JP2001339370A - Transmission channel redundant switch system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission channel redundant switch system that can avoid momentary interruption at execution of switch-back processing in the 1:N type transmission channel switch system and attain long time operation of Extra Traffic in a standby transmission channel. SOLUTION: The transmission channel redundant switch system of this invention is characterized in that the switch system does not fixedly reserve a standby system on the occurrence of a fault, but dynamically decides a transmission channel used for the standby system on the basis of 'quality of transmission channel' and 'priority of transmission channel' at that point of time when the fault takes place and is recovered, updates the priority of transmission channels on the basis of the priority of channels accommodated in each transmission channel and can revise the correspondence between a physical transmission channel and a channel number used for the transmission channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line redundancy switching system for switching a failed transmission line to a standby transmission line in a signal transmission system.

[0002]

2. Description of the Related Art For details of a transmission path switching method, refer to a document (Bellcore
Since it is described in detail in GR-253-CORE Issue 2, ITU-T G.783), the description is omitted below, but the outline of the conventional transmission line switching method is as follows.

[0003] The conventional transmission line switching system performs communication between devices using a control signal defined as an APS byte in the above document. When a failure occurs in the transmission line, the channel is switched to the backup transmission line while synchronizing the control state with the partner device using the APS byte.

[0004] Consider a system as shown in FIG. 2 for realizing a standby switching system of a transmission apparatus. The system is 1:
N (particularly 1: 2 in FIG. 2) switching system (this system configuration is described in detail in Bellcore GR-253-CORE Issue 2 and ITU-T G.783). The own station and the opposite station are connected by a total of (N + 1) transmission lines, and one of them is used as a standby system. The N transmission paths are usually used for communication. When a failure occurs in these transmission paths, the communication line is relieved by diverting the signal to the standby system (see FIG. 3).

[0005]

As described above, when one transmission line is shared by a plurality of transmission lines, the use of the standby transmission line must be stopped and released at the time of recovery from a transmission line failure. This operation is called a switchback process. This is to make it possible to use the spare transmission line when a failure occurs in another transmission line. However, in such a system, there is a possibility that an instantaneous interruption may occur in a line using the transmission line during the switchback processing. This instantaneous interruption depends on the switching method, and can be regarded as an unnecessary line interruption from the viewpoint of the line user. It is unlikely that a very short interruption will have a significant effect on the services provided by the line, but the network should minimize the effect on the line.

On the other hand, Bellcore GR-253-CORE Issue 2, IT
As a rule of UT G.783, even in the 1: N switching method, there is described a method called a non-revertive type that does not actively perform a revertive process after a failure recovery. However, in this non-revertive transmission line switching, Extra T which is a feature of 1: N switching is used.
There is a problem that the operation of raffic cannot be performed. That is, since the operation of Extra Traffic is not restarted until the switchback processing is completed, the time during which the service cannot be provided becomes longer. Here, Extra Traffic is to provide a spare transmission path as a communication path in a state without any trouble, and is useful from the viewpoint of effective use of network resources.

[0007]

According to the transmission line redundancy switching system of the present invention, a standby system at the time of occurrence of a failure is not fixedly secured, but at the time of occurrence and recovery of the failure, the "quality of the transmission line" at that time is determined. ) And "Priority of transmission line" to dynamically determine the transmission line to be used as the standby system, and to determine the priority of the transmission line based on the priority of the line accommodated in each transmission line. Updating and using physical transmission lines and transmission lines
Transmission path switching is characterized in that the correspondence of Channel numbers can be changed.

The advantages of the present invention are the following two points. 1. Avoid instantaneous interruptions that occur in the switching back process in the conventional transmission line switching method. 2. Enable long-term operation of Extra Traffic on the backup transmission line. The 1 “shutdown due to switchback” is a restriction in actual operation. For example, in the conventional switching system, a switch-back operation is performed at midnight on a holiday in order to prevent a service from being affected in a public network. According to the present invention, transmission path control can be performed at the convenience of the operator. Regarding item 2, by changing the name of the transmission path when the switching factor disappears, it is possible to avoid "the state in which the switching factor has disappeared but the switching is continued", which was in the conventional method. In addition, "The switching factor has disappeared,
In the state where switching is continued,
You cannot pass through Extra Traffic.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS §1. First Embodiment The following describes an example of a switching method in which the switching to the non-switching state is performed by changing the channel number of each transmission path without performing the switching process under the control of the bridge circuit and the switch circuit as the process at the time of failure recovery.

(1) Configuration of Embodiment 1 FIG. 1 is a functional block diagram of an apparatus constituting this system. The transmitted signal includes a main signal containing a user signal and a control signal for monitoring and managing the network. In the example of Fig. 1, two Working Lines and one Prot
Section Line is prepared. A signal received from the outside is first taken into the device via the 2to1 switch (1). Two
to1 switch (1) is Working Line 1 or Working Line respectively
Line 2 and Protection Line, and are connected to the working line or the protection line according to the instruction from the control signal processing unit (5).
ction Line is selected and passed to the main signal / control signal separation unit (2). The main signal / control signal separation unit (2) separates an external signal into a main signal and a control signal.

In the SDH device, a control signal is called an overhead, and an area used particularly for switching the standby system is called an APS byte. The APS byte is composed of the K1 byte and the K2 byte, and the contents are as follows. K1 bit 1-4 = Switching request K1 bit 5-8 = Channel number issuing switching request K2 bit 1-4 = Channe connected to Protection Line
l number (K2 bits 6-8 and later are omitted because they are not directly related to the present invention).

The reception control signal selector (3) has a function of selecting one of the control signals extracted from each transmission line. The transmission path information management setting unit (4) will be described later.

The control signal processing unit (5) receives the control request from the reception control signal selection unit (3), and receives the current state of its own device (in particular, the 1to2 bridge (7), the 2to1 switch (1), the transmission Control signal (APS byte) to hold and transmit
Is determined, and when the received APS byte changes or a switching request is issued by the administrator, the state of the own device is updated.
At the same time, it controls the 1to2 bridge (7) and the 2to1 switch (1).

A main signal / control signal synthesizing section (6) synthesizes a main signal to be transmitted and a control signal. The 1to2 bridge (7) controls the protection line and workin by the control from the control signal processing unit (5).
It has a function to split the signal into g Line.

The control signal processing unit (5) performs the following processing based on the control information notified from the transmission / reception control signal comparison unit (4). Control of 2to1 switch (1) Update of control signal output to main signal / control signal synthesis unit (6) Control of 1to2 bridge (7)

The control signal processing unit (5) is a reception control signal selection unit.
(3) When newer control information is received, the state of its own station (transmission control signal, state of 1to2 bridge (7), state of 2to1 switch (1)) is updated.

(2) Operation of the First Embodiment Consider a system as shown in FIG. 2 for realizing the standby switching system of the transmission apparatus. This system is called a 1: N (particularly 1: 2 in FIG. 2) switching system.

Transmission line information Transmission line information set in the transmission line information management setting section (4) is shown below. Each transmission path is managed by two identifiers, a transmission path number and Channel information. The transmission path number indicates a physical transmission path of the transmission device. Specifically, a physical medium such as an optical fiber corresponds to this. Channel
The information represents a function that a physical transmission path performs in a network. Specifically, it has the following information. 1. Working system (indicated as "Working" in FIG. 2) or standby system (indicated as "Protection" in FIG. 2) 2. Identifier between active transmission lines (in FIG. 2, "Working-"
1 ")

Normal State FIGS. 2, 3, and 4 show examples of a state in which no switching has occurred on the network (normal state). In FIG. 2, transmission line 0 is a Protection Channel, transmission line 1 is a Working-1 Channel, and transmission line 2 is a Working-2 Ch.
It is set and operated as annel. In FIG. 3, transmission line 0 is Working-1 Channel and transmission line 1 is Pro.
The transmission path 2 is set and operated as a Working-2 Channel as a tectionChannel. In FIG. 4, the transmission path
0 is Working-1 Channel, Transmission line 1 is Working-2 Cha
As the nnel, the transmission path 2 is set and operated as a protection channel.

Operation When Failure Occurs (1) FIG. 5 shows an operation when a failure (such as an optical fiber break) occurs in the transmission line 1. After the switching, the network using the transmission line 1 is (temporarily) bypassed to the transmission line 0 in terms of the network. The setting information at this time is as follows. Transmission line 0 is Protection Channel Transmission line 1 is Working-1 Channel Transmission line 2 is Working-2 Channel

Failure Recovery (1) FIG. 3 shows an operation when a failure in the transmission line 1 (such as an optical fiber break) is recovered. After recovery from the failure, the failure detection node notifies the opposite station of the failure recovery. After that, the transmission path information is reset as follows. Transmission line 0 is Working-1 Channel Transmission line 1 is Protection Channel Transmission line 2 is Working-2 Channel At the same time, transmission of the main signal to the transmission line before switching is stopped.

Operation When Failure Occurs (2) FIG. 6 shows a case where a failure has occurred in the transmission line 2 following FIG. At this time, a line using the transmission path 1 is (temporarily) bypassed to the transmission path 1 in terms of a network. The setting information is as follows. Transmission line 0 is Working-1 Channel Transmission line 1 is Protection Channel Transmission line 2 is Working-2 Channel

Failure Recovery (2) FIG. 4 shows the operation when the failure of the transmission line 2 is recovered.
After recovery from the failure, the failure detection node notifies the opposite station of the failure recovery. After that, the transmission path information is reset as follows. Transmission path 0 is Working-1 Channel Transmission path 1 is Working-2 Channel Transmission path 2 is Protection Channel Simultaneously, transmission of the main signal to the transmission path before switching is stopped.

§2. Second Embodiment In the first embodiment, the transmission line information is updated at the time of recovery from a failure. In the second embodiment, the update is performed when the switching is completed. -The priority of the line is set to the following two levels. Normal / Extra (Normal has the highest priority)-The quality of the transmission path is classified into the following three levels. No failure Severe failure (optical fiber disconnection, etc.): Hereinafter referred to as SF failure. Minor failure (Bit error, etc.): Hereinafter referred to as SD failure.

The decision to execute switching when a failure occurs is as follows. The determination of the execution of the switching is the same as that of the first embodiment.

Operation example (1) When an SF fault occurs on the Normal line → The transmission line operating the Extra line is determined to be the standby system, and switching processing is performed. After the switching process, the Extra line uses the faulty transmission line. Recovery of SF failure following the above → Update the transmission path information based on the state at that time (the transmission path accommodating the extra line is used as the standby system)

Operation example (2) When an SD fault occurs on the Normal line → The transmission line operating the Extra line is determined to be the standby system, and switching processing is performed. After the switching process, the Extra line uses the faulty transmission line. Following the above, an SF failure has occurred in another Normal line → the Normal line currently being switched due to the SD failure is exchanged with the transmission line accommodating the Normal line in which the SF failure has occurred.

§3. The embodiments of the present invention have been described above in detail with reference to the drawings. Even this is included in the present invention.

[0029]

The first effect is that an instantaneous interruption at the time of executing the switchback processing can be avoided in the 1: N transmission line switching system. The reason is that the switchback processing, which was conventionally realized by controlling the bridge circuit and the switch circuit, is realized as a change in the setting information of the transmission line. As a second effect, there is a case where the Extra Traffic can be operated while realizing the first effect. The reason is that the transmission of the main signal to the transmission line before switching is stopped at the same time as the transmission line information is updated.
ction Channel) is not used in any of the Working Channels. A third effect is that a more flexible switching method can be realized. The reason is that the number of spare transmission lines and the number of transmission lines to be used can be made variable by setting, so the five transmission lines are not limited to 1: 4 protection, but 2: 3 Protection (two transmission lines for three transmission lines). This is because it is easy to realize a method of securing a transmission path).

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a transmission device according to the present invention.

FIG. 2 is an explanatory diagram showing an example (normal state) of the state of the transmission system according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a state of the transmission system according to the present invention (failure recovery of transmission line 1 → normal state).

FIG. 4 is an explanatory diagram showing an example of the state of the transmission system according to the present invention (failure recovery of transmission line 2 → normal state).

FIG. 5 is an explanatory diagram showing an example of a state of the transmission system according to the present invention (a failure occurrence state in the transmission line 1).

FIG. 6 is an explanatory diagram showing an example of a state of the transmission system according to the present invention (a failure occurrence state in the transmission line 2).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 2 to 1 switch 2 ... Main signal / control signal separation part 3 ... Reception control signal selection part 4 ... Transmission path information management setting part 5 ... Control signal processing part 6 ... Main signal / control signal synthesis part 7 …… 1 to 2 bridge

Claims (4)

[Claims] 1. A transmission line redundancy switching method wherein a plurality of backup transmission lines are shared by a plurality of transmission lines. 2. The transmission line redundancy switching method according to claim 1, wherein the switching to the backup transmission line is dynamically determined according to the priority set for each transmission line. 3. The transmission line redundancy switching method according to claim 2, wherein after the recovery from the failure, transmission line information indicating the correspondence between the physical numbers and the function numbers of the transmission line and the backup transmission line is updated. . 4. The transmission line redundancy switching system according to claim 2, wherein after the switching process, transmission line information indicating a correspondence between a physical number and a function number of said transmission line and said backup transmission line is updated. .