JP4180542B2 - Shortest path selection method, node and multilayer network - Google Patents

Description

The present invention relates to GMPLS (Generalized Multi Protocol).
The present invention relates to a multilayer network control technology represented by (Label Switching).

  A multi-layer network consisting of a plurality of networks such as a fiber network, a wavelength network, a TDM network, and a packet network is hierarchized, and a wavelength path is selected by using a network topology composed of fiber links. The wavelength path is regarded as a link when viewed from the upper layer packet layer or the like, and the path selection of the packet path is performed using a network topology constituted by the wavelength links.

In such a hierarchical multi-layer network, when calculating a route, there is a problem of which route is set via a network in which layer. Up to now, when setting the upper layer path, whether to use the existing lower layer link as much as possible, or whether to set the upper layer path using this after setting a new lower layer path A route selection algorithm focusing on the point and a network control technique using the algorithm have been proposed (for example, see Non-Patent Document 1).
K.Sato, N.Yamanaka, Y.Takigawa, M.Koga, S.Okamoto, K.Shiomoto, E.Oki, andW.Imajuku, “GMPLS-based photonic multilayer router (Hikari router) architecture: anoverview of traffic engineering and signaling technology ”, IEEECommun.Mag., Vol.40, No.3, pp.96-101, Mar.2002

  When selecting a path for a path in the network, the path is selected for the purpose of effectively utilizing the resources of the multilayer network. In the background art, route selection is performed according to a predetermined policy. However, depending on the network configuration and node configuration, the policy direction is unsuitable, and in some cases, network resources may not be effectively used.

  The present invention has been made in view of such a background, and provides a shortest path selection method, a node, and a multilayer network that can effectively use network resources regardless of the network configuration or the node configuration. For the purpose.

A first aspect of the present invention is a multi-layer network configured by layering a plurality of networks of different layers, and a layer through which a path from a source node to a destination node passes and the shortest path of the node the destination node walking is the shortest path selecting method for selecting a route selection device provided separately from the nodes.

  Here, the feature of the present invention is that, when creating a virtual graph in which the route is virtually set based on the topology in each layer network, among the line segments constituting the virtual graph of each layer. When the line segment connecting the same points exists only in one layer, the line segment of this layer is used, and when it exists in a plurality of layers, the one with the lowest cost is selected from these ( Claim 1).

  Thus, prior to route selection, a virtual graph in which the route is virtually set in the network of each layer based on the respective topology is created, and by selecting the route, the cost of passing through multiple layers can be reduced. It is possible to select the shortest route that is minimized.

  After multiplying the weight factor for each layer, if there are multiple line segments that connect the same point among the line segments that make up the virtual graph of each layer, select the one with the lowest cost (Claim 2).

  That is, in a multi-layer network, even if the cost is the same, the traffic accommodation possibility may be different for each layer, so it may be difficult to set the cost uniformly. For this reason, when there are multiple segments connecting the same points in multiple layers, the cost is compared between the layers and the one with the lowest cost is selected. It may not be a route. For example, when the minimum cost in a network of a certain layer is “5”, the minimum cost in the network of another layer is “10”, but the route passing through these two layers may be the same distance. . That is, in reality, although the distance does not change regardless of which layer is selected, a traffic allocation imbalance may occur in which the layer with the lower cost is always selected. Alternatively, a rule inversion may occur such that a layer with a higher cost has a higher possibility of accommodating traffic than a layer with a lower cost. By multiplying each layer by a weighting factor, such a cost imbalance can be improved.

  Note that the distance here is not limited to a physical distance, but refers to the possibility of accommodating traffic including various elements such as bandwidth and service quality.

When determining the weighting factor, using the initial weighting factor of each layer, route selection is performed a prescribed number of times, and after calculating the block rate, which is the ratio when the route to the destination node is not found at this time, after changing the values of the weighting factor by a predetermined value, again, the blocking probability calculated by performing routing only a specified number of times, perform the first step you block index and compared to the previously calculated, the first If the block rate increases as a result of executing one step, the initial weighting factor value is changed by a predetermined value in the opposite direction to the first step, and then the route is selected a specified number of times. If the block index is calculated, perform a second step you block index and compared in the case of the value of the initial weighting coefficients, block rate decreased as a result of executing the first step Te, The predetermined value If the block ratio decreases as a result of executing the second step, the value after changing the value in the reverse direction is set as a new weighting factor. A third step is performed to replace the new weighting factor with the original weighting factor, and the first, second and third steps are repeated as long as a decrease in the block rate is observed. (Claim 3).

  Thereby, an effective weighting factor can be set automatically and efficiently in order to select a route with the smallest block rate.

Further, when the block ratio does not decrease as a result of the execution of the first and second steps, the value of the initial weighting factor is changed by a value obtained by halving the predetermined value, and then the specified number of times. performing route selection to calculate the blocking probability only perform the fourth step you block index and compared in the case of the value of the initial weighting coefficients, block index as a result of executing this fourth step If not, after changing the initial weighting factor value by a value halved from the predetermined value in the direction opposite to the fourth step, the path selection is performed a prescribed number of times, and the block rate was calculated, the initial running fifth step you block index and compared in the case of the value of the weighting factor, the fourth If the block index is lowered as a result of executing the steps of the predetermined Halved the value If the block rate is reduced as a result of executing the fifth step after changing the value after changing only by a new weighting factor, after changing the value by halving the predetermined value in the reverse direction And a sixth step of replacing the new weighting factor with the original weighting factor, and performing the fourth, fifth, and sixth steps with a block ratio equal to or less than a threshold value. It can be repeatedly executed until it becomes (Claim 4).

When the block ratio does not decrease as a result of executing the fourth and fifth steps, the predetermined value is further decreased by half and the fourth, fifth and sixth steps are repeatedly executed. (Claim 5). That is, by gradually reducing the change width of the weighting factor, it is possible to finally converge to the optimum weighting factor.

Thus, even when the weighting factor is not determined by the first, second, and third steps, the weighting factor can be determined by the fourth, fifth, and sixth steps.

The second aspect of the present invention is a multi-layer network configured by layering a plurality of networks of different layers, and a layer and a node through which a path from the own node to the destination node or from the source node to the own node passes. It is a node having means for selecting the shortest path.

  Here, a feature of the present invention is that the selecting means includes means for creating a virtual graph in which the route is virtually set based on the topology in each layer network, and the creating means includes Of the line segments that make up the virtual graph of each layer, if the line segment connecting the same points exists only in one layer, use this line segment, and if it exists in multiple layers, Means for selecting the one with the lowest cost (claim 6).

  The means for selecting the one with the lowest cost is obtained by multiplying a weighting factor for each layer, and then, among the line segments constituting the virtual graph of each layer, there are line segments connecting the same points in a plurality of layers. Can be provided with means for selecting the one having the lowest cost from among them (claim 7).

The means for determining the weighting factor is provided, and this means for determining is a ratio when the route selection is performed a prescribed number of times using the initial weighting factor of each layer, and the route to the destination node is not found at this time. after calculating the blocking probability, after changing the value of the weighting factor by a predetermined value, again, the blocking probability calculated by performing routing only a specified number of times, first block index and compared to the previously calculated When the block ratio increases as a result of executing the first step and the means for executing the first step, the value of the initial weighting factor is changed by a predetermined value in the opposite direction to the first step. after the blocking probability calculated by performing only routing specified number of times, and means for performing the second step you block index and compared in the case of the value of the initial weighting coefficients, performs the first step As a result of When the lock rate decreases, the value after changing by the predetermined value is set as a new weighting coefficient. When the block rate decreases as a result of executing the second step, the predetermined value is set in the reverse direction. A means for performing a third step of replacing the new weighting factor with the original weighting factor by setting the value after changing the value as a new weighting factor, and the first, second, and third And means for repeatedly executing the steps as long as the block ratio is reduced (claim 8).

Further, when the block ratio does not decrease as a result of the execution of the first and second steps, the value of the initial weighting factor is changed by a value obtained by halving the predetermined value, and then the specified number of times. only perform routing to calculate the blocking probability, and means for performing a fourth step you block index and compared in the case of the value of the initial weighting coefficients, block as a result of executing this fourth step If the rate does not decrease, change the value of the initial weighting coefficient by a value that halves the predetermined value in the direction opposite to the fourth step, and then perform route selection a specified number of times. the block rate is calculated and means for executing the fifth step you block index and compared in the case of the value of the initial weighting coefficient, if the block index is lowered as a result of executing the fourth step The predetermined If the value after changing the value by half is used as a new weighting factor, and the block ratio decreases as a result of executing the fifth step, the predetermined value is halved in the reverse direction. Means for performing a sixth step of replacing the original weighting factor with a new weighting factor after changing the value by a new weighting factor, and the fourth, fifth, and sixth Means for repeatedly executing the steps until the block ratio is equal to or less than a threshold value (claim 9).

When the block ratio does not decrease as a result of executing the fourth and fifth steps, the predetermined value is further decreased by half and the fourth, fifth, and sixth steps are repeatedly executed. (Claim 10).

  A third aspect of the present invention is a multilayer network comprising the node of the present invention (claim 11).

  It should be noted that each means provided in the node can be provided as a route selection device separately from the node. This route selection device can centrally manage the route selection of each node.

The fourth aspect of the present invention, by installing the information processing apparatus, to the information processing apparatus, a network of a plurality of different layers in layered with composed multi-layer network, from the source node to the destination node It is a program that realizes a function corresponding to a route selection device provided separately from the originating node, the destination node, or the node and having a function of selecting the shortest route of a layer and a node through which a path passes.

  Here, the feature of the present invention is that, as the function to be selected, the function of creating a virtual graph in which the route is virtually set based on the topology of each layer network is realized, and the function of creating As for the line segments constituting the virtual graph of each layer, when the line segment connecting the same points exists only in one layer, the line segment of this layer is used. The present invention is to realize a function of selecting the lowest cost among them (claim 12).

  As a function of selecting the one with the lowest cost, after multiplying each layer by a weighting factor, among the line segments constituting the virtual graph of each layer, there are line segments connecting the same points in a plurality of layers Can realize the function of selecting the one with the lowest cost among these (claim 13).

Further, the function for determining the weighting factor is realized, and as the function for determining, a route selection is performed a prescribed number of times using the initial weighting factor of each layer, and a route to the destination node is not found at this time. after calculating the block which is a ratio, after changing the value of the weighting factor by a predetermined value, again, the blocking probability calculated by performing only routing specified number of times, block index and compared to the previously calculated If the block rate increases as a result of executing the first step and the result of executing the first step, the value of the initial weight coefficient is set to a predetermined value in the opposite direction to the first step. after changing, the blocking probability calculated by performing routing only a specified number of times, a function of executing the second step you block index and compared in the case of the value of the initial weighting factors, the first of Realize the step As a result, when the block rate is reduced, the value after changing by the predetermined value is set as a new weighting factor. When the block rate is reduced as a result of executing the second step, the reverse direction is set. A function of executing a third step of replacing the original weighting factor with a new weighting factor after changing the value by a predetermined value to the first weighting factor, and the first, second, and A function of repeatedly executing the third step as long as the block ratio is reduced can be realized.

Further, when the block ratio does not decrease as a result of the execution of the first and second steps, the value of the initial weighting factor is changed by a value obtained by halving the predetermined value, and then the specified number of times. performing route selection to calculate the blocking probability by a function of executing a fourth step you block index and compared in the case of the value of the initial weighting coefficients, block as a result of executing this fourth step If the rate does not decrease, change the value of the initial weighting coefficient by a value that halves the predetermined value in the direction opposite to the fourth step, and then perform route selection a specified number of times. the block rate is calculated and a function of performing a fifth step you block index and compared in the case of the value of the initial weighting coefficient, if the block index is lowered as a result of executing the fourth step The predetermined If the value after changing the value by half is used as a new weighting factor, and the block ratio decreases as a result of executing the fifth step, the predetermined value is halved in the reverse direction. A function that executes a sixth step of replacing the original weighting factor with a new weighting factor after changing the value by a new weighting factor, and the fourth, fifth, and sixth It is possible to realize a function of repeatedly executing the steps until the block ratio becomes equal to or less than the threshold value (claim 15).

When the block ratio does not decrease as a result of executing the fourth and fifth steps, the predetermined value is further decreased by half and the fourth, fifth, and sixth steps are repeatedly executed. This function can be realized (claim 16).

  Each function realized as a node can be realized as a route selection device separately from the node. This route selection device can centrally manage the route selection of each node.

  A fifth aspect of the present invention is the information processing apparatus-readable recording medium on which the program of the present invention is recorded (claim 17). By recording the program of the present invention on the recording medium of the present invention, the information processing apparatus can install the program of the present invention using this recording medium. Alternatively, the program of the present invention can be directly installed in the information processing apparatus via a network from a server holding the program of the present invention.

  As a result, it is possible to realize a node that can effectively use network resources regardless of the network configuration or the node configuration in a multi-layer network using a general-purpose information processing apparatus.

  According to the present invention, in a multilayer network, network resources can be effectively used regardless of the network configuration or the node configuration.

  The shortest path selection method and node according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of a multilayer network. FIG. 2 is a flowchart showing a virtual graph creation procedure. FIG. 3 is a flowchart showing a weighting factor determination procedure. FIG. 4 is a flowchart showing the weighting factor convergence procedure.

  As shown in FIG. 1, the present embodiment is a multi-layer network formed by layering a plurality of different layer networks, and the layer through which the path from the source node to the destination node passes and the shortest path of the node are This is a shortest route selection method in which the source node, the destination node or the node is selected by a route selection device provided separately.

  In general, it is reasonable for the originating node to send data from now on to select the route, but the destination node may select the route to the originating node, or separate from these nodes. The route selection device provided in the network may perform route selection between a plurality of nodes in a unified manner. Whichever route is selected does not affect the essence of the present invention.

  Here, the feature of this embodiment is that, as shown in FIG. 2, when creating a virtual graph in which the route is virtually set based on the topology in each layer network, the virtual layer of each layer is created. Of the line segments constituting the graph (S1), when a line segment connecting the same point exists only in one layer (S2), the line segment of this layer is used (S4), and the line segment exists in multiple layers (S2), where the one with the lowest cost is selected (S3) (Claim 1).

  In the present embodiment, after multiplying each layer by a weighting factor, among the line segments constituting the virtual graph of each layer, if there are line segments connecting the same points in a plurality of layers, the cost is reduced from these. The smallest one is selected (Claim 2).

As shown in FIG. 3, when determining the weighting factor, the initial weighting factor α of each layer is used (S11), and the route selection is performed a prescribed number of times (S12, S13). After calculating the block rate, which is the ratio when the route is not found (S14), after changing the weight coefficient value α by a minute value + Δ (S15), the route is selected again a predetermined number of times, and the block rate is determined. (S16, S17, S18), and compared with the previously calculated block rate (S19). When the block rate is reduced (S20), the value (α + Δ) after changing only the minute value is newly set. It is set as a weighting coefficient (S27). When the block ratio increases as a result of executing steps S15 to S19 (S20), the initial weighting factor value α is changed by a minute value −Δ in the opposite direction to step S15 (S21), and then specified. The block ratio is calculated by selecting the number of times (S22, S23), compared with the block ratio in the case of the initial weighting factor value α (S24), and when the block ratio is reduced (S25), the reverse direction Then, the value (α−Δ) after the change by a minute value −Δ is set as a new weighting coefficient (S26). Then, the new weighting coefficient (α + Δ) or (α−Δ) is replaced with the original weighting coefficient α (S26, S27) . Steps S11 to S27 are repeated as long as the block rate is reduced (Claim 3). At this time, when the block rate does not decrease as a result of executing steps S15 to S19 and S21 to S24, the process proceeds to the weighting factor convergence procedure shown in FIG. 4 (S28).

In the weighting factor convergence procedure, as shown in FIG. 4, the initial weighting factor value α is changed by a minute value + Δ half the value + Δ / 2 (S31, S32), and then route selection is performed a specified number of times. The block ratio is calculated (S33, S34, S35) and compared with the block ratio in the case of the original weighting factor value α (S36). When the block ratio decreases (S37), a small value + Δ is set. A value (α + (Δ / 2)) after changing by half the value + 2 / Δ is set as a new weighting coefficient (S46) . If the block ratio does not decrease as a result of executing steps S32 to S36 , the original weighting factor value α is changed by a minus value −Δ / 2, which is a small value −Δ in the opposite direction to step S32. (S38), the path ratio is selected a predetermined number of times to calculate the block ratio (S39, S40, S41), and compared with the block ratio in the case of the original weighting factor value α (S42), the block ratio is In the case of a decrease (S43) , the value (α- (Δ / 2)) after changing by a value −Δ / 2, which is a half of the small value −Δ in the reverse direction, is set as a new weighting coefficient (S46). ). Then , the new weighting coefficient (α + (Δ / 2)) or (α− (Δ / 2)) is replaced with the original weighting coefficient α (S46). Steps S32 to S43 and S46 are repeatedly executed until the block rate becomes equal to or smaller than the threshold (S44) (Claim 4).

When the block ratio does not decrease as a result of executing steps S32 to S36 and S38 to S42, the minute values are successively reduced by half (S45), and steps S32 to S46 are repeatedly executed. ).

That is, when the block rate does not decrease in step S43 when steps S38 to S42 are executed, the weighting coefficient α is changed by + Δ / 4 in step S32 as shown in step S45. Furthermore, if the block rate does not decrease in step S37, the weighting coefficient is changed by α−Δ / 4 in step S38. If the block rate still increases, the minute values are further halved successively in the order of ± Δ / 8, ± Δ / 16, ± Δ / 32,.

  FIG. 5 is a block diagram of the node of this embodiment. As shown in FIG. 1, this embodiment is a multi-layer network configured by layering a plurality of different layer networks. As shown in FIG. 5, the layer through which the path from the own node to the destination node passes. And a node including a shortest path selection unit 1 that selects the shortest path of the node.

  Here, a feature of the present embodiment is that the shortest path selection unit 1 includes a virtual graph creation unit 2 that creates a virtual graph in which the path is virtually set based on the topology in each layer network. When the line segment connecting the same point exists in only one layer among the line segments constituting the virtual graph of each layer, the virtual graph creating unit 2 uses the line segments of this layer to If there is a minimum cost selection unit 4, the minimum cost selection unit 4 that selects the one with the minimum cost is provided (Claim 6).

  This minimum cost selection unit 4 multiplies each layer by a weighting factor, and among the line segments constituting the virtual graph of each layer, when there are line segments connecting the same points in a plurality of layers, Means for selecting the one with the lowest cost (Claim 7).

  The weighting calculation unit 5 for determining the weighting coefficient is provided, and the weighting calculation unit 5 includes means for executing steps S11 to S46 based on the topology information and cost information held in the virtual graph creation information storage unit 3 (invention). Item 8, 9, 10).

  As shown in FIG. 1, the multilayer network of the present embodiment includes the node of the present embodiment (claim 11).

  The present embodiment can be implemented as a program that, when installed in a general-purpose information processing apparatus, causes the information processing apparatus to realize functions corresponding to the nodes of the present embodiment (claims 12, 13, 14, 15). 16). The program is recorded on a recording medium and installed in the information processing apparatus (Claim 17), or installed in the information processing apparatus via a communication line, so that the shortest path selection unit 1, virtual Functions corresponding to the graph creation unit 2, the virtual graph creation information storage unit 3, the minimum cost selection unit 4, and the weighting calculation unit 5 can be realized.

  In this embodiment, FIG. 5 is described as a block configuration of a node. However, the same description can be applied to a block configuration of a route selection device provided separately from a node.

  Further, by installing the program of the present embodiment in the information processing apparatus, the information processing apparatus can be made an apparatus having a function corresponding to the node of the present embodiment, and the program of the present embodiment is installed in the information processing apparatus. By installing the information processing apparatus, the information processing apparatus can be an apparatus having a function corresponding to a route selection apparatus provided separately from the node.

  In the following, embodiments of the present invention will be described in more detail.

(First Example)
FIG. 1 shows an example of a multilayer network. In this example, the multilayer network includes a fiber network, a wavelength network, and a packet network. In each layer network, a line or dotted line connecting nodes is a path, and this path is recognized as a link when viewed from an upper layer.

  That is, a straight line that is a path of the fiber layer is recognized as a link when viewed from the wavelength layer, and a curve of the wavelength layer indicates a wavelength path and is regarded as a link when viewed from the packet layer. Multi-layer networks have such a hierarchical network characteristic.

  In such a multi-layer network, when setting a packet path from node C to node E, it is necessary that the nodes be connected by a wavelength path, and the nodes are connected by a wavelength path. It is necessary to be connected by a fiber path in order to be done.

  At this time, in order to set a packet path, it is necessary to solve problems such as which path should be set with a wavelength path or whether an existing wavelength path should be used.

  In the present invention, a virtual graph is used when performing this route calculation. A method for creating this virtual graph will be described below. First, a fiber layer network graph is assumed to be a virtual graph. Next, the wavelength paths that make up the topology of the wavelength layer are copied to the virtual graph one by one, but at this time, if it has a value smaller than the metric of the virtual link derived from the existing fiber path, this wavelength path is overwritten .

  For example, it is assumed that the metric value of the fiber path between the node A and the node H is 10. At this time, in the topology of the virtual graph, A-H is connected by a link of metric 10. If a wavelength path is set between A and H and the metric of this wavelength path is larger than 10, the value derived from the current fiber path is retained as the metric of the virtual link as it is. If the metric of the wavelength path is smaller than 10 (for example, 5), the link of the virtual topology is overwritten by the wavelength path, and the metric of the link between A and H becomes 5. This is performed for all paths, and a virtual topology graph is created.

  The shortest path is obtained using the virtual topology graph created in this way. At this time, if the virtual link on the shortest path is derived from the wavelength path, this means that the existing wavelength path is used, so the packet path to be set passes through the corresponding wavelength path. To do. If the virtual link on the shortest path is derived from a fiber path, this means that a new wavelength path is established using the existing fiber path, and a packet path is set via the newly established wavelength path. It will be. In this case, after setting the wavelength path on the corresponding fiber path, the packet path is set (Claims 1 and 6).

(Second embodiment)
A second embodiment will be described with reference to FIG. FIG. 6 is a diagram showing weighting factors for each layer. When creating a virtual topology graph according to the flow shown in the first embodiment, there are cases in which metrics of a plurality of paths of different types or the same type are compared between two nodes. At this time, as shown in FIG. 6, the fiber topology path metric is multiplied by 1 while the wavelength topology path metric is multiplied by α, whereby weighting can be performed for each layer. .

  By doing so, it is possible to find α that can accommodate more traffic by changing the value of α by trial and error (claims 2 and 7).

(Third embodiment)
In the second embodiment, more efficient traffic accommodation is possible than in the first embodiment, but the network operator needs to find and set the optimum α in the operation process. In order to omit this operational complexity, a third embodiment is proposed.

  This uses the value of α set in advance to operate the network once. When a certain period of time (a certain number of paths are set or released) elapses, the path setting failure probability (block rate) during this period is held. Thereafter, the value of α is changed, and after a predetermined time has elapsed, the newly calculated block rate is compared with the previous probability. If the new block rate is smaller, a new α is adopted and α is changed again. If the previous block rate is smaller, α is changed in the opposite direction to the first α change. By gradually reducing the width of the change of α, the final value of α is determined when it converges to a value of α (claims 3, 4, 5, 8). 9, 10).

  Since traffic is fluid, it is possible to use the network efficiently and constantly by repeating this periodically for a certain period of time, such as once a month or once a week.

  According to the present invention, in a multi-layer network, network resources can be effectively used regardless of the network configuration or node configuration, which contributes to efficient network operation for both network users and administrators. can do.

The figure which shows the example of the multilayer network of a present Example. The flowchart which shows the virtual graph creation procedure of a present Example. The flowchart which shows the weighting coefficient determination procedure of a present Example. The flowchart which shows the weighting factor convergence procedure of a present Example. The block block diagram of the node of a present Example. It is a figure which shows the weighting coefficient for every layer of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shortest path selection part 2 Virtual graph creation part 3 Virtual graph creation information storage part 4 Minimum cost selection part 5 Weighting calculation part

Claims (17)

In multi-layer network comprised network of a plurality of different layers are layered, walk the calling node or the destination node the shortest path layers and nodes through which the path from the source node to the destination node node In the shortest route selection method of selecting by a route selection device provided separately,
When creating a virtual graph in which the route is virtually set based on each topology in the network of each layer, the line segment connecting the same points is one layer among the line segments constituting the virtual graph of each layer. A shortest path selection method using the line segment of this layer when it exists only in the layer, and selecting the one with the lowest cost from among the line segments when it exists in multiple layers.   After multiplying the weight factor for each layer, if there are multiple line segments that connect the same point among the line segments that make up the virtual graph of each layer, select the one with the lowest cost The shortest path selection method according to claim 1. When determining the weighting factor,
Using the initial weighting factor of each layer, route selection is performed a specified number of times. At this time, after calculating the block rate, which is the ratio when the route to the destination node is not found, the weighting factor value is set to a predetermined value. after changing again the blocking probability calculated by performing routing only a specified number of times, perform the first step you block index and compared to the previously calculated,
If the block rate increases as a result of executing this first step, the initial weighting factor value is changed by a predetermined value in the direction opposite to that of the first step, and then the route is selected a specified number of times. the performed to calculate the blocking probability, performs the second step you block index and compared in the case of the value of the initial weighting factors,
If the block rate decreases as a result of executing the first step, the value after changing by the predetermined value is set as a new weighting factor, and the block rate decreases as a result of executing the second step. If this is the case, the value after changing by a predetermined value in the reverse direction is set as a new weighting factor, and the third step of replacing the new weighting factor with the original weighting factor is performed.
The shortest path selection method according to claim 2 , wherein the first, second, and third steps are repeatedly executed as long as a decrease in the block rate is observed. When there is no decrease in the block rate as a result of executing the first and second steps,
After changing the value of the initial weighting factor by a value obtained by halving the predetermined value, the block ratio is calculated by performing path selection a prescribed number of times, and the block rate in the case of the initial weighting factor value and run the fourth step you compare,
If the block rate does not decrease as a result of executing the fourth step, the initial weighting factor value is changed by a value half the predetermined value in the opposite direction to the fourth step. and then, the blocking probability calculated by performing only routing prescribed number of times, executes a fifth step you block index and compared in the case of the value of the initial weighting factors,
When the block ratio is reduced as a result of executing the fourth step, a value obtained by changing the predetermined value by a half value is used as a new weighting factor, and the result of executing the fifth step. As a result, if the block rate is reduced, the value after changing the predetermined value by half in the reverse direction is used as a new weighting factor, and the new weighting factor is replaced with the original weighting factor. Perform the sixth step ,
The shortest path selection method according to claim 3 , wherein the fourth, fifth, and sixth steps are repeatedly executed until a block rate becomes equal to or less than a threshold value. When the block ratio does not decrease as a result of executing the fourth and fifth steps, the predetermined value is further decreased by half and the fourth , fifth , and sixth steps are repeatedly executed. The shortest path selection method according to claim 4. A multi-layer network composed of multiple layers of different layers, equipped with means for selecting the shortest path of the layer and the node through which the path from the local node to the destination node or from the source node to the local node passes In the node
The means for selecting comprises means for creating a virtual graph in which the route is virtually set based on the topology of each layer network,
This means of creating uses the line segment of this layer when the line segment connecting the same points exists in only one layer among the line segments constituting the virtual graph of each layer, and exists in a plurality of layers. In this case, the node is characterized by having means for selecting one having the smallest cost.   The means for selecting the one with the lowest cost is obtained by multiplying a weighting factor for each layer, and then, among the line segments constituting the virtual graph of each layer, there are line segments connecting the same points in a plurality of layers. 7. The node according to claim 6, further comprising means for selecting one having the lowest cost. Means for determining the weighting factor,
This means of determining is
Using the initial weighting factor of each layer, route selection is performed a specified number of times. At this time, after calculating the block rate, which is the ratio when the route to the destination node is not found, the weighting factor value is set to a predetermined value. after changing again the blocking probability calculated by performing routing only a specified number of times, and means for executing the first step you block index and compared to the previously calculated,
If the block rate increases as a result of executing this first step, the initial weighting factor value is changed by a predetermined value in the direction opposite to that of the first step, and then the route is selected a specified number of times. and means for calculating the blocking probability, performing a second step you block index and compared in the case of the value of the initial weighting coefficients performed,
If the block rate decreases as a result of executing the first step, the value after changing by the predetermined value is set as a new weighting factor, and the block rate decreases as a result of executing the second step. If so, means for executing a third step of replacing the new weighting factor with the original weighting factor , the value after changing the predetermined value in the reverse direction as a new weighting factor ;
The node according to claim 7, further comprising: means for repeatedly executing the first, second, and third steps as long as a decrease in the block rate is observed. When there is no decrease in the block rate as a result of executing the first and second steps,
After changing the value of the initial weighting factor by a value obtained by halving the predetermined value, the block ratio is calculated by performing path selection a prescribed number of times, and the block rate in the case of the initial weighting factor value and It means for executing the fourth step you compare,
If the block rate does not decrease as a result of executing the fourth step, the initial weighting factor value is changed by a value half the predetermined value in the opposite direction to the fourth step. and then, it means for the blocking probability calculated by performing routing only a specified number of times, to perform a fifth step you block index and compared in the case of the value of the initial weighting factors,
When the block ratio is reduced as a result of executing the fourth step, a value obtained by changing the predetermined value by a half value is used as a new weighting factor, and the result of executing the fifth step. As a result, if the block rate is reduced, the value after changing the predetermined value by half in the reverse direction is used as a new weighting factor, and the new weighting factor is replaced with the original weighting factor. Means for performing the sixth step;
The node according to claim 8, further comprising: means for repeatedly executing the fourth, fifth, and sixth steps until a block rate becomes equal to or less than a threshold value. When the block ratio does not decrease as a result of executing the fourth and fifth steps, the predetermined value is further decreased by half and the fourth, fifth and sixth steps are repeatedly executed. 10. A node according to claim 9 comprising means.   A multi-layer network comprising the node according to claim 6. By installing on an information processing device,
The source node or the destination node having a function of selecting a layer through which a path from the source node to the destination node passes and a shortest path of the node in a multi-layer network configured by layering a plurality of networks of different layers Or in a program that realizes a function corresponding to a route selection device provided separately from a node ,
As the function to be selected, the function of creating a virtual graph in which the route is virtually set based on the topology of each layer network is realized,
As a function to be created, when the line segment connecting the same point exists in only one layer among the line segments constituting the virtual graph of each layer, the line segment of this layer is used and exists in a plurality of layers. In this case, a program characterized by realizing a function of selecting the one with the lowest cost.   As a function of selecting the one with the lowest cost, after multiplying each layer by a weighting factor, among the line segments constituting the virtual graph of each layer, there are line segments connecting the same points in a plurality of layers 13. The program according to claim 12, which realizes a function of selecting the one with the lowest cost from among them. Realizing the function of determining the weighting factor;
As this determining function,
Using the initial weighting factor of each layer, route selection is performed a specified number of times. At this time, after calculating the block rate, which is the ratio when the route to the destination node is not found, the weighting factor value is set to a predetermined value. after changing, and again, the blocking probability calculated by performing only routing prescribed number of times, to perform a first step you block index and compared to the previously calculated feature,
If the block rate increases as a result of executing this first step, the initial weighting factor value is changed by a predetermined value in the direction opposite to that of the first step, and then the route is selected a specified number of times. a function of calculating the blocking probability, performing a second step you block index and compared in the case of the value of the initial weighting coefficients performed,
If the block rate decreases as a result of executing the first step, the value after changing by the predetermined value is set as a new weighting factor, and the block rate decreases as a result of executing the second step. If so, a function for executing a third step of replacing the new weighting factor with the original weighting factor, with the value after changing by a predetermined value in the reverse direction as a new weighting factor ,
The program according to claim 13, which realizes a function of repeatedly executing the first, second, and third steps as long as a decrease in the block rate is observed. When there is no decrease in the block rate as a result of executing the first and second steps,
After changing the value of the initial weighting factor by a value obtained by halving the predetermined value, the block ratio is calculated by performing path selection a prescribed number of times, and the block rate in the case of the initial weighting factor value and a function of executing a fourth step you compare,
If the block rate does not decrease as a result of executing the fourth step, the initial weighting factor value is changed by a value half the predetermined value in the opposite direction to the fourth step. and then, the function of the block index calculated by performing only routing prescribed number of times, to perform a fifth step you block index and compared in the case of the value of the initial weighting factors,
When the block ratio is reduced as a result of executing the fourth step, a value obtained by changing the predetermined value by a half value is used as a new weighting factor, and the result of executing the fifth step. As a result, if the block rate is reduced, the value after changing the predetermined value by half in the reverse direction is used as a new weighting factor, and the new weighting factor is replaced with the original weighting factor. The ability to perform the sixth step;
The program according to claim 14, which realizes a function of repeatedly executing the fourth, fifth, and sixth steps until a block rate becomes equal to or less than a threshold value. When the block ratio does not decrease as a result of executing the fourth and fifth steps, the predetermined value is further decreased by half and the fourth, fifth, and sixth steps are repeatedly executed. 16. The program according to claim 15, which realizes a function to perform.   17. A recording medium readable by the information processing apparatus on which the program according to claim 12 is recorded.

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