JP4098793B2 - Optical transmission system - Google Patents

Description

  The present invention relates to a transmission system applied to a backbone network or the like. In particular, the present invention relates to an optical transmission system known as an all-optical network, and a protection technology from a transmission path failure in this type of system.

In recent information transmission systems, a plurality of nodes are often connected in a mesh form via a link to form a mesh network. In order to allocate transmission resources of a mesh network to a plurality of communication paths, a method of searching for an optimum route by a routing algorithm has been applied conventionally. In recent years, attention has been focused on networks that transmit light transparently without converting optical signals into electrical signals at nodes. This type of network is called an all-optical network, and a plurality of logical bands can be provided on the link.
In this type of network, each transmission path is protected from failure using a backup transmission path set in correspondence with the respective transmission path. The dedicated protection method, in which each backup transmission path is assigned to each transmission path, has to secure a transmission band corresponding to all the backup transmission paths in the network, which is difficult in terms of transmission bandwidth usage efficiency. is there. In contrast to this method, the Shared Protection method in which each backup transmission path shares a transmission band is superior in terms of band use efficiency. This method is also used in the case of performing protection for a failed link by (wavelength) transmission of the (optical) cut-through method, that is, when performing protection collectively for traffic passing through the failed link.
Patent Documents 1 to 3 below disclose a path protection method in a transmission system. However, none of these documents are intended for all-optical networks.
Japanese Patent Laid-Open No. 2003-258851 JP 2003-273904 A JP 2002-344491 A

In a network that employs the Shared Protection method, when a plurality of transmission failures occur on the network, there is a possibility that the transmission band may compete between a plurality of backup transmission paths used for protection. If it is not possible to avoid this contention, protection corresponding to a plurality of failures cannot be performed.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transmission system capable of avoiding contention of protection wavelength resources and capable of coping with the occurrence of a plurality of failures.

In order to achieve the above object, according to one aspect of the present invention , a failure occurs , comprising a plurality of nodes and a plurality of links formed by multiplexing a plurality of wavelength resources and connecting the plurality of nodes. in an optical transmission system for protecting a transmission path from said disorder with a backup transmission path formed by occupying one of the wavelengths, a wavelength different from that occupied by the protection paths already formed, this and those teru assigning means dividing the protection paths that are newly formed through the same link as the protection paths, setting the protection path is set in advance an initial value of the wavelength on the network to share the same link And wavelength resources that are not used by other backup transmission paths and are not shared by other backup transmission paths having different initial values. A search unit that searches for a destination of the backup transmission path to be moved, and the allocation unit is unable to find a destination of the backup transmission path to be moved of the wavelength allocation as a result of the search by the search unit. For example, an optical transmission system is provided in which the wavelength assignment destination is the initial wavelength of the backup transmission path .
According to such a configuration, when a certain transmission failure occurs on the network and protection is performed, the wavelength to be shared with respect to all other backup transmission paths that share the wavelength used by the backup transmission path is reduced. Settings are moved uniformly. The wavelength at which the destination, a wavelength that is not used by yet another protection path at that time is used. If the wavelength to be moved is not left, the setting of the wavelength shared in the link is returned to the initial value (situation before a series of setting movements). If a new transmission failure occurs and the wavelength to be used competes in this situation, the protection against the new transmission failure is not performed and the result is “cannot be switched”.

In addition, all the backup transmission paths on the network are included in one Shared Protection group, and the situation in which protection can be executed / impossible depends on the order of failure occurrence. As an option, another shared protection pair is created in a specific backup transmission path, and the status of whether or not protection can be performed in the pair is not dependent on whether or not the above-mentioned shared protection is possible. In order to achieve this, it is possible to select an initial value of a wavelength shared by each backup transmission path. In other words, Shared Protection is grouped by selecting this initial value. This selection is expressed by giving an attribute indicating the initial value of the wavelength shared by the corresponding backup transmission path to each transmission path to be protected. Furthermore, as the wavelength at which to move the protection paths, still to use a wavelength that is not shared not used by other protection paths and the unequal other protection paths of the initial values of the To do. Thereby, the protection execution of a specific transmission path can be made independent of the protection execution of other transmission paths.

According to the present invention, contention for wavelength resources for protection can be avoided, and a transmission system that can cope with the occurrence of a plurality of failures can be provided.

[First Embodiment]
FIG. 1 is a system diagram showing a first embodiment of a transmission system according to the present invention. In the following description, an optical transmission system using a protection mechanism based on the Shared Protection method is targeted. The system shown in FIG. 1 has a plurality of nodes A to I connected on a mesh via optical links, and a spare transmission path (dotted line) can be provided for a transmission path (solid line) for transmitting traffic.

  In FIG. 1, attention is paid to the protection for each transmission path between nodes B to C and between nodes H to I. Between the nodes B to C, protection is executed using the backup transmission path set in the transmission band W1 between the nodes B to A to E to F to C. Protection is executed between the nodes H to I using a backup transmission path set in the transmission band W1 between the nodes H to E to F to G to I. Here, between the nodes E to F, the transmission band W1 is shared by the two backup transmission paths.

  FIG. 2 is a diagram illustrating an example of occurrence of resource contention when Shared Protection is performed in an existing system. First, when the first transmission failure (1st) occurs between the nodes B to C, protection is performed using the transmission band W1 between the nodes B to A to E to F to C. From this situation, when the second transmission failure (2nd) occurs between the nodes H to I, the system attempts to execute protection using the transmission band W1 between the nodes H to E to F to G to I. However, the transmission band W1 between the nodes E to F is already used due to the failure 1st, and a protection state cannot be performed between the nodes H to I due to a race condition.

  FIG. 3 is a diagram showing a state in which the present invention is applied to the system of FIG. In FIG. 3, when the first transmission failure (1st) occurs between the nodes B to C, protection is performed using the transmission band W1 between the nodes B to A to E to F to C as in FIG. The Then, in this embodiment, the shared band value W1 between the nodes H to E to F to G to I is changed to W2. From this state, when the second transmission failure (2nd) occurs between the nodes H to I as shown in FIG. 4, the protection passing between the nodes H to E to F to G to I uses the transmission band W2. Implemented. Therefore, the occurrence of competition as shown in FIG. 2 can be prevented.

FIG. 5 is a sequence diagram showing protection control information exchanged between the related nodes in this embodiment. In FIG. 5, when the first transmission failure (1st) is detected by the node C, “switching request” information is signaled in the order of the nodes C → F → E → A → B in order to execute protection. At that time, the node F recognizes that W1 is shared on the paths of the nodes F to E. Therefore, the node F recognizes that W1 is used by executing this protection, and another backup transmission path that shares W1 (set to W1 between the nodes H to E to F to G to I in FIG. 3). In response to this, the “transmission band movement [W2]” information, that is, a request to move the shared transmission band setting to W2 is signaled. It should be noted that the transmission band to be the destination is searched and determined in order from the next transmission band currently shared.
As described above, according to this embodiment, even when a plurality of failures occur in the network, it is possible to perform protection without causing wavelength resource competition.

[Second Embodiment]
FIG. 6 is a system diagram showing a second embodiment of the transmission system according to the present invention. 6 and 7 to 9, an operation in a situation where the setting change for moving the transmission band of the backup transmission path described in the first embodiment cannot be performed (the transmission band to be moved is not left). I will explain.

  In FIG. 6, attention is paid to the protection for transmission paths between nodes B to C, between H and I, and between A and J. Each transmission path includes a transmission band W1 between the nodes B to A to E to F to C, a transmission band W1 between the nodes H to E to F to G to I, and a transmission band W1 between the nodes A to E to H to J. Protection is performed using the backup transmission path set for each. In the transmission band W1 between the nodes E to F, A to E, and E to H, two backup transmission paths share the transmission band. In this network, it is assumed that the transmission bands prepared (available) in advance for the backup transmission path are W1 and W2.

  As shown in FIG. 7, when the first transmission failure (1st) occurs between the nodes B to C, the protection is performed using the transmission band W1 between the nodes B to A to E to F to C. Then, in this embodiment, the shared band value W1 between the nodes H to E to F to G to I and the shared band value W1 between the nodes A to E to H to J are all changed to W2. . From this state, when the second transmission failure (2nd) occurs between the nodes H to I as shown in FIG. 8, the protection passing between the nodes H to E to F to G to I uses the transmission band W2. Implemented. As a result, protection can be executed without band contention.

  FIG. 9 is a sequence diagram showing protection control information exchanged between the related nodes in this embodiment. In FIG. 9, when the “switching request” information is signaled in the order of the nodes C → F → E → A → B from the node C that has detected the first transmission failure (1st), the node F passes the paths of the nodes F to E The node E recognizes that W1 is shared above, and recognizes that W1 is shared on the paths of the nodes E to A.

  As a result of this recognition, the node F recognizes that W1 is used for protection execution between the nodes B to C, and another backup transmission path sharing the W1 (between the nodes H to E to F to G in FIG. 7). "Transmission band shift [W2]" information is signaled to the W1). Node E recognizes that W1 is used to execute protection for nodes B to C, and is set to W1 between nodes A to E to H to J in FIG. ) Is signaled to “Transmission Band Shift [W2]”.

  If the second transmission failure (2nd) occurs between the nodes H to I from this state, when the “switching request” information is signaled in the order of the nodes I → G → F → E → H, the node E Recognize that W2 is shared on the H route. Node E recognizes that W2 is used for protection execution between nodes H to I, and is set to W2 between nodes A to E to H to J in FIG. ) Is signaled to “Transmission Band Movement [W1]”. In this case, as shown in FIG. 8, the node E tries to search in order from the next transmission band (W2) that is currently shared as the transmission band to be moved to, but the setting is made because there is no transmission band after W2. The initial value is returned to W1, which is a situation before a series of setting movements.

  Assume that a third transmission failure (3rd) occurs between nodes A to J from this state as shown in FIG. Then, in FIG. 9, the node J that has detected the third transmission failure (3rd) signals the “switch request” information in the order of the nodes J → H → E → A. At that time, the node E recognizes that a conflict occurs because W1 is already used on the paths of the nodes E to A. For this reason, the node E returns a “not switchable” notification to the node J via the node H, assuming that the protection between the nodes A to E cannot be executed. As a result, the links A to J are not protected in FIG.

[Third Embodiment]
7 to 10, whether or not protection can be executed depends on the order of occurrence of transmission failures. The protection for the transmission path between the nodes A to J in FIG. 7 and thereafter cannot be executed when the third transmission failure between the nodes A to J occurs as shown in FIG. Therefore, in this embodiment, a method that considers that protection against a failure in which a failure has occurred third can be executed will be described. In this embodiment, it is assumed that W1 and W2 are provided as transmission bands usable for the backup transmission path.

  As shown in curly brackets ({}) in FIG. 11, for each transmission path between nodes B to C, H to I, and A to J, the initial value of the transmission band shared by the corresponding backup transmission path Grouping of Shared Protection by giving the attribute indicating. Normally, W1 is given and only one set is set, but W2 is given to the transmission path between the nodes A to J, and another set of Shared Protection is set.

  In FIG. 11, when the first transmission failure (1st) occurs between nodes B to C, “switch request” information is signaled in the order of nodes C → F → E → A → B as shown in FIG. At that time, the node F recognizes that W1 is shared on the paths of the nodes F to E. Node F recognizes that W1 is used to execute protection for nodes B to C, and is set to another backup transmission path sharing W1 (in FIG. 11, W1 between nodes H to E to F to G to I). "Transmission band shift [W2]" information is signaled to

  When node E receives the signaled “transmission band shift [W2]” information, W2 is already shared by the backup transmission path between nodes A to E to H to J on the paths of nodes E to H. Recognize Here, the initial value of the transmission band of this backup transmission path is W2, which is different from the initial value W1 of the backup transmission path that is the object of the “transmission band shift [W2]” information. Therefore, the node E signals the “transmission band movement [W1]” information to the backup transmission path between the nodes H to E to F to G to I that signaled the “transmission band movement [W2]” information. In this case, the node E tries to search in order from the next of W2 currently shared as the transmission band to be the destination, but since there is no transmission band after W2, the setting is returned to the initial value, that is, W1.

  Next, when the second transmission failure (2nd) occurs between the nodes H to I as shown in FIG. 13, the “switch request” is made in the order of the nodes I → G → F → E → H as shown in FIG. Information is signaled. At this time, since W1 has already been used on the paths of the nodes F to E, the node F recognizes that there is a conflict. Therefore, the “switching impossible” notification is returned to the node I via the node G because the protection between the nodes H to I cannot be executed.

As shown in FIG. 14, when the third transmission failure (3rd) occurs between nodes A to J, “switch request” information is signaled in the order of nodes J → H → E → A as shown in FIG. The At that time, the nodes A, E, H, and J recognize that there is no transmission band shared on the route, and the protection is executed as it is.
As described above, according to this embodiment, even when a plurality of failures occur in the network, it is possible to perform protection without causing wavelength resource competition.

[Fourth Embodiment]
In this embodiment, an operation when W1, W2, and W3 are provided as transmission bands usable for the backup transmission path in the network having the topology of FIG. 11 will be described. In FIG. 15, when the first transmission failure (1st) occurs between nodes B to C, “switch request” information is signaled in the order of nodes C → F → E → A → B as shown in FIG. At this time, the node F recognizes that W1 is shared on the paths of the nodes F to E. Node F recognizes that W1 is used to execute protection for nodes B to C, and is set to another backup transmission path sharing W1 (in FIG. 15, W1 between nodes H to E to F to G to I). "Transmission band shift [W2]" information is signaled to

  When node E receives the signaled “transmission band shift [W2]” information, W2 is already shared by the backup transmission path between nodes A to E to H to J on the paths of nodes E to H. Recognize In addition, the initial value of the transmission band of this backup transmission path is W2, which is different from the initial value W1 of the backup transmission path that is the target of the “transmission band shift [W2]” information. Therefore, the node E signals the “transmission band shift [W3]” information to the backup transmission path between the nodes H to E to F to G to I that signaled the “transmission band shift [W2]” information. In this case, the node E searches in order from the next of the currently shared W2 as the transmission band to be moved to find W3.

  In this state, as shown in FIG. 17, when the second transmission failure (2nd) occurs between the nodes H to I, as shown in FIG. 16, “switch request is made in the order of the nodes I → G → F → E → H. Information is signaled. At that time, the nodes H, E, F, G, and I recognize that there is no transmission band shared on the route, and the protection is executed as it is.

  Further, when the third transmission failure (3rd) occurs between the nodes A to J, the “switching request” information is signaled in the order of the nodes J → H → E → A as shown in FIG. At that time, the nodes A, E, H, and J recognize that there is no transmission band shared on the route, so that the protection is executed as it is. In this way, protection is performed without any traffic contention for any failure.

As described above, according to this embodiment, even when a plurality of failures occur in the network, it is possible to perform protection without causing wavelength resource competition. Thus, according to the first to fourth embodiments, it becomes possible to avoid contention for wavelength resources for protection, and it is possible to provide a transmission system that can cope with the occurrence of a plurality of failures.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a system diagram showing a first embodiment of a transmission system according to the present invention. The figure which shows the example of generation | occurrence | production of the resource conflict at the time of implementing Shared Protection in the existing system. The figure which shows the state which applied this invention in the system of FIG. The figure which shows the state from which the competition of the band was prevented from the state of FIG. The sequence diagram which shows the protection control information exchanged between each related node in 1st Embodiment of this invention. The system diagram which shows 2nd Embodiment of the transmission system concerning this invention. The figure which shows the state which applied this invention in the system of FIG. The figure which shows the state from which the competition of the band was prevented from the state of FIG. The sequence diagram which shows the protection control information exchanged between each related node in 2nd Embodiment of this invention. FIG. 8 is a diagram illustrating a state in which a third transmission failure (3rd) occurs from the state of FIG. 7. The system diagram which shows 3rd Embodiment of the transmission system concerning this invention. The sequence diagram which shows the protection control information exchanged between each related node in 3rd Embodiment of this invention. FIG. 12 is a diagram illustrating a state where a second transmission failure (2nd) has occurred from the state of FIG. 11. FIG. 14 is a diagram illustrating a state where a third transmission failure (3rd) has occurred from the state of FIG. 13. The system diagram which shows 4th Embodiment of the transmission system concerning this invention. The sequence diagram which shows the protection control information exchanged between each related node in 4th Embodiment of this invention. The figure which shows the state by which protection was implemented without generation | occurrence | production of competition in 4th Embodiment of this invention.

Explanation of symbols

  A to J ... Node

Claims (3)

A plurality of nodes and a plurality of links formed by multiplexing a plurality of wavelength resources and connecting the plurality of nodes, and a spare transmission path formed by occupying any wavelength when a failure occurs; In an optical transmission system that uses a transmission path to protect against the failure ,
A wavelength different from that occupied by the protection paths that have already been formed, and those Teru assigning means dividing the protection paths that are newly formed through the same link as the protection path,
Setting means for presetting an initial value of the wavelength on the network shared by the backup transmission path in the same link;
Search for searching for a wavelength resource that is not used by another backup transmission path and is not shared by another backup transmission path having a different initial value as a destination of the backup transmission path that is the target of wavelength allocation movement. Means,
The assigning means includes
As a result of the search by the search means, if the movement destination of the backup transmission path that is the movement target of the wavelength assignment is not found, the movement destination of the wavelength assignment is set as the initial value of the wavelength of the backup transmission path. Optical transmission system. A node that recognizes the existence of another backup transmission path that shares the wavelength of the newly formed backup transmission path in the same link sends transmission band movement information to the node that is the movement target of the wavelength allocation. Further comprising a sending means for
When the search means receives transmission band movement information from another node, the destination wavelength indicated by the transmission band movement information is not used by another backup transmission path, and the initial value is not equal. if in result set is a wavelength that is not shared by other protection paths, according to claim 1, characterized in that updating the transmission band movement information and search for a wavelength that matches this condition Optical transmission system. When there is already another backup transmission path that uses the wavelength when the backup transmission path uses the wavelength resource on the network, the node that has recognized the existence of the backup transmission path sends a non-switchable notification to the other node. The optical transmission system according to claim 1, wherein use of a new wavelength is stopped.

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