JP3717064B2 - Photonic node, photonic network, route selection method and program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is used for a photonic network for switching and connecting optical signals. In particular, the present invention relates to a photonic network including a photonic node that performs 3R (Reshaping, Retiming, Regenerating) relay.
[0002]
[Prior art]
In a photonic network, it is necessary to perform 3R processing in the middle of an optical transmission line in consideration of fiber loss, loss, and crosstalk. A conventional photonic network configuration is shown in FIG. In order to perform 3R processing, a 3R repeater is inserted into a node in the middle of the optical transmission path. Although transmission is possible up to a certain distance without performing 3R processing, since complicated calculation is required to determine the distance, 3R relay is performed every one or two stages as shown in FIG. So as to compensate for the deterioration of the optical signal regardless of the route set.
[0003]
Alternatively, there is a usage form in which a 3R repeater is inserted into a specific route of a photonic network, a path is set by using a common route for many paths, and the 3R repeater is shared. However, in this usage mode, the route through which data transfer requires 3R processing is limited.
[0004]
[Problems to be solved by the invention]
A 3R repeater is expensive, and if this 3R repeater is not used as much as possible, a photonic network can be realized extremely economically. However, in the conventional path setting, there is no consideration that the node grasps the usage status of the 3R repeater and sets the path, and each node only knows a predetermined location of the 3R repeater. When a large number of paths share a small number of 3R repeaters, there is a possibility that a large number of loads are concentrated on some 3R repeaters. In addition, if a large number of paths share a small number of 3R repeaters, it is necessary for the paths to always pass through the insertion location of the 3R repeater, which reduces the flexibility of path setting.
[0005]
For example, even when there is a request to add a new path to a specific route where the 3R load is concentrated, there is a situation where a path cannot be set for that route even though another route is available.
[0006]
The present invention has been implemented against this background, and realizes a highly flexible photonic network even if a photonic network is configured while effectively using network resources using a small number of 3R repeaters. An object of the present invention is to provide a photonic node, a photonic network, and a route selection method that can flexibly cope with addition of a new path.
[0007]
[Means for Solving the Problems]
The present invention is characterized in that a path can be set for a route with a low 3R processing load by setting the path in consideration of the 3R relay cost when setting the path. As a result, even when a photonic network is configured while effectively using network resources using a small number of 3R repeaters, it is possible to avoid a situation where the 3R processing load is concentrated at a specific location. Therefore, a highly flexible photonic network can be realized, and it is possible to flexibly cope with the addition of a new path by effectively using a free route.
[0008]
That is, the first aspect of the present invention is applied to a photonic network for exchanging and connecting optical signals, and between the means for exchanging and connecting optical signals and the own node and the destination node when the own node is a source node. And a means for setting a path between the own node and the destination node based on the search result, and the 3R repeater is used with or without one or more 3R repeaters. Either a photonic node or an unused state is selected.
[0009]
Here, the feature of the present invention is that it includes means for obtaining a shortest test path that minimizes the number of passing nodes between the self node and the destination node, and means for calculating the 3R relay cost of the shortest path. The path setting means sets the show test path when there is one show test path, and sets the show test path to minimize the 3R relay cost of the show test path when there are a plurality of show test paths. It is in the place with the means to select and set.
[0010]
Thereby, selection of a plurality of paths including the 3R relay cost can be considered, and the path with the lowest 3R relay cost can be selected. Here, the path with a low 3R relay cost is a path with a low 3R processing load.
[0011]
Means may be provided for calculating the reciprocal of the number of unused 3R repeaters in all nodes existing on the Shortest path as the 3R relay cost of the Shortest path. That is, whether the 3R processing load is high or low can be expressed by whether there are many or few unused 3R repeaters.
[0012]
Alternatively, the 3R relay cost of the Shortest path is a value obtained by subtracting 1 from the number of unused 3R repeaters in the number of all 3R repeaters included in all nodes existing on the Shortest path. Means for calculating the divided value as the 3R relay cost can be provided.
[0013]
That is, whether the 3R processing load is high or low can be expressed by whether the usage rate of the 3R repeater in the node is high or low. Here, the reason why the number of all 3R repeaters included in the own node is divided by a value obtained by subtracting 1 from the number of unused 3R repeaters will be described. For example, from the beginning, there are 100 3R repeaters. When there is a node and a node that has only one 3R repeater from the beginning, if the value obtained by subtracting 1 from the number of unused 3R repeaters is not used, all 3R repeaters are unused In addition, the former 3R relay cost is 100/100 = 1, but the latter 3R relay cost is also 1/1 = 1, which is the same 3R relay cost. However, in such a case, as a matter of course, it is desirable to select a node having 100 3R repeaters. In order to eliminate such inconvenience, a value obtained by subtracting 1 from the number of unused 3R repeaters is used. In addition, when the number of unused 3R repeaters is one, the calculation formula is n / (1-1) = n / 0 (n is the total number of 3R repeaters), and the calculation formula does not hold. In such a case, the 3R relay cost may be defined as being infinite or extremely large. Further, when the number of unused 3R repeaters is 0, the arithmetic expression is n / (0-1) = − n, and the 3R relay cost takes a negative value. It may be defined that the relay cost is infinite or extremely large.
[0014]
Further, the means for selecting sets the cost of another node not including the 3R repeater included in the shortest path as x, and the 3R relay cost of another node including the 3R repeater included in the shortest path. When the cost including Y is y, the weighting factor of the cost y is α, and the cost of the entire show test path is Cost, the calculation result of Cost = Σx + αΣy and the calculation result of the calculation means are minimized. Means for selecting a show test pass. In this way, the optimum path can be selected by comprehensively evaluating the cost of the show test path including the 3R cost.
[0015]
Alternatively, the present invention is characterized in that, when there are a plurality of searched paths, the means for setting the path includes a 3R repeater having all the nodes included in all the searched paths. There is provided means for searching for a node having the largest number of nodes and setting a path including a node having the largest number of 3R repeaters.
[0016]
Alternatively, the feature of the present invention is that, when there are a plurality of searched paths, the means for setting the path is an unused 3R among all nodes included in all the searched paths. The node having the largest number of repeaters is searched, and a path including the node having the largest number of unused 3R repeaters is set.
[0017]
Alternatively, the feature of the present invention is that, when there are a plurality of searched paths, the means for setting the path includes, for each of the searched paths, all nodes included in the path. A value obtained by subtracting 1 from the total of 3R repeaters in use and dividing the sum by the sum of 3R repeaters of all nodes included in the path, and setting a path that maximizes the divided value. It is in.
[0018]
A second aspect of the present invention is a photonic network comprising the photonic node of the present invention.
[0019]
According to a third aspect of the present invention, there are provided means for exchanging and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and the own node based on the search result. And a means for setting a path between the destination node and one or more 3R repeaters, wherein the 3R repeater is selected to be used or unused. This is a route selection method applied to a photonic network having nodes.
[0020]
Here, the present invention is characterized in that a shortest path that minimizes the number of passing nodes between the self node and the destination node is obtained, the 3R relay cost of the shortest path is calculated, and the path is set. When there is one show test path, it is set as a show test path, and when there are a plurality of show test paths, a show test path that minimizes the 3R relay cost of the show test path is selected and set. There is a place to do.
[0021]
As the 3R relay cost of the Shortest path, the reciprocal of the number of unused 3R relays in all nodes existing on the Shortest path can be calculated.
[0022]
Alternatively, the 3R relay cost of the Shortest path is a value obtained by subtracting 1 from the number of unused 3R repeaters in the number of all 3R repeaters included in all nodes existing on the Shortest path. The divided value can also be calculated as the 3R relay cost.
[0023]
In addition, the cost of another node that does not include the 3R repeater included in the Shortest path is x, and the cost that includes the 3R relay cost of another node that includes the 3R repeater included in the Shortest path is y. Then, when the weighting coefficient of the cost y is α and the cost of the entire show test path is Cost, it is calculated as Cost = Σx + αΣy, and the show test path that minimizes the calculation result can be selected.
[0024]
Alternatively, a feature of the present invention is that, when the path is set, when there are a plurality of searched paths, the 3R repeater having all of the nodes included in all the searched paths The node having the largest number of nodes is searched and a path including the node having the largest number of 3R repeaters is set.
[0025]
Alternatively, the present invention is characterized in that, when the path is set, if there are a plurality of searched paths, an unused 3R is selected from all the nodes included in all the searched paths. The node having the largest number of repeaters is searched, and a path including the node having the largest number of unused 3R repeaters is set.
[0026]
Alternatively, the present invention is characterized in that when there are a plurality of searched paths when the path is set, for each of the searched paths, all the nodes included in the path have no search. A value obtained by subtracting 1 from the total of 3R repeaters in use and dividing the sum by the sum of 3R repeaters of all nodes included in the path, and setting a path that maximizes the divided value. It is in.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
A photonic node and a photonic network according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of a photonic network according to the present embodiment. FIG. 2 is a block diagram of the photonic node of this embodiment. FIG. 3 is a configuration diagram of the announcement packet of this embodiment. FIG. 4 is a diagram showing an example of a photonic network for explaining the third embodiment.
[0028]
(First Example)
In the first embodiment, the 3R relay cost calculation unit 5 uses the reciprocal of the number of unused 3R relays 7i (i is any one of 1 to n) in the own node as the 3R relay cost of the own node. Calculate as That is, whether the 3R processing load is high or low can be expressed by whether there are many or few unused 3R repeaters. For example, if the number of unused 3R repeaters 7i of the own node is equal to all the 3R repeaters 71 to 7n, the 3R relay cost becomes (1 / n) and becomes a small value, so there is a sufficient margin for the 3R relay capability. I know that there is. Further, if the number of unused 3R repeaters 7i of the own node is “0”, it becomes (1/0) and the arithmetic expression does not hold, but this is defined as infinite or extremely large value, thereby 3R It can be expressed that there is no margin in the relay capability. The possible range of the 3R relay cost in this case is, for example, 0 <3R relay cost <∞.
[0029]
(Second embodiment)
In the second embodiment, the 3R relay cost calculation unit 5 subtracts 1 from the number of unused 3R repeaters 7i by subtracting the number of all 3R repeaters 71 to 7n included in the own node as the 3R relay cost of the own node. The value divided by the calculated value is calculated as the 3R relay cost. That is, whether the 3R processing load is high or low can be expressed by whether the usage rate of the 3R repeater in the node is high or low. For example, when the number of all 3R repeaters 71 to 7n in the own node is 100, if the number of unused 3R repeaters 7i in the own node is equal to all 3R repeaters 71 to 7n, the 3R relay cost is (100/99), and if the number of unused 3R repeaters 7i of the own node is “1”, the calculation formula does not hold because it is (100/0), but this is an infinite or extremely large value. It can be seen that there is no margin in 3R relay capability. When the number of unused 3R repeaters 7i is “0”, the arithmetic expression is 100 / (0−1) = − 100, and the 3R relay cost takes a negative value. In addition, it may be defined that the 3R relay cost is infinite or extremely large.
[0030]
In this case, the possible range of the 3R relay cost is, for example, 1 <3R relay cost <∞. The reason why 1 is subtracted from the number of unused 3R repeaters 7i is as described above.
[0031]
(Third embodiment)
In the third embodiment, the path setting unit 3 sets x as the cost of another node that does not include the 3R repeater included in the show test path based on the network topology, and shows the show test path based on the total result of the 3R relay cost totaling unit 4. When the cost including the 3R relay cost of the other node including the 3R repeater included in is taken as y, the weighting coefficient of the cost y is assumed as α, and the cost of the entire show test path is assumed as Cost, it is calculated as Cost = Σx + αΣy Then, the show test path that minimizes the calculation result is selected.
[0032]
The weighting coefficient α is a coefficient for weighting the cost including the 3R relay cost of the other node having the 3R repeater with respect to the cost of the other node not having the 3R repeater, for example, two photonic networks If the number of 3R repeaters in one photonic network is larger than the number of 3R repeaters in the other photonic network, the value of the coefficient α in the photonic network having a relatively large number of 3R repeaters May be smaller than the value of the coefficient α in the other photonic network.
[0033]
That is, as shown in FIG. 4, there are routes # 1 and # 2 as show test paths, white circles on each route are 3R non-relay nodes without 3R repeaters, and black circles are 3R with 3R repeaters A node that performs relay. Here, the cost of the 3R non-relay node of route # 1 is 5, and the costs of the nodes that perform 3R relay are 7 and 9. The cost of the 3R non-relay node of route # 2 is 5, and the cost of the node that performs 3R relay is 7. The weighting coefficient α is 2.
[0034]
At this time, the cost of route # 1 is Cost = 5 + 2 (7 + 9) = 37. The cost of route # 2 is Cost = (5 + 5 + 5) +2 (7) = 29. As a result, it can be seen that route # 2 has a larger number of hops, but the cost including the 3R relay cost of the entire show test path is small. Therefore, the path setting unit 3 selects route # 2 and selects route # 2 A path setting request is sent to each node.
[0035]
(Fourth embodiment)
The function of controlling the photonic node of this embodiment can be realized by using a computer device that is an information processing device. That is, by installing in a computer device, the optical device is applied to a photonic network for exchanging and connecting optical signals to the computer device. When the own node is a source node, the own node is used. Route calculation unit 2 that calculates the show test path that minimizes the number of passing nodes between the destination node and the destination node, and sets a path between the own node and the destination node based on the calculation result of the route calculation unit 2 3R relay cost for calculating a 3R relay cost of the own node, which is a program for realizing a function of controlling a photonic node including or not including one or more 3R repeaters 71 to 7n. Functions corresponding to the calculation unit 5 and calculation results of the 3R relay cost calculation unit 5 A function corresponding to the 3R relay cost notifying unit 6 for notifying the other nodes, and a function corresponding to the 3R relay cost totaling unit 4 for counting the 3R relay costs announced from other nodes in correspondence with the addresses of the other nodes. As a function corresponding to the path setting unit 3, when there are a plurality of calculation results of the route calculation unit 2, a shortest test path that minimizes the 3R relay cost is selected based on the aggregation result of the 3R relay cost aggregation unit 4 By installing the program for realizing the function to be installed in the computer device, the computer device can realize the function of controlling the photonic node of this embodiment.
[0036]
Further, as a function corresponding to the 3R relay cost calculation unit 5, a computer program that realizes a function for calculating the inverse of the number of unused 3R relays 7i in the local node as the 3R relay cost of the local node is calculated as the 3R relay cost. By installing in the apparatus, the function of controlling the photonic node of the first embodiment described above can be realized in the computer apparatus.
[0037]
Alternatively, as a function corresponding to the 3R relay cost calculation unit 5, the number of all 3R repeaters 71 to 7n included in the own node is subtracted from the number of unused 3R repeaters 7i as the 3R relay cost of the own node. By installing in the computer device a program that realizes the function of calculating the value divided by the value as the 3R relay cost, the computer device is allowed to realize the function of controlling the photonic node of the second embodiment described above. be able to.
[0038]
Alternatively, as a function corresponding to the path control unit 3, the cost of another node that does not include the 3R repeater included in the show test path based on the network topology is x, and the show test path is based on the total result of the 3R relay cost totaling unit 5. When the cost including the 3R relay cost of the other node including the 3R repeater included in is taken as y, the weighting coefficient of the cost y is assumed as α, and the cost of the entire show test path is assumed as Cost, it is calculated as Cost = Σx + αΣy And a program for realizing the shortest test path that minimizes the calculation result of the function to be calculated is installed in the computer device, and the photonic of the third embodiment described above is installed in the computer device. The function of controlling the node can be realized.
[0039]
By recording the program of the present embodiment on the recording medium of the present embodiment, the computer apparatus can install the program of the present embodiment using this recording medium. Alternatively, the program of this embodiment can be directly installed on the computer device from the server holding the program of this embodiment via the network.
[0040]
As a result, a highly flexible photonic network can be realized even if a photonic network is configured using a small number of 3R repeaters while effectively using network resources using a computer device, and it is flexible to add new paths. It is possible to realize a photonic node and a photonic network that can cope with the above.
[0041]
(Fifth embodiment)
As a photonic node, when the local node is the source node, search the path between the local node and the destination node, and set the path between the local node and the destination node based on the search result When there are a plurality of searched paths, the node having the largest number of 3R repeaters is searched from all the nodes included in all the searched paths, and the number of the 3R repeaters is determined. Set the path that contains the node with the most. Alternatively, the node having the largest number of unused 3R repeaters is searched from all the nodes included in all the searched paths, and the path including the node having the largest number of unused 3R repeaters is set. . Alternatively, for each of the searched paths, the value obtained by subtracting 1 from the sum of the 3R repeaters of all the nodes included in the path is divided by the sum of the 3R repeaters of all the nodes included in the path. Calculate the value and set the path that maximizes the divided value.
[0042]
【The invention's effect】
As described above, according to the present invention, a highly flexible photonic network can be realized even if a photonic network is configured using a small number of 3R repeaters while effectively using network resources. It can respond flexibly to the addition.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a photonic network according to an embodiment.
FIG. 2 is a block diagram of a photonic node according to the present embodiment.
FIG. 3 is a configuration diagram of a notification packet according to the present embodiment.
FIG. 4 is a diagram showing an example of a photonic network for explaining a third embodiment.
FIG. 5 is a diagram showing a conventional photonic network configuration.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical cross-connect 2 Route calculation part 3 Path setting part 4 3R relay cost totaling part 5 3R relay cost calculation part 6 3R relay cost notification part 71-7n 3R repeater

Claims (19)

Applied to a photonic network for switching and connecting optical signals, means for switching and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and the search result And a means for setting a path between the own node and the destination node based on
In a photonic node with or without one or more 3R (Reshaping, Retiming, Regenerating) repeaters, the 3R repeater being used or unused
Means for obtaining a show test path that minimizes the number of passing nodes between the self node and the destination node;
Means for calculating the 3R relay cost of the show test pass,
The means for setting the path sets the shortest test path as a path when there is one shortest test path, and selects the shortest test path that minimizes the 3R relay cost of the shortest test path when there are a plurality of shortest test paths. A photonic node characterized by having a means for setting.   The photonic node according to claim 1, further comprising means for calculating a reciprocal of the number of unused 3R repeaters in all nodes existing on the Shortest path as a 3R relay cost of the Shortest path.   As the 3R relay cost of the Shortest path, the number of all 3R repeaters included in all nodes existing on the Shortest path is divided by the value obtained by subtracting 1 from the number of unused 3R repeaters. The photonic node according to claim 1, further comprising means for calculating a value as the 3R relay cost. The means for selecting is
The cost of another node that does not include the 3R repeater included in the Shortest path is x, and the cost that includes the 3R relay cost of another node that includes the 3R repeater included in the Shortest path is y, When the weighting coefficient of the cost y is α and the cost of the entire show test pass is Cost,
Cost = Σx + αΣy
As a means to calculate as
The photonic node according to claim 1, further comprising: a path that selects a path that minimizes a calculation result of the calculating means. Applied to photonic networks that exchange and connect optical signals,
Means for exchanging and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and a path between the own node and the destination node based on the search result And means for setting
In a photonic node with or without one or more 3R repeaters, where the 3R repeater is selected to be either used or unused,
The means for setting the path searches for a node having the largest number of 3R repeaters from among all nodes included in all the searched paths when there are a plurality of searched paths. A photonic node comprising means for setting a path including a node having the largest number of 3R repeaters. Applied to a photonic network for switching and connecting optical signals, means for switching and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and the search result And a means for setting a path between the own node and the destination node based on
In a photonic node with or without one or more 3R repeaters, where the 3R repeater is selected to be either used or unused,
When there are a plurality of searched paths, the means for setting the path searches for a node having the largest number of unused 3R repeaters from all nodes included in all the searched paths. A path including a node having the largest number of unused 3R repeaters is set. Applied to a photonic network for switching and connecting optical signals, means for switching and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and the search result And a means for setting a path between the own node and the destination node based on
In a photonic node with or without one or more 3R repeaters, where the 3R repeater is selected to be either used or unused,
When there are a plurality of searched paths, the means for setting the path subtracts 1 from the total of unused 3R repeaters of all nodes included in the path for each of the searched paths. A value obtained by dividing the obtained value by the sum of the 3R repeaters of all nodes included in the path is calculated, and a path that maximizes the divided value is set. Means for exchanging and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and a path between the own node and the destination node based on the search result And means for setting
In a route selection method applied to a photonic network comprising a photonic node with or without one or more 3R repeaters, wherein the 3R repeaters are selected to be used or unused.
When a shortest path that minimizes the number of passing nodes between its own node and the destination node is obtained, the 3R relay cost of the shortest path is calculated, and when the shortest path is set, A route selection method characterized by: setting a path as a path, and selecting and setting a shortest path that minimizes the 3R relay cost of the shortest path when there are a plurality of shortest paths.   The route selection method according to claim 8, wherein a reciprocal of the number of unused 3R repeaters in all nodes existing on the Shortest path is calculated as a 3R relay cost of the Shortest path.   As the 3R relay cost of the Shortest path, the number of all 3R repeaters included in all nodes existing on the Shortest path is divided by the value obtained by subtracting 1 from the number of unused 3R repeaters. The route selection method according to claim 8, wherein the value is calculated as the 3R relay cost. The cost of the other node that does not include the 3R repeater included in the Shortest path is x, and the cost that includes the 3R relay cost of the other node that includes the 3R repeater included in the Shortest path is y, When the weighting coefficient of the cost y is α and the cost of the entire show test pass is Cost,
Cost = Σx + αΣy
9. The route selection method according to claim 8, wherein a shortest test path that minimizes the calculation result is selected. Means for exchanging and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and a path between the own node and the destination node based on the search result And means for setting
In a route selection method applied to a photonic network comprising a photonic node with or without one or more 3R repeaters, wherein the 3R repeaters are selected to be used or unused.
When setting the path, if there are a plurality of searched paths, search for a node having the largest number of 3R repeaters from all nodes included in all the searched paths, A route selection method comprising setting a path including a node having the largest number of 3R repeaters. Means for exchanging and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and a path between the own node and the destination node based on the search result And means for setting
In a route selection method applied to a photonic network comprising a photonic node with or without one or more 3R repeaters, wherein the 3R repeaters are selected to be used or unused.
When setting the path, if there are a plurality of searched paths, the node having the largest number of unused 3R repeaters is searched from all the nodes included in all the searched paths. A route selection method including setting a path including a node having the largest number of unused 3R repeaters. Means for exchanging and connecting optical signals, means for searching for a path between the own node and the destination node when the own node is a source node, and a path between the own node and the destination node based on the search result And means for setting
In a route selection method applied to a photonic network comprising a photonic node with or without one or more 3R repeaters, wherein the 3R repeaters are selected to be used or unused.
When setting the path, if there are a plurality of searched paths, subtract 1 from the total of unused 3R repeaters of all nodes included in the path for each of the searched paths. A route selection method comprising: calculating a value obtained by dividing the obtained value by the sum of the 3R repeaters of all nodes included in the path, and setting a path that maximizes the divided value.   A photonic network comprising the photonic node according to claim 1. By installing on an information processing device,
Applied to a photonic network for exchanging and connecting optical signals, means for exchanging and connecting optical signals, means for retrieving a path between the own node and the destination node when the own node is a source node, and the search result And a means for setting a path between the own node and the destination node based on the above, the 3R repeater is provided with one or more 3R repeaters, and the 3R repeater is selected to be used or unused. A program for realizing a function for controlling a photonic node,
A function for obtaining a shortest test path that minimizes the number of passing nodes between the own node and the destination node;
A function for calculating the 3R relay cost of the show test pass;
Realized,
As a function of setting the path, when there is one show test path, it is set as a path, and when there are a plurality of show test paths, a show test path that minimizes the 3R relay cost of the show test path is selected. To realize the function to be set
A program characterized by that. The program according to claim 16, which realizes a function of calculating a reciprocal of the number of unused 3R repeaters in all nodes existing on the Shortest path as the 3R relay cost of the Shortest path. As the 3R relay cost of the Shortest path, the number of all 3R repeaters included in all nodes existing on the Shortest path is divided by the value obtained by subtracting 1 from the number of unused 3R repeaters. The program according to claim 16, which realizes a function of calculating a value as the 3R relay cost. The function to select is
Let x be the cost of another node that does not include the 3R repeater included in the Shortest path, and 3R relay cost of the other node that includes the 3R repeater included in the Shortest path. When the cost to include is y, the weighting coefficient of the cost y is α, and the cost of the entire show test path is Cost,
Cost = Σx + αΣy
With the ability to calculate as
A function for selecting a path with the smallest calculation result of the function to be calculated;
The program of Claim 16 which implement | achieves.

Images