JP3517164B2 - Communication device with duplex switching function - 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 device having a duplication function for receiving copied data from a duplicated network.

[0002]

2. Description of the Related Art Due to the development of information society in recent years,
The types of communication used by users are also diversified.

Examples of this communication include leased line, frame relay (FR) communication, and asynchronous transfer mode (A
TM) communication, time division multiplexing (TDM) communication, Internet communication, and telephone.

When the user desires to use the various communication services as described above together, by integrating the various communication services so that they can be handled collectively, the management can be facilitated and the connection can be simplified. . A multiplexing device is one of the communication devices for realizing the integration of the communication services.

Among networks connected to this multiplexer, there is also a duplex network for improving reliability.

Further, the multiplexing device may function as an ATM communication device for realizing ATM communication.

FIG. 2 is a block diagram showing an example of a connection state of a conventional multiplexer.

The service providing network 1 is a network owned by a telecommunications carrier, and a node device 1 for taking out a service of the telecommunications carrier from this network and providing the service.
a and 1b are provided.

The access network 2 is a network for connecting the user 3 and the service providing network 1, and is assumed to be duplicated to improve reliability. Further, in the access network 2, line terminators 4 are provided at both ends of the duplicated active transmission line (active system) 2a and the redundant transmission line (spare system) 2b.

The access network 5 is also the same as the access network 2 and is a network having an active system 5a and a standby system 5b for connecting the user 6 and the service providing network 1 to each other.

As an example, the service providing network 1 and the access networks 2 and 5 are networks for ATM (asynchronous transfer mode).

The terminal device 3a of one user 3 and the access network 2 are connected by a multiplexing device 7a, and the access network 2 and the service providing network 1 are also connected by a multiplexing device 7b. There is. The multiplexing device 7a may be provided with a terminal device for another communication service used by the user 3.

Depending on the type of service, node devices may be connected or the service providing network may be duplicated.

The terminal device 3b of the other user 6 and the access network 5 are also connected by the multiplexing device 7c, and the access network 5 and the service providing network 1 are also connected by the multiplexing device 7d. There is. Also in this case, the multiplexing device 7c may be provided with another terminal device used by the user 6.

FIG. 3 is a block diagram showing an example of a transmission operation to a duplex network and a reception operation from the duplex network in a conventional multiplexer.
Here, transmission and reception of cells from the service providing network 1 to the terminal device 3b in FIG. 2 will be described, but the same applies to transmission and reception in the opposite direction. The same applies to transmission / reception between the terminal device 3a and the service providing network 1.

Cells 8a to 8c from the service providing network 1
Is received by the external interface circuit 9a of the multiplexer 7d, cell-copied by the bridge circuit 10, and the active system 5 by the external interface circuits 9b and 9c, respectively.
It is transmitted to the virtual path (VP) 11 of both a and the backup system 5b. Further, another virtual path 12 may exist in the active system 5a and the standby system 5b.

A cell is a fixed-length (53-byte) information transfer unit, and is composed of a 5-byte cell header and a 48-byte information field.

In addition to the data cells 8a and 8c, the transmitted and received cells 8a to 8c include OAM cells (Operation Administration and Maintenance cells) for operation and maintenance.
8b is also included.

The cells 8a to 8c transmitted by the virtual paths 11 of both the working system 5a and the standby system 5b are respectively received by the external interface circuits 9d and 9e of the multiplexer 7c. In the multiplexer 7c, cells 8a to 8c from the virtual path 11 of the system (here, the active system 5a) selected by the selector 13 among the received cells are transmitted to the terminal device 3b by the external interface circuit 9f. Sent.

ITU-T Recommendation I.630 recommends an architecture and mechanism for switching ATM layer protection of the network as a control system for the active system and the standby system of the duplexed ATM network.

Further, in ITU-T Recommendation I.630 Annex B, a protocol for an automatic protection switch is used in a switching operation for protecting an active line and a standby line from parallel failure (1 + 1) in each direction (Unidirectional). It is recommended that the selector (cell selection function) can be controlled only by a local request from a receiving side device connected to the network without using (APC).

Therefore, the select operations in the end devices of the access network are independent of each other. The local requests include, in order of priority, clearing the operation circuit, locking protection operation, forced switching, reception signal failure detection, reception signal deterioration, manual switching request, restore wait, no request. Is executed.

[0023]

As described above, when transmitting a cell to a duplicated network, the conventional multiplexing apparatus copies the cell by a bridge circuit and creates a virtual path and a backup for the working system. Send to both virtual paths of the system.

On the other hand, when a cell is received from the duplicated network, the cell is received from the virtual path of the system selected by the selector, and the OAM alarm cell indicating the occurrence of a failure is received as a spare system. Switch to the virtual path.

However, in such a duplication control, since the OAM alarm cell indicating the occurrence of a failure continues to be transmitted while being copied by the multiplexer, the failure occurs even if the virtual path managed by itself is normal. Indicating O
Switching may be performed by receiving an AM alarm cell.
This situation will be explained below.

FIG. 4 is a block diagram showing a cell transfer state when a failure occurs in a network to which a conventional multiplexer is applied. The same parts as those in FIGS. 2 and 3 are designated by the same reference numerals. There is. In addition, although the data transmission from the terminal device 3a to the terminal device 3b will be described with reference to FIG. 4, the same applies to the reverse case.

As a first example, it is assumed that a fault C occurs in the virtual path of the active system 5a in the access network 5. In this case, an alarm is detected by the line terminating device 4 on the receiving side in the active system 5a, and a signal indicating this alarm is VP-A.
IS (VP alarm indication signal) is OA
It is included in the M alarm cell and transmitted to the multiplexer 7c, and the protection switching operation is executed by the multiplexer 7c. The protection switching operation in this case contributes to the improvement of communication quality.

On the other hand, as a second example, a fault A occurs in the virtual path of the active system 2a in the access network 2.
In this case, the line terminating device 4 on the receiving side in the active system 2a
An alarm is detected by the VP-AIS indicating this alarm
Is included in the OAM alarm cell and transmitted to the multiplexer 7b.

In the multiplexer 7b, the received V
An OAM alarm cell including P-AIS is transmitted to the service providing network 1. Further, in the multiplexing device 7b,
Based on the VP-AIS of the OAM alarm cell received,
Assuming that the virtual path of the active system 2a is abnormal, the selector is switched so that the subsequent reception is performed by the virtual path of the standby system 2b.

In the multiplexer 7d, the cell received from the multiplexer 7b via the service providing network 1 is copied, and the OAM alarm cell including the VP-AIS is also copied. The copied cell is transmitted from the multiplexer 7d to both the virtual path of the working system 5a and the virtual path of the protection system 5b of the access network 5.

The cells transmitted from the multiplexer 7d to both the virtual path of the active system 5a and the virtual path of the standby system 5b are
The OAM alarm cell received by the multiplexer 7c from both the virtual path of the active system 5a and the virtual path of the standby system 5b, and the OAM alarm cell including the VP-AIS is also the same as the virtual path of the active system 5a and the standby system 5b. Received from both sides.

The multiplexer 7c receives the VP-AI received.
Based on S, the protection switching operation by the selector is executed even though the virtual path of the active system 5a has not failed. The protection switching operation in this case is meaningless because the system is switched although there is no failure.

Such a meaningless protection switching operation causes a time difference in data transmission of received data and a momentary interruption.

Even when the failure B occurs in the service providing network 1, both the virtual path of the active system 5a and the virtual path of the standby system 5b are normal as in the case of the failure A described above. Nevertheless, unnecessary protection switching operation is executed in the multiplexer 7c.

The present invention has been made in view of the above circumstances, and switches transmission lines only due to a failure in a duplicated network that is in a connection relationship with itself and is subject to switching control. An object of the present invention is to provide a communication device having a duplication function.

[0036]

SUMMARY OF THE INVENTION The essence of the present invention is to perform a predetermined period without switching the transmission line to be used when the time difference when the alarm cell is received from a plurality of transmission lines falls within the predetermined period. The point is to switch the transmission path to be used when it does not enter.

According to the first aspect of the present invention, the copied data can be received from a plurality of transmission lines, and the data is received from a backup transmission line when a failure of the working transmission line among the plurality of transmission lines is detected. The present invention relates to a communication device having a duplication function.

In the communication device having the duplication function of the first aspect of the invention, the monitoring means monitors the reception of the alarm data transferred when a failure occurs in the transmission path for each of a plurality of transmission paths,
The alarm reception time difference monitoring means determines whether the reception time difference of the alarm data of each of the plurality of transmission lines falls within a predetermined period based on the monitoring result by the monitoring means, and the switching control means performs the alarm reception time difference monitoring means If it is determined that the reception time difference of the alarm data for each transmission line is not within the predetermined period, an instruction to switch the active transmission line to the backup transmission line is issued.

The data may be cells, for example, and the plurality of transmission paths may be physical communication paths or logical communication paths.

As a result, it is possible to prevent the switching of the transmission lines to be switched by itself due to a failure that has occurred in another transmission line other than the plurality of transmission lines to be switched by itself. Therefore, it is possible to reduce the occurrence of a time difference and instantaneous interruption of data transmission caused by unnecessary switching, and it is possible to improve the reliability of data transmission.

A second aspect of the present invention is capable of receiving the copied cells from the logical connections respectively provided in the plurality of transmission lines, and detecting a failure of the logical connection in the active transmission line among the plurality of transmission lines. The present invention relates to a communication device having a duplication function for receiving cells from a logical connection on a backup transmission line.

In the communication device having the duplicated function of the second invention, the monitoring means monitors the reception of the alarm cell for each logical connection in the plurality of transmission lines, and the alarm reception time difference monitoring means displays the monitoring result by the monitoring means. On the basis of the alarm reception time difference monitoring means, the switching control means determines whether or not the reception time difference between the alarm cells of the logical connections on the plurality of transmission paths falls within a predetermined period. When it is determined that the cell reception time difference does not fall within the predetermined period, an instruction is issued to switch from the logical connection on the working transmission line to the logical connection on the backup transmission line.

Examples of logical connections include virtual channels and virtual paths.

In the communication device having the duplicated function of the second invention, the same effect can be obtained by the same operation as that of the first invention, but the transmission which is not affected by the failure is secured for each logical connection. The difference is that you can do it.

In the third invention, the communication device having the duplexing function of the second invention manages which logical connection among the plurality of logical connections in the plurality of transmission lines is being received. A switching state management means is added.

As a result, since the logical connection currently used can be easily grasped, the failed logical connection can be recovered at an early stage and the recovery work can be facilitated. Therefore, maintenance becomes easy.

[0047]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Here, the function as an ATM communication device is included, and within a predetermined time from both of the duplicated transmission lines,
A multiplexer that does not switch when an OAM alarm cell indicating a failure has been received will be described.

FIG. 1 is a block diagram showing an example of the multiplexing device according to the present embodiment. The same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. Here, only different parts will be described. explain in detail.

Here, two of the multiplexers 14 according to the present embodiment are connected by a network that is duplicated by an active system 15a and a standby system 15b. Between these multiplexers 14, a cell 8a is connected. 8c is a virtual path 16 (VP16) of the active system 15a and a virtual path 16 (V of the standby system 15b
It is transmitted by P16). The active system 15a and the standby system 15b have at least one other virtual path 17 (VP17).
...) may be set.

In the multiplexer 14, when operating as the receiving side, the external interface circuits 9d to 9f,
OAM cell monitoring circuits 18a and 18b, alarm reception timing monitoring circuit 19, switching control circuit 20, working preliminary selection circuit 21, manual switching / switchback circuit 22, path switching state management unit 2
3 works mainly.

The OAM cell monitoring circuit 18a is used for the active system 15
The cell received via the external interface circuit 9d is monitored for each virtual path 16 and 17 of a. And VP
-If there is an AIS, the VP-AIS is notified to the alarm reception time difference monitoring circuit 19.

The OAM cell monitoring circuit 18b includes a backup system 15
VP of OAM alarm cell for each virtual path 16 and 17 of b
The AIS is notified to the alarm reception time difference monitoring circuit 19.

The alarm reception timing monitoring circuit 19 is OA
When the VP-AIS is received from one of the M cell monitoring circuits 18a and 18b, the VP-AIS is received.
The other OAM within a predetermined period T from the time when S is accepted
Whether or not the same VP-AIS is accepted from the cell monitoring circuit is monitored for each virtual path 16 and 17.

The alarm reception timing monitoring circuit 19
Within a predetermined period T, both OAM cell monitoring circuits 18a,
When the VP-AIS on the same virtual path is accepted from 18b, it is determined that the received OAM alarm cell has been cell-copied, and the virtual paths 16 and 17 of its own switching target are determined to be normal.

On the other hand, when the same VP-AIS is not accepted from both OAM cell monitoring circuits 18a and 18b within the predetermined period T, the received OAM alarm cell indicates an abnormality of the virtual path to be switched by itself. Therefore, the virtual path that has received the OAM alarm cell is determined to be abnormal, and the switching control circuit 20 is notified of that fact.

The predetermined period T is from 0 second to 10 seconds.
Intervals on the order of seconds are available. Normally 0 seconds, but 1
If it is 0 second, the whole world can be covered, and the predetermined period T can be freely set and changed according to the network condition.

When the switching control circuit 20 receives the notification of the abnormal virtual path from the alarm reception timing monitoring circuit 19, the abnormal virtual path is determined to be the active system 15a or the standby system 15b based on the contents of the path switching state management unit 23. Recognize which system of. Then, the instruction for switching to the virtual path of another system different from the currently used system is notified to the active preliminary selection circuit 21.

Further, the switching control circuit 20 has a function of notifying the active spare selection circuit 21 of a command to switch to the virtual path of the system designated by the manual switching / returning circuit 22. Further, it has a function of registering in the path switching state management unit 23 which system is used for each virtual path by the notification of the switching command.

The active preliminary selection circuit 21 is a switching control circuit 2
Based on the switching instruction from 0, each virtual path 16, 1
For every 7, use the active system 15a or the standby system 15b
The cell from the virtual paths 16 and 17 of the selected system is transmitted via the external interface circuit 9f. That is, this working preliminary selection circuit 21
Receives a cell by designating a system to be used for each virtual path 16 and 17, and transmits the received cell via the external interface circuit 9f.

When the multiplexer 14 operates on the transmitting side, the multiplexer 14 performs the same operation as the multiplexer 7d shown in FIG. 3 described above. That is, when operating as the transmitting side, the cell received by itself is cell-copied and the active system 1
It is transmitted to both the virtual path of 5a and the virtual path of the backup system 15b.

The operation of the multiplexer 14 having the above structure will be described below.

Consider, for example, a case where the multiplexing device 14 according to the present embodiment is arranged instead of the multiplexing device 7c in FIG.

When the fault A occurs on the virtual path of the active system 2a of the access network 2, the OAM alarm cell including the VP-AIS is copied by the multiplexer 7d arranged between the service providing network 1 and the access network 5. And transmitted by virtual paths of both the active system 5a and the standby system 5b.

Then, the multiplexing device 1 according to the present embodiment
4, the active system 5a and the standby system 5 that are the switching targets of self
OAM alarm cells will be received from both virtual paths of b.

Thus, when the fault A occurs,
Since the cell copied OAM alarm cell is received,
The difference t between the reception time of the VP-AIS by the virtual path of the active system 5a and the reception time of the VP-AIS by the virtual path of the protection system 5b is within a predetermined period T, and the multiplexer 14 switches the virtual paths. Not executed

When the failure B occurs in the service providing network 1, it is the same as when the failure A occurs.

On the other hand, when the fault C occurs in the virtual path of the active system 5a of the access network 5, the VP-AIS is received by the multiplexer 14 only from the virtual path of the active system 5a.

Therefore, when the fault C occurs,
In the multiplexing device 14 according to the present embodiment, this VP-A
Switching of the virtual path that has transmitted the IS is executed.

As described above, when the multiplexer 14 according to the present embodiment operates as the receiving side, the same VP-AIS from both the active system 15a and the standby system 15b.
Is received within a predetermined period T, and if the same VP-AIS is received from both systems within the predetermined period T, switching is suppressed.

As a result, it is possible to prevent the malfunction of switching to the network in which no failure has occurred, and to prevent the occurrence of a data transmission time difference and the instantaneous interruption.

Further, the multiplexing device 14 according to the present embodiment
In the above, the alarm is monitored in units of virtual paths, and protection switching can be performed in units of virtual paths.

Therefore, switching can be executed in logical units regardless of the physical network configuration, and it is possible to prevent instantaneous interruption of the whole due to the occurrence of one alarm.

The multiplexing device 14 according to the present embodiment
Since it is possible not only to receive cells but to send,
For example, if all of the multiplexers 7a to 7d in FIG. 4 are replaced with the multiplexer 14, the same effect can be obtained not only in the direction from the terminal device 3a to the terminal device 3b but also in the opposite direction. it can.

Further, the multiplexing device 14 according to the present embodiment
4 has the same connection relationship as in FIG. 4 described above, but is similarly applicable when connecting an access network and a plurality of service providing networks, or when connecting a plurality of access networks and a service providing network. .

Further, in the case where the service providing network 1 of FIG. 4 is duplicated, the node devices 1a and 1b are also allowed to perform the same switching judgment as the multiplexing device 14 according to the present embodiment. The same effect as above can be obtained.

Further, in the present embodiment, the case where the switching is managed for each virtual path is described as an example, but the present invention is not limited to this, and the virtual channel (V
It may be managed in units of C). In this case, VC-AIS is used instead of VP-AIS as a switching trigger.

Further, although the case where the network to be switched is duplicated has been described in the present embodiment, the present invention is not limited to this, and the same applies to the case where more than one is multiplexed. Is applicable to.

It is also possible to give the line terminating device having no multiplexing function the duplexing function of the present invention.

[0080]

As described above in detail, in the present invention,
If the same alarm data is received from multiple transmission paths within a predetermined period, the transmission paths are not switched, and if the same alarm data is not received within a predetermined period, the transmission paths are switched. Command.

Therefore, it is possible to prevent switching from being performed on a transmission line that does not require switching.

Therefore, it is possible to reduce the occurrence of a time difference and instantaneous interruption of data transmission caused by the switching of the transmission path,
The reliability of data transmission can be improved.

Further, in the present invention, switching may be managed for each logical connection in each transmission line.
Then, switching can be executed in logical units regardless of the physical network configuration, and it is possible to prevent instantaneous interruption of the whole due to the generation of one alarm.

Further, in the present invention, by managing which logical connection is used, the failed logical connection can be recovered early and the recovery work can be facilitated. Therefore, maintenance becomes easy.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a multiplexing device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a connection state of a conventional multiplexing device.

FIG. 3 is a block diagram showing an example of a transmission operation to a duplex network and a reception operation from the duplex network in a conventional multiplexer.

FIG. 4 is a block diagram showing a cell transfer situation when a failure occurs in a network to which a conventional multiplexer is applied.

[Explanation of symbols]

1 ... Service provision network 2, 5 ... Access network 2a, 5a, 15a ... Working system 2b, 5b, 15b ... spare system 3, 6 ... User 3a, 3b ... Terminal device 4 ... Line terminator 7a to 7d, 14 ... Multiplexing device 8a to 8c ... cell 9a to 9f ... External interface circuit 10 ... Bridge circuit 11, 12, 16, 17 ... Virtual path 13 ... Selector 18a, 18b ... OAM cell monitoring circuit 19 ... Alarm reception time difference monitoring circuit 20 ... Switching control circuit 21 ... Working preliminary selection circuit 22 ... Manual switching / returning circuit 23 ... Path switching state management unit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Koyama 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) Reference JP-A-11-346225 (JP, A) JP 10-336195 (JP, A) JP 10-308741 (JP, A) Patent 3252833 (JP, B2) Patent 3307528 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 12/56 100

Claims (3)

(57) [Claims] 1. A duplication function capable of receiving copied data from a plurality of transmission lines, and receiving data from a backup transmission line when a failure of a working transmission line among the plurality of transmission lines is detected. In the communication device having the monitoring means (18a, 1) for each of the plurality of transmission paths, for monitoring reception of alarm data transferred when a failure occurs in the transmission path.
8b), based on the monitoring result by the monitoring means (18a, 18b), the alarm reception time difference monitoring means for determining whether the reception time difference of the alarm data of each of the plurality of transmission lines falls within a predetermined period ( 19), and when it is determined by the alarm reception time difference monitoring means (19) that the reception time difference of the alarm data for each of the plurality of transmission lines does not fall within a predetermined period, the transmission line from the working transmission line to the backup transmission line A communication device having a duplexing switching function, comprising: a switching control means (20) for instructing switching to. 2. The copied cells are transmitted to a plurality of transmission lines (15a, 1a).
It is possible to receive from the logical connection (VP16) provided in 5b) respectively, and when a failure of the logical connection (VP16) in the working transmission path (15a) among the plurality of transmission paths (15a, 15b) is detected. In a communication device having a duplex switching function for receiving cells from a logical connection (VP16) in a spare transmission line (15b), a logical connection in the plurality of transmission lines (15a, 15b)
Monitoring means (18a, 18) for monitoring the reception of the alarm cell for each (16)
b) and the logical connection (VP) in the plurality of transmission lines (15a, 15b) based on the monitoring result by the monitoring means (18a, 18b).
Alarm reception time difference monitoring means (19) for determining whether or not the reception time difference of each alarm cell of 16) falls within a predetermined period, and the plurality of transmission lines (15a, 15a by the alarm reception time difference monitoring means (19). If it is determined that the alarm cell reception time difference for each logical connection (16) in 15b) is not within the predetermined period, the logical connection (16) in the working transmission path (15a) to the backup transmission path (15a) ), A switching control means (20) for instructing switching to the logical connection (16), and a communication device having a duplication function. 3. The communication device having the duplication function according to claim 2, wherein any one of a plurality of logical connections (VP16) in the plurality of transmission lines (15a, 15b).
A communication device having a duplexing function, characterized in that a switching state management means (23) for managing whether or not a cell passing through is received.