JP2013026710A - Routing table set method in multi-area network, communication system and node - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a routing table set method, preventing the generation of a loop when a routing protocol is operated area-by-area in a multi-area network.SOLUTION: Under an environment in which a plurality of areas, which are subnetworks constituted by links for connecting among a plurality of nodes, exist, when one routing protocol unit, which is included in a node subordinate to the plurality of areas and shares one routing table associated with the entire plurality of areas, tries to set a first route entry to the routing table, when a second route entry to a certain destination node is already set in the routing table by another routing protocol unit, the one routing protocol unit sets the first route entry to the routing table if the route cost of the first route entry is smaller than the route cost of the second route entry.

Description

  The present invention relates to a routing table setting method, a communication system, and a node in a multi-area network, and in particular, a configuration in which a radio communication frequency assigned to each radio interface in each node is freely changed between nodes having a plurality of radio interfaces. The present invention relates to routing table setting in a cognitive radio network.

  In recent years, expectations for the realization of cognitive radio networks are increasing. Here, the cognitive radio network refers to one or more channels from among a plurality of available radio communication frequencies (hereinafter, referred to as “channels” where appropriate) in each node existing in the network. By selecting appropriately based on (unused channel, distance between nodes, communication demand, etc.), a network adapted to the surrounding environment is configured.

  In a cognitive radio network, when any two nodes assigned the same channel are within the propagation distance range, a link is created between the two nodes. Therefore, the links created by the channels assigned to each node and the overall topology are different. In addition, since the characteristics such as propagation distance, capacity, and loss rate are different for each channel, the main feature is that the provisioning of the network can be freely changed by changing the channel assigned to each node as necessary.

  For example, it is possible to create a link or path having a larger capacity between nodes where there is a large communication demand. Specifically, a channel having as much capacity as possible is assigned to a node on the link or the route, or a channel is assigned so that a disjoint route can be created as much as possible for a backup route in the event of a failure. A network configuration with a high degree of freedom is possible.

  Here, in order to further explain the cognitive radio network, a node model and a network configuration example are shown in FIG.

  Referring to FIG. 1, the cognitive radio network in this configuration example includes seven nodes (nodes A to G).

  Further, the node model of this configuration example is characterized in that the node body has a plurality of wireless interfaces. Specifically, each node has two wireless interfaces, a first wireless interface and a second wireless interface.

  In addition, an area (subnetwork) is configured by nodes that share the same channel and are connected to each other via a link created by the shared channel. In this configuration example, four areas (areas X, Y, W, and Z) are configured by eleven links (L11 to L42).

  For example, in area X, the same channel is assigned to the second wireless interface of node A and the second wireless interface of node B. A link L11 formed by the channel connects the node A and the node B.

  In area Y, the same channel is assigned to the first wireless interface of node A, the first wireless interface of node B, and the first wireless interface of node C. Nodes A to C are connected to each other by links L21 to L23 formed by the channel.

  Similarly, in area Z, the same channel is allocated to the second wireless interface of node C and the first wireless interfaces of nodes G, D, E, and F. The links L31 to L34 created by the channel connect the nodes C to F.

  Further, in the area W, the same channel is allocated to the second radio interfaces of the nodes D, E, and G. The links L41 and L42 created by the channel connect the nodes D, E, and G.

  As described above, in a cognitive radio network, an area is defined by nodes that share the same channel and are connected to each other via a link created by the shared channel. A cognitive radio network is realized by the plurality of defined areas. In addition, since a plurality of channels are allocated to one node, there is a feature that one node can belong to a plurality of areas. In this configuration example, for example, node A belongs to both area Y and area X.

  Such cognitive radio networks are disclosed in Patent Documents 1, 2, and 3, for example.

  Specifically, Japanese Patent Application Laid-Open No. H10-228707 describes that frequency use efficiency is improved by using communication bands of a plurality of wireless systems having different characteristics.

  Patent Document 2 describes a technique for selecting a communication route that minimizes the total cost of all pasts, and Patent Document 3 describes a technique for performing appropriate routing.

  As one method for performing routing in a network composed of a plurality of areas as described in each patent document, a method of exchanging link state information in each area can be considered. Here, the link state information is information relating to a link connecting between adjacent nodes in each node.

  As a routing protocol for exchanging link state information, there is OLSR (Optimized Link State Routing) disclosed in Non-Patent Document 1. In OLSR, link state information can be exchanged by a technique called flooding that distributes the same packet from one node to all nodes. However, when the entire network is large, there is a problem that exchanging link state information among all nodes of the network causes a high load and poor scalability.

  Therefore, in order to reduce the number of nodes exchanging link state information, it is conceivable to stop an area for exchanging link state information within the area. However, this does not ensure reachability between different areas. Therefore, a node existing at an area boundary advertises to each area the cost of a route to a node existing in a different area (the sum of the link costs of links on the route) and the corresponding area boundary node information. Ensure reachability between areas. This is the same idea as the inter-area routing in OSPF (Open Shortest Path First) disclosed in Non-Patent Document 2.

  An example in which reachability between areas is ensured by a node existing at an area boundary based on this idea by advertising the route cost to a node existing in a different area and the corresponding area boundary node information to each area. Is shown in FIG.

  In FIG. 2, for convenience of explanation, it is assumed that the area X and the area W are omitted compared to the configuration example of the network of FIG.

  At this time, the node C existing at the area boundary is a route cost to the nodes D, E, F, and G, which are nodes existing in an area different from the area Y, and the corresponding area boundary node. (Node C) is advertised. At the same time, the node C advertises the route cost to the nodes A and B, which are nodes in an area different from the area Z, and the corresponding area boundary node (node C) to the node toward the area Z side. Each node in the areas Y and Z is different by adding the route cost to the node existing in the advertised different area and the route cost to the area boundary node (node C) that advertised the route cost. It is possible to calculate a minimum cost route to a node existing in the area.

JP 2007-306206 A JP 2008-131574 A JP 2008-227740 A

T. Clausen and P. Jacquet, "Optimized Link State Routing Protocol (OLSR)," RFC 3626, October 2003. J. Moy, "OSPF Version 2," RFC 2328, April 1998.

  By using the technique as described above, reachability between areas can be ensured. However, since the above technique has a problem, this point will be described.

  In a cognitive radio network, when exchanging link state information within each area, a plurality of routing protocols may operate within the same node. This is because an area is defined by nodes that share the same channel and are connected to each other via a link created by the shared channel, so a node to which multiple channels are assigned can belong to multiple areas. .

  In an OS (Operating System) generally used recently, only one routing table can be set in each node in many cases. If only one routing table can be set in each node, a packet loop may occur when a plurality of routing protocols operate in the same node.

An example in which a packet loop occurs when a plurality of routing protocols operate in the same node will be described with reference to FIG. For convenience of explanation, it is assumed that the network configuration shown in FIG. 3 has a configuration in which the area X and the area Y are omitted as compared with the network configuration example of FIG.

  The link cost table 501 shows the link cost of each link in the area Z. The link cost table 502 shows the link cost of each link in the area W.

  This link cost may be determined by setting in advance, or may be calculated based on link capacity, link delay time, and the like. In the examples of the link cost tables 501 and 502, it is assumed that only the link L35 has a link cost = 4 and the other links have a link cost = 1.

  The routing protocol calculates the least cost path. Therefore, the route entries calculated by the routing protocol in area Z are as shown in routing table 503 at node D and routing table 504 at node E.

  Further, the route entries calculated by the routing protocol in the area Z are the routing table 505 in the node D and the routing table 506 in the node E. In this description, route entries to nodes outside the area are omitted.

  Here, it is assumed that the routing table 503 is set as an effective routing table in the node D, and the routing table 506 is set as an effective routing table in the node E. However, an entry in the routing table 504 is set as a route entry to the nodes C and F which are nodes not included in the area W.

  In this case, the packet destined for the node G loops between the node D and the node E.

  When the routing protocol is operated for each area in the cognitive radio network as in the above example, there is a problem that a loop may occur when a plurality of routing protocols are operating.

Therefore, the present invention
To provide a routing table setting method, a communication system, and a node in a multi-area network that does not generate a loop even when a plurality of routing protocols are operating when operating a routing protocol for each area in a cognitive radio network. Objective.

  According to the first aspect of the present invention, in an environment where there are a plurality of areas that are sub-networks configured by links connecting a plurality of nodes, the plurality of areas belong to the plurality of areas, and all the plurality of areas are included. In a routing table setting method performed by a node sharing one routing table, the node includes a plurality of routing protocol units corresponding to the areas to which the node belongs, and any one of the routing protocol units is a destination node. If the second route entry for the certain destination node is already set in the routing table by another routing protocol unit when trying to set the first route entry for The first route than the route cost of the second route entry Routing table setting method characterized by long as the smaller of the path cost of entry to the first route entry is set to the routing table is provided.

  According to the second aspect of the present invention, in an environment where there are a plurality of areas that are sub-networks configured by links connecting a plurality of nodes, the plurality of areas belong to the plurality of areas, and all of the plurality of areas are included. In the routing table setting method performed by a node sharing one routing table, the node corresponds to each of the areas to which the node belongs, and includes a plurality of routing protocol units each assigned an individual identification number, When the one routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. If it is set by the routing protocol part, There is provided a routing table setting method for determining whether to set the first route entry based on the magnitude relationship between the identification number of the routing protocol part and the identification number of the second routing protocol part. The

  According to a third aspect of the present invention, there is provided a subnetwork configured by links connecting a plurality of nodes, and in an environment where a plurality of areas each assigned with an individual identification number exist, In a routing table setting method performed by a node belonging to an area and sharing one routing table for all of the plurality of areas, the node includes a plurality of routing protocol units corresponding to each of the belonging areas. When the routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. If it is set by the routing protocol part, the first It is determined whether to set the first route entry based on the magnitude relationship between the identification number of the area corresponding to the routing protocol part and the identification number of the area corresponding to the second routing protocol part. A routing table setting method is provided.

  According to the fourth aspect of the present invention, in an environment in which there are a plurality of areas that are sub-networks configured by links connecting a plurality of nodes, each of the plurality of areas belongs to the plurality of areas. A node sharing one routing table includes a plurality of routing protocol units corresponding to each of the areas to which the node belongs, and any one of the routing protocol units assigns a first route entry for a certain destination node to the routing table. When a second route entry for the certain destination node has already been set in the routing table by another routing protocol unit, the route cost of the second route entry is more than the route cost of the second route entry. If the route cost of the first route entry is smaller, the first Node and sets a route entry of the routing table is provided.

  According to the fifth aspect of the present invention, in an environment in which there are a plurality of areas that are sub-networks configured by links connecting a plurality of nodes, each of the plurality of areas belongs to the plurality of areas. On the other hand, a node sharing one routing table corresponds to each of the areas to which the node belongs, and includes a plurality of routing protocol units each assigned with an individual identification number. When attempting to set the first route entry for the destination node in the routing table, the second route entry for the certain destination node has already been set in the routing table by the second routing protocol unit Is the identification number of the first routing protocol part and the second rule Node, characterized in that on the basis of the magnitude relationship between computing protocol unit identification number to determine whether to set the first path entry is provided.

  According to a sixth aspect of the present invention, there is provided a subnetwork configured by links connecting a plurality of nodes, and in an environment where there are a plurality of areas each assigned with an individual identification number, In a node belonging to an area and sharing one routing table for all of the plurality of areas, the node includes a plurality of routing protocol units corresponding to each of the belonging areas, and the first routing protocol unit includes a certain destination When attempting to set a first route entry for a node in the routing table, if a second route entry for the certain destination node has already been set in the routing table by the second routing protocol unit And identification of the area corresponding to the first routing protocol part Node to issue and wherein determining whether to set the first route entry based on the magnitude relationship between the identification number of the area corresponding to the second routing protocol unit is provided.

  According to a seventh aspect of the present invention, there is provided a subnetwork configured by links connecting a plurality of nodes, and in an environment where a plurality of areas each assigned with an individual identification number are present, In a communication system comprising a plurality of nodes belonging to an area and sharing one routing table for all the plurality of areas, the node is provided according to any one of the fourth to sixth aspects of the present invention. A communication system characterized by being a node is provided.

  According to the present invention, when setting a route entry for a certain destination node, since the route entry is set in the routing table only when a predetermined policy is satisfied, when there is only one routing table, Even if a plurality of routing protocol units try to set route entries for the same destination node, setting of route entries that cause a loop can be prevented.

It is a figure showing an example of the basic composition of a cognitive radio network. It is a figure for demonstrating the advertisement and calculation of a route between areas. It is a figure showing an example of the basic composition of the cognitive radio network where a plurality of routing protocols operate. 1 is a block diagram showing a basic configuration of a first exemplary embodiment of the present invention. It is a figure showing the example of the link state database in embodiment of this invention. It is a figure showing the example of the routing table in the 1st Embodiment of this invention. It is a flowchart (1/2) which shows operation | movement of the node 1000 in embodiment of this invention. It is a flowchart (2/2) which shows operation | movement of the node 1000 in embodiment of this invention. It is a figure showing another example of the link state database in embodiment of this invention. It is a block diagram showing the basic composition of the 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the node 2000 in embodiment of this invention. It is a figure showing the example of the routing table in the 2nd Embodiment of this invention. It is a figure showing another example of the routing table in the 2nd Embodiment of this invention.

[Embodiment 1]
Next, a first embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 4 shows a node 1000 according to the first embodiment of the present invention. The node 1000 is one of the nodes included in the cognitive radio network, and is connected to other nodes by radio links. The overall configuration of the cognitive radio network in the present embodiment is the same as the network configuration example of FIG. It is assumed that other nodes connected to the node 1000 have the same configuration as the node 1000. That is, the present embodiment is established even when the node 1000 is used alone, but also as a cognitive radio network including a plurality of nodes including the node 1000.

  Referring to FIG. 4, the node 1000 includes a routing protocol group 100, a minimum path cost entry determination unit 200, and a routing table 300.

  The routing protocol group 100 includes a plurality of routing protocol units corresponding to each area to which the node 1000 belongs. In the configuration example of FIG. 4, it is assumed that the node 1000 belongs to N areas. Therefore, the routing protocol group 100 includes N routings of the first area routing protocol unit 110-1, the second area routing protocol unit 110-2,..., And the Nth area routing protocol unit 110-N. Includes protocol part. In FIG. 4, only three routing protocol parts are shown, but this is for the convenience of illustration only. In practice, as many routing protocols as there are areas to which the node belongs are included. That is, in FIG. 4, the third area routing protocol unit 110-3,..., And the (N-1) th area routing protocol unit 110-N-1 are not shown. Note that there may be only two routing protocol units depending on the connection status.

  The first area routing protocol unit 110-1, the second area routing protocol unit 110-2,..., And the Nth area routing protocol unit 110-N all have the same configuration. Therefore, the first area routing protocol unit 110-1 will be described on behalf of each routing protocol unit. As described above, the Nth area routing protocol unit 110-N has the same configuration as that of the first area routing protocol unit 110-1, but each unit in the Nth area routing protocol unit 110-N. The illustration of is omitted.

  The first area routing protocol unit 110-1 includes a link state information exchange unit 111-1, a link state database 112-1, a route calculation unit 113-1, and a route setting unit 114-1.

  Link state information exchanging section 111-1 exchanges link state information in the area with adjacent nodes belonging to the same area. Here, the link state information is information relating to a link connecting between adjacent nodes in each node. Examples of the information regarding the link include information for identifying a node that advertises link state information, information for identifying an adjacent node corresponding to each link, link cost, and the like. Examples of protocols for exchanging link state information include OLSR and OSPF. These are merely examples, and other information may be further used or may be based on other protocols. Further, the exchange of link state information may be triggered by notification from an adjacent node, or may inquire of an adjacent node periodically.

  The link state database 112-1 is a database having a function of storing link state information in each area exchanged by the link state information exchange unit 111-1.

  An example of link state information stored in the link state database 112-1 is shown in FIG. The link state database 507 in FIG. 5 is an example of the link state information of the area Z stored in the nodes C to G in FIG. The link state database 508 is an example of link state information of the area W stored in the nodes D, E, and G in FIG. For example, referring to the link state database 507, the adjacent node and link cost corresponding to each link are registered for each node that advertises link state information. For example, it can be seen that node C has a link to node D, and the link cost of the link is 1. Further, the node D has links to the nodes C, E, and G, and it can be seen that the link costs of the links are 1, 1, and 4, respectively.

  The route calculation unit 113-1 refers to the link state information stored in the link state database 112-1, and is the minimum cost route to each destination node in the area to which the first area routing protocol unit 110-1 belongs. Calculate An example of an algorithm for calculating a minimum cost path is an algorithm called Dijkstra's Algorithm. The route calculation may be performed periodically or when the link state database 112-1 is updated.

  The route setting unit 114-1 uses the next hop node corresponding to the route to each node calculated by the route calculation unit 113-1, the route cost, and the identifier of the routing protocol unit in which the route entry is set as the route entry, as a routing table 300. It has a function to set to.

  The route setting unit 114-1 makes an inquiry to the minimum route cost entry determination unit 200 before setting a route entry in the routing table 300, and the route entry to be set is set by another routing protocol unit in the node 1000. Compared with the route entry to the same destination node set to 300, it is checked whether it has the minimum route cost.

  In response to an inquiry from the route setting unit 114-1 to the route setting unit 114 -N, the minimum route cost entry determination unit 200 determines that the route entry to be set by the route setting unit 114-1 to the route setting unit 114 -N is a node. Compared with the route entry to the same destination node set in the routing table 300 by another routing protocol unit in 1000, it is determined whether or not the route protocol has the minimum route cost. Then, the determination result is returned to the inquiry route setting unit 114 (any one of the route setting unit 114-1 to the route setting unit 114-N).

  As a specific determination method, it is checked whether or not a route for the same destination node as the destination node of the route entry to be set by the route setting unit 114 that is the current inquiry is already set in the routing table 300. If not set, it is determined that the route entry to be set by the route setting unit 114 as the inquiry source this time is a route having the minimum route cost to the destination node. If there is an entry that has already been set, the set entry is referred to and the identifier of the routing protocol part that set the entry is checked. When the identifier matches the identifier of the routing protocol unit including the route setting unit 114 of the current inquiry, the route entry to be set by the route setting unit 114 of the current inquiry is the minimum route cost to the destination node. It is determined that the route has If they do not match, the route cost of the already set entry is compared with the route cost of the route entry to be set by the route setting unit 114 that is the current inquiry. As a result of the comparison, if the route cost of the route entry to be set by the current route setting unit 114 is smaller, the route entry to be set by the current route setting unit 114 is It is determined that the route has the minimum route cost to the destination node.

  The routing table 300 is a table in which entries for the next hop node, the route cost to the destination node, and the identifier of the set routing protocol unit are registered for each destination node. The route setting unit 114-1 to the route setting unit 114 are registered. Set by -N. An example of a route entry set in the routing table 300 is shown in the routing table 509 of FIG.

  Referring to FIG. 6, a routing table 509 shows a routing table set in the node D in FIG. 3. For each destination node, the next hop node of the corresponding route, the route cost to the destination node and the setting The entry of the identifier of the routing protocol part is registered.

  For example, in the first entry, it can be seen that the next hop node of the route having the node C as the destination node is the node C, the route cost is 1, and the routing protocol unit in which the entry is set is the routing protocol unit 110-1. Similarly, in the second entry, the next hop node of the route having the node E as the destination node is the node E, the route cost is 1, and the routing protocol unit in which the entry is set is the routing protocol unit 110-2. I understand. In the third entry, it can be seen that the next hop node of the route having the node F as the destination node is the node E, the route cost is 2, and the routing protocol unit in which the entry is set is the routing protocol unit 110-1. In the fourth entry, it can be seen that the next hop node of the route having the node G as the destination node is the node G, the route cost is 1, and the routing protocol unit in which the entry is set is the routing protocol unit 110-2.

  Next, referring to FIG. 7, in this embodiment, link state information exchanging section 111-1, link state information exchanging section 111-2, link state information exchanging section 111-N and link state database 112- 1. The operation when creating a link state table by the link state database 112-2 and the link state database 112-N will be described in detail. This time, the link state information exchanging unit 111-1 and the link state database 112-1 will be described as an example, but the other link state information exchanging unit and link state database perform the same operation.

  First, the link state information exchanging unit 111-1 exchanges link state information in the area with an adjacent node belonging to the same area (step S601).

  Subsequently, the link state database 112-1 stores the link state information acquired by the link state information exchanging unit 111-1 in step S601 as a link state table (step S602).

  By performing the above operation for each adjacent node, a database such as the link state database 507 and the link state database 508 shown in FIG. 5 is created.

  Next, with reference to FIG. 8, the operation in which the route setting units 114-1 and 114-2 and the route setting unit 114-N of the node 1000 set the routing table 300 in the present embodiment will be described in detail.

  First, the route calculation unit 113-1 in the first area routing protocol unit 110-1 in the routing protocol group 100 refers to the link state database 112-1, and the first area routing protocol unit 110-1 belongs to it. The minimum cost route to each destination node in the area is calculated (step S611 in FIG. 8).

  Next, the route setting unit 114-1 sets the next hop node corresponding to the route to each node calculated by the route calculation unit 113-1 in step S611, the route cost, and the identifier of the routing protocol unit that sets the route entry. The route entry is sent to the minimum route cost entry determination unit 200. As a result, it is inquired whether the route entry has a minimum route cost as compared with the route entry to the same destination node set in the routing table 300 by another routing protocol unit in the node 1000. In response to the inquiry from the route setting unit 114-1, the minimum route cost entry determination unit 200 has already set an entry in the routing table 300 for the same destination node as the route entry to be set by the route setting unit 114-1. It is investigated whether or not (steps S612 and S613).

  If not set (No in step S613), the route entry to be set by the route setting unit 114-1 is determined to be a route having the minimum route cost to the destination node, and the process proceeds to step S618. To do.

  On the other hand, if there is an entry that has already been set (Yes in step S613), the set entry is referred to and the identifier of the routing protocol part that set the entry is checked (steps S614 and S615).

  If the identifier matches the identifier of the routing protocol unit 110-1 including the route setting unit 114-1 (Yes in step S615), the route entry to be set by the route setting unit 114-1 is a link to the destination node. It determines with it being a path | route with the minimum path | route cost, and transfers to step S618.

  On the other hand, if the identifier does not match the identifier of the routing protocol unit including the route setting unit 114-1 (No in step S615), the route setting unit 114-1 tries to set the route cost of the entry that has already been set. The route cost of the route entry to be compared is compared (steps S616 and S617).

  As a result of the comparison, if the route cost of the route entry to be set by the route setting unit 114-1 is smaller (Yes in step S617), the route entry to be set by the route setting unit 114-1 is the destination node. It determines with it being a path | route with the minimum path | route cost to, and transfers to step S618. On the contrary, if the route cost of the route entry to be set by the route setting unit 114-1 is not smaller (No in step S617), the route setting unit 114-1 operates without setting the route entry. finish.

  When the minimum route cost entry determination unit 200 determines that the route entry to be set by the route setting unit 114-1 has the minimum route cost, the route setting unit 114-1 calculates in step S611. A route entry is set in the routing table 300 (step S618).

  Here, a specific example of the operations of the above steps S611 to S618 will be described assuming that the node 1000 is at the position of the node D in FIG. In addition, in this explanation, the first area routing protocol unit 110-1 exchanges link state information of area Z, and the second area routing protocol unit 110-2 exchanges link state information of area W. Will be described as calculating and setting a route.

  First, when the link cost of each link in the area Z is the one shown in the link cost table 501 of FIG. 3, the link state information stored in the link state database 112-1 is the link state database 507 of FIG. Thus, the route to each destination node calculated by the route calculation unit 113-1 in step S611 is as shown in the routing table 503 in FIG.

  Further, when the link cost of each link in the area W is the one shown in the link cost table 502 of FIG. 3, the link state information stored in the link state database 112-2 is the link state database 508 of FIG. Thus, the route to each destination node calculated by the route calculation unit 113-2 in step S611 is as shown in the routing table 505 in FIG.

  As an example of the operation after step S612, it is assumed that a route entry corresponding to the area W is set. Specifically, it is assumed that the route setting unit 114-2 attempts to set a route entry having the node G as a destination node. Assume that the state of the routing table 300 before starting step S612 is that shown in the routing table 510 shown in FIG.

  First, in step S612, the minimum cost entry determination unit 200 checks whether an entry having the node G as a destination node is set in the routing table 300. In this example, since a route entry having the node G as the destination node is set, the result is No in step S613, and the process proceeds to step S614.

  Next, in step S614, the minimum cost entry determining unit 200 refers to the routing table 510, so that the routing protocol unit in which the route entry having the node G as the destination node is set is the routing protocol unit 110-1. . This is different from the identifier of the routing protocol unit 110-2 which is now trying to set a route entry to the node G. Therefore, it becomes No in step S615 and moves to step S616.

  In step S616, the minimum cost entry determination unit 200 determines 1 as the route cost of the route entry to the node G to be set by the route setting unit 114-2 and the route cost of the route entry to the node G in the routing table 510. 3 is compared. As a result of the comparison, since the route cost of the route entry to the node G to be set by the route setting unit 114-2 is smaller, No is determined in step S617 and the process proceeds to step S618.

  In step S618, the route setting unit 114-2 sets the route to the node G in the routing table 300 by overwriting it. As a result, the routing table 300 becomes like the routing table 509 shown in FIG.

  In the above description of the present embodiment, the routing protocol group 100 has been described on the assumption that a link state type routing protocol such as OLSR operates, but in addition, an AODV (Ad hoc On-Demand Distance Vector) is used. Even if any routing protocol other than the link state type is used, it can be similarly implemented.

  Next, the effect of this embodiment will be described.

In this embodiment, when trying to set a route entry for a destination node with a route setting unit,
1. 1. The route entry for the destination node has not been set in the routing table. 2. A route entry for the destination node has already been set in the routing table, and this entry is set by the same routing protocol portion as the routing protocol portion having the entry as a setting certificate. A route entry for the destination node is already set in the routing table, and the entry is set by a routing protocol portion that is different from the routing protocol portion for which the current entry is set as a certificate. If the route cost of the route entry to be set is smaller than the route cost, if either of the conditions is met, the route entry is set in the routing table.

  In this way, even if there is only one routing table for each node, even if a plurality of routing protocol units try to set route entries for the same destination node, the "same destination node" The route setting is performed with a consistent policy that “the route entry having the minimum route cost is preferentially set. Therefore, it becomes possible to prevent setting of a route entry that causes a loop as in a general technique.

[Embodiment 2]
Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

  Referring to FIG. 10, the second embodiment of the present invention is configured by a node 2000. The node 2000 is a node in the cognitive radio network, and is connected to other nodes via a radio link, like the node 1000 in the first embodiment of the present invention. The overall configuration of the cognitive radio network in the present embodiment is the same as the network configuration example of FIG. It is assumed that all or some of the other nodes connected to the node 2000 have the same configuration as the node 2000. In other words, the present embodiment is established even with the node 2000 alone, but is also established as a cognitive radio network including a plurality of nodes including the node 2000.

  Referring to FIG. 10, the node 2000 includes a routing protocol group 100, a route setting availability determination unit 400, and a routing table 300. The routing protocol group 100 includes a plurality of routing protocol units corresponding to each area to which the node 2000 belongs.

  The plurality of routing protocol units all have the same configuration. Therefore, the first area routing protocol unit 110-1 will be described on behalf of each routing protocol unit. Further, the illustration of each part regarding the Nth area routing protocol part 110-N is omitted.

  The first area routing protocol unit 110-1 includes a link state information exchange unit 111-1, a link state database 112-1, a route calculation unit 113-1, and a route setting unit 114-1.

  Among these units included in the routing protocol unit 110-1, the link state information exchange unit 111-1, the link state database 112-1, the route calculation unit 113-1, and the routing table 300 are the same as those in the first embodiment. It is assumed that the components and the routing table 300 described with the reference numerals have the same configurations and functions. Therefore, among the units included in the routing protocol unit 110-1, the description of the link state information exchange unit 111-1, the link state database 112-1, the route calculation unit 113-1, and the routing table 300 will be omitted.

  On the other hand, in the node 2000 of the present embodiment, the route setting unit 114-1, the route setting unit 114-2, and the route setting unit 114-N included in the node 1000 in the first embodiment are respectively replaced with the route setting unit 115. -1, the route setting unit 115-2 and the route setting unit 115-N. Furthermore, in the node 2000 of this embodiment, the minimum path cost entry determination unit 200 included in the node 1000 in the first embodiment is replaced with a path setting availability determination unit 400. Each of these replaced parts will be described in detail below.

  Compared with the route setting unit 114-1 in the first embodiment, the route setting unit 115-1 determines whether or not a route can be set instead of making an inquiry to the minimum route cost entry determining unit 200 before setting a route entry. The difference is that the part 400 is inquired to check whether the route entry to be set can be set.

  In response to an inquiry as to whether or not the route entry to be set by the route setting unit 115-1 may be set, the route setting availability determination unit 400 determines the route setting unit 115-1 based on a preset policy. Determines whether or not the route entry to be set can be set. Then, a response as to whether or not the setting may be made is made to the route setting unit 115-1.

As an example of a preset policy,
1. 1. The route entry can be overwritten only when the identifier value of the routing protocol part to be set is smaller (or larger) than the identifier of the routing protocol part in which the existing route entry is set. Only when the identifier value of the area corresponding to the routing protocol part to be set is smaller (or larger) than the identifier of the area corresponding to the routing protocol part in which the existing route entry is set, the route entry Can be overwritten.

  These policies need to be used at each node in the network. If another policy is used in a different node, there is a possibility that a route entry that causes a loop is set as in the general technique.

  In the following, an example is described in which the route setting availability determination unit 400 uses the above one policy (the route entry can be overwritten only when the identifier value of the routing protocol unit to be set is smaller). Will be described.

  The link state information exchange unit 111-1, the link state information exchange unit 111-2, the link state information exchange unit 111-N, the link state database 112-1, the link state database 112-2, and the link of the node 2000 in this embodiment. The operation when creating the link state table by the state database 112-N is the same as the operation described above with reference to FIG.

  Next, with reference to FIG. 11, the operation in which the route setting units 115-1 and 115-2 and the route setting unit 115-N of the node 2000 set the routing table 300 in the present embodiment will be described in detail.

  The operations in steps S621 to S625 in FIG. 11 are the same as the operations in steps S611 to S615 in FIG.

  In step S625, if the identifier does not match the identifier of the routing protocol unit including the route setting unit 115-1, the identifier of the routing protocol unit that has already set the entry and the route from which the route entry is to be set are set. The value of the identifier of the routing protocol part corresponding to the setting part 115-1 is compared (steps S626 and S627).

  As a result of the comparison, if the value of the identifier of the routing protocol unit corresponding to the route setting unit 115-1 is smaller (Yes in step S627), the process proceeds to step S628. On the other hand, if the value of the identifier of the routing protocol unit corresponding to the route setting unit 115-1 is not smaller (No in step S627), the route setting unit 115-1 operates without setting the route entry. finish.

  When the route setting availability determination unit 400 determines that the route entry to be set by the route setting unit 115-1 may be set, the route setting unit 115-1 displays the route entry calculated in step S621 in the routing table. 300 is set (step S628).

  Here, a specific example of the operation of the above steps S621 to S628 will be described assuming that the node 2000 is at the position of the node D in FIG. In addition, in this explanation, the first area routing protocol unit 110-1 exchanges link state information of area Z, and the second area routing protocol unit 110-2 exchanges link state information of area W. Will be described as calculating and setting a route.

  First, when the link cost of each link in the area Z is the one shown in the link cost table 501 of FIG. 3, the link state information stored in the link state database 112-1 is the link state database 507 of FIG. Thus, the route to each destination node calculated by the route calculation unit 113-1 in step S621 is as shown in the routing table 503 in FIG.

  Further, when the link cost of each link in the area W is the one shown in the link cost table 502 of FIG. 3, the link state information stored in the link state database 112-2 is the link state database 508 of FIG. Thus, the route to each destination node calculated by the route calculation unit 113-2 in step S621 is as shown in the routing table 505 in FIG.

  As an example of operations after step S622, a case where a route entry corresponding to area Z is set is assumed. Specifically, it is assumed that the route setting unit 115-1 attempts to set a route entry having the node G as a destination node. It is assumed that the state of the routing table 300 before starting step S622 is that shown in the routing table 511 shown in FIG.

  The operations in steps S622 to S625 are the same as the operation example described in the first embodiment, and a description thereof will be omitted.

  In step S626, the route setting availability determination unit 400 sets the routing protocol unit identifier 110-1 that is an identifier of the routing protocol unit corresponding to the route setting unit 115-1 and the routing protocol unit that sets the route entry to the node G in the routing table 403. Compare the values of the identifier 110-2. As a result of the comparison, since the value of 110-1 which is the identifier of the routing protocol unit corresponding to the route setting unit 115-1 is smaller, the process proceeds from step S627 to step S628.

  In step S628, the route setting unit 115-1 sets the route to the node G in the routing table 300 by overwriting it. As a result, the routing table 300 becomes like the routing table 512 shown in FIG.

  Next, the effect of this embodiment will be described.

In this embodiment, when trying to set a route entry for a destination node with a route setting unit,
1. 1. The route entry for the destination node has not been set in the routing table. 2. The route entry for the destination node is already set in the routing table, but the entry is set by the same routing protocol unit. A route entry for the destination node has already been set in the routing table, and the entry is set by a different routing protocol part. If any of the identifier values of the routing protocol part to which an entry is to be set is smaller, the route entry is set in the routing table.

  In this way, even if there is only one routing table for each node, even if a plurality of routing protocol units try to set route entries for the same destination node, the "same destination node" Is set with a consistent policy that the routing protocol part having the smallest identifier value sets the route entry preferentially. Therefore, it becomes possible to prevent setting of a route entry that causes a loop as in a general technique.

  The embodiment of the present invention described above prevents setting of a route entry that causes a loop even if a plurality of routing protocol units try to set a route entry for the same destination node when there is only one routing table. There is an effect that becomes possible.

  The first reason is that when the route setting unit tries to set a route entry for a certain destination node, the route cost of the route entry to be set is smaller than the route cost of the already set route entry. This is because only in this case, by setting the route entry in the routing table, only the route entry of the least cost route in all areas is set as effective.

  The second reason is that, when trying to set a route entry for a destination node with a route setting unit, the route entry will be set from now on rather than the identifier of the routing protocol unit that has already set the route entry. This is because only when the identifier value of the routing protocol part is smaller, by setting the route entry in the routing table, all nodes in the network set the route entry with a consistent policy.

  In the above embodiment, the description has been given assuming that the program for realizing the node of the present embodiment is incorporated in each node in advance. However, a program for causing a computer to operate as all or part of the nodes of the present embodiment or to execute the above-described processing is stored in a flexible disk, a CD-ROM (Compact Disc Read-Only Memory), a DVD (Digital Versatile Disc), MO (Magneto Optical Disk (Disc)), BD (Blu-ray Disc), etc., stored and distributed on a computer-readable recording medium, installed on another computer, and operated as the above-mentioned means Alternatively, the above-described steps may be executed.

  Furthermore, the program may be stored in a disk device or the like included in a server device on the Internet, and the program may be executed by, for example, superimposing the program on a carrier wave and downloading it to a computer.

  In addition, the routing table setting method according to the embodiment of the present invention can be realized by hardware, but the computer reads a program for causing the computer to execute the method from a computer-readable recording medium and executes the program. Can also be realized.

  Moreover, although the above-described embodiment is a preferred embodiment of the present invention, the scope of the present invention is not limited only to the above-described embodiment, and various modifications are made without departing from the gist of the present invention. Implementation in the form is possible.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Supplementary note 1) In an environment where there are a plurality of areas that are sub-networks configured by links connecting a plurality of nodes,
In a routing table setting method performed by a node belonging to a plurality of areas and sharing one routing table for all the plurality of areas,
The node includes a plurality of routing protocol units corresponding to the area to which the node belongs,
When any one of the routing protocol units tries to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. If it is set by the routing protocol part, the first route entry is set in the routing table if the route cost of the first route entry is smaller than the route cost of the second route entry. A routing table setting method characterized by:

(Supplementary Note 2) In an environment where there are a plurality of areas that are sub-networks configured by links connecting a plurality of nodes,
In a routing table setting method performed by a node belonging to a plurality of areas and sharing one routing table for all the plurality of areas,
The node corresponds to each area to which the node belongs, and includes a plurality of routing protocol units each assigned an individual identification number,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Whether the first route entry is set based on the magnitude relationship between the identification number of the first routing protocol part and the identification number of the second routing protocol part. A routing table setting method characterized by determining whether or not.

(Additional remark 3) It is a subnetwork comprised by the link which connects between several nodes, In the environment where the several area where each individual identification number was allocated exists,
In a routing table setting method performed by a node belonging to a plurality of areas and sharing one routing table for all the plurality of areas,
The node includes a plurality of routing protocol units corresponding to the area to which the node belongs,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Is set by the routing protocol part of the first routing protocol part based on the magnitude relationship between the identification number of the area corresponding to the first routing protocol part and the identification number of the area corresponding to the second routing protocol part. A routing table setting method comprising: determining whether or not to set a route entry.

(Supplementary note 4) In the routing table setting method according to any one of supplementary notes 1 to 3,
If the second route entry is not set, and if the routing protocol part that set the second entry is the same as the routing protocol part that is trying to set the first entry, A routing table setting method, wherein the first route entry is set in the routing table.

(Supplementary note 5) In the routing table setting method according to any one of supplementary notes 1 to 4,
The plurality of routing protocol units are:
A link state information exchange step for exchanging link state information with an adjacent node belonging to the area corresponding to the routing protocol part;
Preparing a link state database for storing the link state information exchanged by the link state information exchange unit;
A route calculation step of calculating a minimum cost route to each destination node belonging to an area corresponding to the routing protocol unit based on the stored link state information;
With
A routing table setting method, wherein the route entry is calculated based on a calculation result of the route calculation step.

(Supplementary note 6) In the routing table setting method according to any one of supplementary notes 1 to 5,
The link is a link created by assigning the same radio communication frequency to radio interfaces of two nodes existing within a mutual propagation distance, and means one or more links created by the same radio communication frequency. A routing table setting method characterized by defining a link belonging to the same group.

(Supplementary note 7) In an environment where there are a plurality of areas that are sub-networks configured by links connecting a plurality of nodes,
In a node belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
Provided with a plurality of routing protocol parts corresponding to each area to which it belongs,
When any one of the routing protocol units tries to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. If it is set by the routing protocol part, the first route entry is set in the routing table if the route cost of the first route entry is smaller than the route cost of the second route entry. A node characterized by

(Supplementary Note 8) In an environment where there are multiple areas that are sub-networks configured by links connecting multiple nodes,
In a node belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
Corresponding to each area to which it belongs, each comprising a plurality of routing protocol parts assigned with individual identification numbers,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Whether the first route entry is set based on the magnitude relationship between the identification number of the first routing protocol part and the identification number of the second routing protocol part. A node characterized by determining whether or not.

(Supplementary Note 9) A sub-network configured by links connecting a plurality of nodes, and in an environment where there are a plurality of areas each assigned an individual identification number,
In a node belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
Provided with a plurality of routing protocol parts corresponding to each area to which it belongs,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Is set by the routing protocol part of the first routing protocol part based on the magnitude relationship between the identification number of the area corresponding to the first routing protocol part and the identification number of the area corresponding to the second routing protocol part. A node characterized by determining whether or not to set a route entry.

(Supplementary Note 10) In the node according to any one of Supplementary Notes 7 to 9,
If the second route entry is not set, and if the routing protocol part that set the second entry is the same as the routing protocol part that is trying to set the first entry, The node, wherein the first route entry is set in the routing table.

(Supplementary note 11) In the node according to any one of Supplementary notes 7 to 10,
The plurality of routing protocol units are:
A link state information exchange unit for exchanging link state information with an adjacent node belonging to an area corresponding to the routing protocol unit;
A unit for preparing a link state database for storing the link state information exchanged by the link state information exchange unit;
A route calculator that calculates a minimum cost route to each destination node belonging to an area corresponding to the routing protocol unit based on the stored link state information;
With
A node that calculates the route entry based on a calculation result of the route calculation unit.

(Supplementary note 12) In the node according to any one of Supplementary notes 7 to 11,
The link is a link created by assigning the same radio communication frequency to radio interfaces of two nodes existing within a mutual propagation distance, and means one or more links created by the same radio communication frequency. A node characterized by defining a link belonging to the same group.

(Additional remark 13) It is a subnetwork comprised by the link which connects between several nodes, In the environment where the several area where each individual identification number was allocated exists,
In a communication system including a plurality of nodes belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
A communication system, wherein the node is the node according to any one of appendices 7 to 12.

L11, L21 to L23, L31 to L35, L42 Links A to F, Node 1000, Node 2000 Nodes X, Y, Z, W Area 110-1 First area routing protocol unit 110-2 Second area routing protocol unit 110-N N-th area routing protocol units 111-1, 111-2, 111-N link state information exchange units 112-1, 112-2, 112-N link state databases 113-1, 113-2, 113- N route calculation unit 114-1, 114-2, 114-N route setting unit 200 minimum route cost entry determination unit 300 routing table 400 route setting availability determination unit 501, 502 link cost table 503-506 routing table 507, 508 link state Database 50 9-512 routing table

Claims (10)

In an environment where there are multiple areas that are sub-networks configured by links connecting multiple nodes,
In a routing table setting method performed by a node belonging to a plurality of areas and sharing one routing table for all the plurality of areas,
The node includes a plurality of routing protocol units corresponding to the area to which the node belongs,
When any one of the routing protocol units tries to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. If it is set by the routing protocol part, the first route entry is set in the routing table if the route cost of the first route entry is smaller than the route cost of the second route entry. A routing table setting method characterized by: In an environment where there are multiple areas that are sub-networks configured by links connecting multiple nodes,
In a routing table setting method performed by a node belonging to a plurality of areas and sharing one routing table for all the plurality of areas,
The node corresponds to each area to which the node belongs, and includes a plurality of routing protocol units each assigned an individual identification number,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Whether the first route entry is set based on the magnitude relationship between the identification number of the first routing protocol part and the identification number of the second routing protocol part. A routing table setting method characterized by determining whether or not. It is a sub-network composed of links connecting multiple nodes, and in an environment where there are multiple areas each assigned an individual identification number,
In a routing table setting method performed by a node belonging to a plurality of areas and sharing one routing table for all the plurality of areas,
The node includes a plurality of routing protocol units corresponding to the area to which the node belongs,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Is set by the routing protocol part of the first routing protocol part based on the magnitude relationship between the identification number of the area corresponding to the first routing protocol part and the identification number of the area corresponding to the second routing protocol part. A routing table setting method comprising: determining whether or not to set a route entry. The routing table setting method according to any one of claims 1 to 3,
If the second route entry is not set, and if the routing protocol part that set the second entry is the same as the routing protocol part that is trying to set the first entry, A routing table setting method, wherein the first route entry is set in the routing table. In the routing table setting method according to any one of claims 1 to 4,
The plurality of routing protocol units are:
A link state information exchange step for exchanging link state information with an adjacent node belonging to the area corresponding to the routing protocol part;
Preparing a link state database for storing the link state information exchanged by the link state information exchange unit;
A route calculation step of calculating a minimum cost route to each destination node belonging to an area corresponding to the routing protocol unit based on the stored link state information;
And
A routing table setting method, wherein the route entry is calculated based on a calculation result of the route calculation step. The routing table setting method according to any one of claims 1 to 5,
The link is a link created by assigning the same radio communication frequency to radio interfaces of two nodes existing within a mutual propagation distance, and means one or more links created by the same radio communication frequency. A routing table setting method characterized by defining a link belonging to the same group. In an environment where there are multiple areas that are sub-networks configured by links connecting multiple nodes,
In a node belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
Provided with a plurality of routing protocol parts corresponding to each area to which it belongs,
When any one of the routing protocol units tries to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. If it is set by the routing protocol part, the first route entry is set in the routing table if the route cost of the first route entry is smaller than the route cost of the second route entry. A node characterized by In an environment where there are multiple areas that are sub-networks configured by links connecting multiple nodes,
In a node belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
Corresponding to each area to which it belongs, each comprising a plurality of routing protocol parts assigned with individual identification numbers,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Whether the first route entry is set based on the magnitude relationship between the identification number of the first routing protocol part and the identification number of the second routing protocol part. A node characterized by determining whether or not. It is a sub-network composed of links connecting multiple nodes, and in an environment where there are multiple areas each assigned an individual identification number,
In a node belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
Provided with a plurality of routing protocol parts corresponding to each area to which it belongs,
When the first routing protocol unit attempts to set a first route entry for a certain destination node in the routing table, a second route entry for the certain destination node already exists in the routing table. Is set by the routing protocol part of the first routing protocol part based on the magnitude relationship between the identification number of the area corresponding to the first routing protocol part and the identification number of the area corresponding to the second routing protocol part. A node characterized by determining whether or not to set a route entry. It is a sub-network composed of links connecting multiple nodes, and in an environment where there are multiple areas each assigned an individual identification number,
In a communication system including a plurality of nodes belonging to a plurality of the areas and sharing one routing table for all the plurality of areas,
A communication system, wherein the node is the node according to any one of claims 7 to 9.

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