Communication apparatus and system

The present invention relates to a communication device and a communication system.

[0002] [Conventional Technology] In recent years, the importance of data communication has increased due to the spread of the Internet and the like. For this reason, the ATM network defined by ITU-T I.150 has been introduced to handle telephone and data communications in an integrated manner. In addition, the SONET network defined by ANSI T1.105, which is a high-speed optical communication network to support significantly increasing transmission capacity, or the SDH defined by ITU-T G707 (however, SONET and SDH are basically the same). Function), and the optical network (OTN) defined by ITU-T G.872, which introduced wavelength division multiplexing (WDM) technology to increase the transmission capacity per fiber, has been introduced.

[0003] These networks are interconnected after the upper hierarchy and the lower hierarchy are defined based on the hierarchical structure based on the OSI (Open System Interconnection) basic reference model defined by ISO.

[0004] According to the regulations of individual networks, in ATM, SONET / SDH, and OTN, ATM is the highest layer, OTN is the lowest layer, and SONET and SDH are positioned as the layer in between. .. In addition, each network is further layered into sub-networks. For example, an ATM network can be divided into Virtual Path and Virtual Channel. In SONET / SDH and OTN, each subnetwork is layered.

[0005] [Problem to be Solved by the Invention] Table 1 shows the upper and lower relationships of the sub-network in which only the hierarchy related to switching is shown except for the section defined by the repeater.

[0006] [Table 1]<img file="JP3775111B2_D0001.tif" />[0007] Further, in this case, when the terms "upper" and "lower" are used, the relationship between the defined interval and the multiplexing is shown in FIG. In the figure, 100 to 112 represent upper hierarchy devices, 300 to 310 represent lower hierarchy devices, 500 to 502 represent upper hierarchy lines, and 600 represent lower hierarchy lines.

[0008] In this figure, a plurality of higher-level devices are connected to one lower-level device, and higher-level devices 100 to 102 are connected to the lower-level device 300, and higher-level devices 110 to 112 are connected to the lower-level device 310. It is connected via the upper layer lines 500 to 502. The lower device uses the SONET network specified by ANSI T1.105, the time division multiplexing method specified by the SDH network specified by ITU-T G707, or the ITU --T G.872, for example. It is bundled by a method such as wavelength division multiplexing (WDM) specified by the specified OTN, and the data transmission capacity per physical medium or unit time is increased and transmitted to the lower layer line.

[0009] The upper layer lines 500, 501, and 502 are transmitted by the upper devices 100 and 110, 101 and 111, 102 and 112, respectively, of a portion for transmitting line monitoring control information, for example, a SONET signal or an overhead portion of an SDH signal. , Receive processing is performed. The section that processes the monitoring control information of the upper layer line is called the upper layer line section (hereinafter abbreviated as the upper layer section). These upper layer lines 500 to 502 may be physically different lines, and even if physically the same line is used, for example, a path defined by a SONET network or an SDH network, it is logical. It does not matter even if it is an independent line. Similarly, the lower layer line 600 is terminated by the lower layer devices 300 and 310, and the portion sandwiched between the lower layer devices 300 and 310 is referred to as a lower layer line section (hereinafter abbreviated as a lower layer section).

[0010] As described above, since the signal of the upper layer becomes the signal of the lower section through the multiplexing process, the signal of the upper layer may be the same as the signal of the lower layer from the viewpoint of the signal band. But it doesn't grow. Further, regarding the defined section, the upper hierarchy may be the same as the lower hierarchy, but it is not shortened.

[0011] Here, consider a case where both the upper layer and the lower layer as shown in FIG. 2 have a switching processing unit. In this figure, the upper layer lines 500 to 505 are terminated by the upper layer devices 100 to 104 and the upper layer line signal processing units 120 to 124 and 125 to 129 in the upper layer devices 100 to 104.

[0012] The upper layer lines 500 to 503 are subjected to multiple separation processing by the multiple separation units 440 and 450 in the lower layer devices 300 and 310, and are subjected to multiple separation processing via the lower section of the lower layer line 600 or 601. 100 ~ 103 and 110 ~ 113 are connected. Similarly, the upper layer lines 504 to 505 are subjected to multiple separation processing by the multiple separation units 441 and 451 in the lower layer devices 301 and 311 and are subjected to multiple separation processing via the lower section of the lower layer line 602 or 603. 103 ~ 104 and 113 ~ 114 are connected.

[0013] Hereinafter, for the sake of simplicity, a 1 + 1 type switching system in which a working line and a spare line exist as a pair, and the same data is transferred in a normal state and a high quality line is selected on the receiving side will be described. To do. In this figure, in the lower layer lines 600 and 601, data having the same contents is branched and transmitted by the lower layer line route branch / selection unit 420 or 430 of the lower layer device. Similarly, in the lower layer lines 602 and 603, the same data is branched and transmitted by the lower layer line route branch / selection unit 421 or 431 of the lower layer device. When there is no line failure and no device failure, the lower layer line 600 is selected as the active line by the lower layer line route branching / selection unit 420 or 430 of the lower layer device, and some failure occurs and the lower layer line 600 becomes When it becomes unusable, 601 is selected as a backup line by the lower layer line route branching / selection unit 420 or 430 of the lower layer device, and the lower layer line is restored in the event of a failure.

Similarly, in the lower layer lines 602 and 603, in the normal state, the lower layer line 602 is selected as the active line by the lower layer line route branch / selection unit 421 or 431 of the lower layer device, and some failure occurs and the lower layer When the line 602 becomes unusable, 603 is selected as a spare line by the lower layer line route branching / selection unit 421 or 431 of the lower layer device, and the lower layer line is restored in the event of a failure.

In this figure, similarly, in the upper section, the same data is branched and transmitted to the upper layer lines 503 and 504 by the upper layer line route branching / selection units 220 and 230 of the upper layer device, respectively. To. As in the case of the lower section, the upper layer line 503 is normally selected as the active transmission line by the upper layer line route branch / selection unit 220 or 230 of the upper layer device, and when a failure of the upper layer line 503 occurs, the backup transmission line is selected. The upper layer line 504 is selected by the upper layer line route branching / selection unit 220 or 230 of the upper layer device.

Next, when a failure occurs in the lower layer line 600 shown in FIG. 3, a switching process between the upper layer and the lower layer by the method devised for the explanation of the embodiment of the present invention will be described. FIG. 3 shows an extracted portion of the upper-level device and the lower-level device having the switching processing unit in FIG.

[0017] In this method, the failure that occurs in the lower layer is notified to the upper layer device by alarm transfer to the upper layer. The concept of alarm transfer is shown in Figure 4. In the figure, the upper layer lines 500 to 502 are terminated by the upper layer devices 100 to 112, the connection between the upper layer and the lower layer is made by the lower layer devices 300 and 310, and between the lower layer devices 300 and 310. It is connected by a lower hierarchy line 600.

[0018] Now, it is assumed that a failure occurs in the lower layer line 600. The lower layer line 600 shows a signal transmitted in both directions, but in this case, consider the case where the influence of a failure affects both directions. First, the lower hierarchy devices 300 and 310 each detect that a failure has occurred in the lower hierarchy line. Then, an alarm transfer signal (AIS) for transmitting the detection of the failure to the upper layer is sent to all the upper layer lines 500 to 502. As a result, all the upper layer devices 100 to 102 and 110 to 112 connected to the lower layer devices can be identified as having failed in the lower layer section 600, and are currently sent to the upper layer lines 500 to 502. Recognize that the data is invalid.

[0019] AIS is each layer of each network shown in Table 1, that is, Virtual Path and Virtual Channel of ATM network, Path and line of SONET network, Path and M section of SDH network, Optical Channel and Optical Multiple of OTN network. Each is stipulated in Section, etc., and the stipulations for each network also stipulate the alarm transfer from the lower layer to the upper layer in each network according to Table 1. It also stipulates alarm forwarding across networks. For example, alarm transfer when the lower layer is a SONET network and the upper layer is an ATM network is specified by ITU-T I.610.

FIG. 5 shows a conceptual diagram of alarm transfer from the lower layer to the upper layer. The line connecting the upper layer and the lower layer in the figure indicates the upper layer line, and the line connecting the lower layers indicates the lower layer line. The alarm transfer is performed from the lower layer to the upper layer, and is not performed from the upper layer to the lower layer.

[0021] With such an alarm forwarding mechanism, the upper layer can recognize the occurrence of a failure in the lower layer. In this method, the switching processing unit of the upper layer and the lower layer has an independent protocol, determines whether switching is necessary based on the detected failure information or AIS, and performs the switching processing independently. Therefore, when a failure occurs in the lower layer line 600 in FIG. 3, the lower layer devices 300 and 310 detect that the failure has occurred in the lower layer line 600 and start the switching process in the lower layer. Then, the switching process from the active line 600 in the lower layer to the spare line 601 in the lower layer is executed. Further, the upper layer devices 100 and 110 determine from the AIS that has received the failure in the lower layer line 600, and start the switching process in the upper layer. Then, the switching from the active line 503 of the upper layer to the spare line 504 of the upper layer is executed.

[0022] In this case, since the switching process is performed independently on both layers, even if the line is restored if the switching process is originally performed on either layer, the switching process on both layers is executed, which is useless. Switching will be executed. To prevent this, there is a method to permanently stop the switching process of one of the two layers when they have different switching functions. For example, ANSI T1.105 uses NUT (Non-preemptible Unprotected Traffic), which prohibits switching of SONET devices on a path-by-path basis, assuming that a network with a switching function such as an ATM is connected as a higher layer. It stipulates.

Further, as an inconvenience of performing the switching process independently in both layers, when the devices in the lower layers are being switched, there is a possibility that the contents of the switching protocol performed between the upper devices may not be correctly passed. is there. To prevent this, there is also a method of stopping one of the switching processes for a certain period of time. For example, in the connection between the ATM network and the SONET network or SDH network, according to the method specified in ITU-T I.630, when the lower layer SONET or SDH is performing the switching process, the ATM network is used. A hold-off time is provided to stop the switching operation for a certain period of time, and this time can be changed every 500 ms in the range of 0 to 10 s.

[0024] As described above, in a system having switching functions in the upper layer and the lower layer, respectively, it is necessary to permanently stop one of the switching processes or for a certain period of time, so that the switching time is wasted. It will occur.

The NUT method defined in ANSI T1.105, which was given as an example of a method for permanently stopping the switching process of one layer, stops the switching of the SONET network, so that the SONET switching processing unit is wasted. Become.

[0026] Further, in the method specified in ITU-T I.630, which is given as an example of a method of stopping the switching process of one layer for a certain period of time, when the failure that cannot be relieved by the SONET network is relieved by the ATM network. , You have to wait at least 500ms. The time chart by this method is shown in FIG. Now, when a failure occurs in a lower layer line, the lower layer device detects that a failure has occurred in the line and sends AIS to all the upper layer lines. As a result, all the upper layer devices connected to the lower layer devices recognize that the lower section has been damaged and the data currently sent to the upper layer line is invalid. However, in order to prevent switching from being performed independently in both layers and unnecessary switching to be executed, the upper layer device has a holdoff time as described above, so that the upper layer device starts from the lower layer device. Even if AIS is received, the switching process is not executed during the holdoff time. In this figure, it is assumed that the upper layer is ATM and the lower layer is SONET or SDH, and the holdoff time in the upper layer device is 500 ms.

[0027] The lower-level device transfers the AIS to the upper-level device and executes switching processing between the lower-level devices. In this case, since it is a 1 + 1 type switching system, the receiving device that detects the failure of the active line switches to the backup line at its own route selection unit. The time required for this switching is specified within 50 ms, for example, in SONET. However, if the backup line also has a failure, or if the device has already failed and the route selection unit does not operate correctly, the switching process may fail. That is, the receiving device continuously detects the failure from the line and continues to transfer the AIS to the upper layer line. However, the upper layer device continues to stand by without performing the switching process for recovering the failure until the holdoff time elapses. Then, after the hold-off time elapses, switching processing is performed between the upper layer devices. That is, the receiving device of the upper layer starts switching to the spare line of the upper layer at its own route selection unit. In the case of ATM, ITU-T Draft New Recommendation As specified in I.630, the switching processing time has been raised by 50ms as the target value. If the switching process is completed successfully, the upper layer device can receive the signal from the normal standby line, and can correctly receive the signal from the line without detecting AIS or a failure.

As shown in this figure, SONET switches within 50 ms, but the time of 450 ms, which is the hold-off time of 500 ms minus the SONET processing time of 50 ms, is a waste of time because both devices do nothing. Become.

[0029] An object of the embodiment of the present invention is to utilize the characteristics of the switching method of both layers in a communication device or a communication network having a switching function in two layers, and to perform a switching function and process of each other according to a failure situation. The purpose is to realize efficient inter-layer cooperative switching processing with less waste than before in terms of time.

[Means for Solving the Problems] One aspect of the embodiment of the present invention is as follows, and a part of the configuration is shown in FIG. The first and second upper layer devices and the first to fourth lower layer devices, each of which has a line switching means, are provided, and the first and second upper layer devices are interchangeable with each other. First and second lower tier communication that is connected via two upper tier communication lines, the first and second lower tier devices can be switched between each other, and one or more upper tier communication lines are multiplexed. Connected via a line, the third and fourth lower layer devices can be switched to each other, and are connected via a third and fourth lower layer communication line in which one or more upper layer communication lines are multiplexed. Then, between the first upper layer device and the first lower layer device and between the second upper layer device and the second lower layer device via the first upper layer communication line. The second upper layer communication line is connected between the first upper layer device and the third lower layer device and between the second upper layer device and the fourth lower layer device. When the lower layer device detects a line failure, the upper layer device is notified to stop the line switching processing execution, and the failure information of the upper layer communication line and the lower layer communication are sent. Using the line failure information, identify one or more failure-occurring lines and failure-occurring sites of the upper-layer communication line or lower-layer communication line, and there is no failure in any of the lower-layer communication lines, and either If it is identified that a failure has occurred in the upper layer communication line, the stop notification of the line switching process execution of the upper layer device is canceled for the upper layer device, and one of the lower layer communication lines fails. If it is identified that an occurrence has occurred, the maximum number of upper-tier communication lines can be used after the failure recovery process is executed, based on the failure information of the upper-tier communication line and the failure information of the lower-tier communication line. Or, in order to preferentially use a line having a higher priority than a line having a lower priority, or to maximize the number of signal lines to be restored, a plurality of upper layer devices or lower layer devices Have each

[Embodiment of the Invention] (Example 1) A switching device having a cooperative switching determination unit according to the present embodiment will be described. The conceptual diagram is shown in Fig. 8.

[0032] In the present embodiment, a determination unit for performing cooperative switching is newly provided, failure information is received from the upper layer and the lower layer, and the layer to be switched is determined according to the state of the failure. The determination unit is also configured to receive information from the upper layer whether or not this upper device has another detour route, that is, another route that does not pass through the lower device that is going to perform the switching process. .. A switching stop signal can be given from the lower layer to the upper layer in addition to the conventional alarm transfer signal, whereby switching control of the lower layer can be performed first.

[0033] First, before explaining the switching device according to the present embodiment, an example of the device configuration for realizing the method as a comparative example will be described with reference to FIG. 5 and the like. FIG. 6 is a detailed representation of a part of FIG. 2 when the network in FIG. 2 is configured by the conventional lower layer devices and upper layer devices.

[0034] In the figure, the lower layer device 310 is connected to another lower layer device via the lower layer active line 600 and the lower layer spare line 601. Further, the lower layer device 310 is also connected to the upper layer devices 110 to 113 via the upper layer lines 500 to 503. The upper layer device 113 has a spare line 504 of the upper layer, and is connected to another lower layer device or a higher layer device. In this case, the spare line 504 in the upper layer can transmit the same data as the line 503 in the upper layer as needed.

[0035] Here, the propagation of a one-way signal flowing from the left side to the right side of the lines 600 to 601 and 500 to 504 will be described. The same can be described for the signal flowing from the right side to the left side as shown below.

The lower layer device 310 includes lower layer line signal reception processing units 330 to 331, lower layer line failure detection units 360 to 361, lower layer line route branching / selection unit 430, and multiple separation units for lower layer lines. It has 450, a lower layer line switching determination unit 710, an alarm transfer determination unit 750 to the upper layer, an upper layer line signal transmission processing unit 340 to 343, and an alarm transfer signal issuing unit 470 to 473 to the upper layer. .. The upper layer device 113 includes upper layer line signal reception processing units 133 to 134, upper layer line failure detection units 163 to 164, upper layer line route branching / selection unit 230, and upper layer line switching determination unit 720. ..

[0037] Here, consider a case where a failure occurs in the lower layer line 600. In this case, the lower layer line failure detection unit 360 detects that a failure has occurred, and notifies the lower layer line switching determination unit 710 and the alarm transfer determination unit 750 to the upper layer that the failure has been detected. As a failure detection method, for example, in the case of SONET and SDH, an error rate detection method using LOS (Loss of Signal) or BIP (Bite Interleaved Parity) is used. In ATM, CRC (Cyclic Redundancy Check) is used. In the case of SONET and SDH, the AIS format specified by ANSI T1.105 or ITU-T G707 is used as the alarm transfer method. For ATMs, the OAM cell method specified in ITU-T I.610 is used.

[0038] The alarm transfer determination unit 750 is set to the alarm transfer signal issuing units 470 to 473 to the upper layer so that the AIS is transmitted to all the lines of the upper layer lines 500 to 503 affected by the lower layer line 600. Give instructions. The lower layer line switching determination unit 710 executes the switching process so as to select the spare line 601 of the lower layer and transfer the data by the lower layer device and the switching protocol facing each other. This figure shows a 1 + 1 type switching system. For example, the switching protocol is 1 + 1 type, 1: N type, BLSR (Bidirectional Line Switched) specified in ANSI T1.105. Ring) etc. can be used. Hereinafter, the case of 1 + 1 type will be described for simplicity. In the 1 + 1 type switching system, the receiving device that detects the failure of the active line switches to the standby line that can normally transfer data at its own route selection unit. That is, the lower layer line switching determination unit 710 branches the lower layer line route so as to select a line without a failure from the active line 600 and the standby line 601 based on the information received from the lower layer line failure detection units 360 and 361. -Instruct the selection unit 430. The lower layer line route branching / selection unit 430 notifies the alarm transfer determination unit 750 when its own selection process is performed correctly, and the switching process in the upper layer device is unnecessary, that is, to the upper layer device. Notify that the alarm transfer is not required. When the alarm transfer determination unit 750 determines that the switching process in the lower layer device is normally performed and the AIS transfer is no longer necessary, the alarm transfer signal issuing units 470 to 473 to the upper layer are alerted. Instruct not to transfer. Further, the alarm transfer determination unit 750 receives the failure information of both lines from the lower layer line failure detection units 360 and 361, and determines whether the line selected by the lower layer line route branching / selection unit 430 is appropriate. To do. At this time, if there is a contradiction between the failure information of both lines and the processing of the route selection unit, the alarm transfer signal issuing units 470 to 473 to the upper layer are continuously instructed to perform AIS transfer.

[0039] The upper layer devices 110 to 113 that have received the AIS by the upper layer lines 500 to 503 independently perform the upper layer line switching process according to the upper layer switching protocol.

[0040] Taking the upper layer device 113 as an example, the switching process of the upper layer device will be described. In this case, the upper layer device 113 uses the upper layer line failure detection units 163 to 164 to identify that the upper layer line 503 transfers the AIS and the data content is invalid, and the upper layer line switching determination unit. Inform 720. The upper layer line switching determination unit 720 executes the switching process so as to select the spare line 504 of the upper layer and transfer the data by exchanging the switching protocol with the opposite upper layer device. In this case, there are several possible switching protocols, but in the case of ATM, a 1 + 1 type switching protocol is specified in ITU-T Draft New Recommendation I.630.

[0041] Of course, even when the upper layer line failure detection units 163 to 164 detect a failure of the upper layer line 503 instead of the AIS, the upper layer device 113 also exchanges a switching protocol with the upper layer device in the same manner. The switching process is executed so as to select the backup line 504 of the upper layer.

Although omitted in this figure, the upper layer device 113 includes a transmission processing unit for a higher layer line signal, an alarm transfer signal issuing unit for a higher layer, and an alarm transfer determination unit for a higher layer. In some cases, it has and transfers an alarm to a higher layer.

[0043] A first embodiment of a switching device having a cooperative switching determination unit of the present invention will be described in detail with reference to FIG. This figure is a detailed representation of a part of FIG. 2 when the network in FIG. 2 is configured by the lower layer devices and the upper layer devices of the above method.

[0044] The upper layer and the lower layer in the embodiment of the present invention are applicable to all of the ATM, SONET, SDH, and OTN shown in Table 1 to which the relative relationship between the upper layer and the lower layer is given. In addition, any of Virtual Path, Virtual Channel, Path, Line, etc. in the ATM, SONET, and SDH sub-networks may be used. According to the hierarchical structure of the OSI (Open System Interconnection) basic reference model defined by ISO, the idea of the embodiment of the present invention can be applied to all that can be given a relative relationship between upper and lower levels.

[0045] In the figure, the lower layer device 310 is connected to another lower layer device via the lower layer active line 600 and the lower layer spare line 601. This figure shows a 1 + 1 type switching system in which the active and spare are paired one by one and the same data is transferred in the normal state. However, the embodiment of the present invention is for n active lines. The same can be applied to a network having a 1: n type switching protocol with one spare line. Further, although FIG. 2 shows a linear network, the idea of the embodiment of the present invention can be similarly applied to a ring network and a mesh network. Hereinafter, a network having a 1 + 1 linear type switching protocol will be described.

[0046] The lower-level device 310 is also connected to the upper-level devices 110 to 113 via higher-level lines 500 to 503. The upper layer device 113 has a spare line 504 of the upper layer, and is connected to another lower layer device or a higher layer device. In this case, the spare line 504 in the upper layer can transmit the same data as the line 503 in the upper layer as needed.

[0047] Here, the propagation of a one-way signal flowing from the left side to the right side of the lines 600 to 601 and 500 to 504 will be described. The same can be described for the signal flowing from the right side to the left side as shown below.

[0048] The lower layer device 310 includes lower layer line signal reception processing units 330 to 331, lower layer line failure detection units 360 to 361, and lower layer line route branching / selection unit 430, as in the device described with reference to FIG. , Lower layer line multiplex separation unit 450, lower layer line switching determination unit 710, alarm transfer determination unit 750 to the upper layer, upper layer line signal transmission processing units 340 to 343, and alarm transfer signal to the upper layer. It has a ejection part 470 to 473. However, in this figure, the lower layer line switching determination unit 710 and the alarm transfer determination unit 750 to the upper layer are omitted.

Compared with the conventional device, the lower-level device 310 further detects upper-layer line failures for the lower-level active line 600 of the lower-level device 310 and upper-level line failure detection for the lower-level backup line 601. It has units 465 to 468 and units 480 to 483 for issuing a switching stop signal to the upper layer of the lower layer device.

[0050] As the medium for transferring the switching stop signal, for example, in OTN, a wavelength-multiplexed monitoring signal may be used, and in SONET or SDH, an overhead may be used. In ATM, it may be transferred by an OAM (Operation Administration Maintenance) cell or the like.

[0051] The upper layer device 113 includes the upper layer line signal reception processing units 133 to 134, the upper layer line failure detection units 163 to 164, the upper layer line route branching / selection unit 230, and the upper layer line, as in the conventional device. It has a switching determination unit 720. However, in this figure, the upper layer line switching determination unit 720 is omitted.

[0052] Like the upper layer devices 113, the upper layer devices 110 to 112 also have upper layer line signal reception processing units 130 to 132 and upper layer line failure detection units 160 to 162.

[0053] The upper layer device 113 further has an upper layer line detour route presence / absence information signal issuing unit 803 as compared with the conventional device. Like the upper layer devices 113, the upper layer devices 110 to 112 also have upper layer line detour route presence / absence information signal issuing units 800 to 802.

[0054] As the medium for transferring the detour route presence / absence information signal, for example, in OTN, a wavelength-multiplexed monitoring signal may be used, and in SONET or SDH, an overhead may be used. In ATM, a method of transferring by an OAM (Operation Administration Maintenance) cell or the like can be considered.

[0055] The detour route referred to here means a usable upper-layer line via another lower-layer device. This can be determined from the network connection status given by the administrator or the failure occurrence status sent from the failure detection unit of the upper layer standby line. Simply, when constructing a network, the administrator grasps whether there is a detour route on each upper layer line, sets the presence or absence of the detour route in advance, and transmits the set contents to the lower layer device. As another simple method for determining the presence or absence of a detour route, the presence or absence of a detour route may be determined only by whether or not the upper layer backup line is normal. That is, if the failure detection unit 164 of the upper layer spare line detects a failure in the upper layer spare line 504, there is a detour route, and if no failure is detected, there is no detour route. Issue information on the presence or absence of a detour route. Further, the logical OR of the information on the presence or absence of the detour route set by the administrator and the information on whether or not the upper layer backup line is normal may be taken. That is, in this case, only when the administrator sets that there is a detour route and the upper layer spare line is normal, the upper layer line detour route presence / absence information signal issuing unit 800 to 802 emits that there is a detour route.

[0056] In the embodiment of the present invention, the inter-layer cooperative switching determination unit 700 is further provided. The location of the inter-layer cooperative switching determination unit 700 is drawn outside the lower-level devices 310 or the upper-level devices 110 to 113 in this figure, but it may be inside the lower-level device 310. It may be in the upper layer devices 110 to 113.

[0057] The cooperative switching determination unit 700 includes the upper layer failure information sent from the upper layer line failure detection units 160 to 164 of the upper layer devices 110 to 113 and the lower layer line failure detection units 360 to 361 of the lower layer device 310. It receives the lower layer failure information sent and the upper layer failure information sent from the upper layer line failure detection units 460 to 468 of the lower layer device 310.

[0058] The cooperative switching determination unit 700 has a function of collating the failure information of the lower layer line and the upper layer line when the failure information is sent. The cooperative switching determination unit 700 can control the lower layer line route branching / selection unit 430 of the lower layer device 310 and the switching stop signal issuing units 480 to 483 to the upper layer. Further, the cooperative switching determination unit 700 can receive the detour route presence / absence information from the upper layer line detour route presence / absence information signal issuing units 800 to 803 of the upper layer devices 100 to 103.

FIG. 17 shows a detailed configuration of the cooperative switching determination unit 700. The cooperative switching judgment unit includes the failure information collection unit 900 for failure information detected by the lower layer device, the failure information collection unit 920 for failure information detected by the upper layer device, and the failure information detected by the lower layer device and the upper layer device, respectively. It has a collation unit 910, a case classification state calculation unit 930, a case classification state selection unit 940, and a switching stop signal issuance request unit 950 for the lower layer device.

[0060] Then, the failure information collection unit 900 of the failure information detected by the lower layer device has a table 901 describing the failure information detected by the lower layer device related to the lower layer active line and the lower level related to the lower layer backup line. It has a table 902 that describes information on failures detected by the layered device. The failure information collection unit 920 of the failure information detected by the upper layer device has a table 921 in which the failure information detected by the upper layer device related to the upper layer active line is described. The failure information collation unit 910 detected by the lower hierarchy device and the upper hierarchy device each has a table 911 that describes information on a valid upper hierarchy active line and a table 912 that describes information on a valid upper hierarchy backup line. The case-separated state calculation unit 930 calculates the table 931 for calculating the first case-separated state, the table 932 for calculating the second case-separated state, and the third case-separated state. It has a table 932 and a table 933 that calculates the fourth case-separated state. The case-separated state selection unit 940 has a maximum number of usable lines state extraction unit 941 and a minimum number of switching state extraction units 942. The switching stop signal issuance request unit 950 to the upper layer of the lower layer device is the switching stop signal issuance request unit 950 from the failure information collection unit 900 of the failure information detected by the lower layer device to the upper layer of the lower layer device. The interrupt signal line 960 is connected. The switching stop signal issuing request unit 950 to the upper layer of the lower layer device is connected to the switching stop signal issuing units 480 to 483 to the upper layer of the lower layer device, and the result of determination by the cooperative switching processing determination unit 700. Based on the above, the switching stop signal issuing units 480 to 483 of the lower layer device to the upper layer issue an instruction as to whether or not to output the switching stop signal.

[0061] In the failure information table 901 detected by the lower layer device regarding the lower layer active line, the failure detection information from the lower layer active line failure detection unit 360 of the lower layer device and the lower layer active line of the lower layer device are displayed. Failure detection information is sent from the corresponding upper layer line failure detection units 460 to 463, and the failure detection information can be described for each upper layer line. In the failure information table 902 detected by the lower layer device related to the lower layer backup line, the failure detection information from the lower layer backup line failure detection unit 361 of the lower layer device and the upper level corresponding to the lower layer backup line of the lower layer device are displayed. Failure detection information is sent from the layered line failure detection units 465 to 468, and the failure detection information can be described for each upper layer line.

Failure information table 921 detected by the upper layer device regarding the upper layer active line is sent failure detection information from the upper layer line failure detection units 160 to 163 corresponding to the upper layer active line of the upper layer device. , The failure detection information can be described for each upper layer line.

[0063] The effective upper-level working line information table 911 is the upper-level working line 500 to 503 between the lower-level device 310 and the upper-level device 110 to 113 that can be currently used without any trouble in this section. This is a table that describes the hierarchical working line in units of higher-level lines. The effective upper-level active line is obtained by logically subtracting the contents of the failure information table 901 detected by the lower-level device related to the lower-level active line from the contents of the failure information table 921 detected by the upper-level device related to the upper-level active line. .. That is, in the failure information table 921 detected by the upper layer device, it is described that there is a failure (abnormality) in the upper layer line 500, and in the failure information table 901 detected by the lower layer device, there is no failure (normal) in the upper layer line 500. When described, the cause of the failure is considered to be the cause of the failure on the upper layer line 500 between the lower layer device 310 and the upper layer device 110 shown in FIG. Therefore, in this case, it is described as unusable in the effective upper layer active line information table 911. Next, in the failure information table 921 detected by the upper layer device, it is described that there is a failure (abnormal) in the upper layer line 500, and in the failure information table 901 detected by the lower layer device, there is a failure (abnormal) in the upper layer line 500. When described, the cause of the failure is considered to be the cause of the failure on the left side of the lower layer device 310 shown in FIG. 9, that is, on the lower layer line 600 or upstream thereof. In this case, it is described that it can be used in the effective upper layer active line information table 911. If the failure detection methods of both devices do not exactly match, the failure information table 921 detected by the upper layer device describes that there is no failure (normal) for the upper layer line 500, and the failure information detected by the lower layer device. If it is described in Table 901 that there is a failure (abnormality), it is considered that the upper layer device can receive the information without any problem, and the result of the failure information table 921 detected by the upper layer device is believed. Therefore, in this case, it is described that it can be used in the effective upper layer active line information table 911.

[0064] Table 912, which describes valid backup line information, collects the contents from the upper layer line detour route presence / absence information signal issuing units 800 to 803 in each upper layer device 110 to 113, and collects the contents from the upper layer line unit. It is a table to describe. In other words, this is a table that describes the upper layer spare lines that can be used instead when the upper layer devices 110 to 113 detect a failure on the upper layer active lines 500 to 503. is there.

[0065] There are no strict rules regarding how to determine the assumed case classification state and the number of tables to be possessed, but here, an example in the case of using four case classification state calculation tables will be described. .. The first case-separated state is a state in which only the active line is used in both the lower layer and the upper layer. In the second case classification state, the active line is used in the lower layer, and the upper layer line uses the active line and the standby line, whichever has no obstacle. The third case-separated state is a state in which a spare line is used in the lower layer and an active line is used in the upper layer line. In the fourth case classification state, the spare line is used in the lower layer, and the upper layer line uses the active line and the spare line, whichever has no obstacle.

[0066] A method of holding the value of each case-separated state table will be described. In each case-separated state table, the content of which upper-layer line is relieved when the cooperative switching process is completed according to the previously determined state is described for each upper-layer line.

[0067] In the first case division state, neither the upper layer device nor the lower layer device is subjected to the switching process. Therefore, the value of the case division state calculation table 931 is detected by the upper layer device related to the upper layer active line. Same as failure information table 921.

[0068] In the second case division state, the lower layer device does not perform switching, and only the upper layer device performs the switching process. Therefore, in this case division state calculation table 932, the upper layer is currently used for each upper layer line. Compare the values of the failure information table 921 detected by the upper layer device related to the line and the effective upper layer backup line information table 912, and use the better value (if there is no failure, use that).

[0069] In the third case division state, switching is performed by the lower layer device, and switching processing is not performed by the upper layer device. Therefore, in this case division state calculation table 933, the lower layer spare line is used for each upper layer line. A logical OR is taken between the failure information table 902 detected by the lower layer device and the effective upper layer active line information table 911.

[0070] In the fourth case classification state, since the state in which the switching process is performed by both the lower layer device and the upper layer device is considered, the case classification state calculation table 934 is the third case for each upper layer line. Compare the value in the case classification status table 933 with the value in the effective upper layer backup line information table 912 and adopt the better value (if there is no obstacle, use that).

[0071] The number of usable upper layer lines and the number of switches are calculated from the results of the four case classification state calculation tables calculated in this way, and the case classification state selection unit 940 selects the optimum state. The number of upper-tier lines that can be used is calculated by summing the number of normal lines that are described as usable for each upper-tier line in the case classification status table.

From this result, the maximum number of usable lines state extraction unit 941 extracts the state in which the maximum number of usable lines is in each case-separated state. At this time, if there is a case division state having a plurality of maximum numbers, all the case classification states are extracted, and the extracted result is passed to the next switching number minimum state extraction unit 942.

[0073] The calculation of the number of switches is calculated as follows. In the first case-separated state, the number of switching is 0 because the switching is not performed. In the third case classification state, switching is performed only by the lower hierarchy device, so the number of switching is 1. In the second case classification state, switching is performed only in the upper layer device, so the number of lines with failures described in the failure information table 901 detected by the lower layer device related to the lower layer active line is the same as the number of upper layer devices. The switching process at will be started. Therefore, the number of switches is the sum of the number of lines with failures described in the failure information table 901. In the fourth case classification state, switching is performed by both the lower layer device and the upper layer device. The switching process in the upper layer device is performed for the number of lines having a failure described in the failure information table 902 detected by the lower layer device related to the lower layer standby line. The total number of switchings is the number of times the number of switchings 1 in the lower hierarchy device is added to this.

[0074] Based on the number of switches calculated in this way, the minimum number of switches state extraction unit 942 extracts the state in which the number of switches is the minimum. Here, if there are a plurality of case-separated switching states in which the number of usable lines is the maximum and the number of switching is the minimum, the state in which the switching process is not performed in the lower layer device is adopted. This is because the time required for all switching processing is shorter when the switching processing is performed only on one layer (in this case, the upper layer) than when switching is performed on both layers. That is, when there are multiple case-separated states in which the number of usable lines is the maximum and the number of switches is the minimum, the second case-separated state is selected instead of the third or fourth case-separated state. To do.

[0075] When it becomes necessary for the lower layer switching process to be performed by the switching number minimum state extraction unit 942, that is, when the third or fourth case classification state is selected, the lower layer device 310. Starts the lower layer line route selection unit 430 of the lower layer device of, and selects the lower layer spare line 601. When the switching process in the lower layer device is completed, or when the switching process in the lower layer device is not required (that is, when the first or second case classification state is selected), the lower layer Notifies the requesting unit 950 of the switching stop signal to the upper layer of the device that it is no longer necessary to issue the switching stop signal to the upper layer of the lower layer device. The switching stop signal issuance requesting unit 950 to the upper layer of the lower layer device issues an instruction to the switching stop signal issuing units 480 to 483 to the upper layer of the lower layer device to release the switching stop signal. Then, each of the upper layer devices 110 to 113 starts the switching process in the upper layer.

[0076] Hereinafter, a processing procedure for performing cooperative switching when a failure occurs will be described.

[0077] In the case of this embodiment, it is assumed that the upper layer line failure detection units 460 to 468 of the lower layer device 310 can detect a failure in units of one upper layer line.

[0078] When the lower layer line failure detection unit 360 or the upper layer line failure detection units 460 to 463 of the lower layer device 310 detects a failure, the failure detection information is sent to the inter-layer cooperative switching determination unit 700 and the upper layer. Notify the transfer signal transmitters 470 to 473. The inter-layer cooperative switching determination unit 700 stops switching so that the switching stop signal is transmitted before or at the same time as the AIS is transmitted so that the switching process in the upper layer is not started by the AIS in the upper layer devices 110 to 113. Give instructions to the signal transmitters 480 to 483.

At this time, when the cooperative switching determination unit 700 receives a notification that a failure has been detected from either the lower layer line failure detection unit 360 or the upper layer line failure detection unit 460 to 463 of the lower layer device 310, An interrupt signal is generated from the failure information collection unit 900 from the lower layer device, and is transmitted through the interrupt signal line 960 to instruct the lower layer device's switching stop signal issuance request unit 950 to request the switching stop signal. .. The switching stop signal issuance requesting unit 950 causes the switching stop signal issuing units 480 to 483 of the lower hierarchy device to issue a switching stop signal.

Next, the cooperative switching determination unit 700 collects failure information from the upper layer line failure detection units 460 to 468 of the lower layer device 310 for a certain period of time, and the failure information collection unit 900 of the failure information detected by the lower layer device. Failure information is described for each upper layer line in the failure information table 901 detected by the lower layer device related to the lower layer active line and the failure information table 902 detected by the lower layer device related to the lower layer spare line. This corresponds to the case where the signal propagation speed is different, the signal transmission path is different depending on the device configuration, and there is a time lag in the signal transmission of the failure information from the multiple failure detection units to the cooperative switching judgment unit 700 even if the failure has the same cause. To do.

[0081] The cooperative switching determination unit 700 also collects failure information from the upper layer line failure detection units 160 to 163 of the upper layer devices 110 to 113 and the upper layer line detour route presence / absence information signal issuing units 800 to 803 for the above-mentioned fixed time. To do. Then, the failure information from the lower layer devices 310 and the failure information from the upper layer devices 110 to 113 are collated by the method described in the detailed configuration of the cooperative switching determination unit.

[0082] FIGS. 18, 19 and 20 show three processing examples of the cooperative switching determination unit when a failure occurs. First, in the example of FIG. 18, the three upper-layer line failure detection units 460,461,462 of the lower-layer device 310 detect a failure with respect to the active line 600 of the lower layer, and the lower-layer device 310 with respect to the spare line 601 of the lower layer. One upper layer line failure detection unit 468 detects a failure, and three upper layer line failure detection units 160,161,162 of the upper layer devices 110 to 112 detect a failure for the upper layer active lines 500 to 503, and the upper layer One upper layer line detour route presence / absence information signal issuing unit 801 of the devices 110 to 113 indicates that there is no detour route and indicates a state in which the spare line of the upper layer cannot be used.

The failure information detected by these lower layer devices and upper layer devices is described in the failure information table 901, 902, 921 as shown in FIG. 18 as 0 at the time of normal operation and 1 at the time of failure detection (abnormal time), for example. Further, the information on the presence / absence of the bypass route of the upper layer line sent from the upper layer device is described in the effective upper layer backup line information table 912 as 0 for usable lines and 1 for unusable lines.

[0084] The result of subtracting the contents of the failure information table 901 detected by the lower hierarchy device from the contents of the failure information table 921 detected by the upper hierarchy device is described in the effective upper hierarchy active line information table 911. In this example, the cause of the failure is considered to be upstream of the lower hierarchy device 310 (on the left side of FIG. 9). Therefore, it can be seen that the section between the lower layer devices 310 and the upper layer devices 110 to 113 in the upper layer active lines 500 to 503 is originally a normal and usable line.

[0085] From the contents of these information tables 901,902,911,912,921, four case classification states are calculated. In the first case-separated state in which neither the upper-layer device nor the lower-layer device is subjected to the switching process, the value of the case-separated state calculation table is the same as that of the failure information table 921.

[0086] In the second case-separation state in which switching is performed only by the upper-layer device without switching in the lower-layer device, the case-separation state calculation table 932 contains the failure information table 921 for each upper-layer line unit. The value of the effective upper layer standby line information table 912 is compared with the value of the better value, that is, the smaller value is adopted in the example shown in FIG.

[0087] In the third case classification state in which switching is performed by the lower layer device and switching processing is not performed by the upper layer device, the case classification state calculation table 933 is set with the failure information table 902 for each upper layer line unit. Takes a logical OR with the effective upper layer active line information table 911.

[0088] In the fourth case classification state in which switching processing is performed by both the lower layer device and the upper layer device, the case classification state calculation table 934 calculates the third case classification state for each upper layer line unit. Compare the values in Table 933 and the effective upper layer standby line information table 912, and use the better value, that is, the smaller value in the example shown in FIG.

[0089] From the results of the four case classification state calculation tables 931 to 934 calculated in this way, the number of usable upper layer lines and the number of switches are calculated. The number of upper-tier lines that can be used is calculated by summing the number of normal lines that are described as usable for each upper-tier line in the case classification status table. In the example of FIG. 18, the maximum number of lines that can be used in these case-separated states is the fourth case-separated state in which switching processing is performed by both the lower-layer device and the upper-layer device. Is 4.

[0090] Since there is only one state extracted by the maximum number of usable lines state extraction unit 941, this result is adopted as it is by the minimum number of switching state extraction unit 942. In the fourth case classification state, the lower layer line route selection unit 430 of the lower layer device of the lower layer device 310 is activated, and the lower layer spare line 601 is selected. When the switching process in the lower layer device is completed, the request unit 950 for issuing the switching stop signal to the upper layer of the lower layer device is notified that it is no longer necessary to issue the switching stop signal to the upper layer of the lower layer device. The switching stop signal issuance requesting unit 950 to the upper layer of the lower layer device issues an instruction to the switching stop signal issuing units 480 to 483 to the upper layer of the lower layer device to release the switching stop signal. Then, each of the upper layer devices 110 to 113 starts the switching process in the upper layer.

Next, an example of FIG. 19 will be described. In this example, one upper layer line failure detection unit 462 of the lower layer device 310 detects a failure with respect to the active line 600 of the lower layer, and one upper layer of the lower layer device 310 with respect to the spare line 601 of the lower layer. The tier line failure detection unit 468 detects a failure, and the two upper tier line failure detection units 160 and 161 of the upper tier devices 110 to 113 detect a failure for the upper tier active lines 500 to 503, and the upper tier devices 110 to 113. All upper-layer line detour route presence / absence information signal issuing units 800 to 803 indicate that there is a detour route and indicate that all the spare lines of the upper layer can be used.

The failure information detected by these lower layer devices and the upper layer devices is described in the failure information table 901, 902, 921 as in the case shown in FIG. Further, the information on the presence / absence of the upper layer line detour route sent from the upper layer device is described in the effective upper layer backup line information table 912.

[0093] In the effective upper-level active line information table 911, the result of subtracting the contents of the failure information table 901 detected by the lower-level device from the contents of the failure information table 921 detected by the upper-level device is described. In this example, there is a failure factor in the section between the lower hierarchy device 310 and the upper hierarchy device 110 in the upper hierarchy active line 500, and even if the lower hierarchy device 310 switches and recovers the failure of the lower hierarchy line, the upper hierarchy It can be seen that the hierarchical working line 500 is an unusable line.

[0094] Similar to the example shown in FIG. 18, the four case classification states, that is, the failure information tables 931 to 934 are calculated. Then, the number of usable upper layer lines and the number of switches are calculated from the results of the case-by-case state calculation tables 931 to 934. In the example of FIG. 19, among these case-separated states, the maximum number of usable lines is in the second and fourth case-separated states, and the number is 4. Therefore, the maximum number of usable lines state extraction unit 941 extracts the second and fourth case classification states, and transmits the result to the minimum number of switching state extraction unit 942.

[0095] Regarding the calculation of the number of switches, in the case of this example, it is calculated as follows. In the second case classification state, the number of switches is the sum of the number of lines with failures described in the failure information table 901, and the number is 1. In the fourth case classification state, the number of switches is the number obtained by adding the number of switches 1 in the lower layer device to the number of lines with a failure described in the failure information table 902, and the number is 2. Therefore, the second case classification state is adopted in the switching number minimum state extraction unit 942.

[0096] In the second case classification state, switching is performed by the upper layer device without switching by the lower layer device. Therefore, the switching number minimum state extraction unit 942 informs the switching stop signal issuance requesting unit 950 of the lower layer device to the upper layer that it is no longer necessary to issue the switching stop signal to the upper layer of the lower layer device. Then, the switching stop signal issuing request unit 950 to the upper layer of the lower layer device issues an instruction to the switching stop signal issuing units 480 to 483 to the upper layer of the lower layer device to release the switching stop signal. Then, each of the upper layer devices 110 to 113 starts the switching process in the upper layer.

Finally, the example of FIG. 20 will be described. In this example, the two upper-tier line fault detection units 460 and 462 of the lower-tier device 310 detect a failure with respect to the lower-tier active line 600, and one higher level of the lower-tier device 310 with respect to the lower-tier spare line 601. The tier line failure detection unit 468 detects a failure, and the three upper tier line failure detection units 160, 161 and 162 of the upper tier devices 110 to 113 detect a failure for the upper tier active lines 500 to 503, and the upper tier devices 110 to 113. All upper-layer line detour route presence / absence information signal issuing unit 801 indicates that there is a detour route and indicates that all the spare lines of the upper layer can be used.

[0098] The failure information detected by these lower layer devices and the upper layer devices is described in the failure information table 901, 902, 921 as in the case shown in FIG. Further, the information on the presence / absence of the upper layer line detour route sent from the upper layer device is described in the effective upper layer backup line information table 912.

[0099] In the effective upper-level active line information table 911, the result of subtracting the contents of the failure information table 901 detected by the lower-level device from the contents of the failure information table 921 detected by the upper-level device is described. In this example, there is a failure factor in the section between the lower layer device 310 and the upper layer device 111 in the upper layer active line 501, and even if the lower layer device 310 switches and recovers from the failure of the lower layer line, the upper layer device 310 It can be seen that the hierarchical working line 501 is an unusable line.

[0100] Similar to the example shown in FIG. 18, the four case classification states, that is, the failure information tables 931 to 934 are calculated. Then, the number of usable upper layer lines and the number of switches are calculated from the results of the case-by-case state calculation tables 931 to 934. In the example of FIG. 20, among these case-separated states, the maximum number of usable lines is in the second and fourth case-separated states, and the number is 4. Therefore, the maximum number of usable lines state extraction unit 941 extracts the second and fourth case classification states, and transmits the result to the minimum number of switching state extraction unit 942.

[0101] In this case, the number of switchings is 2 in both cases. Therefore, the second and fourth case-separated states are still extracted by the switching number minimum state extraction unit 942. As described above, when there are a plurality of case-separated switching states in which the number of usable lines is the maximum and the number of switching is the minimum, the state in which the switching process is not performed in the lower layer device is adopted. This is because the time required for the entire switching process is shorter when the switching process is performed only on one layer than when the switching is performed on both layers. According to this selection rule, the switching number minimum state extraction unit 942 adopts the second case classification state. Then, as shown in FIG. 19, the switching number minimum state extraction unit 942 issues an instruction to the switching stop signal issuance requesting unit 950 to the upper layer of the lower layer device, and stops switching to the upper layer of the lower layer device. Release the switching stop signal of the signal output unit 480 to 483. Then, each of the upper layer devices 110 to 113 starts the switching process in the upper layer.

[0102] The upper-layer line failure detection units 460 to 468 of 310 of the lower-level device do not have to be exactly the same as those of the upper-layer line failure detection units 160 to 164 of the upper-layer devices 110 to 113, and the failure detection The method may be simplified or monitored in units of paths that are organized to some extent. However, in this case, even if there is a failure cause in front of the lower hierarchy device 310, the collation results do not match and it is processed as if the failure cause exists between the lower hierarchy device 310 and the upper hierarchy devices 110 to 113.

[0103] Further, when only the lower layer device 310 detects a failure and the upper layer devices 110 to 113 do not detect a failure, it is considered that communication is actually possible on the upper layer line, and the upper layer device is considered to be able to communicate. Priority is given to the results detected in 110 to 113. FIG. 16 shows a flowchart of the processing procedure of the cooperative switching determination unit for realizing the first embodiment described above.

[0104] So far, a network having a 1 + 1 type switching protocol in which one pair of active and one spare is paired and the same data is normally transferred has been described, but the embodiment of the present invention is 1: n. It can also be applied to networks with type switching protocols.

[0105] In the 1: n-type switching protocol, data is not transferred to the spare line under normal conditions, or one of n data is transferred under the condition that there is no spare line. .. In the 1: n type switching protocol, when the switching process starts, the same data as the active line to be relieved is transferred to the spare line called the bridge. After that, it shifts to the state of performing route selection so as to apply the signal of the backup line on the receiving side called the switch, and the switching process is completed. In the 1: n type switching protocol, the state of the standby line can be determined in this bridge state. That is, when the embodiment of the present invention is applied to a network having a 1: n-type switching protocol, when the cooperative switching determination unit 700 detects a failure in the active line 600 in the lower layer, the switching stop signal issuing unit 480 to When the switch stop signal to the upper layer is issued to 483, the lower layer line route selection unit 430 is instructed to shift to the bridge state. As a result, the cooperative switching determination unit 700 can determine the line status of the backup line 601 and then continue the switching process in the same manner as the 1 + 1 type switching protocol shown above. Further, since the embodiment of the present invention is not a network-dependent method such as a ring type or a mesh type, it can be similarly applied to these networks.

[0106] Except for some functions of the first embodiment, it is conceivable that the apparatus configuration is simplified.

[Example 2] A second embodiment of the present invention of a switching device having a cooperative switching determination unit will be described. A conceptual diagram relating to this embodiment is shown in FIG. Compared with the first embodiment, the second embodiment deletes the information transmission function from the upper layer to the cooperative switching determination unit as to whether the upper layer device has a detour route.

FIG. 11 shows a detailed configuration diagram of the apparatus according to the second embodiment of the present invention. This figure is a detailed representation of a part of FIG. 2 when the network in FIG. 2 is configured by the conventional lower layer devices and upper layer devices.

[0109] Compared with the first embodiment, the second embodiment deletes the function of transmitting the information on the presence / absence of the upper layer line detour route. The inter-layer cooperative switching determination unit 700 uses information as to whether or not the spare line of the upper layer is normal, as the determination material, instead of the information on the presence or absence of the detour route. Since the processing method may be the same as that of the first embodiment, the description thereof will be omitted here.

[Example 3] A switching device having a cooperative switching determination unit according to a third embodiment of the present invention will be described. FIG. 12 shows a conceptual diagram relating to the third embodiment of the present invention. Compared with the second embodiment, the third embodiment omits the function of transmitting the failure information of the upper layer line from the upper layer device to the inter-layer cooperative switching determination unit.

[0111] FIG. 13 shows a detailed configuration diagram of the apparatus according to the third embodiment of the present invention. This figure is a detailed representation of a part of FIG. 2 when the network in FIG. 2 is configured by the conventional lower layer devices and upper layer devices.

[0112] The cooperative switching determination unit 700 performs switching control of the lower layer device and cancellation of the switching stop signal from the failure information from the lower layer device without collating the failure information from the lower device 310 and the upper devices 100 to 103. Do.

[0113] What is different from the first embodiment is the method of determining the switching control performed by the cooperative switching determination unit. In the third embodiment, the failure information from the upper layer device is not transmitted. Therefore, to secure the maximum number of lines within the range in which failure information can be received, select the lower layer active line 600 or standby line 601 connected to the lower layer device 310, whichever has the better transmission quality. Will be done. In the third embodiment, since the cooperative switching determination unit 700 cannot obtain information from the upper layer device, it is not possible to minimize the number of switching processes including the upper layer device in this case.

[0114] As another method for selecting the active or standby line in the lower layer, there is a selection method in which a priority is given to each upper layer line unit that can be detected by the lower layer device 310, and the priority is taken into consideration. For example, in the situation shown in FIG. 18, there is no detour route in the upper layer for line 2. If the administrator of the lower hierarchy device knows this in advance, the priority is given to the line 2, that is, the lower hierarchy device 310 can use the line 2 by the upper hierarchy line failure detection units 460 to 468. You can also set the method of selecting the current or backup line of.

[0115] If the administrator can make such a setting, in the example of the failure state given in FIG. 18, as a result, in the same lower and upper layers as in the case of the first embodiment using the detour route presence / absence information. Switching process will be realized. Of course, the method of giving this priority may be decided by the administrator based on another judgment standard regardless of the information on the presence or absence of the detour route.

[0116] Once the cooperative switching determination unit 700 has determined the switching control method, the first step is to first perform switching in the lower layer, release the switching stop signal, and perform switching in the upper layer. It is the same as the case of the example of.

[Example 4] A switching device having a cooperative switching determination unit according to a fourth embodiment of the present invention will be described. The conceptual diagram according to the fourth embodiment of the present invention is the same as that of FIG. 10 of the second embodiment. Compared with the second embodiment, the fourth embodiment omits the upper hierarchy failure detection unit of the lower hierarchy device.

[0118] FIG. 14 shows a detailed configuration diagram of the apparatus according to the fourth embodiment of the present invention. This figure is a detailed representation of a part of FIG. 2 when the network in FIG. 2 is configured by the conventional lower layer devices and upper layer devices.

[0119] In the fourth embodiment, when the geographical distance between the upper layer device and the lower layer device is short, for example, when both devices exist in the same station building, or when the upper layer device and the lower layer device are connected to each other. It is effectively applied when the reliability of the parts or lines required for the above is high and the probability of failure occurring is clearly low compared to other sections.

[0120] The cooperative switching determination unit 700 performs switching control of the lower layer device 310 and cancellation of the switching stop signal based on the failure information from the upper layer line failure detection units 160 to 164 of the upper layer devices 110 to 113. The switching control determined by the cooperative switching determination unit is determined based on ensuring the maximum number of normal lines that can be received by the upper layer device. Similar to the other embodiments, while the lower layer device is executing the switching process, the switching in the upper layer device is stopped by issuing a switching stop signal.

[0121] As described above, according to the embodiment of the present invention, when there are unique switching functions in different layers, instead of stopping either switching function, switching utilizing each other's characteristics is performed. It is possible to use it properly according to.

[0122] That is, by using the switching function of both layers depending on the situation, it is possible to secure the maximum number of normal lines that can be finally received by the upper layer device. It is also possible to determine the device to be switched so that the number of switching processes is minimized. In particular, when switching between both layers, the switching process can be reliably performed from the lower layer device first, so that the exchange of switching protocols can be reduced, which is effective from the viewpoint of reliability.

[0123] Further, the total switching processing time when the switching function of both layers is used can be remarkably shortened. FIG. 15 shows a time chart of the switching time according to the embodiment of the present invention when the upper layer is ATM when the holdoff time is 500 ms and the lower layer is SONET (switching processing time 50 ms). Compared with the method of FIG. 7 shown as a comparative example, in the conventional method, it took about 550 ms to complete the switching process of the two layers, but according to the embodiment of the present invention, it takes about 100 ms.

[0124] The techniques related to the examples of the present invention are listed below.

1. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. It is connected to a network having an upper layer device having a line switching means of the line, and using the failure information of the upper layer communication line and the failure information of the lower layer communication line at the time of detecting a line failure, the upper layer device and the lower layer device are used. A communication device characterized in that it is configured to perform switching processing of each of the line switching means in cooperation with each other.

2. The communication device has a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and are connected via an interface. The communication device according to 1. above, which is characterized by being a device.

3. The cooperative switching process is characterized in that the switching process of the line switching means of the upper layer device is started when it is determined that the switching process of the lower layer device of the lower layer device is completed. The communication device described in 1.

4. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. It is connected to a network having an upper layer device having a line switching means of the line, and using the failure information of the upper layer communication line and the failure information of the lower layer communication line at the time of detecting a line failure, the upper layer device and the lower layer device A communication device having a means for disaster recovery that specifies in what order the line switching means should be switched.

5. The means is a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and connected to each other via an interface. The communication device according to 4. above.

6. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. It is connected to a network having an upper layer device having a line switching means of the line, and when a line failure is detected, failure information of the upper layer communication line and failure information of the lower layer communication line are collected, and the collected information is used for upper layer communication. Identify one or more failure-occurring lines and failure-occurring parts of the line or lower-tier communication line, and use the specific information to identify the upper-tier device and lower-tier device that should be line-switched for the purpose of failure recovery. , A communication device having a means for specifying in what order and timing the line switching means of the upper layer device and the lower layer device should be switched.

7. The means is a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and connected to each other via an interface. The communication device according to 6. above.

8. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. When connected to a network having a higher-level device having a line switching means of the line and detecting a line failure due to one of the lower-level devices, a notification of stop of line switching processing execution of the higher-level device is sent to the upper-level device. Then, using the collected failure information of the upper layer communication line and the failure information of the lower layer communication line, identify one or more failure occurrence lines and failure occurrence parts of the upper layer communication line or the lower layer communication line. , The line switching process of the lower layer device and the line switching process of the upper layer device are configured to be performed in cooperation with each other by using the collected failure information of the upper layer communication line and the failure information of the lower layer communication line. A communication device characterized by.

9. When the lower layer device detects a line failure, the failure is detected after the upper layer device is notified of the stop of the line switching process execution of the upper layer device. The communication device according to 8. above, which is configured to notify a higher-level device.

10. The communication device has a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and are connected via an interface. The communication device according to 8. above, which is characterized by being a device.

[0135] 11. A lower layer device that is connected to a lower layer communication line and an upper layer communication line and has a line switching means for the lower layer communication line, and a line switching means for the upper layer communication line that is connected to the upper layer communication line. When connected to a network with a higher-level device and one of the lower-level devices detects a line failure, a stop notification of line switching processing execution of the higher-level device is sent to the upper-level device and collected. Using the failure information of the upper layer communication line and the failure information of the lower layer communication line, identify one or more failure occurrence lines and failure occurrence parts of the upper layer communication line or the lower layer communication line, and which lower layer If there is no failure in the communication line and it is specified that there is a failure in one of the upper layer communication lines, the stop notification of the line switching process execution of the upper layer device is canceled for the upper layer device. If it is determined that a failure has occurred in one of the lower layer communication lines, the maximum number after the failure recovery process is executed using the failure information of the upper layer communication line and the failure information of the lower layer communication line. In order to enable higher-level communication lines, or to preferentially use higher-priority lines than lower-priority lines, or to maximize the number of signal lines to be restored. Identifyes the first option of which of the line switching means each of the plurality of upper layer devices or lower layer devices should be switched, and in the line switching process by the first option, the upper layer device and the lower layer device. When both line switching processes in the layered device are included, the line switching process in the lower layer device is performed first, and then the stop notification of the line switching process execution of the upper layer device is canceled for the upper layer device. A communication device comprising means for performing.

12. When the lower-level device detects a line failure, the failure is detected after the higher-level device is notified to stop the line switching process execution. The communication device according to 11. above, which is configured to notify a higher-level device.

13. The means is a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and connected to each other via an interface. The communication device according to 11. above.

[0138] 14. The first and second upper layer devices and the first to fourth lower layer devices, each of which has a line switching means, are provided, and the first and second upper layer devices are interchangeable with each other. First and second lower tier communication that is connected via two upper tier communication lines, the first and second lower tier devices can be switched between each other, and one or more upper tier communication lines are multiplexed. Connected via a line, the third and fourth lower layer devices can be switched to each other, and are connected via a third and fourth lower layer communication line in which one or more upper layer communication lines are multiplexed. Then, between the first upper layer device and the first lower layer device and between the second upper layer device and the second lower layer device via the first upper layer communication line. The second upper layer communication line is connected between the first upper layer device and the third lower layer device and between the second upper layer device and the fourth lower layer device. When the lower layer device detects a line failure, the upper layer device is notified to stop the line switching processing execution, and the failure information of the upper layer communication line and the lower layer communication are sent. Using the line failure information, identify one or more failure-occurring lines and failure-occurring sites of the upper-layer communication line or lower-layer communication line, and there is no failure in any of the lower-layer communication lines, and either If it is identified that a failure has occurred in the upper layer communication line, the stop notification of the line switching process execution of the upper layer device is canceled for the upper layer device, and one of the lower layer communication lines fails. If it is identified that an occurrence has occurred, the maximum number of upper-tier communication lines can be used after the failure recovery process is executed, based on the failure information of the upper-tier communication line and the failure information of the lower-tier communication line. Or, in order to preferentially use a line having a higher priority than a line having a lower priority, or to maximize the number of signal lines to be restored, a plurality of upper layer devices or lower layer devices In the line switching process according to the first option, the first option of which of the line switching means to be switched is specified.When both the line switching process in the upper layer device and the line switching process in the lower layer device are included, the line switching process in the lower layer device is performed first, and then the stop notification of the line switching process execution of the upper layer device is canceled. A communication system characterized by having a first means for a layered device.

15. When there are a plurality of the first options, the second option that minimizes the number of line switchings during the failure recovery process is specified from the first options, and the second option is specified. If there are multiple options, and there is a line switching combination that does not involve line switching in the lower layer device, select that combination as the third option and select the upper layer device. The stop notification of the line switching process execution is canceled for the upper layer device, and if the third option does not exist, the line switching process is performed by the lower layer device that needs to be switched, and then the upper layer device is performed. 14. The communication system according to 14. above, wherein the first means is configured so as to cancel the stop notification of the line switching process execution of the above.

16. When the lower-level device detects a line failure, the failure is detected after the higher-level device is notified to stop the line switching process execution. The communication system according to 14. above, which is configured to notify a higher-level device.

[0141] 17. Each of the lower layer devices has a plurality of lower layer devices and a plurality of higher layer devices belonging to a higher layer than the lower layer device, and one or more upper layer communication lines are multiplexed between the lower layer devices. It is connected via the lower layer communication line, and the upper layer devices are connected via the upper layer communication line via the lower layer device. If any of the lower layer devices detects a line failure, the upper layer device is connected. The stop notification of the line switching process execution of the layer device is sent to the upper layer device, and based on the failure information of the upper layer communication line and the failure information of the lower layer communication line, the upper layer communication line or the lower layer communication line is selected. If one or more failure-occurring lines and failure-occurring sites are specified, no failure has occurred in any of the lower-level communication lines, and it is identified that a failure has occurred in one of the upper-level communication lines, the upper level When the stop notification of the line switching process execution of the layer device is canceled for the upper layer device and it is identified that a failure has occurred in one of the lower layer communication lines, the failure information of the upper layer communication line and the lower layer communication line are detected. Based on the fault information of the tier communication line, in order to enable the maximum number of higher tier communication lines after the failure recovery process is executed, or to preferentially use the higher priority line than the lower priority line. In order to obtain the maximum number of signal lines to be restored, or in order to maximize the number of signal lines to be restored, the first option of which of the line switching means possessed by the plurality of upper layer devices or lower layer devices should be switched is selected. When the line switching process according to the first option includes both the line switching process in the upper layer device and the line switching process in the lower layer device, the line switching process in the lower layer device is performed first, and then the upper layer device is used. A communication system characterized by having a first means for canceling a stop notification of line switching processing execution of a device to a higher-level device.

[0142] 18. If there is no failure in any of the lower layer communication lines and it is specified that a failure has occurred in any of the upper layer communication lines, the line switching process of the upper layer device is executed. The communication system according to 17. above, which is configured to notify the upper layer device that the failure has been detected after canceling the stop notification to the upper layer device.

[0143] 19. The first and second upper layer devices and the first to fourth lower layer devices, each of which has a line switching means, are provided, and the first and second upper layer devices are interchangeable with each other. First and second lower tier communication that is connected via two upper tier communication lines, the first and second lower tier devices can be switched between each other, and one or more upper tier communication lines are multiplexed. Connected via a line, the third and fourth lower layer devices can be switched to each other, and are connected via a third and fourth lower layer communication line in which one or more upper layer communication lines are multiplexed. Then, between the first upper layer device and the first lower layer device and between the second upper layer device and the second lower layer device via the first upper layer communication line. The second upper layer communication line is connected between the first upper layer device and the third lower layer device and between the second upper layer device and the fourth lower layer device. When the lower layer device detects a line failure, the upper layer device is notified to stop the line switching processing execution, and the failure information of the upper layer communication line and the lower layer communication are sent. Based on the line failure information, one or more failure-occurring lines and failure-occurring sites of the upper-layer communication line or the lower-layer communication line are identified, and no failure occurs in any of the lower-layer communication lines, and either one If it is identified that a failure has occurred in the upper layer communication line, the stop notification of the line switching process execution of the upper layer device is canceled for the upper layer device, and one of the lower layer communication lines fails. If it is identified that an occurrence has occurred, the maximum number of upper-tier communication lines can be used after the failure recovery process is executed, based on the failure information of the upper-tier communication line and the failure information of the lower-tier communication line. Or, in order to preferentially use a line having a higher priority than a line having a lower priority, or to maximize the number of signal lines to be restored, a plurality of upper layer devices or lower layer devices Each of the communication systems has a first means for specifying a first option of which of the line switching means to be switched.Stem.

20. When the line switching process according to the first option includes both the line switching process in the upper layer device and the line switching process in the lower layer device, the line switching process in the lower layer device is performed first, and then the line switching process is performed. The communication system according to 19. above, characterized in that the stop notification of the line switching process execution of the upper layer device is canceled for the upper layer device.

21. When there are a plurality of the first options, the second option that minimizes the number of line switchings during the failure recovery process is specified from the first options, and the second option is specified. If there are multiple options, and there is a line switching combination that does not involve line switching in the lower layer device, select that combination as the third option and select the upper layer device. The stop notification of the line switching process execution is canceled for the upper layer device, and if the third option does not exist, the line switching process is performed by the lower layer device that needs to be switched, and then the upper layer device is performed. 19. The communication system according to 19. Above, wherein the first means is configured to cancel the stop notification of the line switching process execution of the above-mentioned 1.

22. When the lower layer device detects a line failure, the failure is detected after the upper layer device is notified of the stop of the line switching process execution of the upper layer device. The communication system according to 19. above, characterized in that it is configured to notify a higher-level device.

[0147] 23. Each of the lower layer devices has a plurality of lower layer devices and a plurality of higher layer devices belonging to a higher layer than the lower layer device, and one or more upper layer communication lines are multiplexed between the lower layer devices. It is connected via the lower layer communication line, and the upper layer devices are connected via the upper layer communication line via the lower layer device. If any of the lower layer devices detects a line failure, the upper layer device is connected. The stop notification of the line switching process execution of the layer device is sent to the upper layer device, and based on the failure information of the upper layer communication line and the failure information of the lower layer communication line, the upper layer communication line or the lower layer communication line is selected. If one or more failure-occurring lines and failure-occurring sites are specified, no failure has occurred in any of the lower-level communication lines, and it is identified that a failure has occurred in one of the upper-level communication lines, the upper level When the stop notification of the line switching process execution of the layer device is canceled for the upper layer device and it is identified that a failure has occurred in one of the lower layer communication lines, the failure information of the upper layer communication line and the lower layer communication line are detected. Based on the fault information of the tier communication line, in order to enable the maximum number of higher tier communication lines after the failure recovery process is executed, or to preferentially use the higher priority line than the lower priority line. In order to obtain the maximum number of signal lines to be restored, or in order to maximize the number of signal lines to be restored, the first option of which of the line switching means of the plurality of upper layer devices or the lower layer devices should be switched is selected. A communication system characterized by having a first means of identifying.

24. When the line switching process according to the first option includes both the line switching process in the upper layer device and the line switching process in the lower layer device, the line switching process in the lower layer device is performed first, and then. The communication system according to 23. above, which is configured to cancel the stop notification of the line switching process execution of the upper layer device to the upper layer device.

[0149] 25. If there is no failure in any of the lower layer communication lines and it is specified that a failure has occurred in any of the upper layer communication lines, the line switching process of the upper layer device is executed. The communication system according to 23. above, wherein the communication system is configured to notify the upper layer device that the failure has been detected after canceling the stop notification to the upper layer device.

26. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. If it is connected to a network with a higher-level device having line switching means and it is judged that failure relief cannot be achieved by switching the line of the lower-level device, the upper layer goes to a detour route that does not pass through the lower-level device. A communication device having a means for notifying the upper layer device of an instruction to switch the line switching means of the device.

27. The communication device has a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and are connected via an interface. The communication device according to 26. Above, which is characterized by being a device.

28. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. It is connected to a network having an upper layer device having a line switching means of the line, and when a line failure is detected, an upper layer communication line or a lower layer communication line is based on the failure information of the upper layer communication line and the failure information of the lower layer communication line. One or more of the failure-occurring lines and failure-occurring sites are identified, and failure recovery is performed based on the specific information and information on whether or not there is a detour route that does not pass through the lower-level device when a failure occurs in the lower-level device. When the upper layer device and lower layer device to be line-switched for the purpose are specified, it is judged that failure relief cannot be achieved by switching the line of the lower layer device, and there is a detour route that does not pass through the lower layer device. The communication device is characterized by having means for notifying the upper layer device of an instruction to switch the line switching means of the upper layer device to the detour route.

29. The communication device has a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and are connected via an interface. The communication device according to 28. above, characterized in that it is a device.

30. The communication device according to 28. above, wherein the failure information of the upper layer communication line is collected from at least one of the upper layer device and the lower layer device.

31. The communication device according to 28. above, wherein the instruction is to release a switching stop signal to the upper layer device.

32. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. Information on whether or not a detour line route that does not pass through a specific lower layer device can be secured by switching the line switching means of the upper layer device, which is connected to the network having the upper layer device having the line switching means of the line. Using the failure information of the tier communication line and the failure information of the lower tier communication line, one or more failure occurrence lines and failure occurrence parts of the upper tier communication line or the lower tier communication line are identified at the time of line failure detection, and the identification thereof. Based on the information, identify the upper-level device and lower-level device that should be line-switched for the purpose of disaster recovery, specify which of the higher-level device and lower-level device line switching means to switch, and switch. When the power line switching means exists in the upper layer device and the lower layer device, respectively, there is a means for instructing the switching of the line switching means of the lower layer device to be prioritized over the switching of the line switching means of the upper layer device. A communication device characterized by.

33. The means is a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and connected to each other via an interface. The communication device according to 32.

34. A lower tier device connected to a lower tier communication line and a higher tier communication line and having a line switching means for the lower tier communication line, and a lower tier communication line connected to the upper tier communication line and the upper tier communication thereof. If it has a higher-level device that has line switching means and it is judged that failure relief cannot be achieved by switching the line of the lower-level device, the line of the upper-level device is taken to a detour route that does not pass through the lower-level device. A communication system comprising means for notifying the upper layer device of an instruction for switching switching means.

35. The means is a cooperative switching device or a lower layer device having a cooperative switching function, or the cooperative switching means and the lower layer device are separately configured and connected to each other via an interface. The communication system according to 34.

36. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. It has an upper-layer device having a line switching means of the line, and when a line failure is detected, it is one of the upper-layer communication line or the lower-layer communication line based on the failure information of the upper-layer communication line and the failure information of the lower-layer communication line. One or more failure-occurring lines and failure-occurring sites are identified, and the line is used for the purpose of failure recovery based on the specific information and information on whether or not there is a detour route that does not pass through the lower-level device when a failure occurs. If the upper layer device and lower layer device to be switched are specified, it is judged that failure relief cannot be achieved by switching the line of the lower layer device, and there is a detour route that does not pass through the lower layer device. A communication system comprising means for notifying the upper layer device of an instruction to switch the line switching means of the upper layer device to the detour route.

37. The communication system according to 36. Above, wherein the failure information of the upper layer communication line is collected from at least one of the upper layer device and the lower layer device.

38. The communication system according to 36. Above, wherein the instruction is a release of a switching stop signal to a higher-level device.

39. A lower layer device connected to a lower layer communication line and a higher layer communication line and having a line switching means for the lower layer communication line, and a lower layer communication line connected to the upper layer communication line and the upper layer communication thereof. Information on whether or not a detour line route that does not pass through a specific lower layer device can be secured by switching the line switching means of the upper layer device and having an upper layer device having a line switching means of the line, an upper layer communication line At the time of line failure detection, one or more failure-occurring lines and failure-occurring sites of the upper-layer communication line or lower-layer communication line are identified by using the failure information and the failure information of the lower-layer communication line, and based on the specific information. Identify the upper-tier device and lower-tier device that should be line-switched for the purpose of disaster recovery, specify which of the upper-tier device and lower-tier device line switching means to switch, and switch the line to be switched. When the means are present in the upper layer device and the lower layer device, respectively, it is characterized by having a means for instructing the switching of the line switching means of the lower layer device to be prioritized over the switching of the line switching means of the upper layer device. Communication system.

[Effect of the Invention] According to the present invention, cooperative switching between layers is possible.

BRIEF DESCRIPTION OF THE DRAWINGS [FIG. 1] FIG. 1 is a diagram for explaining an embodiment of the present invention, showing the concept of an upper layer line section and a lower layer line section.

FIG. 2 is a diagram for explaining an embodiment of the present invention, and is a diagram showing a network configuration when an upper layer and a lower layer each have a switching unit.

FIG. 3 is a diagram for explaining an embodiment of the present invention, and is a diagram for explaining a process of switching between an upper layer and a lower layer when a failure occurs in a lower section.

FIG. 4 is a diagram for explaining a comparative example of the present invention, and is a diagram for explaining alarm transfer from a lower layer to an upper layer.

FIG. 5 is a diagram for explaining a comparative example of the present invention, and is a diagram for explaining a concept of an alarm forwarding method between an upper layer and a lower layer.

FIG. 6 is a diagram for explaining a comparative example of the present invention, and is a diagram showing a device configuration related to switching processing between upper and lower layers.

FIG. 7 is a diagram for explaining a comparative example of the present invention, and is a diagram showing a time chart of switching processing between upper and lower layers.

FIG. 8 is a diagram for explaining an embodiment of the present invention, and is a conceptual diagram of switching processing between upper and lower layers.

FIG. 9 is a diagram for explaining an embodiment of the present invention, and is a diagram showing a configuration of a switching device having a cooperative switching determination unit.

FIG. 10 is a diagram for explaining another embodiment of the present invention, and is a conceptual diagram of switching processing between upper and lower layers.

FIG. 11 is a diagram for explaining another embodiment of the present invention, and is a diagram showing a configuration of a switching device having a cooperative switching determination unit.

FIG. 12 is a diagram for explaining still another embodiment of the present invention, and is a conceptual diagram of a switching process between upper and lower layers.

FIG. 13 is a diagram for explaining still another embodiment of the present invention, and is a diagram showing a configuration of a switching device having a cooperative switching determination unit.

FIG. 14 is a diagram for explaining a fourth embodiment of the present invention, and is a diagram showing a configuration of a switching device having a cooperative switching determination unit.

FIG. 15 is a diagram for explaining an embodiment of the present invention, and is a diagram showing a time chart of switching processing.

FIG. 16 is a diagram for explaining a first embodiment of the present invention, and is a diagram showing a flowchart of processing performed by a cooperative switching determination unit.

FIG. 17 is a diagram for explaining a first embodiment of the present invention, and is a functional block diagram of a cooperative switching determination unit.

FIG. 18 is a diagram showing an example of processing of a cooperative switching determination unit when a failure occurs.

FIG. 19 is a diagram showing an example of processing of a cooperative switching determination unit when a failure occurs.

FIG. 20 is a diagram showing an example of processing of a cooperative switching determination unit when a failure occurs.

FIG. 21 is a diagram for explaining an embodiment of the present invention and showing a network configuration.

[Explanation of Codes] 100 to 114: Upper layer devices 120 to 129: Upper layer line signal processing units of upper layer devices 130 to 138: Upper layer line signal reception processing units of upper layer devices 160 to 164: Upper layer devices Upper layer line failure detection unit 220 to 230: Upper layer line route selection unit of upper layer device 300 to 311: Lower layer device 330 to 331: Lower layer line signal reception processing unit of lower layer device 340 to 343: Lower layer device Upper layer line signal transmission processing unit 360 to 361: Lower layer line failure detection unit 420 to 431 of lower layer device: Lower layer line route selection unit 440 to 451 of lower layer device: Multiplex separation unit 460 to 468 of lower layer device : Upper layer line failure detection unit of lower layer device 470 to 473: Alarm transfer signal issuing unit to upper layer of lower layer device 480 to 483: Switching stop signal issuing unit to upper layer of lower layer device 500 to 504: Upper layer Hierarchical line 600 to 603: Lower tier line 700: Inter-layer cooperative switching judgment unit 710: Lower tier line switching judgment unit of lower tier device 720: Upper tier line switching judgment unit of upper tier device 750: Alarm transfer judgment to higher tier Part 800 to 803: Upper layer line detour route presence / absence information signal issuing part 900: Failure information collection part of failure information detected by lower layer device 901: Failure information table detected by lower layer device related to lower layer active line 902: Lower level Failure information table detected by the lower layer device related to the hierarchical backup line 910: Verification unit of failure information detected by the lower layer device and the upper layer device respectively 911: Effective upper layer active line information table 912: Effective upper layer spare line information Table 920: Failure information collection unit for failure information detected by the upper layer device 921: Failure information table detected by the upper layer device related to the upper layer active line 930: Case classification status calculation unit 931: Case classification status calculation table 1932: Case Divided status calculation table 2933: Case division status calculation table 3934: Case division status calculation table 4940: Case division status selection unit 941: Number of available lines Maximum status extraction unit 942: Number of switching minimum status extraction unit 950:Switching stop signal issuance request unit to the upper layer of the lower layer device 960: An interrupt signal line to the switching stop signal issuance request unit to the upper layer of the lower layer device.