Switching device and switching system

Abstract

The switching device (10) of the present invention comprises a plurality of optical transmitters (13) that convert input electrical packets with set priorities into optical packets and transmit them; a plurality of optical receivers (15) that receive the optical packets and convert them into electrical packets; an optical switch (14) that is arranged between the plurality of optical transmitters and the plurality of optical receivers and transmits the optical packets input from the optical transmitters to one of the plurality of optical receivers; and a control unit (17) that is arranged in connection with the optical receivers and holds converted electrical packets with lower priorities and transmits converted electrical packets with higher priorities first. As a result, the present invention can provide a switching device that can reduce latency and power consumption.

Description

[Technical Field]

[0001] The present invention relates to a switching device and a switching system for switching packets. [Background technology]

[0002] In recent years, the amount of data processed by computers has increased, and there has been interest in new computer architectures to improve computer processing capabilities.

[0003] In the computer architecture, for example, as shown in FIG. 14, a switching system 70 is connected to a plurality of hosts (CPUs, GPUs, accelerators, etc.) 72 via an input / output interface 71, and is also connected to a memory 73.

[0004] In computer processing, the bit rates of signals generated by hosts are increasing dramatically. For bit rates exceeding 10 Gb / s, electrical signals can only travel a limited distance of a few centimeters. Therefore, optical links are required to interconnect hosts that are about 10 meters apart.

[0005] However, the packet switching module is an ASIC switch and can only process electrical signals, so optical / electrical / optical conversion is required in the switch for the optical signals of the optical link. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] J. Dean, "1.1 The Deep Learning Revolution and Its Implications for Computer Architecture and Chip Design," 2020 IEEE International Solid-State Circuits Conference (ISSCC), 2020, pp.8-14, doi: 10.1109 / ISSCC19947.2020.9063049. Summary of the Invention [Problem to be solved by the invention]

[0007] In a packet switch, for example, assuming 128 hosts each with a unit generating 25 Gb / s data packets, a switch throughput of 6.4 Tb / s is required. If this throughput is achieved using an ASIC switch configuration (configuration using optical / electrical / optical conversion), the following problems arise:

[0008] First, ASIC switches of this scale exhibit latencies of over 400 nsec for the fastest scenarios with cut-through packets, resulting in high latency for incoming signals. This creates a problem for data flows with large numbers of packets, resulting in long latency for reception completion.

[0009] In addition, ASIC switches consume a lot of power, concentrating power in a small chip area. To deal with the heat generated by this high power density, air cooling has almost reached its limits, making water cooling essential.

[0010] Other issues include the increased footprint of the switch's optoelectronic interface, especially when higher throughput is required, and the increased energy density per unit area, which leads to increased power consumption. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the switching device of the present invention comprises a plurality of optical transmitters that convert input priority-set electrical packets into optical packets and transmit them; a plurality of optical receivers that receive the optical packets and convert them into electrical packets; an optical switch that is arranged between the plurality of optical transmitters and the plurality of optical receivers and transmits the optical packets input from the optical transmitters to one of the plurality of optical receivers; and a control unit that is arranged connected to the optical receivers and holds the converted electrical packets with a lower priority and transmits the converted electrical packets with a higher priority first. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a switching device and a switching system that can reduce latency and power consumption. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing the configuration of a switching device according to a first embodiment of the present invention. [Figure 2A] FIG. 2A is a diagram for explaining the operation of the switching device according to the first embodiment of the present invention. [Figure 2B] FIG. 2B is a diagram for explaining the operation of the conventional switching device. [Figure 3A] FIG. 3A is a diagram illustrating the operation of the switching device according to the first embodiment of the present invention. [Figure 3B] FIG. 3B is a diagram for explaining the operation of the switching device according to the first embodiment of the present invention. [Figure 3C] FIG. 3C is a diagram for explaining the operation of the switching device according to the first exemplary embodiment of the present invention. [Figure 4] FIG. 4 is a diagram for explaining the operation of a conventional switching device. [Figure 5] FIG. 5 is a block diagram showing the configuration of a switching device according to the second embodiment of the present invention. [Figure 6] FIG. 6 is a diagram for explaining the operation of the switching device according to the second embodiment of the present invention. [Figure 7A] FIG. 7A is a diagram illustrating the operation of the switching device according to the second embodiment of the present invention. [Figure 7B] FIG. 7B is a diagram for explaining the operation of the switching device according to the second embodiment of the present invention. [Figure 7C] FIG. 7C is a diagram illustrating the operation of the switching device according to the second embodiment of the present invention. [Figure 7D] FIG. 7D is a diagram illustrating the operation of the switching device according to the second embodiment of the present invention. [Figure 8] FIG. 8 is a diagram for explaining the operation of the switching device according to the second embodiment of the present invention. [Figure 9A] FIG. 9A is a diagram illustrating the operation of the switching device according to the second embodiment of the present invention. [Figure 9B] FIG. 9B is a diagram for explaining the operation of the conventional switching device. [Figure 10] FIG. 10 is a block diagram showing the configuration of a switching system according to the third embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram showing the configuration of a switching system according to the fourth embodiment of the present invention. [Figure 12] FIG. 12 is a diagram for explaining the operation of the switching system according to the fourth embodiment of the present invention. [Figure 13] FIG. 13 is a block diagram showing an example of the configuration of a switching system according to an embodiment of the present invention. [Figure 14] FIG. 14 is a block diagram showing the configuration of a conventional switching system. DETAILED DESCRIPTION OF THE INVENTION

[0014] First Embodiment A switching device according to a first embodiment of the present invention will be described with reference to FIGS. 1A to 4. FIG.

[0015] <Switching device configuration> As shown in FIG. 1, a switching device 10 according to this embodiment includes an optical transmitter 13, an optical switch 14, an optical receiver 15, and a control unit 17.

[0016] Packet 1 is sent from the sending host 3, compressed and divided (packet 2) by the optical transmitter 13, switched by the optical switch 14, and received by the receiving host 4 via the optical receiver 15. Here, a priority is set for packet 1 sent from the sending host 3.

[0017] In the optical switch 14, all packets destined for the same output port are sent simultaneously, so that the destination output port receives different packets at the same time.

[0018] The control unit 17 is an electric chip, and is arranged so as to be connected to the optical receiver 15. The control unit 17 also performs processing such as arbitration on the packets 2 output from the optical switch .

[0019] A control unit 17 is assigned locally to each receiving host 4 and performs self-management of traffic entering the receiving host 4. The control unit 17 is located close to the receiving host 4 and quickly updates data retrieval priorities.

[0020] Furthermore, the control unit 17 manages the processing of communications from a single receiving host 4 and can operate at high speed.

[0021] The information channel, in addition to the data link, connects the receiving host 4 and the control unit 17 .

[0022] <Switching device operation> Figure 2A shows packet processing in switching device 10. For comparison, Figure 2B shows a conventional non-blocking switch 20.

[0023] In a conventional electrical non-blocking switch 20, the bandwidth of all output ports is fixed, and only one packet can be sent at a time. For example, if flow B (101_2) and flow C (101_3) are sent to the same output port, they are processed by a single band with a fixed bandwidth (Figure 2B).

[0024] On the other hand, in the optical switch 14 of the switching device 10 according to this embodiment, the bandwidth of each output port is variable, and all packets input to the switch can be adjusted. For example, as shown in FIG. 2A, the bandwidth is changed and processing is performed in two bands. Here, the bandwidth of the output port is half the total throughput (bandwidth) of the switch.

[0025] In this manner, optical switch 14 is capable of supporting a high bandwidth per output port.

[0026] In the switching device 10, as shown in FIG. 2A, the low priority input data (packet C) 102_3 is buffered and held for a long period of time in the RAM of the control unit 17.

[0027] On the other hand, the data (packet B) 102_2 with a higher priority is transmitted first.

[0028] The input data (packet C) 102_3 with a lower priority is transmitted after the transmission of the data (packet B) 102_2 with a higher priority is completed.

[0029] The switching apparatus 10 may also have an optical data link located within the control unit 17, allowing optical data to be transmitted directly between the output ports of the switch and a receiving host 4 capable of processing optical input signals.

[0030] As shown in FIGS. 3A to 3C, the optical switch 14 can be configured based on a broadcast-and-select system.

[0031] Signals entering different switch ports are multiplexed, for example, at different wavelengths. Each input signal is sent to all output ports and selected at each output port based on the desired signal destination.

[0032] For example, as shown in FIG. 3A, an input packet 1_1 from a sending host A (3_1) is branched by a splitter 18, and the branched packets 2_1 to 2_4 are transmitted to receiving hosts 4_1 to 4_4.

[0033] 3B, input packets 1_1 and 1_4 from transmitting hosts A and D (3_1 and 4) are branched by splitter 18, and the branched packets 2_1 to 2_4 are selected by optical selection filter 19 at the output port and transmitted to receiving hosts 4_1 to 4_4. Here, a fast tunable filter or a polarizing filter element can be used as the optical selection filter 19.

[0034] Also, as shown in Figure 3C, input packets 1_1 and 1_4 from transmitting hosts A and D (3_1, 4) are each split by splitter 18, and the branched packets 2_1 to 2_4 are received by multiple optical receivers 15 for each packet and transmitted to receiving hosts 4_1 to 4_4.

[0035] <Effects> In the conventional non-blocking packet switch 20, a data packet input to any input port is switched to the desired output port.

[0036] When multiple packets are simultaneously transmitted to the same output port, contention occurs and arbitration is performed for the colliding packets: the higher priority packet is selected for transmission first, while other packets are buffered and transmitted subsequently.

[0037] In this way, in the conventional non-blocking packet switch 20, arbitration is required for scheduling when packets are sent simultaneously to the same destination.

[0038] Typically, the arbitration process follows a centralized control scheme, where information regarding data availability, priority, and selection is collected in a central control unit (not shown) of the system before a decision is made in arbitration. The accuracy of this decision highly depends on the availability of all necessary information that has been updated recently. However, in dynamic computing systems, it is difficult to maintain the accuracy of the recently updated information.

[0039] 4, a receiving host 4 is assigned a computational task to reduce two data flows, flow A (201_1) and flow B (201_2). Host 4 has already processed flow A and is waiting to receive flow B.

[0040] On the other hand, flow C (201_3) is another flow sent to host 4, and arrives at the switch before flow B (201_2) arrives with a time difference. If the time difference is longer than 0 (zero), the switch sends flow C (201_3) to host 4.

[0041] Here, the time difference is represented as ΔT.

[0042] When the optical switch 14 is operated, the transmission of flow B does not start until the transmission of flow C is completely completed.

[0043] When the electrical switch 21 is operated, packet arbitration is initiated between flow C (201_3) and flow B (201_2) when flow B (201_2) arrives. Priority is given to flow B (201_2) only if the arbitrator 22 of the switch has already been notified. If there is a failure or delay in the arbitrator 22 being notified about the host 4's request to give top priority to flow B (201_2), flow B will not be switched fast enough even if the time difference is 0 (zero).

[0044] Since the host 4 is a processing unit, the priorities for retrieving data change rapidly. It is therefore difficult to continuously update the arbitrator 22 with these changing priorities. Therefore, in handling the traffic of all systems, it is difficult for the arbitrator 22 to make the right decision fast enough for the large amount of highly dynamic data.

[0045] As described above, conventional non-blocking packet switches 20 perform arbitration using a centralized control method, and as the number of switch ports and processing power (throughput) increase, the process becomes more complex, resulting in increased latency and power consumption.

[0046] Furthermore, it is difficult to collect information necessary for the arbitration process, such as priority, according to a predetermined rule as the scale of the system increases.

[0047] On the other hand, in the switching device 10 according to the present embodiment, arbitration is performed by the output control unit 17 in a distributed control manner. Here, the host 4 connected to each output port determines which packet to process first. In this way, the control unit 17 can perform arbitration locally for each single host.

[0048] Here, all packets are output with a predetermined duration T. In other words, the data rate of the output signal is the same as the data rate of the input signal.

[0049] In this way, packets arriving at the same output port in different slots are converted to the initial (original) data rate, and packets are output in the order requested by the connected output hosts, thus giving the highest priority packets the lowest latency.

[0050] As a result, the switching device according to this embodiment can reduce latency and power consumption in switching, and can reduce (or eliminate) the burden of collecting information necessary for the arbitration process.

[0051] <Second embodiment> Next, a switching device according to a second embodiment of the present invention will be described with reference to FIGS. 5 to 9B.

[0052] <Switching device configuration> 5, an example of a switching device (packet switch) 30 according to this embodiment includes, in order, an input port 11, an input block 12, an optical transmitter 13, an optical switch 14, an optical receiver 15, and an output port 16. It also includes a control unit 17 connected to the optical receiver 15. In the switching device 30 according to this embodiment, the optical switch 14 operates in a time slot manner.

[0053] <Optical switch operation> The operation of the switching device (packet switch) 30 in this embodiment will be described with reference to FIG.

[0054] 6 shows the basic operation of a packet switch 30 that performs non-blocking processing, using a 4x4 switch as an example. This packet switch 30 is based on a time slot operation, which will be explained below.

[0055] First, packets are switched by input group, where arbitration is performed only among input packets of the same input group. This arbitration is performed for a small number of ports and low traffic, so it is fast.

[0056] Furthermore, an electrical packet 1 input to the switch has a bandwidth BW (bit / sec) and a duration T, and a desired output port 16 to which it is to be sent is set.

[0057] In the packet switch 30, a packet switching operation to any of the four output ports 16 is completed in time T. This is because if switching a single packet takes longer than T, the next incoming packet will be blocked, and continuous switching delays will accumulate.

[0058] Also, the input packet 1 is compressed by a factor (here 4) equal to the number of ports (i.e., the number of optical receivers to which the packet is sent) at the optical transmitter 13 to fit into the time slot. That is, the duration of the input packet is divided by a factor equal to the number of ports, which becomes T / 4. Also, in order to preserve the packet data content, the bandwidth is multiplied by the same factor, which becomes 4BW.

[0059] In this way, an input packet of light 2 is generated that satisfies these conditions.

[0060] Each optical input packet 2 is then distributed to a desired output port 16 in a periodic time slot by an optical switch 14. Here, the periodic operation of the switch is divided into four time slots.

[0061] Each time slot has a duration Δt of T / 4.

[0062] The distribution (switching) of the optical input packet 2 is repeatedly performed for each time slot according to a sequence made up of steps S1 to S4 (described later).

[0063] Finally, the packets are converted into electrical packets by the optical receiver 15 and output at a fixed duration from the packet switch 30. In other words, the data rate of the signal output from the packet switch 30 is the same as the data rate of the signal input thereto.

[0064] In this way, packets arriving in different time-reduced time slots will have their data rate changed to the original data rate, in the order of arrival of the packets, or by other arbitration prioritizing the change.

[0065] The switching operation of the optical switch 14 described above will be described with reference to Figures 7A to 7D. Each of Figures 7A to 7D shows an example of a series of switching operations in steps S1 to S4.

[0066] Packets are input to each of the four ports 11_1 to 11_4 in the packet switch 30. The packet input to the port 11_3 (packet C) has the highest priority and its desired output port is the port 16_3.

[0067] The packets (packets A and D) input to the ports 11_1 and 11_4 have the desired output ports 16_2 and 16_1, respectively, and have the second priority.

[0068] The packet (packet B) input to the port 11_2 has the desired output port as the port 16_4 and has the third priority.

[0069] First, packet C has the highest priority and is therefore transmitted to output port 16_3 for the duration of the first time slot (step S1, FIG. 7A).

[0070] Next, since packets A and D have the second priority, they are transmitted simultaneously to output ports 16_2 and 16_1, respectively, for the duration of the second time slot (step S2, FIG. 7B). Here, packets A and D are transmitted to different output ports, so no collision occurs.

[0071] Next, the packet input to port B (packet B) has the third priority and is therefore transmitted to output port 16_4 with the duration of the third time slot (step S3, FIG. 7C).

[0072] Finally, since the transmission (switching) of packets A to D has been completed in the previous step (step 3), no switching is performed during the duration of the fourth time slot (step S4, FIG. 7D).

[0073] Here, the duration of the first time slot, the duration of the second time slot, the duration of the third time slot, and the duration of the fourth time slot are represented by Δt1, Δt2, Δt3, and Δt4, respectively.

[0074] In this way, when the operation cycle (four steps) is completed, all input packets are switched to their desired output ports simultaneously in a non-blocking manner.

[0075] In this switching operation, in every step, each output port 16 is connected to only one input port 11, as shown in Figures 7A to 7D. Also, the input port 11 is connected to the desired output port 16, and in switching a packet input to the input port 11, the packet is placed in the correct (correct) time slot (with a divided duration).

[0076] Moreover, the optical switch 14 operates as shown in FIG.

[0077] Packets (packets A to D) are input to each of four ports 11_1 to 11_4 in the packet switch 30. Packets A to D have the same desired output port (16_2), and packets B, A, D, and C are prioritized in this order.

[0078] First, packet B has the highest priority and is therefore transmitted to output port 16_2 for the duration of the first time slot (step S1).

[0079] Next, since packet A has the second priority, it is transmitted to output port 16_2 for the duration of the second time slot (step S2).

[0080] Next, since packet D has the third priority, it is transmitted to the output port 16_2 for the duration of the third time slot (step S3).

[0081] Finally, since packet C has the fourth priority, it is transmitted to output port 16_2 for the duration of the fourth time slot (step S4).

[0082] In this way, when the operation cycle (four steps) is completed, all input packets are simultaneously switched to the desired output ports in a non-blocking manner. Here, packets A to D are transmitted in different time slots, so no collisions occur.

[0083] Thus, in packet switch 30, all input packets destined for the same output port are correctly (accurately) switched to that port at time T.

[0084] <Effects> The effects of the switching device 30 in this embodiment will be described below.

[0085] The optical switch in the first embodiment has problems such as a decrease in signal output level with an increase in the number of ports (FIG. 3A), and an increase in the number of constituent units such as optical selection filters 19, including high-speed wavelength selection filters, and optical receivers 15 (FIGS. 3B and 3C). In particular, controlling a large number of high-speed selection units is technically difficult and increases power consumption.

[0086] By introducing time slots and increasing the bit rate, the optical switch 14 in this embodiment can process large amounts of highly dynamic data sufficiently quickly and reduce power consumption without reducing the signal output level with the number of ports or increasing the number of component units.

[0087] Furthermore, in the switching device 10 according to this embodiment, arbitration according to the conventional centralized control method is distributed among the following steps to execute arbitration.

[0088] First, packets from different input groups are sent to the same output group in different time slots in the optical switch 14. The optical switch 14 can perform this step with high data rates and precise time control.

[0089] Arbitration is then performed by the output control unit 17 in a distributed control manner, where the host 4 connected to each output port decides which packet to process first. In this way, the control unit 17 can perform arbitration locally for each single host.

[0090] Here, all packets are output with a predetermined duration T. In other words, the data rate of the output signal is the same as the data rate of the input signal.

[0091] In this way, packets arriving at the same output port in different slots are converted to the initial (original) data rate, and packets are output in the order requested by the connected output hosts, thus giving the highest priority packets the lowest latency.

[0092] As a result, the switching device according to this embodiment can reduce latency and power consumption in switching, and can reduce (or eliminate) the burden of collecting information necessary for the arbitration process.

[0093] Furthermore, the effects of the switching device 30 will be explained in detail in comparison with a conventional non-blocking switch.

[0094] Fig. 9A shows the latency of a flow switched by the switching device 30. For comparison, Fig. 9B shows the latency of a flow switched by the conventional non-blocking switch 20.

[0095] For example, it is assumed that a flow A (1_10) having packets A1 (1_11) to A3 (1_13) and a flow D (1_40) having packets D1 (1_41) to D3 (1_43) are input and transmitted to the same output port.

[0096] In this case, in the conventional non-blocking switch 20, flows A (2_10) and D (2_40) are processed in a single band, as shown in Figure 9B, and delay times are accumulated. As a result, when the length (time) of one packet is T, the delay time is 3T, which is the length (time) of the flow sent immediately before.

[0097] Thus, in the conventional non-blocking switch 20, the delay time increases, and the latency increases.

[0098] On the other hand, in the switching device 30, flows A (2_10) and D (2_40) are processed in two bands as shown in Fig. 9A, so the delay time is hardly accumulated and is less than T. This delay occurs only in the first packet and is negligible compared to the length of the flow, 3T.

[0099] In this way, the switching device 30 has a short delay time and can reduce latency.

[0100] Also, in a typical electrical switch, an input packet passes through an input port of the switch, where its destination and priority are first inspected, and then a centralized arbitration is performed to determine which packet should be sent first among all packets destined for the same output port.

[0101] The complexity of the centralized arbitration process increases as the number of switch ports and throughput increases, resulting in increased communication latency and power consumption.

[0102] On the other hand, the switching device 30 can switch packets without performing centralized arbitration, which takes a long time, and therefore can reduce communication latency and power consumption.

[0103] Furthermore, since the optical switch 14 is responsible for part of the switching process, the switching capacity can be increased with lower power consumption than an ASIC using CMOS transistors.

[0104] Furthermore, because chiplets are used for the input block 12, the area occupied by the input block 12 can be reduced. As a result, even if an optical-electrical interface is implemented, the overall area of the packet switch (chip) does not increase. Therefore, the optical-electrical interface can be implemented without changing the chip area, and the throughput (processing capacity) of the switch can be increased. Furthermore, by using chiplets, power consumption can be reduced.

[0105] It also avoids contention between ports in the same block, allowing non-blocking processing.

[0106] Furthermore, in order to simultaneously transmit multiple packets to the same destination using a conventional packet switch, the same number of parallel optical receivers as the number of packets was required.

[0107] On the other hand, the switching device 30 creates a compact copy of each input packet at a high data rate and transmits the compact packets in short time slots. In this way, packets to the same destination can be transmitted in a time shorter than the actual packet input interval using time interleaving.

[0108] Here, the optical receiver 15 used in the switching device 30 can operate in response to such burst mode transmission.

[0109] The switching device 30 can easily implement a high-speed 4×4 optical switch device by being composed of four 1×4 switching units corresponding to different input ports 11. Here, in the 4×4 optical switch device, the time (transition time) required to transition from one switch mode (e.g., FIG. 7A) to another switch mode (e.g., FIG. 7B) is very short compared to the duration of an input packet.

[0110] For example, assuming that the transition time is negligible, with practically available technology the transition time can be reduced to 10 psec, which is extremely short compared to, for example, a 100 Gb / s Ethernet packet which has a duration of 120 nsec.

[0111] There may also be a short guard time between optical packets to avoid any data loss during switching.

[0112] The bandwidth of packets generated by the host is multiplied by a factor F (the number of switch ports). For example, in an 8x8 switch, 25Gb / s electrical packets need to be converted into 200Gb / s optical packets, which are generated by directly modulated lasers and multilevel modulation formats.

[0113] Here, since the distance between hosts assumed in this embodiment is short, high data rates can be achieved, and the optical dispersion effect is negligible.

[0114] Additionally, high bitrate packets may be generated in other ways. The switch may be used as a core switching unit in a hybrid switching architecture to scale up the number of interconnected hosts without centralized control.

[0115] <Third embodiment> Next, a switching system 40 according to a third embodiment of the present invention will be described with reference to Fig. 10. The switching system 40 is scaled by grouping hosts.

[0116] <Switching system configuration> As shown in FIG. 10, a switching system 40 according to this embodiment includes a plurality of source groups 3_10 to 3_40 on the transmitting side, and each source group includes a plurality of transmitting hosts (for example, 3_11, 3_12) and a switching element 41.

[0117] The receiving side is provided with a plurality of destination groups (e.g., 4_20, etc.), and each destination group is composed of an optical receiver 15, a control unit 17, a receiving-side switch 43, and a plurality of receiving hosts (e.g., 4_21, 4_22, etc.). The other configurations are the same as those of the first embodiment.

[0118] The switching element 41 is a low-radix ASIC switch chip.

[0119] The optical switch 14 has four input / output ports and an operating cycle divided into four time slots, where a group of sending hosts 3_10 to 3_40 connects at the ports of the optical switch 14, rather than individual host units.

[0120] For example, in the transmission group A (3_10), the ASIC switch 41 and the two hosts A1 and A2 (3_11 and 3_12) are arranged close to each other. The ASIC switch 41 and the two hosts 3_11 and 3_12 are electrically linked at short distances.

[0121] Increasing the number of host units per group improves scalability. In order to take advantage of the characteristics of the electrical link, it is desirable to have around 10 host units per group.

[0122] As shown in FIG. 10, destination groups A to D (3_10 to 3_40) are connected to the input ports of the optical switch 14, and destination groups 4_10 to 4_40 are connected to the output ports.

[0123] Hosts in the same group exchange packets using the ASIC switch 41. For example, the ASIC switch 41 in group A (3_10) is used to interconnect hosts A1 and A2 (3_11, 3_12). Packets between hosts in different groups (hereinafter referred to as "inter-group packets") are exchanged via interconnection with the optical switch 14.

[0124] At any time slot, each destination (output) group connects with only one transmit (input) group. Inter-group packet switching of transmit groups is handled by placing these packets (reduced duration optical packets) within the exact time slot at which the transmit group connects with the desired destination group.

[0125] <Switching system operation> The operation of the switching system 40 in this embodiment will be described with reference to FIG.

[0126] In the switching system 40, the end-to-end transmission of an inter-group packet from the source host to the destination host consists of the following three steps:

[0127] As a first step, electrical switching is performed on packets at the destination group level rather than the destination host level.

[0128] In particular, electrical switching is performed according to destination groups using the local ASIC switch 41 to split the packets generated by the host among the sending groups 3_10 to 3_40.

[0129] Here, inter-group packets simultaneously transmitted to the same group are collected in the destination virtual queue regardless of differences in destination hosts. Here, queues G1 to G4 (42_1 to 42_4) correspond to destination groups 4_10 to 4_20.

[0130] As an example, consider two packets simultaneously sent from hosts A1 and A2 (3_11, 3_12) to hosts 4_22 and 4_21 in destination group 4_20, respectively. At this time, both packets are switched to queue G2 (42_1).

[0131] For example, packets from hosts A1 and A2 (3_11 and 3_12) are transmitted at twice the bandwidth of 25 Gb / s.

[0132] As a second step, optical switching is performed on the packets (reduced duration optical packets) sent to the desired destination group by placing each packet in a matching time slot in the optical switch 14.

[0133] For example, a packet is divided into four parts, compressed four times, and each part is assigned to the first to fourth time slots within a time period T, and transmitted with a bandwidth of 200 Gb / s.

[0134] In detail, packets are sent to each optical switch 14 only from the corresponding queue in the ASIC switch 41 .

[0135] Here, hosts in the same group generate packets at the same time that are all sent to the same group.

[0136] Also, to avoid contention, all these simultaneous packets are coordinated into the same time slot of the optical switch 14. The bandwidth of the optical transmitter 13 makes this possible.

[0137] Here, it is not necessary to separate packets from different sending hosts using different wavelengths for identification, but a WDM-based transmitter can be used to meet the high bandwidth requirements associated with an increasing number of host units per group.

[0138] As a third step, the packets arrive at their desired destination group, e.g., all 25 Gb / s packets are received at time T.

[0139] Subsequently, electrical switching is performed on the packets.

[0140] In particular, multiple packets may be sent to the same end host at the same time, with higher priority packets being processed first. The self-management of incoming data packets described above is performed for the local ASIC switch 41 that is assigned to receive the data.

[0141] As described above, in the switching system 40 according to the present embodiment, arbitration according to the conventional centralized control method is divided into the following three steps to execute arbitration.

[0142] In the first step, the input ports of the switching system 40 are divided into groups (e.g., 3_10 to 3_40), and packets in each group are processed independently of other packets. Within an input group, output groups that are input simultaneously and have the same destination are treated as the same group and sent together without arbitration. In this way, grouping the input ports on a small scale allows this step to be processed quickly.

[0143] Thereafter, as in the second embodiment, a processing step by the optical switch is executed as the second step, and an arbitration step is executed as the third step.

[0144] As a result, the switching device according to this embodiment can reduce latency and power consumption in switching, and can reduce (or eliminate) the burden of collecting information necessary for the arbitration process.

[0145] Furthermore, according to the switching system 40 of this embodiment, the number of interconnected hosts can be increased by grouping the hosts, thereby improving the expandability of the system.

[0146] <Fourth embodiment> Next, a switching system 50 according to a fourth embodiment of the present invention will be described with reference to Figures 11 to 13. The switching system 50 is scaled by optical multicasting (optical multiplexing).

[0147] <Switching system configuration> 11, a switching system 50 according to this embodiment includes an optical multiplexing unit 51 between an optical transmitter 13 and an optical switch 14, and a first demultiplexing unit 52 and a second demultiplexing unit 53 between the optical switch 14 and an optical receiver 15. The other configurations are the same as those of the third embodiment.

[0148] A plurality of optical transmitters 13 are connected to the optical multiplexing unit 51 .

[0149] An output port of the optical switch 14 is connected to the first demultiplexing unit 52. An output port of the first demultiplexing unit 52 is connected to the second demultiplexing unit 53.

[0150] In this embodiment, an example of optical multicasting will be described in which wavelength multiplexing is used to multiplex optical signals.

[0151] An AWG (Arrayed Waveguide Grating) optical coupler is used in the optical multiplexing unit 51 for wavelength multiplexing of optical signals.

[0152] An optical splitter is used in the first demultiplexing section 52 to split the optical signal at a predetermined power ratio.

[0153] Also, an AWG filter is used in the second demultiplexing unit 53 to demultiplex the optical signal for each wavelength.

[0154] <Switching system operation> In the switching system 50, for example, as shown in FIG. 11, an optical transmitter 13_1 connected to a transmission group A (3_10) and an optical transmitter 13_2 connected to a transmission group B (3_20) each output optical packets of different wavelengths.

[0155] Optical packets of different wavelengths are multiplexed by an AWG optical coupler 51 and are simultaneously transmitted to multiple destination groups 4_10 to 4_40 in the same time slot.

[0156] In this way, optical packets can be sent to many groups, for example, many more end hosts, without increasing the number of ports on the switch.

[0157] Higher multicasting ratios are also possible, with the power budget of the optical link determining the maximum achievable ratio.

[0158] For example, if two optical packets with different wavelengths are each transmitted at a bandwidth of 200 Gb / s, they will be transmitted at twice the bandwidth (400 Gb / s).

[0159] The transmitted optical packet is split into destination groups by an optical splitter 52, and then demultiplexed into wavelengths by an AWG filter 53 in each group (e.g., group 4_40) and transmitted to an end host (e.g., destination hosts 4_41, 4_42).

[0160] Thus, when multicasting is used, optical packets from multiple destination groups arrive at the same destination group simultaneously, so a receiver unit with demultiplexing capabilities is used to process packets from different destination groups, increasing the total number of receiver units in the system.

[0161] In this way, the switching system 50 can improve the expandability of the system by using optical multicasting (optical multiplexing).

[0162] 12 shows an example of a timing chart of the switching system 50. In the switching system 50, one switching period is divided into four time slots, of which the first slot is shown on the left and the second slot is shown on the right.

[0163] Here we have 128 25Gb / s hosts, 16 groups (8 hosts per group), and multicast to 4 groups at a time.

[0164] The switching system 50 uses commercially available transceiver units based on the PAM4 multi-level format and processes a total communication volume of 6.4 Tb / s.

[0165] In the switching system according to the embodiment of the present invention, an example is shown in which the physical layer transmission group (transmission side) and destination group (reception side) are respectively arranged separately on the input side and output side of the optical switch, but this is not limited to this.

[0166] As shown in Figure 13, in a switching system 60, a source group and a destination group may be attached to the input / output ports of the optical switch 14 with the same index as the same physical layer unit (5_10 to 5_m0). In this case, a single ASIC chip is arranged for each group to control all of the switching and data management described above. Here, the ASIC chip 61 has the functions of the control unit 17 and the switching element 41.

[0167] For example, in a typical data link layer protocol, an end processor (host) is interrupted every time a packet arrives in order to apply the protocol procedures to the packet.

[0168] An example of a protocol procedure is to verify that the packet bits arrived correctly (bit checksum), or to remove overhead bits that were added to the main payload being processed.

[0169] In this embodiment, an ASIC chip 61 is attached to each host group and performs processing related to link layer protocols in addition to the switching function.

[0170] This centralized implementation of physical layer switching and higher link layer functions reduces end-to-end latency and power consumption.

[0171] According to the switching system of this embodiment, the expandability of the system can be improved by optical multicasting (optical multiplexing).

[0172] In the embodiment of the present invention, an example has been shown in which wavelength multiplexing is used as the characteristic of light for multiplexing optical signals, but the present invention is not limited to this, and other optical characteristics such as orthogonal polarization and coding may also be used.

[0173] In the embodiments of the present invention, examples of the structure, dimensions, materials, etc. of each component in the configuration and control method of the switching device and switching system are shown, but the present invention is not limited to these examples. Anything that can demonstrate the functions and effects of the switching device and switching system may be used. [Industrial Applicability]

[0174] The present invention relates to a switching device and a switching system for switching packets, and can be applied to computers and optical communication systems. [Explanation of symbols]

[0175] 10 Switching Device 13 Optical transmitter 14 Optical Switch 15 Optical receiver 17 Control Unit

Claims

1. a plurality of optical transmitters that convert input electrical packets with set priorities into optical packets and transmit the optical packets; a plurality of optical receivers that receive and convert the optical packets into electrical packets; an optical switch disposed between the plurality of optical transmitters and the plurality of optical receivers, the optical switch transmitting the optical packet input from the optical transmitter to any one of the plurality of optical receivers; a control unit connected to the optical receiver, the control unit holding the converted electrical packets with a lower priority and transmitting the converted electrical packets with a higher priority first; A switching device comprising:

2. The control unit has an optical data link.

2. The switching device according to claim 1.

3. Optical packets transmitted from the optical transmitter are multiplexed and demultiplexed according to predetermined optical characteristics, and are received by the optical receiver.

2. The switching device according to claim 1.

4. the optical transmitter divides the optical packet by the number of the optical receivers to which the optical packet is transmitted; The optical switch transmits the divided optical packets in the time slots assigned to each of the divided optical packets.

2. The switching device according to claim 1.

5. In turn, multiple sending hosts and A switching element; A switching device according to claim 1; With multiple receiving hosts Equipped with The plurality of sending hosts are classified into a plurality of sending groups; a single switching element for each of the transmission groups; a single optical transmitter is connected to each of the transmission groups; The switching element controls the plurality of sending hosts and interconnects them with the switching device. A switching system comprising:

6. a multiplexing unit disposed between the plurality of optical transmitters and the optical switch, the multiplexing unit multiplexing optical packets output from the plurality of optical transmitters; a first demultiplexing unit disposed in sequence between the optical switch and the plurality of optical receivers, for demultiplexing an optical packet output from the optical switch; a second demultiplexing unit that selects and demultiplexes the branched optical packets in accordance with predetermined optical characteristics and outputs the demultiplexed packets to each of the plurality of receiving hosts; The switching system of claim 5 , comprising:

7. the sending host; the switching element; the optical transmitter; the optical receiver; the control unit; The receiving host is provided in the same unit.

6. The switching system according to claim 5.

8. the switching element; the control unit; Higher link layer functions are implemented centrally 8. The switching system according to claim 7.

Images