and deletion are performed at the lower layer information storage unit  300 , the lower layer control information conversion unit  400  updates and controls a setting and a status of the lower layer data transfer unit  500  in accordance with a processing of the storing, updating, and deletion. For example, the lower layer control information conversion unit  400  detects, based on information collected from the lower layer data transfer unit  500 , a change of network topology and updates topology information stored in the lower layer information storage unit  300 . In addition, when flow information stored in the lower layer information storage unit  300  changes, the lower layer control information conversion unit  400  performs setting change and control on the lower layer data transfer unit  500  in accordance with the change of the flow information. 
         [0033]    The upper layer information storage unit  301  stores network information of an upper layer. The “network information of an upper layer” herein includes topology information described by using a connection relationship between nodes or ports, and links of an upper layer, flow information representing point-to-point communication, information on some of packets flowing through a network, and the like. The flow information of an upper layer herein includes a match condition such as a port and a header, and an action such as an output destination (output port) of a flow conforming to the match condition and a content of header conversion. The flow information of an upper layer also includes link information (path information) through which a flow passes, and the like. 
         [0034]    The upper layer control information conversion unit  401  acquires pieces of setting/status information from the upper layer data transfer units  501  and  502 , converts the information into network information, and stores the network information in the upper layer information storage unit  301 . In addition, when storing, updating, and deletion are performed at the upper layer information storage unit  301 , the upper layer control information conversion unit  401  updates and controls settings and statuses of the upper layer data transfer units  501  and  502  in accordance with a processing of the storing, updating, and deletion. 
         [0035]    The layer integration unit  200  performs a reciprocal exchange operation between a content of the integrated layer information storage unit  302  and pieces of network information in the lower layer information storage unit  300  and the upper layer information storage unit  301 . Specifically, the layer integration unit  200  refers to pieces of information in the lower layer information storage unit  300  and the upper layer information storage unit  301 . The layer integration unit  200  then integrates network information of an upper layer with flow information of a lower layer as a virtual link, and configures network information of an integrated layer. The configured network information is stored in the integrated layer information storage unit  302 . In addition, the layer integration unit  200  stores virtual ports between nodes of an upper layer and information on the virtual link in association with each other as attribute information of the upper layer information storage unit  301 . Further, the layer integration unit  200  decomposes flow information stored in the integrated layer information storage unit  302  into two or more flows as needed and stores the two or more flows in the upper layer information storage unit  301 . 
         [0036]    In addition, when configuring the network information of the integrated layer, the layer integration unit  200  refers to connection information (hereinafter, referred to as “boundary information”) between a port of a lower layer and a port of an upper layer (see  FIG. 8 ). 
         [0037]    The lower layer data transfer unit  500  is configured by a switch or the like that transfers data in accordance with a transfer rule set by the lower layer control information conversion unit  400 . 
         [0038]    The upper layer data transfer units  501  and  502  each transfer data in accordance with a rule set by the upper layer control information conversion unit  401 . 
         [0039]    Note that each of the units (processing means) of the computer  100 A illustrated in  FIG. 1  can be also implemented by a computer program causing the computer  100 A to execute each of the above-described processing using hardware of the computer  100 A. In addition, in the example of  FIG. 1 , the processing means are arranged in the single computer  100 A, but a plurality of computers can also be used to form a configuration equivalent to that of the computer  100 A in  FIG. 1 . For example, it is also possible to employ a configuration in which different computers carrying functions equivalent to those of the layer integration unit  200 , the lower layer control information conversion unit  400 , and the upper layer control information conversion unit  401  are connected. 
         [0040]    Now, an operation of the present example embodiment is described in detail with reference to the drawings. In the following description, it is assumed that network information at an initial state is set as follows. The lower layer information storage unit  300  stores a setting and a status of the lower layer data transfer unit  500  stored by the lower layer control information conversion unit  400 . The upper layer information storage unit  301  holds settings and statuses of the upper layer data transfer units  501  and  502  stored by the upper layer control information conversion unit  401 . In addition, the integrated layer information storage unit  302  stores topology information (before integration) stored by the upper layer information storage unit  301  (see  FIG. 7( a ) ). 
         [0041]    First, boundary information is input and set (S 10  in  FIG. 2 ). When boundary information is input and set, the layer integration unit  200  refers to the boundary information. The layer integration unit  200  then designates a plurality of sets of ports of respective layers, being at a boundary from among pieces of network information stored in the lower layer information storage unit  300  and the upper layer information storage unit  301  (S 100  in  FIG. 3 ). Next, the layer integration unit  200  deletes the designated ports included in the boundary information from topology information in the integrated layer information storage unit  302  (see S 101  in  FIG. 3 , and  FIG. 7( b ) ). 
         [0042]    Next, a flow is stored in the lower layer information storage unit  300  (S 20  in  FIG. 2 ). When a flow is stored in the lower layer information storage unit  300  (S 200  in  FIG. 4 ), the layer integration unit  200  confirms whether or not an input port and an output port of the flow are included in the boundary information (S 201  in  FIG. 4 ). When an input port and an output port of the flow are not included in the boundary information (No at S 201  in  FIG. 4 ), the layer integration unit  200  regards the flow as normal flow storing and does not perform any particular operation. On the other hand, the lower layer information storage unit  300  notifies the lower layer control information conversion unit  400  of addition of the flow (S 204  in  FIG. 4 ). The lower layer control information conversion unit  400  controls the lower layer data transfer unit  500  in accordance with the notification. 
         [0043]    On the other hand, when an input port and an output port of the flow are included in the boundary information as a result of confirmation at S 201  in  FIG. 4  (Yes at S 201  in  FIG. 4 ), the layer integration unit  200  adds, to the topology information in the integrated layer information storage unit  302 , a virtual link related to the flow and virtual ports necessary for connecting the link (see S 202  in  FIG. 4 , and  FIG. 7( c ) ). 
         [0044]    Next, the layer integration unit  200  refers to the boundary information and derives ports connected with the input port and the output port of the flow in the lower layer information storage unit  300  stored at Step S 200  in  FIG. 4 . The ports are derived from among the pieces of the topology information in the upper layer information storage unit  301 . Then, the layer integration unit  200  stores, as an attribute of the derived ports, the virtual link, and label information and information on virtual ports necessary for using the link (see S 203  in  FIG. 4 , and  FIG. 9 ). Thereafter, the processing ends after passing via Step S 204  in  FIG. 4 . Note that changing the order of the above-described Steps S 202 , S 203 , and S 204  in  FIG. 4  is not a problem. For example, notification of flow addition for the lower layer control information conversion unit  400  may be performed first. 
         [0045]    Further, the flow is stored in the integrated layer information storage unit  302  (S 30  in  FIG. 2 ). First, when the flow is stored in the integrated layer information storage unit  302  (S 300  in  FIG. 5 ), the layer integration unit  200  refers to the topology information in the integrated layer information storage unit  302  and extracts a virtual link through which the flow passes. Next, the layer integration unit  200  stores, in the upper layer information storage unit  301 , the flow decomposed for use in the upper layer data transfer unit  501  and for use in the upper layer data transfer unit  502  (S 301  in  FIG. 5 ). Note that when decomposing the flow for use in the upper layer data transfer unit  501  and for use in the upper layer data transfer unit  502 , the input port and the output port are changed by using the boundary information. Next, the upper layer information storage unit  301  notifies the upper layer control information conversion unit  401  of storing of the decomposed flow (S 302  in  FIG. 5 ). 
         [0046]    Finally, the flow is stored in the upper layer in accordance with the notification of the flow storing (S 40  in  FIG. 2 ). First, the upper layer control information conversion unit  401  receives, from the upper layer information storage unit  301 , setting information (including the label information) on the virtual ports and the virtual link set as an attribute in the ports of the stored flow (S 400  in  FIG. 6 ). Next, the upper layer control information conversion unit  401  receives, from the upper layer information storage unit  301 , setting information on the flow decomposed at Step S 301  in  FIG. 5  (S 401  in  FIG. 6 ). Finally, the upper layer control information conversion unit  401  generates a transfer rule for an upper layer transfer node by using the label information stored along with the information on the virtual ports and the virtual link and the flow information. The upper layer control information conversion unit  401  then sets the transfer rule in the upper layer data transfer units  501  and  502  (S 402  in  FIG. 6 ). As a result of the above, the flow stored in the integrated layer information storage unit  302  is decomposed into two pieces of flow information at the upper layer, and instructions are given to the upper layer data transfer units  501  and  502 . 
         [0047]    As described above, the present example embodiment is configured as follows. The upper layer control information conversion unit  401  is able to change a label necessary for passing data of the upper layer data transfer units  501  and  502  through a virtual link configured over the lower layer data transfer unit  500 . The upper layer control information conversion unit  401  is also able to change a way of assigning the label in accordance with functions of the upper layer data transfer units  501  and  502 . The label and the way of assigning the label are changed by using information on virtual ports and a virtual link stored as attribute information of the upper layer information storage unit. This configuration makes it possible to exchange the lower layer data transfer unit  500  and the upper layer data transfer units  501  and  502  with other devices. This exchange can be performed without influencing on a control function of referring to the lower layer information storage unit  300 , the upper layer information storage unit  301 , and the integrated layer information storage unit  302 . In addition, this configuration also results in realizing reduction in development cost of a network control function. 
       Second Example Embodiment 
       [0048]    Now, a second example embodiment configured by replacing the configuration of the above first example embodiment with more specific devices is described. In the following, basic configurations and operations are the same as those in the first example embodiment, therefore, the description will be focused on different points from the first example embodiment. 
         [0049]      FIG. 8  is a diagram illustrating a configuration of a system according to the second example embodiment of the present invention. Referring to  FIG. 8 , a configuration is illustrated in which a multistage network including OpenFlow switches  1502  and  1503  equivalent to the upper layer transfer unit in the first example embodiment and transport (TP) switches  1500  and  1501  equivalent to the lower layer transfer unit is connected with a control server  100  that controls the switches. In the present example embodiment, the control server  100  is equivalent to the computer  100 A in the above first example embodiment. 
         [0050]    A driver for transport  1400  is equivalent to the lower layer control information conversion unit  400  in the first example embodiment. The driver for transport  1400  performs an operation of storeing information on a transport network including the transport switches  1500  and  1501  in a network database (NWDB) for transport  1300 . Similarly, the driver for transport  1400  controls a transport network based on information updated at the NWDB for transport  1300 , the driver for transport  1400  serving as the lower layer control information conversion unit  400 . 
         [0051]    A driver for OpenFlow  1401  is equivalent to the upper layer control information conversion unit  401  in the first example embodiment. The driver for OpenFlow  1401  performs an operation of storeing information on an OpenFlow network including the OpenFlow switches  1502  and  1503  in a network database (NWDB) for OpenFlow  1301 . Similarly, the driver for OpenFlow  1401  controls an OpenFlow network based on information updated at the NWDB for OpenFlow  1301 . 
         [0052]    The NWDB for transport  1300 , which is equivalent to the lower layer information storage unit  300  in the first example embodiment, stores network information on a network for transport. 
         [0053]    The NWDB for OpenFlow  1301 , which is equivalent to the upper layer information storage unit  301  in the first example embodiment, stores network information on a network for OpenFlow. 
         [0054]    A layerizer  1200 , which is equivalent to the layer integration unit  200  in the first example embodiment, reciprocally exchanges pieces of information in the NWDB for transport  1300  and the NWDB for OpenFlow  1301  with information in a NWDB for integrated layer  1302 . Specifically, the layerizer  1200  integrates information in the NWDB for transport  1300  with information in the NWDB for OpenFlow  1301  and updates network information in the NWDB for integrated layer  1302 . In addition, the layerizer  1200  updates, upon transfer of the NWDB for integrated layer  1302 , the NWDB for transport  1300  or the NWDB for OpenFlow  1301  in accordance with a processing of the transfer. 
         [0055]    The NWDB for integrated layer  1302  is equivalent to the integrated layer information storage unit  302  in the first example embodiment. The NWDB for integrated layer  1302  stores network information of an integrated layer created by integrating network information on a network for OpenFlow with flow information on a network for transport as a virtual link. 
         [0056]    A path control application  2000  is an application for referring to and updating the NWDB for integrated layer  1302 . Note that the path control application  2000  may be an application program running on the control server  100 , or may be an application program running on a terminal or the like capable of accessing to the NWDB for integrated layer  1302 . The path control application  2000  also functions as means of externally accepting flow storing with use of a virtual link on an integrated layer by being provided with data in the NWDB for integrated layer  1302 . Of course, the path control application  2000  may be added with other network management functions. 
         [0057]      FIG. 9  is an example of boundary information stored by the layerizer  1200  according to the present example embodiment. In the example of  FIG. 9 , boundary information is constituted of network IDs (NetIDs) each indicating a NWDB for transport or a NWDB for OpenFlow and pairs of IDs of nodes and ports included in the NWDB for transport or the NWDB for OpenFlow. When the information is stored, ports of OpenFlow switches on topology stored in the NWDB for integrated layer  1302 , included in the information, are deleted, as described at S 101  in  FIG. 3 . For example, when the boundary information in  FIG. 9  is stored, Port  10  of the OpenFlow switch  1502  and Port  11  of the OpenFlow switch  1503  in  FIG. 8  are deleted. 
         [0058]      FIG. 10  indicates virtual ports and label information (an example of attribute information) of virtual links stored in ports of a NWDB for OpenFlow. The information is constructed with the boundary information by the layerizer  1200  when a flow is stored in a NWDB for transport. In the example of  FIG. 10 , Port  10  of Node  1  (the OpenFlow switch  1502  in  FIG. 8 ) relates to Virtual Port # 2  (virtual port ID=Vport2), and a value  10  is set as a Virtual Local Area Network (VLAN). 
         [0059]    By using the information as a label value in a matching condition and a packet rewrite action, the driver for OpenFlow  1401  generates a transfer rule to be set in the OpenFlow switches  1502  and  1503 . For example, the driver for OpenFlow  1401  creates such a transfer rule that assigns VLAN ID=10 to a packet to be output from Port  10  of Node  1  (the OpenFlow switch  1502  in  FIG. 8 ) to Virtual Port # 2  (virtual port ID=Vport2). In addition, according to  FIG. 10 , an identical port of an identical switch having a different destination virtual port may be assigned with a different label. For example, the driver for OpenFlow  1401  creates such a transfer rule that assigns Multi Protocol Label Switching (MPLS) label=100 to a packet to be output from Port  10  of Node  1  (the OpenFlow switch  1502  in  FIG. 8 ) to Virtual Port # 4  (virtual port ID=Vport4). 
         [0060]      FIG. 11  indicates flow information stored in the NWDB for integrated layer  1302  by the path control application  2000  and flow information obtained by decomposing the flow information for use in Node  1  and Node  2  by the layerizer  1200 . For example, as illustrated in  FIG. 11 , assume that flow information is stored in the NWDB for integrated layer  1302  as follows. A packet received from Port  1  of Node  1  (the OpenFlow switch  1502  in  FIG. 8 ) (in other words, a “Match” condition in  FIG. 11 ) is output from Port  5  of Node  2  (the OpenFlow switch  1503  in  FIG. 8 ) via a virtual link (# 10 , for example) (in other words, an “Action” condition in  FIG. 11 ). In the example of  FIG. 11 , the layerizer  1200  decomposes the flow, and creates, for Node  1 , flow information (the OpenFlow switch  1502  in  FIG. 8 ) that causes a packet received from Port  1  (in other words, a “Match” condition of Entry # 1  in the lower column of  FIG. 11 ) to be output from Virtual Port # 2  (a virtual port associated with Port  10  in  FIGS. 8 and 10 ). Similarly, the layerizer  1200  creates, for Node  2 , flow information (the OpenFlow switch  1503  in  FIG. 8 ) that causes a packet received from Virtual Port # 6  (a virtual port associated with Port  11  in  FIGS. 8 and 10 ) (in other words, a “Match” condition of Entry # 2  in the lower column of  FIG. 11 ) to be output from Port  5 . 
         [0061]      FIG. 12  indicates transfer rules set for Node  1  (the OpenFlow switch  1502  in  FIG. 8 ) and Node  2  (the OpenFlow switch  1503  in  FIG. 8 ) by the driver for OpenFlow  1401  based on flow information in  FIG. 11 . For example, an entry of Node  1 ; Table 1 in  FIG. 12  specifies that a packet received from Port  1  is attached with a value “10” in Metadata region, and then jump to (Goto) Table 2. Then, an entry of Node  1 ; Table 2 in  FIG. 12  specifies that a packet with a value “10” set in Metadata region is attached with a VLAN ID=10 and is output from Virtual Port # 10 . In this way, a transfer rule related to flow information for Entry # 1  in the lower column of  FIG. 11  is created. Similarly, an entry of Node  2 ; Table 1 in  FIG. 12  specifies that a packet with a VLAN ID=10 received from Virtual Port # 11  is attached with a value “10” in Metadata region, and then jump to (Goto) Table 2. Then, an entry of Node  2 ; Table 2 in  FIG. 12  specifies that a packet with a value “10” set in Metadata region has a VLAN ID detached and then is output from Port  5 . 
         [0062]    Note that the example of  FIG. 12  illustrates a transfer rule (flow entry) assuming that the Multiple Table function prescribed in OpenFlow version 1.1 or later is available. In this example, an entry in Table 2 may be generated at a point of time when label information of virtual links and virtual ports are stored in the ports of the NWDB for OpenFlow  1301 , for example. In addition, when the Multiple Table function is unavailable, the similar processing may be achieved by a plurality of actions with respect to a single flow. 
         [0063]    In the above, each of the example embodiments of the present invention has been described. However, the present invention is not limited to the above-described example embodiments, but can be further modified, substituted, and adjusted within a scope not departing from the basic technical concept of the present invention. For example, the network configuration, the configuration of elements, the table configuration, and the like illustrated in each of the drawings are examples for aiding the understanding of the present invention, and are not limited to the configurations illustrated in the drawings. 
         [0064]    Finally, preferred modes of the present invention are summarized. 
       [First Mode] 
       [0065]    (See the network control system according to the first viewpoint) 
       [Second Mode] 
       [0066]    The network control system according to the first mode, wherein 
         [0067]    the layer integration unit 
         [0068]    confirms, upon storing of information on a flow representing point-to-point communication of the lower layer in the lower layer information storage unit, whether or not an endpoint of the flow is included in boundary information including a set of ports being at a boundary between network topology stored in the lower layer information storage unit and network topology stored in the upper layer information storage unit, designated in advance, 
         [0069]    generates, when an endpoint of the flow is included in the boundary information, a virtual link related to the flow and virtual ports for the virtual link, and stores the virtual link and the virtual ports in integrated layer network information stored in the integrated layer information storage unit, and 
         [0070]    further, assigns the label information as attribute information of ports of the upper layer to a corresponding entry in the upper layer information storage unit. 
       [Third Mode] 
       [0071]    The network control system according to the second mode, wherein 
         [0072]    a plurality of sets of ports between the lower layer and an upper layer existing across the lower layer can be designated as the boundary information, 
         [0073]    further, when a flow is stored in the integrated layer information storage unit with use of the virtual link, the layer integration unit decomposes the flow for an upper layer based on the boundary information, and notifies the upper layer control information conversion unit of occurrence of the flow, and 
         [0074]    the upper layer control information conversion unit receiving the notification updates settings and statuses of the upper layer data transfer units using the assigned label information to transfer the decomposed flow, and updates network information in the upper layer information storage unit. 
       [Fourth Mode] 
       [0075]    The network control system according to any one of the first to third modes, wherein 
         [0076]    the upper layer data transfer units are configured by centralized control-type network switches, and 
         [0077]    the lower layer data transfer unit is configured by a second switch intervening between the centralized control-type network switches. 
       [Fifth Mode] 
       [0078]    The network control system according to any one of the first to fourth modes, wherein 
         [0079]    storing of a flow with use of the virtual link is externally accepted by being provided with information stored in the integrated layer information storage unit. 
       [Sixth Mode] 
       [0080]    (See the control device according to the second viewpoint) 
       [Seventh Mode] 
       [0081]    (See the network information management method according to the third viewpoint) 
       [Eighth Mode] 
       [0082]    (See the program according to the fourth viewpoint) 
         [0083]    Note that the sixth to eighth modes can be developed into the second to fifth modes in the same manner as the first mode. 
         [0084]    Note that the disclosure of each of PTLs listed above is incorporated herein by reference. The example embodiments or examples can be changed and adjusted within the scope of the entire disclosure (including the claims) of the present invention, and further, based on the basic technical concept of the present invention. In addition, various disclosed elements (including the elements in each of the claims, the elements in each of the example embodiments or the examples, the elements in each of the drawings, and the like) can be combined or selected in various ways within the scope of the disclosure of the present invention. In other words, it goes without saying that the present invention includes various modifications and corrections that can be made by a person skilled in the art in accordance with the entire disclosure including the claims and the technical concept. In particular, with regard to ranges of numerical values described herein, arbitrary numerical values or sub-ranges included within the ranges should be interpreted as being specifically described even when not otherwise described. 
       INDUSTRIAL APPLICABILITY 
       [0085]    The present invention is also applicable to uses such as development of a network control algorithm independent from various multistage network configurations. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           100  Control server 
           100 A Computer 
           200  Layer integration unit 
           300  Lower layer information storage unit 
           301  Upper layer information storage unit 
           302  Integrated layer information storage unit 
           400  Lower layer control information conversion unit 
           401  Upper layer control information conversion unit 
           500  Lower layer data transfer unit 
           501 ,  502  Upper layer data transfer unit 
           1200  Layerizer 
           1300  NWDB for transport 
           1301  NWDB for OpenFlow 
           1302  NWDB for integrated layer 
           1400  Driver for transport 
           1401  Driver for OpenFlow 
           1500 ,  1501  Transport (TP) switch 
           1502 ,  1503  OpenFlow switch 
           2000  Path control application