JP3310495B2 - Instantaneous interruption virtual path switching system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an uninterrupted virtual path switching system, Ru <br/> relates to a hitless virtual path switching system for switching so as not to short break the virtual path.

[0002]

2. Description of the Related Art In recent years, multiplexing is performed by collecting various information in units of a predetermined byte length, adding a header to the information, constructing a cell, and managing the destination of the cell by the header.
Asynchronous transfer mode (ATM) in which a cell is transmitted to a network at an arbitrary time when information is generated and communication is performed.
Is being developed.

Conventionally, in the above-mentioned ATM, transmission lines are switched such that transmission lines between communication devices are duplicated by a system 0 and a system 1 and switched to a system 1 when a current system 0 fails.

[0004]

Even if the physical transmission path is duplicated, in the case of multiple failures of the working / protection transmission path or the failure of the relay device itself, the virtual path accommodated in the transmission path is disconnected. , Cannot be recovered until a detour route is set.

[0005] In ATM, a flexible network can be constructed by introducing the concept of a virtual path (VP) that is set independently of a physical transmission path. For example, as shown in FIG. 10, apart from the working virtual path from the virtual path transmitting apparatus 10 to the virtual path receiving apparatus 12 via the virtual path relaying apparatus 11, the virtual path transmitting apparatus 10 transmits the virtual path
A backup virtual path is provided to reach the virtual path receiving device 12 via 3 and 14. Thus, 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.

Conventionally, however, the setting of a transmission path is performed by an operating system that manages a network, and it takes a long time to set up a detour path. There has been a problem that path switching cannot 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 hitless virtual path switching system that enables instantaneous switching from a working virtual path to a backup virtual path and can reduce the size of a switching device.

[0008]

According to the first aspect of the present invention, switching control cells are inserted at the same position,
Redundant working virtual path and backup virtual path
A virtual path switching system that switches between the working virtual path and the backup virtual path at the position of the switching control cell related to the cell train transmitted using the
The working virtual path and the backup path.
Of each of the virtual paths to each transmitted cell.
Is multiplexed by adding a tag indicating a spare, and the multiplexed
Refer to the table preset for each destination cell and use the current bar.
Determine if the cell is in the Chall pass or the backup virtual path
And, it intends to switch processing line.

[0009] According to a second aspect of the invention, the system switching hitless virtual path according to claim 1, wherein the working bar
One of the virtual pass and backup virtual pass
From the transmission of the switching control cell to the other switching control cell
Phase absorption buffer for storing one of the above cells until transmission
The maximum speed of the capacity of the virtual path to be switched
Read the cell from the phase absorption buffer.

[0010] According to a third aspect of the invention, the system switching hitless virtual path according to claim 2, phase adsorption
Place the cell read from the acquisition buffer in the empty cell position of the main signal.
insert.

[0011] The invention according to claim 4 is the invention according to claim 1 or 3.
In the uninterrupted virtual path switching system described in
One of the working virtual path and backup virtual path
From the transmission of one of the switching control cells, the other switching control cell is transmitted.
Phase absorption buffer that stores one of the above cells until the transmission of the packet.
File according to the capacity of the virtual path to be switched.
The maximum number of cells stored in the phase absorption buffer is varied.
According to a fifth aspect of the present invention, there is provided the virtual path switching system according to the fourth aspect of the present invention , wherein
The phase difference that can be absorbed is converted to the maximum capacity virtual
The maximum delay, which is the maximum phase difference allowed in the path.

[0012]

[0013]

According to the first aspect of the present invention, since the switching is performed by multiplexing the working virtual path and the backup virtual path, only one system is required for the switching, and the apparatus scale can be reduced . Tags are added before multiplexing
By referencing the table, the cell of the working virtual path
It can be easily determined whether the cell is a backup virtual path .

According to the second aspect of the present invention, the reading of cells from the phase absorption buffer is performed at a speed lower than the maximum speed of the capacity of the virtual path to be switched. Overflow can be prevented from occurring in the virtual path.

According to the third aspect of the present invention, the cell read from the phase absorption buffer is inserted into the empty cell position of the main signal, so that the signal cell and the read cell of the phase absorption buffer do not collide with each other. Can be eliminated. According to the fourth aspect of the present invention, since the maximum number of storage cells of the phase absorption buffer is varied according to the capacity of the virtual path to be switched, the maximum delay of the phase absorption buffer can be constant regardless of the capacity of the virtual path to be switched.

According to the fifth aspect of the present invention, since the phase difference absorbed by the phase absorption buffer is set to the maximum phase difference of the virtual path having the maximum capacity, it is possible to prevent the terminal from being regarded as a virtual path disconnection. And the configuration can be simplified.

[0017]

FIG. 2 is a block diagram showing the configuration of a virtual path switching without an instantaneous interruption according to the present invention. In the figure, the virtual path transmitting device 20
Each of the multiplexers (MUX) 21 and 22 multiplexes ATM cells coming from a plurality of external transmission lines and performs VPI
The signals are supplied to the conversion units 23 and 24, respectively. The ATM cell has a predetermined byte length obtained by adding an ATM header to a data portion of a predetermined byte length (48 bytes). VPI converters 23 and 24
Each converts the virtual path identifier (VPI) in the header of each cell according to the path to be transmitted. The cells output from the VPI converters 23 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 25 of the ATM switch 25 are copied.
b. Cells output from the terminal 25a are supplied to interface circuits (IF) 26a and 26b, respectively, and cells output from the terminal 25b are supplied to interface circuits (IF) 27a and 27b. VP
The cells output from the I conversion unit 24 are similarly supplied to another interface circuit (not shown).

The interface circuit 26a is a working virtual path (hereinafter referred to as a "working path").
F) 31a and the interface circuit 26
b indicates the interface circuit 31 by the active path 1 system 28b.
b. Also, the interface circuit 27a
Is connected to the interface circuit 32a of the virtual path receiving apparatus 30 by a backup virtual path (hereinafter referred to as “backup path”) 0a 29a, and the interface circuit 27b is connected to the interface circuit 32b by the backup path 1 system 29b. .

The transmission path switching unit 33 of the virtual path receiving device 30 switches the active path 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 the backup path 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 each of the VPI conversion units 35, 3
6 is converted to a virtual path identifier (VPI) in the header of each cell. Further, the VPI conversion unit 35 adds a tag indicating that the cell is the working path to the header of each cell of the working path, and outputs the result.
Outputs a backup path with a tag indicating that the cell is a backup path added to the header of each cell. It is supplied to 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 cell strings to the virtual path switching unit 38.

FIG. 1 shows a virtual path switching unit 38 according to the present invention.
1 shows a block diagram of one embodiment. In the figure, a cell output from the ATM switch 37 arrives at a terminal 41, and this cell is parallelized by a serial / parallel converter (S / P) 42 and supplied to an abnormality detector 43. Abnormality detector 43
Detects the abnormal state notification cell, the table rewriting unit 51
Notify. The cells that have passed through the abnormality detector 43 are supplied to the OAM cell detector 44 and the VPI filter 46. OA
The M cell detection unit 44 detects a control cell (OAM cell) for maintenance and operation management of the network, and supplies the OAM cell data to the switching control unit 45 if the OAM cell is for virtual path switching. In addition, the VPI filter 46 normally sets the VPI in the cell header for each arrival cell.
Working / protection pass passage table 47 using PI and tags
See The active / backup path passage table 47 stores virtual path identifiers (VPI, VPI is, for example, 12 bits 409).
6) and a tag, and control information is written to instruct whether to pass cells on the working path or cells on the backup path. As a result, during normal operation, cells in the working path are allowed to pass,
If the cell is on the backup path, it is discarded. At the time of uninterrupted switching, cells arriving after the OAM cell for virtual path switching are passed.

The switching controller 45 includes an OAM cell detector 44
Controls the phase absorption buffer 48, the buffer read control unit 49, and the multiplexing unit 52 on the basis of the data of the virtual path switching OAM cell supplied from. The table rewriting unit 51 updates the working / standby path passing table 47 after the virtual path switching is completed.

The phase absorption buffer 48 has a capacity corresponding to the phase difference between the working path and the protection path, and buffers cells output from the VPI filter 46. The buffer read control unit 49 reads cells from the phase absorption buffer 48 under the control of the switching control unit 45.
The multiplexing unit (MUX) 52 multiplexes the cells supplied from the VPI filter 46 and the cells read from the phase absorption buffer 48 under the control of the switching control unit 45, and outputs the multiplexed cells. 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 / protection path passage table 47 from the terminal 60 at the time of failure switching, and notifies the OAM cell detection unit 44 of the virtual path from the terminal 61 at the time of instantaneous interruption switching. Further, the table rewriting unit 51 rewrites the current / protection path passage table 47, that is, the terminal 62
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 at the time of the normal operation executed by the virtual path receiving device 30. In FIG. 3, the header conversion for the highway (HW) for outputting the cell in step S10, that is, the VPI conversion unit 3
A VPI (virtual path identifier) to be converted is set in 5 and 36. Next, in step S12, which path is passed as the current path and which path is discarded as the backup path is set in the current / backup path passage table 47. Steps S10 and S12 are processing performed by the management software of the virtual path receiving device 30.

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

FIGS. 4 and 5 show the virtual path receiving apparatus 30.
5 shows a flowchart of a process at the time of instantaneous interruption switching (forcible switching) executed by. In FIG. 4, when a forced switching request is generated in step S30, the management software of the virtual path transmission device 20 is notified to the OA in step S32.
An M cell transmission request is issued, and an OAM cell standby request is issued to the hardware of the virtual path receiving device 30 in step S34. The above-described 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 processing performed by the management software of the virtual path receiving device 30.

The management software of the virtual path transmission device 20 that 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 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 unit 44, and the virtual path switching unit 38 enters the OAM cell waiting mode in step S36. In this OAM cell waiting mode, the OAM
When the cell detection unit 44 detects an OAM cell, step S3
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 has been received. If the cell is the OAM cell of the working path, the process proceeds to step S42, and the switching control unit 45 stores the cell 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
It is determined whether an M cell has been detected by the OAM detector 44, that is, whether an OAM cell on the backup path has been received. If an OAM cell on the backup path has not been received, step S46 is performed.
Then, the switching control unit 45 determines whether the phase absorption buffer 48 is full, and if not, proceeds to step S44. If an OAM cell on the backup path has been received in step S44, the process proceeds to step S48, where the switching control unit 45 discards the cell stored in the phase absorption buffer 48, and the VPI filter unit 46 deletes cells after the OAM cell on the backup path. It passes through and is supplied to the MUX 52. Thereafter, in step S50, the table rewriting unit 51 sets the current / backup path passage table 4
7 is updated to make the backup path the working path.

Thereafter, the table rewriting section 51 notifies the management software of the table rewriting from the terminal 62 in step S52, and ends the processing. Step S4
If the phase absorption buffer 48 becomes full in step 6, the buffer read control unit 49 reads the cells of the working path stored in the phase absorption buffer 48 in order in step S54,
The signal is supplied to the MUX 52 and mixed with the empty cells of the cell series of the main signal. Thereafter, in step S56, the buffer read control unit 4
9 determines whether or not the phase absorption buffer 48 is empty. If not, the flow advances 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
To separate the phase absorption buffer 48 from the main signal, and then proceeds to step S58 in FIG.
3 notifies the management software of the switching failure and ends the processing.

That is, the cell strings 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 in FIG. Cell rows A ₂ , B ₂ ,
When OAM, C ₂ , and D ₂ are transmitted and cell A ₂ is a copy of cell A ₁ , and the same is applied to the other cells, OA of the working path
The cells C ₁ , D ₁ and MUX 52 of the working path after the M cell are not supplied to the phase absorption buffer 4 as shown in FIG.
8 and the cells C ₂ ,
D ₂ is supplied to MUX52, cell column shown in Graph 1 (D) is output from MUX52. 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 in FIG. 5, and the OAM cell detection unit 44 determines whether an OAM cell on the backup path has been received. If this has not been received, the process proceeds to step S38 in FIG. If an OAM cell on the backup path has been received, the process proceeds to step S62, and the switching control unit 45 stores cells arriving after the OAM cell on the backup 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 detection unit 44. When the OAM cell is detected, the process proceeds to step S66, where V
The PI filter 46 discards cells arriving after the OAM cell of the working path. Further, in step S68, the buffer read control unit 49 sequentially reads the cells of the backup path stored in the phase absorption buffer 48, supplies the read cells to the MUX 52, and mixes them into the empty cells of the cell series of the main signal. In step S70, the buffer read control unit 49 determines whether the phase absorption buffer 48 is empty. If not empty, the flow advances to step S68 to continue reading while storing cells in the backup path in the phase absorption buffer 48 and perform phase absorption. When the buffer 48 becomes empty, the phase absorption buffer 48 is separated from the main signal in step S72, and the cells of the backup path are passed through the VPI filter 46. Then, the process proceeds to step S50 in FIG. I do.

By the way, in step S64, the O of the working path is
If an AM cell has not been received, the switching control unit 45 determines whether the phase absorption buffer 48 is full at step S74, 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 cell shown in FIG.
Row A₁, B₁, OAM, C₁, D_TwoIs transmitted and the spare
Cell row A shown in FIG._Two, B_Two, OAM,
C_Two, D _Two, E_Two, F_TwoIs transmitted and the cell A_TwoIs cell A
₁If you copy the
Cell C after OAM cell_Two, D_TwoIs as shown in FIG.
Stored in the phase absorption buffer 48 and the OAM of the working path.
After the cell arrives, the phase absorption buffer as shown in FIG.
Mixes cells stored in 48 into empty cells of main signal and outputs
Is done. The cell E of the backup path_TwoIs the phase absorption buffer
From cell D_TwoPhase absorption due to incoming
It is stored in the collection buffer 48.

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 and notifies the management software when a signal loss, frame synchronization failure, error rate deterioration, or the like has occurred, and an abnormal state notification cell of the alarm signal VP-AIS. Is generated and sent to the downstream device.
In the first method, the working / backup 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. According to the second method, when the abnormality detecting unit 43 detects the 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 passing table 47 and change the protection path to the working path. Change to a path.

In this manner, the 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 the virtual path relay device 11 of the working path must be stopped to perform maintenance and inspection, etc., the virtual path receiving device 12 issues a forced switching request to the virtual path transmitting device 10,
Instantaneous interruption switching from a working path via the virtual path relay device 11 to a backup path via the virtual path relay devices 13 and 14 can be performed, thereby performing maintenance and inspection of the virtual path relay device 11.

Further, since the working path and the backup path are multiplexed by the ATM switch 37 and supplied to the virtual path switching unit 38, the hardware scale of the virtual path switching unit 38 does not need to be large, and the feasibility is extremely high. . Here, the read control and the write control of the phase absorption buffer 48 will be described in more detail. The virtual path switching unit 38 receives, for example, 2.4 from the ATM switch 37.
Since a high-speed ATM multiplexed signal of Gbps is supplied, it is difficult to predict how much traffic a given virtual path will be at a subsequent low-speed stage, and cells are read out from the phase absorption buffer 48 without limitation. Then, there is a possibility that an overflow occurs when the speed is converted to the low speed stage in the subsequent demultiplexing.

For this purpose, a scheduler 70 shown in FIG. At the time of instantaneous interruption switching, the capacity of the virtual path to be switched is notified from the management software to the scheduler 70 via the terminal 71. When the scheduler 70 is instructed by the switching control unit 45 to read cells from the phase absorption buffer 48 via the terminal 72, the scheduler 70 determines the read interval of the phase absorption buffer 48 based on the notified virtual path capacity.

For example, if the output throughput of the ATM switch 37 is 2.4 Gbps and the capacity of the virtual path to be switched is 155.52 Mbps, the read interval is set to 16
Once per cell, switch virtual path capacity is 7
In the case of 7.78 Mbps, the read interval is set to 1 for 32 cells.
Times. The terminal 73 is connected to the transmission path of the main signal which the VPI filter 46 passes through the cell and supplies to the MUX 52, and the scheduler 70 counts the cell of the main signal. The empty cell detector 74 detects an empty cell of the main signal,
The empty cell detection signal is supplied to the scheduler 70. When the cell count value of the main signal is equal to or longer than the read interval and the empty cell detection signal is supplied, the scheduler 70 generates a read instruction signal for the phase absorption buffer 48 and outputs the signal to the terminal 7.
5 to the phase absorption buffer 48. At the same time, the cell count value of the main signal is reset to zero.

As a result, the output throughput of the virtual path for performing the instantaneous interruption switching does not exceed the capacity of the virtual path in the low-speed stage, and the overflow can be prevented. Further, since cells are read from the phase absorption buffer 48 corresponding to the empty cells, the cell of the main signal and the read cell of the phase absorption buffer do not collide with each other in the MUX 52, and there is no need to provide a queuing buffer in the MUX 52, thereby increasing the hardware. Can be avoided.

Next, the write control will be described. Assuming that the number of cells stored in the phase absorption buffer 48 is a fixed number, the phase difference that can be absorbed by the phase absorption buffer 48 differs depending on the speed of the virtual path for performing instantaneous interruption switching. For example, 50Mb for 100Mbps virtual path
In the virtual path of ps, a double phase difference is accumulated in the phase absorption buffer 48. That is, the maximum delay of the virtual path to be switched in the phase absorption buffer 48 differs depending on the capacity of the virtual path. If the maximum delay becomes too large when the capacity is small, the communication terminal may be regarded as a virtual path disconnection.

For this reason, FIG.
A threshold control unit 80 is provided as shown in FIG. At the time of instantaneous interruption switching, the virtual path capacity to be switched is notified from the management software to the threshold control unit 80 via the terminal 81.
The threshold controller 80 variably sets a threshold for determining whether the phase absorption buffer 48 is full so that the maximum delay is constant according to the virtual path capacity. The determination unit 82 compares the threshold with the number of storage cells in the phase absorption buffer 48 supplied from the terminal 83, and determines that the phase absorption buffer 48 is full when the number of storage cells exceeds the threshold.

The configuration shown in FIG. 9B may be used instead of the configuration shown in FIG. In FIG. 9B, a phase difference counter 90 is provided in the switching control unit 45. Terminal 91
Is connected to the transmission path of the main signal supplied to the MUX 52 by the VPI filter 46, and the phase difference counter 90 counts all the cells of the main signal at the same time as starting to store the cells in the phase absorption buffer 48. I do. That is, the phase difference counter 90 counts the phase difference in the phase absorption buffer 48 by regarding the cell of the main signal as a clock. The determination unit 92 determines that the phase absorption buffer 48 is full when the count value of the phase difference counter 90 exceeds a predetermined threshold. This threshold value is set in the virtual path switching unit 38.
Is a fixed value corresponding to the maximum delay which is the maximum phase difference allowed in the virtual path having the maximum capacity supplied to the virtual path.

For this reason, the phase difference absorbed by the phase absorption buffer 48, that is, the maximum delay is set to a certain time, and the subsequent terminal is not regarded as a virtual path disconnection. Further, the configuration for changing the threshold value is simplified.

[0046]

As described above, according to the first aspect of the present invention, the working virtual path and the backup virtual path are multiplexed and switched, so that only one circuit is required for switching, and the apparatus scale is large. Can be reduced before multiplexing
Tag is added to the current birch by referring to the table
Easily determine whether a cell is in a local path or a spare virtual path
Can be determined.

Further, according to the invention described in claim 2, since the reading of cells from the phase absorbing buffer is performed in the following the maximum speed of the capacity of the virtual path to switch, when converted to the low-speed cross in demultiplexing, Overflow can be prevented from occurring in the switched virtual path.

According to the third aspect of the present invention, since the cell read from the phase absorption buffer is inserted into the empty cell position of the main signal, the signal cell and the read cell of the phase absorption buffer may collide. And no waiting buffer is required. According to the fourth aspect of the present invention, since the maximum number of storage cells of the phase absorption buffer is changed according to the capacity of the virtual path to be switched, the maximum delay of the phase absorption buffer is constant regardless of the capacity of the virtual path to be switched. And can be.

According to the fifth aspect of the present invention, the phase difference that can be absorbed by the phase absorption buffer is set to the maximum delay which is the maximum phase difference of the virtual path having the maximum capacity. This can prevent the possibility of being regarded as disconnection of the path and can simplify the configuration, which is extremely useful in practical use.

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a flowchart of a process at the time of instantaneous interruption switching.

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

FIG. 7 is a signal timing chart for explaining the uninterrupted switching.

FIG. 8 is a block diagram of a buffer read control unit.

FIG. 9 is a block diagram of a switching control unit.

FIG. 10 is a diagram for explaining path duplication.

[Explanation of symbols]

 Reference Signs List 20 virtual path transmission device 23, 24, 35, 36 VPI conversion unit 25, 37 ATM switch 30 virtual path reception device 38 virtual path switching unit 43 abnormality detection unit 44 OAM cell detection unit 45 switching control unit 46 VPI filter 47 working / spare Path passage table 48 Phase absorption buffer 49 Buffer read control unit 51 Table rewriting unit 52 Multiplexing unit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Ota 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Hitoshi Agematsu 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Inside Telegraph and Telephone Corporation (72) Inventor Hiromi Ueda 1-6-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-5-130134 (JP, A) JP-A-5-130 292119 (JP, A) JP-A-4-337935 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 1/22

Claims (5)

(57) [Claims] 1. A switching control cell is inserted at the same position.
It is, at the position of the switching <br/> replacement control cell according to the cell arrays transmitted using current virtual path and the protection Virtual Path which are respectively redundancy, the current virtual path and before
A non- instantaneous virtual path switching system for switching between the backup virtual path and the backup virtual path.
Each cell transmitting each has a working or protection tag.
And multiplexing them, and for each multiplexed arriving cell,
Refer to the set table to set the working virtual path.
Determine cell Le whether the stand-by virtual path, switching hitless virtual path and performs a switching process shea
Stem . 2. The virtual path switching system according to claim 1, wherein the active virtual path and the backup bar are connected.
Transmission of one of the switching control cells with Chalpass
From the above to the transmission of the other switching control cell.
A phase absorbing buffer for storing Le, the position below the maximum speed of the capacity of the virtual path to switch
A non-instantaneous virtual path switching system, wherein cells are read from a phase absorption buffer . 3. The virtual path switching system according to claim 2 , wherein the virtual path is read from the phase absorption buffer.
A non- instantaneous virtual path switching system characterized by inserting a lost cell into an empty cell position of a main signal . 4. The virtual path switching system according to claim 1, wherein the virtual path for the current virtual path and the virtual path for the current path are reserved.
Of one of the virtual path switching control cells
One of the above from transmission to transmission of the other switching control cell
A phase absorbing buffer for storing a cell, the phase absorbing bar according to the capacity of the virtual path to switch
A non-instantaneous virtual path switching system characterized in that the maximum number of cells stored in the buffer is variable . 5. The virtual path switching system according to claim 4, wherein the virtual path can be absorbed by a phase absorption buffer.
Phase difference is allowed in the maximum capacity virtual path transmitted
A non-instantaneous virtual path switching system , wherein the maximum delay is a maximum phase difference .