JP2013093834A - Frame transfer device and frame transfer method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for efficiently suppressing failure occurrence associated with queuing buffer congestion in a frame transfer device with a plurality of queuing buffers.SOLUTION: A frame transfer device comprises: three or more queuing buffers; a storage unit which stores a priority for reading frames from each queuing buffer; a buffer reading unit which reads and transfers a frame according to the priority; and a buffer writing unit which writes a received frame in any of the plurality of queuing buffers according to the information included in the frame. If it detects a congestion state of any of the first queuing buffers, the buffer writing unit replaces the priority of the first queuing buffer with the priority of a second queuing buffer (queuing buffer having a priority one higher than the first queuing buffer) when a prescribed condition is met.

Description

  The present invention relates to a frame transfer apparatus and a frame transfer method.

  2. Description of the Related Art Conventionally, in a company data center or the like, a frame transfer apparatus that transfers frames between a server and a user terminal or between servers is known. Here, “frame” means a data format used in communication in a network. Many frame transfer apparatuses are provided with a plurality of queuing buffers that are memories for temporarily storing received frames. This queuing buffer is used when performing frame transfer processing or when the frame transfer processing speed of the frame transfer apparatus is different from the line speed.

  With regard to this queuing buffer, when frame storage is concentrated in one queuing buffer, there is a problem that a part of the frame is discarded beyond the allowable amount of the queuing buffer. In order to avoid this problem, if there are multiple queuing buffers for storing real-time communication frames such as audio data and moving image data, the queuing buffer will be used when the accumulated amount of frames reaches the threshold. There is known a congestion control method for preferentially reading out frames from the above (Patent Documents 1, 2, and 3).

JP 2004-72569 A JP-A-11-3250 JP 2001-186181 A

  However, in the prior art, when a plurality of queuing buffers are in a congested state, sufficient control cannot be performed as to which queuing buffer is given higher priority. Also, when multiple queuing buffers store frames with different priorities, when a congested state occurs in a low-priority queuing buffer, which queuing buffer should be preferentially read Could not perform enough control. As described above, in the frame transfer apparatus including a plurality of queuing buffers, there is still room for improvement with respect to a technique for efficiently suppressing the occurrence of problems associated with congestion of the queuing buffers.

  The present invention has been made to solve at least a part of the above-described problems, and in a frame transfer apparatus having a plurality of queuing buffers, efficiently suppresses the occurrence of problems associated with congestion of the queuing buffers. It aims at providing the technique for.

  In order to solve at least a part of the above problems, the present invention can be realized as the following aspects or application examples.

[Application Example 1]
A frame transfer device,
Three or more queuing buffers capable of storing frames;
A storage unit for storing relative priorities for reading frames from each of the queuing buffers;
A buffer read unit that reads and transfers frames from the queuing buffer according to the priority order; and
A buffer writing unit that writes a frame received from the outside of the frame transfer device to any one of the plurality of queuing buffers according to information included in the frame, and
When the buffer writing unit detects a congestion state of any of the first queuing buffers, the buffer writing unit has a higher priority than the first queuing buffer and the first queuing buffer when a predetermined condition is satisfied. Is a frame transfer apparatus for switching the priority order of the second queuing buffer that is one level higher.

  According to this configuration, in a frame transfer apparatus including three or more queuing buffers, when any of the queuing buffers becomes congested, the relative priority of the congested queuing buffers is increased by one. It is possible to efficiently suppress the occurrence of problems associated with congestion of the ining buffer.

[Application Example 2]
In the frame transfer apparatus described in Application Example 1,
The frame transfer device, in which the buffer writing unit determines that the predetermined condition is not satisfied when the second queuing buffer is in a congested state, and does not change the priority order.

  According to this configuration, when the congestion state of the queuing buffer is detected, if the queuing buffer that is one priority higher than the queuing buffer is already congested, the two queuing buffers Since the order of priority is not exchanged between them, it is possible to efficiently suppress the occurrence of problems due to congestion of the queuing buffer.

[Application Example 3]
In the frame transfer apparatus according to Application Example 1 or Application Example 2,
The buffer writing unit, when the priority of the first queuing buffer is lowered by one due to the change of the priority performed in the past,
(I) Eliminate the change of priority, and
(Ii) A frame transfer apparatus that switches priority between the first queuing buffer and the second queuing buffer when the second queuing buffer is not congested.

  According to this configuration, when the queuing buffer whose priority is lowered by 1 due to the change of the priorities in the past becomes congested, the priority of the queuing buffer is increased by one and returned to the original state. If the queuing buffer that is one priority higher than the queuing buffer is not in a congested state, the priority is replaced with the queuing buffer that is one priority higher, which is associated with the congestion of the queuing buffer. The occurrence of defects can be efficiently suppressed.

[Application Example 4]
In the frame transfer device according to any one of Application Examples 1 to 3,
When the buffer reading unit detects the cancellation of the congestion state of the first queuing buffer whose priority has been increased by one due to the switching of the priorities performed in the past, the buffer reading unit cancels the switching of the priorities. Frame transfer device.

  According to this configuration, when the congestion state of the queuing buffer whose priority is increased by 1 is canceled by the replacement of the priorities of the past, the priority of the queuing buffer is decreased by 1 and returned to the original state. It is possible to efficiently suppress the occurrence of problems associated with congestion of the ining buffer.

[Application Example 5]
In the frame transfer apparatus according to any one of Application Examples 1 to 4,
The storage unit stores information indicating the current priority of each queuing buffer and information indicating the initial priority of each queuing buffer;
In the information indicating the current priority level, the buffer writing unit indicates the priority level of the second queuing buffer that is one priority higher than the first queuing buffer in the initial priority level. Rewriting the information indicating the current priority so that the priority is one lower than the first queuing buffer;
The buffer reading unit is a frame transfer device that reads and transfers a frame from the queuing buffer according to the current priority order.

  According to this configuration, the storage unit stores the information indicating the current priority of each queuing buffer and the information indicating the initial priority of each queuing buffer, thereby accompanying the congestion of the queuing buffer. The occurrence of defects can be efficiently suppressed.

[Application Example 6]
A frame transfer method,
A step of reading frames from three or more queuing buffers according to the priority order stored in the storage unit and transferring them;
Writing a frame to any of the plurality of queuing buffers according to information contained in the frame;
When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer having a higher priority than the first queuing buffer when a predetermined condition is satisfied. And a step of exchanging the priorities of the two queuing buffers.

  According to this configuration, in a frame transfer apparatus including three or more queuing buffers, when any of the queuing buffers becomes congested, the relative priority of the congested queuing buffers is increased by one. It is possible to efficiently suppress the occurrence of problems associated with congestion of the ining buffer.

[Application Example 7]
A frame transfer device,
Three or more queuing buffers capable of storing frames;
A storage unit for storing relative priorities for reading frames from each of the queuing buffers;
A buffer read unit that reads and transfers frames from the queuing buffer according to the priority order; and
A buffer writing unit that writes a frame received from the outside of the frame transfer device to any one of the plurality of queuing buffers according to information included in the frame, and
The storage unit stores a congestion threshold and a congestion elimination threshold set in each of the queuing buffers,
The buffer writing unit
(I) The congestion state of the queuing buffer is detected when the accumulated amount of frames exceeds the congestion threshold, and the congestion state of the queuing buffer is resolved when the accumulated amount of frames falls below the congestion elimination threshold. Detect
(Ii) When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer have one priority when a predetermined condition is satisfied. Change the priority of the upper second queuing buffer,
(Iii) A frame transfer apparatus that reduces the congestion elimination threshold set in the first queuing buffer.

  According to this configuration, in a frame transfer apparatus including three or more queuing buffers, when any of the queuing buffers becomes congested, the relative priority of the congested queuing buffers is increased by one. It is possible to efficiently suppress the occurrence of problems associated with congestion of the ining buffer. In addition, if any queuing buffer becomes congested, the congestion elimination threshold set for the congested queuing buffer is decreased, so that the occurrence of problems associated with queuing buffer congestion can be further suppressed. it can.

[Application Example 8]
A frame transfer device,
Three or more queuing buffers capable of storing frames;
A storage unit for storing relative priorities for reading frames from each of the queuing buffers;
A buffer read unit that reads and transfers frames from the queuing buffer according to the priority order; and
A buffer writing unit that writes a frame received from the outside of the frame transfer device to any one of the plurality of queuing buffers according to information included in the frame, and
The storage unit stores a congestion threshold and a congestion elimination threshold set in each of the queuing buffers,
The buffer writing unit
(I) The congestion state of the queuing buffer is detected when the accumulated amount of frames exceeds the congestion threshold, and the congestion state of the queuing buffer is resolved when the accumulated amount of frames falls below the congestion elimination threshold. Detect
(Ii) When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer have one priority when a predetermined condition is satisfied. Change the priority of the upper second queuing buffer,
(Iii) A frame transfer apparatus that increases the congestion threshold set in the queuing buffer when a queuing buffer that is not congested for a predetermined time or more is detected.

  According to this configuration, in a frame transfer apparatus including three or more queuing buffers, when any of the queuing buffers becomes congested, the relative priority of the congested queuing buffers is increased by one. It is possible to efficiently suppress the occurrence of problems associated with congestion of the ining buffer. In addition, if a queuing buffer that has not been congested for a predetermined time or more is detected, the congestion threshold set in the queuing buffer is increased, so that the occurrence of problems associated with congestion of the queuing buffer can be further suppressed. it can.

[Application Example 9]
A frame transfer method,
A step of reading frames from three or more queuing buffers according to the priority order stored in the storage unit and transferring them;
Writing a frame to any of the plurality of queuing buffers according to information contained in the frame;
Detecting the congestion state of the queuing buffer when the accumulated amount of frames exceeds the congestion threshold, and detecting the cancellation of the congestion state of the queuing buffer when the accumulated amount of frames falls below the congestion elimination threshold;
When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer having a higher priority than the first queuing buffer when a predetermined condition is satisfied. And a step of switching the priority order of the two queuing buffers to reduce a congestion elimination threshold set in the first queuing buffer.

  According to this configuration, in a frame transfer apparatus including three or more queuing buffers, when any of the queuing buffers becomes congested, the relative priority of the congested queuing buffers is increased by one. It is possible to efficiently suppress the occurrence of problems associated with congestion of the ining buffer. In addition, if any queuing buffer becomes congested, the congestion elimination threshold set for the congested queuing buffer is decreased, so that the occurrence of problems associated with queuing buffer congestion can be further suppressed. it can.

[Application Example 10]
A frame transfer method,
A step of reading frames from three or more queuing buffers according to the priority order stored in the storage unit and transferring them;
Writing a frame to any of the plurality of queuing buffers according to information contained in the frame;
Detecting the congestion state of the queuing buffer when the accumulated amount of frames exceeds the congestion threshold, and detecting the cancellation of the congestion state of the queuing buffer when the accumulated amount of frames falls below the congestion elimination threshold;
When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer having a higher priority than the first queuing buffer when a predetermined condition is satisfied. A step of changing the priority of the queuing buffers of 2;
And a step of increasing a congestion threshold set in the queuing buffer when a queuing buffer that has not been congested for a predetermined time is detected.

  According to this configuration, in a frame transfer apparatus including three or more queuing buffers, when any of the queuing buffers becomes congested, the relative priority of the congested queuing buffers is increased by one. It is possible to efficiently suppress the occurrence of problems associated with congestion of the ining buffer. In addition, if a queuing buffer that has not been congested for a predetermined time or more is detected, the congestion threshold set in the queuing buffer is increased, so that the occurrence of problems associated with congestion of the queuing buffer can be further suppressed. it can.

  The present invention can be realized in various forms other than those described above. For example, a network system including a frame transfer apparatus, a frame transfer apparatus control method, a queuing buffer control method, and the like The present invention can be realized in the form of a computer program for realizing the control method and a storage medium on which the computer program is recorded. The frame transfer apparatus according to the present invention can be applied in combination with other members as appropriate.

It is explanatory drawing which illustrated the network system comprised including the frame transmission apparatus which concerns on 1st Example. It is explanatory drawing for demonstrating schematic structure of a frame transfer apparatus. It is explanatory drawing for demonstrating the identification method of the priority class to which a flame | frame belongs. It is explanatory drawing for demonstrating the content of the buffer status management table. It is explanatory drawing for demonstrating the detection method of the congestion state of a queuing buffer. It is explanatory drawing for demonstrating the method to detect cancellation | release of the congestion state of a queuing buffer. 5 is a flowchart showing a processing flow of a buffer writing unit 150. It is the flowchart which showed the flow of the priority change setting cancellation | release process in step S107 of FIG. It is explanatory drawing for demonstrating the buffer status management table at the time of the priority change setting cancellation | release process of step S107. It is the flowchart which showed the flow of the priority change setting process in step S111 of FIG. It is explanatory drawing for demonstrating the buffer status management table at the time of a priority change setting process. 6 is a flowchart showing a processing flow of a buffer reading unit 160. 13 is a flowchart illustrating a flow of priority change setting release processing in step S408 of FIG. It is explanatory drawing for demonstrating the buffer status management table at the time of the priority change setting cancellation | release process of step S408. FIG. 10 is a first explanatory diagram for illustrating the operation of the frame transfer apparatus. FIG. 16 is an explanatory diagram for explaining a buffer state management table during the operation of FIG. 15; FIG. 10 is a second explanatory diagram for illustrating the operation of the frame transfer apparatus. FIG. 18 is an explanatory diagram for explaining a buffer state management table during the operation of FIG. 17; FIG. 10 is a third explanatory diagram for illustrating the operation of the frame transfer apparatus. FIG. 20 is an explanatory diagram for explaining a buffer state management table during the operation of FIG. 19; It is explanatory drawing for demonstrating schematic structure of the frame transmission apparatus concerning 2nd Example. It is explanatory drawing for demonstrating the content of the buffer threshold value management table. It is the flowchart which showed the flow of the process of the buffer writing part 150 in 2nd Example. It is the flowchart which showed the flow of the congestion threshold value Th1 change determination process in step S120 of FIG. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of the congestion threshold value Th1 change determination process of step S120. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of the congestion threshold value Th1 change determination process of step S120. It is the flowchart which showed the flow of the congestion threshold value Th1 change cancellation process in step S140 of FIG. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of congestion threshold value Th1 change cancellation process of step S140. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of congestion threshold value Th1 change cancellation process of step S140. It is the flowchart which showed the flow of the congestion cancellation threshold value Th2 change determination process in step S150 of FIG. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of the congestion elimination threshold value Th2 change determination process of step S150. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of the congestion elimination threshold value Th2 change determination process of step S150. It is the flowchart which showed the flow of the congestion cancellation threshold value Th2 change cancellation process with respect to the low-order priority class in step S160 of FIG. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of congestion cancellation threshold value Th2 change cancellation | release process of step S160. It is the flowchart which showed the flow of the process of the buffer reading part 160 in 2nd Example. It is the flowchart which showed the flow of the congestion cancellation threshold value Th2 change cancellation process with respect to the object priority class in step S420 of FIG. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of the congestion cancellation threshold value Th2 change cancellation | release process of step S420. It is the 1st explanatory view for illustrating operation of the frame transfer device of the 2nd example. FIG. 39 is an explanatory diagram for describing a buffer threshold value management table during the operation of FIG. 38; It is the 2nd explanatory view for illustrating operation of the frame transfer device of the 2nd example. It is explanatory drawing for demonstrating the buffer threshold value management table at the time of operation | movement of FIG. It is the 3rd explanatory view for illustrating operation of the frame transfer device of the 2nd example. FIG. 43 is an explanatory diagram for describing a buffer threshold value management table during the operation of FIG. 42; It is the 4th explanatory view for illustrating operation of the frame transfer device of the 2nd example. FIG. 45 is an explanatory diagram for describing a buffer threshold value management table during the operation of FIG. 44; It is the 5th explanatory view for illustrating operation of the frame transfer device of the 2nd example. FIG. 47 is an explanatory diagram for describing a buffer threshold value management table during the operation of FIG. 46;

A. First embodiment:
FIG. 1 is an explanatory diagram illustrating a network system including a frame transfer apparatus according to the first embodiment. The network system 10 is a system constructed in a company or the like, and includes a frame transfer device 100, a user terminal 200, a server 300, a storage 400, and a setting monitoring terminal 500. The frame transfer apparatus 100 is connected to the user terminal 200, the server 300, the storage 400, and the setting monitoring terminal 500, and relays the exchange of frames between the apparatuses.

  The frame transfer apparatus 100 classifies the frames received from the respective apparatuses into a plurality of classes according to the transfer priority, and preferentially transfers the frames belonging to the higher priority class. On the other hand, the frame transfer apparatus 100 temporarily switches the class priority in accordance with the amount of received frames for each class. Hereinafter, in this embodiment, as described above, the classification of frames according to the transfer priority is referred to as “priority class” or simply “class”. Specific operations of the frame transfer apparatus 100 will be described later.

  In response to an application request from the user terminal 200, the server 300 acquires various data such as image data and moving image data stored in the storage 400 and transfers the data to the user terminal 200. The setting monitoring terminal 500 is used for managing settings and states of the frame transfer apparatus 100.

FIG. 2 is an explanatory diagram for explaining a schematic configuration of the frame transfer apparatus.
The frame transfer apparatus 100 includes a frame transfer unit 110 and a plurality of line interface units 131 to 133. The frame transfer unit 110 is connected to the line interface units 131 to 133, and performs frame transfer between the line interface units 131 to 133. In this embodiment, the line interface unit 131 is connected to the storage 400, the line interface unit 132 is connected to the server 300, and the line interface unit 133 is connected to the user terminal 200.

  The frame transfer unit 110 includes a queuing buffer group 140, a buffer writing unit 150, a buffer reading unit 160, a priority class table 170, and a buffer state management table 180. The queuing buffer group 140 includes a plurality (four in this case) of queuing buffers 141 to 144 for storing frames. Hereinafter, the four queuing buffers 141 to 144 are also referred to as a first queuing buffer 141, a second queuing buffer 142, a third queuing buffer 143, and a fourth queuing buffer 144, respectively. The priority class table 170 and the buffer status management table 180 are stored in a storage unit 190 configured by a memory or the like.

  Each of the queuing buffers 141 to 144 is in one-to-one correspondence with four priority classes having different priorities. That is, frames belonging to the same priority class are stored in the queuing buffers 141 to 144 by the buffer writing unit 150. In addition, the buffer reading unit 160 preferentially reads and transfers a frame from the priority class queuing buffer having a high priority.

  When the frame transfer apparatus 100 receives a frame, the buffer writing unit 150 stores the frame in a priority class queuing buffer corresponding to information included in the frame (hereinafter also referred to as “in-frame information”). The buffer writing unit 150 refers to the priority class table 170 to identify the priority class to which the frame belongs.

  FIG. 3 is an explanatory diagram for explaining a method for specifying a priority class to which a frame belongs. FIG. 3A is an explanatory diagram for explaining a schematic structure of a frame. As shown in FIG. 3A, the frame includes in-frame information such as a destination, a transmission source, a user type, an application type, and application data. The application type is information that can identify the type of application data, and is information for specifying whether the application data is, for example, audio data, moving image data, still image data, character data, or the like. In this embodiment, a port number included in the header of TCP or UDP protocol is used as the application type. For example, the buffer writing unit 150 reads the application type from the frame and refers to the priority class table 170 to identify the priority class to which the frame belongs.

  FIG. 3B is an explanatory diagram for explaining the contents of the priority class table. The priority class table 170 includes two fields of an application type F11 and a priority class F12, and shows a correspondence relationship between the application type and the priority class. Here, queuing buffers 141 to 144 corresponding to the priority class are shown as the priority class. In the priority class table 170, for example, in the entry E11, the audio data and the queuing buffer 141 are associated with each other. In entry E12, the moving image data and the queuing buffer 142 are associated with each other. When the buffer writing unit 150 specifies that the frame received by the frame transfer apparatus 100 is audio data, the buffer writing unit 150 refers to the priority class table 170 and stores the frame in the queuing buffer 141. The contents of the priority class table 170 may be configured to be arbitrarily settable by the setting monitoring terminal 500.

  The buffer reading unit 160 reads and transfers the frames stored in the queuing buffers 141 to 144. At this time, the buffer reading unit 160 reads frames preferentially from the queuing buffer corresponding to the priority class having a high priority, and performs transfer. The buffer reading unit 160 refers to the buffer state management table 180 to identify the priority of the priority class corresponding to each queuing buffer.

  FIG. 4 is an explanatory diagram for explaining the contents of the buffer status management table. The buffer status management table 180 includes five fields: a priority class F21, a current priority F22, an initial priority F23, a congestion flag F24, and a priority change setting flag F25. The priority class F21 indicates the queuing buffers 141 to 144 as with the priority class F12 (FIG. 3) of the priority class table 170.

  The current priority F22 indicates the relative priority of each priority class. That is, the priority order of the queuing buffers read by the buffer reading unit 160 is shown. Here, the larger the current priority value is, the higher the priority is. Therefore, FIG. 4 shows a state in which the first queuing buffer 141 has the highest priority, the priority decreases in order, and the fourth queuing buffer 144 has the lowest priority. As will be described later, the value of the current priority F22 is appropriately rewritten by the buffer writing unit 150 and the buffer reading unit 160. The initial priority F23 is a relative priority of each priority class set in advance via the setting monitoring terminal 500, and is used as an initial setting value of the current priority F22.

  The congestion flag F24 indicates whether or not each priority class queuing buffer is in a congestion state. Here, “0” is set in the priority class that is not in the congestion state, and “1” is set in the congestion state. As described later, when the buffer writing unit 150 detects the congestion state of the queuing buffer, the congestion flag F24 is set to “1” in the corresponding priority class. Further, as will be described later, when the buffer reading unit 160 detects the cancellation of the congestion state of the queuing buffer, the congestion flag F24 is set to “0” in the corresponding priority class. The cancellation of the congestion state means that the queuing buffer that was in the congestion state is no longer in the congestion state.

  The priority change setting flag F25 indicates whether or not priority change setting is performed in each priority class. The priority change setting is a setting in which the current priority of adjacent priority classes is temporarily replaced, which will be described in detail later. In FIG. 4, “1” is set to the priority class whose current priority is temporarily lowered due to the priority change setting, and “0” is set to the other priority classes. The priority change setting flag F25 is rewritten by the buffer writing unit 150 and the buffer reading unit 160, as will be described later.

  FIG. 5 is an explanatory diagram for explaining a method of detecting a congestion state of the queuing buffer. FIG. 5 shows an example of the second queuing buffer 142 that becomes congested by storing frames. In each of the queuing buffers 141 to 144 including the second queuing buffer 142, a congestion threshold value Th1 for determining whether or not the data accumulation amount exceeds a predetermined amount is set in advance. After storing the frame in the second queuing buffer 142, the buffer writing unit 150 determines whether or not the amount of frame data accumulated in the second queuing buffer 142 exceeds the congestion threshold Th1.

  As shown in the lower part of FIG. 5, when the frame accumulation amount exceeds the congestion threshold Th <b> 1, the buffer writing unit 150 detects a congestion state for the second queuing buffer 142. When detecting the congestion state, the buffer writing unit 150 sets the priority class congestion flag F24 corresponding to the second queuing buffer 142 of the buffer state management table 180 to “1”. The buffer writing unit 150 detects whether or not all the queuing buffers 141 to 144 are congested. The congestion threshold value Th1 can be set to an arbitrary value in advance by the setting monitoring terminal 500. Different values can be set for each of the queuing buffers 141 to 144. Further, the setting monitoring terminal 500 may check the congestion threshold Th1 set for each of the queuing buffers 141 to 144 and the accumulated amount of data.

  FIG. 6 is an explanatory diagram for explaining a method of detecting the cancellation of the congestion state of the queuing buffer. FIG. 6 shows, as an example, the second queuing buffer 142 in which the congestion state has been eliminated by sending frames. In each of the queuing buffers 141 to 144 including the second queuing buffer 142, a congestion elimination threshold Th2 for determining whether or not the accumulated amount of data is below a predetermined amount is set in advance. The congestion elimination threshold Th2 is set to be smaller than the congestion threshold Th1 (Th2 <Th1).

  The buffer read unit 160 determines whether or not the accumulated amount of frame data stored in the second queuing buffer 142 has fallen below the congestion elimination threshold Th2 after reading the frame from the congested second queuing buffer 142. To do. As shown in the lower part of FIG. 6, when the accumulated amount of frames falls below the congestion elimination threshold Th <b> 2, the buffer reading unit 160 detects the congestion state elimination for the second queuing buffer 142. When the buffer reading unit 160 detects the cancellation of the congestion state, the buffer reading unit 160 sets the congestion flag F24 of the priority class corresponding to the second queuing buffer 142 of the buffer state management table 180 to “0”.

  The buffer reading unit 160 detects whether or not the congestion state has been resolved for all the queuing buffers 141 to 144. Note that the congestion elimination threshold Th2 can also be set to an arbitrary value in advance by the setting monitoring terminal 500. Different values can be set for each of the queuing buffers 141 to 144. Moreover, the congestion monitoring threshold Th2 set for each of the queuing buffers 141 to 144 may be confirmed by the setting monitoring terminal 500. Further, the congestion elimination threshold Th2 and the congestion threshold Th1 may be the same value (Th2 = Th1).

  FIG. 7 is a flowchart showing the processing flow of the buffer writing unit 150. When any of the line interface units 131 to 133 receives a frame, the buffer writing unit 150 extracts the frame from the line interface unit (step S101).

  The buffer writing unit 150 reads the application type from the extracted frame. As described above, here, the port number included in the header of the TCP or UDP protocol is read. Thereafter, the buffer writing unit 150 refers to the priority class table 170 (FIG. 3) and identifies the priority class to which the frame belongs from the read application type (step S102). Hereinafter, the priority class specified in step S102 is also referred to as “target priority class”.

  The buffer writing unit 150 writes the frame in the queuing buffer corresponding to the target priority class (step S103). After writing, the buffer writing unit 150 determines whether or not this queuing buffer is in a congested state (step S104). The method of determining whether or not the congestion state is as described with reference to FIG.

  If the buffer writing unit 150 does not detect the congestion state of the queuing buffer (step S104: NO), the buffer writing unit 150 returns to step S101 and waits again until any of the line interface units 131 to 133 receives a frame. . On the other hand, when the congestion state is detected (step S104: YES), the buffer writing unit 150 refers to the buffer state management table 180 (FIG. 4) and determines whether the congestion flag F24 of the target priority class is “1”. Is determined (step S105).

  When the congestion flag F24 of the target priority class is “0” (step S105: NO), the congestion flag F24 of the target priority class is set to “1” (step S106). That is, since the queuing buffer is newly congested by writing the current frame, the congestion flag F24 of the corresponding priority class is switched from “0” to “1”.

  After setting the congestion flag F24 of the target priority class to “1”, the buffer writing unit 150 performs priority change setting release processing for the target priority class and a priority class having a lower initial priority (lower order) than the target priority class. Perform (step S107). The priority change setting release processing for the target priority class and the priority class lower than the target priority class is performed by changing the priority in the priority class having a lower (lower) initial priority F23 than the target priority class or the target priority class. This is a process for canceling this setting. It should be noted that whether or not the priority class has been subjected to the priority change setting can be determined by whether or not the priority change setting flag F25 is “1”. It is a priority class. Details of the priority change setting cancellation processing for priority classes below the target priority class will be described later with reference to FIG.

  Note that when the contents of FIG. 4 are set in the buffer status management table 180 and the second queuing buffer 142 corresponds to the target priority class, the priority class lower than the target priority class is the third queuing. The priority classes corresponding to the buffer 143 and the fourth queuing buffer 144 correspond to this. On the other hand, the priority class corresponding to the first queuing buffer 141 corresponds to a higher priority class than the target priority class.

  In step S105, when the congestion flag F24 of the target priority class is already “1”, or after performing the process of step S107, the buffer writing unit 150 has a higher initial priority F23 than the target priority class (higher order). It is determined whether or not a priority class exists (step S108). Specifically, the buffer writing unit 150 refers to the initial priority F23 of the buffer state management table 180, and determines whether or not a priority class higher than the target priority class exists. If there is no higher priority class (step S108: NO), that is, if the target priority class corresponds to the first queuing buffer 141, the processing of the buffer writing unit 150 returns to step S101.

  When a priority class higher than the target priority class exists (step S108: YES), the buffer writing unit 150 further performs processing such that the congestion flag F24 of the priority class one level higher than the target priority class (directly above) indicates “ 1 ”is determined (step S109). When the congestion flag F24 of the immediately preceding priority class is “1” (step S109: YES), the processing of the buffer writing unit 150 returns to step S101.

  When the congestion flag F24 of the immediately preceding priority class is “0” (step S109: NO), the buffer writing unit 150 determines whether or not priority change setting has been performed in any priority class higher than the target priority class. Is determined (step S110). This determination can be made based on whether or not the priority change setting flag F25 is “1” in any priority class higher than the target priority class.

  When priority change setting is performed in any of the priority classes higher than the target priority class (step S110: YES), the processing of the buffer writing unit 150 returns to step S101. On the other hand, when priority change setting is not performed in all priority classes higher than the target priority class (step S110: NO), the buffer writing unit 150 performs priority change setting processing (step S111). The priority change setting process is a process of switching the current priority of the target priority class and the priority class immediately above the target priority class. Details of the priority change setting process will be described later with reference to FIG. After executing the priority change setting process, the process of the buffer writing unit 150 returns to step S101.

  FIG. 8 is a flowchart showing the flow of priority change setting release processing in step S107 of FIG. FIG. 9 is an explanatory diagram for explaining a buffer state management table at the time of priority change setting release processing in step S107. The buffer writing unit 150 sets the current priority and the initial priority to be equal in the target priority class and each priority class lower than the target priority class by this priority change setting release processing. An example of priority change setting release processing is shown below. Here, the buffer writing unit 150 will be described as including a priority class registration unit capable of setting and registering any one of the priority classes. Note that the priority class registration unit only needs to be configured so that the buffer writing unit 150 can identify any one of the priority classes, and may be configured by a storage unit, a flag, or the like that stores identification information of the priority class. it can.

  The buffer writing unit 150 first registers the target priority class in the priority class registration unit (step S201). This target priority class is the same as the target priority class in step S105 of FIG. Here, the second queuing buffer 142 in FIG. 9 will be described as the target priority class.

  The buffer writing unit 150 refers to the buffer state management table 180 and determines whether the priority change setting flag F25 of the priority class registered in the priority class registration unit (hereinafter also referred to as “registration priority class”) is “1”. Is determined (step S202). In this first step, since the target priority class is registered in the priority class registration unit, it is determined whether or not the priority change setting flag F25 of the target priority class is “1”. In FIG. 9A, the priority change setting flag F25 of the target priority class (second queuing buffer 142) is “1”.

  When the priority change setting flag F25 of the registration priority class is “1” (step S202: YES), the buffer writing unit 150 sets the current priority F22 of the registration priority class to the same value as the initial priority F23 of the registration priority class. (Step S203). Specifically, the buffer writing unit 150 refers to the buffer state management table 180, reads the initial priority F23 of the registration priority class, and writes it to the current priority F22 of the same class. As a result, as shown in FIG. 9B, the current priority of the registration priority class is equal to the initial priority.

  Further, the buffer writing unit 150 sets the current priority F22 of the priority class one level lower than the registered priority class (directly below) to the same value as the initial priority F23 of the same class (step S204). As shown in (c), the current priority and the initial priority are also equal in the priority class one level lower than the registration priority class. Thereafter, as shown in FIG. 9D, the buffer writing unit 150 sets the priority change setting flag F25 of the registration priority class to “0” (step S205).

  In step S202, when the priority change setting flag F25 of the registered priority class is “0”, or after the process of step S205, the buffer writing unit 150 determines whether there is a priority class lower than the registered priority class. Is determined (step S206). If no priority class lower than the registered priority class exists (step S206: NO), the process is terminated.

  On the other hand, when a priority class lower than the registration priority class exists (step S206: YES), the buffer writing unit 150 sets a priority class immediately below (directly below) the current registration priority class as a new registration priority class. Is registered in the priority class registration unit (step S207). Thereafter, the process returns to step S202, and the same processing is performed for the new registration priority class. By the priority change setting release process described above, the priority change setting flag is set to “0” in the target priority class and all priority classes lower than the target priority class, and the current priority F22 is equal to the initial priority F23. Become.

  FIG. 10 is a flowchart showing the flow of priority change setting processing in step S111 of FIG. FIG. 11 is an explanatory diagram for explaining a buffer state management table at the time of priority change setting processing. The buffer writing unit 150 exchanges the current priority of the target priority class and the current priority of the immediately higher priority class by this priority change setting process. An example of priority change setting processing is shown below. Here, the third queuing buffer 143 in FIG. 11A will be described as the target priority class.

  The buffer writing unit 150 sets the current priority F22 of the priority class one level above (directly above) the target priority class to the same value as the initial priority F23 of the target priority class (step S301). Specifically, as shown in FIG. 11B, the buffer writing unit 150 refers to the buffer status management table 180, reads the initial priority F23 of the target priority class, and reads the current priority of the immediately higher priority class. Write to F22.

  Further, the buffer writing unit 150 sets the current priority F22 of the target priority class to the same value as the initial priority F23 of the immediately higher priority class (step S302). Specifically, as illustrated in FIG. 11C, the buffer writing unit 150 refers to the buffer state management table 180, reads the initial priority F23 of the immediately preceding priority class, and reads the current priority of the target priority class. Write to F22. As a result, the current priority F22 of the priority class immediately above the target priority class and the current priority F22 of the target priority class are switched. That is, the priority order immediately above the target priority class and the priority order of the target priority class are switched.

  Thereafter, as shown in FIG. 11D, the buffer writing unit 150 sets the priority class priority change setting flag F25 immediately above the target priority class to “1”. That is, “1” is set to the priority change setting flag F25 of the priority class in which the initial priority is higher than the lower priority class but the current priority is low. Thus, the priority change setting process ends.

  FIG. 12 is a flowchart showing a processing flow of the buffer reading unit 160. The buffer reading unit 160 determines whether or not frames are accumulated for the queuing buffers 141 to 144 (step S401). In the case of accumulation, the buffer reading unit 160 reads the frame accumulated with priority from the queuing buffer having the highest current priority F22 among the accumulated queuing buffers, and the line interface unit 131. To 133 (step S402). The buffer reading unit 160 refers to the destination information (FIG. 3) included in the read frame and determines a transmission destination line interface unit. Here, “read with priority” means that reading is continued until there is no frame accumulation in the queuing buffer with higher current priority, and when there is no more frame accumulation, reading is sequentially performed on the queuing buffer with lower current priority. To do.

  The buffer reading unit 160 determines whether or not the congestion flag F24 of the priority class (hereinafter also referred to as “target priority class”) from which the frame is read in step S402 is “1” (step S403). When the congestion flag F24 of the target priority class is “0” (step S403: NO), the processing of the buffer reading unit 160 returns to step S401.

  On the other hand, when the congestion flag F24 of the target priority class is “1” (step S403: YES), the buffer reading unit 160 determines whether or not the congestion state of the queuing buffer corresponding to the target priority class has been eliminated. (Step S404). If the congestion state of the corresponding queuing buffer has not been resolved (step S404: NO), the processing of the buffer reading unit 160 returns to step S401.

  On the other hand, when the congestion state of the corresponding queuing buffer has been eliminated (step S404: YES), the buffer reading unit 160 sets the congestion flag F24 of the target priority class to “0” (step S405).

  After setting the congestion flag F24 of the target priority class to “0”, the buffer reading unit 160 determines whether or not a priority class having a higher initial priority (higher) than the target priority class exists (step S406). ). When there is a priority class higher than the target priority class (step S406: YES), the buffer reading unit 160 sets the priority change setting flag F25 of the priority class one level higher than the target priority class to “1”. Is determined (step S407).

  If the priority change setting flag F25 of the immediately higher priority class is “1” (step S407: YES), the buffer reading unit 160 performs priority change setting release processing for the immediately higher priority class (step S408). The priority change setting release processing for the immediate priority class is to cancel this setting when the priority change setting has been made in the priority class that is one higher in priority than the target priority class (directly above) It is processing of. Details of the priority change setting release processing for the immediately preceding priority class will be described later with reference to FIG.

  In step S406, when there is no higher priority class than the target priority class (step S406: NO), in step S407, when the priority change setting flag F25 of the immediately higher priority class is “0” (step S407: NO) and when the process of step S408 ends, the process of the buffer reading unit 160 returns to step S401.

  FIG. 13 is a flowchart showing the flow of priority change setting release processing in step S408 of FIG. FIG. 14 is an explanatory diagram for explaining a buffer state management table at the time of priority change setting release processing in step S408. The buffer reading unit 160 cancels the state in which the current priority of the target priority class and the current priority of the priority class immediately above the target priority class are interchanged by this priority change setting release processing. An example of priority change setting release processing is shown below. Here, the third queuing buffer 143 in FIG. 14A will be described as the target priority class.

  The buffer reading unit 160 sets the current priority F22 of the target priority class to the same value as the initial priority F23 of the target priority class (step S501). Specifically, as shown in FIG. The unit 160 refers to the buffer state management table 180, reads the initial priority F23 of the target priority class, and writes it to the current priority F22 of the same class. Thereby, the current priority of the target priority class is equal to the initial priority.

  Furthermore, as shown in FIG. 14C, the buffer reading unit 160 sets the current priority F22 of the priority class one level higher than the target priority class to the same value as the initial priority F23 of the same class. (Step S502). As a result, the current priority and the initial priority are equal in the priority class one level higher than the target priority class. That is, the state in which the current priority F22 of the priority class immediately above the target priority class and the current priority F22 of the target priority class are switched is eliminated. Thereby, the state where the priority of the priority class immediately above the target priority class is lower than the priority of the target priority class is resolved. Thereafter, as shown in FIG. 14D, the buffer reading unit 160 sets the priority change priority flag F25 of the priority class immediately above the target priority class to “0” (step S503). This completes the priority change setting release processing.

  FIG. 15 is a first explanatory diagram for illustrating the operation of the frame transfer apparatus. FIG. 16 is an explanatory diagram for explaining a buffer state management table during the operation of FIG. First, it is assumed that the contents of FIG. 4 are set in the buffer status management table 180.

  In FIG. 15A, the buffer reading unit 160 reads a frame from the first queuing buffer 141 having the highest current priority F22. On the other hand, the buffer writing unit 150 writes a frame to the second queuing buffer 142, and the second queuing buffer 142 is in a congested state.

  When the buffer writing unit 150 detects the congestion state of the second queuing buffer 142 (FIG. 7, step S104), as shown in FIG. 16A, the congestion flag of the priority class corresponding to the second queuing buffer 142 is obtained. F24 is set to “1” (step S106). Thereafter, in step S111, as shown in FIG. 16B, the buffer writing unit 150 performs the priority change setting process, the priority class corresponding to the first queuing buffer 141, the second queuing buffer 142, The current priority F22 of the corresponding priority class is switched. Also, the priority change setting flag F25 of the priority class corresponding to the first queuing buffer 141 is set to “1” (FIG. 10, step S303). As a result, the buffer reading unit 160 reads a frame from the second queuing buffer 142 having the highest priority.

  In FIG. 15B, the frame is read from the second queuing buffer 142 having the highest current priority F22 by the buffer reading unit 160. Further, as a result of reading, the congestion state of the second queuing buffer 142 has been eliminated. When the buffer reading unit 160 detects the cancellation of the congestion state of the second queuing buffer 142 (FIG. 12, step S404), the priority class corresponding to the second queuing buffer 142 as shown in FIG. The congestion flag F24 is set to “0” (step S405). Thereafter, in step S408, the buffer reading unit 160 performs priority change setting release processing, and as shown in FIG. 16D, the priority class corresponding to the first queuing buffer 141, the second queuing buffer 142, and the like. And the current priority F22 of the corresponding priority class is returned to the value of the initial priority F23 of each class. Further, the priority change priority flag F25 of the priority class corresponding to the first queuing buffer 141 is set to “0” (FIG. 13, step S503). As a result, as shown in FIG. 15C, the buffer reading unit 160 reads the frame again from the first queuing buffer 141 having the highest priority. At this time, the second queuing buffer 142 has been temporarily given priority to reading, and the congestion state has been resolved.

  As described above, according to the frame transfer apparatus 100 of this embodiment, the congestion state is detected because the priority class corresponding to the queuing buffer in which the congestion state is detected and the priority order immediately above the priority class are switched. In the queuing buffer, it is possible to suppress the occurrence of a problem in which frames exceeding the allowable amount of the queuing buffer are discarded by preferentially reading frames by the buffer reading unit 160. On the other hand, the priority class queuing buffer whose priority is lowered by one due to the priority change setting is in a state in which the amount of accumulated frames is likely to increase, and the accommodable area can be used effectively.

  FIG. 17 is a second explanatory diagram for illustrating the operation of the frame transfer apparatus. FIG. 18 is an explanatory diagram for explaining a buffer state management table during the operation of FIG. Here, the description will be made assuming that the contents of FIG. 4 are set in the buffer status management table 180.

  FIG. 17A shows a state in which the third queuing buffer 143 is in a congested state and the priority change setting is performed in the second queuing buffer 142 corresponding to the higher priority class. At this time, as shown in FIG. 18A, the priority classes corresponding to the second queuing buffer 142 and the priority class corresponding to the third queuing buffer 143 are switched, so that each queuing buffer 141 is switched. The priorities of the priority classes corresponding to ˜144 are 1, 3, 2, 4 in the order of the queuing buffers 141, 142, 143, 144, respectively.

  FIG. 17B shows a state where the fourth queuing buffer 144 is further congested from the state of FIG. In this case, the buffer writing unit 150 detects the congestion state of the fourth queuing buffer 144 (FIG. 7, step S104), and the priority corresponding to the fourth queuing buffer 144 as shown in FIG. 18B. The class congestion flag F24 is set to "1" (step S106). However, since the congestion flag F24 of the priority class corresponding to the third queuing buffer 143 immediately above is “1” (step S109: YES), the buffer writing unit 150 does not perform the priority change setting process. That is, the priority change of the priority class corresponding to the third queuing buffer 143 is not performed, and the priority order of the priority class corresponding to the third queuing buffer 143 and the priority class corresponding to the fourth queuing buffer 144 Do not replace. Therefore, the priorities of the priority classes corresponding to the queuing buffers 141 to 144 are 1, 3, 2, and 4 in the same order as in FIG.

  FIG. 17C shows a state in which the second queuing buffer 142 is further congested from the state of FIG. In this case, as shown in FIG. 18C, the buffer writing unit 150 sets the congestion flag F24 of the priority class corresponding to the second queuing buffer 142 to “1” (step S106), and then in step S107. The priority change setting release processing of the priority class corresponding to the second queuing buffer 142 is released by the priority change setting release processing. Further, when the first queuing buffer 141 is not in a congested state (step S109: NO), the buffer writing unit 150 sets “1” to the priority change setting of the priority class corresponding to the first queuing buffer 141. Set (step S111). As a result, since the priority order of the priority class corresponding to the first queuing buffer 141 and the priority class corresponding to the second queuing buffer 142 are switched, the priority order of the priority classes corresponding to the queuing buffers 141 to 144 is , Queuing buffers 141, 142, 143, 144 are 2, 1, 3, 4 in this order.

  FIG. 17D shows a state where the first queuing buffer 141 is further congested from the state of FIG. In this case, as shown in FIG. 18D, the buffer writing unit 150 sets the priority class congestion flag F24 corresponding to the first queuing buffer 141 to “1” (step S106), and then performs step S107. The priority change setting release processing of the priority class corresponding to the second queuing buffer 142 is released by the priority change setting release processing. As a result, the priorities of the priority classes corresponding to the queuing buffers 141 to 144 are 1, 2, 3, and 4 in the order of the queuing buffers 141, 142, 143, and 144, respectively.

  FIG. 19 is a third explanatory diagram for illustrating the operation of the frame transfer apparatus. FIG. 20 is an explanatory diagram for explaining a buffer state management table during the operation of FIG. FIG. 19 (a) shows the same state as FIG. 17 (b). FIG. 19B shows a state in which congestion of the third queuing buffer 143 has been eliminated from the state of FIG. In this case, the buffer reading unit 160 detects the release of the congestion state of the third queuing buffer 143 (step S404), and, as shown in FIG. 20A, the priority class corresponding to the third queuing buffer 143 Is set to "0" (step S405).

  By the priority change setting release processing in step S408, the buffer reading unit 160 releases the priority change setting of the priority class corresponding to the second queuing buffer 142 as shown in FIG. 20B (step S408). . On the other hand, as shown in FIG. 20C, the buffer writing unit 150 sets “1” to the priority change setting of the priority class corresponding to the third queuing buffer 143 (step S111). As a result, the priorities of the priority classes corresponding to the queuing buffers 141 to 144 are 1, 2, 4, and 3 in the order of the queuing buffers 141, 142, 143, and 144, respectively.

  As described above, according to the frame transfer apparatus 100 of the present embodiment, the priority of the priority class corresponding to the queuing buffer in which the congestion state is detected is not set to the highest priority, but the priority of the priority class immediately above the priority class. Basically, the frame is read according to the initial priority, and the priority is switched for some queuing buffers in which the congestion state occurs, thereby causing a problem such as discarding the frame. Can be suppressed. In addition, even when a congestion state is detected in a plurality of three or more queuing buffers, the priority of the priority class of the queuing buffer in which the congestion state has been raised and the original priority according to the frame type Frames can be read according to the priority order reflecting (initial priority). Therefore, for example, it is possible to suppress the occurrence of a problem in a congested queuing buffer while giving priority to reading of a frame for real-time communication. In addition, when the queuing buffer whose priority level has temporarily dropped due to priority switching becomes congested, the priority switching is preferentially suppressed in order to eliminate priority switching. However, the occurrence of discarding other frames can be suppressed.

  According to the frame transfer apparatus 100 of the present embodiment, the priority order is limited to the setting of the two real-time communication frames such as voice data and moving image data and the non-real-time communication frames such as character data and still image data. For example, among the frames for real-time communication, the priority order can be changed between audio data and moving image data. Thereby, the transmission quality of the frame transfer apparatus can be further improved.

B. Modification of the first embodiment:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

B1. Modification 1:
In the present embodiment, each of the queuing buffers 141 to 144 has been described as corresponding to one priority class. However, the plurality of queuing buffers provided in the frame transfer apparatus 100 include a plurality of queuing in one priority class. A configuration corresponding to the buffer may be used. In the present embodiment, the frame transfer apparatus 100 has been described as including four queuing buffers 141 to 144. However, the number is not limited to four as long as the number is two or more.

B2. Modification 2:
In this embodiment, the buffer writing unit 150 has been described as reading the application type from the frame and specifying the priority class to which the frame belongs. However, the buffer writing unit 150 is configured to transmit the source MAC address and the destination MAC address from the frame. , VLAN-ID, user priority, DSCP, source port number, destination port number, and a configuration that identifies a priority class based on information on a pair.

B3. Modification 3:
In this embodiment, the congestion state of the queuing buffer is described as being detected by the buffer writing unit 150. However, the setting monitoring terminal 500 detects the congestion state and sets “1” in the corresponding congestion flag F24. It may be a configuration. Further, the setting monitoring terminal 500 may detect the cancellation of the congestion state of the queuing buffer.

B4. Modification 4:
In this embodiment, the buffer reading unit 160 continues reading until the frame is no longer stored in the queuing buffer having a higher current priority. When the frame is not stored, the buffer reading unit 160 sequentially reads the queuing buffer having the lower current priority sequentially. Although described as performing priority control, it may be configured to perform weighted priority control in which the reading frequency is set higher as the current priority is higher and the reading is sequentially performed from all the queuing buffers. Alternatively, the higher the current priority, the longer the read time for one reading (the larger the amount of read data) may be, and all the queuing buffers may read the frame cyclically.

C. Second embodiment:
FIG. 21 is an explanatory diagram for explaining a schematic configuration of the frame transfer apparatus according to the second embodiment. The frame transfer apparatus 102 of the second embodiment is different from the frame transfer apparatus 100 (FIG. 2) of the first embodiment in that a buffer threshold management table 185 is added to the storage unit 190 of the frame transfer unit 110. . The frame transfer apparatus 102 according to the second embodiment sets the set values of the congestion threshold Th1 (FIG. 5) and the congestion elimination threshold Th2 (FIG. 6) preset in each of the queuing buffers 141 to 144, the frequency of the congestion state, and the like. It can be changed according to. The buffer threshold management table 185 is a table for managing the current setting values of the congestion threshold Th1 and the congestion elimination threshold Th2 of the queuing buffers 141 to 144, and indicates the congestion state of the queuing buffers 141 to 144. A flag, information for calculating a new set value after the change, and the like are registered. As will be described later, the buffer writing unit 150 and the buffer reading unit 160 of the second embodiment refer to the buffer threshold management table 185 and the congestion threshold Th1 and the congestion set in each of the queuing buffers 141 to 144, respectively. The set value of the cancellation threshold Th2 is changed.

  FIG. 22 is an explanatory diagram for explaining the contents of the buffer threshold value management table. The buffer threshold management table 185 includes a priority class F301, a threshold type F302, a change state flag F303, an initial setting value F304, a change direction F305, a maximum change width F306, a change stage number F307, and a congestion degree number F308. 11 fields of current set value F309, continuation flag F310, and continuation time F311 are provided. The entries E31 to E38 of the buffer threshold management table 185 correspond to the congestion threshold Th1 and the congestion elimination threshold Th2 of the queuing buffers 141 to 144, respectively. For example, the entry E36 corresponds to the congestion elimination threshold Th2 of the third queuing buffer 143. Hereinafter, the congestion threshold Th1 and the congestion elimination threshold Th2 are collectively referred to simply as “threshold Th”.

  The priority class F301 indicates the queuing buffers 141 to 144 to which the threshold value Th corresponding to the entry belongs. The threshold type F302 indicates whether the threshold Th corresponding to the entry is the congestion threshold Th1 or the congestion elimination threshold Th2. By the priority class F301 and the threshold type F302, one threshold Th corresponding to the entry (hereinafter also referred to as “corresponding threshold Th”) can be specified from the plurality of thresholds Th.

  The change state flag F303 indicates whether or not the corresponding threshold value Th has been changed from a setting initial value a described later (hereinafter also referred to as “change state”). Here, “1” is set when the corresponding threshold value Th is changed, and “0” is set when it is not changed.

  The initial setting value F304 indicates the initial setting value a (%) of the corresponding threshold value Th. The initial setting value a is an initial value of the corresponding threshold value Th, and is used as a setting value of the corresponding threshold value Th before the change state is entered. The initial setting value a can be set in advance via the setting monitoring terminal 500. Here, the initial setting value a is indicated by the accumulation amount ratio (%) with respect to the maximum data accumulation amount of each queuing buffer. For example, in the queuing buffer in which “60” is set as the initial setting value a of the congestion threshold Th1, the congestion state is detected when the data accumulation amount becomes 60% of the total.

  The change direction F305 indicates the change direction b of the correspondence threshold Th. The change direction b is a value indicating whether the corresponding threshold value Th in the changed state increases or decreases with respect to the initial set value a. Here, when the corresponding threshold value Th of the change state increases with respect to the initial setting value a, that is, when the corresponding threshold value Th moves in the frame accumulation amount increasing direction (left direction in FIG. 5) in the queuing buffer, “1 "It is shown. On the other hand, when the corresponding threshold value Th in the changed state decreases with respect to the initial set value a, that is, when the corresponding threshold value Th moves in the frame accumulation amount decreasing direction (right direction in FIG. 5) in the queuing buffer, “−1”. "It is shown. The change direction b can be set in advance via the setting monitoring terminal 500. Here, “1” is set in the entry corresponding to the congestion threshold Th1 of each queuing buffer, and “−1” is set in the entry corresponding to the congestion elimination threshold Th2.

  The maximum change width F306 indicates the maximum change width c (%) of the corresponding threshold value Th. The maximum change width c is a value used when calculating the corresponding threshold value Th in the changed state, and is the maximum value of the accumulation amount ratio (%) that is added to or subtracted from the initial set value a. For example, the corresponding threshold value Th that increases in the changed state is the initial set value a + the maximum change width c after the increase. On the other hand, for the corresponding threshold value Th that decreases in the changed state, the minimum value after the decrease is the initial set value a−the maximum change width c. The maximum change width c can be set in advance via the setting monitoring terminal 500.

  The change stage number F307 indicates the change stage number d of the corresponding threshold value Th. The change stage number d is the number of stages when the value changes stepwise from the initial setting value a to the maximum value or the minimum value (initial setting value a ± maximum change width c). Is shown. For example, the corresponding threshold value Th in which “3” is set in the change stage number d is initially set as the third stage value after passing through the initial stage value α, the first stage value α, and the second stage value β. A set value a ± maximum change width c is set (a <α <β <a + c or a> α> β> ac). The change stage number d can be set in advance via the setting monitoring terminal 500.

  The congestion degree F308 indicates the congestion degree X of the corresponding threshold Th. The congestion degree X is a degree indicating the ease of occurrence of the congestion state of the queuing buffer or the degree of difficulty of occurrence. As will be described later, when the congestion state occurs in the queuing buffer, or when the congestion state does not occur for a certain time (for example, one hour), the count is incremented by one. Here, the entry corresponding to the congestion threshold Th1 is used as a frequency indicating the difficulty of occurrence of the congestion state, and the entry corresponding to the congestion elimination threshold Th2 is used as the frequency indicating the ease of occurrence of the congestion state. The

The current setting value F309 indicates the current setting value Y (%) of the corresponding threshold value Th. The current set value Y is the current value of the corresponding threshold Th, and an initial set value a or a value Y calculated by the following equation (1) is set.
Y = a + b × c × X / d (1)
Here, a is an initial setting value, b is a change direction, c is a maximum change width, X is a congestion degree number, and d is a change stage number d. Further, 0 <a + | b × c | ≦ 100.

  The continuation flag F310 indicates whether or not the state where the queuing buffer is not congested (non-congested state) continues. “1” is set when the queuing buffer is in a non-congested state, and “0” is set when the queuing buffer is in a congested state.

  The duration F311 indicates the non-congested state duration Tc (second) of the corresponding threshold value Th. The non-congestion state duration Tc is a duration when the queuing buffer is in a non-congested state, and is counted up by 1 second when the queuing buffer is in a non-congested state. .

  FIG. 23 is a flowchart showing the flow of processing of the buffer writing unit 150 in the second embodiment. FIG. 23 corresponds to FIG. 7 of the first embodiment. The flowchart of FIG. 23 differs from the flowchart of FIG. 7 in that steps S120, S112, S140, and S150 are newly added. Steps S101 to S111 in FIG. 23 are the same as in FIG.

  After writing the frame (step S103), if the queuing buffer (target priority class) is not congested (step S104: NO), the buffer writing unit 150 performs a congestion threshold Th1 change determination process (step S120). ). The congestion threshold Th1 change determination process is a process for moving the congestion threshold Th1 set in the queuing buffer that has not been in a congestion state for a predetermined time or more in the frame accumulation amount increasing direction (left direction in FIG. 5). . Details of the congestion threshold Th1 change determination process will be described later with reference to FIG.

  On the other hand, when the queuing buffer (target priority class) becomes congested after writing the frame (step S103) (step S104: YES), the buffer writing unit 150 stores the buffer threshold management table 185 (FIG. 22). Referring to this, it is determined whether or not the change state flag F303 of the congestion threshold Th1 of the target priority class is “1” (step S112). When the change state flag F303 is “1” (step S112: YES), the buffer writing unit 150 performs a congestion threshold Th1 change release process for the target priority class (step S140). The congestion threshold Th1 change release process is a process for releasing the changed state by setting the change state flag F303 to “0” in the queuing buffer in which the congestion threshold Th1 is in the changed state. Here, it is performed on the congestion threshold Th1 of the target priority class. As a result, the congestion threshold Th1 of the queuing buffer (target priority class) that has become congested is returned to the initial state. Details of the congestion threshold Th1 change release processing for the target priority class will be described later with reference to FIG.

  After executing the congestion threshold Th1 change release process in step S140 or when the change state flag F303 is “0” in step S112 (step S112: NO), the buffer writing unit 150 eliminates the congestion for the target priority class. A threshold Th2 change determination process is performed (step S150). The congestion elimination threshold Th2 change determination process is a process for moving the congestion elimination threshold Th2 set in the queuing buffer that has been in a congested state for a predetermined time or more in the frame accumulation amount decreasing direction (right direction in FIG. 5). It is. Here, it is performed on the congestion elimination threshold Th2 of the target priority class. As a result, the congestion elimination threshold Th2 of the queuing buffer (target priority class) that has become congested is changed. Details of the congestion elimination threshold Th2 change determination process will be described later with reference to FIG. After the congestion release threshold Th2 change determination process (step S150), the process of the buffer writing unit 150 returns to step S101. The above is the processing flow of the buffer writing unit 150 of the second embodiment.

  FIG. 24 is a flowchart showing the flow of the congestion threshold Th1 change determination process in step S120 of FIG. 25 and 26 are explanatory diagrams for explaining a buffer threshold value management table during the congestion threshold value Th1 change determination process in step S120. In the following, as an example of the congestion threshold Th1 change determination process, when the queuing buffer of the target priority class is not congested for a predetermined time (here, the set time Tp), the congestion threshold Th1 of the target priority class is changed in an increasing direction. The processing to be performed will be described. The set time Tp (for example, 3600 seconds) can be arbitrarily set in advance via the setting monitoring terminal 500.

  First, the buffer writing unit 150 determines whether or not the continuation flag F310 of the congestion threshold Th1 of the target priority class is “1” (step S121). Here, the second queuing buffer 142 in FIG. 25 will be described as the target priority class. In FIG. 25A, the continuation flag F310 of the congestion threshold Th1 (entry E33) of the target priority class (second queuing buffer 142) is “0”.

  When the continuation flag F310 is “0” (step S121: NO), the buffer writing unit 150 sets the continuation flag F310 of the congestion threshold Th1 of the target priority class to “1” as illustrated in FIG. 25B. (Step S122). Subsequently, the buffer writing unit 150 starts counting up the non-congested state duration Tc (second) indicated by the duration F311 of the congestion threshold Th1 of the target priority class (step S123). After step S123, the buffer writing unit 150 ends the process.

  On the other hand, when the continuation flag F310 of the congestion threshold Th1 of the target priority class (second queuing buffer 142) is “1” as shown in FIG. 25 (c) in step S121 (step S121: YES). The buffer writing unit 150 determines whether or not the non-congestion state duration Tc (second) indicated by the duration F311 of the congestion threshold Th1 of the target priority class is equal to or longer than the set time Tp (here, 3600 seconds). (Step S124). That is, in this step S124, it is determined whether or not one hour or more has elapsed in a state where the congestion flag F24 (FIG. 4) of the target priority class is set to “0”. In FIG. 25C, the non-congestion state duration Tc of the congestion threshold Th1 of the target priority class is “3600”, which is equal to or longer than the set time Tp (here, Tc = Tp). That is, the target priority class (second queuing buffer 142) shown in FIG. 25C is in a state where exactly one hour has passed with the congestion flag F24 (FIG. 4) kept at “0”.

  When the non-congestion state duration Tc is equal to or longer than the set time Tp (here, Tc ≧ 3600) (step S124: YES), the buffer writing unit 150, as shown in FIG. The congestion degree number X of Th1 is incremented by “+1” (step S125). On the other hand, unlike FIG. 26C, when the non-congestion state duration Tc is smaller than the set time Tp (step S124: NO), the buffer writing unit 150 ends the process. This is because the non-congested state of the queuing buffer does not continue for a predetermined amount or more, and it is not necessary to change the congestion threshold Th1 in the increasing direction.

  After counting up the congestion frequency number X in step S125, the buffer writing unit 150 updates the current setting value Y of the congestion threshold Th1 of the target priority class (step S126). Specifically, the buffer writing unit 150 updates the current setting value Y set in the current setting value F309 using the value calculated by the above-described equation (1). In FIG. 26D, the initial setting value a of the congestion threshold Th1 of the target priority class is “50”, the change direction b is “1”, the maximum change width c is “20”, the change stage number d is “10”, The congestion degree X is “1”. Therefore, the value calculated by equation (1) is “52” (52 = 50 + 1 × 20 × 1/10). Accordingly, as shown in FIG. 26E, “52” is set as the new current setting value Y in the current setting value F309. By updating the current setting value Y from “50” to “52”, the congestion threshold Th1 of the target priority class is changed in the increasing direction.

  Subsequently, the buffer writing unit 150 determines whether or not the change state flag F303 of the congestion threshold Th1 of the target priority class is “1” (step S127). In FIG. 26E, the change state flag F303 of the congestion threshold Th1 of the target priority class is “0”. When the change state flag F303 is “0” (step S127: NO), the buffer writing unit 150 sets the change state flag F303 of the congestion threshold Th1 of the target priority class to “1” as illustrated in FIG. Set (step S128). Thereafter, the buffer writing unit 150 ends the process. On the other hand, when the change state flag F303 is “1” (step S127: YES), the buffer writing unit 150 ends the process as it is. The above is the flow of the congestion threshold Th1 change determination process.

  According to the above-described congestion threshold Th1 change determination process, when the congestion flag F24 (FIG. 4) of the target priority class becomes “0” for a predetermined time or more, the congestion threshold Th1 can be changed in the increasing direction. If “0” of the congestion flag F24 continues, the congestion threshold Th1 of the target priority class can be sequentially changed in the increasing direction by repeating the congestion threshold Th1 change determination process. That is, the increase amount of the congestion threshold Th1 can be changed according to the duration of “0” of the congestion flag F24.

  FIG. 27 is a flowchart showing the flow of the congestion threshold Th1 change release process in step S140 of FIG. FIG. 28 and FIG. 29 are explanatory diagrams for explaining the buffer threshold value management table during the congestion threshold value Th1 change release processing in step S140. Here, the second queuing buffer 142 in FIG. 28 will be described as the target priority class. In FIG. 28A, the current setting value Y of the congestion threshold Th1 (entry E33) of the target priority class (second queuing buffer 142) is “52”.

  First, as shown in FIG. 28B, the buffer writing unit 150 sets the initial setting value a to the current setting value Y of the congestion threshold Th1 of the target priority class (step S141). Thereafter, as shown in FIG. 28C, the buffer writing unit 150 sets the congestion degree X of the congestion threshold Th1 of the target priority class to “0” (step S142). Further, as shown in FIG. 29D, the buffer writing unit 150 sets the change state flag of the congestion threshold Th1 of the target priority class to “0” (step S143). Further, as illustrated in FIG. 29E, the buffer writing unit 150 sets the continuation flag of the congestion threshold Th1 of the target priority class to “0” (step S144). The buffer writing unit 150 stops counting up the Tc of the congestion threshold Th1 of the target priority class (Step S145). Further, as shown in FIG. 29F, the buffer writing unit 150 sets Tc of the congestion threshold Th1 of the target priority class to “0” (step S146). Thereafter, the buffer writing unit 150 ends the process. The above is the flow of the congestion threshold Th1 change release process.

  FIG. 30 is a flowchart showing the flow of the congestion elimination threshold Th2 change determination process in step S150 of FIG. FIG. 31 and FIG. 32 are explanatory diagrams for explaining the buffer threshold management table at the time of the congestion elimination threshold Th2 change determination process in step S150. In the following, as an example of the congestion elimination threshold Th2 change determination process, the congestion elimination threshold Th2 of the target priority class that has become congested is changed in a decreasing direction, and the congestion elimination threshold Th2 of the priority class lower than the object priority class is initially set. Processing for returning to the state will be described. Here, the second queuing buffer 142 in FIG. 31 will be described as the target priority class.

  The buffer writing unit 150 determines whether or not the congestion degree number X of the congestion elimination threshold Th2 of the target priority class is smaller than the change stage number d (step S151). The congestion degree number X of the congestion elimination threshold Th2 (entry E34) of the target priority class in FIG. 31A is “0”, and the change stage number d is “10”. Therefore, the congestion degree number X is smaller than the change stage number d.

  When the congestion degree number X is smaller than the change stage number d (step S151: YES), the buffer writing unit 150 sets the congestion degree number X of the congestion elimination threshold Th2 of the target priority class to “+1” as shown in FIG. Count up (step S152). On the other hand, unlike FIG. 31, when the congestion degree number X of the congestion elimination threshold Th2 of the target priority class is the change stage number d or more (step S151: NO), the buffer writing unit 150 ends the process.

  After incrementing the congestion frequency number X by “+1” in step S152, the buffer writing unit 150 determines whether or not a higher priority class exists (step S153). In FIG. 31, since the second queuing buffer 142 is the target priority class, a higher priority class (first queuing buffer 141) exists.

  If a higher priority class exists (step S153: YES), it is determined whether or not “1” exists in the change state flag F303 of the congestion elimination threshold Th2 in the higher priority class (step S154). On the other hand, unlike FIG. 31, when there is no higher priority class than the target priority class (step S153: NO), the buffer writing unit 150 skips step S154. In FIG. 31, “1” does not exist in the change state flag F303 of the congestion elimination threshold Th2 of the higher priority class (first queuing buffer 141).

  In the upper priority class, when “1” does not exist in the change state flag F303 of the congestion elimination threshold Th2 (step S154: NO), the buffer writing unit 150 sets the current setting value of the congestion elimination threshold Th2 in the lower priority class. It is determined whether Y is equal to the initial set value a (step S155). On the other hand, unlike FIG. 31, when “1” is present in the change state flag F303 of the congestion elimination threshold Th2 in the higher priority class (step S154: YES), the buffer writing unit 150 ends the processing. In FIG. 31, in the lower priority class (third queuing buffer 143), the current setting value Y (Y = 48) of each congestion elimination threshold Th2 (entry E36) is different from the initial setting value a (a = 50). Yes.

  In the lower priority class, when the current setting value Y of the congestion elimination threshold Th2 is different from the initial setting value a (step S155: NO), the buffer writing unit 150 performs the congestion elimination threshold Th2 change release process for the lower priority class. (Step S160). The congestion cancellation threshold Th2 change release process is a process for releasing the changed state by setting the change state flag F303 to “0” in the queuing buffer in which the congestion release threshold Th2 is in the changed state. Here, since the congestion elimination threshold Th2 change release processing is performed for the lower priority class, as shown in FIG. 31C, the congestion elimination threshold Th2 (third queuing buffer 143) of the lower priority class (third queuing buffer 143). In the entry E36), the change state flag F303 is set to “0”, and the initial set value “a” is set to “50” as the current set value Y. Details of the congestion cancellation threshold Th2 change release processing for the lower priority class will be described later with reference to FIG. On the other hand, unlike FIG. 31, in all lower priority classes, when the current setting value Y of the congestion elimination threshold Th2 is equal to the initial setting value a (step S155: YES), the buffer writing unit 150 skips step S160. To do.

  Next, the buffer writing unit 150 updates the current setting value Y of the congestion elimination threshold Th2 of the target priority class (step S157). Specifically, the buffer writing unit 150 updates the current setting value Y set in the current setting value F309 using the value calculated by the above-described equation (1). In FIG. 31C, the initial setting value a of the congestion elimination threshold Th2 of the target priority class is “50”, the change direction b is “−1”, the maximum change width c is “20”, and the change stage number d is “10”. "The congestion degree X is" 1 ". Therefore, the value calculated by equation (1) is “48” (48 = 50 + 1 × 20 × (−1) / 10). Therefore, as shown in FIG. 32D, “48” is set as the new current setting value Y in the current setting value F309. By updating the current setting value Y from “50” to “48”, the congestion elimination threshold Th2 of the target priority class is changed in a decreasing direction. Next, the buffer writing unit 150 determines whether or not the change state flag F303 of the congestion elimination threshold Th2 of the target priority class is “1” (step S158). In FIG. 32D, the change state flag F303 of the congestion elimination threshold Th2 of the target priority class is “0”.

  When the change state flag F303 is “0” (step S158: NO), the buffer writing unit 150 sets the change state flag F303 of the congestion elimination threshold Th2 of the target priority class to “1” as illustrated in FIG. (Step S159). Thereafter, the buffer writing unit 150 ends the process. On the other hand, unlike FIG. 32, when the change state flag F303 of the congestion elimination threshold Th2 of the target priority class is “1” (step S158: YES), the buffer writing unit 150 ends the process as it is. The above is the flow of the congestion elimination threshold Th2 change determination process.

  FIG. 33 is a flowchart showing the flow of the congestion cancellation threshold Th2 change release process for the lower priority class in step S160 of FIG. FIG. 34 is an explanatory diagram for explaining a buffer threshold management table used in the congestion cancellation threshold Th2 change release process in step S160. The buffer writing unit 150 sets the current priority and the initial priority to be equal in each priority class lower than the target priority class by the congestion cancellation threshold Th2 change release process for the lower priority class. An example of the congestion cancellation threshold Th2 change release process for the lower priority class is shown below. Here, the buffer writing unit 150 will be described as including a priority class registration unit capable of setting and registering any one of the priority classes, as in the first embodiment.

  The buffer writing unit 150 first registers the target priority class in the priority class registration unit (step S161). Here, the second queuing buffer 142 in FIG. 34 will be described as a target priority class. The buffer writing unit 150 refers to the buffer state management table 180 and determines whether or not a priority class lower than the registration priority class exists (step S162). In FIG. 34A, since the second queuing buffer 142 is the target priority class, lower priority classes (third and fourth queuing buffers 143 and 144) exist.

  If a lower priority class exists (step S162: YES), the buffer writing unit 150 registers the immediately lower priority class in the priority class registration unit (step S163). In FIG. 34A, the third queuing buffer 143 is registered. On the other hand, unlike FIG. 34, when there is no lower priority class (step S162: NO), the buffer writing unit 150 ends the process.

  In step S163, after registering the immediate priority class in the priority class registration unit, the buffer writing unit 150 determines whether or not the current setting value Y of the congestion elimination threshold Th2 of the registration priority class is equal to the initial setting value a ( Step S164). In FIG. 34 (a), the current setting value Y (Y = 48) and the initial setting value a (a = 50) a are set in the congestion elimination threshold Th2 (entry E36) of the registration priority class (third queuing buffer 143). Not equal.

  When the current setting value Y of the congestion elimination threshold Th2 of the registration priority class is not equal to the initial setting value a (step S164: NO), the buffer writing unit 150, as shown in FIG. The initial setting value a is set to the current setting value Y of the cancellation threshold Th2 (step S165). Further, as shown in FIG. 34C, the buffer writing unit 150 sets a change state flag F303 of the congestion priority threshold Th2 of the registration priority class to “0” (step S166). Thereafter, the processing of the buffer writing unit 150 returns to step S162. On the other hand, when the current set value Y of the congestion priority threshold Th2 of the registration priority class is equal to the initial set value a in step S164 (step S164: YES), the processing of the buffer writing unit 150 returns to step S162. The above is the flow of the congestion cancellation threshold Th2 change release process for the lower priority class.

  FIG. 35 is a flowchart showing a process flow of the buffer read unit 160 in the second embodiment. FIG. 35 corresponds to FIG. 12 of the first embodiment. The flowchart of FIG. 35 differs from the flowchart of FIG. 12 in that steps S410 and S420 are newly added. Steps S401 to S408 in FIG. 35 are the same as those in FIG.

  When the congestion state of the queuing buffer (target priority class) is canceled by reading the frame (step S402) (step S404), the buffer reading unit 160 sets the change state flag F303 of the congestion cancellation threshold Th2 of the target priority class to “1”. It is determined whether or not (step S410). When the change state flag F303 of the congestion elimination threshold Th2 of the target priority class is “1” (step S410: YES), a congestion elimination threshold Th2 change cancellation process for the target priority class is performed (step S420). Details of the congestion cancellation threshold Th2 change release processing for the target priority class will be described later with reference to FIG. After the congestion cancellation threshold Th2 change release process for the target priority class, the buffer read unit 160 performs the process of step S406. In step S410, when the change state flag F303 of the congestion elimination threshold Th2 of the target priority class is “0” (step S410: NO), the buffer reading unit 160 skips step S420 and performs the process of step S406. The above is the processing flow of the buffer reading unit 160 in the second embodiment.

  FIG. 36 is a flowchart showing the flow of the congestion cancellation threshold Th2 change release process for the target priority class in step S420 of FIG. FIG. 37 is an explanatory diagram for explaining a buffer threshold value management table at the time of releasing the congestion elimination threshold value Th2 in step S420. The buffer reading unit 160 sets the current priority and the initial priority of the target priority class to be equal to each other by the congestion cancellation threshold Th2 change release process for the target priority class. An example of the congestion cancellation threshold Th2 change release process for the target priority class is shown below. Here, the second queuing buffer 142 in FIG. 37 will be described as the target priority class.

As shown in FIG. 37A, the buffer writing unit 150 sets the initial setting value a to the current setting value Y of the congestion elimination threshold Th2 of the target priority class (step S421). Thereafter, the buffer writing unit 150 sets the congestion degree number X of the congestion elimination threshold Th2 of the registration priority class to “0” as illustrated in FIG. 37B (step S422). Further, as shown in FIG. 37C, the buffer writing unit 150 sets a change state flag F303 of the congestion priority threshold Th2 of the registration priority class to “0” (step S423). The above is the flow of the congestion cancellation threshold Th2 change release process for the target priority class.

  FIG. 38 is a first explanatory diagram for illustrating the operation of the frame transfer apparatus according to the second embodiment. Here, description will be made assuming that the contents of FIG. 4 are set in the buffer status management table 180. FIG. 38A shows a state where all the queuing buffers 141 to 144 are not congested. At this time, the priority order of each priority class is 1, 2, 3, 4 in the order of the queuing buffers 141, 142, 143, 144. FIG. 38B shows a state in which the third queuing buffer 143 is congested due to the writing of frames to the third queuing buffer 143 from the state of FIG. When the third queuing buffer 143 becomes congested, the priority change setting is performed in the second queuing buffer 142 corresponding to the higher priority class. As a result, the priority order of each priority class is 1, 3, 2, 4 in the order of the queuing buffers 141, 142, 143, 144. Further, the congestion elimination threshold Th2 of the third queuing buffer 143 moves in the frame accumulation amount decreasing direction (right direction in FIG. 38).

  FIG. 39 is an explanatory diagram for explaining a buffer threshold value management table during the operation of FIG. FIG. 39A shows a buffer threshold management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. The currently set values Y of the congestion elimination threshold Th2 of the queuing buffers 141 to 144 are all “50”. FIG. 39B shows the buffer threshold value management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. When the third queuing buffer 143 becomes congested, the buffer writing unit 150 counts up the congestion degree X of the congestion elimination threshold Th2 (entry E36) of the target priority class (third queuing buffer 143) by “+1” ( FIG. 30, step S152). Further, the buffer writing unit 150 updates the current setting value Y of the congestion elimination threshold Th2 (entry E36) of the target priority class to “48” (48 = 50 + 1 × 20 × (−1) / 10) (step S157). Then, the change state flag F303 is set to “1” (step S159).

  FIG. 40 is a second explanatory diagram for illustrating the operation of the frame transfer apparatus according to the second embodiment. FIG. 40A shows the same state as FIG. 38B described above. That is, a state is shown in which the third queuing buffer 143 is in a congested state and the priority change setting is performed in the second queuing buffer 142 corresponding to the higher priority class.

  FIG. 40 (b) shows a state where the fourth queuing buffer 144 is further congested from the state of FIG. 40 (a). At this time, the priority order of each priority class does not change, and the congestion elimination threshold Th2 of the fourth queuing buffer 144 does not move. FIG. 40 (c) shows a state where the second queuing buffer 142 is further congested from the state of FIG. 40 (a). At this time, the priority order of each priority class is 2, 1, 3, 4 in the order of the queuing buffers 141, 142, 143, and 144, respectively. Further, the congestion elimination threshold Th2 of the second queuing buffer 142 moves in the frame accumulation amount decreasing direction (right direction in FIG. 40). On the other hand, the congestion elimination threshold Th2 of the third queuing buffer 143 moves in the frame accumulation amount increasing direction (left direction in FIG. 40) and returns to the position before the congestion. FIG. 40 (d) shows a state where the first queuing buffer 141 is further congested from the state of FIG. 40 (a). At this time, the priority order of each priority class is 1, 2, 3, 4 in the order of the queuing buffers 141, 142, 143, 144. Further, the congestion elimination threshold Th2 of the first queuing buffer 141 moves in the frame accumulation amount decreasing direction (right direction in FIG. 40). On the other hand, the congestion elimination threshold Th2 of the third queuing buffer 143 moves in the frame accumulation amount increasing direction (left direction in FIG. 40) and returns to the position before the congestion.

  FIG. 41 is an explanatory diagram for explaining a buffer threshold value management table in the operation of FIG. FIG. 41A shows the buffer threshold value management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. When the fourth queuing buffer 144 becomes congested when the third queuing buffer 143 is congested, the buffer writing unit 150 causes the congestion elimination threshold Th2 of the target priority class (fourth queuing buffer 144) (entry E38). Is incremented by “+1” (FIG. 30, step S152). On the other hand, the buffer writing unit 150 does not change the current setting value Y of the congestion elimination threshold Th2 (entry E38) of the target priority class to “50” and does not change the change state flag F303 to “0” ( Step S154: YES).

  FIG. 41 (b) shows the buffer threshold management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. 40 (c). When the second queuing buffer 142 becomes congested when the third queuing buffer 143 is congested, the buffer writing unit 150 causes the congestion elimination threshold Th2 (entry E34) of the target priority class (second queuing buffer 142). Is incremented by “+1” (FIG. 30, step S152). Further, the buffer writing unit 150 updates the current setting value Y of the congestion elimination threshold Th2 (entry E34) of the target priority class to “48” (48 = 50 + 1 × 20 × (−1) / 10 = 48) (step In step S157, the change state flag F303 is set to “1” (step S159). Further, the buffer writing unit 150 sets “50”, which is the initial setting value a, to the current setting value Y of the congestion elimination threshold Th2 (entry E36) of the priority class (third queuing buffer 143) lower than the target priority class. Then (FIG. 33, step S165), the change state flag F303 is set to “0” (step S166).

  FIG. 41 (c) shows the buffer threshold management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. 40 (d). If the first queuing buffer 141 becomes congested when the third queuing buffer 143 is congested, the buffer writing unit 150 causes the congestion elimination threshold Th2 (entry E32) of the target priority class (first queuing buffer 141). Is incremented by “+1” (FIG. 30, step S152). In addition, the buffer writing unit 150 updates the current setting value Y of the congestion elimination threshold Th2 (entry E32) of the target priority class to “48” (48 = 50 + 1 × 20 × (−1) / 10 = 48) (step In step S157, the change state flag F303 is set to “1” (step S159). Further, the buffer writing unit 150 sets “50”, which is the initial setting value a, to the current setting value Y of the congestion elimination threshold Th2 (entry E36) of the priority class (third queuing buffer 143) lower than the target priority class. Then (FIG. 33, step S165), the change state flag F303 is set to “0” (step S166).

  FIG. 42 is a third explanatory diagram for illustrating the operation of the frame transfer apparatus according to the second embodiment. FIG. 42A shows the same state as FIG. 40B described above. That is, the third queuing buffer 143 and the fourth queuing buffer 144 are congested. At this time, the priority order of each priority class is 1, 3, 2, 4 in the order of the queuing buffers 141, 142, 143, and 144, respectively. FIG. 42B shows a state in which the congestion of the third queuing buffer 143 has been eliminated from the state of FIG. By eliminating the congestion, the priority change setting of the higher priority class (second queuing buffer 142) is canceled. As a result, the priorities of the priority classes are 1, 2, 4, 3 in the order of the queuing buffers 141, 142, 143, and 144, respectively. Further, the congestion elimination threshold Th2 of the fourth queuing buffer 144 moves in the frame accumulation amount decreasing direction (right direction in FIG. 42). On the other hand, the congestion elimination threshold Th2 of the third queuing buffer 143 moves in the frame accumulation amount increasing direction (left direction in FIG. 42) and returns to the position before the congestion.

  FIG. 43 is an explanatory diagram for explaining a buffer threshold management table during the operation of FIG. FIG. 43A shows the buffer threshold value management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. The current setting value Y of the congestion elimination threshold Th2 of the queuing buffers 141 to 144 is “48” only for the third queuing buffer 143 and “50” for the others. FIG. 43B shows the buffer threshold management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. When the buffer reading unit 160 detects the cancellation of the congestion state of the target priority class (third queuing buffer 143), the buffer reading unit 160 sets the initial setting value a to the current setting value Y of the congestion cancellation threshold Th2 (entry E36) of the target priority class. (FIG. 36, step S421). Further, the buffer reading unit 160 sets the congestion degree number X and the congestion state flag of the congestion elimination threshold Th2 (entry E36) of the target priority class to “0” (steps S422 and S423). On the other hand, when the buffer writing unit 150 detects the congestion state of the lower priority class (fourth queuing buffer 144), it increments the congestion degree number X of the congestion elimination threshold Th2 (entry E38) of the lower priority class by “+1”. To do. (FIG. 30, step S152). In addition, the buffer writing unit 150 updates the current setting value Y of the congestion elimination threshold Th2 (entry E34) of the target priority class to “46” (48 = 50 + 2 × 20 × (−1) / 10 = 46) (step S40). In step S157, the change state flag F303 is set to “1” (step S159).

  FIG. 44 is a fourth explanatory diagram for illustrating the operation of the frame transfer apparatus according to the second embodiment. FIG. 44A shows a state in which all the queuing buffers 141 to 144 are not congested. FIG. 44B shows a state where a predetermined time (set time Tp) has passed from the state of FIG. 44A in the third queuing buffer 143 without congestion. In the third queuing buffer 143, when congestion has not occurred for a predetermined time, the congestion threshold Th1 of the third queuing buffer 143 moves in the frame accumulation amount increasing direction (left direction in FIG. 44).

  FIG. 45 is an explanatory diagram for explaining a buffer threshold value management table during the operation of FIG. FIG. 45A shows the buffer threshold value management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. The currently set values Y of the congestion threshold Th1 of the queuing buffers 141 to 144 are all “50”. FIG. 45 (b) shows the buffer threshold management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. 44 (b). When the buffer writing unit 150 detects that the third queuing buffer 143 is not congested for a set time Tp (for example, 3600 seconds) (FIG. 24, step S124), the target priority class (third queuing buffer 143) ) Of the congestion threshold Th1 (entry E35) is incremented by “+1” (step S125). Further, the buffer writing unit 150 updates the current setting value Y of the congestion threshold Th1 of the target priority class to “52” (52 = 50 + 1 × 20 × 1/10) (step S126), and sets the change state flag F303 to “1”. "(Step S128).

  FIG. 46 is a fifth explanatory diagram for illustrating the operation of the frame transfer apparatus according to the second embodiment. FIG. 46A shows the same state as FIG. 44B described above. That is, the state where the third queuing buffer 143 is not congested for the set time Tp and the congestion threshold Th1 is moved in the direction of increasing the frame accumulation amount is shown. FIG. 46B shows a state in which the second queuing buffer 142 has not been congested for the set time Tp beyond the state of FIG. 46A. At this time, the congestion threshold Th1 of the second queuing buffer 142 moves in the frame accumulation amount increasing direction (left direction in FIG. 46). On the other hand, the congestion threshold Th1 of the third queuing buffer 143 does not change in the state where it has moved. FIG. 40C shows a state in which the fourth queuing buffer 144 has not been congested for the set time Tp from the state of FIG. 46A. At this time, the congestion threshold Th1 of the fourth queuing buffer 144 moves in the frame accumulation amount increasing direction (left direction in FIG. 46). On the other hand, the congestion threshold Th1 of the third queuing buffer 143 does not change in the state where it has moved.

  FIG. 47 is an explanatory diagram for explaining a buffer threshold value management table during the operation of FIG. FIG. 47A shows the buffer threshold management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. When the buffer writing unit 150 detects that the second queuing buffer 142 is not congested for the set time Tp or more (FIG. 24, step S124), the congestion threshold Th1 of the target priority class (second queuing buffer 142) is detected. The congestion degree number X of (entry E33) is incremented by “+1” (step S125). Further, the buffer writing unit 150 updates the current setting value Y of the congestion threshold Th1 of the target priority class to “52” (52 = 50 + 1 × 20 × 1/10) (step S126), and sets the change state flag F303 to “1”. "(Step S128). FIG. 47B shows the buffer threshold management table 185 when the queuing buffers 141 to 144 are in the state shown in FIG. When the buffer writing unit 150 detects that the fourth queuing buffer 144 is not congested for the set time Tp or more (FIG. 24, step S124), the congestion threshold Th1 of the target priority class (fourth queuing buffer 144). The congestion degree number X of (entry E37) is incremented by “+1” (step S125). Further, the buffer writing unit 150 updates the current setting value Y of the congestion threshold Th1 of the target priority class to “52” (52 = 50 + 1 × 20 × 1/10) (step S126), and sets the change state flag F303 to “1”. "(Step S128).

  According to the frame transfer apparatus 102 of the second embodiment described above, as in the first embodiment, the priority of the priority class of the queuing buffer in which the congestion state occurs is raised, and the original according to the frame type is increased. Frames can be read out according to the priority order reflecting the priority order (initial priority). In addition to this, when the queuing buffer (target priority class) becomes congested, the priority level of the target priority class is increased in order to change the congestion elimination threshold Th2 of the target priority class in the direction of decreasing the frame accumulation amount. Can be maintained longer than in the first embodiment. Thereby, generation | occurrence | production of frame discard can be suppressed.

  Further, when the congestion state of the queuing buffer (target priority class) does not occur for a predetermined time, the congestion threshold Th1 of the queuing buffer of the target priority class is changed in the direction of increasing the frame accumulation amount. The situation is less likely to occur. As a result, the higher priority class can be made less susceptible to the priority change when a congestion state occurs in the target priority class, and the occurrence of defects such as frame discard can be suppressed.

D. Modification of the second embodiment:
D1. Modification 1:
In this embodiment, the configuration is described in which the congestion threshold Th1 and the congestion elimination threshold Th2 of each queuing buffer are managed by one table (buffer threshold management table 185). However, the congestion threshold Th1 and the congestion elimination threshold Th2 are different from each other. It is good also as a structure managed by a table.

D2. Modification 2:
In the present embodiment, the buffer writing unit 150 and the buffer reading unit 160 have been described as a configuration in which the setting values of the congestion threshold Th1 and the congestion elimination threshold Th2 are changed with reference to the buffer threshold management table 185. It is good also as a structure which the arithmetic processing part (not shown) mounted in 102 performs.

D3. Modification 3:
The modification described in the first embodiment (modification of the first embodiment) can naturally be applied to the frame transfer apparatus 102 of the present embodiment.

DESCRIPTION OF SYMBOLS 10 ... Network system 100 ... Frame transfer apparatus 110 ... Frame transfer part 131, 132, 133 ... Line interface part 140 ... Queuing buffer group 141 ... 1st queuing buffer 142 ... 2nd queuing buffer 143 ... 3rd queuing buffer 144 ... 4th queuing buffer 150 ... buffer writing unit 160 ... buffer reading unit 170 ... priority class table 180 ... buffer state management table 190 ... storage unit 200 ... user terminal 300 ... server 400 ... storage 500 ... setting monitoring terminal

Claims (10)

A frame transfer device,
Three or more queuing buffers capable of storing frames;
A storage unit for storing relative priorities for reading frames from each of the queuing buffers;
A buffer read unit that reads and transfers frames from the queuing buffer according to the priority order; and
A buffer writing unit that writes a frame received from the outside of the frame transfer device to any one of the plurality of queuing buffers according to information included in the frame, and
When the buffer writing unit detects a congestion state of any of the first queuing buffers, the buffer writing unit has a higher priority than the first queuing buffer and the first queuing buffer when a predetermined condition is satisfied. Is a frame transfer apparatus for switching the priority order of the second queuing buffer that is one level higher. The frame transfer apparatus according to claim 1,
The frame transfer device, in which the buffer writing unit determines that the predetermined condition is not satisfied when the second queuing buffer is in a congested state, and does not change the priority order. In the frame transfer device according to claim 1 or 2,
The buffer writing unit, when the priority of the first queuing buffer is lowered by one due to the change of the priority performed in the past,
(I) Eliminate the change of priority, and
(Ii) A frame transfer apparatus that switches priority between the first queuing buffer and the second queuing buffer when the second queuing buffer is not congested. The frame transfer device according to any one of claims 1 to 3,
When the buffer reading unit detects that the congestion of the first queuing buffer whose priority is increased by one due to the switching of the priorities performed in the past, the buffer reading unit cancels the switching of the priorities. Frame transfer device. The frame transfer device according to any one of claims 1 to 4,
The storage unit stores information indicating the current priority of each queuing buffer and information indicating the initial priority of each queuing buffer;
In the information indicating the current priority level, the buffer writing unit indicates the priority level of the second queuing buffer that is one priority higher than the first queuing buffer in the initial priority level. Rewriting the information indicating the current priority so that the priority is one lower than the first queuing buffer;
The buffer reading unit is a frame transfer device that reads and transfers a frame from the queuing buffer according to the current priority order. A frame transfer method,
A step of reading frames from three or more queuing buffers according to the priority order stored in the storage unit and transferring them;
Writing a frame to any of the plurality of queuing buffers according to information contained in the frame;
When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer having a higher priority than the first queuing buffer when a predetermined condition is satisfied. And a step of exchanging the priorities of the two queuing buffers. A frame transfer device,
Three or more queuing buffers capable of storing frames;
A storage unit for storing relative priorities for reading frames from each of the queuing buffers;
A buffer read unit that reads and transfers frames from the queuing buffer according to the priority order; and
A buffer writing unit that writes a frame received from the outside of the frame transfer device to any one of the plurality of queuing buffers according to information included in the frame, and
The storage unit stores a congestion threshold and a congestion elimination threshold set in each of the queuing buffers,
The buffer writing unit
(I) The congestion state of the queuing buffer is detected when the accumulated amount of frames exceeds the congestion threshold, and the congestion state of the queuing buffer is resolved when the accumulated amount of frames falls below the congestion elimination threshold. Detect
(Ii) When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer have one priority when a predetermined condition is satisfied. Change the priority of the upper second queuing buffer,
(Iii) A frame transfer apparatus that reduces the congestion elimination threshold set in the first queuing buffer. A frame transfer device,
Three or more queuing buffers capable of storing frames;
A storage unit for storing relative priorities for reading frames from each of the queuing buffers;
A buffer read unit that reads and transfers frames from the queuing buffer according to the priority order; and
A buffer writing unit that writes a frame received from the outside of the frame transfer device to any one of the plurality of queuing buffers according to information included in the frame, and
The storage unit stores a congestion threshold and a congestion elimination threshold set in each of the queuing buffers,
The buffer writing unit
(I) The congestion state of the queuing buffer is detected when the accumulated amount of frames exceeds the congestion threshold, and the congestion state of the queuing buffer is resolved when the accumulated amount of frames falls below the congestion elimination threshold. Detect
(Ii) When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer have one priority when a predetermined condition is satisfied. Change the priority of the upper second queuing buffer,
(Iii) A frame transfer apparatus that increases the congestion threshold set in the queuing buffer when a queuing buffer that is not congested for a predetermined time or more is detected. A frame transfer method,
A step of reading frames from three or more queuing buffers according to the priority order stored in the storage unit and transferring them;
Writing a frame to any of the plurality of queuing buffers according to information contained in the frame;
Detecting the congestion state of the queuing buffer when the accumulated amount of frames exceeds the congestion threshold, and detecting the cancellation of the congestion state of the queuing buffer when the accumulated amount of frames falls below the congestion elimination threshold;
When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer having a higher priority than the first queuing buffer when a predetermined condition is satisfied. And a step of switching the priority order of the two queuing buffers to reduce a congestion elimination threshold set in the first queuing buffer. A frame transfer method,
A step of reading frames from three or more queuing buffers according to the priority order stored in the storage unit and transferring them;
Writing a frame to any of the plurality of queuing buffers according to information contained in the frame;
Detecting the congestion state of the queuing buffer when the accumulated amount of frames exceeds the congestion threshold, and detecting the cancellation of the congestion state of the queuing buffer when the accumulated amount of frames falls below the congestion elimination threshold;
When the congestion state of any of the first queuing buffers is detected, the first queuing buffer and the first queuing buffer having a higher priority than the first queuing buffer when a predetermined condition is satisfied. A step of changing the priority of the queuing buffers of 2;
And a step of increasing a congestion threshold set in the queuing buffer when a queuing buffer that has not been congested for a predetermined time is detected.

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