JP2003069521A - Device, system and method for path switching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform path switching control, even if the number of lightwave paths or the number of transmission paths which take in upward and downward traffics have asymmetric network constructions, by controlling path switching for upward and downward independently. SOLUTION: The switching device 1 is comprised of the pair information retention part 14 which stores the pair information, for upward and downward individually, indicating an active and standby path, and the routing information retention part 12 which stores the routing information, for upward and downward individually, indicating an input and output path. When a switching request is on, the device sends switching controlling information such as the highest priority switching request, bridge selection position and selector selection position to a facing switching device, and controls switching the selector and the bridge according to the highest priority switching request for upward and downward individually, so that independent controlling path switching for upward and downward is available.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an STM (Synchron
ous Transfer Mode) and ATM (Asynchronous Transfer)
Path in electrical layer such as Mode, WDM (Wav
The present invention relates to a path switching device, a path switching system, and a path switching method applied to switching a lightwave path in an optical layer of elength division multiplexing.

[0002]

2. Description of the Related Art In recent years, with the rapid increase in demand for IP traffic, it is required to increase the capacity of backbone networks, but fiber installation costs are extremely high in network construction. Therefore, by accommodating a plurality of lightwave paths having different wavelengths in one fiber and accommodating the electric layer paths of the conventional STM, ATM, etc. in each of these lightwave paths, the transmission capacity per fiber is dramatically increased. W
DM technology has been attracting attention from the viewpoint of inexpensive transport network construction.

The following items are listed as merits of the WDM technology. 1. The transmission capacity per fiber can be inexpensively increased. 2. By passing through the lightwave path that does not terminate at the node in the optical layer without optical / electrical / optical conversion, it is possible to reduce the amount of electrical switch processing required at the node. 3. Since the path protocol to be accommodated for the lightwave path can be protocol-free, a wide variety of traffic can be centrally accommodated.

In this patent specification, STM and ATM are used.
The path of the electrical layer such as is simply defined as “path”, and the path for performing demultiplexing and path control in the optical layer by utilizing the physical wavelength difference is defined as “lightwave path”.

The ATM is composed of a 5-byte cell header containing control information such as a destination and a 48-byte user information.
It is a connection-type communication method based on the transfer of fixed-length cells of 3 bytes, and performs routing in units of virtual path (Virtual Path; hereinafter referred to as VP) and virtual channels (Virtual Channel; hereinafter referred to as VC). . In the switching device, a VP identifier (hereinafter referred to as VPI) or VC assigned to the transmission path is also used.
ATM cells are switched based on an identifier (hereinafter referred to as VCI).

Therefore, the ATM has the following merits. 1. It has a statistical multiple effect due to cell-based multiplexing. 2. A path capacity of an arbitrary speed can be set for each VP, and various services can be centrally and efficiently accommodated. 3. Since bandwidth control can be performed on a VP basis, QoS: Qualit
You can easily guarantee y of service.

Next, a 1: 1 switching path switching method will be described. The 1: 1 switching path switching method means that by implementing a switching protocol, communication is normally performed only through the working path, and when the working path fails, the sending side device and the receiving side device switch to the backup path. Is a path switching method in which communication is performed via a backup path. One of the merits of the 1: 1 switching path switching method is that it can accommodate low-priority class traffic (extra traffic) through a backup path that does not normally communicate, and is excellent in path accommodation efficiency.

Next, a conventional 1: 1 switching path switching method will be described. Note that the method for switching the lightwave path in the optical layer is not currently recommended, so AT
Description will be made using 1: 1 standard VP switching in the M layer.

FIG. 14 is an example of a VP configuration in the conventional VP switching, and FIG. 15 is an example of a normal path setting in FIG.
16 is an example of path switching at the time of failure of the working VP in FIG. 14, FIG. 17 is a switching control flow in conventional 1: 1 standard VP switching, and FIG. 18 is a cell of an APS cell in conventional 1: 1 standard VP switching. The format, FIG. 19, is a diagram showing the pair information holding unit of the working VP and the spare VP in the conventional VP switching, respectively.

As shown in FIG. 14, switching devices 100A, 10A
Between 0B, the same VP is configured for both up and down.
One of the transmission paths indicated by the transmission path number 11 accommodates a working VP assigned with a VP identifier Ba for transmitting high priority class traffic, and the other transmission path indicated by the transmission path number 12 , As a VP to which the VP identifier Bb is given, a backup VP of a high priority class or a V of a low priority class.
P (also referred to as an extra VP, which is a VP for accommodating extra traffic that performs communication using the free band of the spare VP that is not normally used) is accommodated. Note that it is also possible to realize by giving different VP identifiers to the backup VP of the high priority class and the VP of the low priority class.

As shown in FIG. 15, a switching device 100A is usually used.
Output side of the routing information holding unit, that is, the switching device 1
In the setting on the 00B side, the transmission line number 11 and the VP identifier Ba form a set, and the transmission line number 12 and the VP identifier Bb form a set. On the other hand, in the setting on the input side, the transmission line number 01 and the VP identifier Aa form a set, and the transmission line number 02 and the VP identifier Ab form a set. Then, of these four groups, the former group and the latter group are associated with each other.

Further, in the setting on the input side of the routing information holding unit of the switching device 100B, that is, the switching device 100A side, the transmission line number 11 and the VP identifier Ba are paired, and the transmission line number 12 and the VP identifier are set. Bb is a group. On the other hand, in the setting on the output side, the transmission line number 2
1 and the VP identifier Ca form a pair, and the transmission line number 22
And VP identifier Cb form a set. Then, of these four groups, the former group and the latter group are associated with each other.

Therefore, normally, the working VP of the high priority class, which is the VP assigned with the VP identifier Ba, and the extra VP, which is the VP assigned with the VP identifier Bb, are connected, while the backup VP of the high priority class is connected. Is disconnected.

Further, as shown in FIG. 19, the switching device 100
The pair information holding unit of A and 100B has, for example, a working VP.
To associate the backup VP with the transmission line number 11 and V
Set of P identifier Ba, transmission line number 12 and VP identifier B
The sets of b are associated with each other to form pair information, and such set values are commonly used for upstream and downstream.

This is because the following advantages can be obtained in implementing VP switching. 1. Reducing the number of held data in the pair information table 2. 2. Speed up pair information search processing by reducing the number of data. Speeding up processing by reducing the number of VRT data rewrites

Here, as shown in FIG. 16, when the working VP assigned with the VP identifier Ba fails, the switching device 10
0A refers to the pair information holding unit, and in the setting of the routing information holding unit, associates the set of VP identifiers Bb with the set of VP identifiers Aa, and releases the association with the set of VP identifiers Ab. .

Similarly, in the setting of the routing information holding unit, the switching device 100B has a set of the VP identifier Bb and the V
The pairs of P identifiers Ca are associated with each other, and the VP identifiers Cb
Cancel the association for the pair.

As a result, when the working VP fails, the extra VP is disconnected and the VP of the high priority class is switched from the working VP to the backup VP. At this time, in the Extra VP, an AIS (Alarm Indication) indicating a failure has occurred.
Sigunal) The cell is transmitted to the VP terminating device on the downstream side to notify the failure.

The processing in the switching device in the conventional 1: 1 standard VP switching will be described.

In this type of switching device, the electric circuit for switching the path is called a "switch section", of which the portion for switching the path transmitting section is a "bridge" and the portion for switching the path receiving section. The part to do is called a "selector".

In the 1: 1 standard VP switching, the switching request with the highest priority is selected in each switching device,
APS (Automatic Protect) for switching control as shown in FIG.
IonSwitching) Write to cell and reserve VP at regular intervals
Via the switch to the opposite switching device. When a failure occurs in the working VP, the signal disconnection of the working VP is detected and this AIS cell is transmitted to the downstream device.

In the APS cell, 0101 is written in the area of OAM Type as the type of the switching control cell when indicating the switching control cell. V in the Function Type area
0000 when switching in units of P groups, individual V
When switching is performed in P units, 0001 is written. Switching control is performed via the K1 byte and K2 byte of this cell. A switching request with the highest priority is written to the bridge and selector in the switching device in the 1 to 4 bit area of the K1 byte, and the system to which the switching request is applied is written in the 5 to 8 bit area. Further, the current selection positions of the selector and the bridge are written in an area of 1 to 4 bits of the K2 byte, and 0000 is selected when the selector and the bridge select the backup VP, and 0001 when the working VP is selected. Write. The area of 5 to 8 bits of the K2 byte is currently defined as unused.

As shown in FIG. 17, in the switching device 100A,
Switching request R10 common to the bridge / selector in the device
From "1", "signal disconnection of working VP" is selected as the switching request R102 having the highest priority (S101). Then, the switching device 100A switches to the opposite switching device 1 by K1.
The switching request R103 for disconnecting the signal of the working VP is transmitted via the byte.

Further, the switching device 100A is the switching device 10
It is confirmed that there is no code error in the switching request received from 0B, and that the switching request with the highest priority of the switching device 100B is normal for both systems and that the selector and bridge selection position is the working VP (S102). .

Further, the switching device 100A compares the "switching signal of the working VP" determined as the switching request R102 having the highest priority in S101 with the switching request R105 for both systems which has been read in S102 and gives a higher priority. A switching request R107 is issued for the “high-priority switching request“ signal disconnection of the working VP ”.
(S103).

The switching device 100A switches from the working VP to the backup VP by selecting the positions of the bridge and the selector in accordance with the switching request R107 selected in S103. In addition, on the opposite switching device 100B, a "spare V" as a selection position R107 of the selector and the bridge is provided.
P ”is included in the K2 byte of the APS cell and transmitted.

Further, the switching device 100A compares the selection position R106 common to the bridge and the selector of the switching device 100B read in S1022 with the switching request R107 selected in S103 to detect whether they match. (S104). Here, when a mismatch is detected several times in succession in S104, a mismatch warning is transmitted to the switching device 100B to perform the matching process. In addition, the switching device 100A
Even in the switching device 100B facing the switching device,
The same process as 0A is performed to switch the path from the working VP to the backup VP.

[0028]

As described above, in recent years, it has become possible to construct an inexpensive network by the technologies of STM, ATM and WDM. On the other hand, due to the recent increase in data transfer speed and capacity, it has become possible to transfer not only characters and images, but also large amounts of data such as applications and moving images, which reduces the amount of downstream traffic. It has increased. This is because, in services that provide large-volume data content such as applications and videos, the amount of data in the downlink direction is several hundred bytes compared to the amount of data in the direction of tens of bytes to several kilobytes that requires distribution of content. This is because it will be from kilobytes to hundreds of megabytes.

However, in a network to which the conventional path switching method is applied, the path must be accommodated in a transmission path set as a pair in advance. Even if there is a free band in the accommodating transmission path of the path, the redundant path cannot be accommodated any more. The problem that the path accommodation efficiency of the upstream path with a small traffic amount decreases due to the increase in the asymmetry of the traffic amount in the upstream direction and the downstream direction cannot be solved in the network to which the conventional path switching method is applied.

Further, when the conventional path switching method is applied to the switching of the lightwave paths and the traffic is not accommodated in the redundant lightwave path forming the pair, between the lightwave paths in the downstream direction in which the upstream traffic is accommodated in the same lightwave path. Failure information must be shared, which has a large impact on the switching method and causes a problem that the added function becomes too complicated.

In the conventional path switching method, the redundant upstream path and the downstream path must be accommodated in a transmission path set as a pair in advance, and when the bandwidth of the accommodation path of the downstream path is insufficient, the accommodation transmission of the upstream path is performed. Even if there is a free band on the road, it becomes impossible to accommodate more redundant paths. That is, for traffic in which the amounts of data in the upstream and the downlink are asymmetric, the conventional path switching method has a problem that the path accommodation efficiency is lowered in the transmission path accommodating the upstream path. Furthermore, this problem also occurs between urban areas where contents are concentrated and areas where users are concentrated in a large-scale network. Such a decrease in the path accommodation efficiency in a large-scale network is one of the causes of worsening the service provision cost, and improvement of the path accommodation efficiency in the upstream direction is required.

Similarly, in the path switching method of the lightwave path to which the conventional 1: 1 switching algorithm is applied, there is a problem that the path accommodation efficiency is lowered even for the lightwave path accommodating the upstream path. In order to solve this problem, the number of upstream lightwave paths is made smaller than the number of downstream lightwave paths, and the path accommodation efficiency in the upstream lightwave paths is improved by consolidating the traffic in the upstream direction. Problems arise.

FIG. 9 is a diagram showing a lightwave path configuration example for improving the path accommodation efficiency for the lightwave path in the upstream direction. FIG. 9 is an example of a path configuration in which the traffic volume is higher in the downlink than in the uplink, and the number of lightwave paths is 1 in the uplink and 3 in the downlink. In this case, the number of upstream lightwave paths can be aggregated into one with respect to the plurality of downstream lightwave paths, so that the path accommodation efficiency in the upstream lightwave paths is improved.

However, in the conventional path switching method, switching between the up and down directions is performed at the same time. Therefore, if a failure occurs in an arbitrary down light path (λ201), the up light path (λ101) is also spared. It is necessary to switch to the other lightwave paths (λ111), and as a result, the remaining two downstream lightwave paths (λ202, λ20) in which no failure has occurred
Also in 3), in order to match with the selected position of the upstream lightwave path, it is necessary to switch from the working to the protection. Therefore, in the conventional 1: 1 switching algorithm, failure occurrence information is shared between downlink lightwave paths accommodating upstream traffic in the same lightwave path, and switching is performed to a lightwave path without failure. Need to add functionality. However, this method is not realistic because it has a large impact on the switching method itself and is functionally too complicated.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to independently perform path switching control for upstream and downstream paths to thereby enable the upstream and downstream paths to be switched. It is an object of the present invention to provide a path switching device, a path switching system, and a path switching method capable of performing path switching control even in a network configuration in which the number of transmission paths accommodating traffic or the number of lightwave paths is asymmetric.

[0036]

In order to solve the above problems, the present invention according to claim 1 provides means for individually storing pair information indicating a working path and a protection path in an up direction and a down direction, and an input path. And a routing information indicating an output path for each of the upstream direction and the downstream direction, and when switching request, the switching request with the highest priority to the selector in the switching device, the selection position of the bridge and A path switching device that transmits the selection position of a selector as switching control information to an opposite switching device, and performs switching control between a selector and a bridge individually for upstream and downstream paths and according to a switching request with the highest priority. Will be the solution.

According to the present invention of claim 3, the switching device stores pair information indicating the working path and the protection path and routing information indicating the input path and the output path separately for the up direction and the down direction. A path switching method, in the case of a switching request, the switching request with the highest priority to the selector in the switching device, the bridge selection position and the selector selection position as the switching control information, transmitted to the opposite switching device, For each of the up and down paths,
The path switching method is characterized by performing switching control between the selector and the bridge in accordance with the switching request having the highest priority.

According to the first and third aspects of the present invention, when the switching request is made, the switching request having the highest priority to the selector in the switching device, the bridge selection position and the selector selection position are used as the switching control information. It transmits to the opposite switching device and performs switching control of the selector and the bridge individually for the upstream and downstream paths and according to the switching request with the highest priority, so switching control of the upstream and downstream paths is performed. Can be done independently, and as a result,
It is possible to switch paths even in a path configuration in which the number of transmission paths accommodating upstream and downstream paths is asymmetric.

Further, the present invention according to claim 2 is a switching device in which pair information indicating a working path and a protection path and routing information indicating an input path and an output path are individually stored in each of an up direction and a down direction. In the path switching system, one of the switching devices transmits a switching request with the highest priority to the selector in the switching device as switching control information to the opposite switching device and the opposite switching device. The device has a path switching system characterized by responding as normal or abnormal termination of bridge switching performed individually in the upstream direction and the downstream direction and a bridge selection position as switching control information.

Further, according to the present invention of claim 4, a switching device in which pair information indicating a working path and a protection path and routing information indicating an input path and an output path are individually stored in each of an up direction and a down direction. A path switching method performed between two switching devices, in which one switching device transmits a switching request with the highest priority to a selector in this switching device as switching control information to the opposite switching device, and the opposite switching device Therefore, the path switching method is characterized in that normal termination or abnormal termination of the bridge switching performed individually in the up direction and the down direction and the bridge selection position are returned as the switching control information.

According to the present invention of claims 2 and 4, one of the switching devices transmits the switching request having the highest priority to the selector in the switching device to the opposite switching device as the switching control information. , The opposite switching device responds with normal termination or abnormal termination of the bridge switching performed individually in the up direction and the down direction and the bridge selection position as the switching control information. Can be performed independently, and as a result, paths can be switched even in a path configuration in which the number of transmission paths accommodating upstream and downstream paths is asymmetric.

The present invention according to claim 5 is characterized in that switching control is performed in the electrical layer, switching is performed in the optical layer, and switching is performed using a lightwave path as a switching unit.
Alternatively, the path switching method described in 4 is used as a solution.

According to the present invention of claim 5, switching control of lightwave paths in the up and down directions can be independently performed.
As a result, lightwave path switching control can be performed even in a lightwave path configuration in which the number of lightwave paths accommodating upstream and downstream paths is asymmetric.

Further, according to the present invention of claim 6, the path to be switched is an ATM layer VP, the switching control information is included in an APS cell, and the pair information is a transmission path accommodating a working VP. Transmission line number and VP identifier, and backup V
The routing information is information including a transmission path number of a transmission path accommodating P and a VP identifier, and the routing information is an input VP.
Information including a transmission path number and a VP identifier of a transmission path accommodating the output VP, and a transmission path number and a VP identifier of the transmission path accommodating the output VP. The routing information is rewritten after the VP switching. The path switching method according to claim 3 or 4 is a solution.

According to the present invention of claim 6, switching control of the VPs in the up and down directions can be performed independently, and as a result, the number of transmission paths accommodating the VPs in the up and down directions is asymmetric. Even in the VP configuration example described above, the VP switching control can be performed.

Further, in the present invention of claim 7, the path to be switched is a VC of ATM layer, the switching control information is included in an APS cell, and the pair information is of a transmission line accommodating a working VP. Transmission line number, VP identifier and VC identifier, and transmission line number of transmission line accommodating backup VP, VP
The routing information is information including an identifier and a VC identifier, and the routing information includes a transmission line number of a transmission line accommodating an input VP, a VP identifier and a VC identifier, and a transmission line number of a transmission line accommodating an output VP, VP. It is information consisting of an identifier and a VC identifier, and the routing information is rewritten after the VP is switched.
The described path switching method will be the solution.

According to the present invention of claim 7, switching control of VCs in the up direction and the down direction can be independently performed, and as a result, the number of transmission paths accommodating the VCs in the up direction and the down direction is asymmetric. Even in the VC configuration example described above, the VC switching control can be performed.

Further, according to the present invention of claim 8, when a switching device is installed at both ends of each section of the ring network to accommodate a working path and a protection path, switching of both ends of a section in which a failure of the working path occurs. It is a path switching method performed by the device,
4. The switching destinations are folded back and connected to paths around opposite directions of adjacent sections.
The path switching method described in any one of 1 to 7 is a solution.

According to the present invention of claim 8, the section in which the failure in the working path has occurred in the ring network is switched by making a return connection to the path in the opposite direction, so that the section in which the working failure occurs can be avoided. It is possible to switch between failures.

[0050]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment: Example of Application to Device Implementing One-Phase Switching Protocol] In the first embodiment, only a switching request is transmitted as switching control information to an opposite switching device, and a response to the switching request is sent. This is an example of application to an STM or ATM transmission device that implements a one-phase switching protocol that does not perform the above.

FIG. 1 is a diagram showing the configuration of the switching device 1 according to the first embodiment. The switching device 1 includes a switch unit 11,
The routing information storage unit 12, the path switching control unit 13, the pair information storage unit 14, the input signal abnormality detection unit 15, and the host device IF unit 16 are provided. A plurality of transmission lines are connected to the respective input ports and output ports of the switch section 11 via a plurality of reception IF and transmission IF sections, respectively. The correspondence relationship between the input path and the output path is set in the routing information holding unit 12. Path switching control unit 13
By setting the routing information holding unit 12,
Switching control between the selector and the bridge is performed individually for the upstream and downstream paths and according to the switching request with the highest priority.

Pair information indicating the correspondence between the working path and the protection path is set in the pair information holding unit 14 and is referred to when the routing information holding unit 12 is set by the path switching control unit 13. The routing information holding unit 12 and the pair information holding unit 14 are configured such that information is set individually for the up direction and the down direction. The input signal abnormality detection unit 15 gives various switching requests to the path switching control unit 13 based on the failure information detected by each reception IF unit. The higher-level device IF section 16 gives a switching command input from the higher-level apparatus operated by the operator to the path switching control section 13 as a switching request.

2, FIG. 3 and FIG. 4 are respectively a path configuration example of the first embodiment, a path switching example when a working path fails,
It is a switching control flow chart. In the drawings attached to this specification, the working path is shown by a solid line and the backup path is shown by a dotted line. 2 and 3, the switching devices 1A and 1B have the configuration of the switching device 1, and the direction from the switching device 1A to the switching device 1B is "up" and the opposite direction is "down."

As shown in FIG. 2, between the switching devices 1A and 1B, the transmission lines assigned the transmission line numbers 11, 12, 13, and 14 (the former two are upstream transmission lines, the latter two are downstream transmission lines). Transmission line)
Is configured.

One of the upstream transmission paths, to which the transmission path number 11 is assigned, accommodates a working path assigned a path identifier Ba for transmitting high priority class traffic,
The other upstream transmission path to which the transmission path number 12 is assigned accommodates a backup path in the high priority class or a path in the low priority class as the path to which the path identifier Bb is assigned.

One of the downlink transmission lines, to which the transmission line number 13 is given, accommodates a working path to which the path identifier Bc is given for transmitting the traffic of the high priority class.
The other downlink transmission path assigned the transmission path number 14 accommodates a backup path of the high priority class or a path of the low priority class as the path assigned the path identifier Bd.

Further, as shown in FIG. 2, normally, on the upstream output side of the routing information holding unit 12 of the switching device 1A,
That is, in the setting on the switching device 1B side, the transmission line number 1
1 and the path identifier Ba form a pair, and the transmission line number 12
And the path identifier Bb form a set. On the other hand, in the setting on the upstream input side, the transmission line number 01 and the path identifier A
a is a pair, and the transmission line number 02 and the path identifier Ab are
Are in pairs. Of these four sets, the set of path identifiers Aa and the set of path identifiers Ba, the path identifier Ab
And the set of path identifiers Bb are associated with each other.

Further, in the setting on the upstream input side of the routing information holding unit 12 of the switching device 1B, that is, the switching device 1A side, the transmission line number 11 and the path identifier Ba are paired, and the transmission line number 12 and The path identifier Bb is a set. On the other hand, in the setting on the upstream output side, the transmission line number 21 and the path identifier Ca form a set, and the transmission line number 22 and the path identifier Cb form a set. Then, among these four sets, a set of path identifier Ba and a set of path identifier Ca are associated with each other, and a set of path identifier Bb and a set of path identifier Cb are associated with each other.

Further, as shown in FIG. 2, in the setting on the downstream output side of the routing information holding unit 12 of the switching device 1B, that is, the switching device 1A side, the transmission line number 13 and the path identifier Bc form a set. , And the transmission path number 14 and the path identifier Bd form a set. On the other hand, in the setting on the downlink input side, the transmission line number 23 and the path identifier Cc form a set, and the transmission line number 24 and the path identifier Cd form a set. Then, of these four sets, a set of path identifiers Bc and a set of path identifiers Cc are associated with each other, and a set of path identifiers Bd and a set of path identifiers Cd are associated with each other.

Further, in the setting on the downlink input side of the routing information holding unit 12 of the switching device 1A, that is, the switching device 1B side, the transmission line number 13 and the path identifier Bc are paired, and the transmission line number 14 and The path identifier Bd is a set. On the other hand, in the setting on the downlink output side, the transmission line number 03 and the path identifier Ac form a set, and the transmission line number 04 and the path identifier Ad form a set. Then, among these four sets, a set of path identifiers Ac and a set of path identifiers Bc are associated with each other, and a set of path identifiers Ad and a set of path identifiers Bd are associated with each other.

The paths assigned with the path identifier Ba and the path identifier Bc are set so as to be used normally, and are conventionally called "working paths". And
When the switching device 1A can use these paths, the bridge selection position of the switching device 1A (also referred to as a bridge position) is said to be "active", and similarly, the switching device 1B's The selection position of the selector (also referred to as the selector position) is said to be "active".

On the other hand, each of the paths to which the path identifier Bc and the path identifier Bd are given is set as a spare path that is not normally used, and is conventionally called a "spare path". When the switching device 1A can use this path, the bridge position of the switching device 1A and the selector position of the switching device 1B are said to be "spare".

Although not shown, the switching devices 1A, 1B
In each pair information holding unit 14, in the upstream direction of such an inter-apparatus section, a set of a transmission path number 11 and a path identifier Ba indicating the working path and a transmission path number 12 indicating the upstream protection path are shown. Pairs of path identifiers Bb are associated with each other to form pair information.

On the other hand, for the downlink of the section between the switching devices 1A and 1B, a set of the transmission path number 13 and the path identifier Bc indicating the downlink working path, and the transmission path number 14 and the path identifier indicating the downlink protection path. Pairs of Bd are associated with each other to form pair information.

The operation of path switching when the signal of the working path to which the path identifier Ba is added is cut off due to the failure of the upstream transmission path will be described below.

First, the contents of the information transmitted within the device or between the devices and their codes are shown. The "switching request" inside the switching device indicates the type of switching request, and includes identification information for identifying this type.

R1: switching request to selector R2: switching request having the highest priority to the selector R3: system for applying the switching request of R2 R4: selection position of selector R5: highest priority to opposing selector High switching request R6: System to which switching request of R5 is applied R7: Selection position of selector of opposing switching device R8: Selection position of bridge of opposing switching device R9: Switching request for bridge R10: Highest priority to bridge Higher switching request R11: System that applies the switching request of R10: Bridge and opposing selector, that is, system that applies the switching request of the switching request R13: R12 that has the highest priority to the transmission path R14: Selection of the bridge Position R15: Mismatch warning of the selected position of the bridge of the switching device facing the selector R16: With bridge Mismatch alarm selector selection position of the switching device for countercurrent

First, the operation of the switching device 1B will be described. When the transmission line (transmission line number 11) fails, the signal of the upstream working path (path identifier Ba) is cut off, and therefore the input signal abnormality detection unit 15 receives the detection result of this signal breakage as failure information. . Then, the input signal abnormality detection unit 15 gives the path switching control unit 13 a corresponding switching request R1 called “current signal disconnection”. In addition, to the path switching control unit 13,
"Current signal deterioration" or "both system normal (No Request)" provided by the input signal abnormality detection unit 15 or the host device IF unit 16
Since another type of switching request R1 such as a switching command from the server is also input, the path switching control unit 13 determines in step S11.
The (switching request comparing means) compares these input switching requests R1 with each other, and selects the switching request R2, which is the switching request having the highest priority, from the input signal abnormality detecting section 15 in this example. The working path signal disconnection is determined, and the system R3 to which this switching request is applied is determined as the "working system".

As the "system", the active system in which the main signal is transmitted or the standby system in which the main signal is not transmitted can be selected. The system R3 can be omitted when the switching control is performed by transmitting only the switching request to the opposite switching device. These are common to all the embodiments.

Next, in step S12 (selector switching means), the selection position of the selector is changed from "active" to "spare" according to the switching request R2 and the system R3 to which the switching request is applied.
Switch to. Specifically, the path switching control unit 13 refers to the pair information of the pair information holding unit 14, and in the routing information holding unit 12, associates the set of the path identifier Ca with the set of the path identifier Bb to obtain the path identifier. The association regarding the set of Ba is canceled. In a succeeding step S17 (means for transmitting the switching control information to the opposite device), the switching request R2
The "active signal disconnection", the system R3 "active system", the selector selection position R4 "spare", and the bridge selection position R14 are transmitted to the switching device 1A as switching control information. Here, the description will be continued assuming that R14 is “active”.

Next, the operation of the switching device 1A which receives the switching control information will be described. Note that R2, R3, R4, and R14 transmitted as the switching control information are the switching device 1A.
Are respectively recognized as R5, R6, R7, and R8.

First, the switching device 1A confirms that there is no code error in the switching control information in step S13 (a means for confirming and reading the validity of the switching control information), and at the same time, R5, R6, R7, Read R8.

Next, in step S18 (mismatch detecting means for the selector position and the bridge position of the opposite device), the selector selection position R4 of the switching device 1A itself does not match the bridge position R8 of the switching device 1B read in S13. It detects whether or not there is. N because R4 and R7 are both "working"
Although it is determined to be O, when YES (mismatch) is detected several times in succession, the mismatch alarm R15 is transmitted to the switching device 1B.

A switching request R9 for the bridge is input to the path switching control unit 13. Step S
In 14 (comparison means of switching request), the path switching control unit 13
Compares these switching requests and determines the switching request R10 which is the switching request with the highest priority among them. Here, R10 is "both systems normal (No Request)".

Next, in step S15 (switch request comparison means), the path switch control unit 13 switches the switch requests R10 and R.
5, the switching request R5, which is the switching request with the highest priority, is determined as the switching request R12 with the highest priority for the bridge and the opposing selector, and R
6 "active system" is the system R1 to which this switching request R12 is applied
Determined as 3.

Next, step S16 (bridge switching means)
Then, according to the switching request R12 and the system R13 to which this switching is applied, the bridge selection position is switched from "active" to "standby". Specifically, the path switching control unit 13
With reference to the pair information of the pair information holding unit 14, the routing information holding unit 12 associates the pair of path identifiers Bb and the pair of path identifiers Aa with each other and cancels the association of the pair of path identifiers Ab.

The selected position R14 of the bridge after switching
Is the switching control information in step S17 described above,
It is transmitted to the switching device 1B together with R2, 3, and 4.

At step S19 (mismatch detecting means for the bridge position and selector position of the opposite device), it is determined whether or not the selected position R14 of this bridge and the selector position R7 of the switching device 1B read at S13 do not match. To detect. Although both R14 and R7 are determined to be “active”, NO, but if YES (mismatch) is detected several times in succession, the mismatch alarm R16 is transmitted to the switching device 1B.

Therefore, as shown in FIG. 2, only the selectors and bridges of the upstream path where the signal is disconnected are switched from the working to the backup and the downstream path in which no failure has occurred by the processing of steps S11 to S19. The selector and bridge can be left active.

As shown in FIG. 5, S14 and S15 can be omitted in the switching control flow. In this case, R5 is used as the switching request R12, and the applicable system R1
As R3, R6 is unconditionally applied.

As described above, according to the first embodiment of the present invention, the switching request, the bridge selection position and the selector selection position having the highest priority are switched to the selector in the switching device. As information, it is transmitted to the opposite switching device, and for the up and down paths individually,
In addition, since switching control of the selector and bridge is performed according to the switching request with the highest priority, it is possible to perform switching control of the upstream and downstream paths independently, and as a result, the upstream and downstream paths are switched. Paths can be switched even in a path configuration in which the number of accommodated transmission paths is asymmetric.

[Second Embodiment: Example of Application to Device Implementing Two-Phase Switching Protocol] In the second embodiment,
The configuration of the switching device, the configuration of the paths, and the path switching at the time of the active failure are the same as those shown in FIGS. 1, 2 and 3, and the difference in the switching method will be mainly described.

FIG. 6 is a switching control flow chart of the second embodiment. Specifically, switching control of the selector position of the switching device 1B and switching control of the bridge position of the switching device 1A are shown. Below, in the second embodiment, the contents of the information transmitted within the device or between the devices and the symbols thereof will be shown. Note that these reference numerals and step numbers are shown as being different from those in the first embodiment.

R1: Switching request for selector R2: Switching request with highest priority for selector R3: System applying switching request of R2 R4: Switching request for bridge R5: Switching with highest priority for bridge Request R6: switching request having the highest priority with respect to the selector and bridge R7: normal termination or abnormal termination response to the switching request R8: bridge selection position R9: selector position R10: selector / bridge selection position mismatch alarm

First, the operation of the switching device 1B will be described. When the signal of the upstream working path (path identifier Ba) is cut off, the path switching control unit 1 gives a switching request R1 called "working signal cutoff"
Given to 3. The path switching control unit 13 is step S11.
The (switching request comparison means) compares the input switching requests R1 with each other, and selects the switching request R2, which is the switching request having the highest priority, from the input signal abnormality detection unit 15 as "signal disconnection of working path". , And the system R3 to which this switching request is applied is determined to be the "active system". Continued Step S12
(Means for transmitting the switching control information to the opposite device) transmits the switching request R2 "active signal disconnection" and the system R3 "active system" to the switching device 1A as the switching control information.

Next, the operation of the switching device 1A which has received the switching control information will be described. First, in step S13 (means for confirming and reading the validity of the switching control information), it is confirmed that there is no code error in the switching control information, and the switching request R2 "Signal disconnection of working path" and the system R3 to which this switching is applied. Read "active system". In step S14 (switching request comparison means), the switching requests R4 of the plurality of bridges that are input are compared, and the switching request R5 that is the switching request with the highest priority among them is, for example, “both systems normal (NoReques
t) ”. Next, in step S15 (switching request comparing means), the switching requests R2 and R5 are compared, and the switching request R5 “signal disconnection of working path”, which is the switching request with the highest priority, is sent to the bridge and the selector. The switching request R6 having the highest priority is determined. Next step S1
6 (bridge switching means) switches the selected position of the bridge from "active" to "standby" in response to the switching request R6. Specifically, the routing information holding unit 12 is rewritten as in the first embodiment. Next step S17
Then, based on the switching result in step S16, the switching device 1 uses the response R7 indicating the normal end or the abnormal end to the switching request and the bridge selection position R8 as the switching control information.
Send to B. Here, it is assumed that the response R7 is “normal end”.

Next, the operation of the switching device 1B which has received the switching control information will be described. In step S18 (a means for confirming and reading the validity of the switching control information), it is confirmed that there is no code error in the switching control information, and the response R7 and the bridge selection position R8 are read from this switching control information. Then, step S19 (selector switching means)
Then, according to the response R7 "normal end", the selection position of the selector is switched from "active" to "standby". Specifically, the routing information holding unit 12 is rewritten as in the first embodiment.

Then, in step S20 (a mismatch detecting means for the selector position and the bridge position of the opposite device), the selector selection position R9 and the switching device 1A read in step S18.
It is detected whether or not the bridge positions R8 of the two do not match.
Since both R9 and R8 are "active", it is determined to be NO. However, when YES (mismatch) is detected several times in a row,
The disagreement alarm R15 is transmitted to the switching device 1A.

Therefore, as shown in FIG. 2, only the selectors and bridges of the upstream path in which the signal is disconnected are switched from the working to the backup and the downstream path in which no failure has occurred by the processing of steps S11 to S20. The selector and bridge can be left active.

As described above, according to the second embodiment of the present invention, the pair information indicating the working path and the protection path and the routing information indicating the input path and the output path are transmitted in the upstream direction. In the path switching method performed between the switching devices individually stored for each of the downlink directions, a switching request with the highest priority and a system that applies this switching request from one switching device to the selector in this switching device are provided. The switching control information is transmitted to the opposite switching device, and the opposite switching device responds as normal or abnormal termination of bridge switching individually performed in the up direction and the down direction and the bridge selection position as the switching control information. So
Upward and downward path switching control can be performed independently, and as a result, path switching can be performed even in a path configuration in which the number of transmission paths accommodating upstream and downstream paths is asymmetric. it can.

[Third Embodiment: Example of Application to WDM Transmission Device] FIG. 8 is a diagram showing a configuration of a switching device 2 according to a third embodiment. Specifically, it is a diagram showing a configuration of a WDM switching device including an optical cross connect (hereinafter, referred to as an optical XC). Further, FIG. 9 is a diagram showing a lightwave path configuration example, and FIG. 10 is a diagram showing a lightwave path switching example.

The switching device 2 of the third embodiment is configured so that the path to be switched is a lightwave path, and switching control is performed by the electric layer and switching is performed by the optical layer. Further, the same components as those of the switching device 1 shown in FIG. 1 are designated by the same reference numerals, and different portions will be mainly described.

The switching device 2 is the switch unit 1 of the switching device 1.
Instead of 1, optical X that switches lightwave paths in the electrical layer
The optical XC unit 21 includes a C unit 21, and the optical XC unit 21 includes a path switching control unit 13
Is provided with a lightwave path switching control unit 211. Since the optical XC used for lightwave path switching control is a semi-fixed switching operation, the lightwave path switching control unit 211 not only rewrites the routing information holding unit 12 at the time of path switching, but also directly the optical XC unit 21. The switching control is performed for.

Further, in the switching device 2, the multiplexing / demultiplexing of the lightwave path, that is, the demultiplexing and the route in the optical layer are provided between the transmission IF section or the reception IF section and the transmission path (optical fiber). An optical demultiplexing unit 22 for controlling is provided. The pair information holding unit is not necessary if the working and protection pair information of the lightwave path is fixedly assigned in advance and the spare lightwave path to be paired can be specified without referring to the pair information holding unit.

The switching protocol is implemented by setting the path overhead of the electric layer path and the path for switching control,
Alternatively, it can be performed by setting the lightwave path overhead of the light layer or the lightwave path for switching control. The path switching control according to the third embodiment can be performed in the same manner as in the first or second embodiment.

In FIG. 9, the switching device 2A to the switching device 2B.
The number of lightwave paths in the up direction is 1 and the number of lightwave paths in the down direction from the switching device 2B to the switching device 2A is 3.

Transmission line number 1 is provided between the switching devices 2A and 2B.
A transmission line to which 1, 12, 13, and 14 are added (the former two are upstream transmission lines, the latter two are downstream transmission lines) is configured. The upstream transmission path (transmission path number 11) accommodates a working lightwave path (lightwave path identifier λ101) for transmitting high priority class traffic, and the upstream transmission path (transmission path number 12).
Is a backup lightwave path (lightwave path identifier λ
111) is accommodated. Downlink transmission line (transmission line number 13)
In order to transmit high priority class traffic, three working lightwave paths (lightwave path identifiers λ201, 202, 2
03), and the downlink transmission path (transmission path number 14) accommodates three backup light wave paths (light wave path identifiers λ211, 212, 213) of the high priority class.

As shown in FIG. 10, for example, when a failure occurs in the lightwave path (lightwave path identifier λ201),
Since the switching control of the first embodiment or the second embodiment is performed, the lightwave path (lightwave path identifier λ201) can be switched to the lightwave path (lightwave path identifier λ211). In this switching, the switching device 2A (2B)
Then, first, the lightwave path switching control unit 211 performs lightwave path switching control in the electrical layer, and then the optical XC unit 21 performs lightwave path switching in the optical layer.

Therefore, as shown in FIG. 10, only the selectors and bridges of the lightwave path in the direction in which the failure has occurred are switched from the working to the standby, and the selectors and bridges of the other lightwave paths in which no failure has occurred are the working ones. You can leave it selected.

As described above, according to the third embodiment of the present invention, switching control is performed in the electrical layer, switching is performed in the optical layer, and switching is performed using the lightwave path as a switching unit. The switching control of the lightwave paths in the up and down directions can be independently performed, and as a result, the lightwave path switching control can be performed even in the lightwave path configuration in which the number of lightwave paths accommodating the up and down paths is asymmetric. It can be performed.

[Fourth Embodiment: Application Example to ATM Transmission Device] In the fourth embodiment, the switching device 1 of FIG.
It is configured as a TM transmission device (also referred to as switching device 1 in this example). Therefore, the path to be switched is the VP (virtual path) of the ATM layer, and the switching control information described in the above embodiment is included in the APS cell. Also,
The pair information is a transmission line number and a VP identifier (VPI) of a transmission line accommodating the working VP.
And the transmission line number of the transmission line accommodating the spare VP and the VP
It is information consisting of an identifier. The routing information is information including a transmission line number and a VP identifier of a transmission line in which the current input VP is accommodated, and a transmission line number and a VP identifier of a transmission line in which the output VP is accommodated. And V
After P switching, the routing information is rewritten.

Specifically, as shown in FIG.
Since the VP of the layer is used as the switching unit, the switching device 1 (1
In the routing information holding unit 12 (VP routing table) of A, 1B), the VP identifier may be set instead of the path identifier. In addition, the pair information holding unit 14
Transmission line number 11 and VP identifier B indicating the upstream working VP
Transmission line number 12 and V indicating the pair a and the upstream backup VP
Pairs of P identifiers Bb are associated with each other to form pair information. Further, pair information is similarly set for the downlink. Since the routing information is rewritten, for example, the upstream working VP (VP
Even when a failure occurs in the identifier Ba), the downstream V
A failed VP is replaced with a spare VP without switching P
It is possible to switch to (VP identifier Bb).

When the VC (virtual channel) accommodated in the VP is switched as the path of the present invention, the VP identifier of the VP accommodating this VC is set to the VC of this VC.
It suffices to associate the identifiers. That is, the pair information is information including the transmission line number of the transmission line accommodating the working VP, the VP identifier and the VC identifier, and the transmission line number of the transmission line accommodating the backup VP, the VP identifier and the VC identifier. Good. The routing information includes a transmission line number of a transmission line accommodating the input VP, a VP identifier, and a VC identifier,
The information may be the transmission line number of the transmission line accommodating the output VP, the VP identifier, and the VC identifier. It is needless to say that the switching control information is included in the APS cell. After the VP switching, the function as the ATM transmission device can be exhibited by rewriting the routing information.

Therefore, according to the fourth embodiment of the present invention, the switching control of the VP and VC in the up and down directions can be independently performed, and as a result, the VP in the up and down directions can be accommodated. VP configuration example in which the number of transmission paths to be performed is asymmetric,
Alternatively, VP or VC switching control can be performed even in a VC configuration in which the number of VPs accommodating VCs is asymmetric.

[Fifth Embodiment: Application to Ring Network]
FIG. 12 is a diagram showing an example of path switching when the switching device is applied to a ring network. Each of N1 to N8 indicates the switching device 1 of the first embodiment as a node of the ring network. In each section of this ring network,
As shown in, the working path and the backup path are configured in each direction with the clockwise direction as the up direction and the counterclockwise direction as the down direction. It should be noted that in each node, pair information is set such that the working path in the clockwise direction is associated with the backup path in the counterclockwise direction.

As shown in FIG. 12A, when the counterclockwise working path fails in the section between the nodes N2 and N3, the switching devices of N2 and N3 connecting this path counterclockwise. The surrounding working path is connected back to the clockwise protection path. Note that FIG. 12 (b)
As shown in, no switching is performed for the clockwise working path because no failure has occurred. Also, when the failure of the counterclockwise working path is recovered, it is sufficient to switch back from the spare to the working.

Therefore, according to the fifth embodiment,
In the ring network, the section in which the failure of the working path has occurred is switched by looping back to the path in the opposite direction, so that the section in which the working failure has occurred can be avoided and the failure can be switched.

[0108]

As described above, according to the present invention,
Since the upstream and downstream paths are switched independently, the number of upstream and downstream paths or the number of lightwave paths can be made asymmetric depending on the amount of traffic passing through. Further, in the redundant path in which the traffic volumes accommodated in the upstream path and the downlink path are asymmetric, it is possible to improve the path accommodation efficiency of the one path having the smaller traffic volume. This is because it is not necessary to accommodate the upstream path and the downstream path in the transmission path or the lightwave path in which the upstream path and the downstream path are set in advance as in the conventional switching method in the present invention, and either the upstream or downstream path accommodating transmission path. Alternatively, even if there is no free band in the lightwave path, a new redundant path can be continuously set for the path accommodating transmission line or the lightwave path in which the remaining free band exists.

FIG. 13 is a diagram showing the effect of improving the path accommodation efficiency of the lightwave path according to the present invention. FIG. 13 shows the number of light wave paths required in the up direction when the amount of traffic accommodated in the light path in the down direction is changed to 1 to 10 times that in the up direction. As shown in FIG. 13, the number of lightwave paths in the upstream direction can be reduced as the unpairiness of the traffic amount in the upstream direction and the traffic amount in the downstream direction becomes large. As a result, the path accommodation efficiency of the upstream lightwave path can be improved. By reducing the number of wavelengths used in the upstream lightwave path, the network cost of the optical multiplexer / demultiplexer, optical amplifier, optical switch, etc. can be reduced.

Even when the electrical layer path is not directly accommodated in the lightwave path but is directly accommodated in the transmission path, the number of the transmission paths accommodating the upstream paths can be similarly reduced, so that the cost of the transmission path can be reduced. Can be achieved.

Further, according to the present invention, since the upstream path and the downstream path are independently switched, it is possible to improve the survival probability of the path at the time of multiple failures. Here, since the constituent devices such as the laser light source, the optical transmitter / receiver unit, the electronic circuit, and the amplifier, which are the causes of the failure occurrence, use different devices independently for the upstream path and the downstream path, the failure location is the upstream location. It can be assumed that they occur independently for each transmission path or lightwave path unit in the direction and the downlink direction. In the conventional method, since the upstream path and the downstream path are switched at the same time, the upstream path and the downstream path are switched even if a failure occurs only in the lightwave path accommodating the upstream path. Therefore, if a failure occurs in the working of the upstream path and the backup of the downstream path, communication cannot be performed.
On the other hand, according to the present invention, it is possible to perform communication through the backup of the upstream path and the working of the downstream path. Therefore, according to the present invention, it is possible to improve the survival probability of a path when multiple failures occur.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a switching device according to first and second embodiments.

FIG. 2 is a diagram showing an example of a path configuration in the first and second embodiments.

FIG. 3 is a diagram showing an example of path switching at the time of a working failure in the first and second embodiments.

FIG. 4 is a switching control flow chart according to the first embodiment.

FIG. 5 is a switching control flow chart when S14 and S15 are omitted in the first embodiment.

FIG. 6 is a flow chart of switching control according to the second embodiment.

FIG. 7 is a flow chart of switching control when S114 is omitted in the second embodiment.

FIG. 8 is a diagram showing a configuration of a switching device including an optical XC unit according to a third embodiment.

FIG. 9 is a diagram showing a configuration example of a lightwave path according to a third embodiment.

FIG. 10 is a diagram showing an example of lightwave path switching according to the third embodiment.

FIG. 11 is a diagram showing an example of VP switching when a working VP fails in the fourth embodiment.

FIG. 12 is a diagram showing an example of path switching for a ring according to a fifth embodiment.

FIG. 13 is a diagram showing the effect of improving the accommodation efficiency of the lightwave path in the present invention.

FIG. 14 is a diagram showing a VP configuration example in conventional VP switching.

FIG. 15 is a diagram showing an example of VP setting in normal time in FIG.

16 is a diagram showing an example of VP switching in FIG.

FIG. 17 is a switching control flow chart in conventional VP switching.

FIG. 18 is a diagram showing a cell format of an APS cell in conventional VP switching.

FIG. 19 is a diagram showing a pair information holding unit for a VP and a backup VP in conventional VP switching.

[Explanation of symbols]

1,1A, 1B, 2,2A, 2B switching device 11 Switch part 12 Routing information holding unit 13 Path switching control unit 14 Pair information holding unit 15 Input signal abnormality detector 16 Host device IF section 21 Optical XC section 22 Optical demultiplexer

Continued front page    F term (reference) 5K002 AA06 DA13 EA03 EA32 EA33                       FA01                 5K028 AA06 AA11 BB08 CC02 EE05                       KK01 KK03 KK12 MM05 MM08                       MM12 MM14 NN02                 5K031 AA08 CA15 DA19 DB10 DB14                       EB05

Claims (8)

[Claims] 1. A means for individually storing pair information indicating a working path and a protection path in an up direction and a down direction, and routing information indicating an input path and an output path in an up direction and a down direction, respectively. When a switching request is made, the switching request having the highest priority to the selector in the switching device, the bridge selection position and the selector selection position are transmitted as switching control information to the opposite switching device, A path switching device that performs switching control of a selector and a bridge individually for a path in a downward direction and according to a switching request with the highest priority. 2. A path switching system comprising a switching device in which pair information indicating a working path and a backup path and routing information indicating an input path and an output path are individually stored for each of an up direction and a down direction. Therefore, one of the switching devices transmits the switching request with the highest priority to the selector in the switching device as the switching control information to the opposite switching device. The path switching system is characterized in that the normal termination or abnormal termination of the switching of the bridge individually and the selection position of the bridge are responded as the switching control information. 3. A path switching method performed by a switching device, wherein pair information indicating a working path and a protection path and routing information indicating an input path and an output path are individually stored for an up direction and a down direction. When making a request, the switching request with the highest priority to the selector in the switching device, the bridge selection position, and the selector selection position are transmitted as switching control information to the opposite switching device, and the upstream and downstream paths are A path switching method characterized by performing switching control of a selector and a bridge individually and according to a switching request having the highest priority. 4. A path switching method for performing switching between switching devices in which pair information indicating a working path and a protection path and routing information indicating an input path and an output path are individually stored for each of an up direction and a down direction. Then, from one switching device, the system to which the switching request with the highest priority is applied to the selector in this switching device is sent to the opposite switching device as the switching control information, and the opposite switching device And a normal termination or abnormal termination of bridge switching individually performed in the down direction and a bridge selection position are returned as switching control information. 5. The path switching method according to claim 3, wherein switching control is performed in the electrical layer, switching is performed in the optical layer, and switching is performed using a lightwave path as a switching unit. 6. The path to be switched is a V of the ATM layer.
P, the switching control information is included in an APS cell, and the pair information includes a transmission line number and a VP identifier of a transmission line accommodating a working VP, and a transmission line number of a transmission line accommodating a backup VP. The routing information is information including a VP identifier, and the routing information includes a transmission line number and a VP identifier of a transmission line accommodating an input VP, and a transmission line number and a VP identifier of a transmission line accommodating an output VP. And V
5. The path switching method according to claim 3, wherein the routing information is rewritten after P switching. 7. A path to be switched is a V of an ATM layer.
C, the switching control information is included in an APS cell, and the pair information includes a transmission path number of a transmission path accommodating a working VP, a VP identifier and a VC identifier, and a transmission path accommodating a backup VP. The routing information is information including a route number, a VP identifier, and a VC identifier, and the routing information is the input VP.
Transmission line number, VP identifier, and VC of the transmission line accommodated by
An identifier and a transmission path number of a transmission path accommodating the output VP,
This information is composed of a VP identifier and a VC identifier.
The path switching method according to claim 3, wherein the routing information is rewritten after the switching. 8. When a switching device is installed at both ends of each section of the ring network to accommodate a working path and a backup path,
8. A path switching method performed by switching devices at both ends of a section in which a working path has a fault, wherein the switching destinations are folded back and connected to paths in opposite directions of adjacent sections, respectively. Or the path switching method described.