JP2009188501A - Switch device and cell missing detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect cell missing of each switch path with one series of sequence numbers assigned in common to switch paths by a switch which comprises a plurality of input units, a plurality of output units, and a switch unit connecting the respective input units and respective output units and includes a plurality of switch paths from one input unit to one output unit. <P>SOLUTION: A cell missing detection unit 7-1 provided for output units 1-5-1 to 1-5-N recognizes the order of a sequence number imparted to a cell passing through the same switch path from the order of switch paths for sending cells out by the input units 1-1-1 to 1-1-L and sequence numbers imparted to the cells by the output units as destinations of the cells at the respective input units, and checks successiveness of sequence numbers by the switch paths to monitor cell missing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switch device used as a core router of a network, and in particular, includes a plurality of input units, a plurality of output units, each input unit, and a switch unit that connects each output unit, and one output unit outputs one output. The present invention relates to a cell drop detection method in a switch device in which a plurality of switch paths to a unit exist.

  In a switch that is composed of a plurality of input units, a plurality of output units, and a switch unit that connects each input unit and each output unit, and there are a plurality of switch paths from one input unit to one output unit. When the cell sent from the input unit to the switch unit reaches the output unit via the switch unit, the order of the cells may be changed because the cell passes through a plurality of paths. This can occur when a cell passes through switch paths with different delays when reaching the output from the input.

  When the output unit detects a change in the order of the cells, a process of returning the order of the cells to the order of cell output from the input unit is performed. Specifically, in order to recognize the cell order, the cell order is restored based on the sequence numbers assigned in order for each cell when the cells are sent from the input unit to the switch unit. Such a process is called a reordering process.

  Although not a switching device, a communication method that transmits a series of data on a plurality of paths between a transmission terminal and a reception terminal also performs processing similar to the reordering processing using a sequence number.

  For example, in Patent Document 1, the same processing as the reordering processing is performed when data of one communication flow used for communication between a transmission terminal and a reception terminal is branched into a plurality of flows and the original flow is restored. Yes. Specifically, for example, a gateway is installed in each of a first LAN (Local Area Network) to which the transmitting terminal belongs and a second LAN to which the receiving terminal belongs, and a TCP (Transmission Control Protocol) connection transmitted from the transmitting terminal is established. Data is distributed to each communication path in packet units in the first LAN gateway, and the order inversion of packets received from a plurality of communication paths is corrected according to the TCP sequence number in the second LAN gateway.

  In addition, for example, in Patent Document 2, in order to efficiently use a plurality of communication lines and improve the line utilization rate, a function that is added to the TCP of the terminal and communication that has conventionally used one TCP connection is performed. In communication changed to use a plurality of TCP connections, processing similar to the reordering processing is performed. Specifically, first, communication performed in one communication flow in communication between the transmission terminal and the reception terminal is divided into a plurality of communication flows and sent in parallel. Next, when data is transmitted from the transmission terminal to the reception terminal, the communication protocol of the transmission terminal divides the data of one communication flow and distributes the data to a plurality of communication flows. A new header is added to the TCP / IP packet as restoration information for restoring the communication flow (that is, using two system sequence numbers), and data is transmitted in a plurality of communication flows. The communication protocol of the receiving terminal refers to the restoration information of data received from a plurality of communication flows, performs the same processing as the Reordering processing, and restores the original one communication flow. A technique for detecting a packet loss for each path through which a packet passes using two system sequence numbers is also described in Patent Document 3.

JP 2000-261478 A JP 2003-110604 A JP 2004-7361 A

  In a switch that includes a plurality of input units, a plurality of output units, and a switch unit that connects each input unit and each output unit, and there are a plurality of switch paths from one input unit to one output unit. If a cell drop occurs in any switch path from the input unit to the output unit, the reordering process waits for a cell that should come (fallen cell), and the process does not operate normally. For this reason, it is necessary to monitor the presence or absence of a cell drop and reflect the information of the dropped cell in the reordering process. In consideration of the possibility that the cell order may be changed between the switch paths due to different delays between the switch paths, it is necessary to monitor the cell drop for each switch path.

  Here, as a method for monitoring cell drop for each switch path, a method using two system sequence numbers as in the second prior art can be considered. In other words, this is a method of using a sequence number for each switch path separately from the sequence number assigned for the reordering process. However, if two system sequence numbers are assigned to each cell, there is a problem that the amount of information of the cell header information increases and the transfer rate increases. For this reason, a technique that can monitor cell drop for each switch path without increasing the transfer rate is desired.

  The present invention includes a plurality of input units, a plurality of output units, and a switch unit that connects each input unit and each output unit, and there are a plurality of switch paths from one input unit to one output unit. In such a switch, it is an object to enable detection of a cell drop for each switch path by using a sequence number assigned to one switch path.

  The switch device of the present invention includes a plurality of input units, a plurality of output units, and a switch unit that connects each input unit and each output unit, and a plurality of switch paths from one input unit to one output unit. In an existing switch device, the same switch path is determined based on the sequence of switch paths for sending cells in each input unit and the sequence number assigned to each cell for each output unit serving as a cell destination in each input unit. Cell drop detection means for recognizing cell drop by recognizing the order of sequence numbers assigned to cells passing through and checking the continuity of the sequence numbers for each switch path.

  The cell drop detection method of the present invention includes a plurality of input units, a plurality of output units, and a switch unit that connects each input unit and each output unit, and switches from one input unit to one output unit. In the cell drop detection method in a switch device having a plurality of paths, the cell drop detection means provided in the output unit outputs a cell path in each input unit and an output serving as a cell destination in each input unit By recognizing the order of sequence numbers assigned to cells passing through the same switch path from the sequence numbers assigned to the cells for each copy, and checking the continuity of the sequence numbers for each switch path, Monitor.

  According to the present invention, it is possible to detect a cell drop for each switch path by using one system sequence number assigned in common to the switch path.

“First Embodiment”
Referring to FIG. 1, an example of a switch device to which the present invention is applied is a load balance type switch including L input units, k intermediate stage buffers, and N output units. L, N, and k are positive integers of 2 or more, and may be the same value or different values. In this example, the input section and the intermediate stage buffer, and the intermediate stage buffer and the output section are connected by a crossbar (XBAR) switch, but the front crossbar switch 1-2 and the rear crossbar switch 1- A mode in which 4 is physically replaced with a mesh connection using an optical cable or the like is also conceivable.

  The input units 1-1-1 to 1-1-L are respectively connected to the input ports of the front-stage crossbar switch 1-2, and the output ports of the front-stage crossbar switch 1-2 are connected to the intermediate-stage buffer 1-3-1. Connected to ~ 1-3-k. In other words, cells output from the input units 1-1-1 to 1-1-L reach the intermediate stage buffers 1-3-1 to 1-3k via the previous stage crossbar switch 1-2. Become. The cell to be switched is provided with a cell header. At the input unit, an output unit number of the cell transmission destination, an input unit number of the cell transmission source, and a sequence number individually assigned to each destination output unit are added. .

  The intermediate stage buffers 1-3-1 to 1-3-k receive the cells received from the input units 1-1-1 to 1-1-L via the previous-stage crossbar buffer 1-2 in units of destination output units. Built-in VOQ (Virtual Output Queue) to store. The output of the intermediate stage buffer 1-3-1 to 1-3-k is connected to the input port of the rear-stage crossbar switch 1-4, and the output port of the rear-stage crossbar switch 1-4 is connected to the output section 1-5-1 to Connected to 1-5-N. That is, the cells output from the intermediate stage buffers 1-3-1 to 1-3k reach the output units 1-5-1 to 1-5-N via the post-stage crossbar switch 1-4. .

  The output units 1-5-1 to 1-5-N receive cells from the post-stage crossbar switch 1-4, check the cell order for each of the input units 1-1-1 to 1-1-L, and Reordering processing unit 7-5 that performs processing to arrange in the correct cell order when there is a reversal of order, and recognizes in advance the order of the switch path that each input unit sends out the cell, and output that becomes the destination of the cell at each input unit Cell loss detection unit 7 that recognizes the switch path through which the cell has passed from the sequence number assigned to the cell for each unit and performs cell loss monitoring by checking the continuity of the sequence number for each switch path through which the cell has passed -1.

  In the load balance type switch shown in FIG. 1, when a cell is sent from a certain input unit to a certain output unit, it passes through any one of the intermediate stage buffers 1-3-1 to 1-3k. Therefore, as shown in FIG. 2, for example, when a cell is output from the input unit 1 to the output unit 1, there are k switch paths. In this case, the cell order is not changed in the same switch path. However, when a cell is transmitted using a different switch path, the cell order may arrive in reverse in the output unit. The reason is that because the switch path has a buffer (intermediate stage buffer), the arrival time from the input unit to the output unit may differ depending on the switch path due to the difference in the cell accumulation state of the intermediate stage buffer. It is. Further, cell dropping may occur due to buffer overflow or the like.

  In the case of the present embodiment, the cell drop detection unit 7-1 provided in each output unit includes a cell path order in each input unit and a cell for each output unit serving as a cell destination in each input unit. By recognizing the order of sequence numbers assigned to cells passing through the same switch path from the sequence numbers assigned to the cells, and checking the continuity of the sequence numbers for each switch path passed by the cells, Monitor. The reordering processing unit 7-5 performs the reordering process in consideration of the cell drop detection result by the cell drop detection unit 7-1.

  In this embodiment, for example, the order determined by the FOFF (Full Ordered Frames First) method is used as the order of switch paths for transmitting cells in each input unit. The FOFF method is a kind of algorithm in which cells are distributed and output by an input unit in a load balance type switch. In each input unit, a cell is sequentially transmitted to each intermediate buffer for each destination output unit. As a simple example, in a load-balanced switch having four switch paths, the order in which a certain input unit A sends cells to a certain output unit B by the FOFF method is shown in FIG. For the purpose of explanation, intermediate buffer existing in the middle of the switch path is not shown). As described above, in the FOFF method, cells with sequence numbers 0, 1, 2, 3, 4,... Are sequentially transmitted to a plurality of switch paths. References on load balance type switches and FOFF systems include “Isaac Keslassy,“ The Load-Balanced Router, ”Ph.D. Dissertation, Stanford University, June 2004”.

  As described above, when each input unit sends a cell by the FOFF method, in the cell drop detection unit 7-1, the number of switch paths and the sequence number assigned to the cell for each output unit serving as the cell destination From the above, the sequence number sequence of a series of cells passing through the same switch path can be recognized. For example, in the case of FIG. 5, when a cell with sequence number 0 is received from switch path 0, it is understood that cells with sequence number 4, sequence number 8,. Similarly, if a cell with sequence number 1 is received from switch path 1, a cell with sequence number 1 + 4M is received from switch path 1 and a cell with sequence number 2 is received from switch path 2. If there is a cell with sequence number 2 + 4M from switch path 2 and a cell with sequence number 3 from switch path 3, then switch path 3 will subsequently receive a cell with sequence number 3 + 4M. It can be seen that the cell is received. For this reason, the cell drop detection unit 7-1 can detect the presence or absence of a cell drop for each switch path by checking the continuity of the sequence number for each switch path. For example, in the case of FIG. 5, when a cell with sequence number 8 is received before a cell with sequence number 4 after receiving a cell with sequence number 0, it is immediately detected that the cell with sequence number 4 has dropped. can do.

“Second Embodiment”
Referring to FIG. 3, another example of the switch device to which the present invention is applied has a configuration in which a plurality of unit switches are connected in a plurality of stages between L input units and N output units. Yes.

  The input units 1-1-1 to 1-1-L are connected to the input ports of the switch unit 3-2, and the output ports of the switch unit 3-2 are the output units 1-5-1 to 1-5- Connected to N. That is, the cells output from the input units 1-1-1 to 1-1-L reach the output units 1-5-1 to 1-5-N via the switch unit 3-2. The switch unit 3-2 is a switch configured by connecting a plurality of unit switches in multiple stages (eg, cross connection), and there are a plurality of switch paths from a certain input unit to a certain output unit.

  The output units 1-5-1 to 1-5-N receive cells from the input unit via the switch unit, check the cell order for each of the input units 1-1-1 to 1-1-L, A reordering processing unit 7-5 that performs processing for adjusting the correct cell order when cell order is reversed, and a cell loss detection unit 7-1 that monitors cell loss for each switch path through which the cell passes.

  In the switch shown in FIG. 3, when a cell is sent from a certain input unit to a certain output unit, it passes through any one of the unit switches constituting the switch unit. For this reason, as shown in FIG. 4, even when a cell is output from the input unit 1 to the output unit 1, for example, there are a plurality of switch paths. In this case, the cell order is not changed in the same switch path. However, when a cell is transmitted using a different switch path, the cell order may arrive in reverse in the output unit. The reason is that when a buffer or the like exists in the switch path, the arrival time from the input unit to the output unit may be different for each switch path. Further, cell dropping may occur due to buffer overflow or the like.

  In the case of the present embodiment, the cell drop detection unit 7-1 provided in each output unit includes a cell path order in each input unit and a cell for each output unit serving as a cell destination in each input unit. By recognizing the order of sequence numbers assigned to cells passing through the same switch path from the sequence numbers assigned to the cells, and checking the continuity of the sequence numbers for each switch path passed by the cells, Monitor. The reordering processing unit 7-5 performs the reordering process in consideration of the cell drop detection result by the cell drop detection unit.

  In the present embodiment, as the order of switch paths for sending cells in each input unit, a method of sending cells in order to each switch path is used for each output unit serving as a cell destination in each input unit. As a simple example, in a switch having four switch paths, the order in which a certain input unit A sends cells to a certain output unit B is the same as the order described in FIG.

  When each input unit sends out a cell as described above, in the cell drop detection unit 7-1, from the number of switch paths and the sequence number assigned to the cell for each output unit that is the destination of the cell, It is possible to recognize a series of cells passing through the same switch path. For example, in the case of FIG. 5, when a cell with sequence number 0 is received from switch path 0, it is understood that cells with sequence number 4, sequence number 8,. Similarly, if a cell with sequence number 1 is received from switch path 1, a cell with sequence number 1 + 4M is received from switch path 1 and a cell with sequence number 2 is received from switch path 2. If there is a cell with sequence number 2 + 4M from switch path 2 and a cell with sequence number 3 from switch path 3, then switch path 3 will subsequently receive a cell with sequence number 3 + 4M. It can be seen that the cell is received. For this reason, the cell drop detection unit 7-1 can detect the presence or absence of a cell drop for each switch path by checking the continuity of the sequence number for each switch path. For example, in the case of FIG. 5, if a cell with sequence number 8 is received before a cell with sequence number 4 after receiving a cell with sequence number 0, it is detected that a cell with sequence number 4 has dropped. can do.

  Next, an example of the cell drop detection unit 7-1 will be described in detail with reference to the drawings.

  Referring to FIG. 6, the cell drop detection unit 7-1 according to the first embodiment includes an input unit detection unit 7-2, a switch path analysis unit 7-3, and a continuity monitoring unit 7-4.

  The input unit detector 7-2 extracts the input unit number and sequence number for identifying the input unit that is the source of the received cell from the cell header information, and the input unit number is the switch between the continuity monitoring unit 7-4 and the switch. The sequence number is sent to the path analysis unit 7-3, and the sequence number is sent to the switch path analysis unit 7-3.

  The switch path analyzing unit 7-3 is a means for detecting the switch path number and the sequence number for each switch path based on the input unit number and the sequence number received from the input unit detecting unit 7-2. The path number and the sequence number for each switch path are output to the continuity monitoring unit 7-4.

  The continuity monitoring unit 7-4 performs cell drop monitoring for each input unit and each switch path based on the received input unit number, switch path number, and sequence number for each switch path, and the monitoring result (cell drop The presence / absence and the number of dropped cells) are sent to the Reordering processing unit 7-5.

  The reordering processing unit 7-5 performs the reordering process on the received cell based on the sequence number for each input unit, and when the continuity monitoring unit 7-4 notifies that there is a cell drop, Perform the reordering process in consideration and perform the process so that the reordering process is not delayed.

  Next, the operation of the cell drop detection unit 7-1 of the present embodiment will be described.

  The input unit detection unit 7-2 extracts the input unit number and the sequence number that are the transmission source of the received cell from the cell header information, and the input unit number is obtained from the continuity monitoring unit 7-4 and the switch path analysis unit 7 -3 and the sequence number are sent to the switch path analysis unit 7-3.

  The switch path analysis unit 7-3 detects the switch path number and the switch path monitoring sequence number from the received input unit number and sequence number, and sends them to the continuity monitoring unit 7-4. In the case of the switch device of each embodiment described above, the switch path number and the switch path monitoring sequence in the switch path analysis section 7-3 are sent from the input section to the switch path one cell at a time. The number detection process can be realized by using a divider as shown in FIG. 7, for example. That is, by dividing the sequence number of the input cell by the number of switch paths (4 in the example of FIG. 7), the quotient of the division result can be regarded as the sequence number for each switch path, and the remainder can be regarded as the switch path number.

  The continuity monitoring unit 7-4 monitors the continuity of the sequence number of the received cell for each input unit of the cell transmission source and for each switch path. It is determined that there was. For example, as shown in FIG. 8, when a cell with sequence number 4 is lost in switch path 0, 2 is received as the sequence number for each switch path in switch path 0. It can be detected that it has fallen.

  The reordering processing unit 7-5 monitors the sequence number added to each input unit that is a cell transmission source and performs the reordering process. If there is a cell drop, the reordering process will be stopped by waiting for the dropped cell forever. .

  Referring to FIG. 9, the cell drop detection unit 7-1 according to the second embodiment is compared with the cell drop detection unit 7-1 according to the first embodiment illustrated in FIG. In addition to 7-2, the switch path analyzing unit 7-3 and the continuity monitoring unit 7-4, it further differs in that it has a monitoring result insertion unit 7-6.

  The monitoring result insertion unit 7-6 inputs and receives the cell and the monitoring result of the continuity monitoring unit 7-4 (whether there is a cell drop, the number of dropped cells, the source input interface (input unit number), etc.) The monitoring result is inserted into the cell header information and sent to the Reordering processing unit 7-5. The cell into which the monitoring result is inserted is a cell that has led to the deriving of the monitoring result. For example, in the case of FIG. 8, when the cell of sequence number 8 is processed, the continuity monitoring unit 7-4 detects that the cell of sequence number 4 is missing in the switch path 0. Is inserted into the header information (cell drop monitoring result). In addition to the case where a cell drop is detected, the monitoring result may be inserted into the cell header information even when no cell drop is detected. For example, in the case of FIG. 8, when the cell with sequence number 5 is processed, the cell with sequence number 1 has been received before that, so the information “cell missing” in the header information of the cell with sequence number 5 (cell A drop monitoring result) may be inserted.

  In the reordering process 7-5, the cell drop monitoring result (presence / absence of cell drop, number of dropped cells, etc.) is recognized from the cell header information received from the monitoring result insertion unit 7-6, and the reordering process is performed.

  Referring to FIG. 10, the cell drop detection unit 7-1 according to the third embodiment is compared with the cell drop detection unit 7-1 according to the first embodiment shown in FIG. In addition to 7-2, switch path analysis unit 7-3 and continuity monitoring unit 7-4, there is a further difference in having a dummy cell insertion unit 7-7.

  The dummy cell insertion unit 7-7 inputs the cell and the monitoring result of the continuity monitoring unit 7-4 (presence / absence of cell drop, number of dropped cells, etc.) and complements the dummy cell for the cell drop in the received cell flow To the Reordering processing unit 7-5. The dummy cell is a cell that substitutes for the dropped cell. For example, in the header information of the dummy cell, a sequence number, an input unit number, and a destination output unit number that the dropped cell should have are set. The contents of the cells other than the header information may be arbitrary.

  In the reordering process 7-5, it is possible to avoid stopping the reordering process by performing the reordering process including the dummy cell received from the dummy cell insertion unit 7-7.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above examples, and various other additions and modifications can be made. For example, in the above embodiment, the switch described in FIG. 1 and FIG. 3 is used as an application example, and each input unit sends cells to each switch path in turn for each destination output unit. Explained. However, according to the present invention, it is only necessary that the order of switch paths for sending cells in each input unit is determined in advance, and it is not always necessary to output cells in order to each switch path.

  In the above embodiment, the switch device does not particularly hold information on the order of switch paths for sending cells in each input unit, but information on the order of switch paths for sending cells in each input unit. May be prepared and managed and referenced in the switch path analysis unit 7-3 of the cell drop detection unit 7-1. FIG. 11 shows an example of such a management table. In the management table of this example, for each input unit, which cell of which sequence number is output to which switch path is described. For example, the input unit 1 outputs the cell with the sequence number 0 to the switch path 0, the cell with the sequence number 1 to the switch path 2, and the cell with the sequence number 2 to the switch path 4.

It is a block diagram of a switch device concerning a 1st embodiment of the present invention. It is explanatory drawing of the several switch path from the input part in the switch apparatus which concerns on the 1st Embodiment of this invention to an output part. It is a block diagram of the switch apparatus concerning the 2nd Embodiment of this invention. It is explanatory drawing of the several switch path from the input part in the switch apparatus which concerns on the 2nd Embodiment of this invention to an output part. FIG. 4 is a diagram illustrating an example of an order in which a certain input unit transmits cells to a certain output unit in an FOFF manner in a load-balanced switch having four switch paths. It is a block diagram of the 1st Example of the cell drop detection part of this invention. It is a block diagram which shows the operation example of the switch path analysis part in the cell drop detection part of this invention. It is a block diagram which shows the operation example of the switch path analysis part in the cell drop detection part of this invention. It is a block diagram of the 2nd Example of the cell drop detection part of this invention. It is a block diagram of the 3rd Example of the cell drop detection part of this invention. It is a figure which shows the example of the management table which can understand the response | compatibility of the input part managed by the switch path analysis part in the cell drop detection part of this invention, a sequence number, and a switch path.

Explanation of symbols

1-1-1 to 1-1-L ... Input section
1-2… The front crossbar switch (XBAR Switch)
1-3-1 to 1-3k ... Intermediate stage buffer (Buffer)
1-4… Roller crossbar switch (XBAR Switch)
1-5-1 to 1-5-N ... Output section
2-1-1 to 2-1-2k: Switch path from input 1 to output 1
3-1-1 ~ 3-1-L ... Input section
3-2 ... Switch part
3-3-1 to 3-3-3 ... Output section
7-1 ... Cell drop detector
7-2… Input detector
7-3… Switch path analysis unit
7-4… Continuity monitoring unit
7-5… Reordering processing part
7-6… Monitoring result insertion part
7-7… Dummy cell insertion part

Claims (18)

In a switching device that includes a plurality of input units, a plurality of output units, and a switch unit that connects each input unit and each output unit, and there are a plurality of switch paths from one input unit to one output unit,
Assigned to the cells via the same switch path from the order of switch paths for sending the cells at each input unit and the sequence numbers assigned to the cells for each output unit serving as the cell destination at each input unit. A switch device comprising cell drop detection means for recognizing cell drop by recognizing the sequence number sequence to be performed and checking the continuity of the sequence number for each switch path.   2. The switch device according to claim 1, wherein the switch unit has a load balance type switch configuration including a plurality of intermediate stage buffers.   3. The switch device according to claim 2, wherein each input unit and each intermediate stage buffer, and each intermediate stage buffer and each output unit are mesh-connected.   3. The switch device according to claim 2, wherein each input unit and each intermediate stage buffer, and each intermediate stage buffer and each output unit are connected by a crossbar switch.   2. The switch device according to claim 1, wherein the switch unit has a configuration in which unit switches are arranged in a plurality of stages.   6. The switch device according to claim 1, wherein the cell drop detection unit obtains an input unit number and a sequence number for identifying an input unit that is a transmission source of the received cell from cell header information. An input unit detection unit to be extracted, a switch path analysis unit to detect a switch path number and a sequence number for each switch path from the input unit number and the sequence number extracted by the input unit detection unit, and the input unit detection unit A continuity monitoring unit that performs cell drop monitoring for each input unit and for each switch path from the input unit number extracted in step 1 and the switch path number detected by the switch path analysis unit and the sequence number for each switch path. A switch device characterized by that.   The switch device according to any one of claims 1 to 6, wherein the cell drop detection means performs a cell complementing process when a cell drop is detected.   8. The switch device according to claim 7, wherein a dummy cell is inserted as a cell complementing process.   8. The switch device according to claim 7, wherein information of a dropped cell is given to the cell in which the dropped cell is detected as the cell complementing process. A cell drop in a switching device that includes a plurality of input units, a plurality of output units, and a switch unit that connects each input unit and each output unit, and has a plurality of switch paths from one input unit to one output unit. In the detection method,
The cell drop detection means provided in the output unit is the same from the sequence of switch paths for sending cells in each input unit and the sequence number assigned to the cell for each output unit serving as the cell destination in each input unit. A cell drop detection method characterized in that cell drop monitoring is performed by recognizing the order of sequence numbers assigned to cells passing through a switch path and checking the continuity of the sequence numbers for each switch path.   11. The cell drop detection method according to claim 10, wherein the switch section has a load balance type switch configuration including a plurality of intermediate stage buffers.   12. The cell loss detection method according to claim 11, wherein each input unit and each intermediate stage buffer, and each intermediate stage buffer and each output unit are mesh-connected.   12. The cell drop detection method according to claim 11, wherein each input unit and each intermediate stage buffer, and each intermediate stage buffer and each output part are connected by a crossbar switch. .   11. The cell drop detection method according to claim 10, wherein the switch section has a configuration in which a plurality of unit switches are arranged.   15. The cell drop detection method according to claim 10, wherein the cell drop detection means uses an input part number and a sequence number for identifying an input part that is a source of a received cell as a cell header. Extracted from information, detects a switch path number and a sequence number for each switch path from the extracted input part number and sequence number, and extracts the extracted input part number, the detected switch path number, and a sequence for each switch path A cell drop detection method, wherein cell drop monitoring is performed for each input unit and for each switch path from a number.   The cell drop detection method according to any one of claims 10 to 15, wherein the cell drop detection means performs cell complementation processing when a cell drop is detected.   17. The cell drop detection method according to claim 16, wherein a dummy cell is inserted as the cell complementing process.   17. The cell drop detection method according to claim 16, wherein the dropped cell information is added to the cell where the cell drop is detected as the cell complementing process.

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