WO2024038541A1 - Switching apparatus and switching system - Google Patents

Switching apparatus and switching system Download PDF

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Publication number
WO2024038541A1
WO2024038541A1 PCT/JP2022/031220 JP2022031220W WO2024038541A1 WO 2024038541 A1 WO2024038541 A1 WO 2024038541A1 JP 2022031220 W JP2022031220 W JP 2022031220W WO 2024038541 A1 WO2024038541 A1 WO 2024038541A1
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WO
WIPO (PCT)
Prior art keywords
optical
packet
packets
switching
switch
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PCT/JP2022/031220
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French (fr)
Inventor
Ibrahim Salah
Toshikazu Hashimoto
Norio Sato
Takeshi Sakamoto
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Nippon Telegraph And Telephone Corporation
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Priority to PCT/JP2022/031220 priority Critical patent/WO2024038541A1/en
Publication of WO2024038541A1 publication Critical patent/WO2024038541A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/66—Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L49/00—Packet switching elements
    • H04L49/10—Packet switching elements characterised by the switching fabric construction
    • H04L49/111—Switch interfaces, e.g. port details
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L49/00—Packet switching elements
    • H04L49/15—Interconnection of switching modules
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L49/00—Packet switching elements
    • H04L49/30—Peripheral units, e.g. input or output ports

Definitions

  • the present invention relates to a switching apparatus and a switching system, each of which switches a packet.
  • a switching system 70 is connected to a plurality of hosts (a CPU, a GPC, an accelerator, and the like) 72 via an input/output interface 71 and to a memory 73.
  • hosts a CPU, a GPC, an accelerator, and the like
  • bit rate of a signal generated by a host is greatly increased.
  • an electrical signal can reach within a limited distance of about several cm.
  • an optical link is necessary.
  • a packet switching module is an ASIC switch and processes only an electrical signal. For this reason, optical/electric/optical conversion is required in a switch for the optical signal of the optical link.
  • a packet switch In a packet switch, if 128 hosts having units each of which generate, for example, a 25 Gb/s-data packet are assumed, a 6.4-TB/s switch throughput is necessary. If an arrangement (arrangement using optical/electric/optical conversion) using an ASIC switch is implemented to achieve this throughput, the following problem is posed.
  • an ASIC switch of this scale exhibits latency of 400 nsec or more for the fastest scenario having a cut through packet.
  • a high latency occurs in an input signal.
  • a long latency undesirably occurs until the completion of reception.
  • the power consumption of the ASIC switch is high, and the power is concentrated in a narrow chip area. As a measure against heat generated by this high power density almost, air cooling almost reaches the limit, and water cooling is necessary.
  • the mounting area of the optical-electronic interface of the switch is undesirably increased. Furthermore, the energy density per unit area increases to increase the power consumption.
  • a switching apparatus includes a plurality of optical transmitters each configured to convert an input electric packet in which a priority is set into an optical packet and transmit the optical packet, a plurality of optical receivers each configured to receive the optical packet and convert the optical packet into an electric packet, an optical switch arranged between the plurality of optical transmitters and the plurality of optical receivers and configured to transmit the optical packet input from the optical transmitter to any one of the plurality of optical receivers, and a control unit arranged to be connected to the optical receiver and configured to hold the converted electric packet having a low priority, and transmit the converted electric packet having a high priority first.
  • a switching apparatus and a switching system each of which reduces the latency and the power consumption.
  • Fig.1 is a block diagram showing the arrangement of a switching apparatus according to the first embodiment of the present invention
  • Fig.2A is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention
  • Fig.2B is a view for explaining the operation of a conventional switching apparatus
  • Fig.3A is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention
  • Fig.3B is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention
  • Fig.3C is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention
  • Fig.4 is a view for explaining the operation of a conventional switching apparatus
  • Fig.5 is a is a block diagram showing the arrangement of a switching apparatus according to the second embodiment of the present invention
  • Fig.6 is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention
  • Fig.7A is a view for explaining the operation of the
  • a switching apparatus 10 As shown in Fig. 1, a switching apparatus 10 according to this embodiment includes optical transmitters 13, an optical switch 14, optical receivers 15, and control units 17.
  • a packet 1 is transmitted from a transmission host 3, and the optical transmitter 13 compresses and demultiplexes the packet 1 into packets (packets 2).
  • the optical switch 14 switches the packet, and the packet 1 is received by a reception host 4 via the optical receiver 15.
  • the packets 1 transmitted from the transmission host 3 are set with priorities.
  • the optical switch 14 simultaneously transmits all packets for the same output port destination.
  • the destination output port simultaneously receives different packets.
  • the control unit 17 is an electric chip and arranged while being connected to the optical receiver 15.
  • the control unit 17 executes processing such as arbitration for the packets 2 output from the optical switch 14.
  • the control unit 17 is locally assigned for each reception host 4 and executes self management of traffic input to the reception host 4.
  • the control unit 17 is arranged adjacent to the reception host 4 and quickly updates the data acquisition priority.
  • control unit 17 manages communication processing of the single reception host 4, thereby performing a high-speed operation.
  • An information channel is connected to the reception host 4 and the control unit 17 in addition to a data link.
  • FIG. 2A shows packet processing in the switching apparatus 10.
  • Fig. 2B shows a conventional non-blocking switch 20.
  • the bandwidths of all the output ports are constant.
  • the switch 20 can transmit only one packet at one time. For example, if a flow B (101_2) and a flow C (101_3) are transmitted to the same output port, these flows are processed in a single band having a predetermined bandwidth (Fig. 2B).
  • the bandwidth of any output port is variable, and all the packets input to the switch can be adjusted.
  • the bandwidth is changed to process the packet in two bands.
  • the bandwidth of the output port is 1/2 of the total throughput (bandwidth) of the switch.
  • the optical switch 14 can cope with a high bandwidth per output port.
  • data (packet B) 102_2 having a high priority is transmitted first.
  • Input data (packet C) 102_3 having a low priority is transmitted after the completion of the transmission of the data (packet B) 102_2 having a high priority.
  • an optical data link may be arranged in the control unit 17. Accordingly, optical data can be directly transmitted between the output port of the switch and the reception host 4 capable of processing the optical input signal.
  • the optical switch 14 can be arranged based on a broadcast-and-select method.
  • Signals input to different switch ports are multiplexed for, for example, the respective wavelengths.
  • the input signals are respectively transmitted to all the output ports and selected in the respective output ports based on a desired signal transmission destination.
  • an input packet 1_1 from a transmission host A (3_1) is demultiplexed by a splitter 18, and demultiplexed packets 2_1 to 2_4 are transmitted to reception hosts 4_1 to 4_4.
  • the input packet 1_1 and an input packet 1_4 from the transmission host A (3_1) and a transmission host D (3_4) are demultiplexed by the splitter 18.
  • the demultiplexed packets 2_1 to 2_4 are selected by an optical selection filter 19 in the output port and transmitted to the reception hosts 4_1 to 4_4.
  • a fast tunable filter or a polarization filter element can be used as the optical selection filter 19.
  • the input packets 1_1 and 1_4 from the transmission hosts A and D (3_1 and 3_4) are demultiplexed by the splitter 18.
  • the demultiplexed packets 2_1 to 2_4 are received by the plurality of optical receivers 15 for the respective packets and transmitted to the reception hosts 4_1 to 4_4.
  • contention occurs, and arbitration is executed for the colliding packets.
  • arbitration a packet having a high priority is first selected and transmitted, and other packets are buffered and subsequentially transmitted.
  • arbitration is required in scheduling performed when simultaneously transmitting the packets to the same destination.
  • the reception host 4 is assigned with a computational task for reducing the two data flows, that is, a flow A (201_1) and the flow B (201_2).
  • the host 4 has already processed the flow A (201_1) and waits for the reception of the flow B (201_2).
  • the flow C is another flow to be transmitted to the host 4 and reaches the switch before the arrival of the flow B with a time difference. If the time difference is more than zero, the switch transmits the flow C to the host 4.
  • arbitration of the packet is started between the flow C (201_3) and the flow B (201_2) when the flow B (201_2) arrives.
  • a priority is given to the flow B (201_2). If a failure or delay occurs in the arbitrator 22 notified of a request of the host 4 using the flow B (201_2) as the highest destination, the flow B (201_2) is not sufficiently quickly switched even if the time difference is equal to zero.
  • the host 4 is a processing unit, and the data acquisition priority changes at high speed. In this case, it is difficult to continuously update the arbitrator 22 with the changing priority. Accordingly, in the processing of all the system communication amount, it is difficult for the arbitrator 22 to sufficiently quickly and accurately perform determination for a very large amount of dynamic data.
  • arbitration is executed by the control unit 17 on the output side in accordance with the distributed control method.
  • the host 4 connected to each output port determines a packet to be processed first.
  • the control unit 17 can locally execute arbitration for each host.
  • the data rate of the packets reaching the same output port in different slots is converted into the initial (original) data rate.
  • the packets are output in an order requested to the connected output host. In this manner, the minimum latency is given to the packet having the highest priority.
  • the latency and power consumption in switching can be reduced, and the load for acquiring information necessary for the arbitration process can be reduced (eliminated).
  • an example of a switching apparatus (packet switch) 30 includes input ports 11, input blocks 12, optical transmitters 13, an optical switch 14, optical receivers 15, and output ports 16.
  • the switching apparatus 30 also includes control units 17 connected to the optical receivers 15.
  • the optical switch 14 is operated in the time slot operation.
  • Fig. 6 shows an example of the basic operation of the packet switch 30 for executing non-block processing using a 4 x 4 switch. This packet switch 30 is based on the time slot operation to be described below.
  • a packet is switched for each input group.
  • arbitration is executed within the input packet of the same input group. Since this arbitration is executed for the small number of ports and a low communication amount, the operation can be executed fast without requiring a long time.
  • An electric packet 1 input to the switch has a bandwidth BW (bit/sec) and a duration T.
  • the desired output port 16 to which the packet is transmitted is set.
  • a packet switching operation to any one of the four output ports 16 is complete within the time T. This is because if a time of T or longer is required for the switching of a single packet, the next input packet is blocked and a continuous switching delay is accumulated.
  • the optical transmitter 13 compresses the input packet 1 by a factor (in this case, 4) equal in number to the number of ports (that is, the number of optical receivers to which packets are transmitted). That is, the duration of the input packet is divided by a factor equal in number of the number of ports and becomes T/4. In addition, the bandwidth is multiplied by the same factor and becomes 4BW in order to retain the packet data contents.
  • a factor in this case, 4
  • an optical input packet 2 is generated by satisfying the above conditions.
  • the optical switch 14 distributes the respective optical input packets 2 to the desired output ports 16 using periodic time slots.
  • the periodic operation of the switch is divided into four time slots.
  • the distribution (switching) of the optical input packets 2 is repeatedly executed for each time slot in accordance with a sequence formed by steps S1 to S4 (to be described later).
  • the optical receiver 15 converts the packet into an electric packet, and the packet switch 30 outputs the electric packet in a predetermined duration.
  • the data rate of the signal output from the packet switch 30 is equal to the data rate of the input signal.
  • the data rate is changed to the first data rate. This change is performed in the arrival order of packets.
  • the priority of the change may be set by another arbitration.
  • Figs. 7A to 7D show examples of a series of switching operations in steps S1 to S4, respectively.
  • packets are input to four ports 11_1 to 11_4, respectively.
  • the packet (packet C) input to the port 11_3 has the desired output port as a port 16_3 and has the highest priority.
  • the packets (packets A and D) input to ports 11_1 and 11_4 have the desired ports as ports 16_2 and 16_1, respectively, and have the second highest priority.
  • the packet (packet B) input to the port 11_2 has the desired output port as a port 16_4 and has the third highest priority.
  • the packet C since the packet C has the highest priority, the packet C is transmitted to the output port 16_3 in a duration of the first time slot (step S1 and Fig. 7A).
  • the packets A and D Since the packets A and D have the second highest priority, they are simultaneously transmitted to the output ports 16_2 and 16_1 in a duration of the second time slot (step S2 and Fig. 7B). In this case, since the packets A and D are transmitted to different output ports, no collision occurs.
  • the packet (packet B) input to the port B has the third highest priority, it is transferred to the output port 16_4 in a duration of the third time slot (step S3 and Fig. 7C).
  • step 3 since transmission of the packets A to D is complete in the previous step (step 3), switching is not executed in a duration of the fourth time slot (step S4 and Fig. 7D).
  • the respective output ports 16 are connected to only one input port 11.
  • the input port 11 is connected to the desired output port 16.
  • the packet is arranged in a correct (accurate) time slot (the divided duration).
  • optical switch 14 is operated, as shown in Fig. 8.
  • packets 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 are prioritized in the order of the packets B, A, D, and C.
  • the packet B since the packet B has the highest priority, the packet B is transmitted to the output port 16_2 in a duration of the first time slot (step S1).
  • the packet A since the packet A has the second highest priority, the packet A is transmitted to the output port 16_2 in a duration of the second time slot (step S2).
  • the packet D since the packet D has the third highest priority, the packet D is transmitted to the output port 16_2 in a duration of the third time slot (step S3).
  • the packet C since the packet C has the fourth highest priority, the packet C is transmitted to the output port 16_2 in a duration of the fourth time slot (step S4).
  • the optical switch 14 can process a large number of dynamic data sufficiently at high speed due to the introduction of time slots and an increase in bit rate without decreasing the signal output level along with an increase in the number of ports and without increasing the constituent units, thereby reducing power consumption.
  • the arbitration by the conventional concentrated control method is distributed into the following steps, and the arbitration is executed.
  • the optical switch 14 transmits the packets of different input groups to the same output group in different time slots.
  • the optical switch 14 can execute this step at a high data rate with accurate time control.
  • arbitration is executed by the control unit 17 on the output side in accordance with the distributed control method.
  • the host 4 connected to each output port determines a packet to be processed first.
  • the control unit 17 can locally execute arbitration for each host.
  • the data rate of the packets reaching the same output port in different slots is converted into the initial (original) data rate.
  • the packets are output in an order requested to the connected output host. In this manner, the minimum latency is given to the packet having the highest priority.
  • the latency and power consumption in switching can be reduced, and the load for acquiring information necessary for the arbitration process can be reduced (eliminated).
  • Fig. 9A shows the mode of latency in a flow switched by the switching apparatus 30.
  • Fig. 9B shows the mode of latency in a flow switched by the conventional non-blocking switch 20.
  • the delay time is increased, and the latency is increased.
  • the switching apparatus 30 has a short delay time, so that the latency can be reduced.
  • an input packet passes through the input port of the switch. First, the destination and the priority are examined, and then concentrated arbitrary is executed. The first packet to be transmitted is determined from all the packets having the same output port destination.
  • Concentrated arbitration processing becomes complicated with an increase in the number of switch ports and the throughput. As a result, the communication latency is increased, and the power consumption is increased.
  • the switching apparatus 30 since the packet can be switched without executing the concentrated arbitration requiring a long time, the communication latency is reduced, and the power consumption can be reduced.
  • the optical switch 14 performs part of the switching processing, the power consumption is lower than that of the ASIC formed by a CMOS transistor, and the switching capacity can be increased.
  • the area occupied by the input block 12 can be reduced.
  • the total area of the packet switch (chip) is not increased. Accordingly, the optical-electric interface is mounted, and the throughput (processing capacity) of the switch can be increased without changing the chip area.
  • the power consumption can be reduced by using the chiplet.
  • the contention between the ports of the same block can be prevented, and non-blocking processing can be executed.
  • compact copies of the input packets are created at a high rate and divided and transmitted in short time slots.
  • transmission of the packets to the same destination can be processed within a short time as compared with the actual packet input interval by using time interleaving.
  • the optical receiver 15 using the switching apparatus 30 can be operated in correspondence with this burst mode transmission.
  • the switching apparatus 30 is formed by four 1 x 4 switching units corresponding to the different input ports 11 to easily implement a high-speed 4 x 4 optical switch device.
  • the time (transition time) for transitioning one switch mode (for example, Fig. 7A) to another switch mode (for example, Fig. 7B) is very short as compared with the duration of the input packet.
  • the transition time can be reduced to 10 psec in an actually usable technique. This transition time is very short as compared with a 100-Gb/s Ethernet packet having a duration of 120 nsec.
  • a short guard time may be provided between the optical packets to prevent all data losses between switching operations.
  • the bandwidth of the packet generated by the host is multiplied by a coefficient F (switch port count). For example, in an 8 x 8 switch, a 25-Gb/s electric packet must be converted into a 200-Gb/s optical packet. This optical packet is generated by using a direct modulation laser and a multilevel modulation format.
  • this embodiment since a distance between hosts assumed in this embodiment is short, this embodiment is applicable to a high data rate. In addition, the optical dispersion effect has a negligible level.
  • a packet having a high bit rate may be generated by another method.
  • this switch may be used as a core switching unit in a hybrid switching architecture.
  • the switching system 40 can be scaled by grouping hosts.
  • the switching system 40 includes a plurality of transmission (source) groups 3_10 to 3_40 on the transmission side.
  • Each transmission group includes a plurality of transmission hosts (for example, 3_11 and 3_12) and a switching element 41.
  • a plurality of destination groups (for example, 4_20 and the like) are provided on the reception side.
  • Each destination group includes an optical receiver 15, a control unit 17, a reception-side switch 43, and a plurality of reception hosts (for example, 4_21, 4_22, and the like). Other arrangements are the same as in the first embodiment.
  • the switching element 41 is a low-radix ASIC switch chip.
  • the optical switch 14 has an operation period divided into four input/output ports and four time slots. In this case, not each host unit, but the groups 3_10 to 3_40 of the transmission host are connected to the ports of the optical switch 14.
  • the ASIC switch 41 and two hosts A1 and A2 are arranged to be adjacent to each other.
  • the ASIC switch 41 and the two hosts 3_11 and 3_12 are electrically linked at a short distance.
  • the number of host units per group is preferably about 10.
  • the transmission 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.
  • the hosts of the same group exchange the packets using an ASIC switch 41.
  • the ASIC switch 41 of the group A (3_10) is used to interconnect the hosts A1 and A2 (3_11 and 3_12).
  • Packets between hosts of different groups (to be referred to as an inter-group packets hereinafter) are exchanged via the interconnection with the optical switch 14.
  • the groups of the respective destinations (outputs) are connected to only one transmission (input) group in all the time slots.
  • Switching of the inter-group packets of the transmission group is processed by arranging packets (optical packets of the shortened duration) within the accurate time slots. In each time slot, the transmission group is connected to the desired destination group.
  • end-to-end transmission of the inter-group packet from the transmission host to the destination host is formed by the following three steps.
  • queues G1 to G4 (42_1 to 42_4) correspond to the destination groups 4_10 to 4_20.
  • the packets from the hosts A1 and A2 are transmitted in a bandwidth twice 25 Gb/s.
  • optical switching is executed for the packets (optical packets of the shortened duration) transmitted to the desired destination group.
  • a packet is demultiplexed into four packets and compressed four times.
  • the demultiplexed packets are assigned to the first time slot to the fourth time slot in the time T and transmitted in the bandwidth of 200 Gb/s.
  • the packets are transmitted from the corresponding queue in the ASIC switch 41 to the respective optical switches 14.
  • the hosts of the same group simultaneously generate packets to be transmitted to the same group.
  • these simultaneous packets are adjusted in the identical time slots of the optical switch 14. This can be achieved by the bandwidth of the optical transmitter 13.
  • packets of the different transmission hosts need not be demultiplexed using different wavelengths. Note that if a WDM-based transmitter is used, the request of the high bandwidth along with an increase in the number of host units per group can be satisfied.
  • the packet can reach the desired destination group. For example, all the 25-Gb/s packets can be received in the time T.
  • the plurality of packets are simultaneously transmitted to the same end host, and a packet having a high priority is processed first.
  • the self management of the input data packet as described previously is executed for the local ASIC switch 41 to which data reception is assigned.
  • arbitration by the conventional concentrated control method is executed by distributing the arbitration by the following three steps.
  • the input ports of the switching system 40 are divided into groups (for example, 3_10 to 3_40), and the packets of each group are processed independently of the remaining packets.
  • the output groups of the same destination which are simultaneously input are processed as those of the same group in the input group and are transmitted without executing arbitration. In this manner, since the input ports are grouped into small groups, this step can be performed at high speed.
  • the processing step of the optical switch is executed.
  • the arbitration step is executed.
  • the latency and power consumption in switching can be reduced, and the load for acquiring information necessary for the arbitration process can be reduced (eliminated).
  • the hosts are grouped to increase the number of interconnected hosts, and scalability of the system can be improved.
  • the switching system 50 is scaled by optical multicasting (optical multiplexing).
  • a switching system 50 includes an optical multiplexer 51 between an optical transmitter 13 and an optical switch 14.
  • the switching system 50 also includes a first optical demultiplexer 52 and a second optical demultiplexer 53 between the optical switch 14 and the optical receiver 15.
  • Other arrangements are the same as in the third embodiment.
  • the plurality of optical transmitters 13 are connected to the optical multiplexer 51.
  • the output port of the optical switch 14 is connected to the fist optical demultiplexer 52, and the second optical demultiplexer 53 is connected to the output portion of the first optical demultiplexer 52.
  • This embodiment illustrates an example using wavelength multiplexing of an optical signal as an example of optical multicasting.
  • an AWG Arrayed Waveguide Grating optical coupler
  • an optical splitter is used in the first optical demultiplexer 52 and demultiplexes an optical signal at a predetermined power ratio.
  • An AWG filter is used in the second optical demultiplexer 53 and optically demultiplexes an optical signal for each wavelength.
  • 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) output optical packets having different wavelengths, respectively.
  • optical packets having different wavelengths are multiplexed by the AWG optical coupler 51 and simultaneously transmitted to a plurality of destination groups 4_10 to 4_40 in the same time slot.
  • the optical packets can be transmitted to a large number of groups, for example, a large number of end hosts without increasing the number of ports of the switch.
  • a higher multicasting ratio can be implemented, and the maximum achievable ratio can be determined by the power budget of the optical link.
  • the packets can be transmitted in a two-fold bandwidth (400 Gb/s).
  • the transmitted optical packet is demultiplexed into destination groups by the optical splitter 52 and demultiplexed by the AWG filter 53 in each group (for example, group 4_40) for each wavelength.
  • the optical packets are transmitted to the end hosts (for example, the destination hosts 4_41 and 4_42).
  • the optical packets from the plurality of transmission groups simultaneously reach the same destination group.
  • a reception unit having an optical demultiplexing function is used to increase the total number of the reception units of the system.
  • the scalability of the system can be improved by optical multicasting (optical multiplexing).
  • Fig. 12 shows an example of the timing chart of the switching system 50.
  • one switching period is divided into four time slots.
  • the first time slot and the second slots are illustrated in the left and right views, respectively.
  • the switching system 50 includes 128 25-Gb/s hosts and 16 groups (eight hosts per group) and multicasts four groups at a time.
  • a commercially available transceiver unit based on a PAM4 multilevel format is used in the switching system 50 and performs processing in the total communication amount of 6.4 Tb/s.
  • the switching system according to this embodiment of the present invention shows an example in which the transmission group (transmission side) serving as a physical layer and the destination group (reception side) are distributed and arranged on the input side and the output side of the optical switch.
  • the present invention is not limited to this.
  • the transmission group and the destination group may be mounted at the input port/output port of the optical switch 14 having the same index as identical physical layer units (5_10 to 5_m0).
  • a single ASIC chip is arranged for each group and controls all the switching operations and the data management described above.
  • an ASIC chip 61 has the functions of a control unit 17 and a switching element 41.
  • the end processor (host) is disconnected every time the packet reaches.
  • the ASIC chip 61 is mounted in each host group, and processing associated with the link layer protocol in addition of the switching function is executed.
  • the scalability of the system can be improved by optical multicasting (optical multiplexing).
  • the embodiment of the present invention illustrates an example using wavelength multiplexing in an optical characteristic for multiplexing an optical signal.
  • the present invention is not limited to this.
  • An optical characteristic such as orthogonal polarization and coding may be used.
  • the embodiment of the present invention illustrates an example of the structure, size, material, and the like of each constituent component in the arrangements of the switching apparatus and the switching system, and the control method.
  • the present invention is not limited to this. Any example may be implemented as far as the functions of the switching apparatus and the switching system are enhanced to obtain the same effect as described above.
  • the present invention is related to the switching apparatus and the switching system, each of which switches a packet and is applicable to a computer and an optical communication system.

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Abstract

A switching apparatus (10) according to this invention includes a plurality of optical transmitters (13) each configured to convert an input electric packet in which a priority is set into an optical packet and transmit the optical packet, a plurality of optical receivers (15) each configured to receive the optical packet and converts the optical packet into an electric packet, an optical switch (14) arranged between the plurality of optical transmitters and the plurality of optical receivers and configured to transmit the optical packet input from the optical transmitter to any one of the plurality of optical receivers, and a control unit (17) arranged to be connected to the optical receiver and configured to hold the converted electric packet having a low priority, and transmit the electric packet having a high priority first. Accordingly, this invention can provide a switching apparatus capable of reducing the latency and the power consumption.

Description

SWITCHING APPARATUS AND SWITCHING SYSTEM
The present invention relates to a switching apparatus and a switching system, each of which switches a packet.
In recent years, a data amount is increasing in computer processing. For this reason, in order to improve the processing capacity of a computer, a great deal of attention is paid in a new computer architecture.
For example, as shown in Fig. 14, in a computer architecture, a switching system 70 is connected to a plurality of hosts (a CPU, a GPC, an accelerator, and the like) 72 via an input/output interface 71 and to a memory 73.
In computer processing, the bit rate of a signal generated by a host is greatly increased. At this time, for example, for a bit rate exceeding 10 Gb/s, an electrical signal can reach within a limited distance of about several cm. In order to interconnect hosts spaced apart by about 10 m, an optical link is necessary.
However, a packet switching module is an ASIC switch and processes only an electrical signal. For this reason, optical/electric/optical conversion is required in a switch for the optical signal of the optical link.
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.
In a packet switch, if 128 hosts having units each of which generate, for example, a 25 Gb/s-data packet are assumed, a 6.4-TB/s switch throughput is necessary. If an arrangement (arrangement using optical/electric/optical conversion) using an ASIC switch is implemented to achieve this throughput, the following problem is posed.
First, an ASIC switch of this scale exhibits latency of 400 nsec or more for the fastest scenario having a cut through packet. A high latency occurs in an input signal. In this manner, in a data flow including a large number of packets, a long latency undesirably occurs until the completion of reception.
In addition, the power consumption of the ASIC switch is high, and the power is concentrated in a narrow chip area. As a measure against heat generated by this high power density almost, air cooling almost reaches the limit, and water cooling is necessary.
In addition, particularly, if a high throughput is required, the mounting area of the optical-electronic interface of the switch is undesirably increased. Furthermore, the energy density per unit area increases to increase the power consumption.
In order to solve the problem described above, a switching apparatus according to the present invention includes a plurality of optical transmitters each configured to convert an input electric packet in which a priority is set into an optical packet and transmit the optical packet, a plurality of optical receivers each configured to receive the optical packet and convert the optical packet into an electric packet, an optical switch arranged between the plurality of optical transmitters and the plurality of optical receivers and configured to transmit the optical packet input from the optical transmitter to any one of the plurality of optical receivers, and a control unit arranged to be connected to the optical receiver and configured to hold the converted electric packet having a low priority, and transmit the converted electric packet having a high priority first.
According to the present invention, there are provided a switching apparatus and a switching system, each of which reduces the latency and the power consumption.
Fig.1 is a block diagram showing the arrangement of a switching apparatus according to the first embodiment of the present invention; Fig.2A is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention; Fig.2B is a view for explaining the operation of a conventional switching apparatus; Fig.3A is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention; Fig.3B is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention; Fig.3C is a view for explaining the operation of the switching apparatus according to the first embodiment of the present invention; Fig.4 is a view for explaining the operation of a conventional switching apparatus; Fig.5 is a is a block diagram showing the arrangement of a switching apparatus according to the second embodiment of the present invention; Fig.6 is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention; Fig.7A is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention; Fig.7B is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention; Fig.7C is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention; Fig.7D is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention; Fig.8 is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention; Fig.9A is a view for explaining the operation of the switching apparatus according to the second embodiment of the present invention; Fig.9B is a view for explaining the operation of the conventional switching apparatus; Fig.10 is a block diagram showing the arrangement of a switching system according to the third embodiment of the present invention; Fig.11 is a block diagram showing the arrangement of a switching system according to the fourth embodiment of the present invention; Fig.12 is a view for explaining the operation of the switching system according to the fourth embodiment of the present invention; Fig.13 is a block diagram showing an example of the arrangement of a switching system according to an embodiment of the present invention; and Fig.14 is a block diagram showing the arrangement of the conventional switching system.
(First Embodiment)
A switching apparatus according to the first embodiment of the present invention will be described with reference to Figs. 1A to 4.
(Arrangement of Switching Apparatus)
As shown in Fig. 1, a switching apparatus 10 according to this embodiment includes optical transmitters 13, an optical switch 14, optical receivers 15, and control units 17.
A packet 1 is transmitted from a transmission host 3, and the optical transmitter 13 compresses and demultiplexes the packet 1 into packets (packets 2). The optical switch 14 switches the packet, and the packet 1 is received by a reception host 4 via the optical receiver 15. The packets 1 transmitted from the transmission host 3 are set with priorities.
The optical switch 14 simultaneously transmits all packets for the same output port destination. The destination output port simultaneously receives different packets.
The control unit 17 is an electric chip and arranged while being connected to the optical receiver 15. The control unit 17 executes processing such as arbitration for the packets 2 output from the optical switch 14.
The control unit 17 is locally assigned for each reception host 4 and executes self management of traffic input to the reception host 4. The control unit 17 is arranged adjacent to the reception host 4 and quickly updates the data acquisition priority.
In addition, the control unit 17 manages communication processing of the single reception host 4, thereby performing a high-speed operation.
An information channel is connected to the reception host 4 and the control unit 17 in addition to a data link.
(Operation of Switching Apparatus)
Fig. 2A shows packet processing in the switching apparatus 10. As comparison, Fig. 2B shows a conventional non-blocking switch 20.
In the conventional electric non-blocking switch 20, the bandwidths of all the output ports are constant. The switch 20 can transmit only one packet at one time. For example, if a flow B (101_2) and a flow C (101_3) are transmitted to the same output port, these flows are processed in a single band having a predetermined bandwidth (Fig. 2B).
On the other hand, in the optical switch 14 in the switching apparatus 10 according to this embodiment, the bandwidth of any output port is variable, and all the packets input to the switch can be adjusted. For example, as shown in Fig. 2A, the bandwidth is changed to process the packet in two bands. In this case, the bandwidth of the output port is 1/2 of the total throughput (bandwidth) of the switch.
As described above, the optical switch 14 can cope with a high bandwidth per output port.
As shown in Fig. 2A, in the switching apparatus 10, input data (packet C) 102_3 having a low priority is buffered and held in the RAM of the control unit 17 for a long time.
On the other hand, data (packet B) 102_2 having a high priority is transmitted first.
Input data (packet C) 102_3 having a low priority is transmitted after the completion of the transmission of the data (packet B) 102_2 having a high priority.
In addition, in the switching apparatus 10, an optical data link may be arranged in the control unit 17. Accordingly, optical data can be directly transmitted between the output port of the switch and the reception host 4 capable of processing the optical input signal.
As shown in Figs. 3A to 3C, the optical switch 14 can be arranged based on a broadcast-and-select method.
Signals input to different switch ports are multiplexed for, for example, the respective wavelengths. The input signals are respectively transmitted to all the output ports and selected in the respective output ports based on a desired signal transmission destination.
For example, as shown in Fig. 3A, an input packet 1_1 from a transmission host A (3_1) is demultiplexed by a splitter 18, and demultiplexed packets 2_1 to 2_4 are transmitted to reception hosts 4_1 to 4_4.
In addition, as shown in Fig. 3B, the input packet 1_1 and an input packet 1_4 from the transmission host A (3_1) and a transmission host D (3_4) are demultiplexed by the splitter 18. The demultiplexed packets 2_1 to 2_4 are selected by an optical selection filter 19 in the output port and transmitted to the reception hosts 4_1 to 4_4. In this case, a fast tunable filter or a polarization filter element can be used as the optical selection filter 19.
In addition, as shown in Fig. 3C, the input packets 1_1 and 1_4 from the transmission hosts A and D (3_1 and 3_4) are demultiplexed by the splitter 18. The demultiplexed packets 2_1 to 2_4 are received by the plurality of optical receivers 15 for the respective packets and transmitted to the reception hosts 4_1 to 4_4.
(Effect)
In the conventional non-blocking type packet switch 20, a data packet input to any input port can be switched to a desired output port.
If a plurality of packets are simultaneously transmitted to the same output port, contention occurs, and arbitration is executed for the colliding packets. In the arbitration, a packet having a high priority is first selected and transmitted, and other packets are buffered and subsequentially transmitted.
As described above, in the conventional non-blocking type packet switch 20, arbitration is required in scheduling performed when simultaneously transmitting the packets to the same destination.
In the arbitration process, generally pieces of information concerning the validity, priority, and selection of the data are collected to a central control unit (not shown) in accordance with the concentrated control method in a system before the determination in the arbitration. The accuracy of this determination highly depends on all pieces of necessary information in the immediately preceding updating. However, in a dynamic computing system, it is difficult to maintain the accuracy of the information of immediately preceding updating.
More specifically, for example, as shown in Fig. 4, the reception host 4 is assigned with a computational task for reducing the two data flows, that is, a flow A (201_1) and the flow B (201_2). The host 4 has already processed the flow A (201_1) and waits for the reception of the flow B (201_2).
On the other hand, the flow C is another flow to be transmitted to the host 4 and reaches the switch before the arrival of the flow B with a time difference. If the time difference is more than zero, the switch transmits the flow C to the host 4.
Figure JPOXMLDOC01-appb-I000001
When operating the optical switch 14, transmission of the flow B is not started until the completion of all the transmission operations of the flow C.
When operating the electric switch 21, arbitration of the packet is started between the flow C (201_3) and the flow B (201_2) when the flow B (201_2) arrives. As far as an arbitrator 22 of the switch has already received a notification, a priority is given to the flow B (201_2). If a failure or delay occurs in the arbitrator 22 notified of a request of the host 4 using the flow B (201_2) as the highest destination, the flow B (201_2) is not sufficiently quickly switched even if the time difference is equal to zero.
The host 4 is a processing unit, and the data acquisition priority changes at high speed. In this case, it is difficult to continuously update the arbitrator 22 with the changing priority. Accordingly, in the processing of all the system communication amount, it is difficult for the arbitrator 22 to sufficiently quickly and accurately perform determination for a very large amount of dynamic data.
As described above, in the conventional non-blocking type packet switch 20, since arbitration is executed by a concentrated control method, the number of ports of the switch and the processing capacity (throughput) are increased, and the process is complicated. As a result, the latency and power consumption increase.
In addition, collection of information necessary for the arbitration process, such as the priority, in accordance with a predetermined rule is difficult because of an increase of the system scale.
On the other hand, in the switching apparatus 10 according to this embodiment, arbitration is executed by the control unit 17 on the output side in accordance with the distributed control method. In this case, the host 4 connected to each output port determines a packet to be processed first. In this manner, the control unit 17 can locally execute arbitration for each host.
In this case, all packets are output in a predetermined duration T. In other words, the data rate of the output signal is equal to that of the input signal.
As described above, the data rate of the packets reaching the same output port in different slots is converted into the initial (original) data rate. In addition, the packets are output in an order requested to the connected output host. In this manner, the minimum latency is given to the packet having the highest priority.
Accordingly, in the switching apparatus of this embodiment, the latency and power consumption in switching can be reduced, and the load for acquiring information necessary for the arbitration process can be reduced (eliminated).
(Second Embodiment)
A switching apparatus according to the second embodiment of the present invention will be described with reference to Figs. 5 to 9B.
(Arrangement of Switching Apparatus)
As shown in Fig. 5, an example of a switching apparatus (packet switch) 30 according to this embodiment includes input ports 11, input blocks 12, optical transmitters 13, an optical switch 14, optical receivers 15, and output ports 16. The switching apparatus 30 also includes control units 17 connected to the optical receivers 15. In the switching apparatus 30 according to this embodiment, the optical switch 14 is operated in the time slot operation.
(Operation of Optical Switch)
The operation of the switching apparatus (packet switch) 30 according to this embodiment will be described with reference to Fig. 6.
Fig. 6 shows an example of the basic operation of the packet switch 30 for executing non-block processing using a 4 x 4 switch. This packet switch 30 is based on the time slot operation to be described below.
First, a packet is switched for each input group. In this case, arbitration is executed within the input packet of the same input group. Since this arbitration is executed for the small number of ports and a low communication amount, the operation can be executed fast without requiring a long time.
An electric packet 1 input to the switch has a bandwidth BW (bit/sec) and a duration T. The desired output port 16 to which the packet is transmitted is set.
In the packet switch 30, a packet switching operation to any one of the four output ports 16 is complete within the time T. This is because if a time of T or longer is required for the switching of a single packet, the next input packet is blocked and a continuous switching delay is accumulated.
In order to match the input packet 1 with the time slot, the optical transmitter 13 compresses the input packet 1 by a factor (in this case, 4) equal in number to the number of ports (that is, the number of optical receivers to which packets are transmitted). That is, the duration of the input packet is divided by a factor equal in number of the number of ports and becomes T/4. In addition, the bandwidth is multiplied by the same factor and becomes 4BW in order to retain the packet data contents.
As described above, an optical input packet 2 is generated by satisfying the above conditions.
Next, the optical switch 14 distributes the respective optical input packets 2 to the desired output ports 16 using periodic time slots. In this case, the periodic operation of the switch is divided into four time slots.
Figure JPOXMLDOC01-appb-I000002
The distribution (switching) of the optical input packets 2 is repeatedly executed for each time slot in accordance with a sequence formed by steps S1 to S4 (to be described later).
Finally, the optical receiver 15 converts the packet into an electric packet, and the packet switch 30 outputs the electric packet in a predetermined duration. In other words, the data rate of the signal output from the packet switch 30 is equal to the data rate of the input signal.
In the packets arriving in different time slots whose time difference is reduced, the data rate is changed to the first data rate. This change is performed in the arrival order of packets. In addition, the priority of the change may be set by another arbitration.
The switching operation in the above optical switch 14 will be described with reference to Figs. 7A to 7D. Figs. 7A to 7D show examples of a series of switching operations in steps S1 to S4, respectively.
In the packet switch 30, packets are input to four ports 11_1 to 11_4, respectively. The packet (packet C) input to the port 11_3 has the desired output port as a port 16_3 and has the highest priority.
The packets (packets A and D) input to ports 11_1 and 11_4 have the desired ports as ports 16_2 and 16_1, respectively, and have the second highest priority.
　The packet (packet B) input to the port 11_2 has the desired output port as a port 16_4 and has the third highest priority.
First, since the packet C has the highest priority, the packet C is transmitted to the output port 16_3 in a duration of the first time slot (step S1 and Fig. 7A).
Since the packets A and D have the second highest priority, they are simultaneously transmitted to the output ports 16_2 and 16_1 in a duration of the second time slot (step S2 and Fig. 7B). In this case, since the packets A and D are transmitted to different output ports, no collision occurs.
Next, since the packet (packet B) input to the port B has the third highest priority, it is transferred to the output port 16_4 in a duration of the third time slot (step S3 and Fig. 7C).
Finally, since transmission of the packets A to D is complete in the previous step (step 3), switching is not executed in a duration of the fourth time slot (step S4 and Fig. 7D).
Figure JPOXMLDOC01-appb-I000003
As described above, if the operation cycle (the four steps) is complete, all the input packets are simultaneously switched to desired output ports by the non-blocking method.
In this switching operation, in all the steps, as shown in Figs. 7A to 7D, the respective output ports 16 are connected to only one input port 11. In addition, the input port 11 is connected to the desired output port 16. In switching of the packet input to the input port 11, the packet is arranged in a correct (accurate) time slot (the divided duration).
In addition, the optical switch 14 is operated, as shown in Fig. 8.
In the packet switch 30, 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 are prioritized in the order of the packets B, A, D, and C.
First, since the packet B has the highest priority, the packet B is transmitted to the output port 16_2 in a duration of the first time slot (step S1).
Next, since the packet A has the second highest priority, the packet A is transmitted to the output port 16_2 in a duration of the second time slot (step S2).
Next, since the packet D has the third highest priority, the packet D is transmitted to the output port 16_2 in a duration of the third time slot (step S3).
Finally, since the packet C has the fourth highest priority, the packet C is transmitted to the output port 16_2 in a duration of the fourth time slot (step S4).
As described above, if the operation cycle (the four steps) is complete, all the input packets are simultaneously switched to desired output ports by the non-blocking method. In this case, since the packets A to D are transmitted in different time slots, no collision occurs.
In this manner, in the packet switch 30, all the input packets transmitted to the same output port are correctly (accurately) switched to this port in the time T.
(Effect)
The effect of the switching apparatus 30 according to this embodiment will be described below.
In the optical switch according to this first embodiment, problems are posed in which the signal output level is reduced along with the number of ports (Fig. 3A) and the number of constituent units such as the optical selection filter 19 such as the fast tunable filter and the optical receiver 15 are increased (Figs. 3B and 3C). In particular, it is technically difficult to control a large number of fast tunable units, and the power consumption is increased.
The optical switch 14 according to this embodiment can process a large number of dynamic data sufficiently at high speed due to the introduction of time slots and an increase in bit rate without decreasing the signal output level along with an increase in the number of ports and without increasing the constituent units, thereby reducing power consumption.
In addition, in the switching apparatus 10 according to this embodiment, the arbitration by the conventional concentrated control method is distributed into the following steps, and the arbitration is executed.
First, the optical switch 14 transmits the packets of different input groups to the same output group in different time slots. The optical switch 14 can execute this step at a high data rate with accurate time control.
Next, arbitration is executed by the control unit 17 on the output side in accordance with the distributed control method. In this case, the host 4 connected to each output port determines a packet to be processed first. In this manner, the control unit 17 can locally execute arbitration for each host.
In this case, all packets are output in a predetermined duration T. In other words, the data rate of the output signal is equal to that of the input signal.
As described above, the data rate of the packets reaching the same output port in different slots is converted into the initial (original) data rate. In addition, the packets are output in an order requested to the connected output host. In this manner, the minimum latency is given to the packet having the highest priority.
Accordingly, in the switching apparatus of this embodiment, the latency and power consumption in switching can be reduced, and the load for acquiring information necessary for the arbitration process can be reduced (eliminated).
The effect of the switching apparatus 30 will be described in detail in comparison with the conventional non-blocking switch.
Fig. 9A shows the mode of latency in a flow switched by the switching apparatus 30. As comparison, Fig. 9B shows the mode of latency in a flow switched by the conventional non-blocking switch 20.
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.
At this time, as shown in Fig. 9B, in the conventional non-blocking switch 20, since the flows A (2_10) and D (2_40) are processed in a single band, the delay times are accumulated. As a result, if the length (time) of one packet is T, the delay time is 3T, that is, the length (time) of the immediately preceding transmitted flow.
As described above, in the conventional non-blocking switch 20, the delay time is increased, and the latency is increased.
On the other hand, as shown in Fig. 9A, in the switching apparatus 30, since the flows A (2_10) and D (2_40) are processed in two bands, the delay time is rarely accumulated and is not less than T. This delay occurs in only the first packet and can be neglected as compared with the length 3T of the flow.
As described above, the switching apparatus 30 has a short delay time, so that the latency can be reduced.
In a normal electric switch, an input packet passes through the input port of the switch. First, the destination and the priority are examined, and then concentrated arbitrary is executed. The first packet to be transmitted is determined from all the packets having the same output port destination.
Concentrated arbitration processing becomes complicated with an increase in the number of switch ports and the throughput. As a result, the communication latency is increased, and the power consumption is increased.
On the other hand, according to the switching apparatus 30, since the packet can be switched without executing the concentrated arbitration requiring a long time, the communication latency is reduced, and the power consumption can be reduced.
Since the optical switch 14 performs part of the switching processing, the power consumption is lower than that of the ASIC formed by a CMOS transistor, and the switching capacity can be increased.
In addition, since a chiplet is used for the input block 12, the area occupied by the input block 12 can be reduced. As a result, even if an optical-electric interface is mounted, the total area of the packet switch (chip) is not increased. Accordingly, the optical-electric interface is mounted, and the throughput (processing capacity) of the switch can be increased without changing the chip area. In addition, the power consumption can be reduced by using the chiplet.
The contention between the ports of the same block can be prevented, and non-blocking processing can be executed.
In addition, to simultaneously transmit the plurality of packets to the same destination by the conventional packet switch, parallel optical receivers in number equal to the number of packets are necessary.
On the other hand, according to the switching apparatus 30, compact copies of the input packets are created at a high rate and divided and transmitted in short time slots. As described above, transmission of the packets to the same destination can be processed within a short time as compared with the actual packet input interval by using time interleaving.
In this case, the optical receiver 15 using the switching apparatus 30 can be operated in correspondence with this burst mode transmission.
The switching apparatus 30 is formed by four 1 x 4 switching units corresponding to the different input ports 11 to easily implement a high-speed 4 x 4 optical switch device. In the 4 x 4 optical switch device, the time (transition time) for transitioning one switch mode (for example, Fig. 7A) to another switch mode (for example, Fig. 7B) is very short as compared with the duration of the input packet.
For example, if it is assumed that the transition time can be neglected, the transition time can be reduced to 10 psec in an actually usable technique. This transition time is very short as compared with a 100-Gb/s Ethernet packet having a duration of 120 nsec.
In addition, a short guard time may be provided between the optical packets to prevent all data losses between switching operations.
The bandwidth of the packet generated by the host is multiplied by a coefficient F (switch port count). For example, in an 8 x 8 switch, a 25-Gb/s electric packet must be converted into a 200-Gb/s optical packet. This optical packet is generated by using a direct modulation laser and a multilevel modulation format.
In this case, since a distance between hosts assumed in this embodiment is short, this embodiment is applicable to a high data rate. In addition, the optical dispersion effect has a negligible level.
Furthermore, a packet having a high bit rate may be generated by another method. To scale up the number of interconnected hosts without performing concentrated control, this switch may be used as a core switching unit in a hybrid switching architecture.
(Third Embodiment)
Next, a switching system 40 according to the third embodiment of the present invention will be described with reference to Fig. 10. The switching system 40 can be scaled by grouping hosts.
(Arrangement of Switching System)
As shown in Fig. 10, the switching system 40 according to this embodiment includes a plurality of transmission (source) groups 3_10 to 3_40 on the transmission side. Each transmission group includes a plurality of transmission hosts (for example, 3_11 and 3_12) and a switching element 41.
A plurality of destination groups (for example, 4_20 and the like) are provided on the reception side. Each destination group includes an optical receiver 15, a control unit 17, a reception-side switch 43, and a plurality of reception hosts (for example, 4_21, 4_22, and the like). Other arrangements are the same as in the first embodiment.
The switching element 41 is a low-radix ASIC switch chip.
The optical switch 14 has an operation period divided into four input/output ports and four time slots. In this case, not each host unit, but the groups 3_10 to 3_40 of the transmission host are connected to the ports of the optical switch 14.
For example, in the transmission group A (3_10), the ASIC switch 41 and two hosts A1 and A2 (3_11 and 3_12) are arranged to be adjacent to each other. The ASIC switch 41 and the two hosts 3_11 and 3_12 are electrically linked at a short distance.
In this case, scalability is improved by an increase in the number of host units per group. In addition, in order to enhance the feature of the electric link, the number of host units per group is preferably about 10.
As shown in Fig. 10, the transmission 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.
The hosts of the same group exchange the packets using an ASIC switch 41. For example, the ASIC switch 41 of the group A (3_10) is used to interconnect the hosts A1 and A2 (3_11 and 3_12). Packets between hosts of different groups (to be referred to as an inter-group packets hereinafter) are exchanged via the interconnection with the optical switch 14.
The groups of the respective destinations (outputs) are connected to only one transmission (input) group in all the time slots. Switching of the inter-group packets of the transmission group is processed by arranging packets (optical packets of the shortened duration) within the accurate time slots. In each time slot, the transmission group is connected to the desired destination group.
(Operation of Switching System)
The operation of the switching system 40 according to this embodiment will be described with reference to Fig. 10.
In the switching system 40, end-to-end transmission of the inter-group packet from the transmission host to the destination host is formed by the following three steps.
As the first step, electric switching for a packet is executed in a level of not the destination host but the destination group.
More specifically, in order to demultiplex a packet generated by the host, electric switching is executed by the transmission groups 3_10 to 3_40 using the local ASIC switch 41 in accordance with the destination group.
The inter-group packets simultaneously transmitted to the same group are collected by destination virtual queues regardless of the difference between the destination hosts. In this case, queues G1 to G4 (42_1 to 42_4) correspond to the destination groups 4_10 to 4_20.
In this case, as an example, two packets to be simultaneously transmitted from the hosts A1 and A2 (3_11 and 3_12) to the hosts 4_22 and 4_21 of the destination group 4_20 are assumed. At this time, both the packets are switched in the queue G2 (42_1).
For example, the packets from the hosts A1 and A2 (3_11 and 3_12) are transmitted in a bandwidth twice 25 Gb/s.
As the second step, when packets are respectively arranged in the matching time slots in the optical switch 14, optical switching is executed for the packets (optical packets of the shortened duration) transmitted to the desired destination group.
For example, a packet is demultiplexed into four packets and compressed four times. The demultiplexed packets are assigned to the first time slot to the fourth time slot in the time T and transmitted in the bandwidth of 200 Gb/s.
More specifically, the packets are transmitted from the corresponding queue in the ASIC switch 41 to the respective optical switches 14.
In this case, the hosts of the same group simultaneously generate packets to be transmitted to the same group.
In addition, to prevent the contention, these simultaneous packets are adjusted in the identical time slots of the optical switch 14. This can be achieved by the bandwidth of the optical transmitter 13.
For identification, packets of the different transmission hosts need not be demultiplexed using different wavelengths. Note that if a WDM-based transmitter is used, the request of the high bandwidth along with an increase in the number of host units per group can be satisfied.
As the third step, the packet can reach the desired destination group. For example, all the 25-Gb/s packets can be received in the time T.
Subsequently, electric switching is executed for the packet.
More specifically, the plurality of packets are simultaneously transmitted to the same end host, and a packet having a high priority is processed first. The self management of the input data packet as described previously is executed for the local ASIC switch 41 to which data reception is assigned.
As described above, in the switching system 40 according to this embodiment, arbitration by the conventional concentrated control method is executed by distributing the arbitration by the following three steps.
In the first step, the input ports of the switching system 40 are divided into groups (for example, 3_10 to 3_40), and the packets of each group are processed independently of the remaining packets. The output groups of the same destination which are simultaneously input are processed as those of the same group in the input group and are transmitted without executing arbitration. In this manner, since the input ports are grouped into small groups, this step can be performed at high speed.
As in the second embodiment, as the second step, the processing step of the optical switch is executed. As the third step, the arbitration step is executed.
Accordingly, in the switching apparatus of this embodiment, the latency and power consumption in switching can be reduced, and the load for acquiring information necessary for the arbitration process can be reduced (eliminated).
According to the switching system 40 of this embodiment, the hosts are grouped to increase the number of interconnected hosts, and scalability of the system can be improved.
(Fourth Embodiment)
Next, a switching system 50 according to the fourth embodiment of the present invention will be described with reference to Figs. 11 to 13. The switching system 50 is scaled by optical multicasting (optical multiplexing).
(Arrangement of Switching System)
As shown in Fig. 11, a switching system 50 according to this embodiment includes an optical multiplexer 51 between an optical transmitter 13 and an optical switch 14. The switching system 50 also includes a first optical demultiplexer 52 and a second optical demultiplexer 53 between the optical switch 14 and the optical receiver 15. Other arrangements are the same as in the third embodiment.
The plurality of optical transmitters 13 are connected to the optical multiplexer 51.
In addition, the output port of the optical switch 14 is connected to the fist optical demultiplexer 52, and the second optical demultiplexer 53 is connected to the output portion of the first optical demultiplexer 52.
This embodiment illustrates an example using wavelength multiplexing of an optical signal as an example of optical multicasting.
To wavelength-multiplex an optical signal, an AWG (Arrayed Waveguide Grating) optical coupler is used in the optical multiplexer 51.
In addition, an optical splitter is used in the first optical demultiplexer 52 and demultiplexes an optical signal at a predetermined power ratio.
An AWG filter is used in the second optical demultiplexer 53 and optically demultiplexes an optical signal for each wavelength.
(Operation of Switching System)
For example, as shown in Fig. 11, in the switching system 50, 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) output optical packets having different wavelengths, respectively.
The optical packets having different wavelengths are multiplexed by the AWG optical coupler 51 and simultaneously transmitted to a plurality of destination groups 4_10 to 4_40 in the same time slot.
As described above, the optical packets can be transmitted to a large number of groups, for example, a large number of end hosts without increasing the number of ports of the switch.
In addition, a higher multicasting ratio can be implemented, and the maximum achievable ratio can be determined by the power budget of the optical link.
For example, if the two optical packets having different wavelengths are transmitted in the bandwidth of 200 Gb/s, the packets can be transmitted in a two-fold bandwidth (400 Gb/s).
The transmitted optical packet is demultiplexed into destination groups by the optical splitter 52 and demultiplexed by the AWG filter 53 in each group (for example, group 4_40) for each wavelength. The optical packets are transmitted to the end hosts (for example, the destination hosts 4_41 and 4_42).
As described above, if multicasting is used, the optical packets from the plurality of transmission groups simultaneously reach the same destination group. To process packets from different transmission groups, a reception unit having an optical demultiplexing function is used to increase the total number of the reception units of the system.
According to the switching system 50, the scalability of the system can be improved by optical multicasting (optical multiplexing).
Fig. 12 shows an example of the timing chart of the switching system 50. In the switching system 50, one switching period is divided into four time slots. Among these time slots, the first time slot and the second slots are illustrated in the left and right views, respectively.
The switching system 50 includes 128 25-Gb/s hosts and 16 groups (eight hosts per group) and multicasts four groups at a time.
A commercially available transceiver unit based on a PAM4 multilevel format is used in the switching system 50 and performs processing in the total communication amount of 6.4 Tb/s.
The switching system according to this embodiment of the present invention shows an example in which the transmission group (transmission side) serving as a physical layer and the destination group (reception side) are distributed and arranged on the input side and the output side of the optical switch. However, the present invention is not limited to this.
As shown in Fig. 13, in a switching system 60, the transmission group and the destination group may be mounted at the input port/output port of the optical switch 14 having the same index as identical physical layer units (5_10 to 5_m0). At this time, a single ASIC chip is arranged for each group and controls all the switching operations and the data management described above. In this case, an ASIC chip 61 has the functions of a control unit 17 and a switching element 41.
For example, in a normal data link layer protocol, to apply the protocol procedure to a packet, the end processor (host) is disconnected every time the packet reaches.
It is confirmed as an example of the protocol procedure that a packet bit reaches accurately (bit check sum). In addition, an overhead bit added to a main payload to be processed is deleted.
In this embodiment, the ASIC chip 61 is mounted in each host group, and processing associated with the link layer protocol in addition of the switching function is executed.
By the concentrated mounting of the physical layer switching and the function of the high link layer, the latency and the power consumption of the end-to-end transmission can be reduced.
According to the switching system of this embodiment, the scalability of the system can be improved by optical multicasting (optical multiplexing).
The embodiment of the present invention illustrates an example using wavelength multiplexing in an optical characteristic for multiplexing an optical signal. The present invention is not limited to this. An optical characteristic such as orthogonal polarization and coding may be used.
The embodiment of the present invention illustrates an example of the structure, size, material, and the like of each constituent component in the arrangements of the switching apparatus and the switching system, and the control method. However, the present invention is not limited to this. Any example may be implemented as far as the functions of the switching apparatus and the switching system are enhanced to obtain the same effect as described above.
The present invention is related to the switching apparatus and the switching system, each of which switches a packet and is applicable to a computer and an optical communication system.
10: switching apparatus
13: optical transmitter
14: optical switch

Claims (8)

  1. A switching apparatus comprising:
    a plurality of optical transmitters each configured to convert an input electric packet in which a priority is set into an optical packet and transmit the optical packet;
    a plurality of optical receivers each configured to receive the optical packet and convert the optical packet into an electric packet;
    an optical switch arranged between the plurality of optical transmitters and the plurality of optical receivers and configured to transmit the optical packet input from the optical transmitter to any one of the plurality of optical receivers; and
    a control unit arranged to be connected to the optical receiver and configured to hold the converted electric packet having a low priority, and transmit the converted electric packet having a high priority first.
  2. The switching apparatus according to claim 1, wherein the control unit includes an optical data link.
  3. The switching apparatus according to claim 1, wherein the optical packet transmitted from the optical transmitter is multiplexed, demultiplexed, and received by the optical receiver in accordance with a predetermined optical characteristic.
  4. The switching apparatus according to claim 1, wherein
    the optical transmitter demultiplexes the optical packet by a number equal to the number of optical receivers to which the optical packets are transmitted, and
    the optical switch transmits the demultiplexed optical packets in time slots respectively assigned to the demultiplexed optical packets.
  5. A switching system sequentially comprising:
    a plurality of transmission hosts;
    a switching element;
    a switching apparatus according to claim 1; and
    a plurality of reception hosts,
    wherein
    the plurality of transmission hosts are classified into a plurality of transmission groups,
    a single switching element is provided for each transmission group,
    a single optical transmitter is connected for each transmission group, and
    the switching element controls the plurality of transmission hosts and is interconnected with the switching apparatus.
  6. The switching system according to claim 5, further comprising:
    an optical multiplexer arranged between the plurality of optical transmitters and the optical switch and configured to multiplex optical packets output from the plurality of optical transmitters;
    a first optical demultiplexer sequentially arranged between the optical switch and the plurality of optical receivers and configured to demultiplex the optical packet output from the optical switch; and
    a second optical demultiplexer configured to select and demultiplex the demultiplexed optical packet in accordance with a predetermined optical characteristic and output the demultiplexed optical packets, respectively, to the plurality of reception hosts.
  7. The switching system according to claim 5, wherein
    the transmission host,
    the switching element,
    the optical transmitter,
    the optical receiver,
    the control unit, and
    the reception host are included in a single unit.
  8. The switching system according to claim 7, wherein
    the switching element,
    the control unit, and
    a function of a high link layer is concentratedly mounted.
PCT/JP2022/031220 2022-08-18 2022-08-18 Switching apparatus and switching system WO2024038541A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6253031A (en) * 1985-09-02 1987-03-07 Nippon Telegr & Teleph Corp <Ntt> Wavelength multiplex optical fiber transmission system
JPH01238248A (en) * 1988-03-18 1989-09-22 Hitachi Ltd High-speed packet exchange device using special dividing type switch
JPH11127120A (en) * 1997-10-22 1999-05-11 Nec Corp Coding in optical network and optical switch control system
JP2014096700A (en) * 2012-11-09 2014-05-22 Nippon Telegr & Teleph Corp <Ntt> Transfer method and transfer device for optical packet in optical packet switch network
US20160309243A1 (en) * 2013-12-25 2016-10-20 Huawei Technologies Co., Ltd. Optical Switching Apparatus
WO2021009869A1 (en) * 2019-07-17 2021-01-21 日本電信電話株式会社 Optical demultiplexing device, optical separation device, optical transport system, and optical transport method

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6253031A (en) * 1985-09-02 1987-03-07 Nippon Telegr & Teleph Corp <Ntt> Wavelength multiplex optical fiber transmission system
JPH01238248A (en) * 1988-03-18 1989-09-22 Hitachi Ltd High-speed packet exchange device using special dividing type switch
JPH11127120A (en) * 1997-10-22 1999-05-11 Nec Corp Coding in optical network and optical switch control system
JP2014096700A (en) * 2012-11-09 2014-05-22 Nippon Telegr & Teleph Corp <Ntt> Transfer method and transfer device for optical packet in optical packet switch network
US20160309243A1 (en) * 2013-12-25 2016-10-20 Huawei Technologies Co., Ltd. Optical Switching Apparatus
WO2021009869A1 (en) * 2019-07-17 2021-01-21 日本電信電話株式会社 Optical demultiplexing device, optical separation device, optical transport system, and optical transport method

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