Distributed control of telecommunication network for setting up an alternative communication path

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a communication network control method, and more particularly to a method in which communication control is distributed at each node in an asynchronous transfer mode network or a synchronous transfer mode network having an arbitrary structure.

【0002】

In recent years, as a technology to realize a high-speed / broadband integrated network (B-ISDN) aiming at a wide range of multimedia services, a control method for an ATM (Asynchronous Transfer Mode) network or an STM (Aynchronous Transfer Mode) network. Research is being actively carried out.

【0003】

When a node or link in such a network fails, it is necessary to set a detour path that bypasses the failed node or link.

【0004】

[Conventional technology]

In a conventional communication network, the network control center centrally monitors the line status, and when a node notifies a failure, it searches for a path that bypasses the node or link where the failure occurred. Lines have been switched, but in such a centralized control method, there is a problem that it takes time to switch paths and the burden on the network control center is heavy.

【0005】

Therefore, in an ATM network or STM network as shown in FIG. 9, for example, when a failure occurs in the illustrated node N5 or its link, if this failure is detected by the downstream node N8, this node By flooding from N8, each node is distributed and autonomously searches for a detour path.

【0006】

That is, in this flooding, the node N8 that detects the failure sends a detour path search message that identifies the start point node of the target detour path with its own node as the end point node of the detour path, and any detour path search message connected to this node N8. If the node sent to the link in the direction and received this detour path search message is not the starting node, include the information of the own node to indicate that the detour path search message is the node through which the node has passed. The detour path search message is forwarded to the link in all directions connected to the node.

【0007】

Then, if the own node is the starting node, the node that receives this detour path search message sends the detour path setting message that is included in the detour path search message and follows the node that the message has passed through in the reverse direction. Send to the end node of. In this way, the detour path of node N2 node N4 node N8 shown by the thick line in the figure is searched (determined).

【0008】

[Problems to be Solved by the Invention]

However, with the determination of the detour path in this way, a virtual path identification number (hereinafter referred to as VPI) in each link is further set, and this VPI is the starting point of the above in the original virtual path. Must be associated with the VPI set on the outgoing link. That is, the VPI table of each node related to the detour path must be changed.

【0009】

When switching by flooding in this way, depending on how the VPI table is changed, a large amount of information may need to be transferred, and the detour path switching time may become long, resulting in the problem that recovery from the failure cannot be dealt with. ..

【0010】

Therefore, according to the present invention, when a failure occurs in any node or link in the asynchronous transfer mode or synchronous transfer mode network having an arbitrary structure, each node is distributed and flooded from the node that detects the failure. The purpose of the communication network control method for searching for a detour path for the faulty node or link is to reduce the amount of information for switching the detour path as much as possible.

【0011】

[Means and Actions for Solving Problems]

The communication network control method according to the present invention for solving the above problems is conceptually shown in FIGS. 1 and 2.

【0012】

In the present invention, when a failure occurs at node B in the network as shown in FIG. 2 and a failure is detected at node C, a detour path is provided by flooding from the failure detection node C on the downstream side of node B. Perform a search (Fig. 1).

【0013】

In this way, the detour path for switching the virtual path passing through node A node B node C to node A node X node C by flooding is first searched. The intermediate node X is shown as a general term for the meaning including one or more nodes.

【0014】

After that, node C, which is a downstream node of the detour path, determines the surplus transmission capacity, the number of free VPIs corresponding to this transmission capacity, and the free VPI that is the starting point in these free VPIs, and determines the intermediate node X as a message. Send to. (Figure 1). That is, since the extra transmission capacity is known by flooding in this downstream node C, this transmission capacity and the number of free VPIs corresponding to this transmission capacity are determined, and the starting point of these free VPIs is determined. Only the free VPI is determined and sent as a message to reduce the amount of information to be transferred.

【0015】

In the message sent to the intermediate node X in this way, the free starting point VPI is taken out in this intermediate node X, the VPI table in the intermediate node X is changed based on this free starting point VPI, and the node X C Switch the path between.

【0016】

At the same time, in order to switch the path between node A X, the message from the intermediate node X is sent as a message by changing only the VPI with a free start point to match the most upstream node A among the messages from the downstream node C. (Figure 1).

【0017】

In this way, even if there are several intermediate nodes, the same VPI table is changed, and the VPI is changed to a free starting point to the next upstream node, and a transfer message is sent.

【0018】

Finally, the most upstream node A that receives such a message extracts the transmission capacity, the number of free VPIs, and the free VPIs at the start point in this message, and further gives them a predetermined switching order of VPIs to give the VPIs of the own node. Change the table and switch the detour path of node A node X node C to connect (Fig. 1).

【0019】

However, the predetermined switching order may be the order of priority of VPI or the order of transmission capacity of VPI. Further, when there are VPIs having the same transmission capacity, path connection may be performed in the order of VPIs.

【0020】

Furthermore, in the case of Fig. 1, the ATM network was taken as an example, but in the case of the STM network, each node in the detour path searched by flooding faces each other according to the message transferred along this detour path. The input / output table of the own node can be changed so that the time slots in the links between the respective nodes match, and the detour path can be switched and connected.

【0021】

[Example]

FIG. 3 shows an example of the communication network control method according to the present invention, and in this embodiment, the same network configuration as in FIG. 2 is used for simplification of the description.

【0022】

First, as the VPI tables in node A and node C in this embodiment are shown in FIGS. 4 (B) and 4 (A), respectively, the input VPI in node A is VPI "0001" to "0004". When the network is operating normally, the path of node A node B node C is formed, so the output VPI of node A and the input and output VPI of node C also have the same VPI number. It is set.

【0023】

In such a state, when a failure occurs in node B or its link as described above, the detour path of node A node X node C is searched by flooding from node C that detects this. ..

【0024】

In the search for such a detour path, the surplus transmission capacity common to this detour path is also searched, so if this surplus transmission capacity is 200 Mb / s, node C to node X are also searched. The total capacity of the message sent to is 200Mb / s. If the common surplus transmission capacity cannot always be obtained with the same value at the node C, the capacity lower than the transmission capacity and closest to the transmission capacity is selected.

【0025】

Then, in this embodiment, the total transmission capacity of the bypass path is set to 200 Mb / s. Therefore, in order to obtain this transmission capacity, the VPI of the outgoing VPI of the node C is obtained as shown in FIG. 4 (A). If "0003", "0002", and "0004" are selected, it corresponds to 200 Mb / s. In this case, the number of switching VPIs is "3", so the number of switching VPIs is included in the message from node C. Is set to "3".

【0026】

Since it is necessary to make the input VPI on the detour path of node C correspond to the three VPIs "0003", "0002", and "0004" selected in this way, it is shown in Fig. 4 (A). As shown in the figure, free VPIs "1001", "1002", and "1003" from node X to node C are assigned as shown in the figure. However, at this time, including all the update tables in Fig. 4 (A) in the message increases the amount of information, so in this example, the youngest free VPI "1001" is used for the VPI "0003" of 100 Mb / s. Set as a free starting point VPI, include it in the message and send it to node X.

【0027】

As shown in Fig. 4 (A), if there are VPIs with the same capacity, prioritize them as shown in the figure, and by doing so, it is sufficient to select only the number of switching VPIs from the starting point free VPIs.

【0028】

In this way, node C leaves the number of switching VPIs, the total transmission capacity to be switched, and the starting point VPI of the free VPI in the message and sends it to node X. In this node X, when the message is received, the number of switching VPIs in the message and the number of switching VPIs in the message are sent. Allocate input free VPIs "2001" to "2003" from the transmission capacity to node A node X, and output free VPIs "1001" to "1003" from the start point free VPI in the message to node X node C ( These correspond to the input free VPIs "1001" to "1003" of node C), and the VPI table is converted as shown in the figure.

【0029】

And this node X leaves the number of switching VPIs and the total transmission capacity as they are, and since the starting point free VPI changes by converting the VPI table, change only this changed starting point free VPI to VPI "2001" and upstream. It will be sent to node A.

【0030】

When this message is received at node A, the number of switching VPIs is "3", the total capacity is "200Mb / s", and the free starting point VPI is "2001", as shown in Fig. 4 (B). As a result, VPI "0003", which is the largest transmission capacity of node A, corresponds to output VPI "2001", and this VPI "2001" is converted to VPI "1001" by node X. By connecting to C, node C is connected to VPI "0003", which has the largest transmission capacity, so the VPI of the detour path from node A to node C is the same. This also applies to VPIs "0002" and "0004".

【0031】

However, in this case, since the priority is determined as described above, VPI "0002" is set with priority over VPI "0004" even if the transmission capacity is the same 50 Mb / s, and the detour path is set. Therefore, each correspondence can be obtained.

【0032】

By converting the VPI table of each node in this way, the switching connection is completed.

【0033】

In the above examples, VPI conversion is dealt with for the ATM network, but switching connection can be performed for the STM network from another viewpoint. That is, in the network as shown in FIG. 3, a failure occurred at node B, this failure was detected at node C, and a detour path was searched for by flooding. As a result, the node A node X node C was passed through. The detour paths are searched, and when it is found that three of these detour paths can be recovered, the input / output table conversion as shown in FIG. 5 is first performed at the node C.

【0034】

That is, in the path from node B to node C to be restored, three ports (time slot numbers on the input side; 3,4,5) are used in order from the smallest time slot number, and the port "1" on the input side of the bypass path is used. Change the I / O table so that it is assigned to the time slots 3, 4 and 5.

【0035】

This change is made by transferring the SOH (section overhead) in the STM frame shown in Fig. 8 to the node X with the detour path configuration instruction and the number of recoverable paths.

【0036】

In node X, as shown in FIG. 6, the time slot on the input side, that is, the node A side is set with respect to the time slot on the output side, that is, the node C side, and such routing information is obtained. Is also placed on the STM frame in Fig. 8 and sent to node A.

【0037】

Then, when the route setting information from the node X is received in the STM frame at the node A, the time slot on the output side, that is, the node X side, which is not used for the input side with a small time slot number (2,3,4). Change the input / output table as shown in Fig. 7 so that the numbers (10,11,12) are assigned. In this way, in the STM network, the detour path switching connection is realized by matching the time slots in the detour path.

【0038】

[Effect of the invention]

As described above, according to the communication network control method according to the present invention, it is based on the surplus transmission capacity for changing the VPI table in each node of the detour path searched by flooding by a message and the transmission capacity thereof. Since it is configured to send the number of free VPIs to be switched and the VPI that is the starting point in the free VPI, it is not necessary to send all the necessary VPI change tables by forming the detour path, and the detour path can be switched quickly. Since it can be done, the time for disaster recovery is shortened.

【0039】

Also, in the STM network, the input / output table at each node of the searched detour path is changed so that the time slots at the links between the opposing nodes match, so the detour is performed with a small amount of information. The path switching connection can be performed quickly.

[Simple explanation of drawings]

[Figure 1]

It is a flowchart which showed the communication network control system which concerns on this invention in principle.

[Figure 2]

It is a figure which showed the network example of the communication network control system which concerns on this invention.

[Fig. 3]

It is a figure which showed the Example (ATM network example) of the communication network control system which concerns on this invention.

[Fig. 4]

It is a figure which showed the example of the update of the VPI table of the ATM network performed in this invention.

[Fig. 5]

It is a figure which showed the table change example of the node which transmits the message of the detour in the STM network in this invention.

[Fig. 6]

It is a figure which showed the updated table in the intermediate node of the detour path at the time of the failure of the STM network in this invention.

[Fig. 7]

It is a figure which showed the table change example of the node which finally receives the message in the detour path when the STM network fails in this invention.

[Fig. 8]

It is a figure which showed the structural example of the frame in the STM network in this invention.

[Fig. 9]

It is a network diagram for demonstrating the conventional general flooding.

[Explanation of symbols]

A, B, C, X nodes In the figure, the same reference numerals indicate the same or corresponding parts.