JP3433453B2 - Packet switching system and packet switch - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet switching system in which a plurality of packet switching stations connected to each other through a communication line communicate with each other via the communication line, when the current communication line fails. The present invention relates to a protection line connection system having a function of detecting a failure early and performing backup with a protection line via a public switched network.

In the communication of data and the like using a packet switching system, if a line failure such as a disconnection occurs in a current communication line between packet switching stations forming the system, the communication is interrupted as it is. Therefore, line backup is performed using a backup communication line so that communication can be continued even if a failure occurs in the working line.

In this way, the reliability of the entire packet switching system is improved by providing the communication line with redundancy.

[0004]

2. Description of the Related Art A backup for a packet switching system is necessary only when a line fails. Therefore, the backup backup line is normally not used in normal times. Therefore, if a dedicated line equivalent to the working line is used as the backup line, a fixed line usage fee is charged regardless of the frequency of use, which is uneconomical. For this reason, public lines are widely used as backup lines for the purpose of reducing line maintenance costs.

Therefore, FIG. 8 exemplifies a configuration of a conventional packet switching system in a protection line connection system using a public line. In FIG. 8, 10 is a packet switching station (PS
1, PS2) and 12 are public switched networks, L1 is a working line mainly composed of a dedicated line, and L2 is a public line. The above elements constitute the packet switching system.

Furthermore, 11 is a data terminal (TE1, TE
2), the packet switching station 10 (PS1, PS
2) and communicates via the packet switching system.

The packet switching stations 10 (PS1 and PS2) are respectively connected to the dedicated line L1 and the data terminal 1
1 (TE1, TE2) normally performs packet communication via this working line L1.

In addition, the packet switch 10 (PS1, PS
2) are respectively connected to the public switched network 12 via the public line L2, and this public line L2-the public switched network 12-
The public line L2 constitutes a protection line.

Here, an outline of the operation of protection line connection in the conventional system will be described. FIG. 7 is a flowchart showing the flow of the protection line connection control of the conventional example. The packet switching station 10 (PS1, PS2) is always on the working line L.
The CD (carrier detector) line in 1 is monitored, and when a line failure occurs due to a disconnection or the like, this is detected due to the abnormality of the CD line (S1 in FIG. 7).

The stations PS1 and PS2 correspond to each other in operation, and the packet switching station 10 for detecting a fault may be the station PS1 or the station PS2. If either one is the calling station, The other is the called station, and all the following explanations are the same.

Here, it is assumed that a failure has occurred in the working line L1. The packet switching station 10 that has detected the failure automatically calls the destination packet switching station 10 by using the public line L2 and the public switching network 30 to form a link,
The communication line is switched from the failed working line L1 to the protection line L2, and communication is restarted (S2 in FIG. 7).

On the other hand, the packet switching station 10 constantly monitors the working line L1 even during the communication by the protection line L2 (S3 in FIG. 7), and when it detects that the failure is recovered,
After switching the communication path from the protection line L2 to the working line L1, the protection line L2 is opened and the normal communication state is restored (S4 in FIG. 7).

In S1 and S3 of FIG. 7, the packet switching station 10 monitors the working line L1 by detecting an abnormality in the CD line on the working line L1 to the partner packet switching station 10.

That is, when an abnormality is detected in the CD line of the working line L1, the packet switching station 10 starts a procedure for connecting to the protection line as a line failure to the partner packet switching station 10.

The conventional protection line connection system is mainly to automatically connect a protection line upon detection of such a physical failure and to backup the communication line in the event of a failure. However, in some line failures, it may not always be possible to detect only by an abnormality in the CD line. In such a case, in addition to the above-mentioned monitoring method, the packet switching station 10
By constantly monitoring the communication content transmitted or received by the local station, it is possible to cope with a line failure caused by a physical cause such as disconnection.

FIG. 6 shows the working line L in the conventional example.
An example of a time chart from the monitoring state of No. 1 to the protection line connection is shown. In FIG. 6, a horizontal arrow indicates a point-wise flow of packets, and a vertical axis indicates that time goes downward.

In the figure, CR is a call request packet for notifying the packet switching station 10 that a call is requested, C
N is a call request request packet for notifying that the call is requested to the data terminal 11 on the call side, CA is a call accept packet for notifying that the call is accepted, and CF is a call disconnection. Is a disconnection confirmation packet for confirming

In the case of the above-mentioned failure, a call request packet (CR) from a calling party is transmitted from the packet switching center 10 on the calling side, as shown in, for example, FIG. Since the incoming call notification packet (CA) is not returned from the called-side packet switching station 10 after a certain period of time, the working line L1 between the calling-side station and the called-side station is transmitted.
It is possible to detect the occurrence of a failure that cannot be detected only by monitoring the CD line.

The above-mentioned case where the failure cannot be detected only by the abnormality of the CD line is, for example, the working line L.
There is a case where there is a packet relay station (not shown) having no line backup function in the middle of 1 and the packet relay station stops the relay function due to congestion or the like (also called hangup). Conceivable.

In such a case, the CD line on the working line L1 from the packet relay station may be normally detected by both the packet switching stations PS1 and PS2.

[0021]

The problems that occur in the conventional system will be described with reference to the time chart of FIG.

In the conventional system, as described above, the fault of the working line L1 is mainly detected based on the detection of the physical fault of the line such as the monitoring of the CD line. Therefore, if an undetectable fault occurs due to this (in FIG. 6), the fault may not be detected until a call request is made (in FIG. 6).

Then, when the caller issues a call request, the failure is detected for the first time, and the procedure for connecting the protection line is started. However, in order to connect the protection line, the calling packet switching station 10 first dials the called side packet switching station 10 via the public line L2 and the public switching network 12 to call the other party, and then the called side packet. The call request packet (CR) must be transmitted again after setting the link with the exchange 10 and preparing the environment for communication.

For this reason, a delay time longer than that in normal time is required until the call request packet (CR) reaches the called side, the incoming call is accepted, and the incoming call acceptance packet (CC) is received. Will occur (~ in FIG. 6).

Since the protection line L2 is a public line in particular, the connection procedure includes dialing to the called-side packet switching station 10, waiting for a call response, and link setting, as compared with the case of a dedicated line. It takes a relatively large amount of time because it requires a unique procedure. Therefore, when viewed from the calling side terminal 11, an abnormally large amount of data transfer delay occurs, and depending on the processing procedure on the calling side, a timeout occurs (time out) and the call is automatically disconnected. It could happen.

An object of the present invention is to solve the above problems and to provide a protection line connection method in which the time required for public line connection processing in communication at the time of failure does not affect communication.

[0027]

The present invention, as shown in FIG.
Working line L1 for connecting a plurality of packet switching stations to each other
And the protection line L2, and when the working line L1 fails and cannot communicate, communication is automatically switched to the protection line L2 via the public line 12 to continue communication, and the failure of the working line L1 is recovered and communication is possible. Sometimes the protection line is opened and the working line L1
In the protection line connection method of the packet switching system for switching to the communication by the packet switching station 10 (PS1, P1
S2) indicates the monitoring means for monitoring the monitoring packet P periodically transmitted to the other packet switching stations 10 (PS2, PS1) that can be connected by the protection line (L2), and the monitoring packet P cycle. A time measuring means for measuring time is provided, and the time measuring means 52 is provided as shown in the flowchart of FIG.
Notifies the monitoring means (51) (S1 of FIG. 3) when the reception cycle of the monitoring packet (P) from the other packet switching station (10) is longer than the normal cycle (S1 in FIG. 3), and the monitoring means (51). ) Is connected to another packet switching station (10) via a protection line (L2) (S in FIG. 3).
2).

[0028]

The operation of the present invention will be described with reference to the time chart shown in FIG. In the protection line connection method according to the present invention, whether the working line can be used or not is determined by normal arrival / non-arrival of the monitoring packet within a certain period as shown in FIG. 2 (-in FIG. 2).

Therefore, in the case of a line failure that could not be detected until now when a call request is made, including a physical line failure due to a break in the working line or a failure of the circuit system. Also in this case, this can be detected early and connected to the protection line in advance (in FIG. 2).

For this reason, the backup by the protection line is completed before the call is made in the case of the failure of the working line, and even if a call request is made thereafter, it does not take longer than necessary. 2 ~).

[0031]

Embodiments of the present invention will now be described with reference to the drawings. Since the configuration inside the packet switching station 10 (PS1, PS2) is the same, the following description is common. The data terminal 11 shown in FIG.
(TE1, TE2) are packet terminals.

FIG. 4 is a diagram showing an internal configuration of the packet switching center 10 in the embodiment of the present invention. In FIG.
Reference numeral 1 is a packet switch, L1 is a working line, L2 is a public line, and 13 is a modem.

Reference numeral 21 is a management communication processor (MPR),
Performs call setup / release, routine section, system operation management, etc. A communication multiplexer (CMU) 22 controls data transfer between the line and the management communication processor 21.
The management communication processor 21 and the communication multiplexer 22 are duplicated.

Reference numerals 23 and 24 denote disk devices (DK), 2
Reference numerals 5 and 26 are maintenance consoles (VDUs), which are man-machine interfaces with a maintenance person and are composed of a display device and a printer. 27 is a magnetic tape unit (MT)
, Used to load the initial program of the system.

Next, details will be described. In the management communication processor 21, 31 and 32 are main storage devices (M
M), 33, and 34 are central control units (CCs), which control the entire packet switch 1 and use 32-bit processors. Further, 35 to 38 are channel control devices (CHC), which are the disk device 23 and the magnetic tape device 2.
7, maintenance consoles 25 and 26, and line parts,
It controls the input and output of data to and from the central control units 33 and 34.

On the other hand, in the communication multiplexer 22, 41
.About.43 and 41 'to 43' are line corresponding parts (LC), which correspond to the ends of the lines. 44 and 45 are line processing units (LPR)
Then, the channel control devices 35 to 38 and the line corresponding part 41 to
It intervenes between 43 and 41'-43 ', and controls communication between each other. 46 to 48 are line switching units (LS
In W), it is a line changeover switch in the duplicated line multiplexer 22.

Each of the data terminals 11 (TE1, TE2) (not shown) is performing data communication via the packet switch PS1-working line L1-packet switch PS2.
Further, each data terminal has a working line L1 and a public line L2-a public switched network 12-a public line L2 for a protection line L.
It can be connected even by 2. However, the protection line L2 is used for line backup when the working line L1 fails.

Since an analog line is generally used as the public line, it is necessary to carry out communication in a form in which packet data is modulated at the time of communication by the protection line L2. Therefore, the modem 20 is connected between the line and the device.

Needless to say, when the protection line is a digital line, the modulation by the modem 20 is not always necessary. That is, the presence or absence of the modem 20 is not directly related to the present invention and does not limit the present invention.

The signal transmitted from the terminal is branched in two directions after passing through the line switching unit 46 because the communication multiplexer 22 is duplicated, and the line corresponding units 41 and 41 '.
Entered in. Then, each signal is sent to the line processing unit 4.
It is sent to the central control units 33 and 34 via the channel control units 37 and 38 through 4, 45. The signals inputted thereafter are transmitted to the respective destinations by the central control units 33, 34.

The disk device 23, the maintenance console 25, and the magnetic tape device 27 are connected to the central control devices 33 and 34 via the channel control device 36. Figure 5
FIG. 1 is a block diagram of the central control units 33 and 34 of the packet switch 1. 51 is an in-network information monitoring unit that generates and monitors packet data containing information within the local station (mainly indicating congestion status etc.). The packet is transmitted as a packet P, and the monitoring packet P from another station is received. 52 is a monitoring timer,
The reception cycle of the monitoring packet P from another station is timed. 53
Is a control unit that controls the central control units 33 and 34.

The operation of the protection line connection in the packet switching station 10 will be described below. The monitoring packet P is assembled in the central control units 33 and 34 inside the packet switching center 10 based on the network information such as the congestion state in the own station, and through the channel control units 37 and 38, the line processing unit 44, 45--routed through the line corresponding units 41, 41'-line switching unit 46 to the line L1.

The monitoring packet P sent from another station via the line L1 follows a route opposite to the above route, like a normal packet. The central control units 33, 34 are
The monitoring timer 52 monitors the cycle of arrival of the monitoring packet P from another packet switching station 10.

The incoming monitoring packet P is decomposed and processed by the network information monitoring unit 51 as information indicating the current network status. A detailed operation while a failure is detected in the working line and the protection line is connected will be described below with reference to FIG.

As shown in the flowchart of FIG. 3, the central control units 33 and 34 connect the public line L2 when the monitoring packet P from the other packet switching station 10 is not received in a normal cycle (S1 in FIG. 3). A command signal is issued to the line processing unit 45 so as to connect to another packet switching station 10 via this (S2 in FIG. 3).

Then, the line processing unit 45 connects the public line L2 to the other packet switching station 10 and sets the link, and thereafter is formed by the public line L2-public switching network 12-public line L2. The backup line continues the communication state until the failure of the working line L1 is recovered.

At this time, since the in-network information monitoring unit 51 monitors the working line L1, the monitoring packet is transmitted / received even during the line backup by the public line L2. And
When the monitoring packet is normally received on the working line at a constant cycle, the procedure for switching the backup communication by the public line L2 to the normal communication state by the working line L1 is started (S5 and S10 in FIG. 3).

In this way, by using the monitoring packet P to detect a fault that was not detected until a call request is made in the past, the procedure for connecting the protection line is completed in advance, so that a call is made when a fault occurs. The time required for connection procedures for established communications is kept to a minimum.

[0049]

As described above, according to the present invention, in the packet switching system and the packet switching system, the connection of the protection line can be completed in advance when a call occurs when the working line fails. , The packet switching system that does not affect the communication time for public line connection processing
System and packet switch can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle configuration of the present invention. It also serves as an overall configuration diagram of the embodiment.

FIG. 2 is a time chart of the protection line connection in the principle configuration of the present description.

FIG. 3 is a flowchart of protection line connection in the principle configuration of the present description.

FIG. 4 is a configuration diagram of a packet switching station according to an embodiment.

FIG. 5 is a configuration diagram of a central control device according to an embodiment.

FIG. 6 is a flowchart of a conventional example.

FIG. 7 is a time chart in a conventional example.

FIG. 8 is a diagram showing a configuration of a conventional example.

[Explanation of symbols]

L1: Private line (working line) L2: Public line (standby line) 10: Packet switching station (PS1, PS2) 11: Data terminal (TE1, TE2) 12: Public switched network 20: Modem 21: Management Communication Processor (MPR) 22: Communication multiprocessor (CMU) 23, 24: Disk device (DK) 25 and 26: Maintenance console (VDU) 27: Magnetic tape unit (MT) 31, 32: Main memory (MM) 33, 34: Central control unit (CC) 35-38: Channel control device (CHC) 41-43, 41'-43 ': line interface (LC) 44, 45: Line processing unit (LPR) 46-48: Line switching unit (LSW) 51: In-network information monitoring unit (monitoring means) 52: Monitoring timer (time measuring means) 53: control unit

Continuation of front page (56) Reference JP-A-2-73746 (JP, A) JP-A-62-286339 (JP, A) JP-A-62-58746 (JP, A) JP-A-4-10832 (JP , A) JP 62-8640 (JP, A) JP 1-191541 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 12/56 H04L 1/22

Claims (2)

(57) [Claims] 1. A working circuit and a backup circuit via a public switched network.
Multiple packet switching stations that are interconnected by
Including, switching to the protection line when the working line fails
In obtaining a packet switching system, said packet switching stations, other connectable by the said packet switching station protection line
It periodically includes information on its own station with other packet switching stations.
Monitoring means to receive the no-monitoring packet monitors a failure of the working line, measures the reception cycle of the monitoring packet, the reception cycle
It is notified to the monitoring means that a period longer than the normal cycle has elapsed.
The packet switching station is provided with a clocking means to know
The above-mentioned monitoring means that the reception is not performed periodically and normally.
When detected by the timekeeping means, the
Forming the protection line with the other packet switching center
A package characterized by switching to the working line
Exchange system . 2. A working circuit and a backup circuit via a public switched network.
Connected to each other by a line, and when the working line fails
In the packet switch that switches to the protection line, With another packet switch that can be connected by the protection line
In between, periodically send a monitoring packet containing the information in its own device.
Monitoring means for transmitting and monitoring the failure of the working line, The reception cycle of the monitoring packet is timed, and the reception cycle is
It is notified to the monitoring means that a period longer than the normal cycle has elapsed.
With a timekeeping means to know, If the monitoring packet is received at the specified reception cycle and normally
Not detected by the monitoring means and the timing means
The other packet exchanges through the public network.
Switching to the working line by forming the protection line with the switchboard
A packet switch that is characterized by performing