JP3822518B2 - Backup optical path bandwidth securing method and optical path switching device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a backup optical path bandwidth securing method for securing a bandwidth of a backup optical path in an optical path switching device (optical router) in a large-capacity optical communication network, and an optical path switching device for realizing the same.
[0002]
[Prior art]
Due to an increase in data communication traffic such as the Internet, the introduction of node devices having a throughput of Tbit / s at present and 10 to 100 Tbit / s or more in the near future is being studied. As means for realizing such a node device having a large-scale transfer capability, the limit of electrical processing is exceeded, so an optical router (reference: K. Shimano et al., In Technical Digest of NFOEC'2001, vol.1) , p.5, 2001). In this optical router, the management of the optical communication network is performed in a distributed manner for each node, and the optical path connection setting is also performed based on the signaling process between the nodes. That is, in an optical communication network using an optical router, optical path setting management is performed autonomously and distributedly for each node.
[0003]
In such an optical communication network, a shared protection method is promising as a means for providing a highly reliable network service while effectively using resources. This method secures a spare optical path band accommodated in a completely different path from the working optical path, and shares this spare optical path band with spare optical paths for other working optical paths. As a result, it is possible to ensure predetermined reliability while saving the resources of the backup optical path required for the entire network.
[0004]
[Problems to be solved by the invention]
By the way, in order to realize the shared protection method in such an autonomous distributed optical communication network, it is necessary to extend a signaling protocol for securing a backup optical path band. For example, as shown in FIG. 12, when a bandwidth is reserved for a working optical path and a bandwidth is secured, the optical path is opened along the paths of nodes # 1, # 2, # 3, and # 6. On the other hand, with respect to the backup optical path, it is only necessary to register the use of the band to which the backup optical path corresponds, so that the actual optical path is not connected until the working optical path becomes inaccessible due to some influence. There is a need. Therefore, when the bandwidth of the backup optical path is secured by a signaling process similar to the setting of the working optical path, it is necessary to include identification information that makes it clear that the backup optical path is set.
[0005]
Furthermore, in order for the shared protection method to function effectively, the standby optical path is not set so that a plurality of working optical paths that are switched due to a failure of a part of the network device do not secure the same standby optical path bandwidth together. Need to be set.
[0006]
The present invention takes into account the above points, and automatically sets a spare optical path, and further, a spare optical path bandwidth securing method and an optical path switching capable of minimizing the amount of equipment required for the spare optical path. An object is to provide an apparatus.
[0007]
[Means for Solving the Problems]
The present invention relates to a backup optical path bandwidth securing method for securing a bandwidth of a backup optical path to be switched when a working optical path becomes unusable at a node of an optical communication network. against the downstream node, Ri Oh the optical path in the backup optical path, and the identification information indicating the shared protection der Rukoto the band of the backup optical path is shared with other backup optical path, to the backup optical paths The danger classification information to which the corresponding working optical path belongs is notified.
[0008]
Further, each node of the backup optical path bandwidth securing method of the present invention is notified when the active optical path risk classification information is notified from the downstream node (or upstream node) that secures the bandwidth when the working optical path is connected. The risk classification information of the link that accommodates the node and the active optical path connected to the node is added to the upstream node (or the downstream node).
[0009]
The present invention provides an optical path setting management in an optical path switching device having an optical path setting management function unit that secures a bandwidth of a backup optical path to be switched when a working optical path set in an optical communication network becomes unusable. The functional unit includes: a database that holds the risk classification information registered in the optical channel accommodated in the optical path switching device, the risk classification information of each link connected to the optical path switching device, and the optical path switching device; The protection optical path setting process for inputting the risk classification information notified from the other optical path switching device when securing the protection optical path bandwidth and outputting the bandwidth secured as the protection optical path and the risk classification information registered in the database Part.
[0010]
The risk classification information registered in the optical channel is the risk classification information to which the working optical path that secures the optical path as a backup optical path band belongs.
[0011]
Further, the protection optical path setting processing unit sets the risk classification information sets A1, A2,..., An held by the optical channel group existing on the route for which the protection optical path is to be secured, and the protection optical path to be set. In this configuration, an optical channel in which the logical product of the set B of the risk classification information possessed by the working optical path is φ (empty set) is searched. Alternatively, a set of risk classification information A ′ 1, A ′ 2,..., A ′ that exists on the path for which the protection optical path is to be secured and that is already set as the protection optical path band. An optical channel in which the logical product of n and the set B of risk classification information of the input optical path connection request is φ (empty set) may be searched first.
[0012]
Here, the risk classification information is a numerical value assigned to a single unit, a subset, or an entire set of links and nodes that accommodate the working optical path.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows a configuration example of an optical path switching apparatus according to the present invention. In the figure, the optical path switching device is composed of a packet switch unit 1, an optical switch unit 2, and an integrated control function unit 3 that integrally manages them. The optical switch unit 2 uses, for example, a 128 × 128 switch, and has a capability of connecting four fiber links multiplexed with 32 optical paths and inputting and outputting 128 optical paths. The transmission speed of each optical path is 2.5 Gbit / s and is terminated with a SONET OC-48 interface.
[0014]
The integrated control function unit 3 of each optical path switching device exchanges advertisement information control signals with each other via a control signal line. The control signal line consists of a SONET OC-3 line with a transmission rate of 155 Mbit / s. The control signal is, for example, between OSPF / IS-IS protocol packets for acquiring the network topology of an optical communication network, or between packet switches. RSVP-TE / CR-LDP protocol packet for setting / releasing the optical path set in step 1, and link management protocol (LMP) packet for monitoring the failure of each fiber link. Therefore, the integrated control function unit 3 is equipped with a function unit for processing these control signal protocols, and includes a routing processing function unit (OSPF / IS-IS protocol processing function unit) 31, an optical path setting management function unit (RSVP). -TE / CR-LDP protocol processing function unit) 32, and a link failure management function unit (LMP protocol processing function unit) 33 that manages failures of optical fibers and adjacent nodes.
[0015]
The routing processing function unit 31 has a function of defining a cost for each fiber link and searching for a route that minimizes the fiber link cost accumulated between the start node and the end node of the optical path to be set. The Dijkstra method is applied to the search algorithm. In addition, the routing processing function unit 31 has a database that holds risk classification information of the own node and each link connected to the own node, and defines the risk classification for each fiber link and each node.
[0016]
FIG. 2 shows a configuration example of the optical communication network in the first embodiment of the present invention. In the figure, risk classification information 91 to 96 is assigned to nodes # 1 to # 6, respectively. Further, for example, when the fiber link connecting the nodes # 1 and # 2 is expressed as “12” by taking the node number, the risk classification information 80 is assigned to the fiber link 12, and the fiber links 14, 23, and 24 are similarly used. , 35, 36, 45, 56 are assigned risk classification information 81, 82, 82, 85, 84, 83, 86, respectively.
[0017]
Here, for convenience, the node risk classification information is in the 90s and the fiber link risk classification information is in the 80s. Further, the same risk classification information 82 is assigned to the fiber link 23 and the fiber link 24, which means that both fiber links are accommodated in the same earthen pipe in some sections, and the risk of simultaneous fiber cutting occurs. It shows that the nature is high.
[0018]
The optical path setting management function unit 32 has a database that holds optical path route information input to and output from the node and optical channel attribute information input to and output from the node. In this database, risk classification information to which the set optical path or backup optical path belongs is registered and managed in units of optical channels (risk classification information DB in units of optical channel interfaces). Also, not only the risk classification information notified from other nodes when securing the spare optical path bandwidth is input, but also outputs the optical channel to be secured as the spare optical path and the newly updated risk classification information. It has a backup optical path setting processor that searches for an optical channel that accommodates the path. The working optical path is set according to the route instructed by the routing processing function unit 31.
[0019]
FIG. 3 shows a working optical path setting sequence. A temporary optical band reservation request for the working optical path is notified from the starting node # 1 to the final node # 6, and the node # 6 receiving it requests the node # 1 to secure the band of the working optical path. Notice.
[0020]
FIG. 4 shows a backup optical path setting sequence.
Step 1: Of the fiber link costs registered in the routing processing function unit 31, it is assumed that the fiber link cost of the set route of the working optical path is infinite only when the route of the protection optical path is searched. This is a measure for setting a backup optical path by a route different from the same fiber link as the working optical path.
[0021]
Step 2: When a route based on the restriction in Step 1 can be found, the starting node # 1 notifies the downstream node on the route of the preliminary optical path bandwidth reservation. This notification signal includes identification information indicating that a backup optical path is set, and risk classification information to which the working optical path corresponding to the backup optical path belongs. However, the risk classification information of the start node # 1 and the end node # 6 of the working optical path is not included. This risk classification information is obtained from the routing processing function unit 31 of the starting node # 1 when calculating the route of the working optical path.
[0022]
Step 3: The downstream node that has received the preliminary optical path bandwidth reservation notification searches whether there is a bandwidth (optical channel) that can be secured toward the end node # 6. For example, as shown in FIG. 5, the optical switch unit 2 of the node # 4 switches the path of the optical channel of the three fiber links 14, 24, 45, and the wavelength converter ( WC) performs wavelength conversion of the signal light. The node # 4 holds risk classification information to which the optical channel belongs as attribute information of the optical channel input / output to / from its own node. The risk classification information held by the optical channel at the time of system startup is that of the own node, the optical channel accommodating fiber link, and the opposite node of the optical channel.
[0023]
Based on this database, if an optical channel that can secure the backup optical path bandwidth is found, the backup optical path bandwidth reservation is provisionally registered in the database that holds the status of the optical channel for which the bandwidth is temporarily reserved, and The risk classification information held by the working optical path of the optical path is provisionally registered. After that, a preliminary provisional bandwidth reservation is notified to the downstream node. This notification signal includes identification information indicating that a backup optical path is set, and risk classification information to which the working optical path corresponding to the backup optical path belongs. A similar operation is performed in all of the backup optical path relay nodes.
[0024]
Step 4: Receiving the preliminary optical path bandwidth provisional reservation notice, node # 6 at the end point internally reserves the necessary spare optical path bandwidth in its own node, and holds the state of the optical channel to be temporarily reserved on it Provisional registration for securing the spare optical path bandwidth is performed in the database, and the risk classification information held by the working optical path of the spare optical path is registered. Then, it notifies the upstream node of “reserved bandwidth”. However, the optical switch unit 2 of the optical path switching device does not operate at all for reserve bandwidth reservation of the backup optical path, and only the database update process of the integrated control function unit 3 is performed.
[0025]
Step 5: The relay node that has received the preliminary bandwidth reservation notification from the downstream node performs the main registration of the standby optical path bandwidth reservation in the database that holds the temporarily reserved optical channel state, and the working optical path of the standby optical path is retained. The risk classification information to be registered is fully registered. Then, the upstream node is notified of the reserved bandwidth of the backup optical path. Also in the relay node, the optical switch unit 2 of the optical path switching device does not operate at all for securing the bandwidth of the backup optical path, and only the database update process of the integrated control function unit 3 is performed. A similar operation is performed in all of the backup optical path relay nodes.
[0026]
Step 6: The starting node # 1 that has received the band backup reservation notification from the downstream node performs main registration of backup optical path band reservation in the database holding the temporarily reserved optical channel state, and the working light of the backup optical path Completely register the risk classification information held by the pass. Even at the starting node # 1, the optical switch unit 2 of the optical path switching device does not operate at all for securing the bandwidth of the backup optical path, and only the database update process of the integrated control function unit 3 is performed.
[0027]
As described above, the risk classification information to which the working optical path that secures the optical channel as the spare optical path band belongs is registered in the database that holds the information of the optical channel secured as the spare optical path.
[0028]
With such a series of operations, if the backup optical path bandwidth is secured, even if the working optical path falls into a communication impossible state due to a failure in the transmission path, etc., it is quickly switched to the preset backup optical path. be able to.
[0029]
(Second Embodiment)
FIG. 6 shows an example of the configuration of an optical communication network in the second embodiment of the present invention. In the figure, the risk classification information assigned to the nodes # 1 to # 6 and each fiber link is the same as that of the first embodiment shown in FIG. 2, and the basic operation is also the same as that of the first embodiment. Here, an optical path is set from node # 1 to node # 5.
[0030]
A feature of the present embodiment is that it corresponds to a case where a technique called crankback is introduced in the provisional bandwidth reservation notification of the working optical path. Crankback is a type of abnormal processing that occurs when provisional bandwidth reservation fails at a certain relay node when provisionally reserving the bandwidth of an active optical path based on a route in accordance with an instruction from the routing processing function unit 31. . That is, in the example shown in FIG. 6, after the node # 4 fails to secure the band and returns to the node # 2 that is one upstream, the shortest path from the node # 2 to the terminal node # 5 is searched again. A bandwidth preliminary reservation notification is made according to the route. Here, the shortest path from the node # 1 to the node # 5 is not the # 1- # 4- # 5 but the # 1- # 2- # 3- # 5 is provided by the fiber link 14. This is because the number of channels is smaller than the fiber link 12 (high cost).
[0031]
FIG. 7 shows a working optical path setting sequence. FIG. 8 shows a backup optical path setting sequence. The basic setting sequence is the same as that of the first embodiment. However, when the provisional bandwidth reservation method of the present embodiment is introduced, the risk classification information held by the actually set working optical path does not necessarily match the risk classification information of the working optical path searched at the start node. . Therefore, when securing the bandwidth of the working optical path, the fiber link that accommodates the working optical path and the risk classification information of each node are notified to the upstream node, and the risk classification information that the actually set working optical path holds is the starting node. After that, a backup optical path is set according to the procedure of the first embodiment. Thereby, even when an abnormal process occurs when the working optical path is connected, the risk classification information held by the working optical path can be obtained accurately.
[0032]
(Third embodiment)
FIG. 9 shows a configuration example of the optical switch unit 2 in the third embodiment of the present invention. The basic operation is the same as that of the second embodiment. The feature of this embodiment is the backup optical path bandwidth securing algorithm performed at each node when setting up the backup optical path.
[0033]
In FIG. 9, the optical switch unit 2 of the node # 4 switches the route of the optical channels of the three fiber links 14, 24, 45, and the wavelength converter (WC) connected between the input and output thereof is the signal light. Wavelength conversion is performed. Here, when the backup optical path is secured, the risk classification information held by the working optical path notified from the upstream node and each optical channel to be secured for the end node of the backup optical path are held. Logical AND of risk classification information.
[0034]
Specifically, a set of risk classification information A1, A2,..., An held by the optical channels 1 to n to be reserved for bandwidth and the risk classification information held by the working optical path of the backup optical path to be set. An optical channel in which the logical product of set B is φ (empty set) is searched. This means an operation of searching for an optical channel that does not have the risk classification information of the backup optical path to be secured. That is, as shown in FIG. 10, a plurality of working optical paths having the same risk classification information are set not to select the same optical channel as their backup optical path band.
[0035]
By such an operation, the backup optical path band can be shared by a plurality of working optical paths, while a specific backup optical path band can be set so that the plurality of working optical paths do not meet each other due to a failure of the network device. . As a result, it is possible to construct a low-cost and high-reliability network with a high probability of failure recovery while suppressing the required amount of spare optical path equipment.
[0036]
(Modification of the third embodiment)
FIG. 11 shows a configuration example of the optical switch unit 2 in a modification of the third embodiment of the present invention. The basic operation is the same as that of the third embodiment. The feature of this embodiment is that the backup optical path bandwidth securing algorithm performed in each node at the time of setting the backup optical path is slightly different, and the optical channel for securing the bandwidth as the backup optical path is prioritized from the one already used as the backup optical path. The place is searched for.
[0037]
That is, a set of risk classification information A ′ 1, A ′ 2,..., A ′ that exists on a path for which a backup optical path is to be secured and that is already set as a backup optical path band. First, an optical channel in which the logical product of n and the set B of the risk classification information of the input optical path connection request is φ (empty set) is searched. In this search algorithm, when an optical channel suitable for securing a band as a backup optical path cannot be found, the optical channel search for the backup optical path is performed in the third embodiment.
[0038]
Through this process, in this embodiment, the optical channel A24 having the wavelength λ4 is reserved in the fiber link 45 as a spare optical path band for which setting is requested. In the optical channel A24, the bandwidth of the backup optical path (# 3- # 2- # 4- # 5- # 6) for the working optical path between the nodes # 3- # 6 accommodated in the fiber link 36 is also secured. It is in a state.
[0039]
Further, in the present embodiment, as in the third embodiment, the spare optical path band is shared by a plurality of working optical paths, while a specific spare optical path band is shared by a plurality of working optical paths due to a network device failure. Can be set so as not to meet each other. Thereby, the installation amount of the backup optical path can be suppressed as compared with the third embodiment.
[0040]
【The invention's effect】
As described above, the backup optical path bandwidth securing method and the optical path switching apparatus according to the present invention can automatically set the backup optical path to effectively function the shared protection method, and the backup optical path The amount of equipment required can be minimized. Thereby, a low-cost and highly reliable optical communication network can be constructed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of an optical path switching apparatus according to the present invention.
FIG. 2 is a diagram showing a configuration example of an optical communication network according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a working optical path setting sequence.
FIG. 4 is a diagram illustrating a backup optical path setting sequence.
FIG. 5 is a diagram showing a configuration example of an optical switch unit 2 in the first embodiment of the present invention.
FIG. 6 is a diagram illustrating a configuration example of an optical communication network according to a second embodiment of the present invention.
FIG. 7 is a diagram showing a working optical path setting sequence.
FIG. 8 is a diagram illustrating a backup optical path setting sequence.
FIG. 9 is a diagram illustrating a configuration example of an optical switch unit 2 according to a second embodiment of the present invention.
FIG. 10 is a diagram illustrating a configuration example of an optical communication network according to a third embodiment of the present invention.
FIG. 11 is a diagram illustrating a configuration example of an optical switch unit 2 according to a third embodiment of the present invention.
FIG. 12 is a diagram showing a basic configuration of an optical communication network.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Packet switch part 2 Optical switch part 3 Integrated control function part 31 Routing processing function part 32 Optical path setting management function part 33 Link failure management function part

Claims (8)

In a backup optical path bandwidth securing method for securing a bandwidth of a backup optical path to be switched when a working optical path becomes unusable at a node of an optical communication network,
Each node, with respect to the downstream node when bandwidth allocation backup optical path, the shared protection der Rukoto the optical path Ri Ah in backup optical path, and the bandwidth of the backup optical path is shared with other backup optical paths And a protection optical path bandwidth securing method characterized by notifying the identification information indicating the risk classification information to which the working optical path corresponding to the protection optical path belongs. The backup optical path bandwidth securing method according to claim 1 ,
When each node is notified of the risk classification information of the working optical path from the downstream node (or upstream node) that secures the band when the working optical path is connected, the working light connected to the node and the node is notified to this node. A backup optical path bandwidth securing method comprising adding risk classification information of a link accommodating a path and notifying an upstream node (or downstream node). In the backup optical path bandwidth securing method according to claim 1 or 2,
The protection optical path bandwidth securing method, wherein the risk classification information is a numerical value assigned to a single unit, a subset, or an entire set of links and nodes that accommodates the working optical path. In an optical path switching device having an optical path setting management function unit for securing a bandwidth of a backup optical path to be switched when a working optical path set in an optical communication network becomes unusable,
The optical path setting management function unit includes the optical path switching device, the risk classification information of each link connected to the optical path switching device, and the risk classification information registered in the optical channel accommodated in the optical path switching device. And the risk classification information notified from other optical path switching devices when securing the spare optical path bandwidth are input, and the bandwidth secured as the spare optical path and the risk classification information registered in the database are output. An optical path switching device comprising: a backup optical path setting processing unit. The optical path switching device according to claim 4,
The optical path switching device, wherein the risk classification information registered in the optical channel is risk classification information to which a working optical path that secures the optical path as a backup optical path band belongs. The optical path switching device according to claim 4,
The protection optical path setting processing unit sets the risk classification information sets A1, A2,..., An held by the optical channel group existing on the route for which the protection optical path is to be secured, and the protection optical path to be set. An optical path switching device characterized by searching for an optical channel in which the logical product of a set B of risk classification information held by an active optical path is φ (empty set). The optical path switching device according to claim 4,
The protection optical path setting processing unit is a set of risk classification information A ′ 1, A that exists in the optical channel group that exists on the route for which the protection optical path is to be secured and is already set as the protection optical path band. An optical path characterized by first searching for an optical channel whose logical product of '2, ..., A'n and the set B of risk classification information of the input optical path connection request is φ (empty set). Switching device. In the optical path switching device according to any one of claims 4 to 7,
The optical path switching device according to claim 1, wherein the risk classification information is a numerical value assigned to a single unit, a subset, or an entire set of links and nodes that accommodates the working optical path.

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