JPH08331142A - Virtual path switching system - Google Patents

Abstract

PURPOSE: To perform switching from a current virtual path to a standby virtual path. CONSTITUTION: A cell for switching is inserted to the same positions of the current virtual path and the standby virtual path by a transmitter 20, and a cell for switching control on either side of the current virtual path or the standby virtual path is detected by a receiver 30. The cell on one side is stored in a phase absorption buffer 48, and the cell for switching control on the path on the other side is detected, and the cell string of the current virtual path is switched to the one of the standby path read out or transmitted from the phase absorption buffer 48.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a virtual path switching system, and more particularly to a virtual path switching system for switching between a working virtual path and a backup virtual path.

[0002]

2. Description of the Related Art In recent years, various types of information are collected in units of predetermined byte lengths, headers are added to the cells to form cells, and the destinations of cells are managed by the headers for multiplexing.
Asynchronous transfer mode (ATM) in which cells are sent to the network at arbitrary time positions for communication when information is generated
Is being developed.

In the above-mentioned ATM, transmission lines are conventionally switched such that the transmission lines between communication devices are duplicated by 0 system and 1 system, and when the active 0 system fails, it is switched to 1 system.

[0004]

Even if the physical transmission line is duplicated, in the case of a multiple failure of the working / spare transmission path or a failure of the relay device itself, the virtual path accommodated in that transmission path is cut off. , Recovery is not possible until the detour route is set.

In ATM, a flexible network can be constructed by introducing a concept of a virtual path (VP) set independently of a physical transmission line. For example, as shown in FIG. 9, apart from the working virtual path from the virtual path transmission device 10 to the virtual path reception device 12 via the virtual path relay device 11, the virtual path transmission device 10 to the virtual path relay device 13,
A backup virtual path is provided through 14 to the virtual path receiving apparatus 12. Thereby, for example, when the virtual path relay device 11 has a failure, it is possible to recover by switching from the working virtual path to the backup virtual path.

However, conventionally, a transmission route is set by an operating system that manages a network, and it takes time to set up a bypass route, and not only when a failure occurs, but also when a transmission line or a relay device is relocated. There was a problem that switching of paths could not be performed without interruption.

[0007] The present invention has been made in view of the above points,
It is an object of the present invention to provide a virtual path switching method that enables uninterruptible switching from a working virtual path to a backup virtual path.

[0008]

According to a first aspect of the present invention, a cell string transmitted from a transmitting device to a receiving device using a working virtual path and a backup virtual path different from the working virtual path is duplicated or missing cells. It is a virtual path switching method for switching without, in which a switching control cell is inserted at the same position of the working virtual path and the backup virtual path in the transmitting device, and the receiving device selects one of the working virtual path and the backup virtual path. The path switching control cell is detected, the cell of the one path is stored in the phase absorption buffer without cell duplication or loss, and the other path switching control cell is detected, and the working virtual path is detected. From the cell array of (1) to the cell array of the protection path read from the phase absorption buffer or transmitted.

According to a second aspect of the present invention, in the virtual path switching system according to the first aspect, the transmitter is
In response to a switching request from the receiving device, a switching control cell is inserted at the same position on the working virtual path and the backup virtual path.

According to a third aspect of the present invention, in the virtual path switching system according to the first aspect, the transmitting device is
A switching control cell is periodically inserted at the same position of the working virtual path and the backup virtual path, and the receiving device switches by the switching control cells of the working virtual path and the backup virtual path that arrive after the generation of the switching request. .

The invention according to claim 4 is the invention according to claim 1 or 2.
Alternatively, in the virtual path switching method described in 3, the receiving device separates an active virtual path and a backup virtual path of an arbitrary channel into two systems, and is preset for each system for each arrival cell of each system. Select the cell by referring to the table.

According to a fifth aspect of the present invention, in the virtual path switching system according to the fourth aspect, the two systems share a single phase absorption buffer. According to a sixth aspect of the present invention, in the virtual path switching method according to the first aspect, a threshold is provided in the phase absorption buffer, and when the buffer capacity of the phase absorption buffer exceeds the threshold, switching is considered to have failed and virtual path switching is stopped. To do.

According to a seventh aspect of the present invention, in the virtual path switching method according to the first aspect, a table for determining whether an arriving cell of the receiving device is a working virtual path cell or a backup virtual path cell is used as a working virtual path. It is rewritten by the management software when a path failure is detected.

The invention according to claim 8 is the virtual path switching system according to claim 1, wherein a table for determining whether an arriving cell of the receiving device is a cell of a working virtual path or a cell of a backup virtual path is set as a working virtual path. It is rewritten by hardware when a path abnormality notification cell is detected.

[0015]

According to the first aspect of the present invention, the switching control cell of one of the working virtual path and the backup virtual path is detected, the cell of one path is stored in the phase absorption buffer, and the other one is stored. To detect the path switching control cell and switch from the current virtual path cell row to the backup virtual path cell row, the phase difference between both virtual paths is absorbed by the phase absorption buffer to perform non-instantaneous interruption virtual path switching. be able to.

According to the second aspect of the present invention, since the switching control cell is inserted in the working virtual path and the backup virtual path in response to the switching request of the transmitter, the unnecessary switching control cell is the working virtual path and the backup virtual path. It is possible to prevent the cell transmission efficiency from being lowered due to being not inserted into the cell.

According to the third aspect of the present invention, since the switching control cell is periodically inserted in the working virtual path and the backup virtual path, it is not necessary to transmit the switching request from the receiving device to the transmitting device. In the invention according to claim 4, since the working virtual path and the backup virtual path of an arbitrary channel are separated into two systems in the receiving device, the capacity of the output virtual path after switching is 2 above.
It is possible to prevent the capacity from decreasing below the capacity of each virtual path.

In the invention described in claim 5, since the phase absorption buffer is shared by the two virtual paths,
Only one phase absorption buffer is needed, and an increase in the amount of hardware can be prevented. In the invention according to claim 6, switching is stopped when the buffer capacity of the phase absorption buffer exceeds a threshold value. Therefore, when the phase absorption buffer cannot absorb the phase difference between the working virtual path and the backup virtual path, there is no interruption switching. Can be canceled. At this time, no cell loss occurs.

According to the invention described in claim 7, when the working virtual path fails, the table can be rewritten by the management software to switch to the backup virtual path. According to the invention described in claim 8, it is possible to switch to the backup virtual path by detecting the abnormality notification cell when the working virtual path fails and rewriting the table by hardware.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a block diagram of a virtual path switching without interruption of the present invention. In the figure, a virtual path transmission device 20
Each of the internal multiplexers (MUXs) 21 and 22 multiplexes ATM cells coming from a plurality of external transmission lines to perform VPI.
It is supplied to the conversion units 23 and 24, respectively. The ATM cell has a predetermined byte length in which an ATM header is added to the data unit of a predetermined byte length (48 bytes). VPI converter 23, 24
Each of them is a VPI conversion unit 2 for converting the virtual path identifier (VPI) in the header of each cell according to the path to be transmitted.
The cells output by 3 and 24 are supplied to the ATM switch 25, where the output cells of the VPI converter 23 are copied and the two output terminals 25a and 25b of the ATM switch 25 are copied.
Output from The cells output from the terminal 25a are supplied to the interface circuits (IF) 26a and 26b, respectively, and the cells output from the terminal 25b are supplied to the interface circuits (IF) 27a and 27b. VPI
The cell output from the conversion unit 24 is similarly supplied to another interface circuit (not shown). The interface circuit 26a is connected to the interface circuit (IF) 31a of the virtual path receiving apparatus 30 via a working virtual path (hereinafter referred to as "working path") 0 system 28a, and the interface circuit 26b is connected to the interface circuit 31b via a working path 1 system 28b. Connected with. Further, the interface circuit 27a is connected to the interface circuit 32a of the virtual path receiving apparatus 30 via a backup virtual path (hereinafter referred to as "backup path") 0 system 29a, and the interface circuit 27b is connected to the interface circuit 32b via a backup path 1 system 29b. It is connected.

The transmission path switching unit 33 of the virtual path receiving apparatus 30 switches between the working paths 0 system 28a and 1 system 28b and selects a cell supplied from one of the interface circuits 31a and 31b. Similarly, the transmission path switching unit 34 switches between the backup paths 0 system 29a and 1 system 29b, and selects a cell supplied from one of the interface circuits 32a and 32b. Transmission line switching unit 3
The cells selected by 3 and 34 are the VPI conversion units 35 and 3, respectively.
6, and the virtual path identifier (VPI) in the header of each cell is converted here. Further, the VPI conversion unit 35 adds a tag indicating the working path to the header of each cell of the working path and outputs the header.
Outputs the tag with a tag indicating that it is a backup path added to the header of each cell of the backup path. It is supplied to the terminals 37a and 37b of the ATM switch 37, respectively. The ATM switch 37 multiplexes the cell strings supplied from the terminals 37a and 37b and supplies the multiplexed cells to the virtual path switching unit 38.

FIG. 1 shows a virtual path switching unit 38 of the present invention.
2 is a block diagram of a first embodiment of FIG. In the figure, a cell output from the ATM switch 37 enters a terminal 41, and this cell is parallelized by a serial / parallel converter (S / P) 42 and supplied to an abnormality detector 43. Anomaly detector 4
3 detects the abnormal state notification cell, the table rewriting unit 5
Notify 1. The cell that has passed through the abnormality detection unit 43 is supplied to the OAM cell detection unit 44 and the VPI filter 46. O
The AM cell detection unit 44 detects a control cell (OAM cell) for maintenance and operation management of the network, and if this OAM cell is for virtual path switching, supplies the data of the OAM cell to the switching control unit 45. Further, the VPI filter 46 normally uses the VPI and tag in the header of the cell for each arriving cell, and the working / protection path pass table 4
See 7. The working / protection path passage table 47 has a virtual path identifier (VPI, VPI of, for example, 12 bits, 40
It has a value of 96) and is unique in the tag, and control information for instructing whether to pass the cell of the working path or the cell of the backup path is written. As a result, in normal operation, if it is a cell on the working path, let it pass,
If it is a cell on the backup path, it is discarded. When switching without interruption, cells that arrive after the OAM cell for virtual path switching are passed.

The switching control unit 45 includes an OAM cell detection unit 44.
The phase absorption buffer 48, the buffer read control unit 49, and the multiplexing unit 52 are controlled based on the virtual path switching OAM cell data supplied from. The table rewriting unit 51 updates the working / protection path passage table 47 after the completion of the virtual path switching.

The phase absorption buffer 48 has a capacity corresponding to the phase difference between the working path and the protection path, and buffers the cells output from the VPI filter 46. The buffer read controller 49 reads cells from the phase absorption buffer 48 under the control of the switching controller 45.
The multiplexer (MUX) 52 multiplexes the cell supplied from the VPI filter 46 and the cell read from the phase absorption buffer 48 under the control of the switching controller 45, and outputs the multiplexed cell. The multiplexed cells are serialized by the parallel / serial converter 54 and output from the terminal 55.

By the way, management software (COM)
Rewrites the contents of the working / spare path passing table 47 from the terminal 60 at the time of failure switching, and sends a virtual path notification from the terminal 61 to the OAM cell detection unit 44 at the time of non-interruption switching. Further, the table rewriting unit 51 rewrites the working / spare path passage table 47, that is, the rewriting success, to the terminal 62.
To the management software, and the switching control unit 45 notifies the management software from the terminal 63 of the rewriting failure.

FIG. 3 shows a flowchart of the processing executed by the virtual path receiving apparatus 30 during the normal operation. In FIG. 3, header conversion for the highway (HW) that outputs cells in step S10, that is, VPI conversion unit 3
The VPI (virtual path identifier) to be converted is set in steps 5 and 36. Next, in step S12, it is set in the working / protection path passage table 47 which path should be passed as the working path and which path should be discarded as the protection path. These steps S10 and S12 are processes performed by the management software of the virtual path receiving device 30.

Next, in step S14, the VPI converter 3
The header is converted for each cell arriving at 5, 36. At this time, the VPI conversion unit 35 attaches an identifier (tag in the header) indicating that it is a working path cell, and the VPI conversion unit 36 attaches an identifier indicating that it is a protection path cell and outputs it. In the next step S16, the VPI filter 46 refers to the working / spare path passing table 47 for each arriving cell and determines whether the arriving cell is the working cell or the spare cell. In this case, the arriving cell is discarded in step S20. Step S1
When S8 and S20 are executed, the process proceeds to step S14, and steps S14 to S20 are repeated.

4 and 5 show a virtual path receiving device 30.
7 shows a flowchart of a process at the time of non-instantaneous interruption switching (forced switching) executed by. In FIG. 4, when the forced switching request is generated in step S30, the OA is notified to the management software of the virtual path transmission device 20 in step S32.
An M cell transmission request is issued, and in step S34, an OAM cell standby request is issued to the hardware of the virtual path receiving device 30. The above-mentioned forced switching request is a case where the virtual path relay device of the working path is stopped for maintenance, for example. The above steps S30 to S34 are processes performed by the management software of the virtual path reception device 30.

The management software of the virtual path transmission device 20 which has received the OAM cell transmission request in step S32 issues an OAM cell transmission request to the hardware of the virtual path transmission device 20, whereby the virtual path transmission device 20 is An OAM cell is inserted and transmitted from both the working path and the protection path.

The OAM cell waiting request in step S34 is notified from the terminal 61 to the OAM detecting section 44, and the virtual path switching section 38 enters the OAM cell waiting mode in step S36. OAM in this OAM cell waiting mode
When the cell detector 44 detects an OAM cell, step S3
In 8 whether this OAM cell is an OAM cell of the working path,
That is, it is determined whether or not the OAM cell of the working path is received. If it is the OAM cell of the working path, the process proceeds to step S42, and the switching control unit 45 stores the cells arriving after the OAM cell of the working path in the phase absorption buffer 48.

Thereafter, in step S44, the OA of the backup path is set.
It is determined whether or not the M cell is detected by the OAM detection unit 44, that is, whether the OAM cell of the protection path is received, and if the OAM cell of the protection path is not received, step S46.
Then, the switching control unit 45 determines whether or not the phase absorption buffer 48 is full, and if not, proceeds to step S44. When the OAM cell of the protection path is received in step S44, the process proceeds to step S48, the switching control unit 45 discards the cell stored in the phase absorption buffer 48, and the VPI filter unit 46 deletes the cells after the OAM cell of the protection path. It is passed and supplied to the MUX 52. Thereafter, in step S50, the table rewriting unit 51 causes the working / spare path passing table 4
7 is updated to make the backup path the active path.

After that, the table rewriting section 51 sends a table rewriting notification from the terminal 62 to the management software in step S52, and ends the processing. Step S4
If the phase absorption buffer 48 is full in step 6, the buffer read control unit 49 sequentially reads the cells of the working path stored in the phase absorption buffer 48 in step S54,
The signal is supplied to the MUX 52 and mixed into an empty cell of the cell sequence of the main signal. Thereafter, in step S56, the buffer read control unit 4
9 determines whether or not the phase absorption buffer 48 has become empty. If it is not empty, the process proceeds to step S54 to continue reading while storing the cells of the working path in the phase absorption buffer 48, and when the phase absorption buffer 48 becomes empty. Step S57
Then, the phase absorption buffer 48 is separated from the main signal, and then the process proceeds to step S58 of FIG.
3 notifies the management software of the failure in switching and ends the processing.

That is, the cell lines A ₁ , B ₁ , OAM, C ₁ , D ₁ , E ₁ , and F ₁ shown in FIG. 6A are transmitted on the working path, and are shown on the protection path in FIG. Cell rows A ₂ , B ₂ ,
When OAM, C ₂ and D ₂ are transmitted, cell A ₂ is a copy of cell A ₁ , and OA of the working path when the same applies to others.
It is not supplied to the cells C ₁ , D ₁ and MUX 52 of the working path after the M cell, and the phase absorption buffer 4 as shown in FIG.
8 and the cell C ₂ after the OAM cell of the protection path,
D ₂ is supplied to the MUX 52, and the cell string shown in FIG. Also, the phase absorption buffer 4
The cells C ₂ and D _{2 in 8} are discarded.

On the other hand, in step S38, the OAM of the working path
If no cell has been received, the process proceeds to step S60 of FIG. 5, and the OAM cell detection unit 44 determines whether or not the OAM cell of the protection path has been received. If it has not been received, the process proceeds to step S38 in FIG. When the OAM cell of the protection path is received, the process proceeds to step S62, and the switching control unit 45 stores the cells arriving after the OAM cell of the protection path in the phase absorption buffer 48.

Next, in step S64, it is determined whether or not the OAM cell of the working path is detected by the OAM cell detector 44. If this is detected, the process proceeds to step S66.
The PI filter 46 discards arriving cells after the OAM cell on the working path. Further, in step S68, the buffer read control unit 49 sequentially reads the spare path cells stored in the phase absorption buffer 48, supplies them to the MUX 52, and mixes them into the empty cells of the cell sequence of the main signal. In step S70, the buffer read control unit 49 determines whether or not the phase absorption buffer 48 is empty. If not, the process proceeds to step S68 to continue reading while storing the cells of the backup path in the phase absorption buffer 48. When the buffer 48 becomes empty, the phase absorption buffer 48 is separated from the main signal in step S72 and the VPI filter 46 is made to pass the cells of the backup path, and then the process proceeds to step S50 of FIG. 4 to update the working / backup path passage table 47. To do.

By the way, in step S64, the working path O
If no AM cell is received, the switching control unit 45 determines in step S74 whether the phase absorption buffer 48 is full, and if not, proceeds to step S64. When the phase absorption buffer 48 becomes full, the switching control unit 45 discards the cell stored in the phase absorption buffer 48 in step S76, and notifies the management software of the switching failure in step S58.

That is, the cells A ₁ , B ₁ , OAM, C ₁ , D ₂ shown in FIG. 7A are transmitted on the working path, and the cell rows A ₂ , B ₂ shown in FIG. , OAM, C ₂ ,
When D ₂ , E ₂ and F ₂ are transmitted, cell A ₂ is a copy of cell A ₁ , and so on.
The cells C ₂ and D ₂ after the cell are stored in the phase absorption buffer 48 as shown in FIG. 7C, and after the OAM cell of the working path arrives, they are stored in the phase absorption buffer 48 as shown in FIG. The selected cells are mixed with the empty cells of the main signal and output. The cell E _{2 of the} backup path is stored in the phase absorption buffer 48 because the cell E ₂ came in before the cell D ₂ was read from the phase absorption buffer.

There are two methods for automatic switching due to a failure. Each of the interface circuits 31a to 32b generates an alarm signal VP-AIS to notify the management software when a signal disconnection, frame synchronization failure, deterioration of error rate, etc. occur, and an abnormal state notification cell of the alarm signal VP-AIS. Is generated and sent to the device on the downstream side.
In the first method, the working / protection path passage table 47 is rewritten from the terminal 60 of the virtual path switching unit 38 by the management software supplied with the VP-AIS. In the second method, when the abnormality detecting unit 43 detects an abnormal state notification cell of the working path, the abnormality detecting unit 43 controls the table rewriting unit 51 to update the working / protection path passage table 47 and use the protection path. Change to the path.

In this way, non-instantaneous switching from the working path to the protection path can be realized by independent control on the receiving side.
For example, in FIG. 10, when it is necessary to stop the virtual path relay device 11 of the working path for maintenance and inspection, the virtual path reception device 12 issues a forced switching request to the virtual path transmission device 10,
It is possible to perform non-instantaneous switching from the working path that passes through the virtual path relay apparatus 11 to the backup path that passes through the virtual path relay apparatuses 13 and 14, which allows maintenance and inspection of the virtual path relay apparatus 11.

Further, since the ATM path 37 multiplexes the working path and the protection path and supplies them to the virtual path switching section 38, the hardware scale of the virtual path switching section 38 does not need to be large, and the feasibility becomes extremely high. . By the way, in the above-described embodiment, the virtual path transmission device 20 sends the OA to the working path and the backup path in response to the OAM transmission request due to the generation of the switching request from the virtual path reception device 30.
Although M cells are inserted, instead of this, the virtual path transmission device 20 periodically OAMs the working path and the protection path.
After inserting a cell and the virtual path receiving device 30 generates a switching request, it is possible to detect an OAM cell that is periodically transmitted and perform non-instantaneous virtual path switching. However, in this case, the virtual path transmitter 20 assigns serial numbers to the OAM cells, and the virtual path receiver 30 determines whether the OAM cells of the working path and the backup path are the same serial number. FIG. 8 shows a block diagram of a second embodiment of the virtual path switching unit of the present invention. In this embodiment, an ATM switch 137 is used instead of the ATM switch 37.
Therefore, the cells of the working path and the backup path supplied from the VPI converting units 35 and 36 are not multiplexed, and the serial / parallel converting unit (S) of the virtual path switching unit 138 is separately provided.
/ P) 142A, 142B, respectively. That is,
When the working path of an arbitrary channel is supplied to the S / P 142A, the backup path of the virtual path is S / P1.
42B, and when the S / P 142A is being supplied with a backup path of another arbitrary channel, the working path of the virtual path is being supplied to the S / P 142B.

The cells of the respective virtual paths parallelized by the S / Ps 142A and 142B are the abnormality detection unit 1
43A and 143B, respectively. Abnormality detection unit 143
a, 143B notifies the table rewriting unit 151 when detecting an abnormal state notification cell. Abnormality detectors 143A, 14
The cells that have passed 3B are OAM cell detectors 144A and 144A.
B and VPI filters 146A and 146B. The OAM cell detectors 144A and 144B detect control cells (OAM cells) for network maintenance and operation, and if the OAM cells are for virtual path switching, the data of the OAM cells are supplied to the switching controller 145. . Further, each of the VPI filters 146A and 146B normally refers to the working / protection path pass table 147 for each arriving cell using the VPI in the header of the cell. Each of the working / protection path passage tables 147A and 147B is made unique by a virtual path identifier (VPI) (VPI has a value of 4096 in 12 bits, for example), and a cell of the working path is passed or a protection path Control information is written to instruct whether to pass the cell. Since the tables 147A and 147B are provided for each of the two systems of ATM multiplexed signals supplied from the ATM switch 137, it is not necessary to add a tag to each of the VPI conversion units 35 and 36, and each of the tables 147A and 147B has V.
It is unique only by PI. As a result, during normal operation, cells on the working path are passed, and cells on the protection path are discarded. Whether the cell is the working path or the protection path is determined by the tag of the header. When switching without interruption, cells that arrive after the OAM cell for virtual path switching are passed.

The switching control unit 145 is the OAM cell detection unit 1
Phase absorption buffer 1 based on the virtual path switching OAM cell data supplied from 44A and 144B
48, the buffer read control unit 149, the multiplexing unit 152, the selector 170, and the MUX buffers 171A and 171B. The table rewriting unit 151 uses the working / protection path passage table 147 after completion of virtual path switching.
A and 147B are updated.

The phase absorption buffer 148 has a capacity corresponding to the phase difference between the working path and the backup path, and the VPI filters 146A and 146B to the selector (SEL) 170.
Buffer the cells supplied through. The buffer read control unit 149 controls the reading of cells from the phase absorption buffer 148 according to the control of the switching control unit 145. The MUX buffers 171A and 171B are VPI
After passing through the filters 146A and 146B, respectively, the multiplexing unit 5
This is a buffer for waiting when the cells supplied to 2 have the same timing. Multiplexer (MUX) 52
Is controlled by the switching control unit 45, and the MUX buffer 1
The cells supplied from 71A and 171B and the cells read from the phase absorption buffer 148 are multiplexed and output. The multiplexed cells are serialized by the parallel / serial conversion unit 154 and output from the terminal 155.

The management software (COM) operates from the terminal 160 to the working / protection path passage table 14 at the time of failure switching.
7A and 147B are rewritten, and the OAM cell detection units 144A and 14A from the terminal 161 at the time of non-interruption switching.
A virtual path notification is given to each of the 4Bs. Further, the table rewriting unit 151 uses the working / spare path passage table 147.
Rewriting of A and 147B, that is, successful rewriting, is input to the terminal 162.
Notifies the management software from the switching control unit 145
Notifies the management software of the rewriting failure from the terminal 163.

The operation of the virtual path switching unit 138 of FIG. 8 during normal operation, non-interruptionless switching, and failure switching is shown in FIG.
The operation is substantially the same as that of the virtual path switching unit 38.
The only difference is that the cells that have passed through the VPI filters 146A and 146B are temporarily stored in the MUX buffers 171A and 171B, respectively, and then multiplexed by the MUX 152.

Here, the virtual path switching unit 38 of FIG.
ATM switch 37 to AT up to 2.4 Gbps
The M multiplexed signal is supplied, and the working path and the protection path are multiplexed. In the normal operation, the cells of the protection path are discarded by the VPI filter 46, so that the ATM multiplexed signal output from the terminal 55 is It drops to 1.2 Gbps. On the other hand, the virtual path switching unit 138 of FIG.
A maximum of 2.4 Gbps ATM multiplex signal from the M switch 137 comes in, and the serial / parallel conversion unit 142
A and 142B are supplied respectively. Here again, during normal operation, the cells of the backup path are discarded by the VPI filters 146A and 146B, respectively.
Since it is multiplexed by the UX 152, 2.4 from the terminal 155.
An ATM multiplex signal of Gbps is output. Further, in this embodiment, the phase absorption buffer 1 is composed of two systems of ATM multiplexed signals.
48 is shared, and an increase in the amount of hardware can be prevented accordingly.

[0047]

As described above, according to the first aspect of the present invention, the switching control cell of one of the working virtual path and the backup virtual path is detected and the cell of one path is phase-absorbed. It is stored in the buffer, and the cell for switching control of the other path is detected and switched from the cell row of the working virtual path to the cell row of the backup virtual path. Instantaneous interruption Virtual path switching can be performed.

According to the second aspect of the invention, since the switching control cell is inserted into the working virtual path and the backup virtual path in response to the switching request of the transmitting device, the unnecessary switching control cell is used as the working virtual path and the working virtual path. It is possible to prevent the cell transmission efficiency from being lowered because the cell is not inserted in the backup virtual path.

According to the third aspect of the invention, since the switching control cell is periodically inserted in the working virtual path and the backup virtual path, it is not necessary to transmit the switching request from the receiving device to the transmitting device. . According to the invention described in claim 4, since the working virtual path and the backup virtual path of an arbitrary channel are separated into two systems in the receiving device, the capacity of the output virtual path after switching is the above two systems. It is possible to prevent the capacity of each virtual path from decreasing.

According to the invention of claim 5, 2
Since the phase-absorption buffer is shared by the virtual paths of the system, only one phase-absorption buffer is needed and the increase in the amount of hardware can be prevented. Further, according to the invention of claim 6, switching is stopped when the buffer capacity of the phase absorption buffer exceeds a threshold value. Therefore, when the phase absorption buffer cannot absorb the phase difference between the working virtual path and the backup virtual path, there is no Instantaneous interruption switching can be canceled.

Further, according to the invention described in claim 7, when the working virtual path fails, the table can be rewritten by the management software to switch to the backup virtual path. Further, according to the invention described in claim 8, it is possible to detect the abnormality notification cell at the time of the failure of the working virtual path and rewrite the table by hardware to switch to the backup virtual path, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a block diagram of a virtual path switching unit according to the present invention.

FIG. 2 is a configuration diagram of virtual path switching according to the present invention.

FIG. 3 is a flowchart of processing during normal operation.

FIG. 4 is a flowchart of a process at the time of non-instantaneous interruption switching.

FIG. 5 is a flow chart of a process at the time of switching without instantaneous interruption.

FIG. 6 is a signal timing chart for explaining non-instantaneous interruption switching.

FIG. 7 is a signal timing chart for explaining non-instantaneous interruption switching.

FIG. 8 is a block diagram of a virtual path switching unit of the present invention.

FIG. 9 is a diagram for explaining path duplication.

[Description of Reference Signs] 20 virtual path transmission device 23, 24, 35, 36 VPI conversion unit 25, 37, 137 ATM switch 30 virtual path reception device 38 virtual path switching unit 43, 143A, 143B abnormality detection unit 44, 144A, 144B OAM cell detection unit 45,145 switching control unit 46,146A, 146B VPI filter 47,147A, 147B working / spare path passing table 48,148 phase absorption buffer 49,149 buffer reading control unit 51,151 table rewriting unit 52,152 Multiplexing unit 170 Selector 171A, 171B MUX buffer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshinori Koyanagi 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Kazuo Iguchi 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited ( 72) Inventor Hiroshi Ota 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Hitoshi Uematsu 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation ( 72) Inventor Hiromi Ueda 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Norihiro Ashi 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Ltd. (72) Inventor Yukio Nakano 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Information & Communication Division (72) Masahiro Takatori Inventor Masahiro Takatori 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock company Hitachi Information & Communication Division

Claims (8)

[Claims] 1. A virtual path switching method for switching a cell string transmitted from a transmitting device to a receiving device by using a working virtual path and a backup virtual path different from the working virtual path without duplication or loss of cells. The device inserts a switching control cell at the same position of the working virtual path and the backup virtual path, and the receiving device detects the switching control cell of either one of the working virtual path and the backup virtual path, The cell of the path is stored in the phase absorption buffer, the switching control cell of the other path is detected, and the cell string of the working virtual path is read from the phase absorption buffer or transferred to the cell path of the protection path. Virtual path switching method characterized by switching. 2. The virtual path switching method according to claim 1, wherein the transmitting device inserts a switching control cell at the same position of the working virtual path and the backup virtual path in response to a switching request from the receiving device. Virtual path switching method. 3. The virtual path switching method according to claim 1, wherein the transmitting device periodically inserts a switching control cell into the same position of the working virtual path and the backup virtual path, and the receiving device receives the switching request. A virtual path switching method characterized in that switching is performed by the switching control cells of the working virtual path and the backup virtual path that arrive after the occurrence. 4. The virtual path switching method according to claim 1, 2 or 3, wherein the receiving device separates an active virtual path and a backup virtual path of an arbitrary channel into two systems and arrives at each system. A virtual path switching method characterized in that a cell is selected by referring to a table preset for each system for each cell. 5. The virtual path switching system according to claim 4, wherein the two systems share a single phase absorption buffer. 6. The virtual path switching method according to claim 1, wherein a threshold is provided in the phase absorption buffer, and when the buffer capacity of the phase absorption buffer exceeds the threshold, the virtual path switching is stopped as a switching failure. Virtual path switching method. 7. The virtual path switching method according to claim 1, wherein a table for determining whether an arriving cell of the receiving device is a working virtual path cell or a protection virtual path cell is used for management when a failure of the working virtual path is detected. Virtual path switching method characterized by being rewritten by software. 8. The virtual path switching system according to claim 1, wherein a table for determining whether an arriving cell of the receiving device is a working virtual path cell or a backup virtual path cell is used to detect an abnormal notification cell of the working virtual path. Virtual path switching method, which is sometimes rewritten by hardware.