JP2002305536A - Path controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a path controller that can transmit packets through a bypass node not via the shortest path in order to distribute loads depending on the state of the loads in the case of transmitting the packets. SOLUTION: The path controller provides each node for the transmission of packets from a start point node A to a target node D on a network, selects a bypass node B to instruct to take a detour to the packets and generates a bypass node address packet that is a packet to which an address of the bypass node B is attached. When a node receives packets and the address of the received packets indicates the bypass node address packet, the node extracts packets from which the address of the bypass node B is excluded and the node transmits the resulting packets to the target node D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a route control device for controlling a route in a network.

[0002]

2. Description of the Related Art A packet-switched communication network is
A packet in which information is divided into an appropriate data size is transmitted to a packet switching network for communication. Each packet includes destination / destination, error correction, packet order ID, etc.
Control information for reliably transmitting the information is written in the header. Also, the packet switch constantly checks whether the neighboring packet switches (nodes) are alive, and if there is a node that has failed or is down, recognizes that the node is out of service and updates the topology database. I do.

[0003] This network is represented by a configuration in which nodes are connected to each other as shown in FIG. 8. Each node looks at a destination included in a packet, and if it is addressed to itself, captures it. For example, it has a route control function of transmitting to the next node. In general, a node can operate as a router, which is dedicated hardware, or a router in which a plurality of network adapters are attached to a computer. Each node needs a routing table to determine its connection behavior. Now
When there is a packet going out of its own node, it has a function of checking the address of the destination, judging it from the data written in the routing table, and switching.

In recent years, in the route control at each node in a large-scale network such as the Internet, the use of which is expanding, only the shortest route method is used.
A plurality of load distributions are limited between paths having the same distance metric (for example, OSPF (Open Shortest
Path First protocol). This is the next destination (next hop) based on the routing table for forwarding communication packets.
In general, only the method of designating only is specified.

FIG. 8 shows an outline of a conventional method for transmitting a packet. In FIG. 8, the bold arrow belongs to the shortest path tree. Here, the node A is a start node, and the node D is a target node. When transmitting a packet from the node A to the node D, the shortest path method normally uses only the shortest path (in FIG. 8, the path passing through the node C) represented by a dashed line calculated according to some metric.

[0006]

In some cases, it is better to make a detour without passing through the shortest path in order to distribute the load from the load state or the like. However, in the conventional method,
Even if a detour node is selected, there is a possibility that when a packet is transferred to a detour that increases the distance, a loop may occur and a route that does not reach the target node may be generated. For example, as shown in FIG. 9, when a packet is transmitted from the source node A to the destination node D, even if the node B is designated as the detour node, the shortest path is from the node A to the node D represented by a dashed line. Route and may return to the original route.

[0007] Alternatively, a loop can be prevented by the start-point route control that specifies the route to the destination node at the start-point node that is the transmission source, but in this case, the header information of the packet becomes too large. There is a point. Also, in the actual Internet, start point control is hardly used, and there are many organizations that do not pass packets by the start point control by filtering, so that packet transfer itself by the start point control may not be possible.

[0008]

In order to solve the above-mentioned problems, according to the present invention, each node is provided for transmitting a packet from a source node to a destination node on a network, and the destination of the received packet is determined by the destination. A route control device that obtains a packet if the packet is addressed to the node and transmits the packet to the next node if the destination of the packet is not addressed to the node; A detour node-destined packet creating means for creating a detour node-destined packet to which the detour node destination is attached; A detour node destination removing means for extracting the packet, and a packet for transmitting the packet excluding the destination of the detour node to the destination node. And a Tsu door transmission means.

In the above configuration, in a route control device such as a router for transmitting a packet from a source node to a destination node, when a detour is designated at the time of transmitting a packet,
It is possible to create a packet addressed to a detour node with a destination addressed to the detour node, and transmit the packet to the target node via the detour node. At the time of packet reception, if the received packet is a packet addressed to the bypass node, the destination of the bypass node is removed and transmitted to the target node.

According to a second aspect of the present invention, in the route control device according to the first aspect, the detour node-addressed packet is a packet having a plurality of destinations of the detour node.

In the above configuration, it is possible to specify a plurality of detour routes by further specifying a detour node in a packet with a destination of the detour node.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, the path control device 1 according to the present embodiment transmits a packet via a packet receiving unit 10 for receiving a transmitted packet, a packet transmitting unit 11 for transmitting a packet, and a bypass node. In such a case, a detour node-destined packet creating means (or encapsulation packet), which is a packet encapsulated by adding the destination of the detour node to the packet destined for the target node, (or an encapsulation packet) A detour node destination removing unit (or an encapsulation removing unit) 13 for converting the received packet into a packet destined for the original destination node if the received packet is an encapsulated packet; and a routing table 14.
, And is roughly composed of The detour-node-destined packet creating unit 12 includes a detour-route selecting unit 120 that selects a detour route based on the routing table 14.

The operation of the routing table 14 is roughly classified into two types. One is a method of writing manually by a network administrator, and the other is a method of automatically creating information while exchanging information between routers. The former is called static routing, and the latter is called dynamic routing. At present, when the Internet is increasing rapidly, the routing table 14 cannot cope with dynamic routing. Therefore, a routing table 14 automatically created while exchanging information between routers by broadcast is used. Hereinafter, a description will be given using dynamic routing as an example.

The packet receiving means 10 looks at the destination contained in the header of the received packet, and if this node matches the destination, takes in the packet to its own network 15; hand over. If the received packet is an encapsulated packet, the detour node destination removing unit (encapsulation removing unit)
Hand over to 13. The packet transmitting means 11 looks at the destination of the packet to be transmitted, refers to the routing table 14, selects which node to transmit to, and transmits the packet. The detour node-addressed packet creation means (encapsulated packet creation unit) 12 automatically selects a bypass route in view of the load state of the external network. Alternatively, a detour route may be selected based on a time zone or an instruction from a person. When an instruction to select a bypass route is issued, the bypass route selection unit 120 selects a bypass node based on the routing table 14. Therefore, a packet including the original destination of the destination node and a destination of the detour node is created and passed to the packet transmitting means 11. The bypass node destination removing unit (encapsulation removing unit) 13 passes the packet obtained by removing the header of the bypass node from the received packet to the packet transmitting unit 11.

Further, in order to select a detour node by the detour path selection means 120, the following conditions must be satisfied. -There is no detour node on the route from the start node to the destination node.・ Start node to shortest route of detour node and detour node
There is no overlap in the shortest route of the destination node. When the above conditions are satisfied, there is no loop in the generated alternative road. For example, as shown in FIG. 2, the control of the alternative route is conventionally performed by first transferring a packet from the start node A to the detour node B by the shortest route method, and then transferring the packet from the detour node B to the destination node D. Using the shortest path method framework. In FIG. 2, a thick line arrow belongs to the shortest path tree to the destination node D, and a two-dot chain line arrow belongs to the shortest path tree from the start node A to the detour node B. Further, the wavy arrow is an alternative route.

Next, an encapsulated packet obtained by encapsulating a packet destined for the target node by adding the destination of the detour node will be described with reference to FIG. Start node A
When sending data to the destination node D from the destination node D, a packet 22 addressed to the destination node D is created by adding a header including the destination 20 of the destination node D to the data 21 to be sent. In order to send this packet to the destination node D via the bypass node B, the detour node B
A header including the destination 23 is added to create an encapsulated packet 24.

Next, the operation of the route control device 1 will be described with reference to a flowchart. First, the operation when a packet is generated in the own network and the packet is transmitted will be described with reference to the flowchart in FIG. When transmitting a packet generated in the own network (S100), it is determined whether to use the shortest path or the detour path in consideration of the current load state and the like (S101).

Whether or not to use the detour route can be set so that a person observes the load state of the network and determines that the shortest route is congested, and also uses the detour route together. For example, as a result of observation, when the shortest route is crowded depending on the time zone, it is possible to set so that the detour route is selected in the crowded time zone. Alternatively, for example, the route control device 1 basically uses the shortest route, periodically observes the delay, and sets a certain value (for example, (packet size / bandwidth to The sum of the links of *) * (1 + α)
, Etc.), it is also possible to use a bypass route and stochastically distribute communication packets along the shortest route and the bypass route. The percentage is calculated based on each delay. As an example of the delay calculation, the shortest path delay
If d (0) and the delay of the detour are d (1), d (2), ..., d (n), the probability of selecting each route to increase the ratio of routes with small delays Find p (i) as p (i) = r (i) / (r (0) + r (1) + ... + r (n)), r (i) = 1 / d (i) be able to.

When a detour route is selected (S101)
YES), the detour path selection means 120 selects a detour node (S102), and the detour node-destined packet creation means (encapsulated packet creation unit) 12 selects a detour node to include the destination 20 of the destination node D. An encapsulated packet 24 is created by encapsulating the packet 22 addressed to the node D with the destination 23 of the bypass node B (S10).
3). Further, the packet transmitting means 11 transmits the packet to the next node based on the routing table (S1).
04). When the detour route is not selected (S101 N
O), the generated packet is transmitted to the next node by the packet transmitting means 11 based on the routing table (S104).

Next, the operation when a packet arrives will be described with reference to the flowchart of FIG. When a packet is received (S200), the packet receiving means 10 determines whether the destination of the packet is addressed to the own node (S201),
If the packet is not addressed to the own node (NO in S201), the packet transmission unit 11 transfers the packet to the next node based on the routing table (S202). If it is addressed to its own node (S
201 YES), the header of the received packet is checked to determine whether the packet is encapsulated (S203).
If encapsulated (S203 YES),
The encapsulation removing unit 13 removes the header addressed to the detour node and extracts the packet (S205), and passes the packet to the packet transmitting unit 11. The packet transmitting means 11 transfers the packet to the next node based on the routing table (S206). If it is not encapsulated (S203
NO), the data is taken into the own network (S204).

FIG. 6 shows an example of selecting a detour node.
This will be described with reference to the flowchart of FIG. First, based on the shortest path tree, a set of a path from the start node to the destination node and a set of nodes that do not belong to the upstream path are obtained. For this, routing table 1
4, the shortest path tree can be easily obtained by tracing the shortest path tree from the target node to the start node and further to the upstream thereof, and removing nodes existing there (S300). The following methods are conceivable as a method of going upstream. Since the start node to the target node are one-way, they can be obtained by following the directed graph of the shortest path tree from the start node to the target node in the direction of the arrow. Also, for the upstream from the starting point node,
The node connected from the start node can be realized by following the arrow of the directed graph in the opposite direction. In this case,
Because it has a tree structure, it branches off on the way. In this case, the search can be performed by a tree-structured search algorithm such as a depth-first search well known as an algorithm.

Next, one detour node n is selected from N (S301). For this, the following method can be considered. 1. Random Method A detour node is randomly selected from a node set N. Therefore, the probability that node I is selected as a bypass node is p (i)
= 1 / N. 2. Weighted Random Method When selecting a detour node from the node set N, the selection probability of the node is selected by weighting, such as applying a probability weight according to the distance from the target node (or the starting node). For example, if the reciprocal of the distance of the node i from the target node is w (i), the probability that the node I is selected is p (i) = w (i)
/ SUMi (w (i)). (Where SUMi
Represents the sum of i included in the node set N. ) 3. Ordered shortest path method Lists various paths to the target node in ascending order of path length from the shortest path, with the first selection being the shortest (second) shortest path and the next being shortest. The shortest path is calculated in the order of the path (that is, the third shortest path), and the merging point with the node belonging to N is calculated (if there is a plurality of corresponding nodes, one is selected at random from among them). And

Here, based on the routing table 14, the shortest path r1 from the start node to the node n and the shortest path r2 from the node n to the destination node are obtained.
And whether there is an overlap in the route of r2 (S303),
If there is no overlap (S303 NO), n is determined as a bypass node (S304). If there is an overlap between the routes r1 and r2 (S303 YES), the next node is selected (S301). However, it is determined whether the selection of the node n has been performed K times (a certain number of times) or more (S30).
5) If performed K times or more (S305 YES),
It is determined that the determination of the detour node has failed (S306).

As described above in detail, it is possible to perform flexible alternative route control by appropriately selecting a detour node and creating an encapsulated packet addressed to the detour node.

Also, by encapsulating in multiples,
Complex route control can be performed. For example, as shown in FIG. 7, in order to transmit a packet to the destination node D,
E and F are designated as detour nodes. First, the detour node F
The encapsulated packet having the detour node E is further created in the encapsulated packet having the destination
, Bypasses the node E, further bypasses the node F, and transmits to the node D. In this way, it is possible to bypass a plurality of nodes.

[0026]

As described above, according to the route control device of the present invention, flexible alternative route control can be performed without changing the conventional control method using the routing table.
In addition, it is possible to control the alternative path flexibly while preventing generation of a loop without using start point control. Further, it is possible to specify a plurality of detour routes without using the start point control.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a route control device.

FIG. 2 is a diagram illustrating a state in which a packet is transmitted via a bypass node.

FIG. 3 is a diagram illustrating an encapsulated packet with a destination of a bypass node.

FIG. 4 is a flowchart when a detour node is selected at a start node and a packet is transmitted.

FIG. 5 is a flowchart when a packet is received.

FIG. 6 is a flowchart illustrating an example of selecting a bypass node.

FIG. 7 is a diagram illustrating a state in which a packet is transmitted by designating a plurality of detour nodes.

FIG. 8 is a diagram illustrating a state of transmitting a packet by a conventional shortest path.

FIG. 9 is a diagram illustrating a state where a loop is made when a detour route is designated.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 path control device 10 packet receiving means 11 packet transmitting means 12 detour node-destined packet creating means (encapsulated packet creating unit) 13 bypass node destination removing means (encapsulating removing unit) 14 routing table 15 own network 20 destination of destination node D Reference Signs List 21 data to be transmitted 22 packet addressed to destination node D 23 destination of detour node B 24 encapsulated packet 120 detour path selection means

Claims (2)

[Claims] 1. A node is provided in each node for transmitting a packet from a source node to a destination node on a network. If the destination of the received packet is addressed to the node, the packet is acquired, and the destination of the packet is addressed to the node. Otherwise, in a path control device transmitting to the next node, a detour path selecting means for selecting a detour node instructing a detour of a packet, and a detour node for creating a packet addressed to a detour node with the destination of the detour node in the packet Destined packet creation means, when receiving a packet, if the destination of the received packet is a packet addressed to a detour node, a detour node destination removal means for extracting a packet excluding the destination of the detour node; And a packet transmitting means for transmitting the packet to the destination node. 2. The route control device according to claim 1, wherein the detour node-addressed packet is a packet with a plurality of destinations of the detour node.