JPH05227196A - Continuous duplex switching device - Google Patents

Abstract

PURPOSE:To prevent the missing of a reception cell even though a switching call lost in a communication system. CONSTITUTION:The system is provided with #0 and #1 system buffers 30 and 31 capable of transmission delay difference storage, xsi0 and #1 system switching cell detection sections 32 and 33, a selection section 34 selecting the output of the buffers 30 and 31 as the active system at its output, and an access/ switching control section 35 for buffers 30 and 31 based on signals from the sections 32 and 33. When the communication system buffer receiving the switching cells earlier is controlled to remain the reception cells and later and the other system receives switching cells before the amount reaches the threshold value, the switching of the communication system is performed by means of remaining reception cells of the standby buffer. When it exceeds the threshold value, the switching cell is judged to be missed and the missing of reception cells is prevented by using remaining reception cells if there is in the active system buffer without switching the system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention In a communication system having a duplexed communication system and selectively using one of them as an active system, a standby cell system is used to switch to a standby system without interruption when the active system fails. The present invention relates to a non-instantaneous duplex switching device.

In contrast to the conventional communication system based on synchronous time division multiplexing (so-called STM transmission), the concept of statistical cell multiplexing in ATM (asynchronous transfer mode) transmission is new. When the communication system including the communication system of the ATM transmission system is duplicated into the active system and the standby system and the system is switched at the time of a failure, it is necessary from the standpoint of reliability to be able to perform the non-instantaneous duplex switching. That is. Here, the non-instantaneous-duplex switching is to switch the system without duplication or loss of cells.

[0003]

2. Description of the Related Art When a plurality of channels are channel-multiplexed by the STM system, each channel forms a frame structure that appears at regular intervals, so that the phase difference of the frame
Paying attention to the order of multiplexing within a frame and the duplication / missing of cells at the time of switching, non-instantaneous switching can be realized only by selecting a selector.

On the other hand, when a plurality of channels are channel-multiplexed by the ATM system, the multiplexed channels do not form a frame structure. Therefore, only the selection of the selector as in the case of the STM system channel multiplexing described above. In that case, it is not possible to realize non-instantaneous duplex switching.

Therefore, in STM channel multiplexing, A
A method using a switching cell has been proposed as a non-instantaneous duplexing switching method applicable to TM-based channel multiplexing.
FIG. 19 shows a system using this switching cell. As shown in the figure, a communication system of two systems, an active system and a standby system, is provided between the transmitting device A and the receiving device B, and when switching from the active system to the standby system, the transmitting device A is at the position for data switching and the standby system. A switching cell is inserted in both communication systems of the system (Fig. 1
9 (a)). When this switching cell reaches the receiving apparatus B, the cell phases of the active system and the standby system are shifted to some extent ((B) in FIG. 19), but the receiving apparatus B buffers the cells to the extent that this shift can be absorbed. After detecting the switching cell from both the active system and the standby system, pay attention to cell duplication and loss, and select the active system in the front stage of the switching cell and the standby system in the rear stage to select the standby system. Instantaneous disconnection duplex switching is being performed ((c) of FIG. 19).

[0006]

In the case of the above-mentioned switching cell system, it is a necessary condition for switching the system that the receiving device B detects the switching cell in both the active system and the standby system. .. For example, when the receiving device B first detects a switching cell in the active system, after the detection, the receiving device B stops the selective output of the active system and waits for the standby system to detect the switching cell. After the detection of the switching cell in the standby system, the system switching is performed.

However, in the case where the switching cell is lost in the communication path of the standby system, this standby state continues for a long time, and the receiving cells received by the active system during that time are successively discarded. Therefore, even if it is determined to be abnormal after that and the active system is selected and output again, a cell loss occurs during that time.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a reception cell even when a loss of a switching cell occurs in either the working communication system or the protection communication system. It is to prevent the lack of.

[0009]

FIG. 1 shows a principle diagram according to the present invention. As shown in FIG. 1A, the non-instantaneous-duplex switching device according to the present invention is, as one form, a # 0 system buffer 30 capable of accumulating at least a transmission delay difference of reception cells of a # 0 communication system. A # 1 system buffer 31 capable of accumulating at least the transmission delay difference of the # 1 system communication cells; a # 0 system switching cell detection unit 32 for detecting a switching cell from the # 0 system receiving cells; A # 1 system switching cell detection unit 33 which detects a switching cell from the system reception cells, and a selection unit 34 which selects and outputs one of the outputs of the # 0 system and # 1 system buffers 30 and 31 as the active system. ,
Based on the switching cell detection signals from the # 0 system and # 1 system switching cell detection units 32 and 33, the # 0 system and # 1 system buffer 3
A switching control unit 35 that controls access to 0 and 31 and switching control of the selection unit 34.
Controls the reception cells after the switching cell to stay in the buffer of the communication system that received the switching cell first, and the switching cell is received in the other system before the retention amount reaches the predetermined threshold. Occasionally, if there is a stagnation reception cell in the buffer of the backup system at the switching destination, it is used to switch the communication system while absorbing the transmission delay difference. On the other hand, when the stagnation amount exceeds a predetermined threshold, the switching cell Is determined to have occurred, the system is not switched, and if there is a staying reception cell in the buffer of the active system, it is used to prevent the reception cell from being lost.

As another form, the hitless duplex switching apparatus according to the present invention is a hitless duplex switching apparatus for switching a channel-multiplexed communication system of two systems into a hitless duplex switching method. A group of # 0 buffers capable of accumulating at least transmission delay differences for each channel of reception cells of the communication system
# 1 system buffer group capable of accumulating at least transmission delay difference for each channel of # 1 system communication cell, and # 0 system switched cell detection unit group for detecting a switched cell for each channel from # 0 system received cells And a # 1 system switching cell detection unit group that detects a switching cell for each channel from the # 1 system reception cells, and one output of the # 0 system and # 1 system buffers for each channel is selected as the active system. And output # 0
Switching control section for controlling access control of the # 0 system and # 1 buffers and switching control of the selection section for each channel based on the switching cell detection signal from the switching cell detection section The unit controls each channel to hold the received cells after the switching cell in the buffer of the communication system that received the switching cell first, and switches to the other system before the retention amount reaches the predetermined threshold. When a cell is received, if there is a stagnation reception cell in the buffer of the backup system at the switching destination, it is used to switch the communication system for each channel while absorbing the transmission delay difference. When the value exceeds the value, it is judged that the loss of switching cells has occurred and the system is not switched, and if there is a retained reception cell in the buffer of the active system, it is used to control the loss of the reception cell by using it. It is obtained to perform in.

As another embodiment, the hitless duplex switching apparatus according to the present invention includes a # 0 system buffer for temporarily accumulating received cells of a # 0 system communication system and a # 1 system communication system. A # 1 system buffer that temporarily stores received cells, a # 0 system switching cell detection unit that detects a switching cell from # 0 system receiving cells, and a # 1 system receiving cell that detects a switching cell from # 1 system receiving cells # The 1-system switching cell detection unit, the selection unit that selects and outputs one of the outputs of the # 0 system and # 1 system buffers as the active system, and the one receiving cell of the # 0 system and # 1 system is selected. An evacuation buffer unit that can accumulate the received cells in the transmission delay difference,
A switching control unit that performs access control of # 0 system and # 1 system buffers, switching control of a selection unit, and evacuation control of a saving buffer unit based on a switching cell detection signal from a switching cell detection unit of the # 0 system and # 1 system. And the switching control unit performs control to save received cells after the switching cell of the communication system that first received the switching cell to the saving buffer unit, and before the saving amount reaches a predetermined threshold value. When the switching cell is received in the other system as well, if the evacuation buffer section has the evacuation receiving cell of the communication system of the switching destination, it is used to switch the communication system while absorbing the transmission delay difference. When the threshold value is exceeded, it is judged that the switching cell has been lost, and the system is not switched. If there is an evacuation reception cell for the active system in the evacuation buffer, use it to prevent the loss of the reception cell. One in which the.

As shown in (b) of FIG. 1, the non-interruptionless duplex switching apparatus according to the present invention is, as yet another form, a noninterruptive duplexing switching of two channel-multiplexed communication systems. A non-instantaneous-duplex switching device that performs # 0
Of the # 0 system buffer 40 for temporarily accumulating the reception cells of the communication system of the # system, the # 1 system buffer 41 for temporarily accumulating the reception cells of the communication system of the # 1 system, # 0 system switching cell detecting unit 42 for detecting the switching cell for each channel, # 1 system switching cell detecting unit 43 for detecting the switching cell for each channel from the receiving cells of # 1 system, # 0 system,
A selection unit 44 that selects and outputs one output of the # 1 system buffer as a current system for each channel, and selects one receiving cell of the # 0 system and # 1 system for a certain channel and delays transmission of the receiving cell. Saving buffer unit 45 capable of accumulating differences
And access control of the # 0 system and # 1 system buffers 40 and 41, switching control of the selection unit 44, and save buffer based on the switching cell detection signals from the # 0 system and # 1 system switching cell detection units 42 and 43. The switching control unit 46 performs the evacuation control of the unit 45 for each channel, and the switching control unit 46 saves the reception cells after the switching cell of the communication system that previously received the switching cell for a certain channel.
When the switching cell is received in the other system before the amount of the saving reaches a predetermined threshold value, the saving buffer unit 45 uses the saving reception cell of the communication system of the switching destination. The communication system is switched while absorbing the transmission delay difference. On the other hand, when the amount of evacuation exceeds a predetermined threshold, it is judged that the loss of switching cells has occurred and the system is not switched and the evacuation buffer is not used. If there is an evacuation reception cell in the active system, it is used to prevent the reception cell from being lost.

[0013]

In the first embodiment of the switchless duplex switching device, the switching control unit 35 uses the switching cell detection signals from the switching cell detection units 32 and 33 of the # 0 system and the # 1 system, respectively. The access control of the # 1 system buffers 30 and 31 and the switching control of the selection unit 34 are performed. At this time, control is performed so that the receiving cells after the switching cell stay in the buffer of the communication system that received the switching cell first, and the switching cell is also received by the other system before the accumulated amount reaches the predetermined threshold value. At this time, if there is a staying reception cell in the buffer of the standby system at the switching destination, it is used to switch the communication system while absorbing the transmission delay difference. On the other hand, when the staying amount exceeds a predetermined threshold value, it is determined that the switching cell has been lost, and the system is not switched, and if there is a staying receiving cell in the buffer of the active system, the receiving cell is used. Try to prevent missing.

In the non-instantaneous-interruption duplex switching device of the second mode, the switching control unit is based on the switching cell detection signals from the switching cell detection units of the # 0 system and the # 1 system, and the # 0 system,
The access control of the # 1 system buffer and the switching control of the selection unit are performed for each channel. At this time, control is performed to retain received cells after the switching cell in the buffer of the communication system that first received the switching cell for each channel, and the other system also switches before the retention amount reaches the predetermined threshold value. When a cell is received, if there is a staying reception cell in the buffer of the standby system at the switching destination, it is used to absorb the transmission delay difference and switch the communication system for each channel. On the other hand, when the staying amount exceeds a predetermined threshold value, it is determined that the switching cell has been lost, and the system is not switched, and if there is a staying receiving cell in the buffer of the active system, the receiving cell is used. The control is performed for each channel so as to prevent the missing.

In the third embodiment of the switchless duplex switching apparatus, the switching control section is capable of selecting one of the # 0 system and # 1 system receiving cells and accumulating the received cells in the transmission delay difference. Then, access control of the # 0 system and # 1 system buffers, switching control of the selection unit, and evacuation control of the evacuation buffer unit are performed based on the switching cell detection signal from the switching cell detection units of the # 0 system and # 1 system. At this time, control is performed to save the reception cells after the switching cell of the communication system that previously received the switching cell to the saving buffer unit. When the switching cell is received by the other system before the amount of evacuation reaches the predetermined threshold, if there is an evacuation receiving cell of the communication system of the switching destination in the evacuation buffer section, it is used to absorb the transmission delay difference. Switch the communication system. On the other hand, when the saved amount exceeds a predetermined threshold value, it is determined that the switching cell has been lost, and the system is not switched, and if there is an active receiving cell in the save buffer, it is received using that. Try to prevent missing cells.

In the fourth embodiment of the hitless duplex switching apparatus, the switching control section 46 uses the # 0 system based on the switching cell detection signals from the # 0 system and # 1 system switching cell detection sections 42 and 43. , # 1 system buffers 40 and 41 access control, selection unit 44 switching control and save buffer unit 45
Save control is performed for each channel. At this time, for a certain channel, control is performed to save the reception cells after the switching cell of the communication system that previously received the switching cell in the saving buffer unit 45. When the switching cell is received in the other system before the saving amount reaches a predetermined threshold value, the saving buffer unit 45 uses the saving receiving cell of the communication system of the switching destination to absorb the transmission delay difference. While switching the communication system. On the other hand, when the saved amount exceeds a predetermined threshold value, it is determined that the switching cell has been lost, and the system is not switched, and if there is an active receiving cell in the save buffer, it is received using that. Try to prevent missing cells.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an uninterruptible duplex switching device as an embodiment of the present invention. The apparatus of this embodiment has # 0 system and # 1.
Has input ports IP # 0 and IP # 1 for receiving cells from the duplexed communication path of the system, and each input port IP #
The received cells input from 0 and IP # 1 are input into the FIFO memories 1 (0) and 1 (1) as buffer memories, respectively.

The FIFO memories 1 (0) and 1 (1) are memories into which data after serial-parallel conversion of cells received from a communication path are sequentially written, and data is read out under the control of a switching control unit 3 described later. Is configured as
It has a clock transfer function and a data storage function. As a data storage function, it has a memory capacity capable of accumulating a predetermined capacity (usually about 100 cells) of cells capable of absorbing the transmission delay difference between the reception cells passing through the two communication paths.

Reference numerals 2 (0) and 2 (1) denote switching cell detecting units, which detect the switching cell from the data read from the FIFO memories 1 (0) and 1 (1), respectively, and detect the switching cell. It is configured to output a switching cell detection signal to the switching control unit 3. The received cells read from the FIFO memories 1 (0), 1 (1) are the switching cell detection units 2 (0), 2 (1).
Is input to the selector 4 via. The selector 4 is a circuit that selects one of them as an active system according to the switching signal from the switching control unit 3 and outputs it to the output port.

The switching control unit 3 is a switching cell detection unit 2 (0)
FIFO memory 1 based on the detection state of the switching cell from 2 (1) and the states of FIFO memory 1 (0) and 1 (1).
(0), 1 (1) access control and selector 4 switching control are performed.

The operation of the apparatus of this embodiment will be sequentially described below with reference to the time charts of FIGS. 3 to 6 and the flowchart of FIG. Here, assuming that the # 0 system is the active system and the # 1 system is the standby system, the operation when switching the active system from the # 0 system to the # 1 system by the switching cell will be described.

First, as a normal operation without cell loss,
The operation when the active cell # 0 receives a switching cell earlier than the standby cell # 1 will be described with reference to FIG. In FIG. 3, the receiving cells of the # 0 system are shown in uppercase English letters, and the receiving cells of the # 1 system are shown in lowercase letters, of which X is the switching cell in the # 0 system and x is the switching cell in the # 1 system. And

Received cells input from the communication paths of the # 0 system and the # 1 system are sequentially written in the FIFO memories 1 (0) and 1 (1), where the cell phase is controlled under the control of the switching control unit 3. The data is read out while being adjusted, and is input to the selector 4 through the switching cell detection units 2 (0) and 2 (1). At the time when the switching cell is not detected, the selector 4 selects the # 0 system as the active system and outputs the received cell to the output port.

Now, the switching cell X is input to the # 0 system, and the switching cell detection unit 2 (0) detects the switching cell,
It is assumed that the switching cell detection signal is sent to the switching control unit 3. The switching control unit 3 monitors the detection of the switching cell (step S1), and when it is detected, it determines whether the switching cell is the # 0 system or the # 1 system (step S2).

In the example of FIG. 3, the # 0 system switching cell X is detected first. Then, the switching control unit 3 # 0
A read stop control is performed on the system FIFO memory 1 (0) (step S3). This enables the FIFO memory 1
(0) stops the read operation, and sequentially stores the received cells G, H, I, J ... Received after the switching cell X. Further, a vacant cell is inserted in the output from the selector 4 until the reception cell x of the # 1 system is detected (step S4).

Next, when the switching cell x is input to the # 1 system and the switching cell x is detected by the switching cell detection unit 2 (1) in the preceding stage (step S5), the switching control unit 3 causes the selector 4 to operate. The switching control is performed so that the FIFO memory 1 (1) which has been the standby system up to now is selected as the active system. As a result, after the switching cell X, the # 1 system receiving cells g, h, i, j
.. is selected by the selector 4 as the receiving cell of the active system and output to the output port (step S6).

At the time of this switching, the reception cells G, H, which have been buffered in the FIFO memory 1 (0) until then,
I, J ... Are once cleared (step S7), and switching is successful (step S8).

Next, the operation when the # 1 system switching cell x is received before the # 0 system switching cell X will be described with reference to the time chart of FIG. Switching cell x with # 1 system
When it is determined that the data has been detected (step S2), in this case, the reading of the FIFO memory 1 (1) is stopped and the receiving cells g, h, i, j of the # 1 system after the switching cell x are ... Are sequentially stored in the FIFO memory 1 (1).

If the switching cell X is detected in the # 0 system before the accumulated amount of the received cells reaches a predetermined threshold described later (steps S14 and S15), the switching control unit 3 causes the FIFO memory 1 (1 The selector 4 is switched so as to select the read data from (1), and access control is performed so that the accumulated data is read again from the # 1 system FIFO memory 1 (1) which has been stopped. As a result, after detecting the switching cell X in the # 0 system, the switching cell x is detected.
The subsequent receiving cells g, h, i, j of the # 1 system are selected as the active system by the selector 4 and output to the output port.

Similarly to FIG. 3, while the phase of the receiving cell of the # 0 system, which is the active system, is ahead of the phase of the receiving cell of the # 1 system, the switching cell x of the # 1 system, which is the standby system, is The operation when lost in the communication path will be described with reference to FIG.

In this case, after the switching cell X is detected in the # 0 system, the reading of the # 0 system FIFO memory 1 (0) is stopped and the subsequent reception cells G, H, I ... Are accumulated. The operation up to this point is the same as that described with reference to FIG. 3 (steps S1, S2, S3, S4).

However, in the case of FIG. 5, since the # 1 system switching cell x has been lost, the # 1 system switching cell x is not detected forever. Therefore, the storage amount of the reception cells of the FIFO memory 1 (0) gradually increases, and when a threshold is reached (for example, the threshold is set to the storage amount corresponding to the reception cells G to L in FIG. 5), the switching control unit 3 detects this (step S9), notifies the supervisory control system that the loss of the switching cell has occurred to the # 1 system, and requests retransmission of the switching cell (step S10).

Further, the selector 4 is controlled so as to select the receiving cell of the # 0 system as the active system again, and the receiving cells accumulated after the reception of the switching cell X is received for the FIFO memory 1 (0). Access control is performed so that G, H, I, J, ... Are read. As a result, even though the switching cell x of the standby system # 1 is lost, the selector 4 continuously outputs the receiving cells of the active system # 0 without loss. However, the switching has failed (step S12).

Next, as in the case of FIG. 4, while the phase of the receiving cell of the # 1 system which is the standby system is ahead of the phase of the receiving cell of the # 0 system, the switching cell X of the # 0 system which is the active system is The operation when the communication channel is lost will be described with reference to FIG.

In this case, after the switching cell x is detected in the # 1 system, the reading of the FIFO memory 1 (1) is stopped and the subsequent receiving cells g, h, i ... Of the # 1 system are accumulated. The operation up to this is the same as that described with reference to FIG. 4 (steps S1, S2, S13, S14, S15).

However, in the case of FIG. 6, since the # 0 system switching cell X has been lost, the # 0 system switching cell X is not detected forever. Therefore, the storage amount of the reception cells of the FIFO memory 1 (1) gradually increases, and when a threshold is reached (for example, the threshold is set to the storage amount corresponding to the reception cells g to l in FIG. 6), the switching control is performed. The unit 3 detects it (step S9) and notifies the supervisory control system that the loss of the switching cell has occurred in the system # 0 (step S10). Further, the accumulated data in the FIFO memory 1 (1) is cleared (step S19), and the process corresponding to the switching failure is performed (step S20).

In this case, since the switching cell X is not detected in the active system # 0, the selector 4 continues to select the # 0 system as the active system.
Receive cells A, B ... G, H, I ... Of 0 system are continuously output from the selector 4. Therefore, although the switching cell X of the standby system # 0 is lost, the receiving cells of the active system # 0 are continuously output without loss.

Various modifications are possible in carrying out the present invention. FIG. 8 shows an example in which the hitless duplex switching device of the above-described embodiment is modified so that it can be applied to a communication system in which a plurality of channels are multiplexed by the ATM system.

Now, assuming that the number of channels to be channel-multiplexed is N channels, the FIFO memories 1 (0) -1 to 1 (0) -N for # 0 system and # 1 system correspond to these channels.
1 (1) -1 to 1 (1) -N and switching cell detectors 2 (0) -1 to 2
(0) -N, 2 (1) -1 to 2 (1) -N are prepared. Again # 0
Channel identification units 5 (0) and 5
(1) is prepared, the channel of the receiving cell is identified by the channel identifying units 5 (0) and 5 (1), and the receiving cell is distributed to the FIFO memory corresponding to the channel.

Here, in channel multiplexing by ATM,
The multiplexed channels do not form a frame structure, and each channel does not appear at regular intervals. Therefore, the arrangement order of the channels in the active system and the standby system does not match. Also # 0 series and #
It depends on each channel which one of the systems is the active system. For example, when there are four channels A, B, C, D, for channels A, B, C, the # 0 system is the active system,
For channel D, the # 1 system is the active system. Non-instantaneous duplex switching by a switching cell is also performed for each channel. For example, by inserting a switching cell into channel A for only channel A among channels A, B, and C of the active system # 1 system. Processing such as switching to.

In the non-instantaneous-duplex switching device of FIG. 8, the switching control unit 6 includes a selector 7 for each channel, and a # 0 system and a # 1 system.
Switching control is performed so that one of the systems is selected as the active system and output to the output port. Since the operation of the non-instantaneous-duplex switching by the switching cell in each channel is the same as that in the above-mentioned embodiment, detailed description will be omitted here.

As described above, according to the hitless duplex switching apparatus of FIG. 8, it is possible to perform the hitless duplex switching even in a communication system which handles signals multiplexed in channels by the ATM system. However, the apparatus shown in FIG. 8 requires FIFO memories having a large memory capacity for the number of channels × 2. For this reason, a non-instantaneous disconnection duplex switching device can be integrated into a single LSI.
However, there is a problem that it is difficult to do so because the circuit scale of the FIFO memory is large.

FIG. 9 shows an embodiment of the non-instantaneous disconnection duplexing switching device of the present invention which solves such a problem. The device of this embodiment is capable of switching the signals multiplexed in the channel by the ATM system without interruption, and reducing the capacity of the FIFO memory so that it can be mounted on a one-chip LSI.

In FIG. 9, input ports IP # 0, IP
The received cells of the # 0 system and the # 1 system respectively input to # 1 are input to the channel identification units 11 (0) and 11 (1) via the FIFO memories 10 (0) and 10 (1), respectively. Here, the FIFO memories 10 (0) and 10 (1) are buffer memories for clock transfer, have a memory capacity of about several cells, and function to match the cell phase in the device. Processing is facilitated. The channel identification units 11 (0) and 11 (1) are circuits for identifying the channels of the reception cells of the respective systems, and the identification result is notified to the switching control unit 16.

The reception cells of the systems # 0 and # 1 that have passed through the channel identification units 11 (0) and 11 (1) are further passed through the switching cell detection units 12 (0) and 12 (1) to the FIFO memory 13.
It is input to (0) and 13 (1). This FIFO memory 13
In (0) and 13 (1), under the control of the switching control unit 16, the reception cells of the channels which are the active system in the respective systems # 0 and # 1 are accumulated. FIFO
The reception cells read from the memories 13 (0) and 13 (1) are configured to be input to the selector 15 via the switching cell detection units 14 (0) and 14 (1), respectively.

Here, the switching cell detectors 12 (0), 12
Reference numerals (1), 14 (0), and 14 (1) are circuits for detecting the switching cells and supplying the detection signals to the switching control unit 16, respectively. The FIFO memories 13 (0) and 13 (1) are buffer memories for buffering the received cells of several cells. The write / read control of these FIFO memories 13 (0) and 13 (1) is performed by the switching control unit 16 so that only the receiving cells of the active system are buffered in each system # 0 and # 1. ..

The reception cells of the systems # 0 and # 1 via the channel identification units 11 (0) and 11 (1) are also input to the selector 17, and one of the systems is controlled by the switching control unit 16. Only a specific channel of is selected by the selector 17 and input to the save FIFO memory 18 for storage. The save FIFO memory 18 is a memory for temporarily saving the receive cells of the channel for switching the system at the time of switching, and is a memory equivalent to the transmission delay difference between the cells passing through the # 0 system and the # 1 system. Capacity (usually
Have about 100 cells).

The switching controller 16 identifies the channel, detects the switching cell, and the FIFO memories 13 (0), 13 (1),
Based on the state of the accumulated amount of 18, the FIFO memory 13
(0), 13 (1), 18 access control and selector 1
5 is a circuit for controlling switching. FIFO memory 13
The access control of (0), 13 (1) and 18 is performed by so-called skip polling. In this skip polling, when sequentially reading data from the FIFO memories 13 (0), 13 (1), and 18, a search is performed for the free state of each FIFO memory, and the read from the empty memory is skipped ( That is, skip it). As a result, when switching a certain channel, it becomes possible to efficiently and quickly read the stored data in the save FIFO memory 18 and release it, as will be described later in detail.
Therefore, it becomes possible to quickly switch the next channel.

Further, the switching control of the selector 1 by the switching control unit 16 is normally performed in a channel unit. That is, switching control is performed so that # 0 system is selected and output as the active system for a certain channel of the multiplexed channels, and # 1 system is selected and output as the active system for other channels. ..

The operation of the apparatus of this embodiment will be described below with reference to the time charts of FIGS. 10 to 13 and the flow charts of FIGS. 14 to 8. In the time charts of FIGS. 10 to 13, four channels A, B, C and D are assumed to be ATM channel multiplexed. # 0 cells are capital letters A, B, C, and D with cell order.
The cells of the 1-system are represented by symbols with lowercase letters a, b, c and d with cell order. Here, it is assumed that the # 0 system is the active system for each of the A, B, and C channels and the # 1 system is the active system for the D channel.
The operation when switching from the system to the # 1 system will be described.

Further, the flow charts of FIGS.
It is the flowchart which showed the processing procedure on the basis of the 0 system side circuit, and when showing the processing procedure on the basis of the # 1 system side circuit, # 0 and # 1 in FIGS. In addition, the coupling terminals (1) to (3) in FIG. 14 represent the following states. When the # 0 system is the active system and the # 0 system is earlier than the # 1 system (processing of FIG. 15) The # 0 system is the active system and # 1 system is earlier than the # 0 system (processing of FIG. 16) # 1 When the system is the active system and the # 1 system is earlier than the # 0 system (processing of FIG. 17) The # 1 system is the active system and # 0 system is earlier than the # 1 system (processing of FIG. 18)

First, referring to the time chart of FIG. 10, regarding the A channel, the # 0 system switching cell A2 is
The normal operation when detected earlier than the 1-system switching cell a2 will be described. Here for channel A
2 and a2 are switching cells.

When cells are input to each of the input ports IP # 0 and IP # 1, they are input to the FIFO memories 10 (0) and 10 (10).
Channel identification units 11 (0), 11 via (1) respectively
Channel identification is performed by inputting to (1) (step S
20-23). Based on this identification result, the switching control unit 16 performs access control so that only the cells of the active channel in each system # 0, # 1 are written in the FIFO memories 13 (0), 13 (1). That is, the FIFO memory 13
In (0), only the input cells of each channel of A, B, and C are written, and the reception cells of D channel are not written.
Only the reception cells of the D channel are written to the FIFO memory 13 (1), and the reception cells of the channels A, B and C are not written (steps S21 to S27).

These FIFO memories 13 (0) and 13 (1)
The reception cell written in the
The data is appropriately read by skip polling by and is sequentially output to the output port via the selector 15.

Eventually, the switching cell A of the A channel is connected to the # 0 system.
2 is input and detected by the switching cell detection unit 11 (0),
When this is notified to the switching control unit 16, the switching control unit 16 controls to store the switching cell A2 in the FIFO memory 13 (0). Then, regarding the reception cells A3, A4, ... Of the A channel after the switching cell A2, writing to the FIFO memory 13 (0) is prohibited, and
The save FIFO memory 1 for them via the selector 17.
The selector 17 is switched so that the data is stored in the memory 8 and the reading from the save FIFO memory 18 is prohibited.

As for the other B and C channels, they are written in the FIFO memory 13 (0) as before (steps S32 to S36).

Following the A-channel switching cell A2 of the # 0 system, the A-channel switching cell a2 is input to the # 1 system. Then, the switching cell detection unit 12 (1) detects this and notifies the switching control unit 16. The switching control unit 16 monitors the amount of A-channel reception cells accumulated in the evacuation FIFO memory 18, and determines whether the switching cell a2 is received by the # 1 system before the accumulated amount exceeds a certain threshold, which will be described later. It is determined (step S37).

When the switching cell a2 is detected before the threshold is exceeded (step S41), control is performed to switch the active system of the A channel from the # 0 system to the # 1 system. That is, after receiving the switching cell a2, the receiving cells a3, a4, ...
It is written in the IFO memory 13 (1) and is sent to the output port via the selector 1 (step S42). Further, the saving FIFO memory 18 is cleared (step S43), and the receiving cells A3, A4, ... In this way, the switching is successful.

Next, referring to the time chart of FIG. 11, regarding the A channel, the switching cells of the A channel are designated as A3 and a3, and the switching cell a3 of the # 1 system is faster than the switching cell A3 of the # 0 system. The normal operation when detected will be described.

The write operation of the received cell to the FIFO memories 13 (0) and 13 (1) before the detection of the switching cell is as described above. When the A-channel switching cell a3 is input to the # 1 system and is detected and notified to the switching control unit 16, the switching control unit 16 receives the # 1 system receiving cells a4 and a5 after the switching cell a3. .. is controlled to be saved in the save FIFO memory 18. It should be noted that the flowcharts of these operations are obtained by rewriting FIGS. 14 to 18 with reference to the # 1 system side circuit.

Eventually, the switching cell A of the A channel is connected to the # 0 system.
When 3 is input and is detected by the switching cell detection unit 14 (0) in the subsequent stage through the FIFO memory 13 (0) (step S49), reading from the save FIFO memory 18 is started (step S49). S50), the receiving cell a of the # 1 system
Are sequentially transmitted to the output port via the selector 15. This processing is performed by the save FIFO memory 18
Is continued until is empty (step S51). When the save FIFO memory 18 becomes empty, the switching control unit 16 performs channel switching so that the active channel of the A channel becomes the # 1 system (step S52).

By starting the reading of the save FIFO memory 18 after detection by the switching cell detection unit 14 (0) in the subsequent stage, the switching cell A3 and the subsequent receiving cells a4 of the # 1 system,
The cell order can be maintained so that a5 ...

Next, when the # 0 system switching cell is detected earlier than the # 1 system switching cell as shown in FIG. 10, the # 1 system A channel switching cell a2 is used as the transmission path. The operation at the time of failure when switching fails because of loss will be described below with reference to the time chart of FIG.

After detecting the A channel switching cell A2 in the # 0 system, the switching control unit 16 monitors whether or not the A channel switching cell a2 in the # 1 system is detected, but the switching cell a2 is lost. This detection is not performed because it has occurred. Then, the storage amount of the receiving cells A3, A4, ... Of the A channel of the # 0 system saved in the save FIFO memory 18 gradually increases, and eventually exceeds the predetermined threshold (step S37). Note that, in the example of FIG. 12, the threshold is set as the accumulated amount corresponding to the receiving cells A3 to A5 for simplification of the description, but in general, the cell loss etc. is considered in consideration of the transmission delay of the cells on the working and protection communication paths. It is set to the amount that can be judged to have occurred.

As a result, the supervisory control system is notified that there is a cell loss, and a retransmission request for the switching cell is issued.
(Step S38). Then, the switching control unit 16 starts reading from the save FIFO memory 18 and controls so as to read the saved receive cells A3, A4 .... This reading is performed by the FIFO memory 13 as described above.
(0), 13 (1), and 18 are performed by skip polling. A until the save FIFO memory 18 becomes empty
Write the receive cell of the channel to the FIFO memory 18,
When the save FIFO memory 18 becomes empty, the switching control unit 16 will save the save FIFO memory 18 for the A channel.
To the receiving cell A of the subsequent A channel.
6 ... Controls writing to the FIFO memory 13 (0) again.

As described above, although the switching of the A channel has failed, the reception cells A3 to A5 of the A channel received during the switching period are saved and saved in the saving FIFO memory 18, so that the missing cells are deleted. It can be prevented.

Further, when the # 1 system switching cell is detected earlier than the # 0 system switching cell as shown in FIG. 11, the # 0 system A channel switching cell A is detected.
The operation at the time of failure when switching fails because 3 is lost on the transmission path will be described below with reference to the time chart of FIG.

After detecting the A-channel switching cell a3 in the # 1 system, the switching control unit 16 saves the subsequent A-channel receiving cells a4, a5 ... In the # 1 system to the save FIFO memory 18. While monitoring whether or not the switching cell A3 of the # 0 system A channel is detected, this detection is not performed because the switching cell A3 has been lost. Then, the storage amount of the receiving cells a4, a5, ... Of the # 0 system A channel saved in the save FIFO memory 18 gradually increases, and eventually exceeds a predetermined threshold (step S37). Note that, in the example of FIG. 13, the threshold is set as the accumulated amount corresponding to the receiving cells a4 to a7 for simplification of the description, but similarly to the above, in general, in consideration of the transmission delay of the cells in the working and protection communication paths, The amount is set so that it can be determined that a failure such as cell loss has occurred.

As a result, it is determined that the # 0 system A channel switching cell A3 has been lost in the communication system, and the supervisory control system is notified of the cell loss.
Then, the switching control unit 16 sets # 0 for the A channel.
Do not switch channels while keeping the system active. The contents of the save FIFO memory 18 are cleared.

As described above, according to the hitless duplex switching apparatus having the configuration as shown in FIG. 9, compared with the hitless duplex switching apparatus having the configuration as shown in FIG. Even in the case of performing the momentary interruption duplex switching, the memory capacity of the delay difference is required for each FIFO in the apparatus of FIG. 2, whereas the memory capacity of the delay difference is prepared only for the save FIFO memory in the apparatus of FIG. Since it is sufficient, the memory capacity can be significantly reduced. Particularly when channel multiplexing is performed by ATM, the transmission delay difference (for example, 10
0 cells) is required twice as many as the number of channels,
In the apparatus shown in FIG. 9, the number of FIFOs for the transmission delay difference is one, and thereafter, only the FIFO having the memory capacity of several cells for timing adjustment is sufficient. By drastically reducing the amount of memory in this way, it is possible to realize a single chip when the device is integrated into an LSI.

The above-described non-instantaneous-interruption duplex switching device of FIG. 9 has only one evacuation FIFO memory 18, so that only one channel can be switched at a time. However, the present invention is not limited to this, and the selector 17 and the save FIFO are also provided.
It is also possible to switch a plurality of channels at once by preparing a plurality of memories 18 and saving reception cells of different channels in each memory.

Although the non-instantaneous-duplex switching device shown in FIG. 9 has been described as a non-instantaneous-duplex switching device for channel-multiplexed signals, it is, of course, a non-interruptive-duplex switching device for signals not channel-multiplexed. May be.

[0073]

As described above, according to the present invention, even if the switching cell is lost in either the working communication system or the protection communication system, the reception cell may be duplicated or dropped. Without this, it is possible to switch channels without interruption.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing a hitless duplex switching device as an embodiment of the present invention.

FIG. 3 is a time chart of a switching operation at a normal time by the apparatus of the embodiment (when the # 0 system is the active system and the # 0 system is earlier than the # 1 system).

FIG. 4 is a time chart of a switching operation at a normal time by the apparatus of the embodiment (when the # 0 system is the active system and the # 1 system is earlier than the # 0 system).

FIG. 5 is a time chart of the switching operation at the time of a failure by the device of the embodiment (when the # 0 system is the active system, the # 0 system is earlier than the # 1 system, and the switching cell of the # 1 system is lost).

FIG. 6 is a time chart of the switching operation at the time of a failure by the device of the embodiment (when the # 0 system is the active system, the # 1 system is earlier than the # 0 system, and the # 0 system switching cell is lost).

FIG. 7 is a flowchart showing a processing procedure of the embodiment apparatus.

FIG. 8 is a diagram showing an embodiment of a hitless duplex switching device modified so that the device of FIG. 2 is applied to a channel-multiplexed communication system.

FIG. 9 is a diagram showing a hitless duplex switching device as another embodiment of the present invention.

10 is a time chart of a switching operation in a normal time by the apparatus of the embodiment of FIG. 9 (the # 0 system is the active system, and the # 0 system is the # 1 system).
It is earlier than the system).

FIG. 11 is a time chart of a switching operation in normal time by the apparatus of the embodiment of FIG. 9 (# 0 system as an active system, # 1 system as a
It is earlier than the system).

FIG. 12 is a time chart of the switching operation at the time of a failure by the apparatus of the embodiment of FIG. 9 (the # 0 system is the active system, and the # 0 system is the # 1 system).
This is the case when the switching cell of the # 1 system is lost earlier than the system).

FIG. 13 is a time chart of the switching operation at the time of a failure by the apparatus of the embodiment of FIG. 9 (the system # 0 is the active system and the system # 1 is # 0).
This is the case when the switching cell of # 0 system is lost earlier than the system).

FIG. 14 is a flowchart showing a part of the processing procedure of the embodiment apparatus of FIG.

15 is a flowchart showing a part of the processing procedure of the apparatus of the embodiment in FIG.

16 is a flowchart showing a part of the processing procedure of the embodiment apparatus of FIG.

FIG. 17 is a flowchart showing a part of the processing procedure of the apparatus of the embodiment in FIG.

FIG. 18 is a flowchart showing a part of the processing procedure of the embodiment apparatus of FIG. 9;

FIG. 19 is a diagram for explaining non-instantaneous duplex switching by the switching cell method.

[Explanation of symbols]

1 (0), 10 (0), 13 (0) # 0 system FIFO memory 1 (1), 10 (1), 13 (1) # 1 system FIFO memory 2 (0), 12 (0), 14 (0) # 0 system switching cell detection unit 2 (1), 12 (1), 14 (1) # 1 system switching cell detection unit 3, 6, 16 Switching control unit 4, 7, 15, 17 Selector 5 (0), 11 (0) # 0 channel identification section 5 (1), 11 (1) # 1 channel identification section 18 Save FIFO memory

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Setsu Fukuda 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Hiroshi Ota 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Incorporated (72) Inventor Hiromi Ueda 1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (7)

[Claims] 1. A # 0 system buffer (30) capable of accumulating at least transmission delay difference cells of a # 0 communication system, and a # 1 system buffer capable of accumulating at least transmission delay difference cells of a # 1 communication system. (31), a # 0 system switching cell detecting unit (32) that detects a switching cell from the # 0 system receiving cell, and a # 1 system switching cell detecting unit that detects a switching cell from the # 1 system receiving cell (33), a selection unit (34) for selecting and outputting one output of one of the # 0 system and # 1 system buffers as an active system, and a switching cell detection unit for the # 0 system and # 1 system. A switching control unit (35) for controlling access to the # 0 system and # 1 system buffers and switching control of the selection unit based on the switching cell detection signal, the switching control unit receiving the switching cell first. In the buffer of the communication system When the receiving cell is controlled in the buffer of the standby system to be switched to when the switching cell is received in the other system before the retention amount reaches the predetermined threshold, The communication system is switched while absorbing the transmission delay difference by using it. On the other hand, when the staying amount exceeds a predetermined threshold, it is judged that the loss of the switching cell has occurred and the system is not switched and it is in use. A non-instantaneous-duplex switching device that prevents reception cells from being lost by using the accumulated reception cells in the system buffer. 2. A non-instantaneous-duplex switching device for switching two channel-multiplexed communication systems into a non-instantaneous-duplex switching mode, wherein at least transmission delay difference accumulation is performed for each channel of receiving cells of a # 0 communication system. Possible # 0 system buffer group, # 1 system communication group that can accumulate at least the transmission delay difference of # 1 system communication cells for each channel, and Detect switching cells for each channel from # 0 system reception cells # 0 system switching cell detection unit group, # 1 system switching cell detection unit group that detects a switching cell for each channel from received cells of # 1 system, and buffers of the # 0 system and # 1 system for each channel A selection unit that selects and outputs one output as an active system, and access control of the # 0 system and # 1 system buffers based on a switching cell detection signal from the # 0 system and # 1 system switching cell detection units. And switching of the selection unit And a switching control unit that performs control for each channel, the switching control unit performing control to retain the received cells after the switching cell in the buffer of the communication system that previously received the switching cell for each channel. When the switching cell is received by the other system before the retention amount reaches the predetermined threshold, if there is a retention reception cell in the buffer of the standby system at the switching destination, it is used to absorb the transmission delay difference and Switching is performed for each channel. On the other hand, when the accumulated amount exceeds a predetermined threshold value, it is judged that the switching cells have been lost, and the system is not switched and there is a remaining receiving cell in the active buffer. For example, a non-instantaneous-duplex switching device that uses it to perform control to prevent the loss of received cells for each channel. 3. A # 0 system buffer for temporarily accumulating reception cells of a # 0 communication system, a # 1 system buffer for temporarily accumulating reception cells of a # 1 communication system, and a # 0 system. The # 0 system switching cell detection unit that detects the switching cell from among the receiving cells of # 1, the # 1 system switching cell detection unit that detects the switching cell from the # 1 system receiving cells, and the # 0 system and # 1 system A selection unit for selecting and outputting one output of the buffer as an active system; an evacuation buffer unit capable of selecting one of the # 0 system and # 1 system receiving cells and accumulating the received cells in the transmission delay difference; The access control of the # 0 system and # 1 system buffers, the switching control of the selection unit, and the evacuation control of the save buffer unit are performed based on the switch cell detection signal from the switch cell detection units of the # 0 system and # 1 system. And a switching control unit, and the switching control unit first The control is performed to save the received cells after the switching cell of the communication system that received the message to the saving buffer unit, and when the other cell receives the switching cell before the saving amount reaches the predetermined threshold, the saving is performed. If there is an evacuation receiving cell of the communication system of the switching destination in the buffer section, it is used to switch the communication system while absorbing the transmission delay difference, and when the evacuation amount exceeds the predetermined threshold, the switching cell A switchover device for a non-instantaneous-interruption system, which judges that the loss of data has occurred and does not switch the system and prevents the loss of the received cell by using the saved receive cell of the active system in the save buffer. 4. A non-instantaneous-duplex switching apparatus for switching two channel-multiplexed communication systems into a non-instantaneous-duplex switching mode, wherein a # 0 system for temporarily accumulating reception cells of a # 0 communication system is provided. A buffer (40), a # 1 system buffer (41) for temporarily storing communication cells of the # 1 communication system, and a # 0 system switching cell for detecting a switching cell for each channel from the # 0 system reception cells A detection unit (42), a # 1 system switching cell detection unit (43) that detects a switching cell from the # 1 system reception cells for each channel, and one output of one of the # 0 system and # 1 system buffers. Separately, a selection unit (44) for selecting and outputting as an active system, and an evacuation buffer unit (45) for selecting one receiving cell of the # 0 system or # 1 system for a certain channel and accumulating the transmission delay difference of the receiving cell ), And switching between the # 0 system and # 1 system A switching control unit (46) that performs access control of the # 0 system and # 1 system buffers, switching control of the selection unit, and evacuation control of the evacuation buffer unit for each channel based on a switching cell detection signal from the channel detection unit. The switching control unit controls, for a certain channel, the reception cells after the switching cell of the communication system that previously received the switching cell to be saved in the saving buffer unit, and the saving amount is set to a predetermined threshold. When the switching cell is received in the other system before reaching the value, if there is an evacuation receiving cell of the communication system of the switching destination in the evacuation buffer section, it is used to switch the communication system while absorbing the transmission delay difference. On the other hand, when the saved amount exceeds a predetermined threshold value, it is determined that the switching cell has been lost, and the system is not switched. Uninterruptible duplexed switching apparatus so as to prevent missing reception cell used. 5. The non-instantaneous-interruption duplexing switching device according to claim 4, wherein the save buffer units are provided for the number of channels for simultaneously switching the system, and the save control is performed for each channel. 6. The non-instantaneous-interruption duplexing switching device according to claim 3, wherein reading from the # 0 system buffer and the # 1 system buffer and the save buffer unit is performed by skip polling. 7. The non-instantaneous-interruption duplex switching device according to claim 3, wherein a buffer for adjusting a cell phase of a reception cell in the device is provided in an input section from two communication systems.