JPH07336360A - Route switching device - Google Patents

Abstract

PURPOSE:To provide a route switching method with improved reliability in an ATM network. CONSTITUTION:At the time of switching a route from an active system 21 to a reserve system 22 by a transmission side switching device 16 and a reception side switching device 17 in the ATM network, a time monitoring circuit 19 for measuring the time from the time when the transmission side switching device 16 performs changeover from the active system 21 to the reserve system 22 is installed. Then, the reception side switching device 17 switches the route from the active system to the reserve system not only by the reception of OAM cells provided with changeover timing information from the transmission side switching device 16 but also signals from the time monitoring circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a route switching device in an ATM network.

[0002]

2. Description of the Related Art In the operation of an ATM network, there are various kinds of switching such as replacement of accommodating transmission lines and paths, system expansion, or switching of a path from an active system to a standby system after failure recovery. For route switching in an ATM network, a method of switching these routes without interruption has been studied. Switching without interruption means switching under the conditions that the order of cells in the path is guaranteed, cell duplication and cell loss are not performed, and a time difference between cells is allowed.

FIG. 6 is a conceptual diagram of the configuration and switching of nodes and transmission lines in an ATM network. 1 to 3 are nodes in the ATM network, 4 is a transmission line connecting the nodes 1 and 2, 5 is a transmission line connecting the nodes 2 and 3, 6 is a node 3 and the node
Working transmission line connecting 1; 7 is a backup transmission line connecting node 3 and node 1; 8 is a path extending from node 1 through working transmission line 6 to node 3; 9 is a transmission line from node 1 The path extends from node 4 to node 3, and then to transmission path 5 to node 3.

Here, the active system is a route such as a transmission line and a path used before the route switching. The backup system is a route such as a transmission line or a path used by switching the route when the working system or the like fails.

In FIG. 6, switching between the active transmission line 6 and the standby transmission line 7 (hereinafter referred to as transmission line switching) between the nodes 1 and 3 or the path 8 extending between the nodes 1 and 3 is performed. It shows the state of switching from to path 9 (hereinafter referred to as path route switching). Transmission path switching is performed by the transmission path switch at the node, and path path switching is performed by the path switch at the node.

[0006] Next, in the ATM network, there is a method of utilizing the switching timing information disclosed in Document 1 as one proposal of the conventional non-instantaneous path switching.

Reference 1: "Uninterruptible switching method in ATM transmission network" by Hideo Kumano and Nobuyuki Tokura, 1990 Spring National Convention of the Institute of Electronics, Information and Communication Engineers, No. B-772 or less Conventional path using switching timing information A method of switching without interruption will be described.

FIG. 7 shows a path which is currently used as a path route passing through a transmission side route switching device (hereinafter referred to as a transmission side switching device) and a reception side route switching device (hereinafter referred to as a reception side switching device) (hereinafter, a working path). And the other one as a spare (hereinafter referred to as a spare path), and the active path to the spare path in this one-to-one configuration (one active path is allocated to one spare path) An example of switching to a path is shown.

In FIG. 7, 10 is a transmitting side switching device for selecting a working path or a protection path, and 11 is a receiving side switching device for switching by selecting a working path or a protection path. 13 is a path in which cells are sent to the transmitting side switching device 10, 14 is an active path between the transmitting side switching device 10 and the receiving side switching device 11, and 15 is a transmitting side switching device 10 and the receiving side switching device 11. A backup system path between them, 16 is a path for sending a cell from the receiving side switching device 11, and 24 is a cell on the path. 12 is installed on the backup system path and near the reception side switching device 11, stores cells on the backup system path, and reads out the cell in the buffer when a signal is received from the reception side switching device 11. Is a buffer circuit for starting. Here, the buffer circuit 12 is necessary to delay the cell when the delay time of the backup path is shorter than the delay time of the working path. Also a buffer circuit
12 can be separated from the backup path.

FIG. 8 is a flow chart of a conventional method for switching from the working path to the protection path. A conventional method of switching from the working path to the protection path will be described with reference to FIGS. 7 and 8. In FIG. 7, first, between the transmission side switching device 10 and the reception side switching device 11, a route from the path 13 to the transmission side switching device 10, the working path 14, and the reception side switching device 11 to the path 16 ( The cells are flowing on the path of route 1). On the other hand, a route from the path 13 to the transmission side switching device 10, the backup system path 15, the reception side switching device 11, and the path 16 is referred to as route 2.

First, the transmission side switching device 10 switches from the working path 14 to the protection path 15 (step 200). The transmission side switching device 10 switches the path and at the same time the active path 14
To the receiving side switching device 11 with a specific cell (hereinafter referred to as OAM cell) having information (hereinafter referred to as switching timing information) that the path is switched from the active system to the standby system (step 201). The receiving side switching device 11 monitors whether or not the OAM cell has been received (step 202). When the receiving side switching device 11 receives the OAM cell, the receiving side switching device 11
Switches from the active path 14 to the backup path 15 (step 203). If the receiving side switching device 11 does not receive the OAM cell, it jumps to step 202.

After processing step 203, the receiving side switching device 11 reads out cells from the buffer circuit 12 installed in the backup path 15 (step 204). When the reading of the cells of the buffer circuit 12 is completed, the buffer circuit 12 disconnects from the backup system path 15 (step 205). In this way, the cells are transferred by the route of route 2, and the path switching from route 1 to route 2 is completed.

[0013]

However, in the above path switching method using the switching timing information, after transmitting the OAM cell on the working path from the transmitting side switching device, the OAM cell disappears due to some cause during transfer. If you do, there is a risk that route switching will fail. For this reason, it is necessary to retransmit the cell, switch the path again, and the like, which causes a problem that the reliability is lowered in the operation of the ATM network.

[0014]

[Means for Solving the Problems]

(1) Therefore, the present invention is from the time when the route is switched from the active system to the standby system and the transmitting side switching device that sends out the specific cell having the switching timing information at this time, and when this transmitting side switching device switches the route. After a certain amount of time,
A route switching device including a time monitoring circuit that sends a time-out signal to a receiving side switching device, and a receiving side switching device that switches a route to a working system or a standby system when a specific cell having switching timing information or a time-out signal is received. is there.

(2) Further, in the above invention (1), a buffer circuit is further provided for storing the cells on the standby system and reading the stored cells in response to a signal from the receiving side switching device. , Cells on the backup system are delayed.

(3) Further, in the invention of the above (1), after the receiving side switching device finishes switching the route, the time measurement of the time monitoring circuit is stopped.

[0017]

[Action]

(1) According to the present invention, since the configuration is as described above, when the path is switched from the active system to the standby system without interruption, the transmission side switching device first switches from the active system to the standby system. At this time, the transmission side switching device sends the OAM cell to the active system, and the time monitoring circuit starts time measurement. When the OAM cell is received, the receiving side switching device switches the path from the active system to the standby system. At this time, if the receiving side switching device cannot receive the OAM cell for some reason, a time-out signal is sent to the receiving side switching device after a certain period of time elapses. The receiving side switching device switches the route from the active system to the standby system by this signal.

[0018]

EXAMPLES The present invention will be described in detail below based on examples. In the present embodiment, switching without path interruption will be described. Figure
1 is an operation explanatory view of a "route switching device" in a normal state for explaining an embodiment according to the present invention, FIG. 2 is an operation explanatory diagram at the time of path switching in the transmission side switching device of the embodiment, and FIG. 5 is an operation explanatory diagram when the path is switched (when an OAM cell is received) in the receiving side switching device of the example; FIG. 4 is an operation explanatory diagram when the path is switched (when the OAM cell is lost) in the receiving side switching device of the embodiment; 6 is a flowchart of a method of switching from a working path to a backup path according to the embodiment.

In FIGS. 1 to 4, 16 is a transmitting side switching device for switching by selecting a working path or a protection path, 17 is a receiving side switching device for switching by selecting a working path or a protection path, 18 is installed on the protection path and near the reception side switching device 17, stores cells from the transmission side switching device 16 on the protection system path, and buffers when there is a signal from the reception side switching device 17. A buffer circuit for starting reading out, 19 starts time measurement from the time when the transmission side switching device 16 performs path switching, and the time to send a timeout signal to the reception side switching device 17 after a certain period of time elapses. It is a monitoring circuit. Here, the buffer circuit 18 and the backup path can be separated.

Reference numeral 20 is a path through which cells are sent to the transmission side switching device 16, 21 is a working path used before switching the route between the transmission side switching device 16 and the reception side switching device 17, and 22 is A backup path that is used as a backup between the transmission side switching device 16 and the reception side switching device 17 after switching the route, 23 is a path connected to the reception side switching device 17, 24 is a cell flowing on the path, and 25 is It is an OAM cell. Here, in FIGS. 1 to 4, the buffer circuit 18 is necessary for delaying the cell when the delay time of the backup path is shorter than the delay time of the working path.

FIG. 1 shows the operation in the normal state. Figure 1
Then, the cell coming from the path 20 passes through the active path 21 by the transmitting side switching device 16 and is sent to the path 23 by the receiving side switching device 17. Here, the path 20 passes through the transmission side switching device 16 and the working path 21, and further passes through the reception side switching device 17 and the path 23.
Route 3 is the route that passes through. Further, a route passing from the path 20 through the transmission side switching device 16 through the backup system path 22, and further through the receiving side switching device 17 through the path 23 will be referred to as route 4.

Next, a series of operations for switching the path route from the route 3 to the route 4 will be described with reference to the flowcharts of FIGS. 2 to 4 and FIG. FIG. 2 shows an operation of switching the working path 21 connected to the path 20 to the protection path 22 by the transmission side switching device 16 (step 300). Therefore, the cell 24 coming from the path 20 passes through the transmission side switching device 16,
It is sent to the backup path 22. Then, the cell 24 is stored in the buffer circuit 18 on the backup path 22. The buffer circuit 18 is a receiving side switching device connected to the buffer circuit 18.
The cell is read by the signal from 17.

Next, the transmission side switching device 16 switches from the working path 21 to the protection path 22, and then sends the OAM cell 25 to the working path 21 (step 301). Here, the transmission side switching device 16 switches the route from the working path 21 to the protection path 22 and then generates an OAM cell 25 to the working path 21.
25 to send. Since the active path 21 and the path 23 are connected in the receiving side switching device 17, the cells on the active path 21 are
The data including the OAM cell 25 is transmitted to the path 23.

At the same time as transmitting the OAM cell 25, the transmission side switching device 16 transmits a signal to the time monitoring circuit 19. As a result, the time monitoring circuit measures the time since the transmission side switching device 16 switched the route from the working path 21 to the protection path 22 (step 302).

FIG. 3 shows a receiving side switching device 17, which is an active path 21.
The operation when the OAM cell 25 flowing from the above is received is shown. Receiving side switching device 17 received O from working path 21
Monitor whether AM cell 25 is received (step 30)
3). Next, when the receiving side switching device 17 receives the OAM cell 25, this means that all the cells sent to the working path 21 have passed through the receiving side switching device 17 and sent to the path 23. There are no cells left on pass 21. Therefore, the receiving side switching device 17 moves from the working path 21 to the protection path.
Switch to 22. (Step 305) Then, the receiving side switching device 17 transmits a signal for reading the stored cell to the buffer circuit 18 connected on the backup path 22. Then, the buffer circuit 18 becomes the transmission side switching device.
The cell transmitted from 16 to the standby system and stored is read (step 306). When the buffer circuit 18 is emptied by reading the cells stored in the buffer circuit 18, the buffer circuit 18 is disconnected from the backup path 22 (step 307), and the cell transmitted from the transmission side switching device 16 is The signal is received by the receiving side switching device without being delayed by the buffer circuit 18.

Further, the receiving side switching device 17 instructs the buffer circuit 18 to read out the stored cells, and at the same time, the receiving side switching device 17 instructs the time monitoring circuit 19 to measure the time for the next time measurement. Stop signal of the time monitoring circuit
19 stops time measurement (step 308). This time measurement is stopped to prepare for the next time measurement. In this way, the route switching from route 3 to route 4 is completed.

Next, a case where the receiving side switching device 17 does not receive the OAM cell 25 in step 303 will be described.
In this case, the time monitoring circuit 19 monitors whether or not the time has expired (step 304). If it has not timed out, jump to step 303.

On the other hand, if a time-out occurs, the step
Jumping to 305, the operation at this time is shown in FIG.
In other words, the fact that the OAM cell 25 is not received and the time-out occurs means that the OAM cell 25 transmitted from the transmission side switching device 17 on the active path 21 has disappeared for some reason. Here, the time measurement by the time monitoring circuit 19 is O
This is performed after the transmitting side switching device 17 sends out the AM cell 25. When a certain time has elapsed from the start of this time measurement, and the signal for stopping the time measurement has not come from the switching device 17 on the receiving side to the time monitoring circuit 19, the time monitoring circuit 19 informs the switching device 17 on the receiving side. And sends a time-out signal.

By this signal, the receiving side switching device 17 switches from the working path 21 to the protection path 22 (step 305),
After that, the procedure from step 306 to step 308 is executed.

In this way, the route switching from route 3 to route 4 is completed.

In the description of this embodiment, the backup system path 22
The case where the buffer circuit 18 is provided in the above has been described, but when the delay time of the working path is shorter than the delay time of the protection path, the buffer circuit is provided near the receiving side switching device 17 on the working path. There may be a circuit. That is, the buffer circuit according to the present invention is installed in the side having a later delay time.

In the description of this embodiment, the path is used as the path, but the method can also be applied to the method of switching the transmission path by replacing the path with the transmission path.

In the description of this embodiment, a 1 + 1 switching example (a configuration in which one spare path is allocated to one working path) is shown, but a switching configuration of 1 + N (working system) is used. Even with a configuration in which one backup path is assigned to multiple paths), specify the destination path to switch to when switching back from a failure (when switching back from the backup path to the active path). It is possible to switch if applicable. In this case, if the delay time of the working path is shorter than the delay time of the protection path, a buffer circuit is required near the receiving side switching device 17 on the working path.

[0034]

As described above, according to the present invention, in the path switching device for switching the path path by the OAM cell, by installing the time monitoring circuit, even if the OAM cell having the switching timing information disappears, the time monitoring circuit can be used. Since the path can be switched by the time-out signal of, the failure of path switching can be avoided. Therefore, the reliability can be improved when the ATM network is operated.

[Brief description of drawings]

FIG. 1 is an operation explanatory view of a “route switching device” in a normal state for explaining an embodiment.

FIG. 2 is an operation explanatory diagram at the time of path switching in the transmission side switching device of the embodiment.

FIG. 3 is a diagram illustrating a path switching (OA) in the receiving side switching device of the embodiment.
Operation explanation diagram (when receiving M cells)

FIG. 4 is a diagram illustrating a path switching (OA) in the receiving side switching device of the embodiment.
Operation explanatory diagram (when M cell disappears)

FIG. 5 is a flowchart of a method for switching from the working path to the protection path according to the embodiment.

FIG. 6 is a conceptual diagram of the configuration and switching of paths and transmission lines.

FIG. 7 is an operation explanatory diagram of switching from a conventional working path to a protection path.

FIG. 8 is a flowchart of a conventional method for switching from the working path to the protection path.

[Explanation of symbols]

1, 2, 3 Nodes 4, 5, 6, 7 Transmission line 8, 9 Paths 10, 16 Transmission side switching device 11, 17 Reception side switching device 12, 18 Buffer circuit 19 Time monitoring circuit 13, 14, 15, 16, 20, 21, 22, 23 Path 24 cells 25 OAM cells

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H04Q 3/00 9371-5K H04L 13/00 311

Claims (3)

[Claims] 1. A transmission side capable of switching from an active system to a standby system as a path for transmitting a cell, and transmitting a specific cell having switching timing information among the cells to the active system when this switching is performed. A route switching device, a time monitoring circuit that measures a time from when the transmission side route switching device switches the route from the active system to the standby system, and transmits a time-out signal after a certain period of time, and receives the cell. Therefore, it is possible to switch the route from the active system to the standby system in response to the switching of the transmission side switching device, and switch the route from the active system to the standby system based on the reception of the specific cell or the timeout signal. A route switching device, comprising: a receiving side route switching device. 2. A reading of the cell that temporarily stores the cell existing on the route on the protection system and is stored based on the reception of the specific cell or the time-out signal by the receiving-side route switching device. 2. The path switching device according to claim 1, further comprising a buffer circuit for performing the soaking. 3. The receiving side path switching device transmits a time measurement stop signal based on the end of switching from the active system to the standby system, and the time monitoring circuit receives the time measurement stop signal. The time measurement is stopped.
The route switching device described.