JP2006135762A - Device and method for packet transmission control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform packet discard processing when a congestion condition occurs while maintaining fairness between users, for a packet transmission control device and a packet transmission control method with a common buffer. <P>SOLUTION: The device is provided with a write-in controller 21 which performs packet writing in the common buffer 20 corresponding to the user; a reading control unit 22 which performs packet reading corresponding to the user; a common buffer idle address FIFO 24 which stores an address from which a packet is read out as an idle address, and transfers the idle address to the write-in controller one by one; a storage amount table 25 which adds packet length information of input packets corresponding to the user, and subtracts packet length information of the packet corresponding to the user read out from the common buffer after a predetermined time; and a controller 26 which controls packet discard corresponding to the user whose storage amount is the maximum in the storage amount table when a congestion condition of the common buffer occurs; and discriminates packet discard including the transmission packet amount from the present time to the past of the predetermined time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a packet transmission control apparatus and a packet transmission control method provided with a common buffer for processing packets from a plurality of users.

  A packet transmission control apparatus that controls transmission of packets from a plurality of users to respective destinations via a network and performs packet priority control mainly includes a configuration including a common buffer and a configuration including an individual buffer. Can be separated. The configuration including the former common buffer has an advantage that the total buffer capacity can be reduced as compared with the configuration including the latter individual buffer. A system for packetizing and transmitting various types of high-speed and large-capacity data has been put into practical use. For example, devices such as layer 2 switches are required to perform bandwidth control and priority control at high speed, In general, the individual buffers are configured by SRAM (Static Random Access Memory) corresponding to the transmission speed of the packet, and this SRAM is compared to DRAM (Dynamic Random Access Memory) or the like. Expensive.

  FIG. 5 is an explanatory diagram of a conventional common buffer control configuration, in which 50 is a common buffer, 51 is a multiplexing unit, 52 is a demultiplexing unit, 53 is a control unit, and shows the main part of the packet transmission control device. It is. Packets input from a plurality of incoming routes are time-division multiplexed by the multiplexing unit 51 and input to the common buffer 50. At this time, the control unit 53 is notified of the packet destination address, user information, class information, and the like. The control unit 53 manages the free address of the common buffer 50, designates the write address of the packet from the multiplexing unit 51, determines whether it is a high priority class or a low priority class based on the class information, and performs high priority. The class packet is controlled to be read preferentially, the separation unit 52 is controlled in accordance with the destination address of the packet, and is sent to the outgoing route corresponding to the destination address.

  FIG. 6 is an explanatory diagram of the control configuration of the individual buffer of the conventional example, 60-1 to 60-n are individual buffers, 61 is a selection switch unit, 62 is a read control unit, and inputs from a plurality of entry paths. The read packets are respectively written in the individual buffers 60-1 to 60-n corresponding to the incoming routes, and the packets read out by the priority control according to the packet class information by the read control unit 62 are selected switch units. The selection switch unit 61 sends the information to the outgoing route corresponding to the information from the read control unit 62 or the destination address of the packet.

  As shown in FIG. 7, the priority control in the packet transmission control device having the common buffer of the conventional example is performed by an application identification selection unit 71 such as a high priority class packet such as a voice packet or data. The low priority class packet is identified, the high priority class packet is written in the high priority class buffer area 73, the low priority class packet is written in the low priority class buffer area 74, and the read selection unit 72 Packets are read out from the high priority class buffer area 73 in the FIFO format with complete priority to the low priority class buffer area 74, and read out from the low priority class buffer area 74 in the FIFO format or between the users. (Round robin method)

  FIG. 8 shows the management of free addresses in the common buffer of the conventional example. The configurations of the multiplexing unit 51 and the separation unit 52 in FIG. 5 are omitted, and the common buffer 80 and the write control are shown. A configuration including a unit 81, a read control unit 82, and a common buffer empty address FIFO 83 is shown. The write control unit 81 issues a free address request to the common buffer free address FIFO 83, and writes the input packet to the free address of the common buffer 80 in accordance with the free address notification to the common buffer free address FIFO 83. The write address of the buffer 80, the packet class information, and the outgoing route notification corresponding to the destination address are transferred.

  The read control unit 82 performs read address management in accordance with the class information, and can also perform management for each user. For example, the buffer address management of the high priority class shown in FIG. 9A and the buffer address management of the low priority class shown in FIG. Each write address from the control unit 81 is managed in the FIFO format, and when a high priority class packet is written in the common buffer 80, the address is written in the FIFO in FIG. 9A. Therefore, priority is given to the low priority class, and reading from the common buffer is performed according to the address of the packet of the high priority class. When there is no higher priority class address, packets are read from the common buffer using the lower priority class address. FIG. 9C shows a case where address management is performed individually for each user. An address management FIFO is provided for each of users 1 to N, and between users, the common buffer 80 is read by a read address according to sequential reading. Packet reading is performed. Then, the read control unit 82 transfers the address of the common buffer 80 from which the packet has been read to the common buffer empty address FIFO 83 so as to indicate the empty address return.

  Also, since the storage capacity of the common buffer is finite, if a large amount of packets arrives and there is no free space in the common buffer, the next arrived packet is discarded. As shown in FIG. 7, when this common buffer is composed of a high-priority class area 73 and a low-priority class area 74, the high-priority class packet is preferentially read from the common buffer and transmitted. Therefore, the low priority class packet remains in the common buffer. Therefore, in the congestion state, the low priority class packet is discarded. In packet transmission control, it is desired to provide a service to a plurality of users fairly, and fairness is also required for packet discard when the packet congestion occurs.

  Therefore, a means for managing the packet accumulation amount for the common buffer corresponding to the user and discarding the arrival packet from the user when the packet accumulation amount of a certain user exceeds a threshold value is known. In this case, the packet accumulation amount is subtracted according to the size of the packet read from the common buffer and transmitted, and is added according to the packet size written in the common buffer. May be less than the chance of discarding a packet for a user transmitting a small packet.

In order to improve such points, a packet identification unit that inputs an incoming packet, an information management unit, a determination unit, a control unit, and a FIFO buffer are included. Based on the size of the arrived packet, the flow identifier, the size of the packet read from the control unit, and the flow identifier, it is managed as a virtual queue size and a flow identifier list, using the variable TB, constant C, threshold TH, etc. Controls whether or not to discard a packet input to the FIFO buffer, and controls the order of reading packets from the FIFO buffer and controls packet discard so that the bandwidth allocation corresponding to the flow identifier is fair. A means for performing the above has been proposed (see, for example, Patent Document 1).
JP 2003-324474 A

  In a packet transmission apparatus provided with a common buffer, when a packet exceeding the amount of packets read out from the common buffer and sent out, the common buffer becomes congested, and the arrived packet is discarded. It is desired to perform disposal fairly for a plurality of users. In the conventional example in which the amount of user-corresponding accumulated data is compared when the common buffer is in a congested state, the packets of users with a large accumulated amount are discarded. Thus, since a user who performs packet transmission of the high priority class reads packets preferentially from the common buffer, the accumulation amount of the common buffer always increases for the user who performs packet transmission of the low priority class. Therefore, there is a problem that the probability that the packet of the low priority class user is discarded increases.

  In the conventional example of managing the common buffer (FIFO buffer) as the virtual queue size, the priority of the packet is not considered, and in the congested state, it corresponds to the previous user (active flow). The amount of packet transmission is not taken into consideration. From the viewpoint of fairness, when user A who uses only the low priority class on average and user B who uses (a large amount of high priority class) + (a small amount of low priority class), when congestion occurs. In this case, it is desirable to discard the packet of the user B who has transmitted a large amount of packets. However, since the discard process is performed based on the accumulated amount of the common buffer at the time of occurrence of the congestion state, the packet of the user A is It was discarded and there was a problem with fairness.

  An object of the present invention is to process packet discard when a common buffer congestion state occurs so that fairness can be maintained regardless of the priority class.

  The packet transmission control device of the present invention is a packet transmission control device having a common buffer for temporarily storing packets from a plurality of users. Read control unit that reads user-compatible packets from the common buffer, common buffer free address FIFO that accumulates addresses from which packets are read from the common buffer as free addresses, and sequentially transfers free addresses to the write control unit, The packet length information of the user-corresponding packet written in the buffer is added, the packet length information of the user-corresponding packet read from the common buffer is subtracted after a predetermined time, and when the congestion state of the common buffer occurs, Control discarding of packets corresponding to the user with the maximum storage amount in the storage amount table And a control unit.

  Further, time information is added to the user information and packet length information of the packets read from the common buffer by the read control unit and sequentially stored, and after a predetermined time based on the time information, the user information and the packet length information are read, The accumulation amount table is provided with a virtual FIFO that is input as a subtraction value of the accumulation amount corresponding to the user.

  The packet transmission control method of the present invention is a packet transmission control method in which packets from a plurality of users are temporarily stored in a common buffer for transmission control. Based on the packet length information, the accumulated amount of user-written packets written in the common buffer is obtained, and the user information and packet length information read from the common buffer are subtracted from the accumulated amount of packets after a predetermined time. This includes a process of identifying the user with the maximum storage amount based on the storage amount thus obtained and discarding the user's packet when the common buffer is congested.

  In a packet transmission control apparatus and a packet transmission control method for performing packet transmission of a plurality of users using a common buffer, when a common buffer congestion state occurs, not only the accumulated amount of the common buffer corresponding to the user at that time but also the past Users who transmit a large amount of packets of high priority class by discarding the packets of users with the maximum accumulation amount by comparing the accumulated amount including the amount read and sent from the common buffer to the user In addition, the packet discarding process can be performed while maintaining fairness with the user who transmits the low priority class packet.

  The packet transmission control device of the present invention will be described with reference to FIG. 2. A write control unit 21 that writes a packet to a common buffer 20 in correspondence with a user, and a read that reads out a packet corresponding to a user from the common buffer 20. The control unit 22, the address read from the packet from the common buffer 20 is accumulated as a free address, and the common buffer free address FIFO 24 for sequentially transferring the free address to the write control unit, and the user-corresponding packet written in the common buffer 20 The accumulated amount table 25 for subtracting the packet length information of the user-corresponding packet read from the common buffer after a predetermined time, and the accumulated amount in the accumulated amount table 25 when the congestion state of the common buffer 20 occurs. And a control unit 26 that controls the discard of the maximum user-compatible packet.

  The packet transmission control method of the present invention writes a packet to the common buffer 20 and obtains the stored amount of the packet corresponding to the user written to the common buffer 20 based on the user information and the packet length information of the packet. The user with the maximum accumulation amount is identified based on the accumulation amount obtained by subtracting the packet user information and the packet length information read from the common buffer 20 from the packet accumulation amount after a predetermined time. This includes a process of discarding the packet when the common buffer 20 is congested.

  FIG. 1 is an explanatory view of the main part of an embodiment of the present invention, in which 11 is a high priority class area, 12 is a low priority class area, 13 is an application identification selection section, 14 is a read selection section, and 15 is a user-specific selection. , 16 is a virtual FIFO, and 17 is a control unit. The high priority class and low priority class areas 11 and 12 are areas formed in the common buffer, and the application identification selection unit 13 identifies the priority class of the packet. A packet of low priority class such as normal data or the like is written to the area 12.

  Further, the read selection unit 14 preferentially reads and transmits the packet stored in the high priority class area 11 with respect to the packet stored in the low priority class area 12. Further, the accumulated amount table 15 for each user adds the accumulated amount in the common buffer corresponding to the user based on the user information and the packet length information of the packet written in the common buffer, and the user of the packet read from the common buffer. Information and packet length information are used to determine the amount of data stored in the common buffer for the user. The packet length information of the packet read from the common buffer is delayed by a predetermined time by way of the virtual FIFO 16. Is subtracted from the accumulated amount. Accordingly, the accumulation amount table 16 stores, for each user, a value indicating the accumulation amount corresponding to (accumulation amount at a certain time) + (data amount transmitted within a predetermined time in the past from a certain time). The

  In this case, the control unit 17 adds the time information to the user information and the packet length information of the packet read from the common buffer and writes the information to the virtual FIFO 16, and the user information that has passed a predetermined time based on the time information The packet length information is read from the virtual FIFO 16 and controlled to be input as subtraction data to the accumulation amount table 15 for each user. As described above, the accumulation amount table 15 has a predetermined time for each user. The accumulated amount indicating the data amount of the input packet remains. Then, the control unit 17 discards the user packet indicating the maximum accumulation amount in the accumulation amount table 15 when the congestion state of the common buffer occurs. That is, the user's packet having a large data amount of transmission packets within a predetermined past time is discarded at the time when the packet is read from the common buffer. Therefore, the packet of a user with a small amount of data is less likely to be discarded even if it is a low priority packet, and fairness among users can be maintained in the packet transmission process by priority control. In addition, the accuracy of fairness can be adjusted by selecting the storage time of the virtual FIFO 16 and the delay time for inputting as a subtraction value corresponding to the user in the accumulated amount table 15 for each user.

  FIG. 2 is an explanatory diagram of an embodiment of the present invention, in which 20 is a common buffer, 21 is a write control unit, 22 is a read control unit, 23 is a virtual FIFO + management unit, 24 is a common buffer free address FIFO, and 25 is An accumulation amount table, 26 is a control unit, and 27 is an accumulation amount comparison table. As shown in FIG. 1, the common buffer 20 includes a high priority class area 11 and a low priority class area 12. The write control unit 21 includes the function of the application identification selection unit 13 in FIG. 1, and the read control unit 22 includes the function of the read selection unit 14 in FIG. The virtual FIFO + management unit 23 includes the function of the virtual FIFO 16 in FIG. The accumulation amount table 25 corresponds to the accumulation amount table 15 for each user in FIG. The common buffer empty address FIFO 24, the control unit 26, and the comparison table 27 correspond to the function of the control unit 17 in FIG.

  When the common buffer 20 is not congested, the write control unit 21 extracts user information, class information, packet length information, and the like of the input packet, and sets the common buffer 20 free address requested to the common buffer free address FIFO 24 On the other hand, the input packet is written, the user information, the class information, and the write address are notified to the read control unit 22, and the user information and the packet length information are transferred to the accumulation amount table 25. The accumulation amount table 25 adds packet length information for each user.

  The read control unit 22 reads and sends a packet preferentially from the high priority class area of the common buffer 20. Then, the user information and the packet length information of the read packet are transferred to the virtual FIFO + management unit 23, and the current time information is added and temporarily held. The time information in this case can be added by the clock function in the virtual FIFO + management unit 23 or the clock function of the control unit 26. The address at which the packet is read from the common buffer 20 is transferred to the common buffer empty address FIFO 24. Then, the virtual FIFO + management unit 23 manages the elapsed time, and transfers user information and packet length information after a predetermined time has elapsed to the accumulation amount table 25. The accumulation amount table 25 subtracts the packet length information from the virtual FIFO + management unit 23 from the addition result of the packet length information by the packet input corresponding to the user.

  As shown in FIG. 3, the accumulation amount table 25 has an area for holding the packet accumulation amounts corresponding to the users # 1 to #N, and the time when the packet is read out from the common buffer 20 by the read control unit 22 and sent out. It becomes the added packet length information including the packet length information of the input packet before a predetermined time. This packet length information can be the number of bytes. The contents of the accumulated amount table 25 include packet length information of packets input in the past for a predetermined time, not the accumulated amount at the current time of the common buffer 20.

  For example, the control unit 26 monitors the common buffer free address FIFO 24, and when there is no free address or when the free address becomes a number equal to or less than a preset threshold, the occurrence of a congestion state of the common buffer 20 is detected. Judgment is made, and the user with the maximum storage amount in the storage amount table 25 is searched. In this case, a high-speed search can be executed by using the comparison table 27 that compares the accumulated amount corresponding to the user in the accumulated amount table 25 by rounding. This comparison table 27 has the configuration shown in FIG. 4, for example, and compares the areas corresponding to the users # 1 to #N based on the accumulated amount corresponding to the user rounded, for example, every 1500 bytes. In that case, an area for the maximum accumulation amount display bit is provided. In the case shown in the figure, “1” is an area indicating the accumulation amount, and “0” indicates an empty area, so that the user with the maximum accumulation amount is identified by one search indicated by a dotted arrow with respect to the leading “1”. can do. By using the comparison table 27, the control unit 26 can search for a user with the maximum accumulation amount at a high speed when a congestion state occurs.

  In this case, due to the occurrence of the congestion state of the common buffer 20, the user who has the largest (current common buffer storage amount) + (transmission amount in the past predetermined time) is identified, and the packet of this user is discarded. It is possible to detect a user who maximizes the amount of used packets over a predetermined period of time in addition to the current time, discard the user's packet, and maintain fairness among the users. In the packet discarding process, for example, the controller 26 instructs the reading controller 22 to discard the packet including user information for discarding the packet. The read control unit 22 reads and discards the packet corresponding to the user information from the common buffer 20 according to the instruction. As a result, empty address information is transferred to the common buffer empty address FIFO 24, so that a newly input packet can be written into the common buffer 20. If the packet corresponding to the user with the maximum storage amount is lost in the common buffer 20 due to the discarding process and the congestion state continues, the write control unit 21 is notified and the packet of the user with the maximum storage amount is input. Can be disposed of at the time. Alternatively, by instructing the writing control unit 21 from the control unit 26 to discard the packet including the maximum accumulated amount of user information, the writing control unit 21 causes the user of the packet input in accordance with the instructed user information. Discard packets that match the information.

(Supplementary note 1) In a packet transmission control apparatus having a common buffer for temporarily storing packets from a plurality of users, a write control unit for writing packets to the common buffer in correspondence with the user, and the common buffer A read control unit for reading a user-compatible packet;
A common buffer empty address FIFO for accumulating addresses read from the common buffer as empty addresses and sequentially transferring empty addresses to the write control unit, and packet length information of user-corresponding packets written in the common buffer And an accumulation amount table that subtracts the packet length information of the user-ready packet read from the common buffer after a predetermined time, and the user correspondence with the maximum accumulation amount in the accumulation amount table when the congestion state of the common buffer occurs. A packet transmission control apparatus comprising: a control unit that controls discarding of the packet.

(Supplementary note 2) Time information is added to the user information and packet length information of the packets read from the common buffer by the read control unit and sequentially stored, and the user information and the packet length after a predetermined time based on the time information. 2. The packet transmission control device according to claim 1, further comprising a virtual FIFO that reads out information and inputs the information as a subtraction value of a storage amount corresponding to a user in the storage amount table.
(Additional remark 3) The accumulation amount of the said accumulation amount table is rounded up for every fixed amount corresponding to a user, and the comparison table which searches the user of the largest accumulation amount by the largest accumulation amount display bit is provided, It is characterized by the above-mentioned. The packet transmission apparatus according to appendix 1.

  (Supplementary note 4) In a packet transmission control method for temporarily storing packets from a plurality of users in a common buffer and controlling transmission, the packet is written in the common buffer, and user information and packet length information of the packet are written. Based on the above, the accumulated amount of the packet corresponding to the user written in the common buffer is obtained, and the user information and the packet length information of the packet read from the common buffer are subtracted from the accumulated amount of the packet after a predetermined time. A packet transmission control method comprising: identifying a user with the maximum storage amount based on the stored amount and discarding the user's packet when the common buffer is congested.

  (Supplementary Note 5) The packet length information of the user-corresponding packet written in the common buffer is input to the accumulation table and added, and the packet length information of the user-corresponding packet read from the common buffer is accumulated after a predetermined time has elapsed. The method includes a step of inputting to a quantity table and subtracting from the addition result to obtain an accumulated amount corresponding to a user, and discarding a packet of a maximum accumulated amount of a user when a congestion state of the common buffer occurs. The packet transmission control method according to appendix 4.

It is principal part explanatory drawing of the Example of this invention. It is explanatory drawing of the Example of this invention. It is explanatory drawing of the accumulation | storage amount table of the Example of this invention. It is explanatory drawing of the storage amount comparison table of the Example of this invention. It is explanatory drawing of the control structure of the common buffer of a prior art example. It is explanatory drawing of the control structure of the separate buffer of a prior art example. It is explanatory drawing of the priority control structure of the common buffer of a prior art example. It is explanatory drawing of the free address management of a prior art example. It is explanatory drawing of the read address management of a prior art example.

Explanation of symbols

11 High priority class area 12 Low priority class area 13 Application identification selection unit 14 Read selection unit 15 Accumulated amount table for each user 16 Virtual FIFO
17 control unit 20 common buffer 21 write control unit 22 read control unit 23 virtual FIFO + management unit 24 common buffer free address FIFO
25 Accumulated amount table 26 Control unit 27 Comparison table

Claims (3)

In a packet transmission control device having a common buffer for temporarily storing packets from a plurality of users,
A write controller that writes packets to the common buffer in response to a user;
A read control unit for reading a user-compatible packet from the common buffer;
A common buffer empty address FIFO for accumulating addresses read from the common buffer as empty addresses and sequentially transferring empty addresses to the write control unit;
An accumulation amount table for adding packet length information of a user-corresponding packet written in the common buffer and subtracting packet length information of a user-corresponding packet read from the common buffer after a predetermined time;
A packet transmission control device comprising: a control unit that controls discard of a user-corresponding packet having a maximum accumulation amount in the accumulation amount table when a congestion state of the common buffer occurs.   Time information is added to the user information and packet length information of the packets read from the common buffer by the read control unit and sequentially stored, and the user information and packet length information are read after a predetermined time based on the time information. 2. The packet transmission control apparatus according to claim 1, further comprising a virtual FIFO that is input to the accumulation amount table as a subtraction value of the accumulation amount corresponding to a user. In a packet transmission control method for temporarily storing packets from a plurality of users in a common buffer and controlling transmission,
User information of the packet read from the common buffer by writing a packet to the common buffer, obtaining an accumulation amount of the user-corresponding packet written to the common buffer based on user information and packet length information of the packet And the packet length information are subtracted from the accumulated amount of the packet after a predetermined time, and the user with the maximum accumulated amount is identified, and the user's packet is discarded when the congestion state of the common buffer occurs. A packet transmission control method comprising a process of processing.

Images