JP2002057689A - Optical transmission network and optical channel setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set an optical channel for performing communication between nodes in the optical transmission network of a large scale in a short time. SOLUTION: This optical transmission network of the large scale is regionally or functionally divided into the optical transmission networks of a small scale and is constituted of the set. Also, as this optical channel setting method in the large scale optical transmission network, the setting processing of the optical channel is parallelly performed for the respective regionally/functionally divided optical transmission networks of the small scale, they are respectively connected and thus, the optical channel between a start point and an end point is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for configuring an optical transmission network and an optical channel connection setting technique for performing communication between nodes in the optical transmission network. In particular, the present invention relates to a method of configuring an optical transmission network configured using a wavelength division multiplexing (WDM) technique, and a technique of setting a connection of an optical channel between nodes.

[0002]

2. Description of the Related Art A method of setting an optical channel in a conventional optical transmission network will be described below. Here, an optical path network is assumed as an example of the optical transmission network. For the optical path network,
Literature "Kenichi Sato and Satoshi Okamoto" Development of Optical Path Layer Technology ", 1992 IEICE Autumn Conference SB-7-1 199
September, 2 years ”. Here, an optical path network using a WP having no wavelength conversion function will be described as an optical path network. Here, the optical path may be considered to be the same as the optical channel used in the claims.

FIG. 5 shows an optical transmission network having a conventional configuration, and FIG.
2 shows a procedure for setting / releasing an optical path by a backward signaling method using a packet as a control signal. In the optical transmission network of FIG. 5, adjacent nodes are connected by an optical fiber 107. Also, a description will be given using a backward method as a signaling method. The procedure for setting the optical path is as follows.

[0004] The node that has issued the optical path setting request is the start node 105, and the target node (end node 10).
Calculate the optimal path for setting the optical path up to 6). The method of calculating the optimal route is, for example, the Dijkstra method, but is not limited to a specific method. (The Dijkstra method is described in the literature: A.V. Aiho, "Data Structure and Algorithm," Baifukan, ISBN4-563- 00791-9).

[0005] When the path for setting the optical path is determined, the start node 105 transmits a signal to the end node 106 to check the use status of the wavelength on each link in the optical path setting path. Here, this signal is called a survey packet.

[0006] The investigation packet is transferred hop-by-hob along the optical path setting route, and is transmitted from the source node 105 to n.
At the nth node, the wavelength usage on the link between the (n + 1) th node to which the investigation packet is transferred next and the wavelength usage on the link from the start node 105 to the nth node Using the information, the wavelength use status at the link from the start node 105 to the (n + 1) th node is obtained.

As a result, the n-th node and (n + 1)
In the link between the first node and the (n + 1) th node, the optical path setting is performed because all the wavelength-multiplexed wavelengths are used for the optical path or the like. If there is no wavelength that can be used for the Nth node, the n-th node transmits a NACK packet to the source node 105, and the source node 105 receiving this NACK packet restarts the processing of the optical path setting route from the search. .

If there is a wavelength that can be used for setting an optical path in the link between the start node 105 and the (n + 1) th node, the investigation packet is sent to (n
+1) Transmit to the node. The above processing is performed from the start node 105 to the end node 1 along the optical path setting path.
The processing is sequentially performed at each node up to 06.

The arrival of the investigation packet at the destination node 106 means that the source node 105 and the destination node 106
Means that there is at least one wavelength that can be used for setting an optical path. The destination node 106 receiving the investigation packet selects one wavelength used for optical path setting from the wavelengths available for optical path setting between the start point and the end point, and the investigation packet is transferred to the start node 105. A signal for setting an optical path in the reverse direction on the same route as the route is transmitted.

Here, this signal is called a setting packet. In the setting packet, information on the wavelength used for setting the optical path and the like are described. The configuration packet is
The node positioned nth from the start node 105 on the optical path setting path performs a process for setting an optical path with the (n-1) th node to which the setting packet is transferred next.

If an optical path cannot be set between the n-th node and the (n-1) -th node using the wavelength selected by the end node 106, the start node 1
A NACK packet for transmitting the optical path setup failure is transmitted to the client 05. At the same time, the optical path set between the n-th node that failed to set and the end point node 106 is released.

[0012] The start-point node 105 that has received the NACK packet indicating that the optical path setup has failed fails again from the route search. The above-described processing is sequentially performed for each node along the optical path setting path, and the start node 105 receives the setting packet transmitted from the end node 106, whereby the setting of the optical path succeeds, and the start nodes 105 to 105 An optical path is set between the nodes 106.

The start node 105 starts transferring data to the end node 106. When the data transfer is completed and the set optical path becomes unnecessary, the optical path release processing is started. The procedure for releasing the set optical path is as follows. The start node 105 transmits a release request packet, which is a signal for requesting release of the optical path, to the end node 106.

End point node 1 receiving the release request packet
06 transmits a signal for releasing the optical path to the starting point node 105. Here, this signal is called a release packet. The relay node that has received the release packet releases the set optical path.

The source node 105 that has received the release packet
Transmits an ACK packet for transmitting the completion of the optical path setting release to the destination node 106, and
However, receiving the ACK packet completes the optical path release processing. The optical path network used here and the optical channel used in the present invention may be considered to be the same.

[0016]

In the conventional method as described above, the size of an optical transmission network (WP network) composed of nodes having no wavelength conversion function becomes large (the nodes constituting the optical transmission network). However, there has been a problem that the success rate of setting an optical channel between the start node and the end node decreases, and the setting time of the optical channel increases.

(References: Masaaki Mukoto, Satoshi Okamoto, "Proposal of Dynamic Optical Path Setting Protocol", IEICE
PNI Study Group, May 2000, PNI2000-5 PP.34). Also,
Also in the recovery method at the time of the optical channel failure using the conventional signaling method, there is a problem that the setting time of the optical channel similarly increases and it is difficult to recover the failure in a short time.

[0018]

According to the present invention, the above-mentioned object is solved by the means described in the claims. That is, according to the first aspect of the present invention, adjacent nodes are locally and functionally divided in an optical transmission network connected by an optical fiber through which an optical signal wavelength-multiplexed by the wavelength division multiplexing technique is propagated. It is an optical transmission network composed of a set of subnets, which are optical transmission networks.

According to a second aspect of the present invention, in the optical transmission network according to the first aspect, adjacent subnets are connected by a node having a function of connecting the adjacent subnets. .

According to a third aspect of the present invention, in the optical transmission network according to the second aspect, a node having a function of connecting subnets is configured to have a wavelength conversion function.

According to a fourth aspect of the present invention, in the optical transmission network according to the first aspect, a node having a function for connecting a subnet located in an arbitrary subnet in the optical transmission network is provided.
By not transmitting control / management information in the subnet to a node located in another different subnet, and not propagating control / management information in another different subnet to a node located in the subnet, , And control and management of an arbitrary subnet is performed independently of other subnets.

According to a fifth aspect of the present invention, there is provided a method for setting an optical channel between a start node and an end node existing in different subnets in the optical transmission network according to the first aspect, wherein paths for setting the optical channel are adjacent to each other. Decide to always go through the node that has the function to connect the subnet,
An optical channel is set by parallel processing for each subnet located along an optical channel setting path between a start node and an end node, and a function for connecting adjacent subnets to the optical channel set by parallel processing for each subnet. This is an optical channel setting method in which an optical channel is set between a start point node and an end point node by connecting at a node having the same.

According to a sixth aspect of the present invention, in the optical channel setting method according to the fifth aspect, when the setting of an optical channel in an arbitrary subnet fails, the optical channel is reset in the subnet. It is composed.

[0024] The invention of claim 7 is the invention of claims 1 to 4.
In the optical transmission network described above, in a process of recovering from a state in which communication cannot be performed due to a failure of an optical channel set between a start node and an end node, a failure recovery is performed in a subnet including a failure point. It was done.

As described above, the present invention divides a large-scale optical transmission network constituted by nodes having no wavelength conversion function into a plurality of small-scale optical transmission networks (with a small number of nodes),
A large-scale optical transmission network is configured as a set of divided optical transmission networks. This divided small-scale optical transmission network is called a subnet here.

The adjacent subnets are connected by a node having a function of connecting subnets such as a wavelength conversion function. Here, a node for connecting adjacent subnets is called a gateway node.

When an optical channel is set between a start node and an end node located on different subnets, the optical channel is set over a plurality of subnets. As described above in the section "Problems to be Solved by the Invention", setting an optical channel between the start point and the end point increases the setting time.

Therefore, according to the present invention, when an optical channel to be set extends over a plurality of subnets, an optical channel is set in parallel for each subnet. Also, an optical channel setting route is set from an arbitrary subnet to an adjacent subnet so as to always pass through a gateway node.

Therefore, as the optical channel setting section, the starting node to the gateway node, the gateway node to
A gateway node, a gateway node to an end point node, are connected to each optical channel set in these sections at the gateway node to set an optical channel between the start and end points.

The same applies to the case of a failure of the optical channel. The optical channel set by the above means is maintained and controlled between the start point and the end point and for each subnet, and when an existing optical channel is interrupted due to a failure in an arbitrary subnet, the failure is restored in the corresponding subnet. I do.

[0031]

FIG. 1 shows an optical transmission network according to the configuration of the present invention. In the configuration example shown in FIG. 1, the optical transmission network is divided into four subnets 103, each of which is composed of six nodes 101 and a plurality of gateway nodes 104. Adjacent nodes are connected by an optical fiber 107.

Each subnet is assumed to be a WP network composed of nodes having no wavelength conversion function, but a VWP network composed of nodes having a wavelength conversion function or a WP / VWP mixed network in which these are mixed. Can also be configured. Adjacent subnet 103
They are connected by a gateway node 104, and the gateway node exists over two or more subnets.

The gateway node 104 is provided with functions necessary for connecting adjacent subnets. The functions include a wavelength conversion function. In addition, information such as the wavelength usage status of each link in the subnet, which is maintained and managed independently of the other subnets, for example, by not transmitting the used wavelength information of each link in the subnet to other subnets, Perform subnet management independently.

Source node 105 in a different subnet
Optical channel 102 set between the destination node 106
Is set from the start node 105 to the end node 106 via the gateway node 104 at least once. FIG.
FIG. 3 is a diagram showing a recovery method when an optical channel fails in the optical transmission network configured according to the present invention.

In FIG. 2, the gateway node 104-
If the working optical channel 102 fails in the subnet including the communication nodes 1 and 104-2, the start node 10
Rather than resetting the optical channel between 5 and the end point node 106, recovery is performed within the subnet including the failure point. In FIG. 2, failure recovery is performed by setting the optical channel 201 between the gateway nodes within the subnet including the gateway nodes 104-1 and 104-2.

[First Embodiment] FIG. 3 shows an optical channel setting procedure based on backward signaling according to the first embodiment of the present invention in the optical transmission network shown in FIG. Here, the start node 105 and the end node 106 are assumed to belong to different subnets. This applies to other embodiments described later.

In this embodiment, a packet is used as a control signal for processing such as setting or canceling of an optical channel. However, wavelength information, node information, route information and the like necessary for setting are described. In this case, the signal is not limited to a packet. For example, an overhead byte of a layer 1 signal can be used.

These control packets are transferred using a dedicated optical channel always terminated between adjacent nodes, for example, an optical section monitoring channel. Also, here
Although it is assumed that each subnet has a WP network configured by nodes having no wavelength conversion function, the present invention is not limited to this, and the present invention is not limited to this. The present invention can be similarly applied to a subnet constituted by a mixed network.

The node that first receives the optical channel setting request becomes the start node 105, and searches for an optimal route for setting the optical channel 102 to the target node (end node 106). As the optimum route, for example, a route including the largest number of wavelengths that can be used for optical channel setting between the start node 105 and the end node 106 is considered, but the number of hops and the distance between the start point and the end point are the smallest (short). A route or a route obtained by using all of them as parameters may be used.

The method for calculating the optimum route is, for example, the Dijkstra method, but is not limited to a specific method. The start node 105 is a gateway node 10 that travels on the way to an end node 106 located on a different subnet.
The optical channel setting route including 4-1 and 104-2 is obtained by calculation based on the route information. When the route is determined, the start node 105 transmits a signal to the end node 106 to check the usage status of the wavelength on each link in the optical channel setting route.

This signal is referred to herein as a survey packet. The investigation packet is transferred hop-by-hop along the optical channel setting path. The investigation packet is forwarded to the destination node 106, but first, the source node 105
In this case, the usable wavelength of the optical channel setting route from the first to the gateway node 104-1 that passes through is checked.

From the start node 105 to the n-th node, the wavelength usage status on the link between the (n + 1) -th node to which the next investigation packet is transferred and the interval between the start node 105 and the n-th node From the source node 105 using the information on the wavelength usage status in the link of (n +).
1) Obtain the wavelength usage status in the link up to the node.

As a result, all the wavelengths multiplexed on the link between the n-th node and the (n + 1) -th node are transmitted from the start-point node 105 because the wavelengths are used for an optical channel or the like. If there is no wavelength that can be used for optical channel setting in the link between the (n + 1) -th node, the n-th node transmits a NACK packet to the start node 105 and repeats the process from the route search. .

If there is a wavelength that can be used for optical channel setting in the link between the start node 105 and the (n + 1) th node, the investigation packet is sent to the (n
+1) Transmit to the node. The fact that the first gateway node 104-1 has received the investigation packet means that the source node 105 to the gateway node 104-1
This means that there is at least one wavelength that can be used for setting an optical channel.

The gateway node 104-1 selects one wavelength to be used for setting an optical channel from the wavelength information that can be used for setting the optical channel, and, toward the start-point node 105, uses the same route as the route on which the investigation packet was transferred. In the reverse direction, a signal for setting an optical channel is transmitted. here,
This signal is called a setting packet. In the setting packet, information on the wavelength used for setting the optical channel and the like are described.

By transmitting the packet set by the gateway node 104-1 to the start node 105,
The setting of the optical channel is started between the starting node 105 and the gateway node 104-1 independently of the subnet located downstream on the setting route (in the investigation packet transmitting direction).

The setting packet is used to set an optical channel between the (n-1) th node to which the next setting packet is transferred in the nth node from the start node 105 on the optical channel setting path. Perform processing. If the optical channel cannot be set between the n-th node and the (n-1) -th node using the wavelength selected by the gateway node 104-1, the setting of the n-th optical channel has failed. For releasing the optical channel set between the node and the gateway node 104-1 and for transmitting the optical channel setting failure to the source node 105 at the same time.
Send a NACK packet.

Upon receiving the NACK packet indicating that the optical channel setting has failed, the start node 105 performs a route search, and searches for the start node.
The process of resetting the optical channel between the gateway nodes 104-1 is performed again. At this time, the start node 105 transmits the investigation packet not to the end node 106 but to the gateway node 104-1.

Start node 105 to gateway node 1
At the same time as transmitting a setting packet for setting an optical channel to the source node 105 between the nodes 04-1 and 04-1, the gateway node 104-1 initializes the usable wavelength information of the investigation packet previously received, and Of the link, and if there is an available wavelength, it is forwarded to the end node 106. If there is no usable wavelength, the gateway node 104-1 changes to the end node 106.
Calculate again the optical channel setting path up to and try to reset it.

Between the gateway node 104-1 and the gateway node 104-2, the gateway node 104-
Investigation of the wavelength use status by the investigation packet for setting the optical channel between the second to end nodes 106 is the same as described above, but between the gateway nodes 104-1 to 104-2 and the gateway node 104-2.
When there is no available wavelength between the end node 106 and the NACK packet returned to the start node 105, the NACK packet returned by the upstream gateway node on the optical channel setting path located in the same subnet as the node that transmitted the NACK packet is The NACK packet is processed and is not relayed toward the source node 105.

The gateway node receiving the NACK packet recalculates the optical channel setting route to the destination node 106, and transfers the investigation packet to the destination node 106. The processing is similar to the method described above.

The gateway node 104-2 and the destination node 106, which have received the investigation packet, arbitrarily select one wavelength that can be used for optical channel setting on the optical channel setting path in each subnet, and send the setting packet to each of the gateway nodes. 104-1, gateway node 10
4-2, and the optical channel is set. The setting of the optical channel is the same as that between the start node 105 and the gateway node 104-1.

The gateway node that has received the setting packet confirms that the optical channel has been set in the downstream subnet belonging to itself, connects to the optical channel set in the upstream subnet, and starts from the start node 105 to the end node 1.
06, the optical channel 102 is opened.

The connection of each optical channel at the gateway node is performed using, for example, an identifier for identifying the optical channel to be connected. The setting of the optical channel between the start node 105 and the end node 106 is confirmed in the following procedure. In the first subnet on the optical channel setting path, the source node 105 is the gateway node 104-1.
Receiving the setting packet from the source node 105
The setting of the optical channel between the gateway node 104-1 and the gateway node 104-1 is completed.

The starting node 105 that has received the setting packet
Transmits a setting confirmation packet, which is a signal, for confirming the setting between the start and end points of the optical channel to the end point node 106. The gateway node 104-1 that has received the setting confirmation packet transmits a setting confirmation packet if an optical channel is set between the gateway node 104-1 and the gateway node 104-2 in the next adjacent subnet on the optical channel setting path. To the gateway node 1
Send it to 04-2.

If the optical channel has not been set, the gateway node 104-1 transmits a NACK packet to the source node 105. Upon receiving the NACK packet, the start-point node 105 transmits a setting confirmation packet again after a predetermined time has elapsed, and performs the above processing in the order of subnets. Upon receiving the setting confirmation packet, the end node 106 transmits an ACK packet indicating that the setting of the optical channel 102 has been completed between the start point and the end point to the start node 105, and the start node 105 receives the ACK packet. By doing so, an optical channel is set between the start node 105 and the end node 106. The setting confirmation packet and the ACK of the setting confirmation packet may be transmitted using the set optical channel.

The start node 105 repeats the above processing until an ACK packet is received.
If no K packet is received, the source node 10
It is determined that the setting of the optical channel among the fifth to end nodes 106 has failed, and the corresponding optical channel is released. The data transmission ends, and the setting of the unused optical channel is released. The procedure for releasing the optical channel is the same as that in the above-described conventional example.

[Second Embodiment] FIG. 4 shows an optical channel setting procedure based on backward signaling according to a second embodiment of the present invention in the optical transmission network shown in FIG. still,
In this embodiment, a packet is used as a control signal for processing such as setting or canceling of an optical channel. However, if wavelength information, node information, route information, etc. necessary for setting are described, the signal is However, it is also possible to use an overhead byte of, for example, a layer 1 signal.

These control packets are transferred using a dedicated optical channel that is always terminated between adjacent nodes, for example, an optical section monitoring channel. Here, each subnet is assumed to be a WP network constituted by nodes having no wavelength conversion function. However, the present invention is not limited to this, and the present invention provides a VWP network constituted by nodes having a wavelength conversion function. Alternatively, the present invention can be similarly applied to a subnet configured by a mixed network of the two.

The node that first receives the optical channel setting request becomes the start node 105, and searches for an optimum route for setting the optical channel 102 to the target node (end node 106). However, since the end node 106 is located on a different subnet from the start node 105, the start node 105 calculates not the route to the end node 106 but the optimum route to the end node 106 based on the route information.

As the optimum route, for example, a route that includes the largest number of wavelengths that can be used for setting an optical channel can be considered, but the number of hops and the distance between the start and end points are the smallest (short), or all of them are used as parameters. May be the route required. The method of calculating the optimum route includes, for example, the Dijkstra method, but is not limited to a specific method.

When the route is determined, the start node 105
A signal is transmitted to the gateway node 104-1 to check the usage status of the wavelength on each link in the optical channel setting path. Here, this signal is called a survey packet. The investigation packet is transferred hop-by-hop along the optical channel setting path.

In the n-th node from the start node 105, the wavelength use status on the link between the (n + 1) -th node to which the investigation packet is transferred next and the start node 1
Using the information on the wavelength usage status in the link from 05 to the n-th node, the wavelength usage status in the link from the start node 105 to the (n + 1) -th node is obtained.

As a result, in the link between the n-th node and the (n + 1) -th node, all the wavelength-multiplexed wavelengths are used for the optical channel or the like. If there is no wavelength that can be used for optical channel setting in the link between the (n + 1) -th node, the n-th node transmits a NACK packet to the start node 105 and repeats the process from the route search. .

If there is a wavelength that can be used for optical channel setting in the link between the start point node 105 and the (n + 1) th node, the investigation packet is set to (n +
1) Transmit to the node. Gateway node 1
The fact that 04-1 has received the investigation packet means that there is at least one wavelength that can be used for optical channel setting between the source node 105 and the gateway node 104-1.

The gateway node 104-1 selects one wavelength to be used for setting an optical channel from the wavelength information that can be used for setting the optical channel, and reverses the same on the same route as the route on which the investigation packet was transferred to the source node 105. Transmit a signal to set the optical channel in the direction. Here, this signal is called a setting packet.

In this setting packet, information on the wavelength used for setting the optical channel and the like are described. At the same time, the gateway node 104-1 calculates an optical channel setting path to the destination node 106 which is the final destination node of the investigation packet. In the case of the optical transmission network shown in FIG. 1, the destination node 106 is not included in the subnet including the gateway node 104-1.

Therefore, the gateway node 104-1
Calculates the optimal route to the gateway node 104-2 in order to transmit the investigation packet to the gateway node 104-2 that can set the optimal route to the end point node 106. After the determination of the optimum route, the status of the wavelength used in the link with the next node is checked, and if there is an available wavelength, it is transmitted to the gateway node 104-2.

If there is no usable wavelength, the gateway node 104-1 changes to the gateway node 104-2.
Calculate again the optical channel setting path up to and try to reset it. By repeatedly executing the above processing procedure, the investigation packet transmitted from the start node 105 reaches the end node 106. Each gateway node 104
-1, 104-2, the end point node 106 immediately sets the optical channel in the subnet after receiving the investigation packet.

The setting packet is transmitted to the start node 105 or the gateway node in the same subnet. The setting of the optical channel in each subnet is the same as in the first embodiment. When the start node 105 or the upstream gateway node receives the setting packet,
The optical channel is set in the subnet.

Then, the optical channels set between the start node 105 and the end node 106 are connected by connecting the gateway nodes that relay the optical channels set in the respective subnets.
The setting of 2 is completed. This processing procedure is the same as in the first embodiment. When the data transmission ends, the setting of the unused optical channel is released. The procedure for releasing the optical channel is the same as in the above-described conventional example.

[0072]

As described above, according to the optical transmission network and the optical channel setting method of the present invention, in a large-scale optical transmission network, an optical channel can be set in a plurality of subnets in parallel. Therefore, as compared with the conventional method, the success rate of optical channel setting can be increased, and the setting of the optical channel can be performed in a short time. Also, by providing a subnet, even in the event of a failure, the effect of the failure can be prevented from being propagated to all nodes in the network, and thus there is an advantage that recovery from the failure can be performed in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of the configuration of an optical transmission network according to the present invention.

FIG. 2 is a diagram illustrating a failure recovery method in an optical transmission network according to the present invention.

FIG. 3 is a diagram illustrating an optical channel setting / releasing method using backward signaling according to the first embodiment.

FIG. 4 is a diagram illustrating an optical channel setting / releasing method using backward signaling according to a second embodiment.

FIG. 5 is a diagram illustrating an example of a configuration of a conventional optical transmission network.

FIG. 6 is a diagram illustrating a conventional optical channel setting / releasing method using backward signaling.

[Explanation of symbols]

 101 Node 102, 201 Optical Channel 103 Subnet 104-1, 104-2 Gateway Node 105 Start Node 106 End Node 107 Optical Fiber

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K002 DA02 DA09 EA05 EA06 FA01 5K030 GA01 HA01 HA08 JL03 LA17 LB01 5K033 AA01 CB01 CC01 DB22

Claims (7)

[Claims] 1. An optical transmission network in which adjacent nodes are connected by an optical fiber through which an optical signal wavelength-division multiplexed by a wavelength division multiplexing technique is propagated. An optical transmission network comprising a set of subnets, which are optical transmission networks. 2. The optical transmission network according to claim 1, wherein adjacent subnets are connected by nodes having a function of connecting the adjacent subnets. 3. The optical transmission network according to claim 2, wherein the node having a function of connecting subnets has a wavelength conversion function. 4. A node having a function of connecting a subnet located in an arbitrary subnet in an optical transmission network transmits control / management information in the subnet to a node located in another different subnet. 2. The control / management of an arbitrary subnet is performed independently of other subnets by not propagating and not propagating control / management information of another different subnet to a node located in the subnet. Light transmission network. 5. A method for setting an optical channel between a start node and an end node existing in different subnets in the optical transmission network according to claim 1, wherein the route for setting the optical channel is connected to adjacent subnets. Was determined to always pass through a node having the function of, and an optical channel was set by parallel processing for each subnet located along the optical channel setting path between the start node and the end node, and set by parallel processing for each subnet An optical channel setting method, wherein an optical channel is set between a start node and an end node by connecting an optical channel at a node having a function of connecting adjacent subnets. 6. The optical channel setting method according to claim 5, wherein when setting of an optical channel in an arbitrary subnet fails, the optical channel is reset within the subnet. 7. When an optical channel set between a start node and an end node in the optical transmission network according to claim 1 is in a state where communication cannot be performed due to a failure,
An optical transmission network, characterized in that in a process of recovering from the state, a fault recovery is performed in a subnet including a fault point.