JP2012244348A - Network relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve a problem that, at multicast transfer in a network relay device, when congestion occurs in a packet transmission part, a packet including the transmission part where congestion occurs at a destination is blocked at a packet reception part, which may cause delay influence on the other packets.SOLUTION: An input part has a disposal threshold rewriting circuit to rewrite a disposal threshold of a packet including an output part where congestion occurs at a destination so as to be small based on congestion information received from a crossbar switch that performs packet switching. When the disposal threshold is small, the corresponding packet is easily disposed, and delay influence on the other packets can be reduced.

Description

  The present invention relates to a network relay device, and more particularly to a network relay device that performs data transfer by controlling congestion.

  In recent information communication networks, the amount of communication of information has increased rapidly. Therefore, high-speed and large-capacity data processing is also required in network relay devices. In particular, in multicast transfer in which information from one point is transferred to a plurality of points, data input from one line is duplicated and output to a plurality of lines inside the network relay device. For this reason, it is necessary to process a large amount of data further increased by replication with high efficiency.

  Patent Document 1 discloses a packet switch that can reduce the processing load without reducing the input rate allowed for a multicast packet.

JP 2002-208938 A

  The present invention relates to a packet transfer apparatus including a plurality of transmission / reception units, and performs switching of packet transfer for transferring a packet received by one reception unit to one or a plurality of transmission units according to the congestion status of the transmission unit. This is a technique for performing transfer control of the receiver, and is particularly effective for multicast transfer.

  In the packet transfer apparatus of FIG. 3, when a packet transferred from a certain packet transfer unit 50 is switched from a sub crossbar switch (SSW) 60 to another SSW 60 via a crossbar switch (CSW) 70, one SSW 60 When packets are concentrated on the network, congestion occurs that delays packet transfer beyond the communication capacity of the SSW 60. In particular, the multicast transfer in which the CSW 70 copies one packet to a plurality of SSWs 60 and transfers the packet is likely to be congested.

  With reference to FIG. 1, a conventional method for dealing with congestion will be described. In FIG. 1, a packet transfer apparatus 900 includes a packet transfer receiving unit 50 (I), a sub crossbar switch receiving unit 60 (I), a crossbar switch 70, a sub crossbar switch transmitting unit 60 (E), The packet transfer transmission unit 50 (E). Note that there are n packet transfer receivers 50 (I), sub crossbar switch receivers 60 (I), sub crossbar switch transmitters 60 (E), and packet transfer transmitters 50 (E). It is. When distinguishing each, it describes as packet transfer receiving part 50 (In) (n = 0-n-1).

  SSW receiver 60 (I) includes a multicast SSW transmission queue 90 and a scheduler 130. The CSW 70 includes a switching unit 200, a CSW transmission queue 110, a congestion monitoring circuit 120, a congestion information rewriting circuit 140, and a congestion information generating circuit 100. Here, there are n CSW transmission queues 110, congestion monitoring circuits 120, and congestion information rewriting circuits 140, respectively. The SSW transmission unit 60 (E) includes a header analysis circuit 150.

  In switching in the packet transfer apparatus 900, a packet addressed to the SSW transmission unit 60 (E) where congestion occurs is waited at the SSW reception unit 60 (I) and waits until the congestion is eliminated. In FIG. 1, the congestion monitoring circuit 120 in the CSW 70 that performs switching notifies the congestion information generation circuit 100 of congestion information when it is found that congestion has occurred in the CSW transmission queue 110 in charge. That the CSW transmission queue 110 is congested means that one of the SSW transmission units 60 (E) is congested. For this reason, the congestion information generation circuit 100 generates congestion information indicating the SSW transmission unit 60 (E) in which congestion has occurred, and sends the congestion information to the congestion information rewriting circuit 140 that exists for each SSW transmission unit 60 (E).

  The congestion information rewriting circuit 140 updates the field for writing the congestion information of the switch header to be transmitted to the SSW transmission unit 60 (E). When there is no packet to be transmitted for a certain period of time, the congestion information rewriting circuit 140 generates a dummy packet, writes the congestion information in the header, and transmits it to the SSW transmission unit 60 (E). The header analysis circuit 150 (E) of the SSW transmission unit 60 (E) reads the congestion information from the switch header and transmits it to the SSW reception unit 60 (I).

  The SSW receiver 60 (I) has an SSW transmission queue 90 for temporarily writing a packet to be transferred to the CSW 70, and is managed by the scheduler 130. When the scheduler 130 receives the congestion information, if a packet including the SSW transmission unit 60 (E) where the congestion has occurred reaches the head of the SSW transmission queue 90, the scheduler 130 performs scheduling so that the packet is not transmitted to the CSW 70. And wait for congestion to be resolved. However, this method has a problem as shown in FIG.

  Assume that congestion occurs in the SSW transmission unit 60 (E1) as shown in FIG. The SSW receiver 60 (I0) waits for the packet “1” because the destination of the first packet “1” in the SSW transmission queue 90 is the SSW transmitter 60 (E0) and the SSW transmitter 60 (E1). Then, all the packets held in the SSW transmission queue 90 are in a standby state. For this reason, a delay also occurs for the packet “2” whose destinations are the SSW transmission unit 60 (E2) and the SSW transmission unit 60 (E3). That is, in the conventional method, there is a problem that a delay occurs even for a packet destined only for the SSW transmission unit in which congestion does not occur.

  This problem can be solved by dividing the transmission queue of the SSW receiving unit 60 (I) for each destination. However, since there are a plurality of destinations in multicast transfer, it is not possible to separate queues for each destination. For this reason, multicast packets generally use one queue 90 regardless of the destination.

  In the multicast transfer in the packet transfer device, if congestion occurs in the SSW transmission unit, the SSW reception unit stops the packet including the transmission unit that is congested at the destination, which affects the delay of other packet transfers. End up.

  In the present invention, the packet is easily discarded by lowering the discard threshold of the packet including the SSW output port that is congested in the multicast transfer. As a result, multicast packets only for destinations that are not congested are easily transferred. The discard threshold refers to the switch header added in the packet transfer unit. When the queue length of the transmission queue is smaller than the discard threshold in the SSW reception unit, the packet is transmitted to the buffer, and when the queue length of the transmission queue is larger than the discard threshold. Is the value to discard the packet. The queue length is the number of staying packets in the queue. In other words, reducing the discard threshold means that the probability of being discarded without being transmitted to the queue is increased.

  The problems described above include a plurality of packet transfer units that perform packet transfer, a crossbar switch unit that performs packet switching, and a plurality of switches that transmit and receive packets to and from the packet transfer unit and control input / output of the crossbar switch. In the network relay apparatus, the crossbar switch transmits the detected congestion information to the switch, and the switch that has received the congestion information can be achieved by the network relay apparatus that rewrites the discard threshold of the switch header.

  Also, a network relay having a plurality of packet transfer units that perform packet transfer, a crossbar switch unit that performs packet switching, and a plurality of switches that transmit / receive packets to / from the packet transfer unit and control input / output of the crossbar switch In the device, the crossbar switch writes the detected congestion information in the switch header and transmits it to the switch, and the switch that has received the congestion information can be achieved by a network relay device that rewrites the discard threshold of the switch header.

  In multicast forwarding, the discard threshold for packets including output ports that are congested is lowered to facilitate discarding of packets. Thereby, it is possible to reduce the influence of the delay of the packet not including the port where the congestion occurs.

It is a block diagram of the conventional packet transfer apparatus. It is a block diagram of the packet transfer apparatus main part explaining congestion. It is a block diagram of a network relay apparatus. It is a detailed block diagram of a network relay device. It is a block diagram of a congestion monitoring circuit. It is a figure explaining serial transfer of congestion information. It is a figure explaining the header format of a packet. It is a block diagram of a discard threshold value rewriting circuit and a discard determination circuit. It is a figure explaining the flow of packet discard. It is a flowchart explaining the process of SSW. It is a flowchart explaining the process of a network relay apparatus. It is a detailed block diagram of another network relay apparatus. It is a detailed block diagram of still another network relay device. It is a figure explaining the other header format of a packet. It is a flowchart explaining the process of another network relay apparatus. It is a block diagram of another network relay apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings using examples. The same reference numerals are assigned to substantially the same parts, and the description will not be repeated.

  The configuration of the network relay device will be described with reference to FIG. In FIG. 3, the network relay device 100 includes an n-type line 20, n packet transfer units 30, a switching unit 40, and a CPU 10. The packet transfer unit 30 includes a packet transfer unit 50 and an SSW 60. The switching unit 40 includes a CSW 70.

  The packet transfer unit 50 adds and deletes a switch header to the packet received from the line 20. The SSW 60 discards the packet with reference to the discard threshold. The switch header includes switching information and a discard threshold. The CSW 70 performs switching based on the switching information in the switch header of the packet. The CPU 10 monitors and controls all the packet transfer units 30 and the switching units 40. The CPU 10 is connected to the packet transfer unit 30 and the switching unit 40 via the CPU bus 170. The SSW 60 and the CSW 70 are connected via a data path 180 and a congestion notification dedicated line 190.

  Details of the network relay device will be described with reference to FIG. In FIG. 4, the network relay device 1000 includes a packet transfer receiving unit 50 (I), an SSW receiving unit 60A (I), a CSW 70, an SSW transmitting unit 60 (E), and a packet transfer transmitting unit 50 (E). It is composed of The packet transfer receiving unit 50 (I), the SSW receiving unit 60A (I), the SSW transmitting unit 60 (E), and the packet transfer transmitting unit 50 (E) are each composed of n units. The packet transfer receiver 50 (I) and the packet transfer transmitter 50 (E) together correspond to the packet transfer unit 50. The SSW receiver 60A (I) and the SSW transmitter 60 (E) together correspond to the SSW 60. The SSW receiving unit 60A (I) includes a discard threshold rewriting circuit 80, a discard determination circuit 160, and a multicast SSW transmission queue 90. The CSW 70 includes a switching unit 200, a CSW transmission queue 110, a congestion monitoring circuit 120, and a congestion information generation circuit 100. Each of the CSW transmission queue 110 and the congestion monitoring circuit 120 is composed of n units.

  The packet transfer receiving unit 50 (I) adds a switch header generated from the packet analysis result and the device state to the packet. The discard threshold rewriting circuit 80 rewrites the discard threshold field of the switch header. The SSW transmission queue 90 temporarily stores packets to be transmitted to the CSW 70. The discard determination circuit 160 compares the discard threshold field of the switch header with the queue length of the SSW transmission queue 90 and determines whether to send the packet to the SSW transmission queue 90 or to discard it. The switching unit 200 refers to the switching information in the switch header, determines the output destination, and switches the packet. The CSW transmission queue 110 temporarily stores packets to be transmitted to the SSW transmission unit. The congestion monitoring circuit 120 monitors the CSW transmission queue. The congestion information generation circuit 100 generates congestion information based on the information sent from the congestion monitoring circuit 120. The SSW transmission unit 60 (E) analyzes the switch header of the packet and determines whether to transmit to the packet transfer unit. The packet transfer receiving unit 50 (E) deletes the switch header of the packet. Further, a congestion notification dedicated line 190 is provided between the SSW receiving unit 60 (I) and the CSW 70 in order to notify the congestion information.

  Congestion detection will be described with reference to FIG. In FIG. 5, the congestion monitoring device 120 of the CSW 70 includes a queue length register 121, a congestion reference value register 122, and a magnitude comparator 123. The queue length register 121 manages the queue length. The congestion reference value register 122 manages a reference value for determining that congestion has occurred.

  The congestion monitoring device 120 monitors the queue length of the CSW transmission queue 110 and stores it in the queue length register 121. The queue length register 121 and the congestion reference value register 122 are compared. When the queue length register 121 is larger, the SSW transmission unit 60 (E) as the transfer destination determines that congestion has occurred, and a plurality of congestions corresponding to each CSW transmission queue Congestion information is notified to the information generation circuit 100.

  The congestion information generation circuit 100 generates congestion information based on the information of the congestion monitoring circuit 120, and transfers the congestion information to the discard threshold rewriting circuit 80 of all the SSW receiving units 60 (I) through the congestion notification dedicated line 190. The congestion information is expressed by a bitmap representing the congested SSW transmission unit 60 (E).

  The serial signal transfer of the congestion information bitmap will be described with reference to FIG. In FIG. 6, the congestion information generation circuit 100 has a bitmap table that stores the congestion information of each transmission queue 110. The congestion information generation circuit 100 sequentially selects the table information by the multiplexer 101 and transfers it to the discard threshold rewriting circuit 80. The discard threshold rewriting circuit 80 reproduces the congestion information with the bitmap table by the demultiplexer 102. As a result, the congestion information can be transferred as a serial signal.

  Here, the congestion information is generated as a bitmap and is transmitted and received as a serial signal. However, the congestion information may be represented by the number of the SSW in which congestion occurs. Also, a plurality of congestion notification dedicated lines may be provided and transferred by parallel signals.

  The discard threshold rewriting circuit 80 of the SSW receiver 60 (I) that has received the congestion information compares the destination of the switch header of the packet with the congestion information. When the destination of the switch header includes the congested SSW transmission unit 60 (E), the discard threshold rewriting circuit 80 lowers the value of the discard threshold field of the switch header of the packet. On the other hand, if not included, the discard threshold rewriting circuit 80 transmits the packet to the discard determination circuit as it is.

  With reference to FIG. 7, a switch header including information on the discard threshold and the destination SSW will be described. In FIG. 7, the packet is composed of a header 608 and data 609. The header 608 includes a discard threshold 610 and a destination bitmap 611.

  The discard threshold field 610 is 2 bits. Four levels of 0 to 3 can be represented by 2 bits, and the closer to 0, the easier it is to discard, the closer to 3, the less likely to be discarded. The destination bitmap is represented by 8 bits for 8 SSWs. In the destination bitmap, the bit corresponding to the destination SSW is expressed as 1. The case indicated by the destination bitmap 600 is a unicast packet addressed to SSW # 7. In the case of the destination bitmap 601, multicast packets addressed to SSW # 1 and # 5, in the case of the destination bitmap 602, multicast packets addressed to SSW # 4 and # 5 and # 6 and # 7, and in the case of the destination bitmap 603, SSW This is a unicast packet addressed to # 3.

  Returning to FIG. 4, the discard determination circuit 160 reads the discard threshold of the packet switching header and compares it with the queue length of the SSW transmission queue. When the queue length is smaller than the discard threshold, the discard determination circuit 160 transmits the packet to the SSW transmission queue. On the other hand, when the queue length is longer than the discard threshold, the discard determination circuit 160 discards the packet without transmitting it to the SSW transmission queue.

  With reference to FIG. 8, the rewriting of the congestion threshold and the packet discard will be described. In FIG. 8, the discard threshold rewriting circuit 80 includes a register 802, a comparator 803, and a subtracter 804. The register 802 stores a congestion information bitmap. The comparator 803 compares the congestion information bitmap and the destination bitmap. The subtracter 804 decreases the discard threshold value.

  The comparator 803 compares the destination bitmap 801 of the switch header with the congestion information bitmap 802. When the destination includes an SSW in which congestion occurs, the subtracter 804 subtracts 1 from the discard threshold 800 and rewrites it to the discard threshold 805. When the destination does not include an SSW in which congestion has occurred, the subtractor 804 sets the discard threshold 800 as the discard threshold 805 as it is.

  The discard threshold determination circuit 160 includes a comparator 807 and a determiner 808. The comparator 807 compares the discard threshold with the queue length. The determiner 808 determines discard.

  The comparator 807 compares the discard threshold value 805 after rewriting with the queue length 806 of the SSW transmission queue 90. When the queue length 806 is smaller than the discard threshold 805, the determiner 808 transmits the packet to the SSW transmission queue 90. On the other hand, when the queue length 806 is larger than the discard threshold 805, the determiner 808 discards the packet.

  With reference to FIG. 9, a flow of discard threshold rewriting and discard will be described. In FIG. 9, a congestion information bitmap 700 is used in which the SSW field in which congestion occurs is 1. When it is found from the congestion information bitmap 700 that congestion has occurred in the SSW # 1, the discard threshold rewriting circuit 80 determines whether or not the SSW # 1 address is included from the destination bitmap 701 in the switch header. If included, the discard threshold rewriting circuit 80 rewrites the value of the discard threshold 702 of the corresponding packet to be smaller. In FIG. 9, since packets 1 and 2 are applicable, the discard threshold rewriting circuit 80 decreases the discard threshold value of the packets 1 and 2 by one.

  The discard determination circuit 160 constantly monitors the queue length 703 of the SSW transmission queue 90. The discard determination circuit 160 compares the packet with a packet discard threshold 702 when transmitting the packet to the SSW transmission queue 90. The discard determination circuit 160 transmits the packet having the discard threshold 702 larger than the queue length 703 to the SSW transmission queue 90. On the other hand, the discard determination circuit 160 discards packets whose discard threshold value 702 is the queue length 703 or less.

  In FIG. 9, the discard determination circuit 160 discards packets 1 and 2 because the discard threshold is equal to or less than the queue length. On the other hand, the discard determination circuit 160 transmits packets 0 and 3 to the SSW transmission queue. In the above description, the discard threshold is always subtracted from 1. However, the number of matching destinations and SSWs where congestion occurs is counted, and the discard threshold is subtracted by the number of the matching numbers. Also good.

  With reference to FIG. 10, the process in the SSW receiver will be described. FIG. 10 shows the flow in FIG. In step 300, the SSW receiving unit 60 </ b> A (I) sends the input congestion information to the discard threshold rewriting circuit 80. In step 301, the discard threshold rewriting circuit 80 refers to the destination bitmap in the switch header. In step 302, the discard threshold rewriting circuit 80 determines whether or not the destination includes the destination of the SSW in which congestion has occurred. If so, the process proceeds to step 303. If not, the process proceeds to step 304. In step 303, the discard threshold rewriting circuit 80 rewrites the discard threshold value to a smaller value, and proceeds to step 304. In step 304, the discard determination circuit 160 refers to the queue length of the SSW transmission queue 90. In step 305, the discard determination circuit 160 compares the discard threshold of the switch header with the queue length. If the queue length is smaller than the discard threshold, the process proceeds to step 306 and transmits the packet to the SSW transmission queue. Is discarded.

With reference to FIG. 11, the overall processing flow of the first embodiment will be described. In FIG. 11, in step 400, the congestion monitoring circuit 120 of the CSW 70 monitors the queue length of the CSW transmission queue 110. If the queue length exceeds a predetermined reference value (YES), the processing proceeds to step 401 and is handled. The SSW receiving unit 60 (I) that determines that congestion has occurred, notifies the congestion information generation circuit 100 of the occurrence of congestion. In step 402, when the congestion information generation circuit 100 receives the congestion notification, the congestion information generation circuit 100 generates a congestion information bit map indicating which SSW is congested, and all the SSW receiving units 60 ( To I). In step 403, the discard threshold rewriting circuit 80 that has received the congestion information bitmap rewrites the discard threshold of a packet that includes a congested SSW as a destination to a small value. In step 404, the discard determination circuit 160 compares the packet discard threshold with the queue length of the SSW transmission queue 90. If the queue length is smaller than the discard threshold, the process proceeds to step 405 and transmits the packet to the SSW transmission queue. Proceed to 406 and discard the packet.
As a result, a packet including an SSW destination in which congestion occurs is easily discarded in the SSW transmission queue, and the influence of delay due to congestion can be reduced as a whole apparatus.

  A network relay device 1000A according to the second embodiment will be described with reference to FIG. In FIG. 12, the congestion information of the network relay device 1000A is notified to the SSW receiving unit using the existing CPU bus 170. The network relay apparatus 1000A includes a packet transfer receiver 50 (I), an SSW receiver 60A (I), a CSW 70A, an SSW transmitter 60 (E), a packet transfer transmitter 50 (E), and a CPU 130. Have. The packet transfer receiving unit 50 (I) and the packet transfer transmitting unit 50 (E) are equivalent to the packet transfer unit 50, and the SSW receiving unit 60A (I) and the SSW transmitting unit 60 (E) are equivalent to the SSW 60. The packet transfer receiving unit 50 (I) adds a switch header generated from the packet analysis result and the device state to the packet. The SSW receiving unit 60A (I) includes a discard threshold rewriting circuit 80 that rewrites the discard threshold field of the switch header, an SSW transmission queue 90 that temporarily stores packets to be transmitted to the CSW, a discard threshold field of the switch header, and SSW transmission A discard determination circuit 160 that compares the queue lengths of the queues and determines whether to send or discard the packet to the SSW transmission queue is provided. The CSW 70A refers to the switching information, determines the output destination and switches the packet, the switching unit 200, the CSW transmission queue 110 that temporarily stores the packet to be transmitted to the SSW transmission unit, and the congestion monitoring that monitors the CSW transmission queue The circuit 120 includes a congestion information generation circuit 100A that generates congestion information based on the information sent from the congestion monitoring circuit 120, and a congestion information storage buffer 210 for storing the congestion information. The SSW transmission unit 60 (E) analyzes the switch header of the packet and determines whether to transmit to the packet transfer unit. The packet transfer receiving unit 50 (E) deletes the switch header of the packet. The CPU 130 monitors all SSWs and CSWs.

  The method of knowing the occurrence of congestion is the same as in the first embodiment, but when the congestion information generating circuit 100A generates the congestion information, the congestion information is written in the congestion information storage buffer 210. The CPU 10 periodically accesses the congestion information storage buffer 210, reads the written congestion information, and notifies each SSW receiving unit via the CPU bus. The method of processing the congestion information by the SSW receiving unit 60A (I) is the same as that in the first embodiment.

  With reference to FIG. 13, a network relay device 1000B according to the third embodiment will be described. In FIG. 13, the network relay apparatus 1000B provides a congestion information rewriting circuit 140 at the output of the transmission queue 110 of the CSW 70B. Further, the SSW transmission unit 60A (E) includes a header analysis circuit 150.

  The congestion information generation circuit 100B generates congestion information based on the information sent from the congestion monitoring circuit 120. The congestion information generation circuit 100B transmits the congestion information to the header analysis circuit 150. The congestion information rewriting circuit 140 rewrites the value of the congestion information field of the switch header. The header analysis circuit 150 analyzes the switch header of the packet. The header analysis circuit 150 takes out the congestion information and determines whether or not to send it to the packet transfer transmission unit 50 (E).

  The method of knowing the occurrence of congestion is the same as in the first embodiment, but the congestion information generation circuit 100B generates congestion information and transmits it to the congestion information rewriting circuit 140 that exists for each SSW. Each congestion information rewriting circuit 140 updates the congestion information field of the switch header addressed to the responsible SSW. When the packet addressed to the SSW assigned for the preset time does not flow, the congestion information rewriting circuit 140 generates a dummy packet, writes the congestion information in the congestion information field of the switch header, and transfers it. When the packet is transferred to the SSW transmission unit 60A (E), the header analysis circuit 150 reads the congestion information from the header and transfers it to the SSW reception unit 60A (I). The method of processing the congestion information by the SSW receiving unit 60A (I) is the same as that in the first embodiment.

  A congestion information field is provided in the header of data transmitted from the CSW 70 of the CSW 70 network relay apparatus 1000B to the SSW transmission unit 60A (E). With reference to FIG. 14, a header provided with a congestion information field will be described. In FIG. 14, as is clear from the comparison with FIG. 7, congestion information 612 is added to the header 608. When the destination bitmap is not used after switching is performed by the switching unit 200 of the CSW 70, the congestion information field 612 may be shared with the destination bitmap field 611.

  With reference to FIG. 15, the frame discarding process due to the congestion of the network relay device 1000B will be described. In FIG. 15, the network relay apparatus 1000B determines whether or not the queue length of the CSW transmission queue exceeds the standard (S501). If YES, the network relay device 1000B determines whether congestion has occurred in the CSW (S502). The network relay device 1000B creates a congestion information bitmap (S503). The network relay apparatus 1000B determines whether a packet to be transmitted for each SSW is within a certain period (S504). When YES, the network relay device 1000B writes the congestion information bitmap in the packet header of the transmission packet (S504). When NO in step 503, the network relay device 1000B generates a dummy packet and writes a congestion information bitmap in the packet header of the dummy packet (S505). After step 504 or step 505, the SSW transmission unit 60A (E) extracts the congestion information bitmap from the packet header and transmits it to the SSW reception unit 60A (I) (S506). The network relay apparatus 1000B rewrites the discard threshold of the packet header including the SSW in which the congestion occurs as a destination smaller than the congestion information bitmap (S507). The network relay apparatus 1000B determines whether the discard threshold is smaller than the queue length of the SSW transmission queue (S508). If YES, the network relay device 1000B transmits the target frame to the SSW transmission queue (S509) and ends. If NO in step 508, the network relay apparatus 1000B discards the target frame (S510) and ends.

  Referring to FIG. 16, a description will be given of a packet transfer apparatus 1000C in which the number of CSWs 70 is increased to two and the number of CPUs 10 is increased to two. In FIG. 16, the network relay device 1000 </ b> C includes a plurality of lines 20, a plurality of packet transfer units 31, a plurality of switching units 41, and two CPUs 10.

  The packet transfer unit 31 in FIG. 16 includes a bus selection unit 220 that selects either the CPU bus 170 (0) or the CPU bus 170 (1) in addition to the packet transfer unit 30 in FIG. The SSW 60 selects one CSW 70 in operation among the plurality of CSWs 70 and transfers the packet data.

  The switching unit 41 in FIG. 16 includes a bus selection unit 221 that selects either the CPU bus 170 (0) or the CPU bus 170 (1) in addition to the switching unit 40 in FIG.

  Further, the CPU 100 (0) and the CPU 100 (1) are connected to the plurality of packet transfer units 31 and the plurality of switching units 41 via the two CPU buses 170 (0) and the CPU bus 170 (1), respectively. ing.

  One of the CPU 100 (0) and the CPU 100 (1) operates as an active system, and monitors and controls the entire network relay device. The other operates as a standby system in case the active system becomes inoperable for some reason.

  The two switching units 41 may perform a switching process using one as an active system and the other as a standby system.

  When the network relay apparatus 1000C of FIG. 16 has k switching units 41, the switching process is performed using k-1 switching units 41 as the active system, and one switching unit has k-1 units. It can also be made to stand by as a backup system of the switching unit 41.

  Further, when the network relay device of FIG. 16 has k switching units 41, the switching processing is performed using all k switching units 41 as the active system, and i switching units 41 become inoperable. In such a case, it is possible to take various operation forms such as continuing the operation with k−i switching units 41.

  Further, the network relay device of FIG. 16 has n × k data buses 180 when there are n packet transfer units 31 and k switching units, and SSW60 (0) to SSW60 (n−1). And CSW70 (0) to CSW70 (k-1) may be connected in any combination.

The network relay device according to the fourth embodiment further includes n packet transfer units 31, k switching units, and n × k congestion information notification dedicated lines 190 (not shown) in addition to the configuration diagram of FIG. 16. Then, SSW60 (0) to SSW60 (n-1) and CSW70 (0) to CSW70 (k-1) are connected in an arbitrary combination.
The method for generating congestion information in the CSW 70 and transferring the congestion information to the SSW 60 is the same as in the first embodiment.

  In the fifth embodiment, congestion information from a plurality of CSWs 70 is transferred to one SSW 60. When the congestion information is stored in the congestion information bitmap 802 in the SSW 60, the congestion information from the plurality of CSWs 70 is ORed for each bit, or the result of arbitrary calculation is stored, thereby storing the congestion of the plurality of CSWs 70. Information can be reflected in the congestion information bitmap 802.

  It is also possible to provide the SSW 60 with a plurality of congestion information bitmaps 802, each of which stores information about a plurality of CSWs 70. For example, k congestion information bitmaps 802 (0) to 802 (k-1) are provided corresponding to k CSWs 70 (0) to CSW70 (k-1). In this case, the SSW 60 further includes a plurality of comparators 803 (0) to 803 (k−1), compares the destination bit map 801 and the plurality of congestion information bit maps 802, and subtracts 804 based on a plurality of comparison results. It is also possible to reflect this in the reduction of the discard threshold. When the destination bitmap 801 includes a congested SSW of only the congestion information bitmap 802 (0), the discard threshold (after rewriting) 805 is set to a value obtained by subtracting 1 from the discard threshold (before rewriting) 800. When the bitmap 801 includes the congested SSW of the congestion information bitmap 802 (0) and also includes the congested SSW of the congestion information bitmap 802 (1), the discard threshold (after rewriting) Can be taken by various methods such as a value obtained by subtracting 2 from the discard threshold (before rewriting).

  The congestion information transfer method according to the fifth embodiment can also use the CPU bus 170 as in the second embodiment, and this embodiment is referred to as a sixth embodiment.

  In the sixth embodiment, the congestion information is transferred from the plurality of CSWs 70 to the plurality of SSWs 60 in the network transfer apparatus of FIG. 16, as in the second embodiment, the CPU 10 (0) and the CPU bus 170 (0) or the CPU 10 (1) and Transfer is performed using either of the CPU bus 170 (1).

  The operation of rewriting the discard threshold using the congestion information from the plurality of CSWs 70 in the SSW 60 is the same as in the fifth embodiment. The congestion information transfer method of the fifth embodiment can use the congestion information field of the switch header as in the third embodiment, and this embodiment is referred to as a sixth embodiment.

  In the sixth embodiment, the congestion information is transferred from the plurality of CSWs 70 to the plurality of SSWs 60 in the network transfer apparatus of FIG. 16 using the congestion information field of the switch header as in the third embodiment.

  The operation of rewriting the discard threshold using the congestion information from the plurality of CSWs 70 in the SSW 60 is the same as in the fifth embodiment.

  10 ... CPU, 20 ... line, 30 ... packet transfer unit, 31 ... packet transfer unit, 40 ... switching unit, 41 ... switching unit, 50 ... packet transfer unit, 60 ... sub crossbar switch (SSW), 70 ... crossbar Switch (CSW) 80 ... Discard threshold rewriting circuit 90 ... Multicast SSW transmission queue 100 ... Congestion information generation circuit 101 ... Multiplexer 102 ... Demultiplexer 110 ... CSW transmission queue 120 ... Congestion monitoring circuit 121 ... Queue length register, 122 ... congestion reference value register, 123 ... size comparator, 130 ... scheduler, 140 ... congestion information rewriting circuit, 150 ... header analysis circuit, 160 ... discard decision circuit, 170 ... CPU bus, 180 ... data bus, 190 ... Congestion notification dedicated line, 200 Switching unit 210 ... Congestion information storage buffer 220 ... Bus selection unit 600 ... Destination bitmap example 1, 601 ... Destination bitmap example 2,602 ... Destination bitmap example 3,603 ... Destination bitmap example 4,604 ... Congestion information bit map example 1, 605 ... Congestion information bit map example 1, 606 ... Congestion information bit map example 1, 607 ... Congestion information bit map example 1, 608 ... Switch header part, 609 ... Data part, 610 ... Discard threshold field 611 ... Destination bitmap field, 612 ... Congestion information field, 700 ... Congestion information bitmap, 701 ... Destination bitmap, 702 ... Discard threshold, 703 ... SSW transmission queue queue length, 800 ... Discard threshold (before rewriting), 801 ... Destination bitmap, 802 ... Congestion information bitmap, 803 ... Comparison , 804 ... subtractor, 805 ... waste threshold (rewritten), 806 ... SSW transmission queue queue length, 807 ... comparator, 808 ... determination unit, 900 ... packet transfer apparatus, 1000 ... network relay apparatus.

Claims (4)

A network relay having a plurality of packet transfer units that perform packet transfer, a crossbar switch unit that performs packet switching, and a plurality of switches that transmit and receive packets to and from the packet transfer unit and control input and output of the crossbar switch In the device
The crossbar switch sends the detected congestion information to the switch;
A network relay device, wherein a switch that receives congestion information rewrites a discard threshold of a switch header. The network relay device according to claim 1,
The network relay device, wherein the crossbar switch transmits the congestion information to the switch using a CPU line. A network relay having a plurality of packet transfer units that perform packet transfer, a crossbar switch unit that performs packet switching, and a plurality of switches that transmit and receive packets to and from the packet transfer unit and control input and output of the crossbar switch In the device
The crossbar switch writes the detected congestion information in a switch header and sends it to the switch,
A network relay device, wherein a switch that receives congestion information rewrites a discard threshold of a switch header. The network relay device according to claim 1 or 3, wherein
The switch includes a transmission queue and a discard determination unit,
The discard determination unit compares the queue length of the transmission queue with the discard threshold, and discards the received packet when the discard threshold of the received packet is equal to or less than the queue length. apparatus.

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