JP3878140B2 - Communication node, routing information advertising method, routing information advertising program, and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication node for performing path control in a network using bucket switches such as IP and MPLS, and a network composed of TDM switches and optical switches such as GMPLS, a routing information advertising method, a routing information advertising program, and a recording medium About.
[0002]
[Prior art]
In recent years, due to the rapid spread of the Internet and LAN, data traffic including IP traffic has increased exponentially. To cope with the increase in traffic, the backbone network is in the direction of higher speed and larger scale.
[0003]
In an IP network, in order to solve routing in the network, a link state routing protocol such as OSPF or IS-IS is operating in each router in the network (for example, see Non-Patent Document 1). Using these routing protocols, each router grasps its own network topology (connection configuration) and creates an IP packet forwarding table necessary for forwarding IP packets. In these routing protocols, when distributing routing information in the network, an advertisement method called “Reliable Flooding” is used. Basically, in this system, since the bucket transmission including the same routing information is performed on all the interfaces of each router, there is a problem in the efficiency of routing information distribution. In particular, in a network in which each router is mesh-connected, the amount of protocol messages in the network is proportional to the square of the number of routers.
[0004]
Further, recently, a network is demanded for a mechanism for providing an advanced service for dealing with VoIP (Voice over IP), streaming delivery, and the like. In order to respond to such a request, MPLS (Multiprotocol Label Switching) has been proposed so far (see, for example, Non-Patent Document 2).
[0005]
MPLS assigns a fixed-length label to a packet to be transferred, and determines a route to be transferred at each node in the communication network based on the label. By introducing this MPLS into the IP backbone network, advanced traffic engineering such as quality assurance and load distribution becomes possible. The routing protocol is also used as a means for distributing the link state necessary for performing the traffic engineering in the network.
[0006]
Recently, even in a network composed of communication nodes that do not handle packets such as TDM switches, optical cross-connects, and optical switches other than IP networks, such as GMPLS, for collecting network topology and link state information. In addition, routing protocols such as OSPF and IS-IS are used (see, for example, Non-Patent Document 3).
[0007]
[Non-Patent Document 1]
J. et al. Moy, 0SPF: Anatomy of an internet routing protocol, Addison-Wesley, 1998.
[Non-Patent Document 2]
Takashi Miyamura, Takashi Kurimoto, Michihiro Aoki, “A Scalable Multipath Algorithm in Hierarchical MPLS Networks”, Proc. of WTC / ISS2002.
[Non-Patent Document 3]
J. et al. Moy, “Flooding over a subset topology”, IETF, Internet Draft, February 2001.
[0008]
[Problems to be solved by the invention]
As described above, the increase in the size of the network and the diversification of the types of information to be delivered by the routing protocol increases the amount of messages of the routing protocol in the network, and the load on the processor of each router that processes the protocol is a problem. It has become. When a high load is applied to the processor, the processing time of each message of the protocol increases, so that the convergence time of routing in the network increases. Eventually, it caused various instabilities in the network such as the occurrence of routing loops, which was a problem.
[0009]
As means for solving such a problem, techniques of “refresh stop” and “link panda ring” have been proposed so far.
[0010]
First, “refresh stop” will be described. In a normal routing protocol, even when there is no change in the connection configuration of routers in the network, a database that holds topology information is periodically updated. This update is called refresh. In this method, when there is no change in the topology, refresh is stopped and distribution of useless routing information is suppressed. This method is effective for a stable network with little change in topology. However, even if the topology of the network does not change, as in the case of performing link state advertisement necessary for traffic engineering, it is not effective in the case where advertisement by a routing protocol is required periodically.
[0011]
Next, “link bundling” will be described. As shown in FIG. 6, when a plurality of links exist between the two routers 1 and 2, the normal routing protocol establishes an adjacency for each link and advertises routing information individually. In this method, a plurality of links are bundled into one link (= bundling) and advertised in the network as one virtual link, thereby suppressing advertisement of useless routing information. As shown in FIG. 6, this method is effective only when a plurality of links exist between the specific routers 1 and 2, and cannot be applied when one router is connected to a plurality of different routers.
[0012]
The present invention has been made in view of the above-described circumstances, can reduce the convergence time of routing, and can ultimately improve the stability of the network. In addition, a large number of links between the same nodes. An object of the present invention is to provide a communication node, a routing information advertising method, a routing information advertising program, and a recording medium that can be applied to a general network topology.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problem, in the invention according to claim 1, in the communication node arranged on the network and operating the routing protocol, the routing protocol is separated from the topology of the network learned by the routing protocol. Topology calculating means for calculating a topology used for delivering a message, and selecting means for selecting a link for transmitting a packet including routing information based on the topology calculated by the topology calculating means , The computing means recalculates the topology based on the number of nodes connected to each node in the routing protocol message delivery topology, by adding a link connected to the node to the topology, G If the topology of the local network is adjacent to two or more nodes when the topology is recalculated, and the topology used for message distribution is less than two As far as this node is concerned, a node adjacent to the node is added to the topology used for message delivery .
[0016]
Further, in order to solve the above-described problems, in the invention according to claim 2 , in the routing information advertising method of the routing protocol operating on the network composed of a plurality of communication nodes, learning is performed with the routing protocol. Separately from the topology of the network, to calculate the topology used to deliver the routing protocol message, to select a link for transmitting a packet including routing information based on the calculated topology, and to deliver the routing protocol When calculating the topology to be used in the routing protocol, based on the number of nodes to which each node is connected in the routing protocol message delivery topology, a link connected to the node is added to the topology. When recalculating the topology used for message delivery of the routing protocol, it is a node that is adjacent to two or more nodes in the topology of its own network, and is adjacent in the topology used for the calculated message delivery. Only when the number of nodes is less than two, a node adjacent to the node is added to the topology used for message delivery .
[0019]
In order to solve the above-described problem, in the invention according to claim 3 , the routing protocol is separated from the topology of the network learned by the routing protocol operating on the network composed of a plurality of communication nodes. Causing the computer to execute a first step of calculating a topology used to deliver the message of the second message and a second step of selecting a link for transmitting a packet including routing information based on the calculated topology ; In the first step, when calculating the topology to be used for delivering the routing protocol, based on the number of nodes to which each node is connected in the routing protocol message delivery topology, Added links to the topology And recalculating the topology, and recalculating the topology used for routing protocol message delivery, the topology of the own network is a node adjacent to two or more nodes, and is calculated in the topology used in the message delivery only if the number of neighboring nodes is less than two, and wherein Rukoto to execute the steps in the computer to add a node adjacent to the node to the topology used in the message delivery To do.
[0020]
In order to solve the above-described problem, in the invention according to claim 4 , the routing protocol is separated from the topology of the network learned by the routing protocol operating on the network composed of a plurality of communication nodes. Causing the computer to execute a first step of calculating a topology used to deliver the message of the second message and a second step of selecting a link for transmitting a packet including routing information based on the calculated topology ; In the first step, when calculating the topology to be used for delivering the routing protocol, based on the number of nodes to which each node is connected in the routing protocol message delivery topology, Added links to the topology And recalculating the topology, and recalculating the topology used for routing protocol message delivery, the topology of the own network is a node adjacent to two or more nodes, and is calculated in the topology used in the message delivery only if the number of neighboring nodes is less than two, the routing information advertising program that the topology to be used for message delivery Ru to execute the steps in the computer to add a node adjacent to the node Is recorded.
[0021]
According to the present invention, the topology calculation means calculates the topology used for delivering the routing protocol message separately from the network topology learned by the routing protocol, and the selection means calculates the routing based on the calculated topology. Select the link to send the packet containing information. Therefore, advertisement of redundant routing information can be suppressed, and the load for processing the routing protocol of the processor in each communication node can be reduced. Reducing the processing load on the processor of each node can shorten the convergence time of routing and ultimately improve the stability of the network.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
First, the routing information advertisement system according to this embodiment will be described. FIG. 1 is a conceptual diagram illustrating an example of an IP network. The network shown in FIG. 1 includes four nodes 10, 11, 12, and 13, and each of the nodes 10 to 13 is connected to each other by a link indicated by a solid line. In each of the nodes 10 to 13, a link state type routing protocol such as OSPF or IS-IS operates, and the topology of the own network can be learned.
[0024]
Before describing the advertisement method of this embodiment, an advertisement method called “Reliable Flooding” employed in a normal link state type routing protocol will be described. An arrow shown in FIG. 1 represents a direction in which a packet including routing information is transmitted. Here, it is assumed that a failure has occurred in the link between the node 13 and the subnet 20 connected thereto. The node 13 needs to transmit information that the subnet 20 has become unreachable to other routers in the network. Typically, this information is advertised to all routers that have established routing protocol adjacencies.
[0025]
As shown by the arrows in FIG. 1, the node 13 advertises the updated routing information of the nodes 10, 11, and 12. At this point, all routers in the network have received updated routing information from the node 13. However, in the conventional advertising method, each of the nodes 10, 11, and 12 advertises the same information again to all routers other than the node 13 that is the transmission source of the routing information. In this way, in the conventional advertising method, a large amount of redundant routing information is advertised, so the message volume of the protocol to be processed increases. Especially in a large-scale network, the processing load of the message in each router is a problem. there were.
[0026]
In the present embodiment, the above problem is solved by limiting the links used for transmission of packets including routing information.
[0027]
FIG. 2 is a flowchart for explaining the operation of the advertisement method according to the embodiment of the present invention. First, the topology information of the own network is learned using a normal routing protocol (S1). Next, a tree for routing information delivery is created based on the topology information (S2). Eventually, the packet including the routing information is transmitted only on the link included in the routing information delivery tree. Details of the tree calculation algorithm will be described later.
[0028]
When the calculation of this tree is completed, each of the routers 10 to 13 in the network checks whether there is a link that is currently used for advertising routing information that is not included in this tree. . If such a link exists, transmission of routing information on this link is stopped thereafter (S3). At this time, the adjacent relationship established on this link may be stopped, or only Flooding may be stopped while maintaining the adjacent relationship.
[0029]
FIG. 3 is a conceptual diagram showing an example of a routing information delivery tree. In the figure, the transmission of routing information on the link between the node 10 and the node 13 and the link between the node 11 and the node 12 is stopped. As in the previous example, let us consider a case where a failure has occurred in the link between the node 13 and the subnet 20. The node 13 advertises routing information to the nodes 11 and 12. Next, since the node 11 and the node 12 can advertise the routing information only to the node 10 other than the node 13, the routing information is transmitted to the node 10. This completes the distribution of routing information within the network. Compared to the case shown in FIG. 3, it can be seen that the number of protocol messages generated in the network is reduced.
[0030]
Next, an algorithm for calculating the routing information delivery tree shown in FIG. 3 will be described. FIG. 4 is a flowchart for explaining this algorithm. First, a minimum spanning tree is created from the topology of the own network (S10). As an algorithm for calculating the minimum tree, a prim algorithm or the like is known.
[0031]
FIG. 5 is a conceptual diagram showing a minimum tree for the network shown in FIG. Here, instead of the minimum tree, a shortest tree (Shortest path tree) may be used. For the calculation of the shortest tree, Dijkstra Algorithm can be used.
[0032]
This minimum tree may be used as a routing information distribution tree (hereinafter simply referred to as a distribution tree), but in this case, the following problem occurs. In FIG. 5, if a failure occurs in the link between the node 10 and the node 11, the routing domain is divided into two. For example, the node 10 cannot solve the routing to the node 13. A means for solving this problem will be described. For this purpose, first, the order of nodes is defined.
[0033]
Node degree: Number of links connected to the node [0034]
For example, the order of a node having two links is “2”.
[0035]
First, the initial state of the delivery tree is set to the minimum tree. Then, the degree of the node in the distribution tree is calculated.
[0036]
Next, it is determined whether or not there is a node satisfying the condition A: “the node order in the original network is 2 or more” and “the node order in the distribution tree is less than 2” (S11). If the condition is satisfied, the link of the corresponding node is added to the delivery tree (S12).
[0037]
When there are a plurality of link candidates to be added, there are the following two selection methods.
・ Select one random link from multiple candidate links.
-Select one link that is connected to the opposite node having the smallest degree among a plurality of candidate links.
[0038]
Next, the order of the delivery tree is calculated again (S13), and it is checked again whether or not the condition 1 is satisfied in step S11. If the condition A is satisfied, a link is added in step S12.
[0039]
On the other hand, if the condition A is not satisfied, the distribution tree at that time is used as a routing information distribution tree (S14). The above is the details of the algorithm.
[0040]
The above-described embodiment relates to a routing information advertisement method in a routing protocol. Even if the target node is an IP router or an MPLS router that performs packet switching, a TDM switch or optical switch that does not perform packet switching.・ Applicable even to optical cross-connects.
[0041]
The router function described above is realized by executing a program stored in a storage unit (not shown). The storage unit is configured by a hard disk device, a magneto-optical disk device, a nonvolatile memory such as a flash memory, a volatile memory such as a RAM (Random Access Memory), or a combination thereof. Further, the storage unit is a fixed time such as a volatile memory (RAM) in a computer system serving as a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. Includes those holding programs.
[0042]
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information such as a network such as the Internet or a communication line such as a telephone line. The program may be for realizing a part of the above-described processing. Furthermore, what can implement | achieve the process mentioned above in combination with the program already recorded on the router, what is called a difference file (difference program) may be sufficient.
[0043]
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above-described embodiment, and includes a design and the like within a scope not departing from the gist of the present invention. .
[0044]
【The invention's effect】
As described above, according to the present invention, since it is possible to provide an efficient routing information advertisement method in a network in which a routing protocol operates, it is possible to suppress advertisement of redundant routing information. It is possible to reduce the load of processing the routing protocol of the processor in each communication node. Reducing the processing load on the processor of each node has the advantage of shortening the convergence time of routing and ultimately improving the stability of the network. Further, according to the present invention, it can be applied to a general network topology including a case where a large number of links exist between the same nodes, and distribution of link state information such as bandwidth information used for traffic engineering is also efficient. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating an example of an IP network.
FIG. 2 is a flowchart for explaining an operation of an advertisement method according to an embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an example of a routing information delivery tree.
FIG. 4 is a flowchart for explaining this algorithm.
FIG. 5 is a conceptual diagram showing a minimum tree for the network shown in FIG. 4;
FIG. 6 is a conceptual diagram showing an example of an IP network when a plurality of links exist between two routers.
[Explanation of symbols]
10, 11, 12, 13 nodes (topology calculation means, selection means)
20 subnets

Claims (4)

In a communication node that is placed on the network and runs a routing protocol,
In addition to the topology of the network learned by the routing protocol, topology calculation means for calculating the topology used for delivering the routing protocol message,
Selection means for selecting a link for transmitting a packet including routing information based on the topology calculated by the topology calculation means ;
The topology calculation means includes
Based on the number of nodes to which each node is connected in the routing protocol message delivery topology, recalculate the topology by adding links connecting to that node to the topology;
When recalculating the topology, the topology of the network is adjacent to two or more nodes, and the topology used for the calculated message delivery has less than two adjacent nodes. Only if the node adjacent to the node is added to the topology used for message delivery
A communication node characterized by that . In the routing information advertising method of a routing protocol operating on a network composed of a plurality of communication nodes,
Apart from the network topology learned by the routing protocol, calculate the topology used to deliver the routing protocol messages,
Selecting a link that transmits a packet including routing information based on the calculated topology ;
When calculating the topology used to deliver the routing protocol, based on the number of nodes to which each node is connected in the routing protocol message delivery topology, the link connected to that node is added to the topology. Recalculate the topology by
When recalculating the topology used for routing protocol message delivery, the number of nodes that are adjacent to two or more nodes in the topology of the local network and that are adjacent to the calculated message delivery topology A routing information advertisement method characterized by adding a node adjacent to the node to the topology used for message delivery only when the number is less than two . A first step of calculating a topology to be used for delivering routing protocol messages separately from a network topology learned by a routing protocol operating on a network composed of a plurality of communication nodes;
Based on the calculated topology, causing the computer to perform a second step of selecting a link to transmit a packet containing routing information ;
In the first step,
When calculating the topology used to deliver the routing protocol, based on the number of nodes to which each node is connected in the routing protocol message delivery topology, the link connected to that node is added to the topology. Recalculating the topology by:
When recalculating the topology used for routing protocol message delivery, the number of nodes that are adjacent to two or more nodes in the topology of the local network and that are adjacent to the calculated message delivery topology there only if less than two, the routing information advertising program characterized Rukoto to execute the steps in the computer to add a node adjacent to the node to the topology used for message delivery. A first step of calculating a topology to be used for delivering routing protocol messages separately from a network topology learned by a routing protocol operating on a network composed of a plurality of communication nodes;
Based on the calculated topology, causing the computer to perform a second step of selecting a link to transmit a packet containing routing information ;
In the first step,
When calculating the topology used to deliver the routing protocol, based on the number of nodes to which each node is connected in the routing protocol message delivery topology, the link connected to that node is added to the topology. Recalculating the topology by:
When recalculating the topology used for routing protocol message delivery, the number of nodes that are adjacent to two or more nodes in the topology of the local network and that are adjacent to the calculated message delivery topology there only if less than two, the recording medium characterized by recording a routing information advertising program that the topology to be used for message delivery Ru to execute the steps in the computer to add a node adjacent to the node.

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