Communication device, communication system, method for identifying packet loss, and program for identifying packet loss

Abstract

To appropriately identify the occurrence of packet loss, while reducing the load associated with preprocessing required to identify the occurrence of the packet loss.SOLUTION: A communication device 2 transmits communication packets to a destination device using multiple routes and receives acknowledgement packets for the communication packets from the destination device. The communication device 2 includes a sequence information acquisition unit 9 that acquires sequence information of communication packets of a communication flow, a transmission order correspondence information storage unit 10 that stores, as transmission order correspondence information, a correspondence between the transmission order of the communication packets for each route and the sequence information of the communication packets acquired by the sequence information acquisition unit, an acknowledgement information acquisition unit 11 that acquires acknowledgement information indicating the delivery status of the communication packets, and a packet loss determination unit 12 that determines whether or not a packet loss has occurred based on the transmission order correspondence information stored in the transmission order correspondence information storage unit and the acknowledgement information acquired by the acknowledgement information acquisition unit.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a communication device, a communication system, a method for identifying packet loss, and a program for identifying packet loss. [Background technology]

[0002] In packet communication, a communication device transmits a communication packet to a destination device, and when the destination device receives the communication packet from the communication device, it transmits a delivery confirmation packet for the communication packet to the communication device. For example, Patent Document 1 discloses a technique in which, when a communication device transmits a communication packet to a destination device using multiple routes, sequence information for each route and sequence information of the communication packet for each communication flow are added, and whether or not a packet loss has occurred is determined based on the sequence information for each route. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4497322 Summary of the Invention [Problem to be solved by the invention]

[0004] In the method disclosed in Patent Document 1, it is necessary to add sequence information for each path and sequence information for communication packets for each communication flow in order to determine whether a packet loss has occurred. Therefore, there is a problem that the load of pre-processing for identifying the occurrence of packet loss is large because two types of sequence information are added.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a communication device, a communication system, a method for identifying packet loss, and a program for identifying packet loss that can appropriately identify the occurrence of packet loss while reducing the load associated with pre-processing for identifying the occurrence of packet loss. [Means for solving the problem]

[0006] According to the invention recited in claim 1, communication packets are transmitted to a destination device using multiple routes, and a delivery confirmation packet for the communication packets is received from the destination device. A sequence information acquisition unit (9) acquires sequence information of the communication packets of a communication flow. A transmission order correspondence information storage unit (10) stores, for each route, a correspondence between the transmission order of the communication packets and the sequence information of the communication packets acquired by the sequence information acquisition unit as transmission order correspondence information. A delivery confirmation information acquisition unit (11) acquires delivery confirmation information indicating a delivery status of the communication packets. A packet loss determination unit (12) determines whether or not a packet loss has occurred based on the transmission order correspondence information stored in the transmission order correspondence information storage unit and the delivery confirmation information acquired by the delivery confirmation information acquisition unit.

[0007] The correspondence between the transmission order of communication packets for each route and the sequence information of the communication packets is stored as transmission order correspondence information, and whether or not a packet loss has occurred is determined based on the stored transmission order correspondence information and delivery confirmation information indicating the delivery status of the communication packets. The occurrence of a packet loss can be identified without the need to assign two types of sequence information, that is, sequence information for each route and sequence information for the communication packets for each communication flow. This makes it possible to appropriately identify the occurrence of a packet loss while suppressing the load associated with pre-processing for identifying the occurrence of a packet loss. [Brief description of the drawings]

[0008] [Figure 1] A functional block diagram showing the overall configuration of a first embodiment. [Diagram 2] Flowchart showing packet loss determination processing [Diagram 3] Diagram explaining the occurrence of packet loss [Figure 4] Diagram explaining delivery confirmation information [Diagram 5]FIG. 13 illustrates a second embodiment and explains the occurrence of packet loss. [Figure 6] Diagram explaining delivery confirmation information [Figure 7] A functional block diagram showing the overall configuration of a third embodiment. [Figure 8] Flowchart showing packet loss determination processing [Figure 9] Diagram explaining the occurrence of packet loss [Figure 10] Diagram explaining delivery confirmation information [Figure 11] A functional block diagram showing the overall configuration of a fourth embodiment. [Figure 12] Flowchart showing packet loss determination processing [Figure 13] Diagram explaining the occurrence of packet loss [Figure 14] Diagram explaining delivery confirmation information [Figure 15] A functional block diagram showing the overall configuration of a fifth embodiment. [Figure 16] Diagram explaining the occurrence of packet loss [Figure 17] Diagram explaining delivery confirmation information DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a number of embodiments will be described with reference to the drawings. Note that in the subsequent embodiments, the description of the same contents as in the preceding embodiments may be omitted.

[0010] (First embodiment) The first embodiment will be described with reference to Fig. 1 to Fig. 4. As shown in Fig. 1, a communication system 1 is configured such that a communication node 2 (corresponding to a communication device) and a destination node 3 (corresponding to a destination device) can communicate data via a wireless line. The data communication between the communication node 2 and the destination node 3 is data communication conforming to the communication protocol TCP / IP (Transmission Control Protocol / Internet Protocol). The communication node 2 transmits a communication packet to the destination node 3 via a wireless line. When the destination node 3 receives a communication packet from the communication node 2, it transmits a delivery confirmation packet for the received communication packet to the communication node 2 via a wireless line. Note that the communication node 2 and the destination node 3 may be configured to be able to communicate data via a base station, and the communication node 2 and the base station may communicate data via a wireless line, and the destination node 3 and the base station may communicate data via a wired line.

[0011] The communication node 2 includes a control unit 4 that controls the operation of the entire node. The control unit 4 is mainly configured with a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and I / O (Input / Output), etc. The functions provided by the control unit 4 can be provided by software recorded in a physical memory device and a computer that executes the software, software only, hardware only, or a combination of these. For example, when the control unit 4 is provided by an electronic circuit that is hardware, it can be provided by a digital circuit including a large number of logic circuits or an analog circuit. When the control unit 4 executes a program stored in a non-transitive physical recording medium, a process corresponding to the program is executed, and a method corresponding to the program is executed.

[0012] The control unit 4 includes, for each function, a packet generation unit 5, a vehicle inside communication interface unit 6 (corresponding to a packet receiving unit), a first vehicle outside communication interface unit 7, a second vehicle outside communication interface unit 8, a sequence information acquisition unit 9, a transmission order correspondence information storage unit 10, a delivery confirmation information acquisition unit 11, and a packet loss determination unit 12. Each of these units 5 to 12 executes a packet loss identification program and performs a packet loss identification method.

[0013] The packet generation unit 5 generates a communication packet in accordance with the execution of the application by the control unit 4, and outputs the generated communication packet to the sequence information acquisition unit 9. When the vehicle inside communication interface unit 6 receives a communication packet from an external node 13 (corresponding to an external device), it outputs the received communication packet to the sequence information acquisition unit 9.

[0014] The first vehicle exterior communication interface unit 7 performs data communication conforming to a communication protocol of a WiFi (registered trademark) line as a path 1, for example, transmits a communication packet to a destination node 3 via the WiFi line, and receives a delivery confirmation packet for the communication packet from the destination node 3 via the WiFi line. The second vehicle exterior communication interface unit 8 performs data communication conforming to a communication protocol of a cellular line as a path 2, for example, transmits a communication packet to a destination node 3 via the cellular line, and receives a delivery confirmation packet for the communication packet from the destination node 3 via the cellular line. Note that the combination of path 1 and path 2 is not limited to the combination of a WiFi line and a cellular line, and may be any combination of lines having different communication protocols.

[0015] When two routes, route 1 and route 2, are prepared as transmission routes for communication packets, the order in which communication packets are sent from the communication node 2 may not match the order in which communication packets are received by the destination node 3 due to differences in line delays caused by the communication conditions between the routes. That is, if the communication conditions of route 1 are relatively good and the communication conditions of route 2 are relatively poor, the communication packet transmitted later from the communication node 2 to route 1 may be received by the destination node 3 earlier than the communication packet transmitted earlier from the communication node 2 to route 2. Conversely, if the communication conditions of route 1 are relatively poor and the communication conditions of route 2 are relatively good, the communication packet transmitted later from the communication node 2 to route 2 may be received by the destination node 3 earlier than the communication packet transmitted earlier from the communication node 2 to route 1.

[0016] The sequence information acquisition unit 9 acquires sequence numbers (corresponding to sequence information) of communication packets and delivery confirmation packets whose processing has been scheduled in advance. The sequence numbers are information that can specify the transmission order of the communication packets and the reception order of the delivery confirmation packets, respectively. As long as the transmission order of the communication packets and the reception order of the delivery confirmation packets can be specified, information other than the sequence numbers may be used instead of the sequence numbers.

[0017] When the sequence number of a communication packet is acquired by the sequence information acquisition unit 9, the transmission order correspondence information storage unit 10 stores the correspondence between the transmission order of the communication packets for each route and the acquired sequence number of the communication packet as a transmission order correspondence table (corresponding to transmission order correspondence information).

[0018] The delivery confirmation information acquisition unit 11 acquires delivery confirmation information indicating the delivery status of the communication packet by a delivery confirmation packet. When the delivery confirmation information acquisition unit 11 acquires the delivery confirmation information, the packet loss determination unit 12 determines whether or not a packet loss has occurred based on the transmission order correspondence table stored in the transmission order correspondence information storage unit 10 and the acquired delivery confirmation information. That is, the packet loss determination unit 12 determines whether or not the delivery confirmation information matches the transmission order correspondence table. When the packet loss determination unit 12 determines that the delivery confirmation information matches the transmission order correspondence table, it determines that no packet loss has occurred. On the other hand, when the packet loss determination unit 12 determines that the delivery confirmation information does not match the transmission order correspondence table, it determines that a packet loss has occurred.

[0019] Next, the operation of the above-mentioned configuration will be described with reference to Fig. 2 to Fig. 4. When a transmission request for a communication packet occurs, the control unit 4 performs a communication packet transmission process for transmitting the communication packet of the transmission request to the destination node 3, and also performs a packet loss determination process for determining whether or not the communication packet of the transmission request has been lost.

[0020] When the control unit 4 starts the packet loss determination process, it acquires the sequence number of the communication packet that is the target of the transmission request (S1, which corresponds to the sequence information acquisition procedure).When the control unit 4 transmits the communication packet to the destination node 3, it stores the correspondence between the acquired sequence number of the communication packet and the transmission order on the route used for transmitting the communication packet as a transmission order correspondence table (S2, which corresponds to the transmission order correspondence information storage procedure).

[0021] When the destination node 3 receives a communication packet from the communication node 2, it transmits to the communication node 2 a delivery confirmation packet for the received communication packet, and also transmits to the communication node 2 delivery confirmation information indicating the delivery status of the communication packet.

[0022] When the control unit 4 receives the acknowledgement packet and the acknowledgement information from the destination node 3, it acquires the sequence number of the received acknowledgement packet and acquires the acknowledgement information (S3, which corresponds to the acknowledgement information acquisition procedure).The control unit 4 compares the acquired acknowledgement information with the transmission order correspondence table (S4), and determines whether the acknowledgement information matches the transmission order correspondence table (S5, which corresponds to the packet loss determination procedure).

[0023] If the control unit 4 determines that the delivery confirmation information matches the transmission order correspondence table (S5: YES), it determines that no packet loss has occurred (S6) and ends the packet loss determination process. On the other hand, if the control unit 4 determines that the delivery confirmation information does not match the transmission order correspondence table (S5: NO), it determines that a packet loss has occurred (S7) and ends the packet loss determination process.

[0024] 3, a case will be described in which a communication node 2 transmits communication packets with sequence numbers "1" to "3", and "6" to a destination node 3 via a route 1, and transmits communication packets with sequence numbers "4" to "5", and "7" to a destination node 3 via a route 2. In this case, the communication node 2 associates the transmission order "1" to "4" with the sequence numbers "1" to "3", and "6" as the transmission order correspondence table for route 1, and associates the transmission order "1" to "3" with the sequence numbers "4" to "5", and "7" as the transmission order correspondence table for route 2.

[0025] The communication node 2 transmits communication packets to the destination node 3 in the order of sequence numbers "1" to "7". However, as described above, due to differences in line delays caused by communication conditions between the paths, the transmission order of the communication packets from the communication node 2 may not match the reception order of the communication packets at the destination node 3. For example, if the communication conditions of path 1 are relatively good and the communication conditions of path 2 are relatively poor, the communication packet with sequence number "6" may be received by the destination node 6 before the communication packet with sequence number "4". When the destination node 3 receives the communication packet with sequence number "6" before the communication packet with sequence number "4", it transmits a delivery confirmation packet for the communication packet with sequence number "6" to the communication node 2 before transmitting a delivery confirmation packet for the communication packet with sequence number "4" to the communication node 2.

[0026] In this case, as shown in FIG. 4, the destination node 3 transmits a delivery confirmation packet for the communication packet with sequence number "6" to the communication node 2, and also transmits delivery confirmation information to the communication node 2 indicating that "communication packet up to sequence number "2" has been received, communication packets with sequence numbers "3" to "5" have not been received, and communication packet with sequence number "6" has been received."

[0027] When communication node 2 receives a delivery confirmation packet for the communication packet with sequence number "6" from destination node 3 and also receives delivery confirmation information, it determines from the received delivery confirmation information that communication packets with sequence numbers "3" to "5" have not been received. Here, communication node 2 does not determine that communication packets with sequence numbers "4" to "5" are lost, since they are on a different route from the communication packet with sequence number "6". On the other hand, communication node 2 determines that communication packet with sequence number "3" is lost, since it is on the same route as communication packet with sequence number "6".

[0028] That is, in the above situation, in a configuration that determines loss simply based on the order of sequence numbers, it determines that loss has occurred in communication packets with sequence numbers "3" to "5", resulting in unnecessary retransmission of sequence numbers "4" to "5". On the other hand, in this embodiment, it determines that loss has occurred only in communication packets with sequence number "3", so no retransmission of sequence numbers "4" to "5" occurs. By using the transmission order correspondence table, unnecessary redundant retransmission can be avoided without transmitting the sequence number for each communication flow to the destination node 3.

[0029] As described above, according to the first embodiment, the following advantageous effects can be obtained. In the communication node 2, it is determined whether or not a packet loss has occurred based on a transmission order correspondence table indicating the correspondence between the transmission order of communication packets and the sequence numbers of the communication packets for each route, and delivery confirmation information indicating the delivery status of the communication packets. It is possible to identify the occurrence of a packet loss without the need to assign two types of sequence information, that is, sequence information for each route and sequence information of the communication packets for each communication flow. This makes it possible to appropriately identify the occurrence of a packet loss while suppressing the load related to pre-processing for identifying the occurrence of a packet loss.

[0030] It is determined whether or not a packet loss has occurred for a communication packet generated by the communication node 2. The occurrence of a packet loss can be appropriately identified for communication packets generated by the communication node 2.

[0031] It is determined whether or not a packet loss has occurred for a communication packet received from the external node 13. For communication packets received from the external node 13, it is possible to appropriately identify the occurrence of a packet loss.

[0032] Second embodiment The second embodiment will be described with reference to Fig. 5 and Fig. 6. While the first embodiment is configured to target one communication flow, the second embodiment is configured to target multiple communication flows. The transmission order correspondence information storage unit 10 stores, for each route, the correspondence between the transmission order of communication packets, a flow ID (corresponding to flow identification information) that identifies the communication flow, and the sequence number of the communication packet as a transmission order correspondence table (corresponding to transmission order correspondence information).

[0033] 5, in the case of communication flow "a" to "c" in the communication node 2, a case will be described in which, for the communication flow "a", communication packets with sequence numbers "1" to "3", and "6" are transmitted to the destination node 3 via the route 1, and communication packets with sequence numbers "4" to "5", and "7" are transmitted to the destination node 3 via the route 2. In this case, the communication node 2 associates the transmission orders "1" to "3", and "5" with the sequence numbers "1" to "3", and "6" of the flow ID "a" as the transmission order correspondence table for the route 1, and associates the transmission order "1" to "2", and "4" with the sequence numbers "4" to "5", and "7" of the flow ID "a" as the transmission order correspondence table for the route 2.

[0034] When the destination node 3 receives a communication packet with sequence number "6" of flow ID "a" before the communication packet with sequence number "4" of flow ID "a", it transmits a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" to the communication node 2 before transmitting a delivery confirmation packet for the communication packet with sequence number "4" of flow ID "a" to the communication node 2.

[0035] As shown in FIG. 6, the destination node 3 transmits to the communication node 2 a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a", and also transmits to the communication node 2 delivery confirmation information indicating that "communication packet up to sequence number "2" of flow ID "a" has been received, communication packets with sequence numbers "3" to "5" of flow ID "a" have not been received, and communication packet with sequence number "6" of flow ID "a" has been received."

[0036] When the communication node 2 receives a delivery confirmation packet for the communication packet with sequence number "6" and flow ID "a" from the destination node 3 and also receives delivery confirmation information, it determines from the received delivery confirmation information that the communication packets with sequence numbers "3" to "5" and flow ID "a" have not been received. Here, the communication node 2 does not determine that the communication packets with sequence numbers "4" to "5" and flow ID "a" are lost, since they are on a different route from the communication packet with sequence number "6" and flow ID "a". On the other hand, the communication node 2 determines that the communication packet with sequence number "3" and flow ID "a" is lost, since it is on the same route as the communication packet with sequence number "6" and flow ID "a".

[0037] Even in a configuration that targets multiple communication flows, by using a transmission order correspondence table in the same manner as in the first embodiment, it is possible to avoid unnecessary redundant retransmissions without transmitting the sequence number for each communication flow to the destination node 3. Although the above has been exemplified for communication flow "a", the same applies to communication flow "b" and communication flow "c". Note that the number of communication flows is not limited to "3".

[0038] As described above, according to the second embodiment, the following advantageous effects can be obtained. In the configuration in which a plurality of communication flows "a" to "c" are targeted in the communication node 2, advantageous effects similar to those of the first embodiment can be obtained, and the occurrence of packet loss can be appropriately identified while suppressing the load related to pre-processing for identifying the occurrence of packet loss.

[0039] Third embodiment The third embodiment will be described with reference to Fig. 7 to Fig. 10. The third embodiment is configured such that a communication node functions as a relay node that transmits a communication packet received from a transmitting node (corresponding to a transmitting device) to a destination node.

[0040] As shown in Fig. 7, the communication system 21 is configured such that a communication node 22 (corresponding to a communication device) and destination nodes 23a to 23c (corresponding to destination devices) can communicate data with each other via a wireless line. In the communication node 22, the control unit 24 includes a packet generating unit 5, a vehicle inside communication interface unit 6, a first vehicle outside communication interface unit 7, a second vehicle outside communication interface unit 8, a sequence information acquiring unit 9, a transmission order correspondence information storage unit 10, a delivery confirmation information acquiring unit 11, and a packet loss determining unit 12, all of which are described in the first embodiment, as well as a delivery confirmation information reconstructing unit 25. When the packet loss determining unit 12 identifies that a packet loss has occurred, the delivery confirmation information reconstructing unit 25 reconstructs delivery confirmation information indicating the delivery status of the communication packet, and transmits the reconstructed delivery confirmation information to the transmitting node.

[0041] Next, the operation of the above-mentioned configuration will be described with reference to FIGS. The control unit 24 starts the packet loss determination process, performs S1 to S5 described in the first embodiment, and when it determines that the delivery confirmation information does not match the transmission order correspondence table (S5: NO) and identifies that packet loss has occurred (S7), it reconstructs the delivery confirmation information indicating the delivery status of the communication packet (S11), transmits the reconstructed delivery confirmation information to the transmitting node (S12), and terminates the packet loss determination process.

[0042] As shown in FIG. 9, a case will be described in which the communication node 22 relays a communication flow "a" from the transmitting node 26a to the destination node 23a, transmits a communication flow "b" to the destination node 23b, and relays a communication flow "c" from the transmitting node 26c to the destination node 23c. The communication node 22 transmits communication packets with sequence numbers "1" to "3" and "6" for the communication flow "a" to the destination node 23a via the route 1, and transmits communication packets with sequence numbers "4" to "5" and "7" to the destination node 23a via the route 2. In this case, the communication node 22 also associates the transmission orders "1" to "3" and "5" with the sequence numbers "1" to "3" and "6" of the flow ID "a" as the transmission order correspondence table for the route 1, as in the second embodiment, and associates the transmission orders "1" to "2" and "4" with the sequence numbers "4" to "5" and "7" of the flow ID "a" as the transmission order correspondence table for the route 2.

[0043] When the destination node 23a receives a communication packet with sequence number "6" of flow ID "a" before the communication packet with sequence number "4" of flow ID "a", it transmits a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" to the communication node 22 before transmitting a delivery confirmation packet for the communication packet with sequence number "4" of flow ID "a" to the communication node 22.

[0044] As shown in FIG. 10, the destination node 23a transmits a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" to the communication node 2, and also transmits delivery confirmation information to the communication node 22 indicating that "communication packet up to sequence number "2" of flow ID "a" has been received, communication packets with sequence numbers "3" to "5" of flow ID "a" have not been received, and communication packet with sequence number "6" of flow ID "a" has been received."

[0045] The communication node 22 receives a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" from the destination node 23a and also receives delivery confirmation information, and identifies the loss of the communication packet with sequence number "3" of flow ID "a". The communication node 22 changes and reconstructs the received delivery confirmation information to "communication packet up to sequence number "2" of flow ID "a" has been received, communication packet with sequence number "3" of flow ID "a" has not been received, and communication packet with sequence number "6" of flow ID "a" has been received", and transmits the reconstructed delivery confirmation information to the transmitting node 26a.

[0046] That is, if the acknowledgement information received from the destination node 23a is transmitted to the transmitting node 26a without being reconstructed, the transmitting node 26a will identify the communication packets with sequence numbers "3" to "5" of the flow ID "a" as lost, and unnecessary redundant retransmission will occur. In this embodiment, the acknowledgement information received from the destination node 23a is reconstructed and transmitted to the transmitting node 26a, thereby making it possible to prevent unnecessary redundant retransmission. The above is an example of the communication flow "a" from the transmitting node 26a, but the same applies to the communication flow "c" from the transmitting node 26c.

[0047] As described above, according to the third embodiment, the following advantageous effects can be obtained: When the communication node 22 functions as a relay node for transmitting communication packets received from the transmitting nodes 26a, 26c to the destination nodes 23a-23c, the communication node 22 reconstructs the delivery confirmation information received from the destination nodes 23a-23c and transmits it to the transmitting nodes 26a, 26c, thereby making it possible to prevent unnecessary redundant retransmission from the transmitting nodes 26a, 26c.

[0048] (Fourth embodiment) The fourth embodiment will be described with reference to Fig. 11 to Fig. 14. In the fourth embodiment, similarly to the third embodiment, a communication node functions as a relay node that transmits a communication packet received from a transmission node to a destination node.

[0049] As shown in Fig. 11, the communication system 31 is configured such that a communication node 32 (corresponding to a communication device) and destination nodes 23a to 23c (corresponding to destination devices) can communicate data with each other via a wireless line. In the communication node 32, the control unit 34 includes a packet retransmitting unit 35 in addition to the packet generating unit 5, the vehicle inside communication interface unit 6, the first vehicle outside communication interface unit 7, the second vehicle outside communication interface unit 8, the sequence information acquiring unit 9, the transmission order correspondence information storage unit 10, the delivery confirmation information acquiring unit 11, and the packet loss determining unit 12 described in the first embodiment. When the packet loss determining unit 12 identifies that a packet loss has occurred, the packet retransmitting unit 35 retransmits the communication packet identified as having the packet loss to the destination node.

[0050] Next, the operation of the above-mentioned configuration will be described with reference to FIGS. The control unit 34 starts the packet loss determination process, performs S1 to S5 described in the first embodiment, and when it determines that the delivery confirmation information does not match the transmission order correspondence table (S5: NO) and determines that a packet loss has occurred, it resends the communication packet in which the packet loss has been identified to the destination node (S21), and ends the packet loss determination process.

[0051] 13, in the communication node 32, as in the third embodiment, a case will be described in which a communication flow "a" from the transmitting node 26a is relayed and transmitted to the destination node 23a, a communication flow "b" is transmitted to the destination node 23b, and a communication flow "c" from the transmitting node 26c is relayed and transmitted to the destination node 23c. A buffer is provided for storing communication packets received from the transmitting nodes 26a and 26c, and communication packets to be transmitted are stored in the buffer even after the communication packets are transmitted to the destination nodes 23a to 26c.

[0052] The communication node 32 transmits communication packets with sequence numbers "1" to "3", and "6" for communication flow "a" to the destination node 23a via path 1, and transmits communication packets with sequence numbers "4" to "5", and "7" to the destination node 23a via path 2. In this case, similar to the second embodiment, the communication node 32 associates the transmission orders "1" to "3", and "5" with the sequence numbers "1" to "3", and "6" of the flow ID "a" as the transmission order correspondence table for path 1, and associates the transmission orders "1" to "2", and "4" with the sequence numbers "4" to "5", and "7" of the flow ID "a" as the transmission order correspondence table for path 2.

[0053] When the destination node 23a receives a communication packet with sequence number "6" of flow ID "a" before the communication packet with sequence number "4" of flow ID "a", it transmits a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" to the communication node 32 before transmitting a delivery confirmation packet for the communication packet with sequence number "4" of flow ID "a" to the communication node 32.

[0054] As shown in FIG. 14, the destination node 23a transmits a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" to the communication node 2, and also transmits delivery confirmation information to the communication node 32 indicating that "communication packet up to sequence number "2" of flow ID "a" has been received, communication packets with sequence numbers "3" to "5" of flow ID "a" have not been received, and communication packet with sequence number "6" of flow ID "a" has been received."

[0055] The communication node 32 receives a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" from the destination node 23a, and upon receiving delivery confirmation information, identifies the loss of the communication packet with sequence number "3" of flow ID "a." The communication node 22 retransmits the communication packet with sequence number "3" of flow ID "a" for which the packet loss has been identified, to the destination node 23a.

[0056] That is, if the delivery confirmation information received from the destination node 23a is transmitted as is to the transmitting node 26a, the transmitting node 26a will identify the communication packets with sequence numbers "3" to "5" of the flow ID "a" as lost, and unnecessary redundant retransmission will occur. In this embodiment, unnecessary redundant retransmission can be avoided by retransmitting the communication packet with sequence number "3" of the flow ID "a" in which the packet loss has been identified to the destination node 23a. Although the above is an example of the communication flow "a" from the transmitting node 26a, the same applies to the communication flow "c" from the transmitting node 26c.

[0057] As described above, according to the fourth embodiment, the following advantageous effects can be obtained: When the communication node 32 functions as a relay node that transmits communication packets received from the transmitting nodes 26a, 26c to the destination nodes 23a-23c, the communication packet identified as having a packet loss can be retransmitted to the destination node 23a, thereby making it possible to prevent unnecessary redundant retransmission from the transmitting nodes 26a, 26c.

[0058] Fifth embodiment The fifth embodiment will be described with reference to Fig. 15 to Fig. 17. The fifth embodiment is configured such that the destination node thins out and transmits delivery confirmation packets.

[0059] As shown in Fig. 15, a communication system 41 is configured so that a communication node 42 (corresponding to a communication device) and a destination node 43 (corresponding to a destination device) can communicate data via a wireless line. In the communication node 42, a control unit 44 has a configuration equivalent to the control unit 4 described in the first embodiment. The destination node 43 determines whether the communication flows are the same or not, and determines whether the sequence numbers are consecutive or not. During a period in which communication packets with the same communication flow and consecutive sequence numbers are being received, the destination node 43 thins out delivery confirmation packets and transmits them to the communication node 42.

[0060] When the destination node 43 receives the communication packet with sequence number "1" and flow ID "a", it transmits a delivery confirmation packet for the communication packet with sequence number "1" and flow ID "a" to the communication node 42. When the destination node 43 receives the communication packet with sequence number "2" and flow ID "a", the condition that the communication flow is the same as that of the communication packet with sequence number "1" and flow ID "a" and that the sequence numbers are consecutive is satisfied, so that the destination node 43 does not transmit a delivery confirmation packet for the communication packet with sequence number "2" and flow ID "a" to the communication node 42.

[0061] 16, a case will be described in which, for a communication flow "a", in the communication node 42, communication packets with sequence numbers "1" to "3", and "6" are transmitted to the destination node 23a via route 1, and communication packets with sequence numbers "4" to "5", and "7" are transmitted to the destination node 23a via route 2. In this case, as in the second embodiment, the communication node 42 associates the transmission orders "1" to "3", and "5" with the sequence numbers "1" to "3", and "6" of the flow ID "a" as the transmission order correspondence table for route 1, and associates the transmission orders "1" to "2", and "4" with the sequence numbers "4" to "5", and "7" of the flow ID "a" as the transmission order correspondence table for route 2.

[0062] When the destination node 43 receives a communication packet with sequence number "6" of flow ID "a" before the communication packet with sequence number "4" of flow ID "a", it transmits a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" to the communication node 42 before transmitting a delivery confirmation packet for the communication packet with sequence number "4" of flow ID "a" to the communication node 42.

[0063] 17, when the destination node 43 receives a communication packet with sequence number "1" of flow ID "b", the condition that the communication flow is the same as that of the communication packet with sequence number "2" of flow ID "a" and the sequence numbers are consecutive is not satisfied, so the destination node 43 transmits a delivery confirmation packet for the communication packet with sequence number "1" of flow ID "b" to the communication node 42. In this case, the destination node 43 transmits to the communication node 42 delivery confirmation information indicating that "the communication packet with sequence number "2" of flow ID "a" has been received, and the communication packet with sequence number "1" of flow ID "b" has been received."

[0064] When the communication node 42 receives a delivery confirmation packet for a communication packet with sequence number "1" and flow ID "b" from the destination node 43 and also receives delivery confirmation information, it identifies the loss of a communication packet with sequence number "3" and flow ID "a". That is, in the second to fourth embodiments, the communication node 42 can identify the loss of a communication packet with sequence number "3" and flow ID "a" only at the timing when it receives a delivery confirmation packet for a communication packet with sequence number "6" and flow ID "a" from the destination node 43. On the other hand, in this embodiment, it can identify the loss of a communication packet with sequence number "3" and flow ID "a" at the timing when it receives a delivery confirmation packet for a communication packet with sequence number "1" and flow ID "b" from the destination node 43.

[0065] As described above, according to the fifth embodiment, the following advantageous effects can be obtained. In a configuration in which the destination node 43 thins out and transmits delivery confirmation packets during a period in which communication packets having the same communication flow and consecutive sequence numbers are received, the communication node 42 can obtain the same effect as in the first embodiment, and can appropriately identify the occurrence of packet loss while reducing the load associated with pre-processing for identifying the occurrence of packet loss.

[0066] In addition to the claims, the present disclosure also includes the following inventions. [1] A communication device (2, 22, 32) that transmits a communication packet to a destination device using a plurality of routes and receives a delivery confirmation packet for the communication packet from the destination device, a sequence information acquisition unit (9) for acquiring sequence information of the communication packets of the communication flow; a transmission order correspondence information storage unit (10) that stores, for each path, a correspondence between the transmission order of the communication packets and the sequence information of the communication packets acquired by the sequence information acquisition unit as transmission order correspondence information; a delivery confirmation information acquisition unit (11) for acquiring delivery confirmation information indicating a delivery status of the communication packet; a packet loss determination unit (12) that determines whether or not a packet loss has occurred based on the transmission order correspondence information stored in the transmission order correspondence information storage unit and the delivery confirmation information acquired by the delivery confirmation information acquisition unit.

[0067] [2] The communication device described in [1], wherein the transmission order correspondence information storage unit stores, for each route, a correspondence between the transmission order of the communication packets, flow identification information that identifies a communication flow, and sequence information of the communication packets acquired by the sequence information acquisition unit as the transmission order correspondence information.

[0068] [3] A relay device functions as a relay device that transmits the communication packet received from the transmitting device to the destination device; The communication device according to [1], further comprising a delivery confirmation information reconstructing unit (25) that reconstructs the delivery confirmation information acquired by the delivery confirmation information acquisition unit when a packet loss is identified by the packet loss determination unit, and transmits the reconstructed delivery confirmation information to the transmitting device.

[0069] [4] A relay device functions as a relay device that transmits the communication packet received from the transmitting device to the destination device; The communication device according to [1], further comprising a packet retransmission unit (35) that, when a packet loss is identified by the packet loss determination unit, retransmits the communication packet for which the packet loss is identified to the destination device.

[0070] [5] A packet generating unit (5) for generating packets, The communication device according to claim 1, wherein the sequence information acquisition unit acquires sequence information of the communication packet generated by the packet generation unit.

[0071] [6] A packet receiving unit (6) for receiving the communication packet from an external device, The communication device according to any one of claims [1] to [5], wherein the sequence information acquisition unit acquires sequence information of the communication packet received by the packet receiving unit from the external device.

[0072] (Other embodiments) Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0073] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0074] In the drawing, 1, 21, 31, and 41 are communication systems, 2, 22, 32, and 42 are communication nodes (communication devices), 3, 23a to 23c, and 43 are destination nodes (destination devices), 4, 24, 34, and 44 are control units, 5 is a packet generation unit, 6 is a vehicle inside communication interface unit (packet receiving unit), 10 is a transmission order correspondence information storage unit, 11 is a delivery confirmation information acquisition unit, 12 is a packet loss determination unit, 25 is a delivery confirmation information reconstruction unit, and 35 is a packet retransmission unit.

Claims

1. A communication device (2, 22, 32) that transmits a communication packet to a destination device using a plurality of routes and receives a delivery confirmation packet for the communication packet from the destination device, A sequence information acquisition unit (9) for acquiring sequence information of the communication packets of a communication flow; a transmission order correspondence information storage unit (10) that stores, for each path, a correspondence between the transmission order of the communication packets and the sequence information of the communication packets acquired by the sequence information acquisition unit as transmission order correspondence information; a delivery confirmation information acquisition unit (11) for acquiring delivery confirmation information indicating a delivery status of the communication packet; A communication device comprising: a packet loss determination unit (12) that determines whether or not a packet loss has occurred based on the transmission order correspondence information stored in the transmission order correspondence information storage unit and the delivery confirmation information acquired by the delivery confirmation information acquisition unit.

2. The communication device according to claim 1, wherein the transmission order correspondence information storage unit stores, for each route, a correspondence between the transmission order of the communication packets, flow identification information that identifies the communication flow, and sequence information of the communication packets acquired by the sequence information acquisition unit as the transmission order correspondence information.

3. A relay device functions as a relay device that transmits the communication packet received from the transmitting device to the destination device; 2. The communication device according to claim 1, further comprising a delivery confirmation information reconstructing unit (25) that reconstructs the delivery confirmation information acquired by the delivery confirmation information acquisition unit when a packet loss is identified by the packet loss determination unit, and transmits the reconstructed delivery confirmation information to the transmitting device.

4. A relay device functions as a relay device that transmits the communication packet received from the transmitting device to the destination device; 2. The communication device according to claim 1, further comprising a packet retransmission unit (35) for retransmitting the communication packet for which a packet loss has been identified to the destination device when a packet loss has been identified by the packet loss determination unit.

5. A packet generating unit (5) for generating packets, The communication device according to claim 1 , wherein the sequence information acquisition unit acquires sequence information of the communication packet generated by the packet generation unit.

6. A packet receiving unit (6) for receiving the communication packet from an external device, The communication device according to claim 1 , wherein the sequence information acquisition unit acquires, from the external device, sequence information of the communication packet received by the packet receiving unit.

7. A communication system (41) including a communication device (42) that transmits a communication packet to a destination device using a plurality of routes, and a destination device (43) that transmits a delivery confirmation packet for the communication packet to the communication device, The communication device includes: A sequence information acquisition unit (9) for acquiring sequence information of the communication packets of a plurality of communication flows; a transmission order correspondence information storage unit (10) that stores, for each path, a correspondence between a transmission order of the communication packets, flow identification information for identifying the communication flow, and sequence information of the communication packets acquired by the sequence information acquisition unit as transmission order correspondence information; a delivery confirmation information acquisition unit (11) for acquiring delivery confirmation information indicating a delivery status of the communication packet; a packet loss determination unit (12) that determines whether or not a packet loss has occurred based on the transmission order correspondence information stored in the transmission order correspondence information storage unit and the delivery confirmation information acquired by the delivery confirmation information acquisition unit, The destination device: The communication system thins out and transmits the delivery confirmation packets during a period in which the communication packets having the same communication flow and continuous sequence information are being received.

8. A communication device (2, 22, 32) that transmits a communication packet to a destination device using a plurality of routes and receives a delivery confirmation packet for the communication packet from the destination device, a sequence information acquisition step of acquiring sequence information of the communication packets of a communication flow; a transmission order correspondence information storage step of storing, for each path, a correspondence between the transmission order of the communication packets and the sequence information of the communication packets acquired by the sequence information acquisition step as transmission order correspondence information; a delivery confirmation information acquisition step for acquiring delivery confirmation information indicating a delivery status of the communication packet; A method for identifying packet loss, comprising: a packet loss determination procedure for determining whether or not packet loss has occurred based on the transmission order correspondence information stored by the transmission order correspondence information storage procedure and the delivery confirmation information acquired by the delivery confirmation information acquisition procedure.

9. A control unit (4, 24, 34) of a communication device (2, 22, 32) that transmits a communication packet to a destination device using a plurality of routes and receives a delivery confirmation packet for the communication packet from the destination device, a sequence information acquisition step of acquiring sequence information of the communication packets of a communication flow; a transmission order correspondence information storage step of storing, for each path, a correspondence between the transmission order of the communication packets and the sequence information of the communication packets acquired by the sequence information acquisition step as transmission order correspondence information; a delivery confirmation information acquisition step for acquiring delivery confirmation information indicating a delivery status of the communication packet; a packet loss determination procedure for determining whether or not a packet loss has occurred based on the transmission order correspondence information stored by the transmission order correspondence information storage procedure and the delivery confirmation information acquired by the delivery confirmation information acquisition procedure.

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