JP6323282B2 - Line termination equipment - Google Patents

Description

  The present invention relates to a line termination device.

  ITU-T (International Telecommunication Union Telecommunication standardization Sector) recommendation In an ATM network in which communication is performed using ATM (Asynchronous Transfer Mode) compliant with 361, communication equipment on the provider side and communication equipment on the subscriber (user) side (hereinafter referred to as “user equipment”). For example, a line termination device such as an ONU (Optical Network Unit) or a DSU (Digital Service Unit) is used.

  In an ATM network in which this type of line terminator is used, an ITU-T recommendation I.I. An OAM (Operation Administration and Maintenance) cell compliant with 610 is used.

  As a technique using an OAM cell in an ATM network, Patent Document 1 discloses ITU-T Recommendation I.D. An ATM alarm processing method is disclosed that uses a segment VP-AIS (Virtual Path-Alarm Indication Signal) cell conforming to 610 to manage a failure in a VP segment of an ATM network. In this technology, the network management device sets whether or not to transfer a segment VP-AIS cell in the information area, including the target VPI value in the VPI (Virtual Path Identifier) for the transmission device in the network. The specific cell in which the information is stored is input to the transmission apparatus constituting the VP segment. Further, in this technique, when each transmission device constituting the VP segment detects the specific cell, the setting information in the information area is stored, and the specific cell is sequentially transferred to the subsequent transmission device until reaching the end of the segment. To do.

Japanese Patent Laid-Open No. 11-346225

  Incidentally, the above-described line termination device is generally provided with a detachable network interface card (hereinafter referred to as “ATM termination card”) to which user equipment is connected. The ATM termination card has a function of generating a VP-AIS cell when the ATM termination card is in a disconnected state in which an input signal from the user device is not received. Specific examples of the case where the input signal from the user device is in a disconnected state include a disconnection of a communication cable connecting the user device and the ATM termination card, or a state in which the power of the user device is turned off. Can be mentioned.

  However, the VP-AIS cell does not include information for identifying the transmission source. For this reason, in the line termination device, is the VP-AIS cell input from the ATM termination card a VP-AIS cell transmitted from the user equipment or a VP-AIS cell generated by the ATM termination card? Cannot be determined. Therefore, there is a problem in that the line termination device cannot detect that the input signal from the user device is in a disconnected state. This problem is not limited to the ATM network, but may be a problem that may occur in a network in which information that does not include information for identifying the transmission source is transmitted.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a line terminator capable of accurately detecting that an input signal from a user device is in a disconnected state.

  In order to achieve the above object, when a user equipment is connected and the input signal from the user equipment is in a normal state, the line termination device of the present invention can receive information inputted from the user equipment at a first communication speed. When the input signal is in a disconnected state, the failure management information is generated at a second communication speed higher than the first communication speed and is output from the connection device that outputs the information. A determination unit that determines whether or not the input signal is in a disconnected state by determining whether or not a communication speed is equal to or higher than a predetermined speed higher than the first communication speed, and the input by the determination unit And an output unit that outputs information indicating that the input signal is in a disconnected state when it is determined that the signal is in a disconnected state.

  According to the present invention, it is possible to accurately detect that the input signal from the user device is in a disconnected state.

It is a schematic block diagram of the communication system which concerns on embodiment. It is a functional block diagram which shows the functional structure of the line termination apparatus which concerns on embodiment. It is a functional block diagram which shows the functional structure of the filter part which concerns on embodiment. It is a timing chart with which it uses for description of the output process of the cell by the ATM termination | terminus card | curd which concerns on embodiment. It is a schematic diagram which shows an example of the cell format of the OAM cell which concerns on embodiment. It is a state transition diagram which shows an example of the state transition of the determination part which concerns on embodiment. It is a schematic diagram which shows an example of the cell format of the failure notification cell which concerns on embodiment. It is a timing chart with which it uses for description of the process by the ATM port in the normal time which concerns on embodiment. It is a timing chart with which it uses for description of the process by the ATM port when the input signal which concerns on embodiment becomes a disconnection state. It is a schematic diagram with which it uses for description of the process of the multiplexing by the multiplexing part which concerns on embodiment. It is a schematic diagram which shows an example of a structure of the connection table which concerns on embodiment. It is a flowchart which shows the flow of the cell output process of the line termination apparatus which concerns on embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. Here, a case where the present invention is applied to a line terminating device to which user equipment in an ATM network is connected will be described.

  First, the configuration of the communication system 10 according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, a communication system 10 according to the present embodiment includes a plurality (two in the present embodiment) of line termination devices 12A and 12B. In the following description, when it is not necessary to distinguish between the line termination devices 12A and 12B, the alphabet at the end of the code is omitted.

  The line termination device 12A according to the present embodiment includes ATM termination cards 14A to 14D that are examples of the connection device of the present invention that can be attached to and detached from the line termination device 12A. The line termination device 12B according to the present embodiment also includes ATM termination cards 14E to 14H that can be attached to and detached from the line termination device 12B. User equipments 16A to 16D are connected to the ATM terminal cards 14A to 14D of the line terminal device 12A on a one-to-one basis, and user equipments 16E to 16H are connected to the ATM terminal cards 14E to 14H of the circuit terminal device 12B. Each is connected one-to-one. Hereinafter, when it is not necessary to distinguish between the ATM end cards 14A to 14H, the alphabet at the end of the code is omitted. In the following description, when there is no need to distinguish between the user devices 16A to 16H, the alphabet at the end of the code is omitted.

  Specific examples of the user device 16 include a terminal such as a server / computer and a network device such as a router that can communicate by ATM.

  On the other hand, the line terminating device 12 according to the present embodiment is also connected to the ATM network 18. With the above configuration, each user device 16 can perform ATM communication via the connected line termination device 12.

  Although FIG. 1 shows a case where four user devices 16 are connected to one line terminating device 12, the present invention is not limited to this. The number of user equipments 16 connected to one line terminating device 12 may be set as appropriate according to the required communication speed.

  Moreover, although FIG. 1 shows the case where one user equipment 16 is connected to one ATM terminal card 14, it is not limited to this. For example, a plurality of connection points (ports) may be provided in one ATM terminal card 14, and a plurality of user devices 16 may be connected to one ATM terminal card 14.

  Next, with reference to FIG. 2 and FIG. 3, a functional configuration of the line termination apparatus 12 according to the present embodiment will be described.

  As shown in FIG. 2, the line termination apparatus 12 according to the present embodiment includes an ATM port 20A to 20D, a multiplexing unit 28, a failure notification cell detection unit 30, a second generation unit 32, a connection table 34, and an output unit 36. It has. Note that the numbers in parentheses of the ATM ports 20A to 20D in FIG. 2 indicate the port numbers of the ATM ports in which the numbers are described. The ATM ports 20B to 20D are similar in configuration to the ATM port 20A, and are not shown in FIG. Further, in the following, when it is not necessary to distinguish and describe the ATM ports 20A to 20D, the alphabet at the end of the code is omitted.

  The ATM ports 20A to 20D are provided on a one-to-one basis on the ATM end cards 14A to 14D, respectively, and ATM cells (hereinafter simply referred to as “cells”) output from the corresponding ATM end cards 14 are input thereto.

  When the input signal from the connected user equipment 16 is in a normal state, the ATM termination card 14 according to the present embodiment converts the cell input from the user equipment 16 to the first communication speed (in this embodiment, As an example, the data is output at 25.6 Mbps (Megabits per second). On the other hand, the ATM termination card 14 is an example of the failure management information of the present invention when the input signal from the connected user device 16 is in a disconnected state (hereinafter referred to as “LOS” (Loss Of Signal)). A VP-AIS cell (in this embodiment, an end-to-end F4 flow OAM cell) is generated at a second communication speed (in this embodiment, 155.52 Mbps as an example) faster than the first communication speed. Output.

  Specifically, the ATM termination card 14 according to the present embodiment, at the time of LOS, sends VP-AIS cells to all destinations, that is, to VPC (Virtual Path Connection) VPI of 0 to 255, respectively. Generate and output. Therefore, in this case, the ATM end card 14 generates and outputs 256 VP-AIS cells.

  The ATM termination card 14 according to the present embodiment generates and outputs one set of 256 VP-AIS cells per second. Further, as shown in FIG. 4, the ATM terminal card 14 also generates and outputs an empty cell (hereinafter referred to as “empty cell”) in order to adjust the communication speed for outputting the cell. FIG. 4 is a timing chart for explaining cell output processing by the ATM termination card 14 and shows cells output from the ATM termination card 14 per second. The upper cell row in FIG. 4 indicates a normal cell, and the lower cell row in FIG. 4 indicates a LOS cell. Also, the dotted line cells in FIG. 4 indicate empty cells, and the solid line cells indicate cells to which the value of VPI described in the cell is the destination.

  As an example, as shown in FIG. 4, when normal, cells addressed to a VPC with a VPI of 0 (zero) at 25.6 Mbps are sequentially input from the user equipment 16, and the cells are output from the ATM termination card 14 at 25.6 Mbps. Is done. On the other hand, at the time of LOS, as described above, one set of VP-AIS cells destined for the VPC having a VPI of 0 to 255 is output from the ATM terminal card 14 at 155.52 Mbps.

  That is, when normal, the ATM terminal card 14 adjusts the communication speed to 155.52 Mbps, which is the communication speed between the ATM terminal card 14 and the line terminal device 12 (more specifically, the ATM port 20). Therefore, in the example illustrated in FIG. 4, five empty cells are output for one cell input from the user equipment 16. On the other hand, at the time of LOS, the ATM end card 14 sequentially outputs VP-AIS cells addressed to VPCs having VPI of 0 to 255, and then outputs empty cells for the remaining one second. As a result, the cell input from the user equipment 16 is output from the ATM termination card 14 at 25.6 Mbps, and the communication speed between the ATM termination card 14 and the line termination device 12 is 155.52 Mbps. The cell format of the empty cell is not particularly limited, and a cell format determined in advance as an empty cell may be used.

  On the other hand, as shown in FIG. 2, the ATM port 20 according to the present embodiment includes a filter unit 22, a first generation unit 24, and a selector 26.

  As shown in FIG. 3, the filter unit 22 according to the present embodiment includes a FIFO (First In First Out) unit 22A, an AIS cell detection unit 22B, a window unit 22C, a determination unit 22D, and a timer unit 22E. .

  The cells output from the ATM termination card 14 are input to the FIFO unit 22A and the AIS cell detection unit 22B.

  The FIFO unit 22A according to the present embodiment is a FIFO memory for delaying an input cell. In the present embodiment, as an example, the capacity of 4 cells, that is, 53 bytes × 4 = 212 bytes. Has capacity. In the present embodiment, it is assumed that 1 byte = 8 bits.

  The AIS cell detector 22B according to the present embodiment detects that the input cell is a VP-AIS cell.

  Here, a detection method of the VP-AIS cell by the AIS cell detection unit 22B will be described. First, as shown in FIG. A cell format is defined at 610. For OAM cells, ITU-T Recommendation I.I. Since it is defined in 610, the description here is omitted.

  In the VP-AIS cell, the value of the VCI (Virtual Channel Identifier) field (hereinafter referred to as “VCI value”) in the header of the cell format shown in FIG. 5 is “4”, and the value of the OAM cell type field (hereinafter referred to as “VCI value”). ITU-T recommendation that “OAM cell type value”) is “0001” indicating failure management and the value of the function type field (hereinafter referred to as “function type value”) is “0000” indicating AIS. I. 610.

  Accordingly, the AIS cell detection unit 22B detects that the cell is a VP-AIS cell by referring to the VCI value, the OAM cell type value, and the function type value of the input cell header.

  When the AIS cell detection unit 22B detects that the input cell is a VP-AIS cell, the AIS cell detection unit 22B outputs “1”. When the AIS cell detection unit 22B detects that the cell is a cell other than the VP-AIS cell, "0" is output.

  The window unit 22C according to the present embodiment is a FIFO memory having the same number of bits as the number of cells stored in the FIFO unit 22A (4 bits as an example in the present embodiment), and is output from the AIS cell detection unit 22B. “0” or “1” is input. Therefore, for example, when all four cells stored in the FIFO unit 22A are VP-AIS cells, the content of the window unit 22C is “1111”.

  The determination unit 22D according to the present embodiment determines whether or not a LOS has occurred by determining whether or not a predetermined number or more of VP-AIS cells have been input from the ATM end card 14 within a predetermined period.

  Specifically, the determination unit 22D according to the present embodiment determines whether there are two or more VP-AIS cells in the latest four cells by determining whether or not there are two or more “1” s in the window unit 22C. By determining whether or not there are two or more, it is determined whether or not LOS has occurred. If the determination unit 22D determines that the LOS has occurred, the determination unit 22D notifies the first generation unit 24 and the selector 26 that the LOS detection is valid. On the other hand, if the determination unit 22D determines that the LOS is not in effect, the determination unit 22D notifies the first generation unit 24 and the selector 26 that LOS detection is invalid.

  As described above, the VP-AIS cell does not include information for identifying the transmission source. The ATM terminal card 14 outputs a cell (including a VP-AIS cell) input from the user equipment 16 at 25.6 Mbps when normal, and generates a VP-AIS cell at 155.52 Mbps at LOS. And output.

  Therefore, as in the present embodiment, the determination unit 22D determines whether there are two or more VP-AIS cells in the latest four cells. Thereby, it is determined whether the VP-AIS cell is input from the user equipment 16 via the ATM termination card 14 or is generated by the ATM termination card 14 due to the LOS. it can.

  Note that the number of cells to be determined by the determination unit 22D, that is, the sizes of the FIFO unit 22A and the window unit 22C, and the threshold used for determination by the determination unit 22D are not limited to the above values. These values may be set as appropriate according to the ratio between the first communication speed and the second communication speed, and it is sufficient that at least the number of cells to be determined by the determination unit 22D is plural.

  More specifically, the determination unit 22D according to the present embodiment has an internal circuit, and the state is any of a normal state, a failure state, and a recovery protection state shown in FIG. . In the following description, it is assumed that the initial state of the determination unit 22D is a normal state.

  As illustrated in FIG. 6, in the normal state, the determination unit 22D continues in the normal state when “1” is one or less in the window portion 22C. In the normal state, the determination unit 22D transitions to the failure state when there are two or more “1” s in the window unit 22C. When the determination unit 22D has two or more “1” s in the window unit 22C in the failure state, the failure state continues. In the failure state, the determination unit 22D transitions to the recovery protection state when “1” is one or less in the window portion 22C.

  The determination unit 22D transitions to a failure state when there are two or more “1” s in the window unit 22C in the recovery protection state. In the recovery protection state, the determination unit 22D continues the recovery protection state when “1” is one or less in the window portion 22C. When the 1.5-second timer expires in the recovery protection state, the determination unit 22D transitions to a normal state.

  Next, this timer will be described. The timer unit 22E according to the present embodiment has a timer whose initial value is 0, and enters a valid state when the determination unit 22D notifies the validity of the timer. The timer unit 22E counts up the timer while it is in a valid state. When the timer value reaches a preset value (1.5 seconds in the present embodiment), the timer unit 22E Notify expiration and reset the timer to zero. On the other hand, the timer unit 22E enters an invalid state when the determination unit 22D notifies the timer invalid. The timer unit 22E sets the timer to 0 while it is in an invalid state, and does not increment the timer.

  The notification from the determination unit 22D to the timer unit 22E, the first generation unit 24, and the selector 26 is as shown in Table 1 below.

  As shown in Table 1, in the normal state, the determination unit 22D notifies the timer unit 22E that the timer is invalid, and notifies the first generation unit 24 and the selector 26 that the LOS detection is invalid. On the other hand, in the failure state, the determination unit 22D notifies the timer unit 22E that the timer is invalid, and notifies the first generation unit 24 and the selector 26 that the LOS detection is valid. Further, in the recovery protection state, the determination unit 22D notifies the timer unit 22E that the timer is valid, and notifies the first generation unit 24 and the selector 26 that the LOS detection is valid. These notifications are made every time the determination unit 22D processes each cell including an empty cell.

  The state transition of the determination unit 22D having the above configuration will be described in detail. When normal, the determination unit 22D is always in a normal state.

  On the other hand, at the time of LOS, as described above, the determination unit 22D first performs the above-described determination process on the VP-AIS cell addressed to the VPC having a VPI of 0 to 255 that is input from the ATM terminal card 14 at one set per second. To do so, transition to the fault state. Next, since the determination unit 22D performs the determination process on the empty cell for the remaining one second, the determination unit 22D transits to the recovery protection state and notifies the timer unit 22E that the timer is valid. Thereby, the timer unit 22E starts counting up the timer.

  When the LOS continues, since the VP-AIS cell addressed to the VPC having the VPI of 0 to 255 is input again after about 1 second (at least 1 second and less than 1.5 seconds), the determination unit 22D enters the failure state. Transition is made and the timer unit 22E is notified of the invalidity of the timer. On the other hand, when the LOS recovers, a plurality of VP-AIS cells are not input in the latest four cells, so that the recovery protection state continues, and after expiration of 1.5 seconds, the timer unit 22E notifies the expiration of the timer, The determination unit 22D transitions to a normal state.

  When the determination unit 22D determines that the LOS has occurred, the first generation unit 24 generates a failure notification cell including a value corresponding to the port number that identifies the connection location of the user device 16 that has become the LOS. The value corresponding to the port number is an example of the specific information of the present invention, and the failure notification cell is an example of the failure notification information of the present invention.

  The failure notification cell will be described with reference to FIG. As shown in FIG. 7, the failure notification cell includes a 4-bit CLID (Cell Identification) field, a 2-bit PORT field, and a 1-bit LA (Line Alarm) field.

  The CLID indicates a cell type. In the present embodiment, “1000” is stored in the CLID field as a value indicating that the cell is a failure notification cell. PORT indicates a connection location that has become LOS, and a value corresponding to the ATM port 20 that has become LOS is stored. In the present embodiment, in the PORT field, “00” is set as a value according to the ATM port 20A, “01” is set as a value according to the ATM port 20B, and “10” is set as a value according to the ATM port 20C. “11” is stored as a value corresponding to the ATM port 20D.

  LA indicates a flag indicating whether or not a transmission line failure has occurred, that is, whether or not a LOS has occurred (hereinafter referred to as “transmission line failure flag”). In the present embodiment, the LA field includes “1” is stored during LOS, and “0” is stored during normal operation.

  Note that the cell format of the failure notification cell and the values stored in each field are examples, and the present invention is not limited to this. The cell format of the failure notification cell and the value stored in each field are those that can identify whether the cell is a failure notification cell, the connection location that has become LOS, and whether or not a transmission line failure has occurred. Good.

  Specifically, the 1st production | generation part 24 has an internal circuit, and the state will be in any state of a valid state and an invalid state. In other words, the first generation unit 24 becomes valid when notified of the validity of LOS detection from the determination unit 22D, and becomes invalid when notified of invalidity of LOS detection from the determination unit 22D.

  In the valid state, the first generation unit 24 provides the CLID field value (hereinafter referred to as “CLID value”) as “1000” and the PORT field value (hereinafter referred to as “PORT value”). A failure notification cell having a value corresponding to the ATM port 20 and an LA field value (hereinafter referred to as “LA value”) “1” is generated at 155.52 Mbps and output. The first generation unit 24 sets the CLID value to “1000”, the PORT value to a value corresponding to the ATM port 20 in which the first generation unit 24 changes from the valid state to the invalid state, and the LA value to “0”. Only one failure notification cell is generated and output. Further, the first generation unit 24 does not generate a failure notification cell while the invalid state continues.

  As shown in FIGS. 2 and 3, the selector 26 according to the present embodiment receives the cell output from the FIFO unit 22A. Further, the selector 26 receives the failure notification cell output from the first generation unit 24 when LOS occurs. Further, the selector 26 is notified of whether the LOS detection is valid or invalid from the determination unit 22D. The selector 26 also has an internal circuit similar to the first generation unit 24, and its state is either a valid state or an invalid state. In other words, the selector 26 enters the valid state when notified by the determination unit 22D that the LOS detection is valid, and enters the invalid state when notified from the determination unit 22D that the LOS detection is invalid.

  In the valid state, the selector 26 outputs a failure notification cell in which the transmission path failure flag (LA value) input from the first generation unit 24 is “1”. The selector 26 outputs a failure notification cell in which the transmission line failure flag input from the first generation unit 24 is “0” at the timing when the selector 26 changes from the valid state to the invalid state. Further, the selector 26 outputs the cell input from the FIFO unit 22A while the invalid state continues.

  The operation of the ATM port 20 will be described with reference to FIG. 8A and 8B show the contents of the window part 22C, and the lower parts of FIGS. 8A and 8B show cells input to the filter part 22 and cells output from the selector 26. A cell “VPI = 0” in FIG. 8A indicates a VP-AIS cell input from the user equipment 16 via the ATM termination card 14. Also, the dotted rectangles in FIGS. 8A and 8B indicate empty cells.

  As shown in FIG. 8A, during normal operation, the VP-AIS cell input from the user equipment 16 to the ATM termination card 14 is output from the ATM termination card 14 at 25.6 Mbps and input to the filter unit 22. As described above, in this embodiment, since the communication speed between the ATM end card 14 and the ATM port 20 is 155.52 Mbps, an empty cell is inserted between each VP-AIS cell in the normal state. The

  As shown in FIG. 8A, when normal, a plurality of “1” s are not stored in the window unit 22C, and the determination unit 22D keeps the normal state and notifies the invalidity of LOS detection. Therefore, the selector 26 outputs the VP-AIS cell and the empty cell input from the filter unit 22.

  On the other hand, as shown in FIG. 8B, at the time of LOS, one set of VP-AIS cells destined for a VPC having a VPI of 0 to 255 is input to the filter unit 22 from the ATM terminal card 14 at 155.52 Mbps.

  As shown in FIG. 8B, at the time of LOS, a plurality of “1” s are stored in the window unit 22C, and the determination unit 22D enters a failure state and notifies the validity of LOS detection. Therefore, the selector 26 outputs the failure notification cell in which the transmission line failure flag generated by the first generation unit 24 is “1”.

  When the LOS is recovered, the determination unit 22D first transits to the recovery protection state, and transits to the normal state after 1.5 seconds. At this time, the notification of LOS detection from the determination unit 22D changes from valid to invalid. Therefore, the selector 26 outputs one failure notification cell in which the transmission line failure flag generated by the first generation unit 24 is “0”.

  As described above, since the ATM termination card 14 sequentially generates and outputs 256 VP-AIS cells at 155.52 Mbps at the time of LOS, an empty cell is inserted between each VP-AIS cell. Unlikely. However, as shown in FIG. 8B, even when an empty cell is inserted between any of the VP-AIS cells and is input to the filter unit 22, the determination unit 22D determines that the LOS has occurred.

  As shown in FIG. 2, the cell output from the selector 26 of each ATM port 20 is input to the multiplexing unit 28.

  As shown in FIG. 9, the multiplexing unit 28 multiplexes the cells input from the selectors 26 of the ATM ports 20 by time division multiplexing and outputs the result. As shown in FIG. 9, the cells output from each ATM port 20 by multiplexing by the multiplexing unit 28 are output from the multiplexing unit 28 every four cells.

  As shown in FIG. 2, the cell output from the multiplexing unit 28 is input to the failure notification cell detection unit 30 and the output unit 36.

  The failure notification cell detection unit 30 according to the present embodiment detects a failure notification cell by determining whether or not the CLID value of the input cell is “1000”. When a failure notification cell is detected, the failure notification cell detection unit 30 further refers to the LA value. When the LA value is “1”, the failure notification cell detection unit 30 notifies the validity of the transmission line failure and also notifies the PORT value. . Further, when the failure notification cell is detected and the LA value is “0”, the failure notification cell detection unit 30 notifies the invalidity of the transmission line failure and the PORT value. Furthermore, when no failure notification cell is detected, the failure notification cell detection unit 30 notifies the failure of the transmission path failure. These notifications are input to the second generation unit 32 and the output unit 36.

  When a failure notification cell is generated by the first generation unit 24, the second generation unit 32 according to the present embodiment determines that the connection location corresponding to the PORT value is LOS based on the PORT value included in the failure notification cell. Therefore, a VP-AIS cell and a VC-AIS cell (in this embodiment, an end-to-end F5 flow OAM cell) are generated for a destination that affects communication.

  Specifically, the second generation unit 32 also has an internal circuit like the first generation unit 24, and the state thereof is either a valid state or an invalid state. In other words, the second generation unit 32 is enabled when the failure notification cell detection unit 30 is notified of the validity of the transmission line failure, and is invalidated when the failure notification cell detection unit 30 is notified of the transmission line failure. It becomes a state.

  Then, in the valid state, the second generation unit 32 refers to the connection table 34 and acquires the VPI value and the VCI value of the destination that affects communication based on the PORT value notified from the failure notification cell detection unit 30. To do.

  The connection table 34 will be described with reference to FIG. The connection table 34 according to the present embodiment is a table in which a destination VPI value and a VCI value that are affected when each ATM terminal card 14 corresponding to each ATM port 20 becomes LOS are registered in advance. Note that the port number string in FIG. 10 indicates the PORT value corresponding to each ATM port 20. Further, the VPI column and the VCI column in FIG. 10 respectively indicate the VPI value and the VCI value of the destination having an influence on the communication when each ATM terminal card 14 corresponding to the value of the port number column becomes LOS.

  Note that the configuration of the connection table 34 shown in FIG. 10 is an example, and is not limited to this. Any configuration can be used as long as the destination that affects communication can be specified by the connection location that becomes the LOS.

  Then, in the valid state, the second generation unit 32 generates and outputs a VP-AIS cell for the VPC having the acquired VPI value and a VC-AIS cell for the VCC (Virtual Channel Connection) having the acquired VCI value. In the present embodiment, the second generation unit 32 generates and outputs one VP-AIS cell and one VC-AIS cell each second in the valid state. The cell output by the second generation unit 32 is input to the output unit 36. Moreover, the 2nd production | generation part 32 does not produce | generate a VP-AIS cell and a VC-AIS cell in an invalid state.

  The output unit 36 according to the present embodiment selects a cell to be output in response to a notification of transmission path failure validity or invalidity. Specifically, the output unit 36 has an internal circuit for each PORT value, and the state becomes either a valid state or an invalid state for each PORT value. That is, when the failure notification cell detection unit 30 notifies the failure of the transmission line and the PORT value, the output unit 36 becomes valid, and the failure notification cell detection unit 30 disables the transmission line failure. When the PORT value is notified, the PORT value becomes invalid.

  In the valid state, the output unit 36 discards the cell corresponding to the PORT value in the valid state in the cell input from the multiplexing unit 28. Further, in the valid state, the output unit 36 multiplexes the VP-AIS cell and the VC-AIS cell input from the second generation unit 32 instead of the discarded cell, and outputs the multiplexed VP-AIS cell and the VC-AIS cell to the ATM network 18. The output unit 36 outputs the cell input from the multiplexing unit 28 to the ATM network 18 in the invalid state.

  As described above, the second generation unit 32 outputs the VP-AIS cell and the VC-AIS cell one cell per second in the valid state. Therefore, the output unit 36 may output the cell input from the multiplexing unit 28 at a timing when the VP-AIS cell and the VC-AIS cell are not output by the second generation unit 32 in the valid state. The cells may be discarded and empty cells may be multiplexed instead.

  By the way, the processing by each component of the line termination device 12 configured as described above may be realized by a software configuration using a computer by executing a program. However, it is not limited to realization by software configuration, and it goes without saying that it may be realized by hardware configuration or a combination of hardware configuration and software configuration. In addition, as a form example in the case where each of the above constituent elements is realized by a hardware configuration, a form in which a functional element that performs the same processing as that of each constituent element is created and applied is exemplified.

  Next, with reference to FIG. 11, the operation of the line termination device 12 according to the present embodiment will be described. FIG. 11 is a flowchart showing the flow of cell output processing from when a cell output by the ATM terminal card 14 is input to the filter unit 22 until a cell is output to the ATM network 18 by the output unit 36. .

  In step S100 of FIG. 11, the AIS cell detection unit 22B determines whether the input cell is a VP-AIS cell as described above. When this determination is affirmative, the AIS cell detection unit 22B proceeds to the process of step S102, and when it is negative, the AIS cell detection unit 22B proceeds to the process of step S104.

  In step S102, the AIS cell detection unit 22B outputs “1” to the window unit 22C. On the other hand, in step S104, the AIS cell detection unit 22B outputs “0” to the window unit 22C.

  In step S106, the determination unit 22D determines whether or not LOS has occurred by determining whether or not there are two or more “1” s in the window unit 22C. Based on this determination and the presence or absence of timer expiration notification from the timer unit 22E, the state of the determination unit 22D transitions to a normal state, a recovery protection state, or a failure state as shown in FIG. Then, as shown in Table 1, the determination unit 22D notifies the timer unit 22E of the validity or invalidity of the timer according to the state, and informs the first generation unit 24 and the selector 26 whether the LOS detection is valid or invalid. Notice.

  In the next step S108, the first generation unit 24 enters the valid state or the invalid state according to the notification of the validity or invalidity of the LOS detection from the determination unit 22D. As described above, in the valid state, the first generation unit 24 generates and outputs a failure notification cell with the transmission line failure flag set to “1”. Further, the first generation unit 24 generates and outputs only one failure notification cell with the transmission line failure flag set to “0” at the timing when the state changes from the valid state to the invalid state. Further, the first generation unit 24 does not generate a failure notification cell while the invalid state continues.

  In the next step S110, the selector 26 enters the valid state or the invalid state according to the notification of the validity or invalidity of the LOS detection from the determination unit 22D. As described above, in the valid state, the selector 26 outputs a failure notification cell in which the transmission path failure flag input from the first generation unit 24 is “1”. The selector 26 outputs a failure notification cell in which the transmission line failure flag input from the first generation unit 24 is “0” at the timing when the selector 26 changes from the valid state to the invalid state. Further, the selector 26 outputs the cell input from the FIFO unit 22A while the invalid state continues. The processes in steps S100 to S110 are executed in parallel for each ATM port 20.

  In the next step S112, the multiplexing unit 28 multiplexes the cells input from the selector 26 of each ATM port 20 by time division multiplexing and outputs the multiplexed cells.

  In the next step S114, the failure notification cell detection unit 30 determines whether or not the cell input from the multiplexing unit 28 is a failure notification cell, as described above. If this determination is affirmative, the failure notification cell detection unit 30 proceeds to the process of step S116. In step S116, the failure notification cell detection unit 30 determines whether or not the LA value of the failure notification cell is “1”. The failure notification cell detection unit 30 proceeds to the process of step S118 when this determination is affirmative, while it proceeds to the process of step S120 when this determination is negative.

  In step S118, the failure notification cell detection unit 30 notifies the validity of the transmission line failure and the PORT value. On the other hand, in step S120, the failure notification cell detection unit 30 notifies the invalidity of the transmission line failure and the PORT value. On the other hand, when the determination of step S114 is negative, the failure notification cell detection unit 30 proceeds to the process of step S122. In step S122, the failure notification cell detection unit 30 notifies the failure of the transmission path failure.

  In step S <b> 124, the second generation unit 32 enters the valid state or the invalid state according to the notification of the valid or invalid transmission path failure from the failure notification cell detection unit 30. As described above, the second generation unit 32 acquires the VPI value and the VCI value corresponding to the PORT value from the connection table 34 in the valid state. Then, the second generation unit 32 generates and outputs one VP-AIS cell for the VPC having the acquired VPI value and one VC-AIS cell for the VCC having the acquired VCI value each second. Moreover, the 2nd production | generation part 32 does not produce | generate a VP-AIS cell and a VC-AIS cell in an invalid state.

  In the next step S126, the output unit 36 enters the valid state or invalid state for each PORT value in response to the notification of the validity or invalidity of the transmission line failure from the failure notification cell detection unit 30 and the notification of the PORT value. . As described above, in the valid state, the output unit 36, in the cell output from the multiplexing unit 28, the VP− input from the second generation unit 32 instead of the cell corresponding to the PORT value in the valid state. AIS cells and VC-AIS cells are multiplexed and output. Further, in the invalid state, the output unit 36 outputs a cell corresponding to the PORT value in the invalid state among the cells output from the multiplexing unit 28. With the processing in step S126, the cell is output from the output unit 36 to the ATM network 18, and the cell output processing is terminated.

  As described above, in the present embodiment, the determination unit 22D determines whether or not two or more VP-AIS cells have been input from the ATM end card 14 in the latest four cells. It is determined whether or not. Thereby, it is possible to accurately detect that the input signal from the user device 16 is in the disconnected state.

  In the present embodiment, when the first generation unit 24 determines that the LOS has occurred by the determination unit 22D, the first generation unit 24 generates a failure notification cell including a PORT value that identifies the connection location of the user device 16 that has become the LOS. doing. Thereby, the connection location of the user equipment 16 in which the input signal is in the disconnected state can be specified.

  Furthermore, in the present embodiment, when the second generation unit 32 generates a failure notification cell by the first generation unit 24, the connection location becomes LOS based on the PORT value included in the failure notification cell. To generate a VP-AIS cell and a VC-AIS cell for a destination that affects communication. In the present embodiment, the output unit 36 outputs the VP-AIS cell and the VC-AIS cell generated by the second generation unit 32. Thereby, it can be efficiently notified that the input signal from the user device 16 is in a disconnected state. Further, even when the ATM terminal card 14 does not have a function of generating a VC-AIS cell at the time of LOS, it is possible to notify the VCC that the input signal from the user equipment 16 has been cut off. .

  Although the embodiment has been described above, the technical scope of the present invention is not limited to the scope described in the embodiment. Various modifications or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such modifications or improvements are added are also included in the technical scope of the present invention.

  Further, the above embodiments do not limit the invention according to the claims (claims), and all the combinations of features described in the embodiments are essential for the solution means of the invention. Not exclusively. The embodiments described above include inventions at various stages, and various inventions are extracted by combining a plurality of disclosed constituent elements. Even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, as long as an effect is obtained, a configuration from which these some constituent requirements are deleted can be extracted as an invention.

  For example, in the above embodiment, the case where the VP-AIS cell is detected by the AIS cell detection unit 22B has been described, but the present invention is not limited to this.

  As described above, the ATM termination card 14 outputs the cell input from the user equipment at the first communication speed (25.6 Mbps) at a normal time, and between the ATM termination card 14 and the line termination device 12. The empty cell is output so that the communication speed becomes the second communication speed (155.52 Mbps). Therefore, by counting the number of empty cells in the latest four cells, cells input from the user equipment 16 to the ATM port 20 via the ATM termination card 14 and generated by the ATM termination card 14 are used. It is possible to determine whether or not the communication speed of the VP-AIS cell input to is higher than a predetermined speed higher than the first communication speed. For example, if the number of empty cells is two or less among the latest four cells, it can be determined that the communication speed is higher than the first communication speed.

  Therefore, for example, the AIS cell detection unit 22B detects whether or not the input cell is an empty cell, and when the cell is an empty cell, outputs “1” to the window unit 22C, and the cell is empty. If it is not a cell, “0” is output to the window portion 22C. Then, the determination unit 22D may determine whether or not the LOS has occurred by determining whether or not the number of “1” s in the window unit 22C is equal to or less than a predetermined number (two as an example). . Thereby, the filter unit 22 can determine whether or not the LOS has occurred without detecting whether or not the cell input from the ATM end card 14 is a VP-AIS cell.

  In the above embodiment, the case where the ATM end card 14 generates and outputs one set of VP-AIS cells addressed to VPCs with VPI of 0 to 255 at the time of LOS has been described. It is not limited. For example, the ATM end card 14 may generate and output a plurality of sets of the VP-AIS cells per second during LOS.

  In the above-described embodiment, the case where the second generation unit 32 generates and outputs one VP-AIS cell and one VC-AIS cell each second in the valid state has been described. However, the present invention is not limited to this. Is not to be done. For example, the second generation unit 32 may generate and output a plurality of VP-AIS cells and VC-AIS cells each second in the valid state.

  In the above embodiment, the case where the VP-AIS cell and the VC-AIS cell are finally output from the output unit 36 at the time of LOS has been described. However, the present invention is not limited to this. For example, the line termination device 12 may be provided with a display unit such as an LED lamp or a liquid crystal display, and information indicating that LOS is detected may be output to the display unit. Further, in this case, information indicating the port number where the LOS has occurred may be output to the display unit.

  In the above embodiment, the case where both the VP-AIS cell and the VC-AIS cell are applied as the cells output by the output unit 36 at the time of LOS has been described. However, the present invention is not limited to this. Absent. As a cell output from the output unit 36, a VP-AIS cell or a VC-AIS cell may be applied.

  In the above embodiment, the case where the determination unit 22D determines whether or not the LOS has occurred by referring to the window unit 22C has been described, but the present invention is not limited to this. For example, the determination unit 22D performs a process for detecting a VP-AIS cell similar to the AIS cell detection unit 22B in each cell of the FIFO unit 22A. And the determination part 22D is good also as a form which determines whether it became LOS by whether the number of VP-AIS cells is more than predetermined number (for example, two). In this case, each time a cell is input, the determination unit 22D performs a process of detecting whether or not each cell of the FIFO unit 22A is a VP-AIS cell. The cell detection unit 22B and the window unit 22C need not be provided.

  In the above embodiment, the case where the ATM network 18 is applied as the backbone network to which the line terminating device 12 is connected has been described. However, the present invention is not limited to this. For example, a network of another communication method such as Ethernet (registered trademark) may be applied as the backbone network. In this case, the line termination device 12 may be provided with a conversion unit that converts between ATM and the communication method of the network.

  Moreover, although the case where ATM was applied as a communication system between the ATM terminal card 14 and the user equipment 16 was described in the above embodiment, the present invention is not limited to this. For example, when the input signal from the user device is in a normal state as the communication method, the cell input from the user device is output at the first communication speed, and the input signal from the user device is in a disconnected state Another communication method that allows communication by a connection device that generates and outputs failure management information at a second communication speed that is faster than the first communication speed may be applied.

  In addition, the configuration of the line termination device (see FIGS. 1 to 3) described in the above embodiment is merely an example, and unnecessary portions can be deleted or new portions can be deleted without departing from the gist of the present invention. Needless to say, it may be added.

  The cell output process flow (see FIG. 11) described in the above embodiment is also an example, and unnecessary steps are deleted or new steps are added without departing from the gist of the present invention. Needless to say, the processing order may be changed.

DESCRIPTION OF SYMBOLS 10 Communication system 12 Line termination apparatus 14 ATM termination card 16 User equipment 22D Determination part 24 1st production | generation part 32 2nd production | generation part 36 Output part

Claims (6)

When the user equipment is connected and the input signal from the user equipment is in a normal state, information input from the user equipment is output at the first communication speed, and when the input signal is in a disconnected state, failure management is performed. The communication speed of information input from a connection device that generates and outputs information at a second communication speed that is faster than the first communication speed is greater than or equal to a predetermined speed that is higher than the first communication speed. A determination unit for determining whether or not the input signal is in a disconnected state by determining whether or not there is;
An output unit that outputs information indicating that the input signal is in a disconnected state when the determination unit determines that the input signal is in a disconnected state;
Line termination equipment with The information input from the user equipment includes failure management information,
The determination unit determines whether or not the input signal is in a disconnected state by determining whether or not a predetermined number or more of failure management information is input from the connection device within the predetermined period. The line terminator described. A first generation unit that generates failure notification information including specific information that identifies a connection location of the user device in which the input signal is in a disconnected state when the determination unit determines that the input signal is in a disconnected state. Further comprising
The line termination apparatus according to claim 1, wherein the output unit further outputs information indicating the connection location based on the failure notification information generated by the first generation unit. When the failure notification information is generated by the first generation unit, the communication is affected by the input signal to the connection location being disconnected based on the specific information included in the failure notification information. A second generator for generating failure management information for a certain destination;
The line termination apparatus according to claim 3, wherein the output unit outputs failure management information generated by the second generation unit as information indicating that the input signal is in a disconnected state. The communication method between the user equipment and the connection device is an asynchronous transfer mode,
The line termination device according to any one of claims 1 to 3, wherein the failure management information is a VP-AIS cell. The communication method between the user equipment and the connection device is an asynchronous transfer mode,
The failure management information output by the connection device is a VP-AIS cell,
The line termination apparatus according to claim 4, wherein the failure management information generated by the second generation unit is a VP-AIS cell and a VC-AIS cell.