JPH11308276A - Route selection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select a route for a correct destination even when a link in the mid way becomes unusable by constituting a virtual communication network where the unusable link is eliminated from topology information of a communication network and selecting the shortest route when an edge node of a transmission terminal prepares route information. SOLUTION: When a link becomes unusable, its information is made to be reflected upon topology information of a reproduced virtual communication network in a virtual communication network construction part 23 of each of communication nodes A to L by having a use able/disable notification part 22 mutually notify the information between the communication nodes A to L. Then, in accordance with such a piece of information that certain links are unusable as this way, a route selection part 24 of the communication node A selects the shortest route to a specified communication node from the communication node A to a specified communication node faced on the topology information of the virtual communication network from which those unusable links are removed. A specified route information generation part 25 of the communication node A prepares specified route information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention is used for communication performed via a plurality of communication nodes constituting a communication network. The present invention is used for selecting the shortest path in a communication network. In particular, the present invention relates to a technique for selecting a shortest route that bypasses an unusable route.

[0002]

2. Description of the Related Art In order to perform communication via a communication network, it is necessary to select a route between a transmitting end and a receiving end. Information transfer methods include circuit switching and packet switching (datagram). Selection of a route in the case of circuit switching is performed using a destination address notified by a line setting signal at the time of line setting. In the case of packet switching, a route is selected using the destination address in the header of the packet. Note that even in the case of packet switching, when a virtual circuit (virtual circuit) is set without using a datagram, a route is selected at the time of setting the circuit.

[0003] Both circuit switching and packet switching are roughly classified into two methods according to the timing of selecting a route. One is a method of selecting a hop-by-hop route, and the other is a method of designating a route to a destination address at a transmitting end edge node of a communication network. Here, the hop-by-hop is a method of sending a setup message for connection connection to a communication node, and the communication node sequentially selects a next route having a margin in a band described in the setup message. An edge node refers to a communication node at a transmitting end or a receiving end.

The latter method is called source routing,
To do this, it is assumed that the transmitting edge node knows the topology of the communication network. Here, the relay method by the source routing means the bridge and the LAN indicated by the routing information following the source address.
It is a method of relaying via such as. The edge node at the transmitting end selects the shortest path to the destination based on the topology information of the communication network, and sets the path.

A typical example of source routing is AT
PNNI (Private Net)
work-Network Interface). Also, the header format is determined so that source routing is possible even with IPv6, which is the standard of the next-generation Internet protocol (the document name is RFC1883). Also, in the burst circuit switching network according to the invention of the present applicants, source routing is performed at the edge node at the transmitting end (Japanese Patent Application No. 9-222,197).
-334444, unpublished at the time of filing the present application).

[0006]

When performing source routing, the edge node at the transmitting end needs to know the topology of the communication network. Here, the topology of the communication network refers to the form of the communication network. A communication network generally has a bus type, a ring type, a star type, and a mesh type topology configuration. When a link failure occurs, communication may not be possible if the transmitting end edge node performs routing with old topology information before the information is propagated to the transmitting end edge node. If a link on the route has been used by another user, the user must wait until the link becomes available.

In these cases, in order to continue communication,
It is conceivable that a bypass route is selected at a communication node on the route. FIG. 5 is a diagram showing a conventional detour selection method. In FIG. 5, there is a communication node B on the shortest path from the communication nodes A to C. In FIG. 5, communication nodes A, B, and C
Only communication nodes are shown, but other communication nodes are not shown. Here, the shortest path from the communication node B to the communication node C is a part of the shortest path from the communication node A to C. Here, when the link from the communication node B to the communication node C cannot be used, the communication node B searches for the second shortest path between the communication node B and the communication node C, and selects that path. Conceivable.

However, in this method, a closed route is created as shown below, and it may not be possible to reach a desired destination address. FIG. 6 is a diagram illustrating an example of a communication network. FIG. 6 shows a communication network including communication nodes A to L and links 1 to 16. Assuming that the length of each link is the same, and considering the path selection from the communication node A to the communication node E, the shortest path is ABCDE.

Communication node A which is an edge node at the transmitting end
Selects this shortest path and starts communication. FIG. 7 is a diagram illustrating an example of a communication network in which a failure has occurred. Here, as shown in FIG. 7, when the link 3 connecting the communication node B and the communication node C cannot be used due to congestion or failure, the communication node B uses the link 3 which is the shortest path to the communication node E. Since it cannot be used, communication node B to communication node E
BFDGDE, which is the second shortest path to, is selected again.

Next, when the communication node F arrives at the communication node F and the link 8 connecting the communication node F and the communication node G cannot be used, the communication node F uses the second shortest path from the communication node F to the communication node E. A certain FHBCDE is reselected. However, since the link 3 connecting the communication node B and the communication node C cannot be used, when returning to the communication node B, a route to the communication node F is selected again, and a closed route is formed.

FIG. 8 is a diagram showing an example of another communication network. FIG. 9 is a diagram illustrating an example of another communication network in which a failure has occurred. The communication network shown in FIG. 8 is obtained by removing the communication node G, the link 8 and the link 9 from the communication network of FIG. In this example, as shown in FIG. 9, when it is determined that the link 3 cannot be used by the communication node B, a route to the communication node F is selected. Otherwise, FHB, which is the second shortest path, is selected, and a closed path is created as in the example of FIG.

[0012] Such a closed path is created because the communication node performing the path selection does not know the state other than the link directly connected to the communication node.

The present invention has been made in view of such a background, and provides a route selection device capable of selecting a route to a correct destination even when an intermediate link is unavailable due to congestion or failure. The purpose is to provide. The present invention
An object of the present invention is to provide a route selection device that can improve the throughput of a communication network.

[0014]

SUMMARY OF THE INVENTION According to the present invention, when a link becomes unavailable due to congestion or failure, the communication nodes notify each other of the availability status of the link. The information is reflected in the topology information of the communication network of the node. When creating path information, the edge node at the transmitting end configures a virtual communication network by removing its link from topology information of the communication network, and selects the shortest path.

[0015] In addition, until the information that the link becomes unusable is transmitted to the edge node, there may be a case where an interrupted route is temporarily selected. Similarly, the communication node also forms a virtual communication network, and selects the shortest path to the destination again. When the communication node knows that the link on the route is unusable, the communication node forms a virtual communication network by removing the unusable link from the topology information of the communication network, and transmits from the virtual communication network. From the path information between the end and the receiving end, all communication nodes sandwiched between the transmitting end and the link and links directly connected to the communication nodes are removed. In the virtual communication network thus formed, the shortest path from the communication node immediately before the disabled link to the destination is selected. In the route information between the transmitting end and the receiving end, the route information from the communication node immediately before the disabled link to the destination is replaced with the newly selected route information, and the route selection is continued. Do.

That is, the present invention comprises a plurality of communication nodes and a plurality of links interconnecting the plurality of communication nodes, and the communication node at the transmitting end sets a path from the transmitting end to the receiving end. It is a route selection device provided with a selection means. According to a feature of the present invention, the communication node is configured to determine whether a link connected to the communication node is usable regardless of the presence or absence of communication, and determine a determination result of the determination unit between the plurality of communication nodes. Means for notifying each other, and means for virtually reproducing the topology of the communication network according to the availability status notified by the notifying means. There is provided a means for selecting a route from the transmitting end to the receiving end on a virtually reproduced communication network.

Thus, even when a link on the way is unusable due to congestion or failure, a route to a correct destination can be selected. Therefore, the throughput of the communication network can be improved.

Preferably, the means for virtually reproducing the topology of the communication network includes means for updating the topology each time the availability of the link is changed. Alternatively, the means for virtually reproducing the topology of the communication network may include a means for periodically updating the topology regardless of a change in the availability state of the link.

Preferably, the means for selecting a path includes means for sequentially selecting a path having a smaller number of relay communication nodes.

Further, means for confirming the availability of the designated route in accordance with the received designated route information, and when there is a route newly recognized as being unusable by the confirming means, the designated route is determined to be unusable. Means for changing the route so as to bypass the recognized route.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of a main part of a communication node according to an embodiment of the present invention. FIG. 2 is a diagram showing a failure example of a communication network for explaining the first embodiment of the present invention.

As shown in FIG. 2, the present invention comprises a plurality of communication nodes A to L and a plurality of links 1 to 16 for interconnecting the plurality of communication nodes A to L, and The communication node is, as shown in FIG. 1, a route selection device 20 including a route selection unit 24 that is a means for selecting a shortest route from the transmission end to the reception end.

Here, the feature of the present invention is that the communication nodes A to L are provided with an availability judging unit 21 which is means for judging the availability status of a link connected to the communication node regardless of the presence / absence of communication. The availability notification unit 22, which is a means for mutually notifying the determination result of the availability determination unit 21 between the plurality of communication nodes A to L, and the availability status notified by the availability notification unit 22. A virtual communication network configuration unit 23, which is means for virtually reproducing the topology of the communication network in its own node, wherein the route selection unit 24 of the communication node at the transmitting end virtually reproduces the virtual network by the virtual communication network configuration unit 23 Is to select the shortest path from the transmitting end to the receiving end on the communication network.

In the embodiment of the present invention, the virtual communication network composing unit 23
Updates the topology whenever the availability status of the links 1 to 16 is changed. Another example is links 1 to
The topology may be updated periodically regardless of the change of the 16 availability status.

The route selecting unit 24 selects the routes in ascending order of the number of relay communication nodes. Further, the route selection unit 24
Confirms the availability status of the designated route according to the received designated route information, and if there is a route newly recognized as unusable by this check, bypasses the designated route to the route recognized as unusable To change.

The communication of information is performed by the communication device 30. At this time, the link availability information is input from the communication device 30 to the availability determination unit 21. The destination information of the information to be transferred is transmitted from the communication device 30 to the route selection unit 2.
4 is input. Also, the usability notification information from the usability notification unit 22 to other communication nodes is transferred to the other communication nodes via the communication device 30. After the route selection unit 24 selects a route according to the destination information of the information to be transferred,
The designated path information generation unit 25 generates designated path information according to the selected path and inputs the information to the communication device 30. The communication device 30 transfers information to be transferred based on the input designated path information. The designated path information is also transferred together with the information to be transferred.

[0027]

(First Embodiment) A first embodiment of the present invention will be described with reference to FIG. FIG. 2 illustrates the communication network shown in FIG.
It is assumed that when the link 3 between the communication node B and the communication node C and the link 8 between the communication node F and the communication node G become unavailable, a route is selected from the communication node A to the communication node E. .

The fact that the links 3 and 8 have become unusable is notified mutually by the communication nodes A to L by the availability notification unit 22 shown in FIG. The virtual communication network configuration unit 23 reflects the topology information of the virtual communication network reproduced. In order to transmit the information that the link has become unavailable to all communication nodes A to L in the communication network, a document by D. Bertsekas and R. Galallagar et al.
Section 5.3 of Data Networks (2nd ed., Prentice Hall, 1992)
(pp418-433).

To explain this method very simply, when a failure occurs in a link adjacent to a certain communication node, the communication node puts the link number in a message and directs the message to a link other than the failed link. Broadcast. A communication node adjacent to the communication node that has received the message broadcasts the message to a link other than the link that received the message. At this time, in order to prevent messages notifying the same information from overlapping, a message number is assigned to the message, the message is identified, and if the message has already been received, the message is not broadcast to another communication node. In this way, information on the failed link is propagated in the communication network.

According to the information that the link is unusable obtained in this way, the route selecting unit 24 of the communication node A determines, based on the topology information of the virtual communication network from which the links 3 and 8 have been removed, The shortest path from the communication node A to the communication node E is selected. The designated route information generating unit 25 of the communication node A uses ABH- as designated route information.
Create IJKLDE. Thus, the shortest route can be selected without using the disabled link.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing a failure example of a communication network for explaining the second embodiment of the present invention. In the first embodiment of the present invention, after the link 3 and the link 8 are disabled,
Before this information propagates to the communication node A, the communication node A sets ABCC- as the shortest path to the communication node E.
DE is selected. The second embodiment of the present invention solves this point.

The communication node A uses the virtual communication network topology information of the virtual communication network forming unit 23 before receiving the notification that the link 3 and the link 8 have become unavailable from the communication node A to the communication node A. A- as the shortest route to E
Select BCDE. When the communication node B arrives next time, the communication node B knows that the link 3 is unusable, so that the communication node A and the virtual communication network from which the link 2 and the link 3 have been removed are subjected to virtual communication. The network selecting unit 23, and the route selecting unit 24 of the communication node B.
Selects the shortest path from the communication node B to the communication node E. In this case, since BFGDE is the shortest path on the virtual communication network, the designated path information generation unit 25 of the communication node B sends the original designated path information AB
Of -CDE, the portion of BCDDE is BF-
Replaced by GDE, ie, ABFG
Let DE be new designated route information.

However, when the communication node F arrives at the communication node F, the communication node F knows that the link 8 is unusable, so that the communication nodes A and B and the links 1, 2, 3, 7,.
The virtual communication network excluding the link 10 and the link 8 is configured in the virtual communication network forming unit 23, and the route selecting unit 24 of the communication node F selects the shortest route from the communication node F to the communication node E. Since FHIJKLDE is the shortest path on the virtual communication network, the designated path information generation unit 25 of the communication node F Of the designated route information AB-F-G-D-E, the F-G-D-E portion is replaced by the F-HI-J-K-L-
What was replaced by DE, that is, ABFFHI
-JKLDE is set as new designated route information.

In this way, link 3 and link 8 are unusable, and the information is transmitted to communication node A, respectively.
The shortest path from the communication node A to the communication node E can be selected without knowing the communication node B and the communication node B.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a diagram showing a failure example of a communication network for explaining the third embodiment of the present invention. FIG. 4 assumes that, in the communication network shown in FIG. 9, when the link 3 between the communication node B and the communication node C becomes unavailable, a route is selected from the communication node A to the communication node E.

The fact that link 3 has become unusable is indicated in FIG.
Are notified to each other between the communication nodes A to L by the use availability notification unit 22 shown in FIG. 1 and reflected in the virtual communication network topology information of the virtual communication network forming unit 23 of each of the communication nodes A to L. .

According to the information that the link is unusable obtained in this way, the route selecting unit 24 of the communication node B determines the communication node A based on the topology information of the virtual communication network from which the link 3 has been removed. From the communication node E to the shortest path. The designated route information generating unit 25 of the communication node B uses ABBFHIJ as designated route information.
Create KLDE. Thus, the shortest route can be selected without using the disabled link.

(Summary of Embodiment) As described above, in the conventional route selection device, there is a case where a closed route is formed when an intermediate link is unavailable due to congestion or failure. This occurs because the communicating node performing the routing does not know any state other than the link directly connected to the communicating node. In the present invention, even when a link in the middle is unavailable due to congestion or failure, the communication node that has passed so far and the link related thereto and the virtual link that is known to be unavailable are removed. By selecting the shortest route again in a typical communication network, even if the link along the way becomes unavailable due to congestion or failure, it can select the route to the target destination correctly without selecting a closed route it can.

[0039]

As described above, according to the present invention,
Even when a link on the way is unavailable due to congestion or failure, it is possible to select a route to a correct destination. Thereby, the throughput of the communication network can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a communication node according to an embodiment of the present invention.

FIG. 2 is a diagram showing a failure example of a communication network for explaining the first embodiment of the present invention.

FIG. 3 is a diagram showing a failure example of a communication network for explaining a second embodiment of the present invention.

FIG. 4 is a diagram showing a failure example of a communication network for explaining a third embodiment of the present invention.

FIG. 5 is a diagram showing a conventional detour selection method.

FIG. 6 is a diagram showing an example of a communication network.

FIG. 7 is a diagram illustrating an example of a communication network in which a failure has occurred.

FIG. 8 is a diagram showing an example of another communication network.

FIG. 9 is a diagram showing an example of another communication network in which a failure has occurred.

[Explanation of symbols]

 1 to 16 link 20 route selection device 21 usability determination unit 22 usability notification unit 23 virtual communication network configuration unit 24 route selection unit 25 designated route information generation unit 30 communication device A to L communication node

[Procedure amendment]

[Submission date] January 13, 1999

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5 ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 27, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (5)

[Claims] 1. A communication node comprising a plurality of communication nodes and a plurality of links interconnecting the plurality of communication nodes, wherein a communication node at a transmission end selects a path from the transmission end to the reception end. In the route selection device provided, the communication node determines whether the link connected to the communication node is usable regardless of the presence or absence of communication, and determines the determination result of the determination unit between the plurality of communication nodes. And a means for virtually reproducing the topology of the communication network in accordance with the availability state notified by the notifying means. A means for selecting a route from the transmitting end to the receiving end on the communication network reproduced in (1). 2. The route selection device according to claim 1, wherein the means for virtually reproducing the topology of the communication network includes means for updating the topology whenever the availability state of the link is changed. 3. The means for virtually reproducing the topology of the communication network includes means for periodically updating the topology irrespective of a change in the availability state of the link.
A route selection device as described. 4. The route selection device according to claim 2, wherein the means for selecting a route includes means for sequentially selecting a route having a smaller number of relay communication nodes. 5. A means for confirming the availability of the designated route according to the received designated route information, and when there is a route newly recognized as unavailable by the means for confirming, the designated route is determined to be unavailable. 2. A route selecting apparatus according to claim 1, further comprising means for changing the recognized route so that the route is bypassed.