JP3899096B2 - Route control apparatus and route selection method - Google Patents

Description

  The present invention relates to a packet communication technology, and more particularly to a route selection technology for selecting an optimum route used for packet communication.

  In recent years, the traffic volume of a large-scale backbone network in the center of the Internet has increased explosively due to the rapid increase in the number of users of the Internet and the rapid spread of applications that exchange large amounts of data. Therefore, there is a demand for improving the capacity of the backbone network to accommodate traffic.

  In order to distribute traffic and improve the traffic capacity of the backbone network, multiple routes that do not go through the same node or link between the same nodes are set, and traffic is distributed dynamically according to the traffic situation. Engineering technology is being considered. In addition, it is also used to improve the reliability of the network by switching to another route when one route becomes incapable of communication (see, for example, Non-Patent Document 1).

As a route selection method for selecting a plurality of routes between the same nodes, there is an equivalent multipath algorithm (Equal Cost Multi Path) improved from the shortest route routing algorithm (Shortest Path First). This algorithm calculates a plurality of routes having the same cost between the same nodes (see, for example, Non-Patent Document 2).
However, the above route selection method cannot output a plurality of these routes when there are only routes with different costs between the same nodes. In particular, when an individual traffic amount is used for a link as a cost, the traffic amount is often greatly different for each link, and it is unlikely that a route with the same cost exists. For this reason, there is a problem that a plurality of routes cannot always be calculated.

  On the other hand, the mathematical programming method has been used as a method for finding an optimal solution by regarding the route selection problem in which traffic is distributed between the same nodes without going through the same nodes and links as a combination optimization problem. A method using a genetic algorithm (GA) or a simulated annealing method (SA) has been proposed (see, for example, Non-Patent Document 3).

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
"Priority Control / Route Control Method Based on Deadline in IP Networks", IEICE Transactions VOL.J86-B No.12, p2501, IEICE, December 2003 "RFC3272 Overview and Principles of Internet Traffic Engineering", p30, THE INTERNET ENGINEERING TASK FORCE, May 2002 "Next Generation Internet and Traffic Engineering", IEICE Transactions VOL.J85-B No.6, pp875-889, IEICE, June 2002

  However, in such a conventional technology, calculation time tends to increase rapidly as the scale of the problem increases. When individual traffic information or the like is used as a cost for each link, the traffic volume actually increases for each link. In many cases, it takes different time to calculate a plurality of routes between the same nodes. For this reason, in a large-scale network such as a backbone network, there is a problem that the applicability as a route selection method in dynamic route control with respect to traffic fluctuations such as traffic engineering technology is low.

  The present invention is for solving such problems, and even when individual traffic volume is used for each link as the link cost, the calculation processing load can be reduced, and a plurality of routes can be quickly selected between the same nodes. It is an object of the present invention to provide a route control device and a route selection method.

  In order to achieve such an object, a routing control device according to the present invention is provided in a packet communication network including a plurality of nodes connected in a network via a link, and the following is performed from a transmission source node that performs packet communication. A route control device that selects a route from a transmission source node to a desired destination node by sequentially selecting a route to a node from the network, and includes link information indicating a packet transfer status in each link. When selecting a link information collection unit that collects from a node and a route from a source node to an arbitrary node, based on the optimization parameter value that evaluates the route to the node, either of the routes to the node The route selection unit selected as the route to the node, the link information collected by the link information collection unit, the optimization parameter value of the node, and And a storage unit that stores the route to each node selected by the route selection unit, and when the optimization parameter value of the node is calculated by the route selection unit, the route to the node stored in the storage unit is configured. When the optimization parameter value is calculated from the link information of each link to be selected, the route selection unit first selects the route from the transmission source node to the destination node when selecting the second route different from the first route. Thereafter, a new topology of the network is created from the links and nodes excluding the links and nodes constituting the first route, and the route from the destination node to any node in the topology as the second half route of the second route Is selected from the topology, and the first half path from the source node to any node in the topology is selected from the storage unit as the first half path of the second path, and the first half path and the second half path are combined. Selecting a path as a second path.

  At this time, the route selection unit may select a node having the maximum optimization parameter value from the storage unit as a node that becomes a connection point between the first half route and the second half route.

  Also, the route selection method according to the present invention is a route control device provided in a packet communication network composed of a plurality of nodes connected in a network via a link, from a transmission source node that performs packet communication to the next node. A route selection method for selecting a route from a source node to a desired destination node by sequentially selecting a route from the network, and collecting link information indicating the packet transfer status at each link from each node. Link information collection step, and when selecting a route from a source node to an arbitrary node, based on an optimization parameter value that evaluates the route to the node, either of the routes to the node Route selection step to select as a route, link information collected by the link information collection unit, optimization parameter value of the node, And a storage step for storing the route to each node selected by the route selection unit in the storage unit. When calculating the optimization parameter value of the node in the route selection step, the storage unit stores the route to the node stored in the storage unit. When the optimization parameter value is calculated from the link information of each link constituting the route, and the second route different from the first route is selected in the route selection step, the route from the transmission source node to the destination node is first selected. And creating a new topology of the network from the links and nodes excluding the links and nodes constituting the first route, and selecting the second half route of the second route from the destination node in the topology. Selecting a path from the source node to any node in the topology as a first half path of the second path. The routing performed a selection step from the storage unit, and selecting a route obtained by synthesizing the first half path and the second half path as the second pathway.

  At this time, in the route selection step, a node having the maximum optimization parameter value may be selected from the storage unit as a node serving as a connection point between the first half route and the second half route.

  According to the present invention, when the route selection unit of the route control unit selects the second route different from the first route, after the route from the transmission source node to the destination node is first selected, A new topology of the network is created from the links and nodes excluding the links and nodes that constitute one route, and the route from the destination node to any node in the topology is selected from the topology as the second half route of the second route As the first half path of the second path, the first half path from the transmission source node to any node in the topology is selected from the storage unit, and the path combining the first half path and the second half path is selected as the second path. The

  Thereby, the calculation result of the first route can be reused for the first half of the second routes. Therefore, as compared with the conventional methods for finding the optimal solution, mathematical programming, genetic algorithm (GA), or simulated annealing (SA) is used for route selection. Even when an individual traffic amount is used for each link as the link cost, the calculation processing load can be reduced, and a plurality of routes can be quickly selected between the same nodes.

Next, embodiments of the present invention will be described with reference to the drawings.
[Network model]
First, a communication network to which a path control device according to an embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 is a block diagram illustrating an example of a network model of a communication network to which a route control device according to an embodiment of the present invention is applied.
This communication network includes user accommodation devices 10 and 11, relay devices 20 and 21, and a route control device 30, and each user terminal 40 and 41 is accommodated in each of the user accommodation devices 10 and 11 via a link. ing.

The user accommodation devices 10 and 11 are connected by links 100 to 104 and relay devices 20 and 21. The route control device 30 is connected to the user accommodation devices 10 and 11 and the relay devices 20 and 21 via the management network 300.
Below, the backbone network 200 is comprised from the user accommodation apparatuses 10 and 11, the relay apparatuses 20 and 21, and the links 100-104 which connect between the user accommodation apparatuses 10 and 11 and the relay apparatuses 20 and 21. FIG. The user accommodation devices 10 and 11 and the relay devices 20 and 21 are referred to as nodes constituting the backbone network 200.

[Route control device]
Next, a route control device according to an embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the path control device according to the embodiment of the present invention.
The route control device 30 is composed of an information processing device having a computer as a whole, and is provided with a link information collection unit 31, a route selection unit 32, a route control unit 33, and a storage unit. Each of these units executes a program in the CPU, and cooperates hardware and the program to realize a functional unit, and communication for transmitting and receiving control packets via the management network 300 It is comprised from the interface part (not shown).

  The link information collection unit 31 includes a functional unit realized by the arithmetic processing unit. From the communication interface unit via the management network 300, the user accommodation devices 10 and 11 and the relay devices 20 and 21 are connected to each link. A function of collecting link information indicating a packet transfer status, for example, traffic volume, and a function of updating a link cost table stored in the storage unit 34 based on a cost value obtained from the collected link information (for example, reciprocal of traffic volume). Have.

  The route selection unit 32 includes a functional unit realized by the arithmetic processing unit, and calculates a route from a packet communication transmission source node (originating node) to a destination node (destination node) using a Dijkstra-based algorithm. A route that is a route selection result and the optimization parameter value of the node on the route in the optimization parameter table and the route stack of the storage unit 34, and a link and a node on the route by searching the route stack For the link availability table and the node availability table in the storage unit 34.

  In addition to this, the route selection unit 32 searches the link availability table and the node availability table with the availability flag, and creates a new topology composed of only usable nodes and links, A function to check whether the route from the source node to the destination node exists on the created topology, a function to search the node having the maximum value by sorting the optimization parameter table by the node optimization parameter value, and the destination It has a function of calculating a route from the node to the node on the topology, and a function of storing the calculation result in the route stack.

  The optimization parameter value referred to in the present invention is a value used as a selection criterion when selecting a route from a packet communication source node to an arbitrary node u, and evaluates the route to the node u. It is an evaluation value. For example, in the MIN-MAX algorithm, when selecting a route to an arbitrary node u, an optimization parameter is obtained for each route to the node u, and a route having the maximum optimization parameter is selected. At this time, for the route to the node v that has already been route-selected and is adjacent to the node u via the link, for example, the minimum value of the cost of the link constituting the selected route from the source node to the node v, that is, The optimization parameter of node u is used.

The route control unit 33 includes a functional unit realized by the arithmetic processing unit, and has a function of searching the route stack stored in the storage unit 34 and the searched route via the management network 300 from the communication interface unit. The user accommodation devices 10 and 11 and the relay devices 20 and 21 have a function to be set.
The storage unit 34 includes a storage device such as a hard disk or a memory, and includes a link cost table 34A, an optimization parameter table 34B, a path stack 34C, a link availability table 34D, a node availability table 34E, and a MIN-MAX algorithm parameter. The table 34F is managed by a database, and has a function of providing a managed value or changing and saving it according to access from the link information collection unit 31, the route selection unit 32, and the route control unit 33. is doing.

3 is a configuration example of the link cost table 34A managed by the storage unit 34, FIG. 4 is a configuration example of the optimization parameter table 34B managed by the storage unit 34, and FIG. 4 is a configuration example of a path stack 34C managed by the unit 34.
6 is a configuration example of the link availability table 34D managed by the storage unit 34, and FIG. 7 is a configuration example of the node availability table 34E managed by the storage unit 34. In either case, examples of values before the start of route selection are shown.

  The link cost table 34A is obtained from the link information collected by the link information collection unit 31 as the link evaluation value for each of the links 100 to 104 connecting the user accommodation devices 10 and 11 and the relay devices 20 and 21. Link cost is managed. In the optimization parameter table 34B, the optimization parameter value is managed for each node. The path stack 34C manages the path from the packet communication source node to the node for each node.

  In the link availability table 34D, the availability of the link is managed for each of the links 100 to 104. In the node availability table 34E, the availability of the node is managed for each of the nodes 10, 11, 20, and 21. In the MIN-MAX algorithm parameter table 34F, as parameters used in the MIN-MAX algorithm, for example, a route that is a selection result and optimization parameter values of each node are managed.

  In this embodiment, the route selection unit 32 of the route control device 30 sequentially selects a route from the transmission source node that performs packet communication to the next node from the network by a Dijkstra-based route selection algorithm. The route from the transmission source node to the desired destination node is selected. Then, when one route from the source node to the destination node is calculated, the route from the source node to another node is selected at the same time, and the route from the destination node to the other node is selected. The other route from the transmission source node to the destination node is calculated by combining with the already selected route.

Specifically, after selecting a first route from a packet communication source node to a destination node, a new topology excluding links and nodes constituting the route is created, and the optimization calculated when the first route is selected The latter half route from the node having the largest parameter value to the destination node is selected on the topology, and the first half route and the latter half route from the source node selected at the time of selecting the first route to the node having the largest optimization parameter value Is selected as a second route from the destination node to the transmission source node, which is different from the first route.
As a result, the calculation result of the first route can be reused, and even when an individual traffic amount is used for each link as the link cost, the calculation processing load can be reduced, and a plurality of routes can be quickly connected between the same nodes. You can choose.

[Operation of route control device]
Next, with reference to FIG. 8, the operation of the path control apparatus according to the embodiment of the present invention will be described. FIG. 8 is a flowchart showing route selection processing in the route control device according to the embodiment of the present invention.
Hereinafter, as a route from the user accommodation device 10 serving as the transmission source node to the user accommodation device 11 serving as the destination node of the packet in the communication network of FIG. 1 described above, MIN, which is one of the Dijkstra-based route selection algorithms. A case where a plurality of routes are selected based on the MAX algorithm will be described as an example.

  First, the path control device 30 collects link information of the links 100 to 104 from the user accommodation devices 10 and 11 and the relay devices 20 and 21 via the management network 300 by the link information collection unit 31, and the link information. The link cost obtained from (1), for example, consisting of the reciprocal of the traffic volume is stored in the link cost table 34A of the storage unit 34 (step 500). In this example, it is assumed that the link costs having the contents shown in FIG. 10 are stored as the link cost table 34A in the initial state.

[Selection of the first route]
Next, the path control device 30 uses the MIN-MAX algorithm (see, for example, Patent Document 1) to sequentially select a path from the transmission source node to an arbitrary node from the network, thereby transmitting the transmission source. A first route from a node to a desired destination node is selected (step 501). At this time, as a route from the transmission source node to an arbitrary node, a route from which the minimum value of the cost of each link constituting each route is maximized is selected from among the routes to the node.
FIG. 10 is an explanatory diagram showing definitions and notations relating to the MIN-MAX algorithm used in this case. In this notation, the device means a user accommodation device or a relay device.

  At the start of processing of the MIN-MAX algorithm, each parameter is initialized. FIG. 11 shows the stored contents of the MIN-MAX algorithm parameter table 34F in the initial state. At this time, the value of the MIN-MAX algorithm parameter in FIG. 11 is the same as the value of the parameter shown in the definition of FIG. Of these, the set V is a set of all devices that are subject to route selection. The set U is a set of devices whose paths are determined, and is Φ (empty set) in the initial state. Therefore, the set V-U is a set of devices that are undefined routes, that is, route selection candidates. The route is a route to an arbitrary device determined by the route selection process, and C is an optimization parameter value for each device.

[First step of selecting the first route]
First, the route control device 30 performs route selection processing of the first step using the MIN-MAX algorithm. In the MIN-MAX algorithm parameter table 34F of FIG. 11, among the devices included in the set V-U, the cost C (10) = “∞ (infinity)” of the user accommodation device 10 is the largest, so that the user accommodation is performed. Device 10 is included in set U. Then, “10 → 10” is obtained as a route from the user accommodation device 10 that is the transmission source node to the user accommodation device 10 that is one of the route selection target nodes. At this time, the route with the smallest link cost maximum is the route from the user accommodation device 10 to the user accommodation device 10, but since the link is not included, it has not been determined substantially.

Subsequently, among the devices included in the set V-U, any device included in the set U, here the cost of the device adjacent to the user accommodating device 10 via the link, that is, the optimization parameter value, is expressed as MIN-MAX. Based on the algorithm, the cost is updated to the minimum value of the link on the route to the device. In this case, the cost C (20) of the relay device 20 adjacent to the user accommodating device 10 is “4” from the link 100 of the link cost table 34A of FIG. Further, the cost C (21) of the relay device 21 adjacent to the user accommodation device 10 is also “3” from the link 101.
The MIN-MAX algorithm parameter table 34F at this time takes the values shown in FIG.

[Second step of first route selection]
Next, the route control device 30 performs route selection processing of the second step using the MIN-MAX algorithm. First, in the MIN-MAX algorithm parameter table 34F of FIG. 12, among the devices included in the set VU, the cost C (20) = “4” of the relay device 20 is the largest, so the relay device 20 Included in U. Then, “10 → 20” is obtained as a route from the user accommodation device 10 that is the transmission source node to the relay device 20 that is one of the route selection target nodes, based on the route for which the cost C (20) is calculated.

Subsequently, among the devices included in the set V-U, the cost of the device adjacent to the arbitrary device included in the set U via the link is updated. Here, the cost C (11) of the user accommodation apparatus 11 adjacent to the relay apparatus 20 is the cost “2” of the link 103 and the cost C (20) = “4” of the relay apparatus 20 in the link cost table 34A of FIG. The minimum value is “2”. Further, the cost C (21) of the relay device 21 adjacent to the relay device 20 is the minimum value “1” between the cost “1” and the cost C (20) = “4” of the relay device 20 from the link 102. Since the cost C (21) = “3” of the route from the user accommodation device 10 to the relay device 21 required so far is larger, the cost C (21) = “3” remains.
The MIN-MAX algorithm parameter table 34F at this time takes the values shown in FIG.

[Third step of first route selection]
Next, the route control device 30 performs route selection processing at the third step using the MIN-MAX algorithm. First, in the MIN-MAX algorithm parameter table 34F in FIG. 13, among the devices included in the set VU, the cost C (21) = “3” of the relay device 21 is the largest. Included in U. Then, “10 → 21” is obtained as a route from the user accommodation device 10 that is the transmission source node to the relay device 21 that is one of the route selection target nodes, based on the route for which the cost C (21) is calculated.

Subsequently, among the devices included in the set V-U, the cost of the device adjacent to the arbitrary device included in the set U via the link is updated. Here, the cost C (11) of the user accommodation device 11 adjacent to the relay device 21 is the cost “3” of the link 104 in the link cost table 34A of FIG. 9 and the cost C (21) = “3” of the relay device 21. The minimum value is “3”. At this time, since the cost C (11) = “2” of the route from the relay device 20 to the user accommodation device 11 required so far is smaller, the route from the relay device 21 with the highest cost is selected. And updated to cost C (21) = “3”.
The MIN-MAX algorithm parameter table 34F at this time takes the values shown in FIG.

[Fourth step of first route selection]
Next, the route control device 30 performs route selection processing of the fourth step using the MIN-MAX algorithm. First, in the MIN-MAX algorithm parameter table 34F of FIG. 14, among the devices included in the set VU, the cost C (11) = “3” of the user accommodating device 11 is the largest, so the user accommodating device 11 Are included in set U. Then, “10 → 21 → 20” is obtained as a route from the user accommodation device 10 that is the transmission source node to the relay device 21 that is one of the route selection target nodes, based on the route for which the cost C (11) is calculated. .

As a result, the first route is selected as the route from the user accommodation device 10 that is the transmission source node to the desired user accommodation device 11 that is the destination node, and the first route in the route selection unit 32 is selected. The selection process ends (step 501).
The MIN-MAX algorithm parameter table 34F at this time takes the values shown in FIG.

Next, the route selection unit 32 stores the costs C (10), C (11), C (20), and C (21) of each node from the MIN-MAX algorithm parameter table 34F in FIG. Store in the optimization parameter table 34B (step 502). The optimization parameter table 34B at this time takes the values shown in FIG.
Further, the route from the transmission source node to each node obtained by the first route selection process from the MIN-MAX algorithm parameter table 34F of FIG. 15 is stored in the route stack 34C of the storage unit 34 (step 502). ). The path stack 34C at this point takes the values shown in FIG.

Subsequently, since the route selection unit 32 selects a second route different from the first route from the transmission source node to the destination node, the route selection unit 32 assigns links and nodes other than the links and nodes constituting the first route. Based on this, a new topology of the backbone network 200 is created.
First, referring to the route to the user accommodation apparatus 11 that is the destination node of the route stack 34C in FIG. 17, the links 101 and 104 used in the first route in the link availability table 34D of the storage unit 34 are displayed. Set to unusable (step 503). The link availability table 34D at this time takes the values shown in FIG.
In the node availability table 34E of the storage unit 34, the node used in the first path, that is, the relay device 21 is set to be unusable (step 503). The node availability table 34E at this point takes the values shown in FIG.

Then, the route selection unit 32 refers to the link availability table 34D and the node availability table 34E in the storage unit 34, and creates a new topology of the backbone network 200 composed of usable links and nodes. (Step 504).
FIG. 20 is an explanatory diagram showing the new topology created in step 504. Here, a new topology of the backbone network 200 that connects the user accommodation device 10 that is the transmission source node and the user accommodation device 11 that is the destination node is created from the links 100, 102, and 103 and the relay device 20.

Next, the route control device 30 confirms reachability from the user accommodation device 11 to the user accommodation device 10 using depth priority selection in the topology of FIG. 20 (step 505). That is, whether or not the user accommodation device 10 is connected by searching for the relay device connected via the link from the user accommodation device 11 that is the destination node and further following the link connected to the relay device. Check.
Specifically, in the topology of FIG. 20, the link 103 connected to the user accommodation device 11 is traced to the relay device 20, and the user accommodation device 10 is further connected from the link 100 connected to the relay device 20. That is confirmed.

  In this way, after confirming that the route from the transmission source node to the destination node exists on the topology of FIG. 20 (step 505: YES), the route selection unit 32 performs the optimization parameter table of the storage unit 34. The node having the maximum optimization parameter value, for example, the relay device 20 here is selected as a connection point for connecting the first half path and the second half path of the second path by sorting 34B by the optimization parameter value. Step 506). Note that the optimization parameter value of the user accommodation device 10 is given a value of “∞ (infinite)”, and is therefore excluded from the node selection candidates here.

Then, since the route selection unit 32 selects a second route different from the first route in the topology of FIG. 20, the route selection unit 32 selects the second route from the second route, that is, the user accommodation device 11 that is the destination node. A route selection process is performed for the route to the relay device 20 that is the connection point selected in (Step 507).
For this route selection process, the MIN-MAX algorithm (see, for example, Patent Document 1) is used, as in the route selection process related to the first route described above. At the start of processing of the MIN-MAX algorithm, each parameter is initialized. FIG. 22 shows the stored contents of the MIN-MAX algorithm parameter table 34F in the initial state.

[First step in selecting the second half of the route]
First, the path control device 30 performs a first-step path selection process using a MIN-MAX algorithm (see, for example, Patent Document 1). In the MIN-MAX algorithm parameter table 34F of FIG. 22, among the devices included in the set VU, the cost C (11) = “∞” of the user accommodation device 11 is the largest, so the user accommodation device 11 Included in U. Then, “11 → 11” is obtained as a route from the user accommodation device 11 to the user accommodation device 11 which is one of the route selection target nodes. At this time, the route with the smallest link cost maximum is the route from the user accommodation device 10 to the user accommodation device 10, but since the link is not included, it has not been determined substantially.

Subsequently, among the devices included in the set V-U, the cost of the arbitrary device included in the set U, here the user accommodation device 11 through the link, that is, the optimization parameter value, is expressed as MIN-MAX. Based on the algorithm, the link cost of the route to the device is set to the minimum value. In this case, the cost C (20) of the relay device 20 adjacent to the user accommodating device 11 is “2” from the link 103 of the link cost table 34A of FIG.
The MIN-MAX algorithm parameter table 34F at this time takes the values shown in FIG.

[Second step of selecting the second half route]
Next, the route control device 30 performs route selection processing of the second step using the MIN-MAX algorithm. First, in the MIN-MAX algorithm parameter table 34F of FIG. 23, among the devices included in the set VU, the cost C (20) = “2” of the relay device 20 is the largest, so the relay device 20 Included in U. Then, “11 → 20” is obtained as a route from the user accommodation device 11 that is the destination node to the relay device 20 that is one of the route selection target nodes, based on the route for which the cost C (20) is calculated.

As a result, the latter half route from the user accommodation device 11 that is the destination node to the desired relay device 20 that is the connection point is selected, and the selection processing of the latter half route in the route selection unit 32 ends (step 507). .
The MIN-MAX algorithm parameter table 34F at this time takes the values shown in FIG.

Subsequently, the route selection unit 32 sets “10 → 20” as the route from the user accommodation device 10 that is the transmission source node of the packet to the relay device 20 that is the connection point, constituting the second route. A selection is made from the path stack 34C (see FIG. 17) in the storage unit 34 (step 508).
Next, the latter half route “11 → 20” from the user accommodation device 11 to the relay device 20 stored in the MIN-MAX algorithm parameter table 34F (see FIG. 24) of the storage unit 34 and the above first half route “10 → 20”. ”Is selected as the second route, and the second route“ 10 → 20 → 11 ”is stored in the route stack 34C of the storage unit 34 (step 509). . The path stack 34C at this time takes the values shown in FIG.

Thereafter, the process returns to the above-described step 503 and refers to the route to the user accommodation apparatus 11 that is the destination node of the route stack 34C in FIG. 24, and the second route in the link availability table 34D of the storage unit 34. The links 100 and 103 used in the above are set to be unusable (step 503). The link availability table 34D at this point takes the values shown in FIG.
Further, the node used in the second route, that is, the relay device 20 in the node availability table 34E of the storage unit 34 is set to be unusable (step 503). The node availability table 34E at this point takes the values shown in FIG.

Then, the route selection unit 32 refers to the link availability table 34D and the node availability table 34E in the storage unit 34, and creates a new topology of the backbone network 200 composed of usable links and nodes. (Step 504).
FIG. 28 is an explanatory diagram showing the new topology created in step 504. Here, a new topology of the backbone network 200 that connects the user accommodation apparatus 10 that is the transmission source node and the user accommodation apparatus 11 that is the destination node is created from the link 102.

Next, the route control device 30 confirms reachability from the user accommodation device 11 to the user accommodation device 10 using depth priority selection in the topology of FIG. 28 (step 505). In this case, since there is no link connected to the user accommodation device 11 that is the destination node, it is determined that there is no reachability to the user accommodation device 10 (step 505: NO), and a series of route selection processing is terminated. .
As a result, in the route stack 34C of the storage unit 34, the first route “10 → 21 → 11” and the second route are routed from the user accommodation device 10 as the transmission source node to the user accommodation device 11 as the destination node. Two different routes of “10 → 20 → 11” are selected.

  As described above, in this embodiment, after selecting the first route from the transmission source node to the destination node, a topology excluding the route is created, and the transmission source node different from the first route to the destination node is created. As a second half route of the second route, a route between the relay node as the connection point and the destination node is selected, and the first half from the transmission source node already obtained in the selection process of the first route to the node as the connection point A route obtained by combining the route and the latter half route is selected as the second route.

  As a result, when the second route is selected, the calculation result of the first route that has already been selected can be reused, and the calculation processing load is reduced even when an individual traffic amount is used for each link as the link cost. It is possible to quickly select a plurality of routes between the same nodes.

  In addition, since the node of the connection point connecting the first half path and the second half path of the second path is selected, the node having the maximum optimization parameter value is selected from the nodes in the topology. Or a path with the performance next to the first path can be selected as the second path, and a path most suitable as a path to be used by switching to the first path can be selected.

  Further, the second route selected as a route different from the first route is not limited to one. For example, if there is a route connecting the source node and the destination node other than the second route, steps 503 to 509 in FIG. 8 are repeatedly executed, so a plurality of routes are selected as the second route. It is possible to select three or more different routes as a route connecting the transmission source node and the destination node.

  In the above description, the case where the MIN-MAX algorithm is used as the route selection algorithm has been described as an example. However, the present invention is not limited to this, and the next node is sequentially set using the optimization parameter value for evaluating the route. As long as the algorithm is selected, the present invention can be applied in the same manner as described above, and the same effects as described above can be obtained.

  Further, in the above, as shown in FIG. 6, as the MIN-MAX algorithm, the minimum value of the link cost among the links constituting an arbitrary route is set as the optimization parameter value of the route, and the optimization parameter of each route is set. Although the case where the route having the maximum value is selected as the optimum route has been described, the present invention is not limited to this. By reversing the size of the criteria, the maximum link cost among the links that make up an arbitrary route is the optimization parameter value for that route, and the route with the smallest optimization parameter value among each route is the optimal route. Even when the MIN-MAX algorithm to be selected is used, the present invention can be applied in the same manner as described above, and the same effects as described above can be obtained. At this time, the optimization parameter value is initialized to a predetermined maximum value in processing such as infinity “∞”. In addition, as for a node serving as a connection point connecting the first half path and the second half path of the second path, a node having the smallest optimization parameter value may be selected.

1 is a configuration example of a communication network to which a path control device according to an embodiment of the present invention is applied. It is a block diagram which shows the structure of the route control apparatus concerning one embodiment of this invention. It is a structural example of a link cost table. It is a structural example of an optimization parameter table. It is a structural example of a path | route stack. It is a structural example of a link availability table. It is a structural example of a node availability table. It is a flowchart which shows the route selection process in the route control apparatus concerning one embodiment of this invention. It is a structural example of a link cost table (initial state). It is explanatory drawing which shows the definition and description regarding a MIN-MAX algorithm. It is an example of stored contents (initial state) of the MIN-MAX algorithm parameter table. It is an example of stored contents of the MIN-MAX algorithm parameter table (first step of the first route). It is an example of stored contents of the MIN-MAX algorithm parameter table (second step of the first route). It is an example of stored contents of the MIN-MAX algorithm parameter table (third step of the first route). It is an example of stored contents of the MIN-MAX algorithm parameter table (fourth step of the first route). It is an example of stored contents of the optimization parameter table (at the time of first route determination). It is an example of stored contents of a path stack (at the time of first path determination). It is an example of stored contents of the link availability table (at the time of determining the first route). It is an example of stored contents of the node availability table (at the time of determining the first route). It is an example of topology creation (after the first route is determined). It is an example of stored contents of the optimization parameter table (initial state of the second path). It is an example of stored contents of the MIN-MAX algorithm parameter table (initial state of the second route). It is an example of stored contents of the MIN-MAX algorithm parameter table (first step of the second route). It is an example of stored contents of the MIN-MAX algorithm parameter table (second step of the second route). It is an example of stored contents of a path stack (at the time of determining a second path). It is an example of the stored contents of the link availability table (at the time of determining the second route). It is an example of stored contents of the node availability table (at the time of determining the second route). It is an example of topology creation (after the second route is determined).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,11 ... User accommodation apparatus (node), 20, 21 ... Relay apparatus (node), 30 ... Path control apparatus, 31 ... Link information collection part, 32 ... Path selection part, 33 ... Path control part, 34 ... Storage part , 34A ... link cost table, 34B ... optimization parameter table, 34C ... path stack, 34D ... link availability table, 34E ... node availability table, 34F ... MIN-MAX algorithm parameter table, 40, 41 ... user terminal , 100 to 104 ... link, 200 ... backbone network, 300 ... management network.

Claims (4)

The transmission source is provided in a packet communication network including a plurality of nodes connected in a network via a link, and sequentially selects a route from the transmission source node for performing packet communication to the next node from the network. A route control device that selects a route from a node to a desired destination node,
A link information collection unit that collects link information indicating the packet transfer status in each link from each node;
When selecting a route from a source node to an arbitrary node, a route selection that selects one of the routes to the node as a route to the node based on an optimization parameter value that evaluates the route to the node. And
A storage unit that stores link information collected by the link information collection unit, optimization parameter values of the node, and a route to each node selected by the route selection unit;
The route selection unit, when calculating the optimization parameter value of the node, calculates the optimization parameter value from the link information of each link constituting the route to the node stored in the storage unit,
When the route selection unit selects a second route different from the first route,
After first selecting a route from the source node to the destination node, create a new topology of the network from the links and nodes excluding the links and nodes constituting the first route,
Selecting a path from the destination node to any node in the topology from the topology as a second half path of the second path;
As the first half path of the second path, select the first half path from the transmission source node to any node in the topology from the storage unit,
A route control device, wherein a route obtained by combining the first half route and the second half route is selected as the second route. The route control device according to claim 1,
The route control device, wherein the route selection unit selects a node having a maximum optimization parameter value from the storage unit as the node that becomes a connection point between the first half route and the second half route. A route control device provided in a packet communication network composed of a plurality of nodes connected in a network via a link, and sequentially selecting a route from the transmission source node for performing packet communication to the next node from the network. A route selection method for selecting a route from the source node to a desired destination node,
A link information collecting step for collecting link information indicating a packet transfer status in each link from each of the nodes;
When selecting a route from a source node to an arbitrary node, a route selection that selects one of the routes to the node as a route to the node based on an optimization parameter value that evaluates the route to the node. Steps,
A storage step of storing in the storage unit the link information collected by the link information collection unit, the optimization parameter value of the node, and the route to each node selected by the route selection unit;
The route selection step calculates the optimization parameter value from the link information of each link constituting the route to the node stored in the storage unit when calculating the optimization parameter value of the node;
In the route selection step, when selecting a second route different from the first route,
First selecting a route from the source node to the destination node, then creating a new topology of the network from the links and nodes excluding the links and nodes that make up the first route;
Selecting from the topology a path from the destination node to any node in the topology as a second half path of the second path;
Selecting the first half path from the source node to any node in the topology as the first half path of the second path from the storage unit;
A route selection method comprising: selecting a route obtained by combining the first half route and the second half route as the second route. In the route selection method according to claim 3,
The route selection method, wherein the route selection step selects a node having a maximum optimization parameter value from the storage unit as the node that becomes a connection point between the first half route and the second half route.

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