Communication apparatus, communication system, packet loss determination method, and storage medium

Abstract

A communication device (2) transmits a communication packet to a destination device using a plurality of paths, and receives a delivery confirmation packet for the communication packet from the destination device. A communication device (2) is provided with: 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, the correspondence relationship between the transmission order of the communication packets for each path and the sequence information of the communication packets acquired by the sequence information acquisition unit; a delivery confirmation information acquisition unit (11) that acquires delivery confirmation information indicating the delivery status of the communication packet; and a packet loss determination unit (12) that determines whether or not a packet loss has occurred on the basis of 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.

Description

Technical Field

[0001] The invention relates to a communication device, a communication system, a method for determining packet loss and a persistent computer-readable storage medium. Background Art

[0002] In packet communication, a communication device sends a communication packet to a destination device, and when the destination device receives the communication packet from the communication device, it sends a delivery confirmation packet for the communication packet to the communication device. For example, Patent Document 1 discloses the following technology: In a communication device, when a communication packet is sent to a destination device using multiple paths, sequence information for each path and sequence information for the communication packet of each communication flow are given, and whether a packet loss has occurred is determined based on the sequence information for each path.

[0003] Patent Document 1: Japanese Patent No. 4497322

[0004] In the method disclosed in Patent Document 1, in order to determine whether packet loss has occurred, it is necessary to assign sequence information for each path and sequence information for communication packets for each communication flow. Therefore, there is a problem that the load involved in preprocessing for determining the occurrence of packet loss is large in accordance with the assignment of two types of sequence information. Summary of the invention

[0005] The present invention has been made in view of the above-mentioned situation, and an object of the present invention is to provide a communication device, a communication system, a method for determining packet loss, and a program for determining packet loss that can suppress the load involved in preprocessing for determining the occurrence of packet loss and can appropriately determine the occurrence of packet loss.

[0006] According to the present invention, communication packets are sent to a destination device using multiple paths, and delivery confirmation packets for the communication packets are received from the destination device. A sequence information acquisition unit acquires sequence information of the communication packets of a communication flow. A transmission order correspondence information storage unit stores the correspondence between the transmission order of the communication packets for each path 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 acquires delivery confirmation information indicating the delivery status of the communication packets. A packet loss determination unit determines whether 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 the communication packets and the sequence information of the communication packets for each path is stored as the transmission order correspondence information, and based on the stored transmission order correspondence information and the delivery confirmation information indicating the delivery status of the communication packets, it is determined whether the packet loss has occurred. The occurrence of the packet loss can be determined without providing two kinds of sequence information, the sequence information of each path and the sequence information of the communication packets of each communication flow. Thus, the load involved in the preprocessing for determining the occurrence of the packet loss can be suppressed, and the occurrence of the packet loss can be appropriately determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a functional block diagram showing the overall structure of the first embodiment.

[0009] Figure 2 This is a flowchart showing the packet loss determination process.

[0010] Figure 3 This is a diagram for explaining the occurrence of packet loss.

[0011] Figure 4 This is a diagram for explaining delivery confirmation information.

[0012] Figure 5 This is a diagram showing the second embodiment and explaining the occurrence of packet loss.

[0013] Figure 6 This is a diagram for explaining delivery confirmation information.

[0014] Figure 7 It is a functional block diagram showing the overall structure of the third embodiment.

[0015] Figure 8 This is a flowchart showing the packet loss determination process.

[0016] Fig. 9 This is a diagram for explaining the occurrence of packet loss.

[0017] Fig.10 This is a diagram for explaining delivery confirmation information.

[0018] Fig.11 It is a functional block diagram showing the overall structure of the fourth embodiment.

[0019] Fig.12 This is a flowchart showing the packet loss determination process.

[0020] Fig.13 This is a diagram for explaining the occurrence of packet loss.

[0021] Fig.14 This is a diagram for explaining delivery confirmation information.

[0022] Fig.15 It is a functional block diagram showing the overall structure of the fifth embodiment.

[0023] Fig.16 This is a diagram for explaining the occurrence of packet loss.

[0024] Fig.17 This is a diagram for explaining delivery confirmation information. DETAILED DESCRIPTION

[0025] Hereinafter, a plurality of embodiments will be described with reference to the drawings. In addition, in the subsequent embodiments, description of the same contents as the previous embodiments may be omitted.

[0026] (First Embodiment)

[0027] Reference Figures 1 to 4 The first embodiment is described. Figure 1 As shown, the communication system 1 is configured so that the communication node 2 (equivalent to the communication device) and the destination node 3 (equivalent to the destination device) can perform data communication via a wireless line. The data communication performed between the communication node 2 and the destination node 3 is data communication based on the communication protocol of TCP / IP (Transmission Control Protocol / Internet Protocol). The communication node 2 sends a communication packet to the destination node 3 via a wireless line. If the destination node 3 receives a communication packet from the communication node 2, it sends a delivery confirmation packet for the received communication packet to the communication node 2 via the wireless line. In addition, it can also be the following structure: the communication node 2 and the destination node 3 are configured so that data communication can be performed via a base station, the communication node 2 and the base station perform data communication via a wireless line, and the destination node 3 and the base station perform data communication via a wired line.

[0028] The communication node 2 has a control unit 4 that controls the overall operation of the node. The control unit 4 is mainly composed of a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an I / O (Input / Output). 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, only software, only hardware, or a combination thereof. For example, in the case where the control unit 4 is provided by an electronic circuit as hardware, it can be provided by a digital circuit or an analog circuit including a plurality of logic circuits. By executing a program stored in a non-migrating physical recording medium by the control unit 4, processing corresponding to the program is performed, and a method corresponding to the program is executed.

[0029] The control unit 4 includes, for each function, a packet generating unit 5, a vehicle interior communication interface unit 6 (equivalent to a packet receiving unit), a first vehicle exterior communication interface unit 7, a second vehicle exterior 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. Each of these units 5 to 12 executes a packet loss determination program and performs a packet loss determination method.

[0030] The packet generation unit 5 generates a communication packet according to the execution of the application by the control unit 4, and outputs the generated communication packet to the sequence information acquisition unit 9. The in-vehicle communication interface unit 6 outputs the received communication packet to the sequence information acquisition unit 9 when receiving a communication packet from the external node 13 (equivalent to an external device).

[0031] The first vehicle-exterior communication interface unit 7 performs data communication based on the communication protocol of the WiFi (registered trademark) line as path 1, sends a communication packet to the 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 based on the communication protocol of the cellular line as path 2, sends a communication packet to the 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. In addition, the combination of path 1 and path 2 is not limited to the combination of the WiFi line and the cellular line, and any combination of lines with different communication protocols is acceptable.

[0032] When two paths, path 1 and path 2, are prepared as transmission paths for communication packets, there may be a case where the transmission order of communication packets from communication node 2 and the reception order of communication packets to destination node 3 do not match due to the difference in line delay caused by the communication conditions between the paths. That is, if the communication condition of path 1 is relatively good and the communication condition of path 2 is relatively bad, there may be a case where a communication packet sent from communication node 2 to path 1 later is received by destination node 3 earlier than a communication packet sent from communication node 2 to path 2 earlier is received by destination node 3. On the contrary, if the communication condition of path 1 is relatively bad and the communication condition of path 2 is relatively good, there may be a case where a communication packet sent from communication node 2 to path 2 later is received by destination node 3 earlier than a communication packet sent from communication node 2 to path 1 earlier is received by destination node 3.

[0033] The sequence information acquisition unit 9 acquires the sequence numbers (equivalent to sequence information) of the communication packets and delivery confirmation packets that are pre-arranged for processing. The sequence number is information that can determine the order in which the communication packets are sent and the order in which the delivery confirmation packets are received. If the order in which the communication packets are sent and the order in which the delivery confirmation packets are received can be determined, it is not limited to the sequence number, and information other than the sequence number can also be used.

[0034] When the sequence information acquiring unit 9 acquires the sequence number of the communication packet, the sending order correspondence information storage unit 10 stores the correspondence between the sending order of the communication packets and the acquired sequence number of the communication packets for each path as a sending order correspondence table (equivalent to the sending order correspondence information).

[0035] The delivery confirmation information acquisition unit 11 acquires delivery confirmation information indicating the delivery status of the communication packet through the delivery confirmation packet. When the delivery confirmation information acquisition unit 11 acquires the delivery confirmation information, the packet loss determination unit 12 determines whether 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 the delivery confirmation information is consistent with the transmission order correspondence table. If the packet loss determination unit 12 determines that the delivery confirmation information is consistent with the transmission order correspondence table, it is determined that no packet loss has occurred. On the other hand, if the packet loss determination unit 12 determines that the delivery confirmation information is inconsistent with the transmission order correspondence table, it is determined that a packet loss has occurred.

[0036] Next, refer to Figures 2 to 4When a communication packet transmission request is generated, the control unit 4 performs a communication packet transmission process to transmit the communication packet of the transmission request to the destination node 3, and performs a packet loss determination process to determine whether the communication packet of the transmission request is lost.

[0037] When the control unit 4 starts the packet loss determination process, it obtains the sequence number of the communication packet that is the object of the transmission request (S1, equivalent to the sequence information acquisition step). 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 in the path used for transmitting the communication packet as a transmission order correspondence table (S2, equivalent to the transmission order correspondence information storage step).

[0038] When receiving a communication packet from the communication node 2 , the destination node 3 transmits a delivery confirmation packet for the received communication packet to the communication node 2 , and transmits delivery confirmation information indicating the delivery status of the communication packet to the communication node 2 .

[0039] When the control unit 4 receives the delivery confirmation packet and the delivery confirmation information from the destination node 3, it obtains the sequence number of the received delivery confirmation packet and obtains the delivery confirmation information (S3, equivalent to the delivery confirmation information obtaining step). The control unit 4 compares the transmission order correspondence table with the obtained delivery confirmation information (S4), and determines whether the delivery confirmation information is consistent with the transmission order correspondence table (S5, equivalent to the packet loss determination step).

[0040] If the control unit 4 determines that the delivery confirmation information is consistent with the transmission order correspondence table (S5: Yes), it is determined that no packet loss has occurred (S6), and the packet loss determination process is terminated. On the other hand, if the control unit 4 determines that the delivery confirmation information is inconsistent with the transmission order correspondence table (S5: No), it is determined that a packet loss has occurred (S7), and the packet loss determination process is terminated.

[0041] like Figure 3 As shown, the following situation is described: in communication node 2, communication packets with sequence numbers "1" to "3", "6" are sent to destination node 3 via path 1, and communication packets with sequence numbers "4" to "5", "7" are sent to destination node 3 via path 2. In this case, in communication node 2, a correspondence is established between the sending order "1" to "4" and the sequence numbers "1" to "3", "6" as a sending order correspondence table for path 1, and a correspondence is established between the sending order "1" to "3" and the sequence numbers "4" to "5", "7" as a sending order correspondence table for path 2.

[0042] Communication node 2 sends communication packets to destination node 3 in the order of sequence numbers "1" to "7", but as mentioned above, there may be a difference in line delay caused by the communication conditions between the paths, and the order of sending communication packets from communication node 2 and the order of receiving communication packets to destination node 3 may not be consistent. For example, if the communication condition of path 1 is relatively good, and the communication condition of path 2 is relatively bad, there may be a situation where the communication packet with sequence number "6" is received by destination node 6 before the communication packet with sequence number "4". If destination node 3 receives the communication packet with sequence number "6" before the communication packet with sequence number "4", it will send the delivery confirmation packet for the communication packet with sequence number "6" to communication node 2 before sending the delivery confirmation packet for the communication packet with sequence number "4" to communication node 2.

[0043] In this case, if Figure 4 As shown, the destination node 3 sends a delivery confirmation packet for the communication packet with sequence number "6" to the communication node 2, and sends a delivery confirmation information indicating that "the communication packet up to the sequence number "2" has been received, the communication packets with sequence numbers "3" to "5" have not been received, and the communication packet with sequence number "6" has been received" to the communication node 2.

[0044] If communication node 2 receives a delivery confirmation packet for the communication packet with sequence number "6" from destination node 3 and receives delivery confirmation information, it determines that the communication packets with sequence numbers "3" to "5" have not been received based on the received delivery confirmation information. Here, for the communication packets with sequence numbers "4" to "5", since they are on a different path from the communication packet with sequence number "6", communication node 2 does not determine that they are lost. On the other hand, for the communication packet with sequence number "3", since they are on the same path as the communication packet with sequence number "6", communication node 2 determines that they are lost.

[0045] That is, in the case of the above situation, in the structure that determines the loss only by the order of the sequence number, it is determined that the communication packets of sequence numbers "3" to "5" have been lost, so the retransmission of sequence numbers "4" to "5" that is not necessary is generated. On the other hand, in the present embodiment, it is determined that only the communication packet of sequence number "3" has been lost, so the retransmission of sequence numbers "4" to "5" is not generated. By using the transmission order correspondence table, it is possible to prevent unnecessary redundant retransmission without sending the sequence number of each communication flow to the destination node 3.

[0046] As described above, according to the first embodiment, the following effects can be obtained. In the communication node 2, based on the transmission order correspondence table indicating the correspondence between the transmission order of the communication packets and the sequence numbers of the communication packets for each path, and the delivery confirmation information indicating the delivery status of the communication packets, it is determined whether a packet loss has occurred. It is not necessary to assign two types of sequence information, namely, sequence information for each path and sequence information for the communication packets of each communication flow, to determine the occurrence of packet loss. As a result, the load involved in the preprocessing for determining the occurrence of packet loss can be suppressed, and the occurrence of packet loss can be appropriately determined.

[0047] It is determined whether or not packet loss has occurred with respect to the communication packet generated by the communication node 2. The communication packet generated by the communication node 2 can be targeted, and the occurrence of packet loss can be appropriately determined.

[0048] It is determined whether or not packet loss has occurred with respect to the communication packet received from the external node 13. The communication packet received from the external node 13 can be used as a target, and the occurrence of packet loss can be appropriately determined.

[0049] (Second Embodiment)

[0050] Reference Figure 5 to Figure 6 The second embodiment is described. The first embodiment is a structure that sets one communication flow as an object, whereas the second embodiment is a structure that sets multiple communication flows as objects. The transmission order correspondence information storage unit 10 stores the correspondence between the transmission order of communication packets for each path and the flow ID (equivalent to flow identification information) for identifying the communication flow and the sequence number of the communication packet as a transmission order correspondence table (equivalent to transmission order correspondence information).

[0051] like Figure 5 As shown, the following case is described: in the communication node 2, when the communication flows "a" to "c" are set as objects, for the communication flow "a", the communication packets with sequence numbers "1" to "3", "6" are sent to the destination node 3 through the path 1, and the communication packets with sequence numbers "4" to "5", "7" are sent to the destination node 3 through the path 2. In this case, the communication node 2 establishes a correspondence between the sending order "1" to "3", "5" and the sequence numbers "1" to "3", "6" of the flow ID "a" as the sending order correspondence table of the path 1, and establishes a correspondence between the sending order "1" to "2", "4" and the sequence numbers "4" to "5", "7" of the flow ID "a" as the sending order correspondence table of the path 2.

[0052] If destination node 3 receives the communication packet with sequence number “6” of flow ID “a” before the communication packet with sequence number “4” of flow ID “a”, it sends the delivery confirmation packet for the communication packet with sequence number “6” of flow ID “a” to communication node 2 before sending the delivery confirmation packet for the communication packet with sequence number “4” of flow ID “a” to communication node 2.

[0053] like Figure 6 As shown, the destination node 3 sends a delivery confirmation packet for the communication packet with sequence number "6" of the flow ID "a" to the communication node 2, and sends a delivery confirmation message indicating that "the communication packets up to the sequence number "2" of the flow ID "a" have been received, the communication packets with sequence numbers "3" to "5" of the flow ID "a" have not been received, and the communication packet with sequence number "6" of the flow ID "a" has been received." to the communication node 2.

[0054] If the communication node 2 receives a delivery confirmation packet for the communication packet with sequence number "6" of the flow ID "a" from the destination node 3 and receives the delivery confirmation information, it is determined based on the received delivery confirmation information that the communication packets with sequence numbers "3" to "5" of the flow ID "a" have not been received. Here, for the communication packets with sequence numbers "4" to "5" of the flow ID "a", since they are on a different path from the communication packet with sequence number "6" of the flow ID "a", the communication node 2 does not determine that they are lost. On the other hand, for the communication packet with sequence number "3" of the flow ID "a", since they are on the same path as the communication packet with sequence number "6" of the flow ID "a", the communication node 2 determines that it is lost.

[0055] In the configuration where multiple communication flows are used as the object, by using the transmission order correspondence table in the same manner as in the first embodiment, unnecessary redundant retransmission can be prevented without sending the sequence number of each communication flow to the destination node 3. In the above, the communication flow "a" is exemplified, but the same is true for the communication flow "b" and the communication flow "c". In addition, the number of communication flows is not limited to "3".

[0056] As described above, according to the second embodiment, the following effects can be obtained. In the communication node 2, even in the configuration in which a plurality of communication flows "a" to "c" are set as objects, the same effects as those of the first embodiment can be obtained, and the load involved in the preprocessing for determining the occurrence of packet loss can be suppressed, and the occurrence of packet loss can be appropriately determined.

[0057] (Third Embodiment)

[0058] Reference Figures 7 to 10The third embodiment is described below. The third embodiment is a configuration in which a communication node functions as a relay node that transmits a communication packet received from a transmission node (corresponding to a transmission device) to a destination node.

[0059] like Figure 7 As shown, the communication system 21 is configured so that the communication node 22 (equivalent to the communication device) and the destination nodes 23a to 23c (equivalent to the destination device) can perform data communication via a wireless line. In the communication node 22, the control unit 24 includes a delivery confirmation information reconstruction unit 25 in addition to the packet generation unit 5, the vehicle interior communication interface unit 6, the first vehicle exterior communication interface unit 7, the second vehicle exterior communication interface unit 8, the sequence information acquisition unit 9, the transmission order corresponding information storage unit 10, the delivery confirmation information acquisition unit 11, and the packet loss determination unit 12 described in the first embodiment. If the packet loss determination unit 12 determines that a packet loss has occurred, the delivery confirmation information reconstruction unit 25 reconstructs the delivery confirmation information indicating the delivery status of the communication packet and sends the reconstructed delivery confirmation information to the sending node.

[0060] Next, refer to Figures 8 to 10 The function of the above-mentioned structure will be described.

[0061] The control unit 24 starts the packet loss determination process and performs S1 to S5 described in the first embodiment. If it is determined that the delivery confirmation information is inconsistent with the sending order correspondence table (S5: No), it is determined that packet loss has occurred (S7), then the delivery confirmation information indicating the delivery status of the communication packet is reconstructed (S11), and the reconstructed delivery confirmation information is sent to the sending node (S12), and the packet loss determination process ends.

[0062] like Fig. 9 As shown, the following case is described: in the communication node 22, the communication flow "a" from the transmission node 26a is relayed and sent to the destination node 23a, the communication flow "b" is sent to the destination node 23b, and the communication flow "c" from the transmission node 26c is relayed and sent to the destination node 23c. For the communication flow "a", the communication node 22 sends the communication packets with sequence numbers "1" to "3" and "6" to the destination node 23a through the path 1, and sends the communication packets with sequence numbers "4" to "5" and "7" to the destination node 23a through the path 2. In this case, as in the second embodiment, the communication node 22 establishes a correspondence relationship between the transmission order "1" to "3" and "5" and the sequence numbers "1" to "3" and "6" of the flow ID "a" as the transmission order correspondence table of the path 1, and establishes a correspondence relationship between the transmission order "1" to "2" and "4" and the sequence numbers "4" to "5" and "7" of the flow ID "a" as the transmission order correspondence table of the path 2.

[0063] If the destination node 23a receives the communication packet with sequence number “6” of flow ID “a” before the communication packet with sequence number “4” of flow ID “a”, it sends the delivery confirmation packet for the communication packet with sequence number “6” of flow ID “a” to the communication node 22 before sending the delivery confirmation packet for the communication packet with sequence number “4” of flow ID “a” to the communication node 22.

[0064] like Fig.10 As shown, the destination node 23a sends a delivery confirmation packet for the communication packet with sequence number "6" of the flow ID "a" to the communication node 2, and sends a delivery confirmation message indicating that "the communication packets up to the sequence number "2" of the flow ID "a" have been received, the communication packets with sequence numbers "3" to "5" of the flow ID "a" have not been received, and the communication packet with sequence number "6" of the flow ID "a" has been received" to the communication node 22.

[0065] If the communication node 22 receives a delivery confirmation packet for the communication packet with sequence number "6" of the flow ID "a" from the destination node 23a and receives the delivery confirmation information, it determines that the communication packet with sequence number "3" of the flow ID "a" is lost. The communication node 22 changes the received delivery confirmation information and reconstructs it to "communication packets up to sequence number "2" of the flow ID "a" have been received, communication packets with sequence number "3" of the flow ID "a" have not been received, and communication packets with sequence number "6" of the flow ID "a" have been received", and sends the reconstructed delivery confirmation information to the sending node 26a.

[0066] That is, if the delivery confirmation information received from the destination node 23a is not reconstructed and sent to the sending node 26a as it is, the sending node 26a determines that the communication packets of the sequence numbers "3" to "5" of the flow ID "a" are lost, and unnecessary redundant retransmissions are generated. In this embodiment, by reconstructing the delivery confirmation information received from the destination node 23a and sending it to the sending node 26a, unnecessary redundant retransmissions can be prevented. The above example illustrates the communication flow "a" from the sending node 26a, but the same is true for the communication flow "c" from the sending node 26c.

[0067] As described above, according to the third embodiment, the following effects can be obtained. In the communication node 22, when functioning as a relay node that transmits communication packets received from the transmission nodes 26a and 26c to the destination nodes 23a to 23c, by reconstructing the delivery confirmation information received from the destination nodes 23a to 23c and transmitting it to the transmission nodes 26a and 26c, unnecessary redundant retransmissions from the transmission nodes 26a and 26c can be prevented.

[0068] (Fourth Embodiment)

[0069] Reference Figures 11 to 14 A fourth embodiment will be described. 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.

[0070] like Fig.11 As shown, the communication system 31 is configured so that the communication node 32 (equivalent to the communication device) and the destination nodes 23a to 23c (equivalent to the destination device) can perform data communication via a wireless line. In the communication node 32, the control unit 34 includes a packet retransmission unit 35 in addition to the packet generation unit 5, the vehicle interior communication interface unit 6, the first vehicle exterior communication interface unit 7, the second vehicle exterior communication interface unit 8, the sequence information acquisition unit 9, the transmission order corresponding information storage unit 10, the delivery confirmation information acquisition unit 11, and the packet loss determination unit 12 described in the first embodiment. If the packet loss determination unit 12 determines that a packet loss has occurred, the packet retransmission unit 35 retransmits the communication packet in which the packet loss is determined to have occurred to the destination node.

[0071] Next, refer to Figure 12 to Figure 14 The function of the above-mentioned structure will be described.

[0072] The control unit 34 starts the packet loss determination process and performs S1 to S5 described in the first embodiment. If it is determined that the delivery confirmation information is inconsistent with the sending order correspondence table (S5: No), it is determined that packet loss has occurred, and the communication packet that determines the packet loss is resent to the destination node (S21), and the packet loss determination process ends.

[0073] like Fig.13As shown, the following situation is described: in the communication node 32, similarly to the third embodiment, the communication flow "a" from the sending node 26a is relayed and sent to the destination node 23a, the communication flow "b" is sent to the destination node 23b, and the communication flow "c" from the sending node 26c is relayed and sent to the destination node 23c. A buffer is provided for accumulating the communication packets received from the sending nodes 26a and 26c, and after the communication packets are sent to the destination nodes 23a to 26c, the communication packets to be sent are also accumulated in the buffer.

[0074] For the communication flow "a", the communication node 32 sends the communication packets with sequence numbers "1" to "3" and "6" to the destination node 23a through the path 1, and sends the communication packets with sequence numbers "4" to "5" and "7" to the destination node 23a through the path 2. In this case, as in the second embodiment, the communication node 32 establishes a correspondence between the sending order "1" to "3" and "5" and the sequence numbers "1" to "3" and "6" of the flow ID "a" as a sending order correspondence table for path 1, and establishes a correspondence between the sending order "1" to "2" and "4" and the sequence numbers "4" to "5" and "7" of the flow ID "a" as a sending order correspondence table for path 2.

[0075] If the destination node 23a receives the communication packet with sequence number “6” of flow ID “a” before the communication packet with sequence number “4” of flow ID “a”, it sends the delivery confirmation packet for the communication packet with sequence number “6” of flow ID “a” to the communication node 32 before sending the delivery confirmation packet for the communication packet with sequence number “4” of flow ID “a” to the communication node 32.

[0076] like Fig.14 As shown, the destination node 23a sends a delivery confirmation packet for the communication packet with sequence number "6" of flow ID "a" to the communication node 2, and sends a delivery confirmation message indicating that "the communication packets up to sequence number "2" of flow ID "a" have been received, the communication packets with sequence numbers "3" to "5" of flow ID "a" have not been received, and the communication packet with sequence number "6" of flow ID "a" has been received" to the communication node 32.

[0077] When the communication node 32 receives the delivery confirmation packet for the communication packet with sequence number "6" of the flow ID "a" from the destination node 23a and receives the delivery confirmation information, it is determined that the communication packet with sequence number "3" of the flow ID "a" is lost. The communication node 22 retransmits the communication packet with sequence number "3" of the flow ID "a" for which the packet loss is determined to be, to the destination node 23a.

[0078] That is, if the delivery confirmation information received from the destination node 23a is sent to the sending node 26a as it is, the sending node 26a determines that the communication packets with sequence numbers "3" to "5" of the flow ID "a" are lost, and unnecessary redundant retransmissions occur. In this embodiment, by retransmitting the communication packet with sequence number "3" of the flow ID "a" determined to be lost to the destination node 23a, unnecessary redundant retransmissions can be prevented. The above example illustrates the communication flow "a" from the sending node 26a, but the same is true for the communication flow "c" from the sending node 26c.

[0079] As described above, according to the fourth embodiment, the following effects can be obtained. In the communication node 32, when functioning as a relay node that transmits communication packets received from the sending nodes 26a and 26c to the destination nodes 23a to 23c, by retransmitting the communication packet that has been determined to be lost to the destination node 23a, unnecessary redundant retransmissions from the sending nodes 26a and 26c can be prevented.

[0080] (Fifth Embodiment)

[0081] Reference Figures 15 to 17 The fifth embodiment will be described. The fifth embodiment is a configuration in which a destination node transmits delivery confirmation packets sparsely.

[0082] like Fig.15 As shown, the communication system 41 is configured so that a communication node 42 (equivalent to a communication device) and a destination node 43 (equivalent to a destination device) can perform data communication via a wireless line. In the communication node 42, the control unit 44 is a structure equivalent to the control unit 4 described in the first embodiment. The destination node 43 determines whether the communication flows are the same and whether the sequence numbers are continuous. During the reception of communication packets with the same communication flows and continuous sequence numbers, sparse delivery confirmation packets are sent to the communication node 42.

[0083] If the destination node 43 receives the communication packet with the sequence number "1" of the flow ID "a", the delivery confirmation packet for the communication packet with the sequence number "1" of the flow ID "a" is sent to the communication node 42. If the destination node 43 receives the communication packet with the sequence number "2" of the flow ID "a", the conditions that the communication flows are the same and the sequence numbers are continuous are satisfied with respect to the communication packet with the sequence number "1" of the flow ID "a", and therefore the delivery confirmation packet for the communication packet with the sequence number "2" of the flow ID "a" is not sent to the communication node 42.

[0084] like Fig.16As shown, the following case is described: in the communication node 42, for the communication flow "a", the communication packets with sequence numbers "1" to "3", "6" are sent to the destination node 23a through the path 1, and the communication packets with sequence numbers "4" to "5", "7" are sent to the destination node 23a through the path 2. In this case, as in the second embodiment, the communication node 42 establishes a correspondence between the sending order "1" to "3", "5" and the sequence numbers "1" to "3", "6" of the flow ID "a" as the sending order correspondence table of the path 1, and establishes a correspondence between the sending order "1" to "2", "4" and the sequence numbers "4" to "5", "7" of the flow ID "a" as the sending order correspondence table of the path 2.

[0085] If the destination node 43 receives the communication packet with sequence number “6” of flow ID “a” before the communication packet with sequence number “4” of flow ID “a”, it sends the delivery confirmation packet for the communication packet with sequence number “6” of flow ID “a” to the communication node 42 before sending the delivery confirmation packet for the communication packet with sequence number “4” of flow ID “a” to the communication node 42.

[0086] like Fig.17 As shown, if the destination node 43 receives the communication packet with sequence number "1" of the flow ID "b", the condition that the communication flow is the same and the sequence number is continuous does not hold true for the communication packet with sequence number "2" of the flow ID "a", so the destination node 43 sends the delivery confirmation packet for the communication packet with sequence number "1" of the flow ID "b" to the communication node 42. In this case, the destination node 43 sends the delivery confirmation information indicating that "the communication packet with sequence number "2" of the flow ID "a" has been received, and the communication packet with sequence number "1" of the flow ID "b" has been received".

[0087] If the communication node 42 receives a delivery confirmation packet for the communication packet with sequence number "1" of the flow ID "b" from the destination node 43 and receives the delivery confirmation information, the loss of the communication packet with sequence number "3" of the flow ID "a" is determined. That is, in the second to fourth embodiments, the loss of the communication packet with sequence number "3" of the flow ID "a" can be determined only at the timing of receiving the delivery confirmation packet for the communication packet with sequence number "6" of the flow ID "a" from the destination node 43. On the other hand, in the present embodiment, the loss of the communication packet with sequence number "3" of the flow ID "a" can be determined at the timing of receiving the delivery confirmation packet for the communication packet with sequence number "1" of the flow ID "b" from the destination node 43.

[0088] As described above, according to the fifth embodiment, the following effects can be obtained.

[0089] In a structure in which the destination node 43 sparsely sends delivery confirmation packets while receiving communication packets with the same communication flow and consecutive sequence numbers, in the communication node 42, the same effect as the first embodiment can be obtained, the load involved in the preprocessing for determining the occurrence of packet loss can be suppressed, and the occurrence of packet loss can be appropriately determined.

[0090] The present disclosure includes the following inventions in addition to the description of the claims. [1]

[0092] A communication device (2, 22, 32) transmits a communication packet to a destination device using a plurality of paths, and receives a delivery confirmation packet for the communication packet from the destination device, wherein the communication device comprises:

[0093] A sequence information acquisition unit (9) for acquiring sequence information of the communication packets of the communication flow;

[0094] a transmission order correspondence information storage unit (10) for storing, as transmission order correspondence information, a correspondence relationship between the transmission order of the communication packets for each path and the sequence information of the communication packets acquired by the sequence information acquisition unit;

[0095] A delivery confirmation information acquisition unit (11) acquires delivery confirmation information indicating a delivery status of the communication packet; and

[0096] A packet loss determination unit (12) determines whether 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]

[0098] A communication device according to [1], wherein:

[0099] The transmission order correspondence information storage unit stores, as the transmission order correspondence information, a correspondence relationship between the transmission order of the communication packets for each path, flow identification information for identifying a communication flow, and sequence information of the communication packets acquired by the sequence information acquisition unit. [3]

[0101] A communication device according to [1], wherein:

[0102] The communication device functions as a relay device that transmits the communication packet received from the transmission device to the destination device.

[0103] The communication device comprises a delivery confirmation information reconstruction unit (25) which, when the packet loss determination unit determines that a packet is lost, reconstructs the delivery confirmation information acquired by the delivery confirmation information acquisition unit and sends the reconstructed delivery confirmation information to the sending device. [4]

[0105] A communication device according to [1], wherein:

[0106] The communication device functions as a relay device that transmits the communication packet received from the transmission device to the destination device.

[0107] The communication device includes a packet retransmission unit (35) which, when the packet loss determination unit determines that a packet loss has occurred, retransmits the communication packet in which the packet loss has been determined to the destination device. [5]

[0109] A communication device according to any one of [1] to [4], wherein:

[0110] The communication device comprises a packet generating unit (5) for generating packets.

[0111] The sequence information acquisition unit acquires the sequence information of the communication packet generated by the packet generation unit. [6]

[0113] A communication device according to any one of [1] to [5], wherein:

[0114] The communication device comprises a packet receiving unit (6) for receiving the communication packet from an external device.

[0115] The sequence information acquisition unit acquires sequence information of the communication packet received by the packet reception unit from the external device.

[0116] (Other Embodiments)

[0117] The present disclosure is described based on the embodiments, but it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure also includes various modifications and variations within the scope of equality. In addition, various combinations and methods, further including other combinations and methods of only one element, more than one element, or less than one element, also fall within the scope and scope of thought of the present disclosure.

[0118] The control unit and method described in the present disclosure may also be implemented by a special-purpose computer, which is provided by constituting a processor and a memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and method described in the present disclosure may also be implemented by a special-purpose computer, which is provided by constituting a processor composed of one or more special-purpose hardware logic circuits. Alternatively, the control unit and method described in the present disclosure may also be implemented by one or more special-purpose computers, which are constituted by a combination of a processor and a memory programmed to perform one or more functions and a processor composed of one or more hardware logic circuits. In addition, a computer program may also be stored as an instruction executed by a computer in a non-migratable tangible recording medium that can be read by a computer.

Claims

1. A communication device that transmits a communication packet to a destination device using a plurality of paths and receives a delivery confirmation packet for the communication packet from the destination device, wherein: The communication device comprises: A sequence information acquisition unit, which acquires sequence information of the communication packets of the communication flow; a transmission order correspondence information storage unit 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 that acquires delivery confirmation information indicating a delivery status of the communication packet; as well as The packet loss determination unit determines whether or not 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, as the transmission order correspondence information, a correspondence relationship between the transmission order of the communication packets, flow identification information identifying the communication flow, and sequence information of the communication packets acquired by the sequence information acquisition unit for each path.

3. The communication device according to claim 1, wherein: The communication device functions as a relay device that transmits the communication packet received from the transmission device to the destination device. The communication device includes a delivery confirmation information reconstruction unit. When the packet loss determination unit determines that a packet is lost, the delivery confirmation information reconstruction unit reconstructs the delivery confirmation information acquired by the delivery confirmation information acquisition unit and sends the reconstructed delivery confirmation information to the sending device.

4. The communication device according to claim 1, wherein: The communication device functions as a relay device that transmits the communication packet received from the transmission device to the destination device. The communication device includes a packet retransmission unit, and when the packet loss determination unit specifies a packet loss, the packet retransmission unit retransmits the communication packet in which the packet loss is specified to the destination device.

5. The communication device according to claim 1, wherein: The communication device includes a packet generating unit for generating packets. The sequence information acquisition section acquires sequence information of the communication packet generated by the packet generation section.

6. The communication device according to any one of claims 1 to 5, wherein: The communication device includes a packet receiving unit for receiving the communication packet from an external device. The sequence information acquisition section acquires sequence information of the communication packet received by the packet reception section from the external device.

7. A communication system comprising a communication device for sending a communication packet to a destination device using a plurality of paths and a destination device for sending a delivery confirmation packet for the communication packet to the communication device, wherein: The communication device comprises: A sequence information acquisition unit, which acquires sequence information of the communication packets of a plurality of communication flows; a transmission order correspondence information storage unit that stores, for each path, a correspondence between the transmission order of the communication packets and the flow identification information identifying the communication flow 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 that acquires delivery confirmation information indicating a delivery status of the communication packet; as well as a packet loss determination unit that determines whether 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 sparsely transmits the delivery confirmation packets while receiving the communication packets that are in the same communication flow and have continuous sequence information.

8. A method for determining packet loss, wherein: In a communication device that transmits a communication packet to a destination device using a plurality of paths and receives a delivery confirmation packet for the communication packet from the destination device, the following steps are performed: A sequence information acquisition step, acquiring the sequence information of the communication packets of the communication flow; a sending order corresponding information storing step, storing the corresponding relationship between the sending order of the communication packets for each path and the sequence information of the communication packets acquired by the sequence information acquiring step as sending order corresponding information; A delivery confirmation information acquisition step of acquiring delivery confirmation information indicating a delivery status of the communication packet; as well as The packet loss determination step determines whether or not packet loss has occurred based on the transmission order correspondence information stored in the transmission order correspondence information storage step and the delivery confirmation information acquired in the delivery confirmation information acquisition step.

9. A persistent computer-readable storage medium having computer-implemented commands, the commands comprising a computer-implemented method for controlling the display of an image of a vehicle's surroundings, wherein: The communication device transmits a communication packet to a destination device using a plurality of paths and receives a delivery confirmation packet for the communication packet from the destination device, and the command causes a control unit of the communication device to execute the following steps: A sequence information acquisition step, acquiring sequence information of the communication packets of the communication flow; a sending order corresponding information storing step, storing the corresponding relationship between the sending order of the communication packets for each path and the sequence information of the communication packets acquired by the sequence information acquiring step as sending order corresponding information; A delivery confirmation information acquisition step of acquiring delivery confirmation information indicating a delivery status of the communication packet; as well as The packet loss determination step determines whether or not packet loss has occurred based on the transmission order correspondence information stored in the transmission order correspondence information storage step and the delivery confirmation information acquired in the delivery confirmation information acquisition step.

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