JP3011131B2 - Transmission path autonomous switching system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission path autonomous switching system, and more particularly to a connection oriented system using a protocol for performing a line connection using a source routing method for performing a route calculation based on topology information exchanged between nodes. The present invention relates to a transmission path autonomous switching system in a simple communication network.

[0002]

2. Description of the Related Art A conventional network of this kind, for example, A
In a connection switching system using a TM (asynchronous transfer mode) network, a detour path having the same quality as the main path is prepared for switching, or is switched only when a failure occurs.

For example, a centralized management device for centrally managing a network topology is prepared, and this centralized management device collects network topology information from all nodes, so that connection recovery can be performed with a low delay when a failure occurs. The preliminary route is calculated in advance for the purpose of.

[0004] In this state, the central management device also sets a backup route for the working connection when setting a certain connection, and when a failure occurs, transmits a switching control signal from the central management device to each node. Therefore, a method of switching connections at each node is adopted.

In addition, the centralized management device may adopt a method in which a bypass route is not set in advance, but when a fault occurs, a route is calculated to avoid the fault, and a bypass connection is set.

[0006] In a network of the type described above,
Since the central management device can manage the topology information of the network, it is possible to determine a backup route for the working route.

On the other hand, a technique which does not rely on a centralized control method is described in, for example, Japanese Patent Application Laid-Open No. 4-65942. According to this method, each node holds a plurality of predetermined backup routes and usually monitors the status of the backup routes. When a failure occurs, an appropriate You have selected a route.

According to the method described in Japanese Patent Application Laid-Open No. 6-62001, for example, when a failure occurs, a control frame is generated, and the control frame is transmitted to all connected paths. The node that has received this control frame has determined a backup route.

According to the method described in Japanese Patent Application Laid-Open No. Hei 7-115420, a management connection is set in advance from a node to which a connection source terminal is connected to all nodes in addition to a user connection. Incidentally, a method has been proposed in which when a failure occurs, the management connection is first restored autonomously in a decentralized manner, and then the network connection information is collected using the management connection to switch the connection.

[0010]

The above-described conventional connection switching apparatus is capable of providing a good-quality path as a detour path in switching due to a failure.
If the quality is the lowest within the range of the quality requested by the user when the connection is set, the same quality is used even after the switching. Conversely, when the connection quality is good before the switching, but when searching for a connection of the same quality after the switching, the scope of route selection is narrowed, and the probability of the detour route search is low.

[0011] The reason is that when a failure occurs, it is intended to restore the connection with the same quality as the connection that used the connection on the bypass route.

[0012] Further, the conventional connection switching device includes:
Since the switching is performed when a failure occurs, there is a disadvantage that when the connection is set, if the quality is the lowest in the range requested by the user, the user must perform communication of the same quality until the connection is disconnected. .

The reason is that there is no means to change the connection set within the range requested by the user until the connection is disconnected once, and the quality of the connection is within the range of the request. This is because they are not seen and are not switched.

An object of the present invention is to improve network utilization efficiency by setting a new quality after switching if the quality is within the range requested by the terminal in the path switching in the event of a failure, Also, even after the connection is set once, if a better quality route is found within the quality range requested by the user,
An object of the present invention is to provide a transmission path autonomous switching system capable of improving the quality of a user connection by switching paths.

[0015]

According to the present invention, a connection-oriented communication network using a protocol for performing a line connection using a source routing method for performing a route calculation based on topology information exchanged between nodes. The transmission path autonomous switching system according to claim 1, wherein the node is a request quality holding unit that holds required quality information having a predetermined range of quality requested by a terminal at the time of connection setting, and the required quality in response to the occurrence of a connection failure. A transmission path autonomous switching system, comprising: a path calculation means for calculating a detour path having a quality within a required quality range held in a holding means; and a means for switching to a detour path obtained by the path calculation means. Is obtained.

[0016] The node further activates the route calculation means at regular time intervals, and searches for a route having a better quality than the currently operating route within the range of the quality requested by the terminal. Wherein the route is switched to the search route by the switching means when the route search is completed, and the quality is information indicating a transmittable band of the route. And

The operation of the present invention will be described. When searching for a detour route in the event of a fault, the search is performed within the range of the line quality requested by the calling terminal. Can increase the establishment.

Further, if a different route is calculated periodically and the obtained route has a better quality than the current route, the route is switched to the better route so that a connection of better quality can always be provided to the user. .

[0019]

Next, embodiments of the present invention will be described with reference to the drawings.

First, a description will be given with reference to FIG. FIG.
As an example of realizing a network using a protocol for performing line connection using a source routing method for performing a route calculation based on topology information exchanged between nodes in the M, a PNNI (Priv
ate Network-Network Interface) Indicates a network based on the protocol.

Here, the PNNI protocol relates to a routing technique for exchanging topology information of a network and a signaling technique for connecting a connection.

First, an outline of a routing technique, which is a mechanism for exchanging network configuration and topology information using a PNNI protocol, will be described.

FIG. 3 shows six nodes (301, 302,
303, 304, 305, 306), and between the respective nodes 301-302, 301-304, 30
2-303, 302-305, 303-304, 303
-306, 304-305, and 305-306 are assumed to be connected by a link.

In the routing, network topology information is exchanged by exchanging routing messages between the node and all adjacent nodes. Here, when the exchanged topology information is different from the topology information table of the own node, it is updated when it is determined that the topology information needs to be updated according to the PNNI rule described above.
Then, when it is necessary to transfer the received topology information to another node, the topology information is transmitted (flooding).

In this way, the nodes in the network grasp the information on the topology of all the nodes. For example, at node 303,
When the topology change is recognized, the information is notified to the nodes 302, 304 and 306 by 401 to 403 in the first stage as shown in FIG.
Notification is sent to the nodes 301 and 305 at 04 to 405.

On the other hand, signaling is a technique in which, when a setup message is received from a transmitting terminal at a node to which the transmitting terminal is connected (hereinafter referred to as a starting node), a connection is set based on a route to a receiving terminal. At this time, as described above, since the entire topology in the network can be grasped by the routing, the route is determined. Then, the node on the route information notifies the next node of the setup message in the order calculated by the start node.

FIG. 1 is a functional block diagram showing an embodiment of the present invention. FIG. 1 shows main components provided in each node. As shown, the node comprises a routing means 101 and a signaling means 1
02, a route calculation unit 103, a switching unit 104, a topology information database 111, a route information database 112, and a required quality database 113.

The routing means 101 performs the above-described A
It has a protocol with the same specifications as the PNNI routing protocol specified by TM Forum. This routing means 101 exchanges topology information by exchanging routing messages between its own node and adjacent nodes. If this exchanged topology information is stored in the topology information database 111 of the own node,
In contrast, when it is determined that the information needs to be updated according to the rules, the content of the topology information database 111 is updated. Then, if there is a need for flooding, flooding is performed.

The signaling means 102 performs two main processes. One is a process of normal connection setting or disconnection in response to a request from the terminal, and the other is a process of disconnecting and resetting the connection when a failure occurs in the network. Since these processes have different processing functions depending on the positions of the nodes on the connection route, the nodes will be classified and described as a start node, an end node, and other nodes (relay nodes).

First, the first process of the signaling means 102, ie, the process of connection setting or disconnection by a request from the calling terminal will be described.

When the start node receives a setup message related to the route setting from the calling terminal, the signaling means 102 notifies the route calculation means 103 that the route calculation is necessary. At this time, the required quality information, which is the content of the setup message, is set in the required quality database 113. Signaling means 102
Performs connection processing of the connection in its own node based on the path information of the path information database 112 set by the path calculation means 103, and transmits a setup message to the next connection destination node on the path information. I do.

When the relay node and the end point node receive the setup message, the relay node and the end node perform connection processing of the own node,
Based on the route information in the setup message, a setup message is transmitted to the next node or the terminating terminal to perform connection setting.

When all nodes receive a release message related to a route disconnection in response to a request from a terminal, the node sends a release message to the next connection destination node on the route, and sends a release message to the corresponding node. Perform connection disconnection processing.

Next, a description will be given of a second operation of the signaling means 102, which is a processing operation for disconnecting and resetting a connection when a failure occurs in the network.

First, when the start node recognizes a failure, it notifies the route calculation means 103 that route calculation is necessary while maintaining the connection to the calling terminal. The signaling means 102, based on the route information of the route information database 112 set by the route calculating means 103,
The connection process of the own node is performed, and a setup message is transmitted to the next connection destination node on the route information, and as soon as the connection is secured, the switching unit 104 is requested to switch.

Signaling means 10 in relay node
2 receives the setup message for the detour route setting, performs connection connection processing in its own node, transmits a setup message to the next node based on the route information in the setup message, and performs connection setting. I do.

Signaling means 10 at the destination node
2 receives the setup message for setting the bypass route, and requests the switching unit 104 to switch between the secured route and the currently used route.

When transmitting a message, a unique connection identifier is assigned in the network and transmitted.

The route calculation means 103 calculates a route with reference to the address of the called terminal and the topology information database 111. As an example of the route calculation method, a calculation is performed in consideration of the required quality of the required quality database 113 using a Dijkstra algorithm for calculating the shortest route, and the result is set in the route information database 112. In this case, it is not necessary that the quality of the currently operated connection be the same.

The switching unit 104 switches between the connection of the currently used route and the connection secured by another route calculation. Specifically, the switching is performed by connecting the newly secured connection and the connection of the terminal. When switching, which connection corresponds to which connection uses a connection identifier.

FIG. 2 is a functional block diagram showing another embodiment of the present invention. As shown, a timer means 105 is added to the block of FIG. With the addition of the timer means 105, the signaling means 10
The processing of 2 is as follows.

The signaling means 102 sets the switching connection based on the timer means 105 in addition to the processing described in the example of FIG. Based on the notification from the timer means 105, a search for a path of better quality is periodically performed within the required quality range for the currently operating connection. This process is performed at the start node.

That is, after being notified of the periodic timing from the timer means 105, it requests the path calculation means 103 to search for a path of good quality for the currently operated connection. Here, if a new route can be found, a setup message for a detour route is transmitted, and after the route is secured, the switching means 10
Request switching to 4. A process as shown in FIG. 5 is performed as a process example at this time.

First, in process 402, the timer 105
To see if has timed out. When a timeout occurs, in the next process 403, it is confirmed whether or not the corresponding connection exists. Here, if the operating connection has been disconnected, this process ends, and if it is still in operation, another route calculation is performed in process 404. This is requested to the route calculation means 103.

Then, another route information is obtained from the route information database 112 holding the calculation result,
In processing 405, the quality of the connection currently used and the quality of another path are compared. Here, if the quality of the other path is better, a setup message for another path is transmitted in processing 406, and connection setting processing is performed.

Then, after the connection is set,
In process 407, switching is performed, and in process 408, the connection of the originally used path is disconnected. on the other hand,
If the quality of the alternative route is determined to be poor in the process 405, the process returns to the process 402.

In this way, another route of the connection that is currently present is calculated for each certain period of time, and if a route of better quality can be searched from the current route, a route switching process is performed.

Next, with reference to FIGS. 6 to 8, a specific example of the overall processing operation in the embodiment of the present invention will be described with reference to the AT of FIG.
This will be described using the M network.

First, a case where the originating terminal 311 newly connects to the destination terminal 312 will be described with reference to FIG. In this operation, the originating terminal 311 transmits a setup message to the node 301 serving as the start node. Node 3 that received the setup message
01 signaling means 102
To get route information. As an example, node 30
It is assumed that a path 231 in the order of 1,302,303,306 is obtained.

On the basis of this route information, the signaling means 102 of the node 301
02 sends a setup message. Node 30
2 corresponds to a relay node, the signaling means 102 performs connection setting processing and transmits a setup message to a node 303 which is the next node on the route.

Similar processing is performed at the node 303.
Similarly, the node 306, which is the end point node, performs connection setting processing and transmits a setup message to the receiving terminal 312. The receiving terminal 312 performs a connection procedure upon receiving the setup message, and transmits a connect message to the calling terminal 311 upon completion.

Accordingly, nodes 306, 303, 30
A connect message is notified, such as 2,301. Finally, the originating terminal 311 is notified that the connection has been established.

Next, the operation when a failure occurs will be described with reference to FIG.
The explanation will be made with reference to FIG. When a failure occurs in the link between the nodes 302 to 303, the notification is eventually sent to the start node 301 and the end node 306. Start node 3
In the signaling process 102 of 01, since the failure has been recognized, a request is made to the detour route calculation means 103 of the own node for a route calculation excluding the failure.

At this time, the detour route calculation means 103
The route is calculated based on the required quality information having a wide range in the required quality database 113. Then, the connection is set based on the obtained route information. Node 30 as an example
It is assumed that a path 322 in the order of 1, 304, 305, 306 has been obtained. In this case, the signaling means 102 of the node 301 determines the next node 3 based on the route information.
04 and sends a setup message.

Since the node 304 corresponds to a relay node, its signaling means 102 performs connection setting processing, and the node 305 which is the next node on the route.
Send setup message to Similar processing is performed in the node 305.

When the end point node 306 receives this message, the switching means 104 switches the connection. Then, the connect message, which is a response to the setup message, is transmitted to the nodes 305, 304, 30.
The connection is switched at the start node 301 notified in the order of 1.

Then, in order to disconnect the connection path originally used, a release message is transmitted to the next node 302 on the path of the original connection, and the release message is similarly notified in the order of the nodes 303 and 308. Finally, the original path is disconnected.

The operation when a route of good quality is found will be described with reference to FIG. In the start node 301, the route 322
, Different route of good quality is calculated by the route calculating means 103. If the obtained route has better quality than the current route, a switching process is performed. As an example, it is assumed that route information in the order of the nodes 301, 304, 303, and 306 has been obtained.

In this case, the signaling means 102 of the node 301 determines the next node 30 based on the route information.
4 sends a setup message. Node 304
Corresponds to the relay node, so that its signaling means 1
In 02, a connection setting process is performed, and a setup message is transmitted to the node 303 which is the next node on the route. Similar processing is performed at the node 303.

When the terminal node 306 receives this message, the switching means 104 switches the connection. Then, the connect message as a response to the setup message is transmitted to the nodes 303, 304, and 30.
The connection is switched at the start node 301 notified in the order of 1. Then, in order to disconnect the connection path originally used, a release message is transmitted to the next node 302 on the path of the original connection, and the release message is similarly notified in the order of the nodes 303 and 308. Originally, the original path is disconnected.

Hereinafter, the operation of the embodiment will be specifically described using the used band as an example of the quality request information.

From the calling terminal, the line to be connected is
I would like to use 40Mbit / S, but at least 20M
If bit / S is required to be ensured, these two pieces of information are added as contents of the setup message and transmitted to the start node. The transmitting node stores this information in the required quality database. The sending node must establish a connection by this setup message, and this connection is searched based on the topology information database constructed by the routing means.
It is assumed that the contents of the topology information database regarding the remaining available bandwidth are as shown in FIG.

The result of calculating the shortest path by the Dijkstra algorithm is 301-302-303-30.
In the case of route 6, the bandwidth used for this connection is 30 Mbit / S, which is the minimum value of this route, and a connection to the end node is set based on this value. In other words, the portion indicated by * in the table will have a value reduced by 30 Mbit / S because 30 Mbit / S will eventually be secured in each node.

The table of FIG. 9 is updated through the routing means as needed when there is a change due to connection being connected or disconnected.

Here, when a failure occurs in the link between the nodes 302 and 303, the calculation of the Dijkstra algorithm excluding this link is performed. The calculation at this time is 3
01-304-305-306. In this case, the bandwidth used is 20 Mbit / S according to FIG. 9, which is lower than the originally set 30 Mbit / S. However, according to the required quality database, this connection may be 20 to 40 Mbit / S. It can be seen that this route also satisfies the request of the calling terminal, so that a setup message for using this route is transmitted.

On the other hand, when the network situation changes, 30
Assume that the link between 3 and 304 has changed to 100 Mbit / S. At the start node, the shortest route is obtained by using a route obtained by partially removing the current route.
As one of the shortest paths, 301-304-303-3
06 is calculated, 50 Mbi from the table in FIG.
It can be seen that t / S can be secured, and from the required quality database, it is 20 to 40 Mbit / S.
A connection that secures 40 Mbit / S, which is the maximum required quality, is set. Then, after a new connection can be secured, by performing switching, a connection of better quality can be obtained.

[0067]

As described above, the autonomous switching system of the present invention has the following effects. The first effect is that a detour path at the time of occurrence of a failure can be flexibly searched. If a better quality route can be provided in the detour route, it is provided, and the probability of searching for the detour route can be increased. The reason is that in searching for a detour route, a route search is performed with a certain quality requested by the terminal.

The second effect is that a connection of better quality can be provided to a user using the connection. The reason is that another route is calculated periodically, and if the obtained route has better quality than the current route, the route can be switched.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of another embodiment of the present invention.

FIG. 3 is a diagram showing a configuration example of a network using the present invention.

FIG. 4 is a diagram showing an operation of flooding.

FIG. 5 is a flowchart showing the operation of the block in FIG. 2;

FIG. 6 is a message flow example in connection setting.

FIG. 7 is an example of a message flow of a switching process when a failure occurs.

FIG. 8 is an example of a switching processing flow when a path with better quality is found.

FIG. 9 is a diagram showing an example of the contents of a required quality database 113 in FIGS.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Routing means 102 Signaling means 103 Route calculation means 104 Switching means 111 Topology information database 112 Route information database 113 Quality request database 301-306 Nodes 311-212 Terminal 231 Connection setting route 322 Detour route 323 when failure occurs Good quality Alternate route 401-405 flood message if found

Claims (2)

(57) [Claims] 1. A transmission path autonomous switching system in a connection-oriented communication network using a protocol for performing a circuit connection using a source routing method for performing a path calculation based on topology information exchanged between nodes, A request quality holding unit for holding required quality information having a predetermined range of quality requested by a terminal at the time of connection setting; and a required quality range held by the required quality holding unit in response to occurrence of a connection failure. Path calculating means for calculating a detour path having a quality within, switching means for switching to a detour path obtained by the path calculating means, and activating the path calculating means at regular time intervals,
Within the quality range required by the
Means for searching for a route of better quality, and when the route search is successful,
Transmission path autonomous switching system is characterized in that so as to form a switch to the path. Wherein said quality transmission path autonomous switching system according to claim 1, wherein the information indicating the allowable communication bandwidth of the path.