JP3027483B2 - Line switching control method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit suitable for performing communication using a dedicated line at normal times, and switching to a backup line for communication during an emergency when a failure occurs in the dedicated line. > Related to a line switching control method and apparatus .

[0002]

2. Description of the Related Art Conventionally, a system has been adopted in which when a failure occurs in a communication line, the communication is continued by switching to a backup line prepared in advance. For example, there is a system configuration in which communication is performed using a dedicated line in a normal state, and a switched line using an ISDN (also called an ISDN network or simply a network) is used as a backup line in an emergency when a failure occurs in the dedicated line. . In such a system,
For emergency use, it is necessary to secure an ISDN channel that can be used immediately. However, the probability that a failure occurs in the dedicated line is extremely low, and if the backup line is used only for an emergency, the line utilization efficiency is reduced. In order to increase the line utilization efficiency, in order for other general terminal devices to use this backup line for normal communication at normal times, it is necessary to secure an empty channel in an emergency. A line switching control method is provided 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 is a diagram showing a system configuration to which a conventional line switching control method using ISDN as a backup line is applied. In FIG. 6, reference numeral 1 denotes a center device (hereinafter, referred to as "CCP") which is one of the terminal devices. Reference numeral 2 denotes a conventional line switching device, which includes a dedicated line 7 and an ISD
The line is switched by N. 2a is a switch for switching the line. Reference numeral 3 denotes a line switching device on the side opposite to 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 indicates an automatic calling procedure package. 3d and 3e are switches for switching the line.

[0004] Reference numeral 4 denotes a terminal device to be backed up (hereinafter referred to as a "backup target DTE" or simply "DTE") connected to the CCP 1 by a dedicated line 7 or an ISDN 9 as a backup line, and 5 is a line via the ISDN. A remote management device for remotely controlling the switching device 2 and the line switching device 3 is shown. Reference numeral 6 denotes a modem used for communication on the dedicated line 7. 8 is a general terminal device (hereinafter referred to as “general DTE” or simply “DT”) when ISDN is used for other purposes, that is, normal communication.
E ”). Reference numeral 9 denotes an ISDN, 10 denotes an ISDN subscriber line (hereinafter, simply referred to as “subscriber line”), and 11
Is a DSU connecting the subscriber line 10 and the ISDN 9. Reference numerals 12 and 13 denote a plurality of ISDN-compliant general DTs connected to the subscriber line 10 on the CCP1 side in a multipoint manner.
E and 14 and 15 are a plurality of ISDN-compliant general DTEs connected to the subscriber line 10 on the side opposite to the CCP 1 by multipoint connection.

[0005] The optional function unit 3c in the line switching device 3 is provided with a function unique to each model of the DTE 8 to be connected.

Next, the operation of the conventional example shown in FIG. 6 will be described. Now, the CCP1 and the DTE4 communicate via the dedicated line 7, and the DTE12 and the DTE8
It is assumed that communication is performed via the communication line 9. In this state, if a failure occurs in the leased line 7 or the modem 6, a failure report is made from the line switching device 2 or 3 to the remote management device 5 through D-channel packet communication via the ISDN 9.

[0007] 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 transmitted to the option function unit 3c by the ISDN.
9 is issued. Optional function part 3
c performs disconnection processing of the DTE 8 according to a predetermined procedure. After the completion of the disconnection processing, the line control unit 3b switches the switch 3d to the DTE 4 side, switches the switch 3e from the leased line 7 to the ISDN 9 side, and performs a 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 ISDN B channel.

[0008]

However, in the above-mentioned prior art, 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.

SUMMARY OF THE INVENTION The present invention is to solve such a conventional problem, and does not include an expensive optional function unit in a 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 a dedicated line to a backup line in an emergency when a failure occurs in the dedicated line.

[0010]

The present invention SUMMARY OF THE INVENTION In order to achieve the above object, the normal communicates via a dedicated line, dedicated
In the event of a failure in a service line, at least one backup line that communicates via a backup line consisting of an ISDN line.
Means for connecting a backup target terminal device, line monitoring means for monitoring the dedicated line, first connection means for connecting the backup target terminal device by switching to the dedicated line or backup line, and connecting to the backup line. the other terminals as well as multi-point connection, the other end
A second connection means capable of disconnecting the terminal device from the backup line , and
An empty channel confirmation unit for confirming that there is no communication, and the dedicated channel in response to a command from the line monitoring unit and the empty channel confirmation unit.
Switching of the first connection means when a failure occurs in a service line
E and a control means for controlling the connection or disconnection of the second connection means, before the said vacant channel check means
Check whether there is free space in the backup line channel.
Separately, if there is a free channel, the first connection
Depending on the stage, whether the backup target terminal device is the dedicated line
Switch to the backup line and connect
If there is no vacancy, the second connection means causes the other
Disconnect the terminal device from the backup line,
Terminal device to be backed up by connection means of (1)
Switch from the dedicated line to the backup line
The configuration is continued .

[0011]

According to the present invention, according to the above configuration, when the occurrence of a failure is detected by monitoring a dedicated line, a failure occurrence signal is transmitted to the management device and transmitted from the management device 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. The connection is switched from the dedicated line to the backup line, and when there is no free space in the backup line, a disconnection request for disconnecting the terminal device in use is transmitted to the backup line, and the other terminal device in use is released. After the 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 a normal state and to control line switching in an emergency without having a unique optional function unit corresponding to a plurality of terminal devices that want to make a multipoint connection to the backup line. can do.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a 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.

In FIG . 1, the same components as those in FIG. 7 showing the conventional example are denoted by the same reference numerals, and description thereof will be omitted. 8a
Is a terminal adapter for mutually converting a DTE 8 that does not support ISDN 9 into an I interface. 16
Indicates a line switching device on the side opposite to the line switching device 2.
In the line switching device 16, 16a is an operation panel unit, 1
Reference numeral 6b denotes a line monitoring unit which is a line monitoring unit for monitoring a failure of the leased line 7 and the state of the ISDN. 16e is a first connection unit for connecting the DTE 4 which is a dedicated line terminal device by switching to the dedicated line 7 or ISDN. Switch, 16c is DTE
A switch, which is a second connection means for multipoint connection of a plurality of terminal devices such as 8, 14, 15 to the ISDN 9, 16d is a control for controlling connection or disconnection of the switch 16c according to a command of the line monitoring unit 16b. It is a control unit as a means.

The configuration of FIG. 1 is characterized in that a plurality of terminal devices such as DTE 8 and DTEs 14 and 15 via terminal adapter 8a are connected to ISDN 9 via switch 16c in a multipoint manner. Since the I interface can be directly connected without having an optional function such as an automatic calling procedure package unique to each terminal device or a telephone interface package, the conventional restriction is eliminated.

Next, when the dedicated line 7 or modem 6 fails, the operations performed by the line switching unit 16 and the remote management apparatus 5 will be described with reference to an operation flowchart of FIG.

When the line switching device 16 detects a failure of the leased line 7 or the modem 6, the control method setting is selected (step S1). The setting of this control method includes the setting by the remote management device 5 (step S2), the setting by the independent control of the line switching device 16 (step S3), the case where the remote management device is not used or not used (step S4).
Select one of

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

In the processing in the remote management device 5, when the failure report A is received (step S6), the line switching device 16
Issue a switching instruction B (step S7). With this switching instruction B, two types of settings are possible. One is a first switching instruction (b) for switching only when the channel is idle.
1) (Step S9), and the other is to disconnect the in-use DTE and perform switching even if the channel using the line in the general DTE is blocked irrespective of the state of use of the line. (B2) (step S2).
1).

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

In the case of the first switching instruction (b1)

It is checked whether there is an empty channel (step S).
11) If yes, set backup target DTE4 to I
Connect to SDN 9 (step S16), if no,
No connection operation is performed (step S22).

In the case of the second switching instruction (b2)

First, it is checked whether or not there is a free channel (step S10).
Is connected to the ISDN 9 (step S16). If there is no DTE8,14,
Determining which of the 15 is using ISDN9,
After performing the disconnection processing (steps S12 to S15), the backup target DTE is connected to the ISDN 9 (step S16).

There are three procedures for the disconnection control, and it is determined whether the disconnection is specified by the normal control procedure or the disconnection is specified by another procedure (step S12). In the case of the normal control procedure, the general DTE 8, 14, or 1
The ISDN 9 used in step 5 is released according to the sequence (1) described later (step S13). If it is not a normal procedure, there are two more methods, and ISDN9 used for general DTE forcibly due to link disconnection,
Release according to the procedure of sequence (2) described later (step S14), and the speed matching method (I.460 and I.460 of CCITT recommendation).
461 etc.) and general DTE
There is a case where the ISDN 9 used in step (1) is released by a procedure of a sequence (3) described later (step S15). In either case, after the release is completed, the backup target DTE 4 is connected to the ISDN 9 (step S1).
6).

In the case of setting by the independent control of the line switching device 16 in step S3, a failure 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. 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, if no remote management device is used or not used in step S4, the operation of the panel 16a of the line switching device 16 is determined by the human (step S19).
, The switching connection is performed.

Steps S9 and S18
In step S1, if there is an empty channel,
It goes without saying that the processing moves to 6 and the backup target DTE 4 is connected. Also, in step S10, if another line is not using the ISDN, the connection process is similarly performed in step S16.

A description will now be given with reference to FIGS about to sequence (1) of the line switching procedure (3) shown in step S13 and 15 in FIG. 2.

In the sequence (1) shown in FIG. 3 , when the line switching device 16 detects a failure during data communication, it transmits a failure report 101 to the remote management device 5. Upon receiving this, the switching instruction 102 is transmitted from the remote management device 5. Thereafter, it is determined whether or not there is another free line (step S101). If there is no free line, it is determined whether or not there is a controllable DTE among the general DTEs using the line (step S102). If there is a controllable DTE, a switching control operation is performed (step S103). That is, a disconnection message (hereinafter simply referred to as “disconnect”) is sent to the line switching device 2 or TA (terminal adapter) of the other party.
And other messages are abbreviated as well.)
103 and transmits each communication signal 104 to the general DTE.
Is turned off.

With the ISDN 9 as a relay, the release 105 from the line switching device 2 or TA 8a on the other side is switched to the line switching device 1
6 is sent. Then, the release completion 106 is transmitted from the line switching device 16 to the line switching device 2 or the TA 8a using the ISDN 9 as a relay, so that the IS
The disconnection from the DN 9 is completed.

After the disconnection is completed, the backup target DTE
4 is connected to the ISDN 9. First, the call setting 107 is transmitted from the line switching device 16 to the line switching device 2, and the CCP 1 and the backup target DTE that were communicating with each other over the leased line before the failure occurred from the line switching device 2.
A call 108 is sent to 4. In response to this call 108, the response 109 from the CCP 1 is the backup target DT.
The response is sent to E4, and the response is
Is transmitted to the line switching device 2 using the ISDN 9 as a relay, and the connection process is completed.

Thereafter, the backup line ISDN
9, the data communication is resumed between the CCP1 interrupted by the failure and the backup target DTE4.

The sequence (2) in FIG. 4 is the same as the sequence (1) except that the method of the release processing is the same, and the description is omitted. Line switching device 16 is IS
Physical separation 201 is performed between DN9 and general DTE,
Upon receiving release 202 from ISDN 9, release complete 203
Is transmitted, the general DT using the ISDN 9 is transmitted.
E can be immediately separated.

In the sequence (3) of FIG. 5 , the line switching device 1 which has received the switching instruction 102 from the remote management device 5
6 determines whether or not there is another free line (step S101). If there is no free line, the disconnection function determines whether or not another DTE is using the ISDN 9 (step S301). A disconnection control operation is performed (step S302). The feature of this sequence is that the out-of-synchronization 301 is forcibly generated in the separation control operation. Accordingly, in this case, the communicating general DTE receives the disconnection 302 from the line switching device 2 or the TA on the other side. Then, the sequences (1) and (2)
In the opposite direction, the release 303 and the release completion 304 are exchanged, and the process of disconnecting the general DTE from the ISDN is completed.

Regarding the process of connecting the backup target DTE 4 to the ISDN 9, the sequence (1) and (2)
The description is omitted.

As is clear from the above embodiment, the line switching apparatus in FIG. 1 has a function of switching the DTE to be backed up to the dedicated line or the ISDN 9 which is a backup line and connecting it, and also connects 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, the general DTE has a function of performing disconnection processing and connecting the backup target DTE.

[0038]

The present invention improves the point that the ISDN, which is usually used as a backup line such as a dedicated line, is always idle and not effectively used except during an emergency (backup). ISDN as backup line
In the normal case where the terminal is not used, other general terminal devices can use the ISDN, and the line switching device does not have an optional function for each general terminal device, and a plurality of terminal devices can be used. The equipment can be connected in multipoints, and when an event of the intended purpose occurs, the line can be switched quickly and the ISDN can be used as a backup line. It has the effect of further increasing economically.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a system according to 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 performed by the line switching device in FIG. 1;

FIG. 3 is a sequence diagram of line switching according to a normal procedure in FIG. 2;

FIG. 4 is a sequence diagram of line switching according to a link disconnection procedure in FIG. 2;

FIG. 5 is a sequence diagram of line switching by a procedure using out-of-synchronization in FIG. 2;

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

[Explanation of symbols]

 4 Terminal device for backup (DTE) 5 Remote management device 7 Dedicated line 8 General terminal device (DTE) 9 ISDN (Backup line) 11 Terminating device (DSU) 16 Line switching device 16b Line monitoring unit (line monitoring means) 16c Switch ( Second connection means) 16d Control unit (control means) 16e Switch (first connection means)

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 1/22 H04L 29/14 H04M 11/00 303

Claims (5)

(57) [Claims] 1. A normal communicates via a dedicated line, dedicated
Means for connecting at least one terminal device to be backed up which communicates via a backup line consisting of an ISDN line in the event of an emergency in a service line, and line monitoring means for monitoring the dedicated line. First connection means for switching the backup target terminal device to the dedicated line or backup line and connecting the terminal device to the backup line, and connecting the other terminal device to the backup line by multipoint connection ;
A second connection means capable of disconnecting the terminal device from the backup line , and
An empty channel confirmation unit for confirming that there is no communication, and the dedicated channel in response to a command from the line monitoring unit and the empty channel confirmation unit.
Switching of the first connection means when a failure occurs in a service line
E and a control means for controlling the connection or disconnection of the second connection means, to determine whether there is a free channel before <br/> Symbol backup line by said vacant channel checking means, the channel when there is a vacancy, the said backup target terminal device by a first connecting means to connect switch to the backup line from the dedicated line, when there is no space in the channel, depending on the second connecting means such other
Disconnect the terminal device from the backup line,
Line switching control wherein the connecting switches the backup target terminal apparatus, the backup line from the private line by a connecting means. 2. Normally, communication is performed via a dedicated line,
In the event of a failure in the service line, the backup is ISDN.
At least one backup device communicating over the backup line.
Means for connecting a terminal device to be
Line monitoring means and the backup target terminal
Switch to the dedicated line or backup line and connect
And the other terminal device connected to the backup line.
Device and the other terminal device
Second connection means capable of disconnecting from the backup line
And whether there is an empty channel in the backup line.
Vacant channel confirmation means to be recognized,
To the dedicated line in response to a command from the vacant channel confirmation means
Switching and of said first connecting means when a failure occurs
A control means for controlling connection or disconnection of the second connection means;
Stage, wherein the empty channel checking means
Determine whether there is a free channel in the backup line,
If there is a vacancy in the channel, the first connection means
The backup target terminal device from the dedicated line
Switch to the backup line and connect, and there is a free channel
When there is no other terminal, the other terminal is connected by the second connection means.
Disconnect the device from the backup line and connect the first
Connecting the backup target terminal device by the
Control to switch from the dedicated line to the backup line
Line switching control, comprising:
apparatus. 3. The method according to claim 2, further comprising :
Means for transmitting a signal to the remote management device, and
Receiving the disconnection command signal transmitted from the remote management
Communication means, wherein the control means responds to the disconnection command signal.
The backup target terminal device is
Control to switch to the backup line from
The line switching control device according to claim 2, wherein: 4. Communication by the backup line
Hand to disconnect the other terminal device from the backup line
Steps include forced disconnection means for forcibly opening the line and disconnection.
There is a line release means by a disconnection sequence.
The other means by either disconnecting means or line opening means
Disconnecting the terminal device from the backup line.
3. The line switching control device according to claim 2, wherein: 5. The method according to claim 1, wherein said forcible disconnection means is provided for link disconnection or terminal disconnection.
Release the line during one of the
5. The line switching control device according to claim 4, wherein: