Switching device and switching method

Abstract

The switching device (10) of the present invention comprises, in order, a plurality of input ports (11) into which a plurality of electrical packets are respectively input, an input block (12) that performs low-radix switching on the electrical packets, a plurality of optical transmitters (13) that convert the electrical packets output from the input block into optical packets that are divided into a number equal to the number of ports and transmit them, an optical switch (14) that transmits the divided optical packets in time slots assigned to each of the divided optical packets, a plurality of optical receivers (15) that convert the optical packets output from the optical switch into electrical packets and transmit them, and a plurality of output ports (16) that output the electrical packets output from each optical receiver. As a result, the present invention can provide a high-speed, low-power-consumption switching device.

Description

[Technical Field]

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

[0002] As information communication becomes larger and faster, it becomes necessary to switch large amounts of communication data in order to achieve end-to-end connectivity over a wide area.

[0003] Packet switching is widely adopted as a technology for network environments such as large-scale data center networks. ASIC chips are implemented as the electrical packet switches that make up these networks.

[0004] In an ASIC switch, as shown in Figure 8, the total power consumption increases as the switch bandwidth, i.e., the switching throughput (processing capacity), increases. Air-cooling and water-cooling are used to dissipate heat from the chips in the ASIC switch. Arrows 81 and 82 in the figure indicate the air-cooling limit and water-cooling limit in terms of power consumption, respectively.

[0005] In addition, in optical communication networks, optical-electrical interfaces are implemented at the input and output ports of switches in order to switch optical packets. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Zilberman, Noa, Gabi Bracha, and Golan Schzukin. "Stardust: Divide and conquer in the data center network." 16th USENIX Symposium on Networked Systems Design and Implementation (NSDI 19). 2019. Summary of the Invention [Problem to be solved by the invention]

[0007] However, in conventional packet switches, the implementation of an optical-electrical interface increases the chip area, making it difficult to increase the throughput (processing capacity) of the switch without changing the chip area.

[0008] As described above, conventional packet switches have had problems such as high power density due to the constraints of ASIC chip area, and problems due to the implementation of optical-electrical interfaces.

[0009] Furthermore, when a conventional packet switch performs non-blocking processing, a data packet input to an input port is switched to a desired output port. When multiple packets are simultaneously transmitted to the same output port, contention occurs, and arbitration is performed for the packets under collision.

[0010] In arbitration, using centralized information such as desired output port and priority, the highest priority packets are selected for transmission first, while other packets are buffered and transmitted subsequently.

[0011] However, with this type of packet switch, as the number of ports in the switch and the data rate per port increase, controlling and scheduling the traffic handled by the switch becomes more complex and time-consuming.

[0012] For example, in the fastest scenario of switching packets in a cut-through fashion, an ASIC switch with a throughput of 6 Tb / s takes about 400 nsec or more, resulting in increased latency. Furthermore, this latency increases due to packet collisions. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, the switching device of the present invention comprises, in order, a plurality of input ports into which a plurality of electrical packets are respectively input, an input block that performs low-radix switching on the electrical packets, a plurality of optical transmitters that convert the electrical packets output from the input block into optical packets that are divided into a number equal to the number of ports and transmit them, an optical switch that transmits the divided optical packets in time slots assigned to each of the divided optical packets, a plurality of optical receivers that convert the optical packets output from the optical switch into electrical packets and transmit them, and a plurality of output ports that output the electrical packets output from each of the optical receivers.

[0014] In addition, the switching method according to the present invention includes the steps of an input block performing low-radix switching on input electrical packets, a plurality of optical transmitters converting the electrical packets output from the input block into optical packets divided into a number equal to the number of ports and transmitting the optical packets, an optical switch transmitting the divided optical packets in time slots assigned to each of the divided optical packets, and an optical receiver converting the optical packets input from the optical switch into electrical packets and transmitting the electrical packets. [Effects of the Invention]

[0015] According to the present invention, a high-speed, low-power-consumption switching device and switching method can be provided. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a block diagram showing the configuration of a switching system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining the operation of the switching system according to the first embodiment of the present invention. [Figure 3A]FIG. 3A is a diagram for explaining the operation of the switching system according to the first embodiment of the present invention. [Figure 3B] FIG. 3B is a diagram for explaining the operation of the switching system according to the first embodiment of the present invention. [Figure 3C] FIG. 3C is a diagram for explaining the operation of the switching system according to the first exemplary embodiment of the present invention. [Figure 3D] FIG. 3D is a diagram for explaining the operation of the switching system according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram for explaining the operation of the switching system according to the modified example of the first embodiment of the present invention. [Figure 5] FIG. 5 is a block diagram showing the configuration of a switching system according to the second embodiment of the present invention. [Figure 6] FIG. 6 is a diagram for explaining the operation of the switching system according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a diagram for explaining the operation of the switching system according to the first embodiment of the present invention. [Figure 8] FIG. 8 is a diagram for explaining the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0017] First Embodiment A switching device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3D.

[0018] <Switching device configuration> As shown in FIG. 1, the switching device (packet switch) 10 according to this embodiment comprises, 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.

[0019] The input block 12 is an electronic switching unit, a low-radix switching block (chiplet).

[0020] The input port 11 of the packet switch 10 is branched into m groups, and each group is connected to an input block 12 .

[0021] The input block 12 processes the incoming packets.

[0022] The optical transmitter 13 converts the electrical signal output from the input block 12 into an optical signal and outputs it.

[0023] The optical switch 14 cross-connects each group of input blocks 12 and output ports 16 based on a time slot operation (described below).

[0024] The optical receiver 15 converts the optical signal output from the optical switch 14 into an electrical signal.

[0025] The output ports 16 of the packet switch 10 are each divided into m virtual groups.

[0026] In the packet switch 10, the same blocks are connected one by one to each group of different output ports 16 in order, and each is connected by a time slot (described later), where T is the duration of the packet input to the packet switch 10.

[0027] Here, the time slot is Δt=T / m.

[0028] Also, the same output port 16 of an input block 12 always connects to the same output port 16 of a virtual group, where both ports have the same index within the port group.

[0029] <Switching device operation> The operation of the switching device (packet switch) 10 according to this embodiment will be described with reference to FIG.

[0030] 2 shows the basic operation of a packet switch 10 that performs non-blocking processing, using a 4x4 switch as an example. This packet switch 10 operates based on time slot operation, which will be explained below.

[0031] 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.

[0032] 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.

[0033] In the packet switch 10, 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.

[0034] 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.

[0035] In this way, an input packet of light 2 is generated that satisfies these conditions.

[0036] 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.

[0037] Each time slot has a duration Δt of T / 4.

[0038] 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).

[0039] Finally, the packets are converted into electrical packets by the optical receiver 15 and output at a fixed duration from the packet switch 10. In other words, the data rate of the signal output from the packet switch 10 is the same as the data rate of the signal input thereto.

[0040] 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.

[0041] The switching operation of the optical switch 14 described above will be described with reference to Figures 3A to 3D. Each of Figures 3A to 3D shows an example of a series of switching operations in steps S1 to S4.

[0042] Packets are input to each of the four ports 11_1 to 11_4 in the packet switch 10. The packet input to the port 11_3 (packet C) has the desired output port as the port 16_3 and has the highest priority.

[0043] 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.

[0044] 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.

[0045] 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. 3A).

[0046] 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. 3B). Here, packets A and D are transmitted to different output ports, so no collision occurs.

[0047] 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. 3C).

[0048] 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. 3D).

[0049] 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.

[0050] 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.

[0051] In this switching operation, in every step, each output port 16 is connected to only one input port 11, as shown in Figures 3A to 3D. 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 (exact) time slot (with a divided duration).

[0052] Additionally, the optical receiver 15 in the packet switch 10 can operate in response to such burst mode transmission.

[0053] The packet switch 10 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. 3A) to another switch mode (e.g., FIG. 3B) is very short compared to the duration of the input packet.

[0054] 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.

[0055] Also, if a short guard time is set between packets entering the same input port 11 to avoid data loss during switching, this guard time is less than 1 / 10 of the duration of the input packet. The transition time is short enough to be accommodated within the guard time.

[0056] <Effects> The effects of the switching device (packet switch) 10 according to this embodiment will be described below.

[0057] In a typical electrical switch, an incoming packet passes through an input port of the switch, where it is first inspected for destination and priority, followed by a centralized arbitration to determine which packet should be sent first among all packets destined for the same output port.

[0058] The implementation of a centralized arbitration process becomes more complex as the number of switch ports and throughput increases, resulting in increased communication latency and power consumption.

[0059] On the other hand, the switching device (packet switch) according to this embodiment can switch packets without performing centralized arbitration, which takes a long time, and therefore can reduce communication latency and power consumption.

[0060] Furthermore, because part of the switching process is handled by an optical switch, it is possible to increase the switching capacity with lower power consumption than an ASIC using CMOS transistors.

[0061] 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.

[0062] It also avoids contention between ports in the same block, allowing non-blocking processing.

[0063] <Modification> A switching device according to a modified example of the first embodiment of the present invention will be described with reference to Fig. 4. The configuration of a switching device (packet switch) 10_2 according to this modified example is similar to that of the first embodiment.

[0064] <Switching device operation> The operation of the switching device (packet switch) 10_2 according to this modification will be described below.

[0065] In the packet switch 10_2, packets (packets A to D) are input to four ports 11_1 to 11_4, respectively. The packets A to D have the same desired output port (16_2), and the packets B, A, D, and C are prioritized in this order.

[0066] 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).

[0067] Next, since packet A has the second priority, it is transmitted to the output port 16_2 for the duration of the second time slot (step S2).

[0068] 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).

[0069] 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).

[0070] 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.

[0071] In this way, in the packet switch 10_2, all input packets transmitted to the same output port are correctly (accurately) switched to that port at time T.

[0072] <Effects> The switching device (packet switch) 10_2 according to this modification has the following effects in addition to the effects of the first embodiment.

[0073] In order to send multiple packets simultaneously to the same destination using a conventional packet switch, the same number of parallel optical receivers as the number of packets was required.

[0074] In the packet switch 10_2, a compact copy of each input packet is created at a high data rate, and the compact packets are divided into short time slots and transmitted. In this way, transmission of packets to the same destination can be performed in a time shorter than the actual packet input interval using time interleaving.

[0075] According to the switching device (packet switch) of this modified example, packets can be sent to the same output port without performing centralized arbitration, which takes a long time, and therefore communication latency can be reduced, and power consumption can be reduced.

[0076] <Second embodiment> A switching device according to a second embodiment of the present invention will be described with reference to FIG.

[0077] <Switching device configuration>

[0078] A switching device (packet switch) 20 according to this embodiment includes an optical multiplexing unit 21 after the optical transmitter 13, and an optical demultiplexing unit 22 before the optical receiver 15. Also, a receiving queue 23 after the optical receiver 15. The other configurations are the same as those of the first embodiment.

[0079] This allows the total amount of communication that the packet switch 20 can handle to be increased.

[0080] For example, when an optical wavelength multiplexing technique is used as the optical multiplexing technique, a multiplexer is used for the optical multiplexing unit 21, and an optical demultiplexer is used for the optical demultiplexing unit 22.

[0081] A multiplexer 21 is connected as an optical multiplexing section to a plurality of optical transmitters 13 that transmit optical packets at different wavelengths.

[0082] On the other hand, a demultiplexer 22 is connected as an optical separation unit after the optical switch 14, and demultiplexes the multi-wavelength optical packet and outputs each wavelength to an optical receiver 15 at the subsequent stage.

[0083] A receiving queue 23 is connected to the rear of the optical receiver 15, stores the output of the optical receiver 15, and outputs it sequentially.

[0084] Furthermore, for example, when optical orthogonal frequency division multiplexing (OFDM) technology is used as the optical multiplexing technology, a multiplexer 21 is used in the optical multiplexing section, and a demultiplexing circuit 23 is used in the optical demultiplexing section.

[0085] A multiplexer 21 is connected as an optical multiplexing section to a plurality of optical transmitters 13 that transmit phase-modulated optical packets.

[0086] On the other hand, a demultiplexing circuit 23 is connected as an optical demultiplexing unit after the optical switch 14, and demultiplexes the polarization-multiplexed optical packets and outputs them to the optical receiver 15 at the subsequent stage for each phase (polarization).

[0087] A receiving queue is connected to the rear of the optical receiver 15, stores the output of the optical receiver 15, and outputs it sequentially.

[0088] <First Example> A switching device according to a first embodiment of the present invention will be described with reference to FIG.

[0089] As an example of a switching device (packet switch) 20_1 according to this embodiment, as shown in Fig. 6, a block 12 has two output ports 12_1 and 12_2. One is a first port 12_1 and the other is a second port 12_2. The other configuration is the same as that of the second embodiment.

[0090] Through the optical switch 14, the block 12 is connected to only one port 16_1 of the output ports 16_1 to 16_4 at a time, and subsequently connected to the next port in a cyclical order. A packet output from the first port 12_1 of the block 12 is connected to the first port 16_1_1 of the output port 16_1, and similarly, a packet output from the second port 12_2 of the block 12 is connected to the second port 16_1_2 of the output port 16_1.

[0091] According to the one-to-one port mapping, switching is performed only by the input groups and no switching is required at the output ports, where the mapping automatically splits the different wavelengths to the desired output ports 16 by the demultiplexers (optical filters) 22.

[0092] In the packet switch 20_1, the optical switch 14 is configured as a 4x4 switch. Packets passing through each port of the optical switch 14 are multiplexed and transmitted simultaneously, so that the total number of ports of the switching system is doubled to 8x8.

[0093] In this way, the switching device (packet switch) according to this embodiment has excellent scalability and can realize a large-scale switch without increasing latency.

[0094] In the switching device (packet switch) according to this embodiment, as shown in FIG. 7, the switching function may be implemented by a virtual queue 24 within an input group.

[0095] In embodiments of the present invention, optical switching and optical multicasting may be combined, thereby increasing the number of switching ports and the total communication volume.

[0096] In an embodiment of the present invention, signals output from different ports of an input block may be compressed together in adjacent sub-bands of the optical signal by a digital signal processing (DSP), where a DSP-based receiving unit may be used at the output port to decompress these signals and transmit them directly to the corresponding output port.

[0097] In the embodiment of the present invention, examples of the structure and dimensions of each component in the configuration and operation of the switching device are shown, but the present invention is not limited to these examples. Any structure and dimensions may be used as long as the switching device can function and produce the desired effect. [Industrial Applicability]

[0098] The present invention relates to a switching device and a switching method for processing packets, and can be applied to information communication systems. [Explanation of symbols]

[0099] 10 Switching Device 11 Input Ports 12 Input Blocks 13 Optical transmitter 14 Optical Switch 15 Optical receiver 16 output ports

Claims

1. a plurality of input ports to which a plurality of electrical packets are respectively input; an input block that performs low-radix switching on the electrical packets; a plurality of optical transmitters that convert electrical packets output from the input block into optical packets that are divided into a number equal to the number of ports and transmit the optical packets; an optical switch that transmits the divided optical packets in time slots assigned to the divided optical packets; a plurality of optical receivers that convert optical packets output from the optical switch into electrical packets and transmit the electrical packets; a plurality of output ports for outputting electrical packets output from each of the optical receivers; A switching device comprising:

2. The output ports to which the plurality of electrical packets are to be transmitted are set, The optical switch transmits the divided optical packets toward the set output ports.

2. The switching device according to claim 1.

3. The set output port is the same for the plurality of electrical packets.

3. The switching device according to claim 2.

4. The output port to which the electrical packet is to be sent is set in the electrical packet; The optical switch transmits the divided optical packets toward the set output ports.

2. The switching device according to claim 1.

5. an optical multiplexing unit disposed between the optical transmitter and the optical switch; an optical separator disposed between the optical switch and the optical receiver; The switching device of claim 1 .

6. Arbitration is performed only on the input block 2. The switching device according to claim 1.

7. The electrical packets output from the input block are digitally processed.

2. The switching device according to claim 1.

8. an input block performing low-radix switching on the input electrical packet; a step in which a plurality of optical transmitters convert the electrical packets output from the input block into optical packets divided into a number equal to the number of ports and transmit the optical packets; an optical switch transmitting the divided optical packets in time slots assigned to the divided optical packets; an optical receiver converting the optical packet input from the optical switch into an electrical packet and transmitting the electrical packet; A switching method comprising:

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