JP2732775B2 - Communication line switching control device and communication line switching control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication line switching control device and a communication line switching control method, and more particularly to a system for performing data communication using a plurality of communication lines when a failure occurs in any one of the communication lines. The present invention relates to an apparatus and a method for controlling switching of a communication line.

[0002]

2. Description of the Related Art Japanese Patent Laying-Open No. 3-136533 discloses a configuration control method for a distributed system that performs data transmission while performing load distribution using a plurality of communication lines. In this control method, the system is configured such that each module monitors abnormalities of a plurality of communication lines by itself, and when an abnormality occurs in a certain communication line, data communication is continued by the remaining normal communication lines.

Japanese Patent Laid-Open Publication No. Hei 3-127528 discloses an automatic network communication line in which an alternative line is prepared in advance and the active communication line is switched to the alternative line when a failure occurs in the active communication line. A switching control method is disclosed.

In these control systems, the communication line is automatically switched when a communication failure occurs, and it is not necessary for an application program or an operator to be aware of the switching of the communication line.

[0005]

However, in the above-mentioned conventional control method, it is considered that an alternative line is selected while taking into consideration the load distribution of the remaining normal communication lines except for the communication line in which a failure has occurred. Absent. Also, no consideration is given to how to return data communication from the substitute line to the original communication line when the failed communication line is restored.

[0006] Therefore, the communication load of some normal communication lines increases due to the switching of communication lines, and the performance of data communication using the communication lines may be extremely deteriorated.

[0007] In order to avoid such a problem, it is necessary to delegate control for performing data communication while considering load distribution of a communication line to an application program. In this case, it is necessary to consider switching of the communication line when developing the application program, and the productivity is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a system for performing data communication using a plurality of communication lines, in the event that a failure occurs in any one of the communication lines, taking into consideration the load distribution of the remaining normal communication lines. A communication line switching control device and a communication device capable of performing line switching and automatically returning data communication to the original communication line after the recovery from the failure, and performing control of the line completely without the application program being conscious. An object of the present invention is to provide a line switching control method.

[0009]

(1) First invention A communication line switching control device according to a first invention comprises a plurality of line control means and line information storage means.

[0010] The plurality of line control means are provided corresponding to the plurality of communication lines, respectively, and each is connected to the corresponding communication line. A plurality of line information corresponding to the plurality of line control units are stored in the line information storage unit.

Each line information stored in the line information storage means corresponds to detour line information indicating the other communication line when the corresponding communication line is detouring data communication relating to the other communication line. When the data communication relating to the communication line is detouring to another communication line, the information includes detour destination line information indicating the other communication line.

Each of the plurality of line control means controls the data communication and the data detour processing on the corresponding communication line by referring to and updating the detour line information and the detour destination line information stored in the line information storage means. I do.

(2) Second invention In the communication line switching control device according to the second invention,
Each of the plurality of line control means, when a failure occurs in the corresponding communication line, refers to the detouring line information stored in the line information storage means and selects a communication line with a small communication load among normal communication lines. Determined as a detour destination line, diverts data communication to the detour destination line, and updates detour line information and detour destination line information stored in the line information storage means, after the failure of the corresponding communication line is recovered The data communication by the detour destination line is returned to the corresponding communication line by referring to the detour destination line information stored in the line information storage means, and the detour line information and the detour destination line information stored in the line information storage means are returned. Update.

(3) Third Invention The communication line switching control device according to the third invention further includes a plurality of transmission data storage means. The plurality of transmission data storage means are provided corresponding to the plurality of communication lines, respectively, and store data to be transmitted to the corresponding communication lines.

Each line information stored in the line information storage means further includes transmission data information indicating a position where the data being transmitted or transmitted in the corresponding transmission data storage means is stored and a transmission state.

Each of the plurality of line control means, after the failure of the corresponding communication line is recovered, refers to the corresponding transmission data information stored in the line information storage means and performs data communication by the detour destination line. Return to communication line.

(4) Fourth Invention In the communication line switching control method according to the fourth invention, a plurality of line information respectively corresponding to a plurality of communication lines are stored in the line information storage means. Each line information includes a detouring line information indicating the other communication line when the corresponding communication line is bypassing the data communication regarding the other communication line, and the data communication regarding the corresponding communication line is transmitted to the other communication line. In the case of a detour, it includes detour destination line information indicating the other communication line.

[0018] Then, by referring to and updating the detour line information and the detour destination line information stored in the line information storage means, data communication and data detour processing for the corresponding communication line are controlled.

(5) Fifth Invention In the communication line switching control method according to the fifth invention, when a failure occurs in any of the plurality of communication lines, the detour line information stored in the line information storage means is stored. , A communication line with a small communication load among normal communication lines is determined as a detour destination line, the detour destination line is diverted to data communication, and the detour line information and the detour destination stored in the line information storage means. Update line information.

After the failure of the communication line is recovered, the data communication by the detour destination line is returned to the original communication line by referring to the detour destination line information stored in the line information storage means, and stored in the line information storage means. Update the detoured line information and the detour destination line information.

[0021]

(1) First invention In the communication line switching control device according to the first invention,
Since the current detouring line information and the detouring destination line information are stored in the line information storage means, each communication line determines which other communication line is detouring, and the data communication regarding each communication line is Each line control means can recognize which communication line the device is bypassing. Further, each line control means can recognize the number of other communication lines bypassing each communication line.

Accordingly, when a failure occurs, each line control means switches the communication line while taking the communication load of the communication line into account and performs the detour processing, and after the recovery from the failure, terminates the detour processing and returns the communication line to the original state. be able to.

(2) Second invention In the communication line switching control device according to the second invention,
Since the communication line with a small communication load is determined as the detour destination line based on the detouring line information, the communication load on some communication lines does not increase due to the occurrence of a failure.

(3) Third invention In the communication line switching control device according to the third invention,
Since each line information stored in the line information storage means further includes transmission data information indicating a position and a transmission state where the data being transmitted or transmitted in the corresponding transmission data storage means is stored, a failure of the communication line may occur. After recovering,
By referring to the transmission data information, data communication by the detour destination line can be returned to the original communication line.

(4) Fourth Invention In the communication line switching control method according to the fourth invention,
Since the current detouring line information and the detouring destination line information are stored in the line information storage means, each communication line determines which other communication line is detouring, and the data communication regarding each communication line is It is possible to recognize which communication line is being bypassed. Also, the number of other communication lines bypassing each communication line can be recognized.

Therefore, when a failure occurs, the detouring process can be performed by switching the communication line while considering the communication load of the communication line, and after the recovery from the failure, the detouring process can be terminated to return the communication line to the original state.

(5) Fifth Invention In the communication line switching control method according to the fifth invention,
Since the communication line with a small communication load is determined as the detour destination line based on the detouring line information, the communication load on some communication lines does not increase due to the occurrence of a failure.

[0028]

FIG. 1 is a block diagram showing the configuration of a communication line switching control device according to an embodiment of the present invention.

This communication line switching control device includes a line control processing unit 1, a transmission data file unit 2, a line management table 3, and an application program unit 4. The line control processing unit 1 is connected to n sets of communication lines L1, L2,..., Ln.

The line control processing unit 1 includes n sets of communication circuits L
, Ln, and n line control processing modules 11, 12,..., 1n. Each line control processing module is connected to a corresponding communication line. The transmission data file unit 2 includes n sets of communication lines L1, L2,
, N transmission data files 21 and 22 corresponding to Ln
2, ..., 2n. Each transmission data file is connected to a corresponding line control processing module.

The application program section 4 includes a plurality of application programs 41, 42,..., 4m. Each application program is created as needed. Each application program requests the corresponding communication line for data transmission by writing the transmission request data in the transmission data file. Thereby, data is transmitted to the corresponding communication line. For example, when requesting data transmission from the communication line L1, the transmission request data is written in the transmission data file 21.

As shown in FIG. 2, each line control processing module in the line control processing unit 1 includes a data transmission / reception line monitoring processing unit 1a, a line recovery processing unit 1b, a line failure processing unit 1c, and a transmission data creation processing unit 1d. And a reception processing application program 1e.

The data transmission / reception line monitoring processor 1a controls transmission / reception of data relating to a corresponding communication line, and monitors the state of the communication line. Line recovery processing unit 1
In step b, after the failure of the corresponding communication line is recovered, the recovery processing is performed with reference to the line management table 3 and the content of the line management table 3 is updated. When a failure occurs in a corresponding communication line, the line failure processing unit 1c performs a detour process described below with reference to the line management table 3 and updates the contents of the line management table 3.

The transmission data creation processing unit 1d refers to the line management table 3, creates transmission data based on the transmission request data stored in the corresponding transmission data file, and gives it to the data transmission / reception line monitoring processing unit 1a. . The reception processing application program 1e performs a predetermined reception process on the reception data provided from the data transmission / reception line monitoring processing unit 1a.

Here, a communication line corresponding to each line control processing module, that is, a communication line controlled by each line control processing module is called a self-control line. For example, for the line control processing module 11 of FIG. 1, the communication line L1 is its own control line, and for the line control processing module 12, the communication line L12 is its own control line.

A communication line requested by an application program to transmit data is called a transmission request line. For example, when the application program 42 writes the transmission request data in the transmission data file 21, the communication line L1 becomes the transmission request line.

When a failure occurs in a certain communication line,
Data transmission to the failed communication line is performed by bypassing another communication line in which no failure has occurred. This is called a bypass process. In this case, the failed communication line is referred to as a detour line, and the communication line on which data transmission to the failed communication line is bypassed is referred to as a bypass destination line.

Referring back to FIG. Line management table 3
Includes a line identifier field (hereinafter, referred to as a line ID field) 31, a transmission data information field 32, a detour line information field 33, and a detour destination line information field 34 for each communication line.

The transmission data information field 32 includes a transmission record pointer field 32a and a transmission status field 32b. Detour line information field 33
Is the number of detouring lines field 33a and the detouring line I
It consists of a D field 33b. The bypass line information field 34 includes a bypass flag field 34a and a bypass line ID field 34b.

The line ID field 31 stores the line ID of the communication line to be managed. The transmission record pointer field 32a stores a transmission record pointer. The transmission record pointer indicates the record position where the currently transmitted transmission request data or the last transmitted transmission request data among the transmission request data stored in the corresponding transmission data file is stored. The transmission status field 32b stores the transmission status of the transmission request data, ie, “transmitting” or “transmitted”.

The number of detouring lines field 33a stores the number of detouring lines for which detour processing is performed by the communication line out of the failed communication lines. In the detour line ID field 33b, the line ID of the detour line that performs detour processing by the communication line is stored.

In the detour destination flag field 34a, a flag indicating "during detour" is set when the data transmission requested by the communication line is diverted to another communication line. The detour destination line ID field 34b stores the line ID of the detour destination line when data transmission requested by the communication line is detoured to another communication line.

Next, the operation of each line control processing module in the line control processing unit 1 will be described with reference to the flowcharts of FIGS.

FIG. 3 shows a processing procedure when the communication line controlled by the line control processing module is normal. Here, the processing procedure of the line control processing module 11 will be described as an example. The same applies to the processing procedures of the other line control processing modules.

The line control processing module 11 is usually in a state of monitoring the following three cases (step S1).
Hereinafter, this state is called an idle state. (1) Receive data from its own control line L1. (2) Data for the own control line L1 is passed from the application program unit 4. (3) In the line management table 3, the application program unit 4 passes the data for the detour line stored in the detour line ID field 33b corresponding to the own control line L1.

Here, for example, the communication line L2 is set in the detour line ID field 33b corresponding to the own control line L1.
Is stored.

Line control processing module 1 in idle state
When the data is given to the line control processing module 1
1 determines whether data has been generated in any of the above cases (1) to (3) (step S2), and performs the following processing according to the source of the data.

When the line control processing unit 11 receives data from its own control line L1, after passing the received data to an application program corresponding to the received data,
Return to the idle state (step S3).

Next, a case where the line control processing module 11 receives a data transmission request for the own control line L1 will be described. In this case, the transmission request line is the own control line L1.

The line control processing module 11 transmits the data in the transmission data file 21 corresponding to the transmission request line L1 according to the contents of the transmission record pointer field 32a and the transmission status field 32b corresponding to the transmission request line L1 in the line management table 3. Find the record position where the request data is stored.

In this embodiment, the record position of the currently transmitted transmission request data or the last transmitted transmission request data is stored in the transmission record pointer field 32a. Therefore, when the content of the transmission status field 32b is “transmitting”, the record position stored in the transmission record pointer field 32a is the record position where the transmission request data is stored in the transmission data file 21. . The transmission status field 32
When the content of b is “transmitted”, the record position next to the record position stored in the transmission record pointer field 32a is the record position in the transmission data file 21 where the transmission request data is stored. .

When the content of the transmission status field 32b is "transmitting" in this step, it is only in a special case, such as immediately after a communication failure is found and bypassed, and normally "transmitted". ing.

The line control processing module 11 reads the above record position in the transmission data file 21 corresponding to the transmission request line L1, and receives the transmission request data.
Then, the line control processing module 11 edits the received transmission request data as necessary, and creates transmission data (step S4).

Further, the line control processing module 11
In order to indicate that the transmission request data stored in the above record position in the transmission data file 21 is currently being transmitted, the transmission record pointer field 32a corresponding to the transmission request line L1 in the line management table 3
Is updated to the above record position, and the content of the transmission status field 32b is updated to "transmitting" (step S5).

Then, the line control processing section 11 sends out the created transmission data to its own control line L1 (step S1).
6) Wait for a received response to the transmitted data from the destination computer (step S7).

When the line control processing module 11 receives the received response from the destination computer, it considers that the data transmission has been completed, and
, The content of the transmission status field 32b corresponding to the transmission request line L1 is updated to “transmitted” (step S
8).

The transmission process for the data is completed as described above, and it is determined whether or not another transmission request data has been generated during the transmission process (step S9). If another transmission request data has occurred, the process proceeds to step S4, and if no other transmission request data has occurred, the process returns to the idle state of step S1.

When the line control processing module 11 receives a request to transmit data to the detour line in the idle state (step S1), the processes in steps S4 to S9 are performed with the detour line as the transmission request line.

If transmission request data for a plurality of communication lines is generated in step S9, a method for processing transmission request data for its own control line preferentially,
There is a method of evenly and cyclically processing transmission request data for the own control line and the detour line. These methods may be arbitrarily selected according to the system using the communication line switching control device.

FIG. 4 shows a processing procedure when a communication failure occurs on a communication line. Here, a processing procedure of the line control processing module 11 when a failure occurs in the communication line L1 will be described. The same applies to the processing procedures of the other line control processing modules.

In the normal processing procedure described with reference to FIG. 3, a failure in a communication line is caused by a state of waiting for data reception or a state of receiving data (step S).
1, S3, S7) and during data transmission (step S6).

Here, description will be made assuming that the state of the line management table 3 is set as shown in FIG.
Data transmission to the communication line L2 is bypassed by the communication line L1. Therefore, the flag of the detour destination flag field 34a corresponding to the communication line L2 is set to "during detour", and "L1" is set in the detour destination line ID field 34b. Also, “1” is set in the detour line number field 33a corresponding to the communication line L1, and “L2” is set in the detour line ID field 33b.

The data transmission to the communication line L3 is bypassed by the communication line L5. Accordingly, the flag of the detour destination flag field 34a corresponding to the communication line L3 is set to "during detour", and "L5" is set in the detour destination line ID field 34b. The communication line L
"1" is set in the detour line number field 33a corresponding to 5 and "L3" is displayed in the detour line ID field 33b.
Is set.

In this state, the line control processing module 11
When detecting a communication failure in the own control line L1, the line control processing module 11 determines an alternative communication line for transmitting transmission request data to the own control line L1, that is, a bypass destination line (step S11). The method of determining the detour destination line is as follows.

(A) The entire line management table 3 is searched to find a communication line in which the flag of the bypass destination flag field 34a is reset, that is, a communication line that is normally communicating data. (B) Among the communication lines obtained in (a) above, a communication line having the smallest value in the number of detouring lines field 33a is obtained, and the communication line is set as a detour destination line.

In the example shown in FIG. 5, the communication lines L4 and L5
Has been reset in the bypass destination flag field 34a corresponding to. The value of the detour line number field 33a corresponding to the communication line L4 is “0”, and the detour line number field 3 corresponding to the communication line L5 is “3”.
The value of 3a is "1". Therefore, in this case, the detour destination line is determined to be the communication line L4.

The line control processing module 11 sets the flag of the detour flag field 34a corresponding to the own control line L1 in the line management table 3 to "during detour", and stores the detour destination line L4 in the detour destination line ID field 34b.
Is set (step S12). As a result, another line control processing module indicates that a failure has occurred in the own control line L1 and that data transmission to the own control line L1 is bypassing the bypass destination line L4.

Further, the line control processing module 11 requests the line control processing module that controls the detour destination line L4 to perform detour processing, so that the detour line ID corresponding to the detour destination line L4 in the line management table 3 is output. The line ID of the own control line L1 is added to the field 33b, and the value of the detour line number field 33a is counted up from "0" to "1" by one line (step S13).

Further, the line control processing module 11
The contents of the detour line information field 33 corresponding to the own control line L1 are checked in the line management table 3 (step 14). If there is a detouring line detouring to the own control line L1, the following processing is performed to switch the detouring line detouring to the own control line L1 to another normal communication line. In the example of FIG. 5, data transmission to the communication line L2 bypasses the own control line L1.

First, a detour destination line is determined by the methods (a) and (b) (step S15). Here, for example, the communication line L5 is determined as the bypass destination line. Then, the line control processing module 11 requests the line control processing module that controls the detour destination line L5 to perform detour processing.
The line ID of the communication line L2 is added to the D field 33b, and the value of the detour line number field 33a is counted up from "1" to "2" by one line (step S1).
6).

Further, the line control processing module 11
In the line management table 3, the contents of the bypass line ID field 34b corresponding to the communication line L2 are changed to the bypass line L5.
The detour destination of the communication line L2 is changed by changing to the line ID (step S17).

Further, the line control processing module 11 deletes the line ID of the communication line L2 from the detour line ID field 33b corresponding to the own control line L1 in the line management table 3 and sets the value of the detour line number field 33a. Is counted down from “1” to “0” (step S
18).

By the above processing, the state of the line management table becomes as shown in FIG. Line control processing module 1
1 checks whether all the detouring lines detouring to the own control line L1 have been detoured to other normal communication lines, and if there are detouring lines that have not been detoured yet, The processing from step S15 to step S18 is repeated (step S19).

Thereafter, the line control processing module 11
The status of the self-control line L1 is monitored, and the process waits for the recovery of the fault of the self-control line L1 (step S20).

When the failure of the own control line L1 is recovered, the line control processing module 11 first sends the following to the line control processing module that controls the detour destination line L4 in which data transmission to the own control line L1 is bypassed. Instruct the termination of the detour processing in the procedure.

(A) By referring to the detour destination line ID field 34b corresponding to the own control line L1 in the line management table 3, the detour destination line L4 which is currently bypassing data transmission to the own control line L1 is obtained (step S1). S2
1). (B) In the line management table 3, the line ID of the own control line L1 is deleted from the detour line ID field 33b corresponding to the detour destination line L4 obtained in (A) above, and the value of the detour line number field 33a is changed. Count down from "1" to "0" (step S22).

Next, the line control processing module 11 resets the contents of the detour destination line ID field 34b and the flag of the detour destination flag field 34a corresponding to the own control line L1 in the line management table 3 so that another line is processed. This indicates to the control processing module that the own control line L1 is communicating normally (step S2).
3).

When transmission data for the own control line L1 is being transmitted on the detour destination line L4, that is, when the content of the transmission status field 32b corresponding to the own control line L1 in the line management table 3 is "transmitting" Indicates that the transmission of the data has been completed and the content of the transmission status field 32b has been updated to "transmitted", or that a communication failure has occurred in the bypass destination line L4 transmitting the data. Waits until the flag of the detour destination flag field 34a corresponding to the detour destination line L4 is set to "during detour", and returns to the normal processing procedure. By the above processing, the state of the line management table 3 becomes as shown in FIG.

According to the above-described processing procedure, when a communication failure occurs in a certain communication line, the data transmission related to the failed communication line is transmitted to another normal communication line while keeping the communication load of the other normal communication line relatively uniform. It is possible to detour to a simple communication line and automatically terminate the detour processing when a failure is recovered.

In the above embodiment, the detour line information field 33 has the detour line number field 33a,
Although the detour destination line information field 34 has a detour destination flag field 34a, these fields are unnecessary if there is a technique that achieves an equivalent function.

For example, the detour line ID field 33
Alternatively, the number of detour lines may be obtained by counting the number of line IDs stored in b. In this case, the detour line number field 33a is unnecessary. If the data transmission to the own control line is bypassing another communication line, the bypass line ID is set in the bypass line ID field 34b, otherwise, the bypass line ID field 34b is always blank. In this case, when the bypass destination line ID field 34b is other than blank, it can be determined that a bypass is being performed. In this case, the bypass destination flag field 34a may be deleted.

In the above embodiment, one piece of transmission data is created for one piece of transmission request data passed from the application program unit 4. However, a maximum of M pieces of transmission request data are blocked. One transmission data may be created. Here, M is a positive integer. However, in this case, it is necessary to set a maximum of M pointers in the transmission record pointer field 32a of the line management table 3.

[0083]

As described above, according to the present invention, when a failure occurs in some of the communication lines, the detour process is performed by switching the communication lines while considering the load distribution of the remaining normal communication lines. Data communication can be automatically returned to the original communication line after the recovery from the failure. Moreover, it is not necessary for the application program to be aware of the control.

Therefore, the performance of a system using a plurality of communication lines is improved, and the burden of developing an application program is reduced, thereby improving the productivity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a communication line switching control device according to one embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a line control processing module included in the communication line switching control device of FIG.

FIG. 3 is a flowchart showing a processing procedure of a line control processing module when a corresponding communication line is normal.

FIG. 4 is a flowchart illustrating a processing procedure of a line control processing module when a failure occurs in a corresponding communication line.

FIG. 5 is a diagram illustrating an example of a state of a line management table before a failure occurs.

FIG. 6 is a diagram illustrating an example of a state of a line management table after a bypass process;

FIG. 7 is a diagram illustrating an example of a state of a line management table after recovery from a failure;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 line control processing unit 2 transmission data file unit 3 line management table 4 application program unit 1a data transmission / reception line monitoring processing unit 1b line recovery processing unit 1c line failure processing unit 1d transmission data creation processing unit 1e reception processing application programs 11, 12 , 1n line control processing module 21, 22, 2n transmission data file 31 line ID field 32 transmission data information field 32a transmission record pointer field 32b transmission status field 33 detour line information 33a detour line number field 33b detour line ID field 34 Detour destination line information field 34a Detour destination flag field 34b Detour destination line ID field 41, 42, 4m Application program L1, L2, Ln Communication line In the drawings, the same reference numerals indicate the same or corresponding parts.

Continuation of the front page (72) Inventor Tsutomu Shioya 1-6-13-402 Tomobuchi-cho, Miyakojima-ku, Osaka-shi

Claims (5)

(57) [Claims] 1. A communication line switching control device for controlling switching of communication lines in a system for performing data communication using a plurality of communication lines, the communication line switching control device being provided corresponding to each of the plurality of communication lines. A plurality of line control means connected to a communication line to be connected, and line information storage means for storing a plurality of line information respectively corresponding to the plurality of line control means, each of which is stored in the line information storage means. The line information includes the detouring line information indicating the other communication line when the corresponding communication line is bypassing data communication regarding the other communication line, and the data communication regarding the corresponding communication line is detoured to another communication line. And the detour destination line information indicating the other communication line when the line information is stored, and each of the plurality of line control means stores the detour information stored in the line information storage means. A communication line switching control device that controls data communication and data detour processing for a corresponding communication line by referring to and updating routing line information and said bypass destination line information. 2. When a failure occurs in a corresponding communication line, each of the plurality of line control units refers to the detour line information stored in the line information storage unit to determine a normal communication line. Among them, a communication line with a small communication load is determined as a detour destination line, data communication is detoured to the detour destination line, and the detour line information and the detour destination line information stored in the line information storage unit are updated. After the failure of the corresponding communication line is recovered, referring to the detour destination line information stored in the line information storage means, returning data communication by the detour destination line to the corresponding communication line, and The communication line switching control device according to claim 1, wherein the detour line information and the detour destination line information stored in an information storage unit are updated. 3. The communication apparatus according to claim 1, further comprising a plurality of transmission data storage units provided corresponding to the plurality of communication lines, each storing data to be transmitted to the corresponding communication line. Each of the stored line information further includes transmission data information indicating a position and a transmission state where data being transmitted or transmitted is stored in the corresponding transmission data storage unit, and each of the plurality of line control units includes 3. The method according to claim 2, wherein after the failure of the communication line to be recovered is restored, the data communication by the detour destination line is returned to the corresponding communication line by referring to the corresponding transmission data information stored in the line information storage means. Communication line switching control device. 4. A communication line switching control method for controlling switching of communication lines in a system for performing data communication using a plurality of communication lines, wherein a plurality of line information respectively corresponding to the plurality of communication lines are stored as line information. The line information is stored in a storage unit, and when the data communication related to the other communication line is bypassed by the corresponding communication line, the detoured line information indicating the other communication line and the data related to the corresponding communication line. When the communication is detouring to another communication line, the information includes detour destination line information indicating the other communication line, and refers to the detouring line information and the detour destination line information stored in the line information storage unit. And a communication line switching control method for controlling data communication and data bypass processing for each communication line by updating. 5. When a failure occurs in any one of the plurality of communication lines, a communication with a small communication load among normal communication lines is referred to by referring to the detouring line information stored in the line information storage means. A line is determined as a detour destination line, data communication is detoured to the detour destination line, and the detour line information and the detour destination line information stored in the line information storage means are updated, and a fault in the communication line is determined. Is restored, the data communication by the detour destination line is returned to the original communication line with reference to the detour destination line information stored in the line information storage means, and the detour during the detour stored in the line information storage means is performed. The communication line switching control method according to claim 4, wherein the line information and the bypass destination line information are updated.