JP5210403B2 - Route determination method and route determination device - Google Patents

Description

  The present invention relates to a route determination method and a route determination device for determining the shortest route between two nodes in a communication network composed of a plurality of nodes.

  In a communication network composed of a plurality of nodes, there are a plurality of communication paths from a start point node which is one of the plurality of nodes to an end point node which is a node other than the start point node among the plurality of nodes. Therefore, it is necessary to determine the shortest route that is the most efficient communication route among the plurality of communication routes.

  Therefore, a weight value called a cost value is set for a link connecting each of a plurality of nodes. In general, by calculating the cost value of each of the plurality of communication paths from the start node to the end node, the communication path having the minimum cost value is determined as the shortest path.

  For example, Non-Patent Document 1 discloses a Dijkstra method that is one of the algorithms for determining the shortest path by the calculation as described above.

  FIG. 9 is a flowchart for explaining the operation of determining the shortest path using the Dijkstra method.

  First, it is determined whether or not there is a node that is not selected as a starting point node among a plurality of nodes constituting the communication network (step S101).

  As a result of the determination in step S101, if there is no node not selected as the start point node, the process ends.

  On the other hand, if the result of determination in step S101 is that there is a node not selected as the start point node, one of the nodes not selected as the start point node is selected as the start point node (step S102). Note that the node selected as the start point node is recognized as the end point node of the determined shortest path.

  Next, it is determined whether there is a node that is adjacent to the end point node of the determined shortest path and whose shortest path from the start point node has not been determined (step S103). The “node adjacent to the end point node” is a node directly connected to the end point node by a link, and no other node exists between the end point node and the node. The same applies to the following description.

  As a result of the determination in step S103, if there is a node adjacent to the end point node of the determined shortest path and the shortest path from the start point node is not determined, the communication path from the start point node to that node is the shortest path candidate. Is done.

  Then, a calculation for calculating the cost value of the shortest path candidate is performed, and the shortest path candidate that minimizes the calculated cost value is determined as the shortest path (step S104). And it changes to operation | movement of step S103.

  On the other hand, if the result of determination in step S103 is that there is no node adjacent to the end point node of the determined shortest path and the shortest path from the start point node is not yet determined, the process proceeds to step S101.

  FIG. 10 is a diagram for explaining a specific example of the operation for determining the shortest path according to the flowchart shown in FIG. 9, (a) shows an example of a communication network, and (b) shows the shortest path is determined. It is a figure which shows an example of a transition which goes. In FIG. 10A, nodes a to g are represented by black circles. Further, hereinafter, the communication path is expressed using <> such as <node a → node b>.

  First, in accordance with the operation of step S101 described above, it is determined whether there is a node that is not selected as the start point node among the nodes a to g configuring the communication network illustrated in FIG. Here, it is assumed that the nodes a to g are not selected as the start point nodes.

  Therefore, one of the nodes a to g is selected as the start node in accordance with the operation of step S102 described above. Here, it is assumed that the node a is selected as the start point node. Thereby, the node a is recognized as the end point node of the determined shortest path.

  Next, according to the operation of step S103 described above, it is determined whether or not there is a node adjacent to the end point node of the determined shortest path and the shortest path from the start point node is undetermined. Here, the terminal node of the determined shortest path is node a. The starting point node is node a. Nodes adjacent to node a in the communication network shown in FIG. 10A are node b and node e. Here, there is no node for which the shortest path from the node a is determined. Accordingly, two of <node a → node b> and <node a → node e> are shortest path candidates.

  Next, a calculation for calculating the cost values of <node a → node b> and <node a → node e> is performed. Here, it is assumed that the cost value of <node a → node b> is smaller than the cost value of <node a → node e>. For this reason, <node a → node b> is determined as the shortest path from node a to node b in accordance with the operation of step S104 described above. The shortest path determined so far is shown in the upper part of FIG.

  Next, the process proceeds to the operation of step S103 described above, and it is determined whether there is a node that is adjacent to the end point node of the determined shortest path and whose shortest path from the start point node has not been determined. Here, the terminal nodes of the determined shortest path are the node a and the node b. The starting point node is node a. In the communication network shown in FIG. 10A, nodes adjacent to node a are node b and node e, and nodes adjacent to node b are node c and node g. Here, <node a → node b> has been determined as the shortest path. Accordingly, the three communication paths of <node a → node b → node c>, <node a → node b → node g>, and <node a → node e> are the shortest path candidates.

  Next, calculation is performed to calculate cost values of <node a → node b → node c>, <node a → node b → node g>, and <node a → node e>. Here, it is assumed that the cost value of <node a → node b → node c> is smaller than the cost value of <node a → node b → node g> and <node a → node e>. For this reason, <node a → node b → node c> is determined as the shortest path from node a to node c in accordance with the operation of step S104 described above. The shortest path determined so far is shown in the middle of FIG.

  Thereafter, by repeating the same operation, it is assumed that <node a → node b → node c → node d> is determined as the shortest path from node a to node d in accordance with the operation of step S104 described above. The shortest path determined so far is shown in the lower part of FIG.

  In this way, one of the plurality of nodes constituting the communication network is selected as the start point node, and the shortest path from the node selected as the start point node is sequentially determined. After all the shortest paths from the start node are determined, one of the nodes not selected as the start node is selected as the start node, and the shortest path from the node selected as the start node is sequentially determined. . That is, when the Dijkstra method is used, the shortest path is sequentially determined for each row of the table as shown in FIG.

Dijkstra, EW (1959). "A note on two problems in connexion with graphs" .Numerische Mathematik 1: 269-271 (http://www-m3.ma.tum.de/twiki/pub/MN0506/WebHome/dijkstra .pdf.)

  An algorithm such as the Dijkstra method described above is an algorithm for determining the shortest path from one node to another node. Therefore, the cost value for determining the shortest path is calculated for each of a plurality of nodes.

  In this case, the cost value is calculated multiple times for the same communication path. That is, there is a problem that the time until the shortest path is determined becomes longer than necessary by performing unnecessary calculations.

  It is an object of the present invention to provide a route determination method and a route determination device that can avoid an unnecessarily long time until determining the shortest route.

In order to achieve the above object, a route determination method of the present invention is a route for determining a shortest route from each of a plurality of nodes constituting a communication network to an end point node that is a node other than the node among the plurality of nodes. A decision method,
A selection process for selecting, as a start point node, one of the plurality of nodes where there is an undetermined end point node for which the shortest path from the node has not been determined;
Processing for determining the shortest path from the start point node to the undetermined end point node;
Determining a communication path from a node other than the start point node on the determined shortest path to the end point node of the shortest path through the shortest path as a shortest path from the node to the end point node; Yes, and
In the selection process, a node to be selected as the start point node among the plurality of nodes is determined according to the number of the undetermined end point nodes .

  In order to achieve the above object, the route determination device of the present invention determines the shortest route from each of a plurality of nodes constituting a communication network to an end node that is a node other than the node among the plurality of nodes. The route determination device performs processing in the above route determination method.

  Since the present invention is configured as described above, a part of the shortest path from the node selected as the start node after the second is determined as the shortest path from the node previously selected as the start node. It will be decided as well.

  Therefore, the calculation of the cost value is not performed a plurality of times for the same communication path, and it can be avoided that the time until the shortest path is determined becomes longer than necessary.

It is a figure which shows an example of a communication network. It is a block diagram which shows the structure of one Embodiment of the route determination apparatus of this invention. It is a figure which shows an example of the shortest path | route determination table with which the memory | storage part shown in FIG. 2 is provided. FIG. 4 is a flowchart for explaining an operation in which the route determination device shown in FIGS. 2 and 3 determines the shortest route. FIG. 4 is a diagram for explaining a specific example of an operation in which the route determination device shown in FIG. 2 and FIG. 3 determines the shortest route, and (a) is an example of a communication network indicated by topology information stored in a topology information section. FIG. 8B is a diagram illustrating an example of a state transition of the shortest path determination table. FIG. 4 is a diagram for explaining another specific example of the operation of determining the shortest path by the path determination device shown in FIG. 2 and FIG. 3, (a) of the communication network indicated by the topology information stored in the topology information section; The figure which shows an example, (b) is a figure which shows an example of a transition of the state of the shortest path determination table. It is a figure for demonstrating an example of operation | movement at the time of the selection part shown in FIG. 2 selecting a starting point node. It is a figure for demonstrating the other example of operation | movement when the selection part shown in FIG. 2 selects a starting point node, (a) shows an example of the communication network which the topology information memorize | stored in the topology information part shows. FIG. 4B is a diagram showing metric values for a plurality of nodes. It is a flowchart for demonstrating the operation | movement which determines the shortest path | route using the Dijkstra method. It is a figure for demonstrating the specific example of the operation | movement which determines the shortest path | route according to the flowchart shown in FIG. 9, (a) is a figure which shows an example of a communication network, (b) is the transition of the shortest path being determined. It is a figure which shows an example.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the present invention, the shortest path is determined by using a part of the shortest path between two nodes as a shortest path between two nodes on the shortest path.

  FIG. 1 is a diagram illustrating an example of a communication network. In FIG. 1, the nodes a to f are represented by black circles.

  Here, in the communication network shown in FIG. 1, if the shortest path from node a to node d is <node a → node b → node e → node c → node d>, the shortest path from node b to node c. The path proves that it is <node b → node e → node c> which is a part of <node a → node b → node e → node c → node d>.

First, the following (1) and (2) are assumed.
(1) The shortest path from node a to node d is <node a → node b → node e → node c → node d> (2) The shortest path from node b to node c is <node b → node f If node (2) is correct, the shortest path from node a to node d is <node a → node b → node f → node c → node d, and the above (1) ) And (2) contradict each other. Therefore, if the shortest path from node a to node d is <node a → node b → node e → node c → node d>, the shortest path from node b to node c is <node a → node b → node <node b → node e → node c> which is a part of e → node c → node d>.

  Thus, a part of the shortest path between two nodes becomes the shortest path between two nodes on the shortest path. In the present invention, when the shortest route between two nodes is determined, a communication route from a node other than the starting point node on the shortest route to the end node of the shortest route through the shortest route is also defined as the shortest route. decide.

  FIG. 2 is a block diagram showing the configuration of an embodiment of the route determination device of the present invention.

  The path determination device 10 illustrated in FIG. 2 includes a topology information unit 11, a storage unit 12, a selection unit 13, and a determination unit 14.

  The topology information unit 11 stores topology information indicating a communication network. Note that the topology information includes a plurality of nodes constituting the communication network and connection states of the plurality of nodes.

  The storage unit 12 uses each of a plurality of nodes constituting the communication network indicated by the topology information stored in the topology information unit 11 as a start point node, and indicates the shortest path indicating whether the shortest path from the start point node to the end point node has been determined. A routing table is provided.

  FIG. 3 is a diagram illustrating an example of the shortest path determination table provided in the storage unit 12 illustrated in FIG.

  As shown in FIG. 3, the shortest path determination table has a column direction as a start point node and a row direction as an end point node. The example shown in FIG. 3 shows a state in which all of the shortest paths when the node a is the start node are determined.

  Referring to FIG. 2 again, the selection unit 13 refers to the shortest path determination table stored in the storage unit 12. Then, the selection unit 13 is a node in which there is an undetermined end point node that is an end point node in which the shortest path is not determined when the node is the start point node among a plurality of nodes constituting the communication network indicated by the topology information Determine if there is any. As a result of the determination, when there is a node having an undetermined end point node, the selection unit 13 selects one of the nodes having an undetermined end point node as a start point node. For example, when the shortest path determination table is in the state shown in FIG. 3, the selection unit 13 selects one of the nodes b to d as the start node. Then, the selection unit 13 outputs selected node information indicating the node selected as the start point node to the determination unit 14.

  The determination unit 14 acquires the topology information stored in the topology information unit 11. Further, the determination unit 14 receives the selected node information output from the selection unit 13. Then, the determination unit 14 uses the node indicated by the received selected node information as a start point node, refers to the acquired topology information, and determines the shortest path from the start point node to the undetermined end point node. Specifically, the determination unit 14 determines the shortest path by calculating a cost value using, for example, the Dijkstra method described above. Further, the determination unit 14 determines a route from a node other than the start node on the determined shortest route to the end node of the shortest route via the shortest route as the shortest route from the node to the end node. . Then, the determination unit 14 updates the shortest path determination table stored in the storage unit 12 based on the determined shortest path.

  Hereinafter, an operation in which the route determination device configured as described above determines the shortest route will be described.

  FIG. 4 is a flowchart for explaining an operation in which the route determination device 10 shown in FIGS. 2 and 3 determines the shortest route.

  First, the selection unit 13 refers to the shortest path determination table stored in the storage unit 12.

  Then, the selection unit 13 determines whether there is a node having an undetermined end point node among a plurality of nodes constituting the communication network indicated by the topology information (step S1).

  If the result of determination in step S <b> 1 is that there is no node with an undetermined end point node, the process ends.

  On the other hand, if the result of determination in step S1 is that there is a node with an undetermined end point node, the selection unit 13 selects one of the nodes with an undetermined end point node as the start point node (step S2). Note that the node selected as the start point node is recognized by the determination unit 14 as the end point node of the determined shortest path.

  Then, the selection unit 13 outputs selected node information indicating the node selected as the start point node to the determination unit 14.

  The determination unit 14 that has received the selection node information output from the selection unit 13 refers to the topology information, is adjacent to the end point node of the determined shortest path, and from the start node indicated by the received selection node information. It is determined whether there is a node for which the shortest path has not been determined (step S3).

  If the result of determination in step S3 is that there is a node that is adjacent to the end node of the determined shortest path and that has not yet been determined from the start node indicated by the received selected node information, the determining unit 14 The communication path from the node to the node is the shortest path candidate.

  Then, the determination unit 14 performs a calculation for calculating the cost value of the shortest path candidate, and determines the shortest path candidate having the minimum calculated cost value as the shortest path (step S4).

  Next, the determination unit 14 determines a communication path from a node other than the start point node on the shortest path determined in step S4 to the end point node of the shortest path from the node to the end point node. The shortest route is determined (step S5).

  And the determination part 14 updates the shortest path | route determination table memorize | stored in the memory | storage part 12 based on the shortest path | route determined in step S4 and step S5 (step S6), and changes to operation | movement of step S3.

  On the other hand, if the result of determination in step S3 is that there is no node that is adjacent to the end node of the determined shortest path and whose shortest path from the start node indicated by the received selected node information is not yet determined, Transition to operation.

  FIG. 5 is a diagram for explaining a specific example of the operation in which the route determination device 10 shown in FIGS. 2 and 3 determines the shortest route. FIG. 5A shows the topology information stored in the topology information unit 11. The figure which shows an example of the communication network to show, (b) is a figure which shows an example of transition of the state of the shortest path determination table. In FIG. 5A, nodes a to g are represented by black circles.

  First, according to the operation of step S1 described above, the selection unit 13 determines whether there is a node having an undetermined end point node among the nodes a to g configuring the communication network illustrated in FIG. Here, it is assumed that there is an undetermined end point node when the nodes a to g are set as start point nodes.

  Therefore, according to the operation in step S2 described above, the selection unit 13 selects one of the nodes a to g as a start point node. Here, the selection part 13 shall select the node a as a starting point node. As a result, the node a is recognized by the determination unit 14 as the end node of the determined shortest path.

  Next, according to the operation of step S3 described above, the determination unit 14 determines whether there is a node that is adjacent to the end point node of the determined shortest path and whose shortest path from the start point node has not yet been determined. Here, the terminal node of the determined shortest path is node a. The starting point node is node a. Nodes adjacent to the node a in the communication network shown in FIG. 5A are the node b and the node e. Here, it is assumed that there is no node for which the shortest path from the node a is determined. Accordingly, two of <node a → node b> and <node a → node e> are shortest path candidates.

  Next, the determination unit 14 performs a calculation for calculating cost values of <node a → node b> and <node a → node e>. Here, it is assumed that the cost value of <node a → node b> is smaller than the cost value of <node a → node e>. Therefore, the determination unit 14 determines <node a → node b> as the shortest path from node a to node b in accordance with the operation of step S4 described above.

  Next, the determination unit 14 operates according to step S5 described above. Here, the node other than the start point node on the shortest path determined in step S4 and the end point node of the shortest path are both nodes b. . Therefore, the operation in step S5 described above is not executed here.

  And the determination part 14 updates the shortest path | route determination table based on the determined shortest path | route according to operation | movement of step S6 mentioned above. The updated shortest path determination table is shown in the upper part of FIG.

  Next, the process proceeds to the operation of step S3 described above, and the determination unit 14 determines whether there is a node adjacent to the end point node of the determined shortest path and having the undecided shortest path from the start point node. Here, the terminal nodes of the determined shortest path are the node a and the node b. The starting point node is node a. In the communication network shown in FIG. 5A, nodes adjacent to node a are node b and node e, and nodes adjacent to node b are node c and node g. Here, <node a → node b> has been determined as the shortest path. Accordingly, the three communication paths of <node a → node b → node c>, <node a → node b → node g>, and <node a → node e> are the shortest path candidates.

  Next, the determination unit 14 performs calculation to calculate cost values of <node a → node b → node c>, <node a → node b → node g>, and <node a → node e>. Here, it is assumed that the cost value of <node a → node b → node c> is smaller than the cost value of <node a → node b → node g> and <node a → node e>. Therefore, the determination unit 14 determines <node a → node b → node c> as the shortest path from node a to node c in accordance with the operation of step S4 described above.

  Further, the determination unit 14 determines a communication path from the node other than the start point node on the shortest path determined in step S4 to the end point node of the shortest path through the shortest path in accordance with the operation of step S5 described above. It is determined as the shortest path from a node to its end node. Here, the shortest path determined in step S4 described above is <node a → node b → node c>. Therefore, the node other than the start point node (node a) is the node b, and the end point node is the node c. Therefore, the determination unit 14 determines <node b → node c> as the shortest path from node b to node c.

  And the determination part 14 updates the shortest path | route determination table based on the determined shortest path | route according to operation | movement of step S6 mentioned above. The shortest path determination table after the update is shown in the middle part of FIG.

  Thereafter, by repeating the same operation, the determination unit 14 determines <node a → node b → node c → node d> as the shortest path from the node a to the node d according to the operation of step S4 described above. To do.

  In this case, the nodes other than the start point node (node a) on the determined shortest path are the node b and the node c, and the end point node is the node d. Therefore, the determination unit 14 determines <node b → node c → node d> as the shortest path from node b to node d according to the operation of step S5 described above, and <node c → node d> from node c. It is determined as the shortest route to node d.

  And the determination part 14 updates the shortest path | route determination table based on the determined shortest path | route according to operation | movement of step S6 mentioned above. The updated shortest path determination table is shown in the lower part of FIG.

  As described above, in the present embodiment, the route determination device 10 uses, as a start point node, one of the plurality of nodes constituting the communication network that has an undetermined end point node for which the shortest route from the node is not determined. select. Then, the route determination device 10 determines the shortest route from the start point node to the undetermined end point node.

  Further, the route determination device 10 determines a communication route from a node other than the start point node on the determined shortest route to the end point node of the shortest route via the shortest route, and the shortest route from the node to the end point node. Determine as.

  As a result, a part of the shortest path from the node selected as the start point node after the second is determined together with the shortest path from the node previously selected as the start point node.

  Therefore, the cost value is not calculated multiple times for the same route, and it can be avoided that the time until the shortest route is determined becomes longer than necessary.

  Here, according to the above-described method, there is a sufficient effect that it is possible to avoid that the time until the shortest path is determined becomes longer than necessary depending on the order of selecting each of the plurality of nodes as the start node. It may not be.

  FIG. 6 is a diagram for explaining another specific example of the operation in which the route determination device 10 shown in FIGS. 2 and 3 determines the shortest route. FIG. 6A is a topology stored in the topology information unit 11. The figure which shows an example of the communication network which information shows, (b) is a figure which shows an example of transition of the state of the shortest path determination table. In FIG. 6A, the nodes a to g and the nodes x to z are represented by black circles.

  Here, it is assumed that there is an undetermined end point node when the nodes a to g and the nodes x to z are set as start point nodes. Consider the case where node x is first selected as the starting point node.

  In this case, if <node x → node b → node c> is determined as the shortest path from node x to node c, along with this, <node b → node c> is the shortest path from node b to node c. It will be determined as a route. If <node x → node b → node c → node d> is determined as the shortest path from node x to node d, along with this, <node b → node c → node d> is changed from node b. It is determined as the shortest route to the node d. Also, <node c → node d> is determined as the shortest path from node c to node d. The shortest path determination table updated based on the shortest path determined so far is shown in the upper part of FIG.

  Thereafter, node a is selected as the start node, and <node a → node b → node c> is determined as the shortest path from node a to node c. Accordingly, <node b → node c> should be determined as the shortest path from node b to node c. However, the shortest path from the node b to the node c has already been determined when the shortest path is determined with the node x as the start node, as shown in the upper part of FIG. 6B.

  Similarly, assume that <node a → node b → node c → node d> is determined as the shortest path from node a to node d. Accordingly, <node b → node c → node d> is determined as the shortest path from node b to node d, and <node c → node d> is determined as the shortest path from node c to node d. It should be. However, the shortest path from the node b to the node d and the shortest path from the node c to the node d are already already determined when the shortest path is determined with the node x as the starting point node, as shown in the upper part of FIG. It has been decided.

  Thus, depending on the order in which each of the plurality of nodes is selected as the start point node, there may be a case where it is not possible to sufficiently obtain an effect that it is possible to avoid an unnecessarily long time until the shortest path is determined. obtain.

  Therefore, it is necessary to determine the order in which each of the plurality of nodes is selected as the start point node so that the total calculation amount is as small as possible.

  This order may be performed based on information that can be known at the time of selecting the start point node, such as the configuration of the communication network, the calculation result performed immediately before, or information calculated based on the information.

  FIG. 7 is a diagram for explaining an example of an operation when the selection unit 13 shown in FIG. 2 selects a start point node, and shows a shortest path determination table.

  The shortest path determination table shown in FIG. 7 is a state in which a part of the shortest path when the node b and the node c are set as the start nodes is already determined as a result of selecting the node a as the start node and determining the shortest path. Is shown.

  From this state, when determining the node to be selected as the next start point node, the selection unit 13 sets the node having the largest number of undecided end point nodes as the start point node among the nodes b to d where the undecided end point nodes exist. select. In the example shown in FIG. 7, the number of undetermined end nodes is one for node b, two for node c, and three for node d. Therefore, the selection unit 13 selects the node d as the start point node.

  A large number of undetermined end-point nodes for a node means that the number of communication paths that pass through the node among the communication paths for which the cost value has been calculated in order to determine the shortest path is small. . Therefore, if a node with a larger number of undetermined end nodes is preferentially selected as the start node, the calculation performed to determine the shortest path from that node will determine the shortest path from the other nodes The probability of being already done is low. Therefore, if a node having a larger number of undetermined end nodes is preferentially selected as the start node, the shortest path from that node can be used as the shortest path from more other nodes.

  As another method for determining the order of selecting each of the plurality of nodes as the start point node, there is a method of using a metric value of a link connecting each of the plurality of nodes. The metric value is a parameter that represents a virtual distance between two nodes.

  In this case, the selection unit 13 selects, as a start point node, a node having the largest average value of the metric values of the links connected to the node among the nodes having the undetermined end point node.

  When determining the shortest path, the smaller the metric value of a link, the shorter the distance of the communication path through the link is recognized, and the average value of the metric values of the links connected to a node is If it is large, the number of shortest paths passing through the node is small. Therefore, if a node with a larger average metric value of connected links is preferentially selected as the start node, the calculation performed to determine the shortest path from that node will be calculated from other nodes. The probability of having already been performed when determining the shortest path is reduced. In other words, if a node with a larger average metric value of connected links is preferentially selected as the start node, the shortest route from that node can be used as the shortest route from many other nodes. Can do.

  FIG. 8 is a diagram for explaining another example of the operation when the selection unit 13 shown in FIG. 2 selects the start node, and (a) shows the topology information stored in the topology information unit 11. The figure which shows an example of a communication network, (b) is a figure which shows the metric value for every some node.

  In FIG. 8A, each of the nodes A to F is represented by a square, and the link is represented by a straight line. A numerical value in the vicinity of each link indicates a metric value of each link. Here, it is assumed that the metric value is the same regardless of the uplink / downlink direction of each link.

  In the case of the example illustrated in FIG. 8, the selection unit 13 calculates the average value of the metric values of the links connected to the nodes A to F for each of the nodes A to F. This is shown in FIG. 8 (b).

  Then, the selection unit 13 selects nodes as the start point node in order from the node with the larger average metric value. Therefore, in the example shown in FIG. 8, the node D having the largest average metric value is selected first as the start point node. Then, the node F selected next to the node D is the node F having the average metric value next to the node D.

  As described above, the route determination device 10 determines the node to be selected as the start point node in the order according to the number of undecided end nodes or the order according to the metric value of the link to which each of the plurality of nodes is connected. To do. Thereby, it is possible to sufficiently obtain an effect that it is possible to avoid that the time until the shortest path is determined becomes longer than necessary.

DESCRIPTION OF SYMBOLS 10 Route determination apparatus 11 Topology information part 12 Memory | storage part 13 Selection part 14 Determination part

Claims (3)

A route determination method for determining a shortest route from each of a plurality of nodes constituting a communication network to an end point node that is a node other than the node among the plurality of nodes,
A selection process for selecting, as a start point node, one of the plurality of nodes where there is an undetermined end point node for which the shortest path from the node has not been determined;
Processing for determining the shortest path from the start point node to the undetermined end point node;
Determining a communication path from a node other than the start point node on the determined shortest path to the end point node of the shortest path through the shortest path as a shortest path from the node to the end point node; Have
In pre-Symbol selection process, the nodes selected as the start node of the plurality of nodes, path determination method for determining in accordance with the number of the undetermined end node. A route determination method for determining a shortest route from each of a plurality of nodes constituting a communication network to an end point node that is a node other than the node among the plurality of nodes,
A selection process for selecting, as a start point node, one of the plurality of nodes where there is an undetermined end point node for which the shortest path from the node has not been determined;
Processing for determining the shortest path from the start point node to the undetermined end point node;
Determining a communication path from a node other than the start point node on the determined shortest path to the end point node of the shortest path through the shortest path as a shortest path from the node to the end point node; Have
Each of the previous SL plurality of nodes, connected by links,
In the selection process, a path determination method for determining a node to be selected as the start node among the plurality of nodes according to a metric value of a link to which each of the plurality of nodes is connected. A path determination device that determines a shortest path from each of a plurality of nodes constituting a communication network to an end point node that is a node other than the node among the plurality of nodes,
Routing device for performing the process in the path determination method according to claim 1 or 2.

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