JPH06177865A - Line switching control method - Google Patents

Abstract

(57) [Abstract] [Purpose] In the normal case, multiple terminal devices connected to multipoint can use the backup line without providing expensive optional function parts, and in the event of an emergency when the leased line fails, it is dedicated A line switching control method for switching from a line to a backup line is provided. [Configuration] A terminal device 4 to be backed up that normally communicates via a dedicated line 7 and communicates via a backup line 9 in an emergency, and a plurality of other terminal devices 8 that communicate via a backup line, 14, 15 and a line monitoring means 16b for monitoring the leased line, and the first connection for switching the backup target terminal device to the leased line or the backup line
Connection means 16e, a second connection means 16c for connecting another terminal device to the backup line in a multipoint manner, and a control means 16d for controlling connection or disconnection of the second connection means according to a command from the line monitoring means. Is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line switching control method for performing communication by using a leased line in normal times and switching to a backup line in an emergency when a failure occurs in the leased line.

[0002]

2. Description of the Related Art Conventionally, a system has been adopted in which, when a failure occurs in a communication line, it is switched to a backup line prepared in advance to continue communication. For example, there is a system configuration in which communication is normally performed using a leased line, and an exchange line using ISDN (also referred to as ISDN network or simply network) is used as a backup line in an emergency when a failure occurs in the leased line. . In such a system,
In case of emergency, it is necessary to secure an ISDN channel that can be used immediately. However, the probability of failure of the leased line is very low, and if the backup line is used only for emergencies, the line utilization efficiency will decrease. In order to improve the line utilization efficiency, in order for other general terminal devices to use this backup line for normal communication in normal times, it is necessary to secure an empty channel in an emergency, and various terminals in the switching device must be secured. A line switching control method is adopted in which an optional function corresponding to the device is provided and is switched and used as an original backup line only in an emergency.

FIG. 6 shows a system configuration diagram to which a conventional line switching control method using ISDN as a backup line is applied. In FIG. 6, 1 indicates a center device (hereinafter referred to as “CCP”) which is one of the terminal devices. 2 is a conventional line switching device, a dedicated line 7 and ISD
Switch the line by N. 2a is a switch for switching the line. Reference numeral 3 denotes a line switching device on the side facing the line switching device 2. In the line switching device 3, 3a is an operation panel unit, 3b is a line monitoring control unit, and 3c is an optional function unit, which shows an automatic calling procedure package. Further, 3d and 3e are switches for switching lines.

Reference numeral 4 denotes a backup target terminal device (hereinafter referred to as "backup target DTE" or simply "DTE") connected to the CCP 1 and the leased line 7 or an ISDN 9 as a backup line, and 5 denotes a line via the ISDN. A remote management device for remotely controlling the switching device 2 and the line switching device 3 is shown, and 6 is a modem used for communication with the dedicated line 7. Reference numeral 8 denotes various general terminal devices (hereinafter, "general DTE" or simply "DT") when ISDN is used for other purposes, that is, for normal communication.
"E"). Reference numeral 9 is ISDN, 10 is an ISDN subscriber line (hereinafter simply referred to as "subscriber line"), and 11
Is a DSU that connects the subscriber line 10 and the ISDN 9. 12 and 13 are a plurality of ISDN compatible general DTs that are multipoint connected to the subscriber line 10 on the CCP1 side.
E and 14 and 15 are a plurality of ISDN-compatible general DTEs which are multipoint-connected to the subscriber line 10 on the side opposing the CCP 1.

The optional function unit 3c in the line switching device 3 has a unique function for each model of the DTE 8 to be connected.

Next, the operation of the conventional example shown in FIG. 6 will be described. Now, CCP1 and DTE4 are communicating via the leased line 7, and DTE12 and DTE8 are ISDN.
It is assumed that communication is being performed via 9. When a failure occurs in the leased line 7 or the modem 6 in such a state, the failure is reported from the line switching device 2 or 3 to the remote management device 5 by D channel packet communication via the ISDN 9.

The remote management device 5 transmits a switching instruction to the line switching device 3 in response to the failure report. Line switching device 3
In the above, the line control unit 3b determines the idle state of the channel of the subscriber line 10, and when the channel is blocked, the DTE 8 is set to ISDN for the option function unit 3c.
A disconnection request command from 9 is given. Optional function part 3
The c performs the disconnection process of the DTE 8 according to a predetermined procedure. After the disconnection process is completed, the line control unit 3b switches the switch 3d to the DTE 4 side and switches the switch 3e from the dedicated line 7 to the ISDN 9 side to perform the partner connection operation. As a result, the switch 2a of the line switching device 2 also switches from the dedicated line 7 to the ISDN 9. After the switching, the communication interrupted by the failure can be resumed by the B channel of ISDN.

[0008]

However, in the above-mentioned conventional technique, the switching device needs to have an expensive optional function unit according to the type of the terminal device that normally uses the backup line, and does not have the optional function unit. There is a problem that the terminal device connected to the switching device cannot practically use the backup line.

The present invention is intended to solve such a conventional problem, and in a normal case, a plurality of multipoint-connected terminal devices are used as backup lines without providing an expensive optional function unit in the line switching device. It is an object of the present invention to provide an excellent line switching control method that can be used by switching from the leased line to the backup line in an emergency when a failure occurs in the leased line.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides at least a communication in a normal state via a dedicated line and in a emergency in a communication via a backup line.
Backup target terminal device, a plurality of other terminal devices that communicate via the backup line, line monitoring means for monitoring the leased line, and the backup target terminal device for switching to the leased line or the backup line. First connection means for connection, second connection means for multipoint connection of the other terminal device to the backup line, and connection or disconnection of the second connection means in response to a command from the line monitoring means. And a control means for controlling.

[0011]

According to the present invention, with the above configuration, when the leased line is monitored and the occurrence of a failure is detected, a failure occurrence signal is transmitted to the management apparatus and is transmitted from the management apparatus in response to the failure occurrence signal. In response to the switching command signal, it is determined whether or not any of the other terminal devices is using the backup line, and if there is a free channel in the backup line, the backup target terminal device is When switching from a dedicated line to the backup line and connecting, and when the backup line is full, a disconnection request to disconnect the terminal device in use is sent to the backup line and the other terminal device in use is released. After completion, the backup target terminal device is switched from the dedicated line to the backup line and connected.

Therefore, it is possible to use the backup line in the normal state and to control the line switching in the emergency, without providing an optional function unit specific to a plurality of terminal devices to be connected to the backup line in a multipoint manner. can do.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the line switching control method according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a part of a system configuration to which a line switching control method using ISDN as a backup line is applied.

FIG. 1 shows a system configuration to which a line switching control method using ISDN as a backup line is applied. In FIG. 1, the same components as those in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted. Reference numeral 8a is a terminal adapter for converting the DTE8 not compatible with ISDN9 into an I interface. Reference numeral 16 denotes a line switching device on the side facing the line switching device 2. Line switching device 1
In FIG. 6, 16a is an operation panel section and 16b is a dedicated line 7.
Line monitoring unit that is a line monitoring unit that monitors the failure of the ISDN and the state of ISDN, and 16e is a DTE4 that is a leased line terminal device.
Is connected to the dedicated line 7 or ISDN by switching as a first connecting means, and 16c is a DTE 8, 14, 1
A switch which is a second connecting means for multipoint connecting a plurality of terminal devices such as 5 to the ISDN 9, and a control means 16d which is a control means for controlling connection or disconnection of the switch 16c in accordance with a command from the line monitoring unit 16b. It is a department.

The configuration of FIG. 1 is characterized in that a plurality of terminal devices such as the terminal device 8 and the terminal devices 14 and 15 via the terminal adapter 8a are ISDN via the second connecting means 16c.
9 is multi-point connected, the line switching device 16 has an automatic calling procedure package unique to each terminal device,
Since the I interface can be directly connected without having an optional function such as a telephone interface package, the conventional restrictions are eliminated.

Next, the operation executed by the line switching device 16 and the remote management device 5 when a failure occurs in the leased line 7 or the modem 6 will be described with reference to the operation flowchart of FIG. When the line switching device 16 detects a failure in the leased line 7 or the modem 6, the control method setting is selected (step S1). This control method is set by the remote management device 5 (step S2) and by the independent control of the line switching device 16 (step S2).
3) Select either the case where there is no remote management device or the case where it is not used (step S4).

In the case of the setting by the remote management device 5, the line monitoring unit 16b transmits the failure report A to the remote management device 5 by D channel packet communication, and waits for an instruction from the remote management device 5 (step S5). .

In the process of the remote management device 5, when the trouble report A is received (step S6), the line switching device 16
The switching instruction B is issued to (step S7). With this switching instruction B, two types of settings are possible. One is a first switching instruction (b) that switches only when the channel is idle.
1) (step S9), and the other is to switch the DTE by disconnecting the in-use DTE even if the channel using the line is blocked by the general DTE regardless of the use condition of the line. Switching instruction (b2) (step S2
1).

The line switching device 16 which has received the switching instruction B
Confirms the use status of the ISDN 9 that is the backup line that has received the instruction (step S8), and whether the switching instruction B is the first switching instruction (b1) or the second switching instruction (b2). Is determined and the following operation is performed.

In the case of the first switching instruction (b1)

It is confirmed whether or not there is an empty channel (step S
11), if yes, set the backup target DTE4 to I
Connect to SDN9 (step S16), if not,
No connection operation is performed (step S22).

In the case of the second switching instruction (b2)

First, it is confirmed whether or not there is a free channel (step S10). If there is, a backup target DTE is found.
Is connected to ISDN 9 (step S16). If not, it is determined which of the DTEs connected in multipoint is using the ISDN 9, and after performing the disconnecting process (steps S12 to S15), the backup target DTE is connected to the ISDN 9 (step S12). S1
6).

There are three procedures for disconnection control, and it is determined whether disconnection is designated by the normal control procedure or disconnection is designated by another procedure (step S12). In case of the normal control procedure, the general DTE8, 14 or 1 depending on the normal procedure.
The ISDN 9 used in step 5 is released by the procedure of sequence (1) described later (step S13). If the procedure is not normal, there are two more methods, and ISDN9, which was forcibly used in the general DTE due to the disconnection of the link,
The case of releasing in the procedure of the sequence (2) described later (step S14) and the speed matching method (CCITT Recommendation I.460, I.460).
461 etc.), and due to loss of synchronization between terminals, general DTE
There is a case where the ISDN 9 used in step S15 is released by the procedure of sequence (3) described later (step S15). In either case, after the release is completed, the backup target DTE4 is connected to ISDN9 (step S1).
6).

In the case of the setting by the independent control of the line switching device 16 in step S3, the fault report C is sent to the remote management device 5, but the line is independently set without waiting for the switching instruction from the remote management device 5. The usage status of (1) is checked (step S17), and it is determined whether or not there is a free line (step S18). If there is no free line, each process from step S10 is executed. On the other hand, when there is no remote management device in step S4 or when the remote management device is not used, switching connection is performed by the operation of the panel 16a of the line switching device 16 according to a person's judgment.

Incidentally, step S9 and step S18
Of course, if there is a free line, the process goes to step S16 and the process of connecting the backup target DTE 4 is performed. Also, in step S10, when another line is not using the ISDN, connection processing is similarly performed in step S16.

Next, the sequence (1) to (3) of the line switching procedure shown in steps S13 to S15 in FIG. 3 will be described with reference to FIGS. 4 to 6.

In the sequence (1) shown in FIG. 4, when the line switching device 16 detects a fault during data communication, it transmits a fault report 101 to the remote management device 5. The switching instruction 102 is transmitted from the remote management device 5 which receives this. Then, it is determined whether or not there is another free line (step S101), and if there is no free line, it is determined whether or not the general DTE that is using the line has a controllable DTE (step S102). ), If there is a controllable DTE, a switching control operation is performed (step S103). That is, a disconnection message (hereinafter, simply "disconnect") is sent to the line switching device 2 or TA (terminal adapter) on the other side.
And other messages as well)
103 to transmit each communication signal 104 to the general DTE.
To turn off.

The ISDN 9 is used as a relay, and the release 105 is transmitted from the partner line switching device 2 or TA to the line switching device 16. Then, the disconnection completion 106 is transmitted from the line switching device 16 to the line switching device 2 through the ISDN 9 as a relay, whereby the disconnection of the general DTE from the ISDN 9 is completed.

After disconnection is completed, the DTE to be backed up
4 to the ISDN 9 is performed. First, the call setting 107 is transmitted from the line switching device 16 to the line switching device 2, and the line switching device 2 communicates with the CCP1 and the backup target DTE that are communicating with each other via the leased line before the failure occurs.
4 is sent a call 108. In response to this call 108, the response 109 from CCP1 is the backup target DT.
It is transmitted to E4 and the line switching device 16 confirms the response 110
Is transmitted to the line switching device 2 with ISDN 9 as a relay, and the connection process is completed.

After that, ISDN which is a backup line
Via 9, the data communication is restarted between the CCP1 interrupted by the failure and the backup target DTE4.

The sequence (2) of FIG. 5 is different from the sequence (2) only in the release processing method, and is otherwise the same and its description is omitted. The line switching device 16 is an IS
Physically separate 201 between DN9 and general DTE,
Upon receipt of release 202 from ISDN 9, release complete 203
General DT using ISDN9 by sending
E can be separated immediately.

In the sequence (3) of FIG. 6, the line switching device 1 that has received the switching instruction 102 from the remote management device 5.
6 determines whether or not there is another free line (step S101), and if there is no free line, the disconnection function determines whether or not another DTE is using ISDN 9 (step S301), A disconnection control operation is executed (step S302). The characteristic of this sequence is that the out-of-synchronization 301 is forcibly generated in this disconnection control operation. Therefore, in this case, the general DTE in communication receives the disconnection 302 from the line switching device 2 or TA on the partner side. Then sequences (1) and (2)
In the opposite direction, the release 303 and the release completion 304 are exchanged to complete the disconnection processing of the general DTE from the ISDN.

Regarding the connection processing of the backup target DTE 4 to the ISDN 9, the sequences (1) and (2)
The description is omitted here.

As is apparent from the above embodiment, the line switching device in FIG. 1 has a function of switching the backup target DTE to the ISDN 9 which is a dedicated line or a backup line, and connecting a plurality of general DTEs to each DT.
Multipoint connection can be performed without providing an optional function unit for each E. Then, in an emergency when a failure occurs in the leased line, when the general DTE is using the backup line, it has a function of disconnecting and connecting the backup target DTE.

[0037]

EFFECTS OF THE INVENTION The present invention improves the fact that ISDN normally used as a backup line such as a leased line is not effectively used in an idle state except in an emergency (during backup). ISDN as a backup line
In the normal time when the terminal is not used, the ISDN can be used by other general terminal devices, and moreover, a plurality of terminals can be provided without providing an optional function for each general terminal device in the line switching device. The equipment can be connected at multiple points, and when an event for the intended purpose occurs, the line can be switched promptly and the ISDN can be used as a backup line. It has the effect of further increasing economically.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a system of an embodiment to which a line switching control method according to the present invention is applied.

FIG. 2 is a flowchart of a line switching operation executed by the line switching device in FIG.

FIG. 3 is a sequence diagram of line switching according to a normal procedure in FIG.

4 is a sequence diagram of line switching according to the link disconnection procedure in FIG.

5 is a sequence diagram of line switching according to a procedure using out-of-sync in FIG.

FIG. 6 is an overall configuration diagram of a system to which a conventional line switching control method is applied.

[Explanation of symbols]

 4 Backup Target Terminal Equipment (DTE) 5 Remote Management Equipment 7 Leased Line 8 General Terminal Equipment (DTE) 9 ISDN (Backup Line) 11 Termination Equipment (DSU) 16 Line Switching Device 16b Line Monitoring Unit (Line Monitoring Unit) 16c Switch ( Second connection means) 16d Control unit (control means) 16e Switch (first connection means)

Claims (3)

[Claims] 1. At least 1 which communicates via a leased line in a normal time and communicates via a backup line in an emergency
Backup target terminal device, a plurality of other terminal devices that communicate via the backup line, line monitoring means for monitoring the leased line, and the backup target terminal device for switching to the leased line or the backup line. First connection means for connection, second connection means for multipoint connection of the other terminal device to the backup line, and connection or disconnection of the second connection means in response to a command from the line monitoring means. Control means for controlling the backup line to determine whether or not there is a free channel, and when there is a free channel, the first connecting means moves the backup target terminal device from the dedicated line to the backup line. When switching to the backup line and connecting, when there is no free channel, disconnect the terminal device in use by the second connecting means. , Line switching control method characterized by connecting the backup target terminal apparatus is switched to the backup line from the private line. 2. The line switching control method, comprising reconnecting the other terminal device in use to the backup line after completion of the switching connection to the backup line. 3. The line control switching method according to claim 1, wherein the backup line is an ISDN line used by a terminal device having a point-multipoint connection configuration at the normal time.