JPH0498944A - Path changeover system without short break - Google Patents

Abstract

PURPOSE:To change over paths without giving effect on information transferred on the path, without short break by providing a self-routing switch, a time stamp function, a delay compensation cell and a changeover cell. CONSTITUTION:A control node 1 commands a path switching time to each of monitor drivers 11,21. The information is written in a cell 32 and transferred. When changeover is commanded from the control node 1, a sender node 10 confirms it that a standby path 34 is available. In this case, the sender side node 10 inserts a cell having information as to propagation delay measurement start time to an active path 33 and the standby path 34. A receiver side node 20 awaits the arrival of a propagation delay measurement cell sent from the active path 33 and the standby path 34 when changeover is commanded from the control node. When the propagation delay measurement cell is reached, the propagation delay between both is calculated based on the difference of the arrival times. The receiver side node 20 writes the propagation delay information and informs it to the sender node 20 via the control node 1. The sender node 10 starts changeover at the path changeover time.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention provides an ATM (Asynchronous
The present invention relates to a non-interruption path switching method that performs path switching without affecting information being transferred on the path when a path is switched in a transfer mode (transfer mode) network, for example due to trouble relocation.

(Prior art) Conventional STM (Sychronous Tran)
Regarding the path switching method in the STM network (Srer Mode) network, the configuration diagram of the path switching method of the STM network shown in FIG.
This will be explained with reference to the internal structure diagram of the switch (STM-3W) in the STM network shown in the figure and the path switching flow shown in FIG.

In the path switching method in an STM network, a control node 101 that centrally monitors the network uses monitoring drive devices 1 in nodes 100 and 200 on the transmitting and receiving sides of the path to be switched.
10. -210 is given a path switching instruction, and the monitoring/driving device 110 that receives the instruction processes the process via software and actually drives the STM-3W12, 22, thereby performing path switching. . At this time, S
The TM-SW has a matrix structure as shown in FIG. 8, and when it receives a path switching instruction, it switches from the contact 14 connected to the working path to the contact 15 connected to the protection path.

In the conventional technology described above, in order to realize uninterrupted path switching, the following two delay times occur.

(2) The first delay is a delay due to the difference in propagation time after the control node instructs path switching until the information reaches the monitoring drive device in the sending and receiving nodes. Due to this delay, both monitoring and driving devices are unable to receive the information sent by the control node instructing switching at the same time, resulting in a difference in the switching times of the STM-SWs.

(2) The second delay is a delay that occurs because the propagation time of information transferred between the nodes at both ends of the path to be switched is different between the working path and the backup path.

Because of this delay, even if the STM-SWs at both ends of the path switch at the same time, the receiving node will
A shift occurs in the position of the received information.

Further, since the switch STM-8W in the conventional STM performs processing via software, it takes about 5 ms from receiving a switching instruction to actually executing switching.

(Problems to be Solved by the Invention) In the conventional STM network, as described above, problems arise due to delays due to differences in propagation time to the monitoring drive device and delays due to differences in propagation times between paths. Problems due to delay time also exist in ATM networks,
If paths are simply switched without taking any measures in an ATM network, there is a problem in that instantaneous interruptions (packet loss) occur.

Furthermore, if the same switch is used in an ATM network as in an STM network, it will take approximately 5 ms to perform switching.
There are problems in that it takes a long time and instantaneous interruptions occur.

The present invention has been made in view of the above, and its purpose is to provide an uninterrupted path switching system that can accurately switch paths without interruption in an ATM network. .

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the uninterruptible path switching system of the present invention is an uninterruptible path switching system for switching paths in an ATM network, in which a transmitting node and a receiving node In addition to providing the side node with a self-routing φ switch and a time stamp function, a delay compensation cell that compensates for the difference in propagation time between the two nodes and a switching cell that serves as a reference for path switching are provided, thereby eliminating timing deviations in path switching. The main purpose of this system is to compensate for the difference in cell propagation and transit time between the working path and the backup path, and to perform path switching without momentary interruption without affecting the information transferred on the path.

(Function) In the uninterrupted path switching method of the present invention, self-routing
A switching cell and a delay compensation cell are used between a switch and a node with a timestamp function to compensate for the timing difference in path switching and the difference in propagation time of cells flowing on the working path and the protection path. Path switching is performed without any interruption, without affecting the information being transmitted.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of an uninterrupted path switching system applied to an ATM network according to an embodiment of the present invention, and FIG.
Switch used in the ATM network in Figure 1 (ATM-SW)
1 is a diagram illustrating the principle of a self-routing switch that constitutes a

1 and 2, 1 is a control node, 10 is a sending node, 20 is a receiving node, 32 is an input path,
33 is the working path, 34 is the backup path, 35 is the output path, 1
1.21 is a monitoring drive device, 42 is a transmitting side ATM-SW,
43 is a receiving side ATM-8W, 30 is time information, 31 is a routing table, LT is a line termination device, 44 is a self-routing switch, 50 is routing information, 51
゜52 is a unit switch.

The uninterrupted path switching method shown in Figure 1 solves the conventional problems by
It is characterized by using a switch 44, (1) delay compensation cell, and (2) switching cell. Next, each of these features will be explained.

■Time stamp is one of the operations that uses time information synchronized between each node in the network.

For example, if the transmitting node 10 sends out a cell with time information, the receiving node 20 compares the time information of the cell with its own time information, thereby determining the cell information between the two nodes. Propagation time can be measured.

■The self-routing switch 44 adds a routing information to the beginning 50 of the cell header as shown in FIG.
The 0.1 bit information is transferred to each unit switch (for example, 51.
52) is a switch that sequentially autonomously reads cells and performs cell routing.

(2) A delay compensation cell is a cell inserted to compensate for the difference in propagation time between cells flowing through the working path 33 and protection path 34. If this delay compensation is not performed, the cells transferred from the transmitting node 10 to the working path 33, the protection path, and the shorter path of the cells transferred to the protection path 34 will be
It arrives at the receiving side node 20 first. In order for these cells to arrive at the receiving node 20 at the same time, it is necessary to transfer the cells with a delay on the shorter path that arrives at the receiving node 20 first.

Therefore, in the present invention, the difference in propagation delay between the working path 33 and the protection path 34 is measured in advance, and at the path switching time, a number of delay compensation cells corresponding to the difference in propagation delay are propagated. Insert/insert into the path with the shorter time.

■A switching cell is a cell that is used as a reference when a switch actually performs path switching.

Specifically, in the transmitting side node 10, the switching cell is inserted after the difference in propagation delay between the working path 33 and the protection path 34 is compensated for by the delay compensation cell, so in the receiving side node 20, the switching cell is inserted. arrives at the same time from both paths. Therefore, the receiving side node 20 can switch from the working path 33 to the protection path 34 at the time of receiving the switching cell.

■ By introducing time stamps, the current path 33
The propagation time of cells flowing through the backup path 34 can be measured, and can be used as information for propagation delay compensation during path switching. In addition to this, time information 30
By using this, it is possible to compensate for the difference in the switching times of the switches at both ends of the nozzle, which is a problem with the conventional system.

Specifically, since the control node 1 and the nodes 10 and 20 on the sending and receiving sides have the time information 30, the nodes at both ends of the path can drive Sui-Sochi at the same time. .

- By introducing a self-routing switch, it is possible to shorten the time required for switching processing, which is one of the problems with conventional methods. In addition, in the conventional STM-5W, since the switch has a matrix-socket structure, it was difficult to transfer information to the working path 33 and the backup path 34 in parallel, but in the case of a self-routing switch, the routing switch - Parallel transfer of information can be easily and quickly achieved by rewriting pulls.

■Introducing delay compensation cells will improve the propagation time of the working path 33 and protection path 34, which is the problem with the conventional method.
It is possible to compensate for opening the lid. That is, the transmitting side node 10 can transmit the switching cell by compensating for the delay time between the working path 33 and the protection path 34 in advance using the delay compensation cell, and the receiving side node 20 can transmit the switching cell at the same time. can be received.

■By inserting a switching cell, the receiving node 20
In this case, only the arrival of the switching cell needs to be taken into account, and the timing of path switching does not depend on the path capacity. Therefore, it is possible to realize easier path switching than the conventional method.

FIG. 3 shows the switching flow of the uninterrupted path switching method.

When a control node performs path switching, it transfers information containing the time at which path switching is to be performed to the monitoring drive device in the sending and receiving nodes. The monitoring drive devices at both ends that have received this information store the path switching time, and after a certain amount of time has elapsed, measure the propagation time difference between the working path and the backup path. The result is transmitted from the receiving side monitoring and driving device to the sending side monitoring and driving device via the control node, and the sending side monitoring and driving device stores the value. After performing the above processing, the monitoring drive devices at both ends wait until the path switching time, and at the path switching time, rewrite the routing chip to flow information in parallel to the backup path. At this time, the transmitting node inserts a number of delay compensation cells corresponding to the pre-measured propagation time difference into the path with the shorter propagation time, and a switching cell immediately after that, and then transfers the information. On the other hand, only the switching cell is inserted into the path with the longer propagation time before information is transferred. Therefore, the switched cells arrive at the receiving Q-node at the same time.

At the receiving side node, when the path switching time comes, it waits for the arrival of the switching cell, and when this cell arrives, it rewrites the routing chain and switches from the working path to the protection path. Since the switching cells arrive at the same time and ATM-3W operates at high speed, switching can be performed without interruption.

Next, the operation of the present invention will be explained in order by dividing it into three steps. FIG. 4 is an explanatory diagram showing path switching instructions (step 1), and FIG. 5 is an explanatory diagram showing the path switching instruction (step 1), and FIG.
), and FIG. 6 is an explanatory diagram showing path switching (step 3).

First, the prerequisites required for this method are shown below.

■The target network is control node 1, sending node 10,
It consists of a receiving side node 20.

(2) The control node 1 centrally manages the state of the wire mesh body and gives instructions to the sending side monitoring drive device 11 and the receiving side monitoring drive device 21 at the time of path switching.

(2) The transmitting side ATM-3W42 and the receiving side ATM-3W43 are self-routing switches, and cell routing is easily and quickly performed by rewriting the routing chip.

■Control node 1, sending node 10, receiving node 20
has time information 30.

Next, symbols necessary for explaining the operation of the invention will be explained.

- The time when the TO2 control node 1 instructs each monitoring drive device 11 and 21 to switch paths.

- Time when the propagation delay of the Tll second layer path 33 and protection path 34 started to be measured.

- T2: Time at which path switching is actually performed.

- tl: Time during which information instructing path switching propagates between the control node 1 and the monitoring and driving device 11 on the sending side.

- t2: Time during which information instructing path switching propagates between the control node 1 and the monitoring and driving device 21 on the receiving side.

τ: Time to propagate through the cell working path 33.

- Δτ: Propagation delay between the working path 33 and protection path 34. Therefore, the time for the cell to propagate along the protection path 34 is τ±Δ
becomes τ.

The switching procedure of the present invention is shown below.

(1) Step 1: Path switching instruction In step 1, control node 1 is connected to each monitoring drive device 11.
, 2L will be explained about the operation of giving a path switching instruction (4th
(see figure).

- The control node 1 instructs each monitoring drive device 1121 about the path switching time (T2). Information instructing this switching is written into the cell 32 and transferred. Further, the time information 3o held by the control node 1 is referred to for the switching time at this time.

- It is assumed that the time from when the control node 1 instructs switching to when the switching is actually performed (T2-TO) is sufficiently larger than the propagation delay (ltl-t21) of the switching instruction information. (2) Step 2: In the propagation delay measurement and notification step 2, a method of measuring the propagation delay between the working path 33 and the protection path 34 and a method of notifying the result will be explained (see FIG. 5).

- When the sending node 10 is instructed to switch by the control node 1, it confirms that the backup path 34 is available.

- If the protection path 34 is available, start transmitting cells 61 to the protection path 34 in parallel.

- At this time, the transmitting node 10 inserts a cell (propagation delay measurement cell 63) having information about the propagation delay measurement start time (T1) into the working path 33 and the protection path 34. (Time (TI-TO) is the propagation delay of switching instruction information (
tl−t21). ) - When receiving the switching instruction from the control node 1, the receiving node 20 waits for the arrival of the propagation delay measurement cell 63 transmitted from the working path 33 and protection path 34.

- When the propagation delay measurement cell 63 arrives from both the working path 33 and protection path 34, the propagation delay (Δτ) between the two is calculated from the difference in arrival time.

- The receiving side node 20 transmits the propagation delay information to the cell 64.
The sender node 20 is notified via the write control node 1.

(3) Step 3: Path switching In step 3, the path switching operation will be explained (see FIG. 6).

- The transmitting side node 10 that received the propagation delay information 62,
When the path switching time (T2) comes, the switching operation starts.

・The transmitting node 10 uses the path with shorter propagation time (9th
In the illustrated example, a number of delay compensation cells 66 corresponding to the propagation delay (Δτ) are successively inserted into the backup path 34), and a switching cell 65 is inserted immediately after that. After that, cell 61 is transferred.

・The transmitting node 10 uses the path with the longer propagation time (the 6th
In the illustrated example, a switching cell 65 is inserted into the working path 33). After that, cell 61 is transferred. By doing this, the switched cells 65 arrive at the receiving side node 20 at the same time.

- The receiving side node 20 waits for the arrival of the switching cell 65 at the path switching time (T2).

- When the switching cell 65 from the working path 33 arrives, subsequent cells 61 are not received.

- When the switching cell 65 from the protection path 34 arrives, it starts receiving subsequent cells 61.

〔Effect of the invention〕

As described above, according to the present invention, in future ATM networks, path switching can be performed without momentary interruption.
This has the effect of improving the reliability of the network from the user's perspective, since it does not affect the user side and also simplifies the operations within the network.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an uninterrupted path switching system according to an embodiment of the present invention, and FIG. 2 is a principle diagram of a self-routing switch used in the uninterrupted path switching system of FIG. 1. 3 is a diagram showing the switching flow of the uninterrupted path switching method in FIG. 1, FIG. 4 is an explanatory diagram showing path switching instructions, FIG. 5 is an explanatory diagram showing propagation delay measurement and notification, and Figure 7 is an explanatory diagram showing path switching, Figure 7 is a configuration diagram of a path switching method in a conventional STM network, Figure 8 is an internal configuration diagram of a switch used in conventional STM, and Figure 9 is a diagram of a conventional STM network.
FIG. 3 is a diagram showing a switching flow of a path switching method in a network. DESCRIPTION OF SYMBOLS 1... Control node, 10... Sending side node, 11.21... Monitoring drive device, 20=... Receiving side node, 33... Working path, 34... Protection path, 42... - Sending side ATM switch, 43... Receiving side ATM switch, 44... Self-routing switch.

Claims (1)

[Claims] An uninterrupted path switching method for switching paths in an ATM network, in which the sending and receiving nodes are provided with self-routing switch and time stamp functions, and the difference in propagation time delay between the two nodes is compensated for. A delay compensation cell and a switching cell that serves as a reference for path switching are provided to compensate for the timing difference in path switching and the difference in the propagation time of cells flowing on the working path and protection path, which affects the information transferred on the path. An uninterrupted path switching method that is characterized by switching paths without causing any interruptions.