JP2013026803A - Node device, communication system, and failure switching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent interruption of communications when a plurality of active communication paths have gone wrong by using a small capacity standby communication path, but without increasing the power consumption of a device which switches communication paths.SOLUTION: A node device comprises: a large grain switching function unit; a small grain switching function unit; a filter function unit which reduces the band of high order communication paths between the large grain switching function unit and the small grain switching function unit; a multiplexing/separation function unit between bypass high order communication paths connected to the small grain switching function unit; and a control function unit. When the control function unit detects failure in a communication path between the node device and another node device, the filter function unit reduces the band of signals on a single or a plurality of high order communication paths corresponding to the faulty communication path, and the small grain switching function unit connects the band reduced signal to the bypass high order communication path, whereby the communication paths are switched over.

Description

  The present invention relates to a failure recovery technique for a communication network that transfers traffic through a communication path between bases, and in particular, with a small spare (detour) communication path capacity, while avoiding an increase in device scale, The present invention relates to a technique for preventing communication interruption of a communication path and realizing high reliability of a communication network.

  A backbone communication network, which is the backbone of a large-scale communication network, is configured by connecting node devices with optical fibers or the like. The backbone communication network receives a client signal through a UNI (User Network Interface) that is an interface between the node device and the client device, and the service quality (service class) in which traffic of various signal types of the client device is specified by the client. ) Provides a function for transferring between multiple sites. Also, in some cases, at the entrance of the backbone communication network, the signals of multiple clients can be transferred to a higher capacity by using various multiplexing methods such as wavelength multiplexing, time division multiplexing, and statistical multiplexing of variable length asynchronous packet signals. Provides a function of multiplexing and transferring to the next communication path. Traffic transferred in such a backbone communication network continues to increase, and is expected to reach several T to several hundred Tbps (for example, 80 Gbps of 100 Gbps × 80 waves in a single WDM system).

  In recent years, in order to efficiently transfer the traffic of the backbone communication network, optical line switching, in which communication is performed by switching the wavelength-multiplexed wavelength by WDM (Wavelength Division Multiplexing) with an optical cross-connect, etc. Packets such as TDM (Time Division Multiplexing) circuit switching specified in [Non-Patent Document 1], IETF, and MPLS-TP (Multi-Protocol Label Switching Transport Profile) [Non-Patent Document 2] specified in ITU-T A technology for performing multiplexing and switching by mounting a plurality of technologies such as base circuit switching on a node device has been studied [Non-Patent Document 3].

  In other words, processing of large-capacity traffic by high-capacity circuit switching using a method such as optical cross-connect, whose processing scale is not proportional to the transfer bandwidth, reduces node load and power consumption, and time-divides small-grain traffic The backbone communication network is efficiently constructed by multiplexing to a large capacity line with high efficiency by multiplexing or packet multiplexing.

  In a communication network such as the above-described backbone communication network, generally, an improvement in reliability is realized by allocating redundant spare resources in the communication network. However, since the degree of reliability required for the traffic to be transferred varies, if all the traffic is uniformly assigned a spare resource, excessive resources are provided, which is inefficient. Therefore, considering the degree of reliability (class, priority, etc.) for multiple traffic, provide resources for failure recovery as necessary, and provide excessive transfer resources for assumed services By eliminating, it is required to save resources and realize high reliability of the communication network.

  In particular, the traffic to be transferred between bases by clients of the current backbone communication network using the backbone communication network is mainly traffic by packet data that transmits data in units of packets / frames such as Ethernet. The required quality is also diversifying. For example, there are service classes that partially guarantee the transfer bandwidth such as the minimum bandwidth guarantee (the client allows the other parts to be not guaranteed). For such a service class client, there may be a case where it is necessary or not necessary to allocate a spare resource exceeding the minimum guaranteed bandwidth in which a failure has occurred in the communication network. In accordance with the diversification of client transfer requests, it is also necessary to prepare more service menus than ever before for the high reliability technology of the backbone communication network.

ITU-T Recommendation G.709 IETF RFC5921 M. Fukutoku, et.al, OFC / NFOEC 2011, NMC5 (2011). IETF RFC3630 IETF RFC3476 IETF RFC3209 IETF RFC3213 ITU-T Recommendation G.7041

  The conventional failure recovery technology in the above-described backbone communication network has the problems described below.

  In failure recovery, communication failure in the working communication path is prevented by switching the failed working communication path to a standby communication path (also called a bypass communication path). As a typical failure recovery technique in a backbone communication network, there is a protection method in which a switching device such as an optical cross connect is used to switch to a standby communication channel when a working communication channel fails. For example, there are protection in which one active communication path occupies a backup communication path such as 1: 1 protection, and backup shared protection such as 1: N protection and M: N protection.

  Among these, the backup shared protection is a method in which the backup communication path is shared by a plurality of active communication paths, and is positioned as a failure recovery method that realizes high reliability by saving resources. However, if this method is configured by a network in which communication path resources correspond to physical resources, such as an optical path network (wavelength path network), there is a problem that a plurality of clients cannot share a spare band at the same time.

  This is because the resources of the optical path network are managed in a fixed connection with physical resources such as wavelengths, so that the physical resources cannot be decomposed into a plurality of resources. For this reason, when a failure occurs in a plurality of active communication channels sharing the same standby communication channel, a spare resource can be used only in a form occupied by one of the active communication channels. There was a problem that only the working communication path could be restored and communication on other communication paths was interrupted.

  FIG. 1 shows an example corresponding to the above-described pre-shared protection as a first conventional example of a method for switching communication paths.

  In the first conventional example shown in FIG. 1, the large-capacity communication path is switched by the large granularity switching devices 1 and 2 to perform failure recovery. Here, the large-capacity communication path is a communication path of the maximum bandwidth of the communication path in the communication network, and the large granularity switching device is equal to or greater than the granularity of the maximum bandwidth of the communication path in the communication network (granularity of the large-capacity communication path). It is a device that performs switching at a granularity. The large granularity switching device corresponds to, for example, an optical cross-connect device when the large-capacity communication path is a wavelength path. The small capacity communication path is a communication path having a capacity less than that of the large capacity communication path.

  Since the large-grain switching device can switch the communication path only with the same granularity as the bandwidth of the large-capacity communication path, if the detour communication path for failure is shared by multiple active communication paths, multiple active communication paths If a simultaneous failure occurs, only one working communication path can use the detour communication path. That is, when a failure occurs in two active communication paths as shown in FIG. 1B from the normal state shown in FIG. 1A, only one active communication path is switched to a bypass communication path. Can do.

  Note that, in actual operation, such an operation may be appropriate, such as when the priority order of a plurality of failed working channels is clear, but a plurality of working channels, which are more general cases, are equivalent. If you want to handle it, it is not a suitable method.

  In order to prevent communication interruption even if a failure occurs in a plurality of working communication paths, a mechanism for sharing the bypass communication path bandwidth among the plurality of working communication paths is required. A conventional example of such a mechanism is shown in FIG. 2 as a second conventional example of a method for switching communication channels.

  In the second conventional example, the large-capacity communication path is switched by the small granularity switching devices 3 and 4 to perform failure recovery. Here, the small granularity switching device is a device having a function of switching at a granularity less than the granularity of the maximum bandwidth of traffic that can be accommodated in the communication path in the communication network (granularity of the large capacity communication path), for example, A device that performs processing in units of frames / packets, such as ATM and MPLS-TP, is applicable.

  When a small granularity switching device is used, when a failure occurs in multiple active channels, the bandwidth of the detour communication channel is shared by multiple active channels by narrowing down the communication band of the active channel be able to. That is, when a failure occurs in the two active communication paths as shown in FIG. 2B from the normal state shown in FIG. 2A, the current communication paths for two lines are bypassed by narrowing the bandwidth. It can be switched to a communication path.

  It should be noted that a multi-layer communication network composed of a plurality of layers (tiers) includes both a small granularity switching device and a large granularity switching device, and can be configured to enable switching of communication paths in either case. In this case, either the communication path is switched using the large granularity switching device or the communication path is switched using the small granularity switching device, and the communication path is switched using the large granularity switching device. The case is the same as that of the first conventional example shown in FIG. 1, and the case of switching the communication path using the small granularity switching device is the same as the second conventional example shown in FIG.

  As described above, the second conventional example shown in FIG. 2 has an advantage that the band of the bypass communication path can be shared by a plurality of working communication paths, and communication interruption can be prevented.

  However, in the current technology, when the communication path switching is performed by a small granularity switching device that performs processing in units of frames as in the second conventional example, the processing amount of the device increases in proportion to the increase in the line bandwidth. In the case of a large capacity, there is a problem that power consumption and device scale increase. This causes a problem in scalability particularly to cope with the recent increase in traffic.

  The present invention has been made in view of the above problem, and in a communication network that performs failure recovery of communication on the working communication path by switching to the backup communication path, a spare communication path with a small capacity is used, and It is an object of the present invention to provide a technique capable of preventing communication interruption at the time of failure of a plurality of active communication paths without increasing the power consumption and the amount of equipment of a device for switching communication paths.

In order to solve the above-described problems, the present invention is connected to a client device via a low-order communication path and to other node devices via a high-order communication path that accommodates the low-order communication path. A node device,
A large granularity switching function unit equipped with a large granularity communication path switching function;
Small granularity switching function unit with small granularity channel switching function,
A filter function unit that reduces a bandwidth of a high-order communication path between the large granularity switching function unit and the small granularity switching function unit;
Signal multiplexing processing when transmitting a signal to a detour high-order communication path connected to the small-grain switching function section, and signal separation processing when the small-grain switching function section receives a signal from the detour high-order communication path A multiplexing / demultiplexing function unit to perform,
A control function unit including a failure detection function, a switching command function for the large granularity switching function unit and the small granularity switching function unit, and a filter operation setting function for the filter function unit,
When the control function unit detects a failure in the communication path between the node device and the other node device, the filter function unit detects one or more higher-order communication corresponding to the failed communication path. Configured as a node device that reduces a bandwidth of a signal of a path, and the small granularity switching function unit switches the communication path by connecting the signal with the reduced bandwidth to the bypass high-order communication path Is done.

  The control function unit has a function of identifying the priority of the communication channel, and when a communication channel failure is detected, the bandwidth value to be reduced by the fill multifunction unit is changed according to the priority of the communication channel. You may comprise.

  Further, the control function unit has a function of identifying a failure state of a communication channel or a priority of a higher-order communication channel in which a failure is detected, and depending on the failure state of the communication channel or the priority, You may comprise so that it may determine which of the channel switching by a particle size switching function part and the channel switching by the said small particle size switching function part is implemented.

  The control function unit may be configured to change a band value to be reduced by the fill multi-function unit according to a failure state of the communication channel when a communication channel failure is detected.

  In the node device, the number of large granularity switching function units may be plural, and the plurality of large granularity switching function units may be configured to share the small granularity switching function unit.

  Further, for example, the large granularity switching function unit is configured by an optical cross-connect device and the small granularity switching function unit is configured by a TDM cross-connect device, or the small granularity switching function unit and the filter function unit are packetized. You may make it comprise with a switch.

  The present invention can also be configured as a communication system in which the above-described node devices are connected by optical fibers.

Furthermore, the present invention is a failure that is executed by a node device that is connected to a client device via a low-order communication path and that is connected to another node device via a high-order communication path that accommodates the low-order communication path. A switching method,
The node device includes a large granularity switching function unit having a large granularity channel switching function, a small granularity switching function unit having a small granularity channel switching function, the large granularity switching function unit, and the small granularity switching unit. A filter function unit that reduces a bandwidth of a high-order communication path with the function unit, and the failure switching method includes:
Determining a priority of a higher order communication path corresponding to a failure state of the communication path or a communication path in which the failure is detected when a communication path failure is detected;
Determining which of the communication path switching by the large granularity switching function section and the communication path switching by the small granularity switching function section is to be performed according to the failure state of the communication path or the priority; ,
When the communication path is switched by the small granularity switching function section, the filter function section reduces the band of the signal of one or a plurality of higher order communication paths corresponding to the failed communication path, and the small granularity switching function The unit may comprise a step of switching the communication path by connecting the signal with the reduced bandwidth to the bypass higher-order communication path.

  According to the present invention, in a communication network that performs failure recovery of a communication on an active communication path by switching to a backup communication path, consumption of a device that uses a spare communication path with a small capacity and switches the communication path It is possible to provide a technique that can prevent communication interruption at the time of failure of a plurality of active communication paths without increasing the power and the amount of equipment.

It is a figure for demonstrating the 1st prior art example of the system which switches a communication path. It is a figure for demonstrating the 2nd prior art example of the system which switches a communication path. It is a figure for demonstrating the outline | summary of the communication system which concerns on embodiment of this invention. It is a figure for demonstrating the outline | summary of the communication system which concerns on embodiment of this invention. It is a principle lineblock diagram of a communications system concerning an embodiment of the invention. It is a block diagram (normal state) of the communication system which concerns on 1st Embodiment. It is a block diagram (failure switching state) of the communication system which concerns on 1st Embodiment. It is a figure which shows the example of the information which a control function part memorize | stores. It is a flowchart which shows the switching procedure in case a high priority wavelength path fails. It is a flowchart which shows the switching procedure in case a low priority wavelength path fails. It is a figure which shows the example of the table which a control function part hold | maintains. It is a figure which shows the example of the table which a control function part hold | maintains. It is a figure which shows the example of a failure state transition. It is a figure which shows the example of the table which a control function part hold | maintains. It is a figure which shows the example of the table which a control function part hold | maintains. It is a block diagram of the communication system which concerns on 4th Embodiment. It is a block diagram of the communication system which concerns on 5th Embodiment. It is a block diagram of the communication system which concerns on 6th Embodiment. In a 6th embodiment, it is a figure showing a normal state without a failure. In a 6th embodiment, it is a figure showing a state at the time of failure. It is a block diagram of the communication system which concerns on 7th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

(Outline of the embodiment)
<System overview>
FIG. 3 is a diagram for explaining the outline of the communication system according to the embodiment of the present invention. As shown in FIG. 3, the communication system according to the embodiment of the present invention is configured by connecting a node device 50 and a node device 60 to a communication network 70.

  Each node device includes both a small granularity switching device (52, 62) and a large granularity switching device (51, 61). As shown in FIG. 3, the large capacity communication path is connected to the communication network 70 through the large granularity switching devices (51, 61). In the normal state (FIG. 3A), the large capacity communication path is connected to the small granularity switching apparatus. (52, 62) is not passed. Only when a failure occurs (FIG. 3 (b)), the small granularity switching device (52, 62) is made to pass traffic, and the small granularity switching device (52, 62) is used in a small band. Has been. Since the time during which the communication path is in the failure state is significantly shorter than the time in the normal state, according to the technology of the present invention, the time for using the small granularity switching device (52, 62) is greatly reduced and power consumption is reduced. Can be suppressed.

  Further, as shown in FIG. 4, a plurality of large capacity channel groups (that is, a plurality of large granularity switching devices 51 and 61) in the communication network are used by utilizing the short time for using the small granularity switching devices. A configuration in which the small particle size switching devices 52 and 62 are shared can also be adopted. Thereby, the scale of the small granularity switching device required for the entire communication network can be reduced.

  On the other hand, by passing the traffic through the small granularity switching device only in the case of a failure, and sharing the bandwidth with the small granularity switching device by the multiplexing / demultiplexing function, the bandwidth of the detour communication path is allocated to multiple active communication paths. The detour communication path can be used simultaneously with a plurality of working communication paths.

<Principle configuration of node device>
FIG. 5 shows a principle configuration diagram of a communication system according to the embodiment of the present invention. FIG. 5 shows two opposing node devices 10 and 20 connected to a communication network 30 (which may be called a transfer network). As an example, FIG. 5 shows a failure state.

  Since the two node devices 10 and 20 have the same function, the description of the functional configuration below will focus on the node device 10.

  As shown in FIG. 5, the node device 10 according to the embodiment of the present invention includes a large granularity switching function unit 11, a small granularity switching function unit 12, a band filter function unit 13, a multiplexing / demultiplexing function unit 14, and a control function. Part 15. The functions of the following functional units will be described. In addition, the function demonstrated below is a function which also has a corresponding function part in other embodiment fundamentally.

  The large granularity switching function unit 11 is connected to a higher order communication path and has a function of switching the higher order communication path in units of large capacity switching. As this function, for example, a switching function employing a circuit switching method suitable for a large-capacity communication path is applied.

  Here, the high-order communication path is a communication path having the same granularity as the maximum bandwidth of the physical IF of the communication network. In the present embodiment, for example, an OTN network (ITU-T Recommendation G. 709) is assumed as a communication network, and in this case, an OTU (Optical-channel Transport Unit) IF corresponds to the physical IF. Of course, the communication network to which the present invention can be applied is not limited to the OTN network.

  The small granularity switching function unit 12 has a function of switching a low-order communication path in units of small capacity switching. The small granularity switching function unit 12 is connected to the band filter function unit 13 and is also connected to a higher-order communication path (a detour higher-order communication path) via the multiplexing / demultiplexing function unit 14. As the switching function, for example, a switching function that adopts a packet switching method suitable for switching a small-capacity communication path is applied.

  Here, the low-order communication path is a communication path that can be multiplexed (including 1: 1) or mapped to a high-order communication path.

  The band filter function unit 13 is provided between the large granularity switching function unit 11 and the small granularity switching function unit 12, and traffic of a low-order communication path connected from the large granularity switching function unit 11 to the small granularity switching function unit 12. Is selected by a method designated by the control function unit 15 and the traffic is filtered to a band designated by the control function unit 15. Examples of the bandwidth designated by the control function unit 15 include a bandwidth value of the minimum guaranteed bandwidth.

  The multiplexing / separation function unit 14 has a function of multiplexing traffic of a plurality of low-order communication paths to a high-order communication path and a function of separating low-order communication paths multiplexed in the high-order communication path.

  The control function unit 15 has a function of designating an input point and an output point to the switching device of the large granularity switching function unit 11 and the small granularity switching function unit 12 and giving a switching command. Here, the input point / output point is a physical / logical label such as a wavelength of an input / output IF, a time slot, a VLAN ID used in an Ethernet frame, a fiber port, or the like, which is a unit of switching control. In addition, the control function unit 15 includes a function for determining the traffic to be filtered and a band after filtering for the band filter function unit 13.

  The control function unit 15 also includes a failure detection function of a higher-order communication path connected to a passing lower-order communication path or an interrupt detection function of another communication path, and a function of grasping a failure state for each communication path. . Here, the interruption of the other communication path means that the other communication path deprives and uses the resource of the communication path that has been using the resource. The control function unit 15 further uses a failure detection or communication path interrupt as a trigger to determine the switching state of the large granularity switching function unit 11, the switching state of the small granularity switching function unit 12, and the traffic determination method of the band filter function unit 13. It has a function of sending a band value change command after filtering. It also has a function of exchanging control information with a neighboring node through a control link.

  Further, the node device 10 includes IFs for two types of communication paths, a low-order communication path and a high-order communication path. The client device that is a connection source to the communication network includes an IF for a low-order communication path, and an IF for a high-order communication path for an internal transfer network. The low-order communication path can be a communication path switching unit of the small granularity switching function unit 12, and the high-order communication path can be a communication path switching unit of the large granularity switching function unit 11, and the connection state of each switching function unit is set. Thus, a communication path can be dynamically generated between nodes.

  Further, the node device 10 determines whether the connection unit (port, IF, etc.) of the large granularity switching function unit 11 is connected to the small granularity switching function unit 12 or directly connected to the higher order communication path. A function of storing and managing the connection state for each connection unit (port, IF, etc.) is provided. This function is provided in the control function unit 15, for example.

  In the node apparatus 10 according to the present embodiment, in a normal state where no failure or communication path interrupt has been detected and switching to a detour communication path or the like has not been performed, a large capacity communication path has a large granularity switching function unit 11. Set the communication path so that it passes through. In this way, normally, the small granularity switching function unit 12 is not subjected to a load on the large capacity communication path. On the other hand, when a failure or a communication path interruption is detected, a plurality of affected communication paths are reduced and multiplexed, and the small granularity switching function unit 12 is connected to the detour higher-order communication path. In this way, the small granularity switching function unit 12 that is easy to cooperate with the bandwidth reduction function, the multiplexing function, etc. is utilized when using the detour communication path with a reduced bandwidth.

<Example of communication path switching processing procedure when a failure occurs>
Next, an example of a communication path switching process from the working communication path to the detour communication path when a failure occurs will be described. A specific example of each step described below will be described in detail in a first embodiment described later.

  The detour communication path used as the communication path after switching here is a CLI (Command Line Interface) input by the operator (when the control function section includes a CLI), or the control function section 15 is IETF RFC3630 [Non-Patent Document 4]. ] Is determined by referring to the network resource information collected by a protocol such as OSPF-TE (Open Shortest Path First) specified in the above, and set in advance by a route search algorithm such as the Dijkstra method. Alternatively, after the failure occurs, the control function unit 15 may search and calculate a route that does not overlap the failure path in the same manner. In the present invention, the route search method is not limited to a specific method, and the present invention does not depend on the route calculation method. Here, the CLI is a human interface that provides an operator's operation function by inputting a command on a text basis. CLI input means that an operator inputs a command (command) expected by the CLI using a keyboard or the like.

  Step 100) The control function unit 15 detects a failure in the higher order communication path or the lower order communication path. In the case of a failure in the higher order communication path, the accommodated lower order communication path is specified. Further, the failure in the low-order communication path here means a failure in a portion that can be relieved by switching according to the present embodiment, such as a failure in a portion mapped (accommodated) in the high-order communication path. The failure of the higher order communication path includes the failure of the link (optical fiber) that accommodates the higher order communication path.

  Step 200) The control function unit 15 (25) calculates a switching setting for switching the failed communication path to the detour route (or a value set in advance can be used), and the starting point of the detour communication path And a switching command for switching to a detour route to the large granularity switching function units 11 and 21 and the small granularity switching function units 12 and 22 at the end point. At the same time, the band filter function unit 13 (23) determines the band of each communication channel based on the number of communication channels passing through the small granularity switching function units 12 and 22 and the band of the high-order communication channel for the bypass route. The method for specifying is specified, the band after filtering is determined for each communication path, and the band filter function unit 13 (23) is notified. The multiplexing / demultiplexing setting of the multiplexing / demultiplexing function unit 14 (24) based on the number of communication paths passing through the small granularity switching function unit 12 (22) and the bandwidth of the higher-order communication path for the detour route, the higher-order communication path The identification information of each low-order communication channel that is multiplexed is determined and notified to the multiplexing / demultiplexing function unit 14 (24). Further, the identification information set in the lower order communication path and the lower order communication path association information are transmitted to the control function unit 25 of the receiving side node device 20 through the control link.

  Step 300) The large granularity switching function unit 11 (21) and the small granularity switching function unit 12 (22) that have received the switching command from the control function unit 15 (25) perform switching setting according to the switching command.

  Step 400) Upon receiving the band filter setting command from the control function unit 15 (25), the band filter function unit 13 (23) performs the filter setting according to the contents.

  Step 500) Upon receiving the multiplexing / demultiplexing setting command from the control function unit 15 (25), the multiplexing / demultiplexing function unit 14 (24) performs multiplexing setting from the lower order communication path to the higher order communication path on the transmission side according to the information. On the receiving side, a separate setting from a higher order communication path to a lower order communication path is performed. When multiplexing, identification information of each low-order communication path multiplexed on the high-order communication path is given by resource information such as a label, time slot / wavelength, and the like.

  On the separation side, the communication path accommodated in the high-order communication path is separated based on the received identification information set in the low-order communication path and the correspondence information of the low-order communication path, and is output as the low-order communication path.

  By performing the above-described procedure using the node configuration described above, a communication path failure switching function capable of ensuring a small device scale and reliability can be realized. Note that the order of Step 300 to Step 500 in the above procedure is an example, and the order is not limited to this, and the order may be changed.

(First embodiment)
Next, a first embodiment, which is a more specific example of the technology according to the present invention, will be described.

  6 and 7 show a communication system according to the first embodiment. The communication system includes two opposing node devices 100 and 200 connected to the communication network 300. FIG. 6 shows a normal state where failure switching is not performed, and FIG. 7 shows a state after failure switching is performed.

  As shown in FIG. 6, in a state where no switching has occurred, a small granularity switching function unit (in this embodiment, an ODU cross-connect device) that is inefficient for large-capacity traffic is not applied. As shown in FIG. 7, when switching is necessary due to a failure or communication path interruption (which may be collectively referred to as “failure”), the band is filtered and the small granularity switching function unit is switched. Applies to communication. Hereinafter, each function of the node device according to the first embodiment will be described. Since the two node devices have the same function, the node device 100 will be mainly described.

  As shown in FIGS. 6 and 7, the node device 100 according to the first embodiment includes an optical cross-connect device 101 as a large granularity switching function unit, an ODU cross-connect device 102 as a small granularity switching function unit, and a bandpass filter. A function unit 103, a multiplexing / demultiplexing function unit 104, and a control function unit 105 are included.

  An optical cross-connect device 101 as a large-grain switching function unit is a device that performs switching of a wavelength path (corresponding to the above-described higher-order communication path) that is one form of a communication path without using electrical processing. Further, a fiber cross-connect device may be used instead of the optical cross-connect device 101 as the large granularity switching function unit. The fiber cross-connect device is a device that switches between an input fiber port and an output fiber port.

  The ODU cross-connect device 102 as a small granularity switching function unit is a device having an ODU (Optical Data Unit) path switching function, and a device having a function of switching an ODU connection defined by ITU-T G.709. It is. An ODU-SW that is synonymous with the ODU cross-connect device may be used. The ODU-SW is a device having a function of switching an ODU signal defined by G.709.

  The band filter function unit 103 is a band filter circuit having a traffic policing function. Here, the policing function is a function for monitoring the inflow of a band exceeding a specified value and classifying or discarding traffic. The band filter circuit is mounted on a processing circuit such as an LSI or FPGA, for example.

  The multiplexing / demultiplexing function unit 104 is a device that realizes multiplexing of an ODU path to an OTU (Optical Transfer Unit) and separation of an ODU path multiplexed in the OTU path.

  The control function unit 105 in the present embodiment is realized by installing control software or firmware in a computer. In this embodiment, an Ethernet cable is used as the control link.

  In addition, a Tributary IF that is an IF (Interface) that receives a signal format of a client signal is mounted on the communication network 300 side of the optical cross-connect device 101. For example, a cross-connect port, an optical fiber connector, and a tributary IF are configured.

  The Tributary IF is connected to the ODU cross-connect device 102 (small granularity switching function unit), and is directly connected to the Trunk IF (the long distance on the backbone network side included in the node device 100 without going through the ODU cross-connect device 102). Some of them are connected to a wavelength path (using an OTU as a wavelength path signal) that is a higher-order path (higher-order communication path) via the Trunk IF. The control function unit 105 stores information about which Tributary IF belongs to this, and information on the signal format and bit rate of each Tributary IF in a storage unit such as a memory. An example of information stored in the control function unit 105 is shown in FIG.

Here, the IF signal format means the type of communication standard of the signal transmitted by the IF. For example, Ethernet IF is an Ethernet signal. When the large granularity switching function unit and the small granularity switching function unit are realized in the same device, the large granularity switching function unit and the small granularity switching function unit can be connected by bus, in which case, FIG. Original formats other than the standard signal formats shown in the table can also be used.
In this example, it is assumed that the IF speed of the client device connected to the node device of this embodiment is 100 Gbps, and the speed of the Tributary IF and the Trunk IF included in the node device of this embodiment is also 100 Gbps.

  The low-order path, which is a low-order communication path in the present embodiment, starts from the IF (described as CL-IF) of the client apparatus connected to the node apparatus 100 of the present embodiment, and is the opposite client apparatus. The IF is the end point. When passing through the low-order path from the start point to the end point, the following processing is performed on the traffic transmitted from the client device and received by the node device 100.

A signal transmitted from the client device is received by a tributary IF arranged so as to be connected to a port of the optical cross-connect device 101 (large granularity switching function unit) in the node device 100. The received client signal is converted into an ODU signal by a signal mapping function such as GFP (Generic Framing Procedure) [Non-Patent Document 8] and (Generic Mapping Procedure) [Non-Patent Document 1] provided in the IF. The ODU signal is converted into a high-order path OTU format by the Trunk IF, and transmitted to the Trunk IF of the opposite node device 200 by the Trunk IF. The Trunk IF that performs such processing includes a demultiplexing function that demultiplexes ODU frames and an OTN framer circuit that is a function of converting a signal format.
Here, the low-order path ODU format is a format defined by ITU-T G.709, such as ODU 0-4, ODU flex, and the high-order path OTU format is, for example, OTU 1-4, etc. This is a format defined by ITU-T G.709. When processing is possible only with an optical device, there is a case where conversion on the logical definition can be performed without format conversion by electrical processing. Here, a high-order path that is a higher-order communication path means a communication path that can accommodate a lower-order path.

  The traffic received by the opposite device 200 is converted to an ODU signal by the Trunk IF, further converted to the signal format of the client IF by the Tributary IF, and transmitted to the client device at the end point.

  As described above, the Tributary IF connected to the optical cross-connect device 101 (large granularity switching function unit) is the IF connected to the higher-order path without passing through the ODU cross-connect device 102 (small granularity switching function unit). And an IF connected to the ODU cross-connect device 102 (small granularity switching function unit). When the path is opened or in a normal state where no failure has occurred, the control function unit 105 identifies the location of the Tributary IF, and the low-order path does not pass through the ODU cross-connect device 102 (small granularity switching function unit). The connection state of the optical cross-connect device 101 (large granularity switching function unit) is set so as to be connected to the Tributary IF connected to the Trunk IF directly connected to the higher-order path. Here, identifying the location of the Tributary IF means that the connection state between the port of the optical cross-connect device 101 and the Tributary IF (which port and which Tributary IF is connected) is determined.

  Further, when the control function unit 105 first sets a low-order communication path (low-order path) and a corresponding higher-order communication path (high-order path), the control function unit 105 identifies and stores class information of each communication path (path). To do.

  In the above-described state, when a failure that requires switching occurs, as shown in FIG. 7, when the failed path is a high-priority wavelength path, the optical cross-connect devices 101 and 201 for all of the failed paths. By switching the switch, the detour path having the same capacity as the working path is switched.

  If the failed path is a low-priority wavelength path, for some or all of the failed paths, the optical cross-connect devices 101 and 201 (small granularity switching function unit) and the ODU cross-connect devices 102 and 202 (small granularity switching) Function part) By changing the connection settings of each, the bandwidth of the higher-order path connected from the ODU cross-connect devices 102 and 202 (small granularity switching function part) (in the case of ODU, the time slot (G.709 standard terminology) Then, the Tributary Slot)) is divided and assigned to a plurality of failed low-priority paths, and switching to the higher-order path, which is a bypass path, is performed. The same applies to the node device 200 side. The ODU cross-connect devices 102 and 202 are a type of TDM cross-connect device.

  Hereinafter, operations in each of the cases where the high-priority wavelength path fails and the low-priority wavelength path fails will be described with reference to flowcharts. In the present embodiment, the higher-order communication path is a wavelength path, and the case where the wavelength path fails means that the wavelength path between the node devices is different from the case where the failure of the wavelength path between the node devices is detected. This includes the case where a failure in the accommodated lower-order path is detected. For example, a wavelength path that accommodates a low-order path (client path) with high (low) priority may be a high (low) priority wavelength path. Also, high (low) priority may be set at the wavelength path level.

  FIG. 9 is a flowchart showing a switching procedure when the high-priority wavelength path fails.

  A failure is detected by the control function unit 105 in the start node 100, and it is determined whether the detected path is a high priority wavelength path or a low priority wavelength path (step 1). That is, the priority of the failed path (failed low-order path or failed high-order path, or high-order path accommodating the failed low-order path) is determined. Here, it is determined that the wavelength path has failed and is a high-priority wavelength path, and it is determined to switch to the detour path in the optical cross-connect device 101, and the connection state for switching is determined (step) 2).

  The control function unit 105 issues a command to change the connection state of the optical cross-connect device 101 so that the client IF connected to the failed high-priority wavelength path is connected to the bypass wavelength path. (Step 3).

  The optical cross-connect device 101 changes the connection state according to the command, and the path passing through the optical cross-connect device 101 is switched (step 4). That is, the Tributary IF connected to the client IF is changed to the Tributary IF connected to the bypass wavelength path. This operation is performed for each failure path.

  The control function unit 105 notifies the control function unit 205 of the opposite node device 200 of the failure detected in the start node device 100 and the setting information for switching by a control message through the control link (step 21). Control protocols at this time include GMPLS (IETF RFC3476 [Non-Patent Document 5]) protocol group (RSVP-TE (RFC3209 [Non-Patent Document 6])), CR-LDP (RFC3213 [Non-Patent Document 7]), OSPF- TE (RFC3630) etc. is used.

  Similarly, in the opposite node device 200, the connection state of the optical cross-connect device 201 is changed, and the tributary IF connected to the client IF is changed to the tributary IF connected to the bypass wavelength path (steps 23 and 24).

  FIG. 10 is a flowchart showing a switching procedure when the low-priority wavelength path fails. Note that the order of processing in the procedure described as out of order in the flowchart of FIG. 10 is arbitrary, and FIG. 10 shows an example of the procedure.

  The control function unit 105 of the source node 100 detects a failure and determines whether the detected path is a high-priority wavelength path or a low-priority wavelength path (step 31). It is assumed that the path is determined.

  The control function unit 105 includes the ODU cross-connect device 102 and the wavelength path connected to the ODU cross-connect device 102 and the multiplexing / demultiplexing function unit 104 so that the path accommodated in the failed low-priority wavelength path is bypassed. Setting information for a command to connect to the optical cross-connect device 101 is calculated (steps 32 and 35).

It also checks the number of low-priority wavelength paths that have failed at the same time and the bandwidth of the low-order paths (also referred to as failure paths) accommodated in the respective low-priority wavelength paths. Path) and the allocation amount of the divided band to the faulty path are determined, and the band on the detour path of each faulty path is determined. (The bandwidth is smaller than the bandwidth of the working path, which is a low-order path before the failure.) (Step 32)
At this time, for the bandwidth allocated to each failed path, the minimum bandwidth guarantee amount of each client path determined in advance when the path is opened is allocated in the order of the priority of the client path determined in advance when the path is opened. Further, according to the determined band on the detour path of each faulty path, the bandpass filter amount of each path that serves as a reference for the operation of the bandpass filter function unit 103 is determined (step 34). A multiplexing method in the multiplexing / demultiplexing circuit is determined based on the bandwidth and the bandwidth of the Trunk IF that is the IF of the higher-order communication path (step 31).

For example, assume that three low-priority client paths fail (or three low-priority wavelength paths that accommodate them) fail, and the client path attribute information is as follows.
-Client path 1
> Maximum use bandwidth 100Gbps, minimum required bandwidth 40Gbps, high priority, client path 2
> Maximum bandwidth 100Gbps, minimum bandwidth 40Gbps, high priority, client path 3
> Maximum bandwidth 100 Gbps, minimum required bandwidth 30 Gbps, low priority In this case, these three client paths divide and use the bandwidth for the high-order path bandwidth 100 Gbps, which is the detour route. First, the minimum required bandwidth of 40 Gbps is allocated to client path 1 and client path 2 that have high priority. For the client path 3, after the bandwidths of the client path 1 and the client path 2 are allocated, the bandwidth remaining in the higher-order path is allocated with the required bandwidth of the client path 3 being 30 Gbps as an upper limit. (In this case, 20 Gbps is allocated.) Here, the filter amount is a band exceeding the minimum guaranteed band. The filter amount may be only a part of the band exceeding the minimum guaranteed band.

  Which switching is performed for each path priority can be managed, for example, by the control function unit 105 holding the table shown in FIG. For example, when the control function unit 105 detects a failure in a certain wavelength path, the control function unit 105 refers to the priority information of the path accommodated in the wavelength path, and the information is “1”. According to the table, it is determined that the switching is performed by the switching method with high priority.

  In addition, as described above, the bandwidth determination method at the time of low priority switching is prioritized in advance in addition to the method in which the control function unit 105 determines in consideration of the number of failed low-order paths and the high-order path bandwidth serving as a detour path. It is also possible to take a method of determining the absolute value or the ratio to the working channel band according to the degree. In this case, for example, the control function unit 105 holds the table shown in FIG. In this case, for example, when the control function unit 105 detects a failure in a certain wavelength path, it refers to the priority information of the path accommodated in the wavelength path, and the information is, for example, “N”. Based on the table of FIG. 12, it is determined that the switching is performed by the low priority switching method, and further, it is determined that the communication on the detour is performed in the bandwidth of 20% of the bandwidth of the working path.

Returning to FIG. 10, the determination items (setting method, filter setting, multiplexer / separator setting of the large granularity switching function unit and the small granularity switching function unit) of the control function unit 105 described above are the optical cross-connect device 101 and The ODU cross-connect device 102, band filter function unit 103, and multiplexing / demultiplexing function unit 104 are notified (step 37).
The information is also notified to the control function unit 205 of the opposite node device 200 through the control link, and a command to the device is transmitted (steps 51 and 52). As a control protocol at this time, a GMPLS protocol group (RSVP-TE, CR-LDP, OSPF-TE), overhead information of OTN (signal region in which management information other than the main signal is defined), or the like is used.

  The start node device 100 and the end node device 200 change the connection state of the optical cross-connect device so that the client IF connected to the failed high-priority wavelength path is connected to the detour wavelength path (step 38, 53). The band filter function units 103 and 203 change the band so as to filter or shape the specified path to the specified band (steps 39 and 54). The ODU cross-connect devices 102 and 202 change the connection state so that the designated path is connected to the designated port (tributary slot) (steps 40 and 55). The multiplexing / demultiplexing function units 104 and 204 multiplex the ODU path signal connected from the reception ODU cross-connect to the high-order path through the Trunk IF, and perform signal processing on the signal received through the Trunk IF from the wavelength path that is a high-order path Referring to low-order path identifier information (ODU Tributary slot number, sequence number written in packet or frame, etc.) given to the Connect (steps 41 and 56).

(Second Embodiment)
A wavelength path is generally configured by connecting a plurality of links. When a wavelength path failure occurs, a plurality of links may fail. Therefore, in this embodiment, the switching of the low-priority wavelength path described in the first embodiment is performed in the case where a multiple failure in which two or more links continuously fail in the communication network 300 occurs. Applies to failure switching for the second failure after the eye failure.

  The control function unit 105 (205) has a function of grasping whether it is a single failure or multiple failures, as shown in FIG. 13, manages two or more stages of failure state transition, and in the case of each failure state, Which switching method in the first embodiment is applied is preset. An example of setting information (held by the control function unit 105) in that case is shown in FIG.

  As shown in FIG. 14, when the failure state is one stage (single failure), the processing for the high priority wavelength path of the first embodiment is performed, and when the failure state is two or more stages, the first implementation is performed. The low-priority wavelength path of the form is processed.

  It is also possible to take a method in which the absolute value or the ratio to the working channel band is determined in advance according to the failure state.

  In this case, the control function unit 105 (205) holds the table shown in FIG. 15, for example, and refers to the table to determine the switching method according to the failure state. In this case, for example, when the control function unit 105 detects a failure of a certain wavelength path, the control function unit 105 grasps the failure state of the failure. If the failure state is, for example, “N”, it is determined from the table in FIG. 15 that switching is performed by the low priority switching method, and further, communication on the detour is performed in a bandwidth of 20% of the bandwidth of the working path. Decide to do.

  When multiple failures occur in a high-order communication path (high-order path), the resources of the communication network are more insufficient than when a single failure occurs. According to the present embodiment, when such a state occurs, the switching process for the low-priority wavelength path of the first embodiment is performed, and the band is divided and used between the low-order paths. Connectivity can be ensured for more low-order communication paths within a certain resource range, and the survivability of the communication network can be improved.

(Third embodiment)
The switching operations described in the first and second embodiments are triggered by a communication channel failure, but the node devices 100 and 200 have a high-priority communication channel interrupt function (for example, specified by RSVP-TE). Switching operation described in the first and second embodiments can be performed by the interrupt function of the high-priority communication path. Here, the interrupt function of the high-priority communication path means a function that the high-priority communication path takes and uses the low-priority communication path. That is, when the interrupt function of the high priority wavelength path is used as a trigger, the failure occurrence in the first and second embodiments is operated as an interruption occurrence. In the embodiment of the present invention, when an interrupt is received, the same operation as in the case of a failure is performed, so that “failure” may be interpreted to include “interrupt”.

(Fourth embodiment)
The optical cross-connect devices 110 and 210 may be arranged between the start point node 100 and the end point node 200 that are node devices according to the first to third embodiments to configure a communication system. A configuration example in this case is shown in FIG. 16 as a fourth embodiment.

  Specifically, the optical cross-connect devices 110 and 210 here are optical switches such as MEMS (Micro Electro Mechanical Systems) and WSS (Wavelength selective switch), AWG (Arrayed Waveguide Grating), wavelength interleaver, and optical coupler. , And WSS (WSS can be used not only as a cross-connect function but also as a multiplexing / demultiplexing function). In the configuration of FIG. 16, WSS is used for each of the optical switch and the wavelength multiplexer / demultiplexer.

  In this configuration, both the wavelength path connected to the ODU cross-connect devices 102 and 202 and the wavelength path not connected to the ODU cross-connect devices 102 and 202 can be multiplexed on the same optical fiber. As a result, a communication network using the technology of the invention can be configured with fewer optical fibers, a large-scale network can be constructed more efficiently, and the problems addressed by the invention can be more efficiently solved even in a large-scale network. .

  In this embodiment, an optical switching device such as an WSS in which an optical cross-connect function and a wavelength multiplexing function are integrated can be applied. The WSS can also be used for the optical SW (optical cross-connect devices 101 and 201) connected to the client IF. Further, instead of WSS, a configuration combining optical SW and AWG such as MEMS or PLC (Planer Lightwave Circuit) -SW-based matrix-SW may be adopted.

(Fifth embodiment)
The node apparatus may be configured by replacing the ODU cross-connect apparatuses 102 and 202 of the node apparatus in the first to fourth embodiments with a packet SW (111, 211) such as an MPLS-TP switch. A configuration example in this case is shown in FIG.

  In addition, when using packet SW, the filter function is realized by utilizing the best effort packet multiplexing function of packet SW, in addition to the small granularity switching function unit, realizing the filter function unit, and switching the filter function unit and small granularity. Both functional units can be realized simultaneously by the packets SW111 and 211. Here, the best-effort packet multiplexing function of the packets SW111 and 211 uses an IP packet or an Ethernet packet for which the multiplexed communication path does not necessarily guarantee a bandwidth before being multiplexed after being multiplexed. Multiplex method. The specific operation using the best effort packet multiplexing function of the packets SW111 and 211 as the multiplexing / demultiplexing function unit is the same as the operation of the multiplexing / demultiplexing function unit of the first to fourth embodiments. .

(Sixth embodiment)
In this embodiment, as shown in FIG. 18, the node devices in the first to fifth embodiments are connected in an optical fiber in a ring shape or mesh shape, and a large granularity switching function and a small granularity switching function Are used by switching them according to the failure status of the communication channel, and a communication system having high failure resistance is constructed within a certain facility resource range.

  Here, as a specific example according to the situation, when there is no failure, communication is performed on the communication channel set using the large granularity switching function, and when a failure occurs, the small granularity communication channel function is used. And communicate. Even when connected in a ring shape or a mesh shape, each node device can have the same device configuration as the configuration of FIG. 5, FIG. 16, FIG.

  19A and 19B show a configuration example in which the node devices according to the embodiment of the present invention are connected in a ring shape with four nodes (node # 1 to node # 4) and optical fibers. 19A and 19B, the configuration of each node device is simplified and omitted from the functional units of the node device except for the small granularity switching function unit and the large granularity switching function unit. FIG. 19A shows a state without a failure, and FIG. 19B shows a state at the time of failure.

  In a state where there is no failure (FIG. 19A), the communication paths A, B, and C are configured by the large granularity switching function units of the node # 1, the node # 3, and the node # 4. In addition, communication paths A, B, and C are multiplexed on the same optical fiber between nodes. In this state, the communication channels A, B, and C do not pass through the small granularity switching function unit.

  When an optical fiber failure connecting the node # 1 and the node # 3 occurs, the communication paths A, B, and C are disconnected. When a communication interruption occurs and a failure is detected, switching to the detour path is performed by the method shown in the first to fifth embodiments, and the state shown in FIG. 19B is obtained. The communication paths A, B, and C are reduced in bandwidth and pass through the small granularity switching function units of the node # 1 and the node # 4. In addition, before / after the small granularity switching function unit, it is multiplexed on the higher order communication path (optical fiber in the case of WDM) or separated from the higher order communication path. In node # 2, since each communication path is multiplexed and becomes a higher order communication path, it passes through the large granularity switching function unit.

(Seventh embodiment)
When the node device according to the embodiment of the present invention is used in the communication network of the sixth embodiment, for example, as shown in FIG. 20, a large-grain switching function unit (for example, connected to a different optical fiber) You may employ | adopt the structure which shares a small granularity switching function part between WSS etc.). That is, in this case, the node device 500 includes a plurality of large granularity switching function units 501 (for example, WSS), and the plurality of large granularity switching function units 501 share one small granularity switching function unit 502. The same applies to the node device 600.

  Assuming failure such as fiber breakage, the wavelength paths accommodated in different optical fibers have a low probability of failure at the same time, so the wavelength paths with low probability of failure at the same time (in this case, wavelength paths accommodated in different optical fibers) It is possible to effectively share the small granularity switching function unit. Thus, when the required scale for the power consumption and bandwidth of the small granularity switching function unit is large, the small granularity switching function unit can be efficiently shared, and the device scale of the communication network can be reduced even when the bandwidth is increased.

  For example, when the large granularity switching function unit 501 is configured by WSS and the small granularity switching function unit 502 is configured by packet fabric (a circuit that realizes packet switching), a part of the detour route when a wavelength path passing through the WSS fails The packet fabric that will be used as a can be shared.

(Summary of the embodiment, effects)
As described above, according to the embodiment of the present invention, the communication channel bandwidth and the communication channel control granularity when applying the communication channel (to be switched) according to the priority and the failure state of the working communication channel. A node device for changing the communication channel bandwidth granularity) and the transfer technology (wavelength, TDM, packet, etc.) is provided.

  In an actual communication network, the probability that the working channel is broken is smaller than the probability that the detour channel that is the backup channel is broken. For this reason, in the embodiment of the present invention, a packet switching system that increases in scale in proportion to the line bandwidth, such as a function for sharing the bandwidth in the same time zone with a plurality of lines, and is unsuitable for a large capacity communication path. By limiting the time for using this device or the like to the time of using the detour route, it is possible to statistically reduce the necessary amount of the device whose scale increases depending on the bandwidth amount for the entire communication network. On the other hand, it is possible to provide a robust line service that guarantees the continuity of more lines even with a small communication network capacity by sharing the lines.

  That is, according to the technology described in the embodiment of the present invention, a redundancy function for realizing high reliability of the communication network can be realized with a small number of spare communication paths in the backbone communication network.

A large-grain switching device that switches paths in units of cores or wavelengths, such as optical cross-connects suitable for large-capacity communication, and a small-grain switching device that switches accommodation paths in units of frames, for example, suitable for small-capacity communications , By effectively deploying the multiplexing / demultiplexing function (a configuration that can use the small-grain switching device by reducing the bandwidth only in the case of a failure), the working communication channel that shares the backup communication channel has failed simultaneously Even in this case, it is possible to continue the communication by sharing the spare resource and reduce the risk of total interruption of the transfer band.
In addition, if the switching operation as described above is only partially deployed with a small granularity switching device that causes an increase in the device scale for large capacity lines, and switching to a small granularity is not necessary, Can be processed. In the embodiment of the present invention, it is possible to identify whether the working communication path is in use or the detour communication path is used, and to identify the switching state, and to have a function of reducing the bandwidth at the time of switching, There is a feature that the bandwidth of the switching path can be made smaller than normal. For this reason, an efficient large granularity switching function can be used during normal times when there is no failure and the working communication path is used, and a small granularity switching function can be provided when switching the bandwidth is reduced. As a result, a redundancy function for realizing high reliability of the communication network with a small number of spare communication paths can be realized. In addition, when processing with a large granularity is required, a large-scale switching device such as an optical cross-connect suitable for processing large-capacity traffic can be used. Can be secured.

  The present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the claims.

1, 2, 51, 61 Large granularity switching device 3, 4, 52, 62 Small granularity switching device 10, 20, 50, 60, 100, 200, 500, 600 Node devices 11, 21, 501, 601 Large granularity switching function Units 12, 22, 502, 602 Small granularity switching function units 13, 23, 503, 603 Band filter function units 14, 24, 504, 604 Multiplexing / demultiplexing function units 15, 25 Control function units 101, 201 Optical cross-connect device 102 202 ODU cross-connect device 103, 203 Band filter function unit 104, 204 Multiplexing / demultiplexing function unit 105, 205 Control function unit 110, 210 Optical cross-connect device 111, 211 Packet SW
30, 70, 300 Communication network

Claims (8)

A node device that is connected to a client device via a low-order communication path and connected to another node device via a high-order communication path that accommodates the low-order communication path,
A large granularity switching function unit equipped with a large granularity communication path switching function;
Small granularity switching function unit with small granularity channel switching function,
A filter function unit that reduces a bandwidth of a high-order communication path between the large granularity switching function unit and the small granularity switching function unit;
Signal multiplexing processing when transmitting a signal to a detour high-order communication path connected to the small-grain switching function section, and signal separation processing when the small-grain switching function section receives a signal from the detour high-order communication path A multiplexing / demultiplexing function unit to perform,
A control function unit including a failure detection function, a switching command function for the large granularity switching function unit and the small granularity switching function unit, and a filter operation setting function for the filter function unit,
When the control function unit detects a failure in the communication path between the node device and the other node device, the filter function unit detects one or more higher-order communication corresponding to the failed communication path. A node device, wherein a bandwidth of a signal on a path is reduced, and the small granularity switching function unit switches a communication path by connecting the signal with the reduced bandwidth to the bypass high-order communication path. The control function unit has a function of identifying the priority of the communication channel, and when a communication channel failure is detected, the bandwidth value to be reduced by the fill multifunction unit is changed according to the priority of the communication channel. The node device according to claim 1, wherein: The control function unit has a function of identifying a failure state of a communication channel or a priority of a higher-order communication channel in which a failure is detected, and the large granularity switching is performed according to the failure state of the communication channel or the priority. The node device according to claim 1, wherein it is determined which of a communication path switching by a functional unit and a communication path switching by the small granularity switching functional unit is to be performed. The said control function part changes the zone | band value reduced in the said fill multifunctional part according to the failure state of the said communication path, when the failure of a communication path is detected. Node device. 5. The number of the large granularity switching function units is plural, and the small granularity switching function unit is shared by the plurality of large granularity switching function units. 6. Node equipment. While configuring the large grain size switching function unit with an optical cross-connect device,
The small granularity switching function unit is configured by a TDM cross-connect device, or the small granularity switching function unit and the filter function unit are configured by a packet switch. The node device described in 1.   A communication system in which the node devices according to any one of claims 1 to 6 are connected by an optical fiber. A failure switching method executed by a node device connected to a client device via a low-order communication path and connected to another node device via a high-order communication path that accommodates the low-order communication path,
The node device includes a large granularity switching function unit having a large granularity channel switching function, a small granularity switching function unit having a small granularity channel switching function, the large granularity switching function unit, and the small granularity switching unit. A filter function unit that reduces a bandwidth of a high-order communication path with the function unit, and the failure switching method includes:
Determining a priority of a higher order communication path corresponding to a failure state of the communication path or a communication path in which the failure is detected when a communication path failure is detected;
Determining which of the communication path switching by the large granularity switching function section and the communication path switching by the small granularity switching function section is to be performed according to the failure state of the communication path or the priority; ,
When the communication path is switched by the small granularity switching function section, the filter function section reduces the band of the signal of one or a plurality of higher order communication paths corresponding to the failed communication path, and the small granularity switching function A fault switching method, wherein the unit includes a step of switching the communication path by connecting the signal with the reduced bandwidth to the detour higher-order communication path.

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