Network relay device, network transmission device, relay method, packet transmission method, relay program, and packet transmission program

Abstract

This network relay device makes up a network for relaying packets, and comprises: a reception unit that receives a packet destined for a destination device; an acquisition unit that acquires, from the packet received by the reception unit, arrival upper limit information indicating the deadline for the arrival of the packet at the destination device, and arrival lower limit information indicating the lower limit of the time range during which the packet should be made to arrive at the destination device; and a transmission unit that performs transmission processing for transmitting the packet received by the reception unit or a packet which is based on the packet received by the reception unit, wherein the transmission unit performs priority control during the transmission processing on the basis of the arrival upper limit information, and stands by for packet transmission on the basis of the arrival lower limit information.

Description

[Technical Field]

[0001] The present disclosure relates to a network relay device, a network transmission device, a relay method, a packet transmission method, a relay program, and a packet transmission program. This application claims priority based on Japanese Patent Application No. 2021-205850, filed on December 20, 2021, the disclosure of which is incorporated herein in its entirety. [Background technology]

[0002] Non-patent document 1 (ITU-T, "New Service and Capabilities for Network 2030: Description, Technical Gap and Performance Target Analysis," October 2019) states that, in order to safely remotely control vehicles, by around 2030, it will be necessary to achieve stable communication with small and constant latency between on-board devices installed in vehicles and control devices. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] ITU-T, “New Service and Capabilities for Network 2030: Description, Technical Gap and Performance Target Analysis”, October 2019 Summary of the Invention

[0004] The network relay device of the present disclosure is a network relay device that constitutes a network for relaying packets, and is equipped with a receiving unit that receives the packets addressed to a destination device, an acquiring unit that acquires, from the packets received by the receiving unit, arrival limit information indicating the deadline for the packets to reach the destination device, and a transmitting unit that performs priority control when transmitting the packets received by the receiving unit or the packets based on the packet received by the receiving unit, based on the arrival limit information acquired by the acquiring unit.

[0005] The network transmission device of the present disclosure includes a generation unit that generates a packet to be transmitted to a destination device, the packet including upper limit information indicating the deadline for the packet to reach the destination device, and a transmission unit that transmits the packet generated by the generation unit to the destination device via a network.

[0006] The relay method disclosed herein is a relay method in a network relay device that constitutes a network for relaying packets, and includes the steps of receiving the packet addressed to a destination device, obtaining, from the received packet, upper limit arrival information indicating the deadline for the packet to reach the destination device, and performing priority control when transmitting the received packet or a packet based on the received packet based on the obtained upper limit arrival information.

[0007] The packet transmission method of the present disclosure is a packet transmission method in a network transmission device, and includes the steps of generating a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device, and transmitting the generated packet to the destination device via a network.

[0008] The relay program disclosed herein is a relay program used in a network relay device that constitutes a network for relaying packets, and is a program that causes a computer to function as a receiving unit that receives packets addressed to a destination device, an acquiring unit that acquires, from the packets received by the receiving unit, arrival limit information indicating the deadline for the packets to reach the destination device, and a transmitting unit that performs priority control when transmitting the packets received by the receiving unit or the packets based on the packet received by the receiving unit based on the arrival limit information acquired by the acquiring unit.

[0009] The packet transmission program of the present disclosure is a packet transmission program used in a network transmission device, and is a program that causes a computer to function as a generation unit that generates a packet to be sent to a destination device, the packet including arrival limit information indicating the deadline for the packet to reach the destination device, and a transmission unit that transmits the packet generated by the generation unit to the destination device via a network.

[0010] One aspect of the present disclosure may be realized not only as a network relay device having such a characteristic processing unit, but also as a semiconductor integrated circuit that realizes all or part of the network relay device, or as a communication system including the network relay device.Furthermore, one aspect of the present disclosure may be realized not only as a network transmission device having such a characteristic processing unit, but also as a semiconductor integrated circuit that realizes all or part of the network transmission device, or as a communication system including the network transmission device. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating an example of a configuration of a transmission device according to an embodiment of the present disclosure. [Figure 3]FIG. 3 is a diagram illustrating an example of an IP packet generated by a generating unit in the transmitting device according to the embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram illustrating an example of a time setting table stored in a storage unit in a transmission device according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram illustrating an example of a configuration of a relay device according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram illustrating an example of a configuration of a relay device according to an embodiment of the present disclosure. [Figure 7] FIG. 7 is a flowchart illustrating an example of an operation procedure when a transmission device according to an embodiment of the present disclosure transmits an IP packet. [Figure 8] FIG. 8 is a flowchart illustrating an example of an operation procedure when a relay device according to an embodiment of the present disclosure performs relay processing of an IP packet. DETAILED DESCRIPTION OF THE INVENTION

[0012] In a communication system having a network for relaying packets between devices, there is a demand for a technique for reducing communication delays.

[0013] [Problem to be solved by this disclosure] However, Non-Patent Document 1 does not propose a specific method for realizing the above-mentioned stable communication.

[0014] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a network relay device, a network transmission device, a relay method, a packet transmission method, a relay program, and a packet transmission program that can achieve more stable communication.

[0015] [Effects of this disclosure] According to the present disclosure, more stable communication can be achieved.

[0016] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0017] (1) A network relay device according to an embodiment of the present disclosure forms a network for relaying packets, and the network relay device includes a receiving unit that receives the packets addressed to a destination device, an acquiring unit that acquires, from the packets received by the receiving unit, upper limit information indicating a deadline for the packets to reach the destination device and lower limit information indicating a lower limit of a time range within which the packets must reach the destination device, and a transmitting unit that performs a transmission process to transmit the packets received by the receiving unit or packets based on the packets received by the receiving unit, and the transmitting unit performs priority control in the transmission process based on the upper limit information acquired by the acquiring unit, and waits to transmit the packets based on the lower limit information acquired by the acquiring unit.

[0018] In this way, a network relay device can be configured to perform priority control when transmitting a received packet or a packet based on the received packet based on the upper limit information of the packet, thereby enabling the packet to reach the destination device earlier than the arrival deadline, thereby preventing delays in the packet's arrival time. Furthermore, a configuration that waits for packet transmission based on the lower limit information of the received packet enables priority control to be performed so that the packet reaches the destination device within the desired time range, thereby enabling the packet to reach the destination device within the desired time range. This allows for more stable communication.

[0019] (2) In the above (1), the transmitting unit may discard the packet without transmitting it based on a result of comparing the current time with the deadline indicated by the upper limit information.

[0020] With this configuration, the network load can be reduced by discarding packets that cannot reach the destination device before the deadline, taking into account the results of comparing the current time with the deadline.

[0021] (3) A network transmission device according to an embodiment of the present disclosure includes a generation unit that generates a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device, and a transmission unit that transmits the packet generated by the generation unit to the destination device via a network.

[0022] In this way, by configuring a network transmission device to generate and transmit a packet addressed to a destination device that includes arrival limit information, priority control of the packet can be performed in the network so that the packet arrives at the destination device earlier than the arrival deadline, thereby suppressing delays in the arrival time of the packet and thereby achieving more stable communication.

[0023] (4) In the above (3), the generating unit may generate the packet including the reach upper limit information that is determined depending on the type of service provided by the packet.

[0024] With this configuration, in a network, it is possible to perform comprehensive priority control of multiple packets related to different services based on reach upper limit information determined for each service so that the multiple packets can arrive at a destination device earlier than their arrival deadlines. For example, multiple packets related to multiple types of services may be transmitted to an in-vehicle device, which is an example of a destination device, and comprehensive priority control of the multiple packets can be performed based on the reach upper limit information for each of the multiple packets related to the different services.

[0025] (5) In the above (3) or (4), the generating unit may generate the packet further including arrival lower limit information indicating a lower limit of a time range in which the packet should arrive at the destination device.

[0026] With this configuration, in a network, for example, priority control of packets can be performed so that the packets arrive at the destination device at a time within the time range in which they should arrive, thereby making it possible for the packets to arrive at the destination device within the desired time range.

[0027] (6) In the above (5), the generating unit may generate the packet including the lower limit information determined depending on the type of service provided by the packet.

[0028] With this configuration, in the network, priority control of multiple packets related to different services can be performed uniformly based on the arrival limit information determined for each service so that the packets can arrive at the destination device at a time within the time range they should arrive at.

[0029] (7) A relay method according to an embodiment of the present disclosure is a relay method in a network relay device, wherein the network relay device constitutes a network for relaying packets, and the relay method includes the steps of receiving the packet addressed to a destination device, acquiring from the received packet upper limit information indicating a deadline for the packet to reach the destination device and lower limit information indicating a lower limit of a time range in which the packet must reach the destination device, and performing a transmission process to transmit the received packet or a packet based on the received packet, wherein in the step of performing the transmission process, priority control in the transmission process is performed based on the acquired upper limit information, and transmission of the packet is waited for based on the acquired lower limit information.

[0030] In this way, in a network relay device, by using a method for performing priority control when transmitting a received packet or a packet based on the received packet based on the upper arrival limit information of the packet, it is possible to perform priority control on the packet so that the packet arrives at the destination device earlier than the arrival deadline, thereby suppressing delays in the packet arrival time.Furthermore, by using a method for suspending packet transmission based on the lower arrival limit information of the received packet, it is possible to perform priority control so that the packet arrives at the destination device within the time range in which it should arrive, thereby enabling the packet to arrive at the destination device within the desired time range.This therefore enables more stable communication.

[0031] (8) A packet transmission method according to an embodiment of the present disclosure is a packet transmission method in a network transmission device, and includes the steps of generating a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device, and transmitting the generated packet to the destination device via a network.

[0032] In this way, by using a method in which a network transmitting device generates and transmits a packet addressed to a destination device that includes arrival limit information, priority control of the packet can be performed in the network so that the packet arrives at the destination device earlier than the arrival deadline, thereby suppressing delays in the arrival time of the packet and realizing more stable communication.

[0033] (9) A relay program according to an embodiment of the present disclosure is a relay program used in a network relay device, the network relay device constituting a network for relaying packets, the relay program causing a computer to function as: a receiving unit that receives the packet addressed to a destination device; an acquiring unit that acquires, from the packet received by the receiving unit, upper limit information indicating the deadline for the packet to reach the destination device and lower limit information indicating the lower limit of the time range within which the packet must reach the destination device; and a transmitting unit that performs transmission processing to transmit the packet received by the receiving unit or a packet based on the packet received by the receiving unit, and the transmitting unit performs priority control in the transmission processing based on the upper limit information acquired by the acquiring unit, and waits to transmit the packet based on the lower limit information acquired by the acquiring unit.

[0034] In this way, a network relay device can be configured to perform priority control when transmitting a received packet or a packet based on the received packet based on the upper limit information of the packet, thereby enabling the packet to reach the destination device earlier than the arrival deadline, thereby preventing delays in the packet's arrival time. Furthermore, a configuration that waits for packet transmission based on the lower limit information of the received packet enables priority control to be performed so that the packet reaches the destination device within the desired time range, thereby enabling the packet to reach the destination device within the desired time range. This allows for more stable communication.

[0035] (10) A packet transmission program according to an embodiment of the present disclosure is a packet transmission program used in a network transmission device, and is a program for causing a computer to function as a generation unit that generates a packet to be transmitted to a destination device, the packet including upper limit information indicating the deadline for the packet to reach the destination device, and a transmission unit that transmits the packet generated by the generation unit to the destination device via a network.

[0036] In this way, by configuring a network transmission device to generate and transmit a packet addressed to a destination device that includes arrival limit information, priority control of the packet can be performed in the network so that the packet arrives at the destination device earlier than the arrival deadline, thereby suppressing delays in the arrival time of the packet and thereby achieving more stable communication.

[0037] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and their description will not be repeated. Furthermore, at least some of the embodiments described below may be combined in any manner.

[0038] [Configuration and basic operation] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment of the present disclosure. Referring to FIG. 1, a communication system 501 includes a transmitting device 101, a relay device 201, relay devices 202A and 202B, and in-vehicle devices 301A and 301B. Hereinafter, each of the relay devices 202A and 202B will also be referred to as a relay device 202, and each of the in-vehicle devices 301A and 301B will also be referred to as an in-vehicle device 301. The transmitting device 101 is an example of a network transmitting device. The relay device 201 and the relay device 202 are examples of network relay devices. The in-vehicle device 301 is an example of a destination device. For example, the transmitting device 101 and the relay devices 201 and 202 are time-synchronized.

[0039] The in-vehicle device 301 is mounted on the vehicle 1. As an example, the transmitting device 101, the relay device 201, and the relay device 202 are provided outside the vehicle 1. The communication system 501 may be configured to include three or more in-vehicle devices 301. The communication system 501 may also be configured to include in-vehicle devices 301 mounted on different vehicles 1.

[0040] Relay device 201 and relay device 202 constitute network 200 for relaying IP (Internet Protocol) packets. Network 200 relays IP packets between transmitting device 101 and in-vehicle device 301 by wireless communication or wired communication. Network 200 is, for example, a WAN (Wide Area Network).

[0041] The transmitting device 101 provides a service by distributing distribution information to the in-vehicle device 301 at regular or irregular distribution timings. For example, the transmitting device 101 remotely controls the vehicle 1 by distributing, as the distribution information, control information S1 used for autonomous driving control of the vehicle 1 to the in-vehicle device 301. Furthermore, for example, the transmitting device 101 distributes, as the distribution information, switching information S2 indicating a switching time tx, which is the timing at which the lighting state of a signal lamp is switched, to the in-vehicle device 301.

[0042] More specifically, the transmitting device 101 generates an IP packet containing distribution information and addressed to the in-vehicle device 301 , and transmits the generated IP packet to the in-vehicle device 301 via the network 200 .

[0043] The relay device 201 and the relay device 202 perform a relay process of relaying the IP packets transmitted from the transmitting device 101 to the in-vehicle device 301 .

[0044] For example, the relay device 201 transmits the IP packet PA addressed to the in-vehicle device 301A received from the transmission device 101 to the relay device 202A. The relay device 202A transmits the IP packet PA received from the relay device 201 to the in-vehicle device 301A.

[0045] Furthermore, for example, the relay device 201 transmits the IP packet PB addressed to the in-vehicle device 301B received from the transmission device 101 to the relay device 202B. The relay device 202B transmits the IP packet PB received from the relay device 201 to the in-vehicle device 301B.

[0046] The in-vehicle device 301 receives IP packets from the transmitting device 101 via the network 200, and acquires distribution information from the received IP packets. For example, the in-vehicle device 301 drives the vehicle 1 based on the acquired distribution information.

[0047] More specifically, the in-vehicle device 301A receives the IP packet PA from the relay device 201A, acquires distribution information from the received IP packet PA, and drives the vehicle 1 based on the acquired distribution information. The in-vehicle device 301B receives the IP packet PB from the relay device 201B, acquires distribution information from the received IP packet PB, and drives the vehicle 1 based on the acquired distribution information.

[0048] In communications in a communications system 501 including an in-vehicle device 301, from the viewpoint of driving safety, requirements regarding communication delays are stricter than in general consumer communications, and the arrival time of IP packets must be controlled in millisecond or microsecond units.

[0049] The communication system 501 may not include the relay device 202. In this case, the relay device 201 transmits the IP packet PA addressed to the in-vehicle device 301A received from the transmission device 101 to the in-vehicle device 301A, and transmits the IP packet PB addressed to the in-vehicle device 301B received from the transmission device 101 to the in-vehicle device 301B. The communication system 501 may also include one or three or more relay devices 202.

[0050] In addition, at least one of the transmitting device 101, the relay device 201, and the relay device 202 may be mounted on the vehicle 1.

[0051] Furthermore, the destination of the IP packet from the transmitting device 101 is not limited to the in-vehicle device 301. The transmitting device 101 may be configured to generate an IP packet addressed to a device mounted on a robot, for example, and transmit the generated IP packet to that device via the network 200.

[0052] <Transmitting device 101> 2 is a diagram illustrating an example of a configuration of a transmitting device according to an embodiment of the present disclosure. Referring to FIG. 2, transmitting device 101 includes a generating unit 11, a transmitting unit 12, a synchronization processing unit 13, a counter 14, and a storage unit 15. A part or all of generating unit 11, transmitting unit 12, and synchronization processing unit 13 are realized by, for example, a processing circuit including one or more processors. Storage unit 15 is, for example, a non-volatile memory included in the processing circuit.

[0053] The counter 14 counts clock pulses generated by an oscillator circuit using a quartz crystal oscillator, for example, and holds time information indicating the counted value. This time information indicates, for example, the current time.

[0054] The synchronization processing unit 13 updates the count value of the counter 14 in accordance with the Network Time Protocol (NTP). More specifically, the synchronization processing unit 13, for example, periodically transmits an NTP request to an NTP server (not shown) as an NTP client. When the NTP server receives the NTP request from the synchronization processing unit 13, it transmits an NTP response including NTP information indicating the current time held by the NTP server to the synchronization processing unit 13 as a response to the received NTP request. When the synchronization processing unit 13 receives the NTP response from the NTP server, it updates the time information of the counter 14 based on the NTP information included in the received NTP response and a known communication delay time in communication between the synchronization processing unit 13 and the NTP server.

[0055] The generation unit 11 generates an IP packet that is to be transmitted to the in-vehicle device 301 and includes upper limit arrival information. The upper limit arrival information indicates a deadline for the IP packet to reach the in-vehicle device 301. As an example, the generation unit 11 generates an IP packet that includes an upper limit arrival time UL as the upper limit arrival information.

[0056] For example, the generation unit 11 generates an IP packet that further includes lower limit information. The lower limit information indicates the lower limit of a time range in which the IP packet should arrive at the in-vehicle device 301. As an example, the generation unit 11 generates an IP packet that includes a lower limit time LL as the lower limit information.

[0057] Fig. 3 is a diagram illustrating an example of an IP packet generated by a generation unit in a transmission device according to an embodiment of the present disclosure. Fig. 3 illustrates, as an example, an IP packet conforming to IPv (Internet Protocol version) 4. Referring to Fig. 3, the IP packet includes an IP header and an IP payload.

[0058] The generation unit 11 periodically or irregularly generates distribution information and determines an upper arrival time UL and a lower arrival time LL of the generated distribution information. The generation unit 11 then generates an IP packet addressed to the in-vehicle device 301, in which the generated distribution information is stored in an IP payload and the upper arrival time UL and the lower arrival time LL are stored in an option field in the IP header. The generation unit 11 may be configured to generate an IP packet in which the upper arrival time UL and the lower arrival time LL are stored in a field other than the option field.

[0059] For example, the generation unit 11 generates an IP packet including an upper limit arrival time UL and a lower limit arrival time LL that are determined depending on the type of service provided by the IP packet. More specifically, the generation unit 11 determines the upper limit arrival time UL and the lower limit arrival time LL depending on the type of distribution information stored in the IP payload of the IP packet.

[0060] 4 is a diagram illustrating an example of a time setting table stored in a storage unit in a transmission device according to an embodiment of the present disclosure. Referring to FIG. 4, storage unit 15 stores a time setting table T1 indicating a correspondence relationship between distribution information and an upper arrival limit time UL and a lower arrival limit time LL.

[0061] When the generation unit 11 generates distribution information, it refers to the time setting table T1 in the memory unit 15, obtains the upper limit arrival time UL corresponding to the generated distribution information, and stores the obtained upper limit arrival time UL in the option field in the IP header of the IP packet.

[0062] Furthermore, if there is a lower arrival limit time LL corresponding to the distribution information in the time setting table T1, the generation unit 11 further acquires the lower arrival limit information and stores the acquired lower arrival limit time LL in an option field in the IP header of the IP packet. For example, when storing the lower arrival limit time LL in the option field, the generation unit 11 further stores a flag in the option field indicating that the lower arrival limit time LL is stored.

[0063] For example, when generating control information S1 as distribution information, the generation unit 11 refers to the time setting table T1 and determines that the upper limit arrival time UL should be set to "generation time ts + 10 milliseconds." The generation unit 11 then acquires the current time indicated by the time information of the counter 14 as the generation time ts of the control information S1, and determines the time obtained by adding 10 milliseconds to the acquired generation time ts as the upper limit arrival time UL. The generation unit 11 stores the determined upper limit arrival time UL in the options field of the IP header of the IP packet, and outputs the IP packet to the transmission unit 12.

[0064] Furthermore, for example, the generation unit 11 acquires the switching time tx from a signal control device (not shown) that controls the lighting color of the signal lamps, generates switching information S2 indicating the acquired switching time tx, and then refers to the time setting table T1 to determine that the upper limit arrival time UL and the lower limit arrival time LL should be set to "switching time tx+5 seconds" and "switching time tx," respectively. The generation unit 11 then stores the switching time tx and the time obtained by adding 5 seconds to the switching time tx in the option field of the IP header of the IP packet, and outputs the IP packet to the transmission unit 12.

[0065] The transmitter 12 transmits the IP packet generated by the generator 11 to the in-vehicle device 301 via the network 200. More specifically, the transmitter 12 transmits the IP packet received from the generator 11 to the relay device 201.

[0066] For example, by setting the upper limit arrival time of an IP packet containing control information S1 to "generation time ts + 10 milliseconds" and making the IP packet arrive at the in-vehicle device 301 by the upper limit arrival time, highly real-time control can be achieved.

[0067] Furthermore, for example, by setting the lower limit arrival time of an IP packet containing switching information S2 to the switching time tx and transmitting the IP packet to multiple on-board devices 301 mounted on the same vehicle 1 or different vehicles 1 in advance before the switching time tx, congestion of IP packets can be avoided compared to a configuration in which the IP packet is transmitted simultaneously to the multiple on-board devices 301 when the switching time tx is reached.

[0068] <Relay device 201> FIG. 5 is a diagram illustrating an example of a configuration of a relay device according to an embodiment of the present disclosure. FIG. 5 illustrates a configuration of a relay device 201. Referring to FIG. 5, the relay device 201 includes a receiving unit 21, a time acquiring unit 22, a synchronization processing unit 23, a counter 24, a storage unit 25, and a transmitting unit 30. The time acquiring unit 22 is an example of an acquiring unit. Some or all of the receiving unit 21, the time acquiring unit 22, the synchronization processing unit 23, and the transmitting unit 30 are realized by, for example, a processing circuit including one or more processors. The storage unit 25 is, for example, a non-volatile memory included in the processing circuit. For example, the storage unit 25 stores a correspondence table T2 indicating a correspondence relationship between the destination IP address of an IP packet and the relay device 202 to which the IP packet is to be relayed.

[0069] The transmitter 30 includes a transfer unit 31, priority control units 32A and 32B, and output units 33A and 33B. Hereinafter, each of the priority control units 32A and 32B will also be referred to as a priority control unit 32, and each of the output units 33A and 33B will also be referred to as an output unit 33. For example, the transmitter 30 includes a priority control unit 32 and an output unit 33 corresponding to each of the relay devices 202. More specifically, the transmitter 30 includes a priority control unit 32A and an output unit 33A corresponding to the relay device 202A, and a priority control unit 32B and an output unit 33B corresponding to the relay device 202B.

[0070] The counter 24 counts clock pulses generated by an oscillator circuit using a quartz crystal oscillator, for example, and holds time information indicating the counted value. This time information indicates, for example, the current time.

[0071] Similar to synchronization processing unit 13 in transmitting device 101, synchronization processing unit 23 updates the count value of counter 24 in accordance with NTP. This allows counter 14 in transmitting device 101 and counter 24 in relay device 201 to be synchronized.

[0072] The receiving unit 21 receives an IP packet addressed to the in-vehicle device 301. More specifically, the receiving unit 21 receives an IP packet addressed to the in-vehicle device 301 from the transmitting device 101. The receiving unit 21 outputs the received IP packet to the time acquiring unit 22.

[0073] The time acquiring unit 22 acquires arrival upper limit information from the IP packet received by the receiving unit 21. More specifically, the time acquiring unit 22 receives the IP packet from the receiving unit 21 and acquires the arrival upper limit time UL from the option field in the IP header of the received IP packet. The time acquiring unit 22 outputs the IP packet and the acquired arrival upper limit time UL to the transmitting unit 30.

[0074] The transmitter 30 performs priority control when transmitting IP packets received by the receiver 21, based on the upper limit arrival time UL acquired by the time acquirer 22. For example, the transmitter 30 receives IP packets and the upper limit arrival time UL from the time acquirer 22, and schedules the transmission order of the IP packets for each relay device 202 as a relay destination, based on the upper limit arrival time UL. The transmitter 30 transmits the IP packets to the relay device 202 according to the scheduling result.

[0075] More specifically, the transfer unit 31 in the transmission unit 30 receives the IP packet and the arrival upper limit time UL from the time acquisition unit 22 and acquires the destination IP address from the received IP packet. The transfer unit 31 determines the relay device 202 to which the IP packet is to be relayed, based on the correspondence table T2 in the storage unit 25 and the acquired destination IP address. The transfer unit 31 then outputs the IP packet and the arrival upper limit time UL received from the time acquisition unit 22 to the priority control unit 32 corresponding to the relay device 202 to which the IP packet is to be relayed.

[0076] Specifically, when the relay destination of the IP packet is the relay device 202A, the transfer unit 31 outputs the IP packet and the upper limit arrival time UL to the priority control unit 32A. On the other hand, when the relay destination of the IP packet is the relay device 202B, the transfer unit 31 outputs the IP packet and the upper limit arrival time UL to the priority control unit 32B.

[0077] The priority control unit 32 receives IP packets to be transmitted from the transfer unit 31 and holds the received IP packets. The priority control unit 32 outputs to the output unit 33, at an output timing according to a predetermined cycle, the IP packet having the earliest upper limit arrival time UL among one or more IP packets held by the priority control unit 32.

[0078] The output unit 33 receives the IP packet from the priority control unit 32 and transmits the received IP packet to the corresponding relay device 202 .

[0079] The transmitter 30 may be configured to perform priority control when transmitting IP packets based on the IP packets received by the receiver 21, based on the arrival upper limit time UL acquired by the time acquirer 22. More specifically, the relay device 201 further includes a processor (not shown) that processes the IP packets received by the receiver 21, such as by converting and deleting data. The transmitter 30 performs priority control when transmitting the IP packets processed by the processor to the relay device 202.

[0080] (IP packet discard) For example, the transmitter 30 discards the IP packet without transmitting it based on the result of comparing the current time with the upper limit time UL.

[0081] More specifically, the transfer unit 31 receives the IP packet and the arrival upper limit time UL from the time acquisition unit 22, and compares the received arrival upper limit time UL with the current time indicated by the time information of the counter 24. The transfer unit 31 discards the IP packet in accordance with the time length TL1 from the current time to the arrival upper limit time UL.

[0082] Specifically, if the time length TL1 from the current time to the upper limit arrival time UL of the IP packet is equal to or greater than a predetermined threshold value Th1, the transfer unit 31 outputs the IP packet and the upper limit arrival time UL to the priority control unit 32. On the other hand, if the time length TL1 from the current time to the upper limit arrival time UL of the IP packet is less than the threshold value Th1 or if the current time exceeds the upper limit arrival time UL, the transfer unit 31 discards the IP packet.

[0083] For example, the storage unit 25 stores a threshold value Th1 that varies depending on the destination IP address. The transfer unit 31 acquires, from the storage unit 25, the threshold value Th1 that corresponds to the destination IP address of the IP packet received from the time acquisition unit 22, and outputs the IP packet to the priority control unit 32 or discards the IP packet depending on the result of comparing the acquired threshold value Th1 with the time length TL1.

[0084] (Waiting for sending IP packets based on the arrival lower limit time LL) For example, the time acquiring unit 22 further acquires lower arrival limit information from the IP packet. More specifically, if the lower arrival limit time LL is stored in the option field in the IP header of the IP packet received from the receiving unit 21, the time acquiring unit 22 further acquires the lower arrival limit time LL. The time acquiring unit 22 outputs the IP packet and the acquired upper arrival limit time UL and lower arrival limit time LL to the transmitting unit 30.

[0085] For example, the transmitting unit 30 waits for the transmission of the IP packet based on the arrival lower limit time LL acquired by the time acquiring unit 22.

[0086] More specifically, the transfer unit 31 in the transmission unit 30 receives the IP packet and the upper arrival limit time UL and lower arrival limit time LL from the time acquisition unit 22, and compares the received lower arrival limit time LL with the current time indicated by the time information of the counter 24. The transfer unit 31 waits for output of the IP packet to the priority control unit 32 based on the comparison result between the current time and the lower arrival limit time LL.

[0087] Specifically, if the current time has already reached the arrival lower limit time LL or the time length TL2 from the current time to the arrival lower limit time LL of the IP packet is less than a predetermined threshold value Th2, the forwarding unit 31 outputs the IP packet and the arrival upper limit time UL to the priority control unit 32 corresponding to the relay device 202 to which the IP packet is to be relayed.

[0088] On the other hand, if the current time has not reached the arrival lower limit time LL and the time length TL2 from the current time to the arrival lower limit time LL of the IP packet is equal to or greater than the threshold value Th2, the transfer unit 31 stores the IP packet and the arrival upper limit time UL received from the time acquisition unit 22 in the storage unit 25 and waits for the time length TL2 to become less than the threshold value Th2. Then, if the time length TL2 becomes less than the threshold value Th2, the transfer unit 31 acquires the corresponding IP packet and the arrival upper limit time UL from the storage unit 25 and outputs the acquired IP packet and the arrival upper limit time UL to the priority control unit 32 corresponding to the relay device 202 to which the IP packet is to be relayed.

[0089] For example, the storage unit 25 stores a threshold value Th2 that varies depending on the destination IP address. The transfer unit 31 acquires, from the storage unit 25, the threshold value Th2 that corresponds to the destination IP address of the IP packet received from the time acquisition unit 22, and outputs the IP packet to the priority control unit 32 or suspends output of the IP packet to the priority control unit 32 depending on the result of comparing the acquired threshold value Th2 with the time length TL2.

[0090] <Relay device 202> FIG. 6 is a diagram illustrating an example of a configuration of a relay device according to an embodiment of the present disclosure. FIG. 6 illustrates a configuration of relay device 202. Compared to relay device 201, relay device 202 includes a transmitter 130 instead of transmitter 30 and a memory 125 instead of memory 25. The receiver 21, the time acquisition unit 22, the synchronization processing unit 23, and the transmitter 130 may all or partly be implemented by a processing circuit including one or more processors. The memory 125 may be a nonvolatile memory included in the processing circuit. For example, the memory 125 stores address information indicating the destination IP address of an IP packet to be relayed.

[0091] The transmission unit 130 includes a transfer unit 131 , a priority control unit 132 , and an output unit 133 .

[0092] The receiving unit 21 receives an IP packet addressed to the vehicle-mounted device 301 from the relay device 201 and outputs the received IP packet to the time acquiring unit 22 .

[0093] As described above, the time acquiring unit 22 receives an IP packet from the receiving unit 21 and acquires the upper limit arrival time UL from the option field in the IP header of the received IP packet. Then, the time acquiring unit 22 outputs the IP packet and the acquired upper limit arrival time UL to the transmitting unit 30.

[0094] The transmitter 130 performs priority control when transmitting IP packets received by the receiver 21, based on the upper limit arrival time UL acquired by the time acquirer 22. For example, the transmitter 130 receives IP packets and the upper limit arrival time UL from the time acquirer 22, and schedules the order in which the IP packets are to be transmitted to the in-vehicle device 301 based on the upper limit arrival time UL. The transmitter 130 transmits the IP packets to the in-vehicle device 301 according to the scheduling result.

[0095] More specifically, the transfer unit 131 in the transmission unit 130 receives an IP packet and an arrival upper limit time UL from the time acquisition unit 22, and acquires a destination IP address from the received IP packet. If the acquired destination IP address matches the destination IP address indicated by the address information in the storage unit 125, the transfer unit 131 outputs the IP packet and arrival upper limit time UL received from the time acquisition unit 22 to the priority control unit 132. On the other hand, if the acquired destination IP address does not match the destination IP address indicated by the address information in the storage unit 125, the transfer unit 131 discards, for example, the IP packet and arrival upper limit time UL received from the time acquisition unit 22.

[0096] The priority control unit 132 receives IP packets from the transfer unit 131 and holds the received IP packets. The priority control unit 132 outputs to the output unit 133, at an output timing according to a predetermined cycle, the IP packet having the earliest upper limit arrival time UL among one or more IP packets held by the priority control unit 132.

[0097] The output unit 133 receives the IP packet from the priority control unit 132 and transmits the received IP packet to the in-vehicle device 301 .

[0098] The transmitter 130 may be configured to perform priority control when transmitting IP packets based on the IP packets received by the receiver 21, based on the arrival upper limit time UL acquired by the time acquirer 22. More specifically, the relay device 202 further includes a processor (not shown) that processes the IP packets received by the receiver 21, such as by converting and deleting data. The transmitter 130 performs priority control when transmitting the IP packets processed by the processor to the in-vehicle device 301.

[0099] (IP packet discard) For example, the transmitting unit 130 discards the IP packet without transmitting it based on the result of comparing the current time with the arrival upper limit time UL. More specifically, the forwarding unit 131 in the transmitting unit 130 receives the IP packet and the arrival upper limit time UL from the time acquiring unit 22, and compares the received arrival upper limit time UL with the current time indicated by the time information of the counter 24. The forwarding unit 131 discards the IP packet in accordance with the time length TL1 from the current time to the arrival upper limit time UL.

[0100] For example, the storage unit 125 stores a threshold value Th1 that varies depending on the destination IP address. The transfer unit 131 acquires, from the storage unit 125, the threshold value Th1 that corresponds to the destination IP address of the IP packet received from the time acquisition unit 22, and outputs the IP packet to the priority control unit 132 or discards the IP packet depending on the result of comparing the acquired threshold value Th1 with the time length TL1.

[0101] (Waiting for sending IP packets based on the arrival lower limit time LL) For example, the time acquiring unit 22 further acquires a lower arrival limit time LL from the IP packet. More specifically, if the lower arrival limit time LL is stored in an options field in the IP header of the IP packet received from the receiving unit 21, the time acquiring unit 22 further acquires the lower arrival limit time LL. The time acquiring unit 22 outputs the IP packet and the acquired upper arrival limit time UL and lower arrival limit time LL to the transmitting unit 130.

[0102] For example, the transmitting unit 130 waits to transmit an IP packet based on the arrival lower limit time LL acquired by the time acquiring unit 22. More specifically, the forwarding unit 131 in the transmitting unit 130 receives the IP packet, the arrival upper limit time UL, and the arrival lower limit time LL from the time acquiring unit 22, and compares the received arrival lower limit time LL with the current time indicated by the time information of the counter 24. The forwarding unit 131 waits to output the IP packet to the priority control unit 32 based on the comparison result between the current time and the arrival lower limit time LL.

[0103] Specifically, if the current time has already reached the arrival lower limit time LL or if the time length TL2 from the current time to the arrival lower limit time LL of the IP packet is less than a predetermined threshold value Th2, the transfer unit 131 outputs the IP packet and the arrival upper limit time UL to the priority control unit 132. On the other hand, if the current time has not reached the arrival lower limit time LL and the time length TL2 from the current time to the arrival lower limit time LL of the IP packet is equal to or greater than the threshold value Th2, the transfer unit 131 saves the IP packet and the arrival upper limit time UL received from the time acquisition unit 22 in the storage unit 125 and waits for the time length TL2 to become less than the threshold value Th2. Then, if the time length TL2 becomes less than the threshold value Th2, the transfer unit 131 acquires the corresponding IP packet and the arrival upper limit time UL from the storage unit 125 and outputs the acquired IP packet and the arrival upper limit time UL to the priority control unit 132.

[0104] For example, the storage unit 125 stores a threshold value Th2 that varies depending on the destination IP address. The transfer unit 131 acquires, from the storage unit 125, the threshold value Th2 that corresponds to the destination IP address of the IP packet received from the time acquisition unit 22, and outputs the IP packet to the priority control unit 132 or suspends output of the IP packet to the priority control unit 132 depending on the result of comparing the acquired threshold value Th2 with the time length TL2.

[0105] [Operation flow] FIG. 7 is a flowchart illustrating an example of an operation procedure when a transmission device according to an embodiment of the present disclosure transmits an IP packet.

[0106] Referring to FIG. 7, first, transmitting device 101 waits for the timing to distribute distribution information to in-vehicle device 301 (NO in step S102), and when the distribution timing arrives (YES in step S102), generates distribution information (step S104).

[0107] Next, the transmitting device 101 determines the upper limit arrival time UL and the lower limit arrival time LL of the generated distribution information (step S106).

[0108] Next, the transmitting device 101 generates an IP packet addressed to the in-vehicle device 301, in which the distribution information is stored in the IP payload and the upper limit arrival time UL and the lower limit arrival time LL are stored in the option field in the IP header (step S108).

[0109] Next, the transmitting device 101 transmits the generated IP packet to the in-vehicle device 301 via the network 200 (step S110).

[0110] Next, the transmitting device 101 waits for a new distribution timing (NO in step S102).

[0111] In step S106, the transmitting device 101 may determine the upper limit arrival time UL but may not determine the lower limit arrival time LL. In this case, in step S108, the transmitting device 101 generates an IP packet that includes the upper limit arrival time UL but does not include the lower limit arrival time LL.

[0112] 8 is a flowchart showing an example of an operation procedure when a relay device according to an embodiment of the present disclosure performs a relay process on an IP packet. Fig. 8 shows a flowchart showing an example of an operation procedure when a relay device 201 performs a relay process on an IP packet.

[0113] Referring to FIG. 8, first, the relay device 201 waits for an IP packet addressed to the in-vehicle device 301 (NO in step S202), and when it receives an IP packet addressed to the in-vehicle device 301 (YES in step S202), it obtains the upper limit arrival time UL and the lower limit arrival time LL from the received IP packet (step S204).

[0114] Next, the relay device 201 compares the upper limit time UL with the current time indicated by the time information of the counter 24 (step S206).

[0115] Next, if the time length TL1 from the current time to the upper limit arrival time UL of the IP packet is less than the threshold value Th1 corresponding to the destination IP address of the IP packet, or if the current time exceeds the upper limit arrival time UL (NO in step S208), the relay device 201 discards the IP packet (step S210).

[0116] Next, the relay device 201 waits for a new IP packet addressed to the in-vehicle device 301 (NO in step S202).

[0117] On the other hand, if the time length TL1 from the current time to the upper limit arrival time UL of the IP packet is greater than or equal to the threshold value Th1 (YES in step S208), the relay device 201 compares the upper limit arrival time UL with the current time indicated by the time information of the counter 24 (step S212).

[0118] Next, if the current time has already reached the arrival lower limit time LL or the time length TL2 from the current time to the arrival lower limit time LL of the IP packet is less than the threshold value Th2 (YES in step S214), the relay device 201 schedules the transmission order of the IP packet for each relay device 202 to which it is to be relayed based on the arrival upper limit time UL, and transmits the IP packet to the relay device 202 according to the scheduling results (step S216).

[0119] On the other hand, if the current time has not reached the arrival lower limit time LL and the time length TL2 is equal to or greater than the threshold value Th2 (NO in step S214), the relay device 201 waits for the time length TL2 to become less than the threshold value Th2, and when the time length TL2 becomes less than the threshold value Th2 (YES in step S214), it performs priority control when transmitting IP packets based on the arrival upper limit time UL. More specifically, the relay device 201 schedules the transmission order of the IP packets for each relay device 202 as a relay destination based on the arrival upper limit time UL, and transmits the IP packets to the relay device 202 according to the scheduling result (step S216).

[0120] Next, the relay device 201 waits for a new IP packet addressed to the in-vehicle device 301 (NO in step S202).

[0121] If the arrival lower limit time LL is not stored in the received IP packet, the relay device 201 does not perform the processes in steps S212 and S214.

[0122] Furthermore, in the transmitting device 101 according to the embodiment of the present disclosure, the generating unit 11 is configured to generate an IP packet including an upper arrival time UL and a lower arrival time LL determined depending on the service provided by the IP packet, but this is not limited to this. The generating unit 11 may be configured to determine the upper arrival time UL and the lower arrival time LL based on, for example, the generation time of distribution information, regardless of the service provided by the IP packet, and generate an IP packet including the determined upper arrival time UL and lower arrival time LL.

[0123] Furthermore, in the relay device 201 according to the embodiment of the present disclosure, the transmitter 30 is configured to discard an IP packet without transmitting it based on the comparison result between the current time and the upper limit time UL. However, this is not limited to this. For example, the transmitter 30 may be configured to transmit an IP packet regardless of the comparison result between the current time and the upper limit time UL. Specifically, the transmitter 30 may be configured to transmit an IP packet not only when the time length TL1 from the current time to the upper limit time UL of the IP packet is equal to or greater than the threshold value Th1, but also when, for example, the current time is beyond the upper limit time UL. Similarly, the transmitter 130 in the relay device 202 may be configured to transmit an IP packet not only when the time length TL1 from the current time to the upper limit time UL of the IP packet is equal to or greater than the threshold value Th1, but also when, for example, the current time is beyond the upper limit time UL.

[0124] Furthermore, in communication system 501 according to the embodiment of the present disclosure, relay device 201 is configured to include time acquisition unit 22 and priority control unit 32, and relay device 202 is configured to include time acquisition unit 22 and priority control unit 132, but this is not limiting. Relay device 201 may be configured to include time acquisition unit 22 and priority control unit 32, while relay device 202 may not be configured to include time acquisition unit 22 and priority control unit 132. Furthermore, relay device 202 may be configured to include time acquisition unit 22 and priority control unit 132, while relay device 201 may not be configured to include time acquisition unit 22 and priority control unit 32. In other words, one of relay device 201 and relay device 202 may be configured not to perform priority control when transmitting IP packets based on the upper limit arrival time.

[0125] However, there is a demand for technology that enables more stable communication. More specifically, with the recent increase in communication speed, there is a demand for stable communication with reduced communication delays and high real-time performance. For example, technologies such as DiffServ (Differentiated Services) QoS (Quality of Service), IntServ QoS, and centralized QoS are known as priority control technologies for IP packets in wide-area IP networks. However, these technologies may cause delays in the arrival time of IP packets at the destination device, making it impossible to achieve stable communication.

[0126] In contrast, in the relay device 201 according to the embodiment of the present disclosure, the receiver 21 receives an IP packet addressed to the in-vehicle device 301. The time acquirer 22 acquires, from the IP packet received by the receiver 21, an upper limit arrival time UL indicating a deadline for the IP packet to reach the in-vehicle device 301. The transmitter 30 performs priority control when transmitting the IP packet received by the receiver 21 or an IP packet based on the IP packet received by the receiver 21, based on the upper limit arrival time UL acquired by the time acquirer 22.

[0127] In this way, relay device 201 and relay device 202 are configured to perform priority control when transmitting a received IP packet or an IP packet based on the IP packet based on the upper limit arrival time UL of the IP packet, thereby performing priority control of the IP packet so that the IP packet arrives at in-vehicle device 301 earlier than the upper limit arrival time UL, thereby suppressing delays in the arrival time of the IP packet. Therefore, relay device 201 and relay device 202 according to the embodiment of the present disclosure can achieve more stable communication.

[0128] The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0129] Each process (each function) in the above-described embodiments is realized by a processing circuit including one or more processors. The processing circuit may be configured as an integrated circuit or the like that combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute each of the processes. The one or more processors may execute each of the processes according to the program read from the one or more memories, or according to a logic circuit pre-designed to execute each of the processes. The processor may be various processors suitable for computer control, such as a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array (FPGA), and an application-specific integrated circuit (ASIC). Note that the physically separate processors may cooperate with each other to execute each of the processes. For example, the processors mounted on a plurality of physically separated computers may cooperate with each other to execute the above processes via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), the Internet, etc. The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a semiconductor memory, and installed into the memory from the recording medium.

[0130] The above description includes the following additional features. [Appendix 1] A network relay device that constitutes a network for relaying packets, a receiving unit that receives the packet addressed to a destination device; an acquisition unit that acquires, from the packet received by the receiving unit, arrival upper limit information indicating a deadline for the packet to reach the destination device; a transmitting unit that performs priority control when transmitting the packet received by the receiving unit or the packet based on the packet received by the receiving unit, based on the reach upper limit information acquired by the acquiring unit, the receiving unit receives the packet from a network transmitting device; The network transmitting device and the network relay device are time-synchronized.

[0131] [Appendix 2] a generating unit that generates a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device; a transmitting unit that transmits the packet generated by the generating unit to the destination device via a network, The network transmitting device and the network relay devices that constitute the network are time-synchronized.

[0132] [Appendix 3] A network relay device, the network relay device constitutes a network for relaying packets; the network relay device comprises a processing circuit; The processing circuitry receiving the packet addressed to a destination device; obtaining, from the received packet, upper limit information indicating a deadline for the packet to reach the destination device; performing a transmission process for transmitting the received packet or a packet based on the received packet; The network relay device performs priority control in the transmission process based on the acquired reachable upper limit information.

[0133] [Appendix 4] 1. A network transmission device, comprising: a processing circuit; The processing circuitry generating a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device; a network transmitting device that transmits the generated packet to the destination device via a network; [Explanation of symbols]

[0134] 1 vehicle 11 Generation part 12 Transmitter 13 Synchronization processing section 14 Counter 15 Storage section 21 Receiving unit 22 Time acquisition section 23 Synchronization processing section 24 Counter 25 Memory section 30 Transmitter 31 Transfer Unit 32A, 32B, 32 Priority control section 33A,33B,33 Output section 101 Transmitting device 125 Storage section 130 Transmitter 131 Transfer Department 132 Priority control section 133 Output section 200 Network 201 Relay device 202A, 202B, 202 Relay device 301A,301B,301 On-vehicle equipment 501 Communication Systems T1 Time Setting Table

Claims

1. A network relay device, the network relay device constitutes a network for relaying packets; The network relay device a receiving unit that receives the packet addressed to a destination device; an acquisition unit that acquires, from the packet received by the receiving unit, upper arrival limit information indicating a deadline for the packet to reach the destination device and lower arrival limit information indicating a lower limit of a time range in which the packet should reach the destination device; a transmitting unit that performs a transmitting process to transmit the packet received by the receiving unit or a packet based on the packet received by the receiving unit, The transmitting unit performs priority control in the transmission process based on the upper limit information acquired by the acquiring unit, and waits to transmit the packet based on the lower limit information acquired by the acquiring unit.

2. 2. The network relay device according to claim 1, wherein said transmitter discards said packet without transmitting it based on a result of a comparison between a current time and said deadline indicated by said upper limit information.

3. a generating unit that generates a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device; a transmitting unit that transmits the packet generated by the generating unit to the destination device via a network, The network transmission device, wherein the generation unit generates the packet further including arrival lower limit information indicating a lower limit of a time range in which the packet should arrive at the destination device.

4. The network transmission device according to claim 3 , wherein the generation unit generates the packet including the reach upper limit information that is determined depending on the type of service provided by the packet.

5. 5. The network transmission device according to claim 3, wherein the generation unit generates the packet including the lower limit information determined depending on the type of service provided by the packet.

6. A relay method in a network relay device, the network relay device constitutes a network for relaying packets; The relay method includes: receiving the packet destined for a destination device; acquiring, from the received packet, upper limit information indicating a deadline for the packet to reach the destination device and lower limit information indicating a lower limit of a time range in which the packet should reach the destination device; performing a transmission process for transmitting the received packet or a packet based on the received packet; In the step of performing the transmission processing, priority control is performed in the transmission processing based on the acquired upper limit information, and transmission of the packet is put on hold based on the acquired lower limit information.

7. A packet transmission method in a network transmission device, comprising: generating a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device; transmitting the generated packet to the destination device over a network; A packet transmission method, wherein the step of generating a packet further includes generating the packet including lower limit information indicating a lower limit of a time range in which the packet should arrive at the destination device.

8. A relay program used in a network relay device, the network relay device constitutes a network for relaying packets; The relay program Computer, a receiving unit that receives the packet addressed to a destination device; an acquisition unit that acquires, from the packet received by the receiving unit, upper arrival limit information indicating a deadline for the packet to reach the destination device and lower arrival limit information indicating a lower limit of a time range in which the packet should reach the destination device; a transmitting unit that performs a transmitting process to transmit the packet received by the receiving unit or a packet based on the packet received by the receiving unit; It is a program to function as A relay program in which the transmitting unit performs priority control in the transmission process based on the upper limit information acquired by the acquiring unit, and waits to transmit the packet based on the lower limit information acquired by the acquiring unit.

9. A packet transmission program used in a network transmission device, Computer, a generating unit that generates a packet to be transmitted to a destination device, the packet including upper limit information indicating a deadline for the packet to reach the destination device; a transmitting unit that transmits the packet generated by the generating unit to the destination device via a network; It is a program to function as The packet transmission program, wherein the generation unit generates the packet further including arrival lower limit information indicating a lower limit of a time range in which the packet should arrive at the destination device.

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