JP7541494B2 - COMMUNICATION TERMINAL DEVICE, COMMUNICATION METHOD, AND COMPUTER PROGRAM - Google Patents

Description

The present invention relates to a communication terminal device, a communication method, and a computer program.

When a communication terminal downloads a computer program or content from a server, if the communication network on which the communication path exists is congested due to a high communication load, there is a problem that the download time may be long or the communication may be interrupted midway and the download may not be completed. One known technology for solving this problem is that described in Patent Document 1. In the technology described in Patent Document 1, a download processing program running on the communication terminal detects the load state related to communication processing, and the download is performed when the communication load is low.

Non-Patent Document 1 also describes ECN (Explicit Congestion Notification) technology in IP (Internet Protocol) networks. In the ECN technology described in Non-Patent Document 1, when congestion occurs in a communication relay device such as a router that constitutes an IP network, the communication relay device explicitly marks congestion information in the header of the packet it forwards and transmits the packet to the destination communication device. Then, when the destination communication device receives the packet, it uses a TCP (Transmission Control Protocol) ACK packet to notify the source communication device of the packet that congestion has occurred in the IP network.

Figure 10 is a schematic diagram of ECN technology using TCP in an IP network. In Figure 10, a sending terminal sets the ECT (ECN-Capable Transport) bit defined in the IP header to 1 and the CE (Congestion Experienced) bit to 0, and sends a packet (TCP-IP packet). If the output queue length at the output destination of the packet it received is equal to or less than a predetermined threshold, the communication relay device (hereinafter sometimes simply referred to as a relay device) forwards the packet as is, but if it exceeds the threshold, it determines that congestion has occurred (communication load is high) and sets the CE bit of the packet to 1 before forwarding the packet. A receiving terminal that receives a packet with the CE bit of the IP header set to 1 returns a "TCP ACK" packet with the ECE (ECN-Echo) flag in the TCP header set to 1 to the sending terminal. When the transmitting terminal receives a "TCP ACK" packet with an ECE flag of 1, it determines that the communication load on the communication path between the transmitting terminal and the receiving terminal is high, and reduces the amount of data sent to the IP network by reducing the congestion window based on TCP congestion control.

JP 2017-27484 A

IETF, RFC3168, “The Addition of Explicit Congestion Notification (ECN) to IP”

However, with the technology described in Patent Document 1 mentioned above, it is not possible to detect the communication load state of the communication network at the time the download starts, so there is a possibility that the download will start even if the communication network is in a high communication load state. If the communication network continues to be in a high communication load state, the proportion of time that the download is paused increases, and the time it takes to complete the download may be longer than expected.

In addition, the technology described in Patent Document 1 uses the download size per unit time (throughput) in the communication terminal device as an index of the communication load, but the communication load of the communication network may be erroneously determined using only the throughput. For example, when TCP communication is performed between a communication terminal device and a server, if the propagation delay is large due to the long distance of the physical communication path between the communication terminal device and the server, even if the communication load of the communication network is small, it may take time to confirm the response of the TCP communication, and the throughput may decrease.

According to the ECN technology using TCP described in Non-Patent Document 1, it is possible to suppress an increase in the communication load of an IP network by having the transmitting terminal reduce the communication volume before the communication load of the IP network becomes high. However, when many transmitting terminals are communicating, there is a possibility that the increase and decrease patterns of the communication volume of the transmitting devices will be synchronized (they will increase or decrease the communication volume all at once), which may cause an imbalance in the communication load of the IP network.

The present invention was made in consideration of these circumstances, and its purpose is to facilitate smooth downloading and uploading of files between a server and a computer via a communications network.

(1) One aspect of the present invention is a communications terminal device comprising: a communication unit that communicates with a server via a communications network; a file transmission/reception unit that executes at least one of file downloads and uploads between the server and the communication network via the communications network; and a control unit that transmits a probe packet to the server at the time the file transmission/reception process is started to check the congestion status of the communications network, and controls the execution of the file transmission/reception process based on the results of the check of the congestion status of the communications network.
(2) One aspect of the present invention is the communication terminal device of (1) above, wherein the control unit randomly determines a transmission interval for the split files when the target file is split into a plurality of split files.
(3) One aspect of the present invention is a communication terminal device of either (1) or (2) above, wherein the control unit obtains the expiration date of the file to be downloaded from the server and controls the download of the file based on the expiration date of the file.
(4) One aspect of the present invention is the communication terminal device of (3) above, wherein the control unit transmits the probe packet to the server and obtains the expiration date of the file to be downloaded.
(5) One aspect of the present invention is the communication terminal device of either (1) or (2) above, wherein the control unit controls the uploading of a file based on an expiration date of the file to be uploaded.
(6) One aspect of the present invention is a communication terminal device of any of (1) to (5) above, wherein the control unit checks the congestion status of the communication network based on IP header information and header information of a protocol higher than IP in a packet received from the server.
(7) One aspect of the present invention is a communication terminal device of any of (1) to (6) above, wherein the control unit, during the period in which the file transmission/reception process is being executed, checks the congestion status of the communication network based on IP header information and header information of a protocol higher than IP in a packet received from the server, and controls the execution of the file transmission/reception process based on the result of checking the congestion status of the communication network.
(8) One aspect of the present invention is a communication terminal device according to any of (1) to (7) above, in which the control unit determines whether to transmit the file in bulk or in parts based on the expiration date of the target file and the congestion status of the communication network.

(9) One aspect of the present invention is a communication method for a communication terminal device having a communication unit that communicates with a server via a communication network, the communication method including a probe packet transmission step in which the communication terminal device transmits a probe packet to the server at the time when at least one of a file transmission/reception process of downloading and uploading a file to be performed between the communication terminal device and the server via the communication network is started, thereby checking the congestion status of the communication network; a file transmission/reception step in which the communication terminal device executes the file transmission/reception process; and a control step in which the communication terminal device controls the execution of the file transmission/reception process based on the result of checking the congestion status of the communication network.

(10) One aspect of the present invention is a computer program for causing a computer of a communication terminal device having a communication unit that communicates with a server via a communication network to execute a probe packet transmission step of transmitting a probe packet to the server at the time when at least one of file transmission and reception processes of downloading and uploading a file to and from the server via the communication network is started to check the congestion status of the communication network, a file transmission and reception step of executing the file transmission and reception process, and a control step of controlling the execution of the file transmission and reception process based on the result of checking the congestion status of the communication network.

The present invention has the effect of enabling smooth downloading and uploading of files between a server and the server via a communication network.

1 is a block diagram showing a configuration example of a communication system according to an embodiment; 1 is a block diagram showing an example of a configuration of a communication terminal device according to an embodiment; 10 is a flowchart illustrating an example of a procedure of a communication method for downloading a file according to an embodiment. FIG. 13 is a diagram illustrating an example of a configuration of a congestion determination table according to an embodiment. 11 is a flowchart illustrating an example of a procedure for a pause determination process according to an embodiment. FIG. 11 is a diagram illustrating an example of the configuration of a retransmission determination table according to an embodiment. FIG. 13 is a diagram illustrating an example of the configuration of a CE distribution determination table according to an embodiment. FIG. 13 is a diagram illustrating an example of a configuration of a throughput determination table according to an embodiment. 11 is a flowchart illustrating an example of a procedure of a communication method for uploading a file according to an embodiment. FIG. 1 is a schematic diagram of ECN technology using TCP in an IP network.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig. 1 is a block diagram showing a configuration example of a communication system according to an embodiment. In Fig. 1, the communication system 1 is configured by connecting a communication terminal device 2 and a server 3 to a communication network NW. The communication network NW may be a wireless network, a wired network, or may be configured of both a wireless network and a wired network. For example, the communication network NW may be configured of the Internet, a mobile phone network, a wireless LAN (Local Area Network), or the like.

The communication terminal device 2 connects to the communication network NW via a wired line or a wireless line. For example, the communication terminal device 2 is a mobile terminal device such as a smartphone or a tablet computer (tablet PC) or an in-vehicle communication terminal device mounted on a vehicle such as an automobile, and connects to the communication network NW via a wireless line such as a mobile phone network or a wireless LAN (Local Area Network).

The communication terminal device 2 has at least one of a download function for downloading files held by the server 3 and an upload function for uploading files held by the communication terminal device 2 to the server 3. In other words, the communication terminal device 2 may have only a download function, only an upload function, or both a download function and an upload function.

The communication terminal device 2 and the server 3 communicate with each other using the IP protocol. IP packets transmitted and received between the communication terminal device 2 and the server 3 are transferred by one or more relay devices (IP routers) 4 (4-1, 4-2, ..., 4-n) provided in the communication network NW. One or more relay devices 4 (4-1, 4-2, ..., 4-n) that are the communication path between the communication terminal device 2 and the server 3 have the ECN function described in FIG. 10. Therefore, if the output queue length at the output destination of the packet that it received is equal to or less than a predetermined threshold, the relay device 4 with the ECN function will forward the packet as is, but if the output queue length exceeds the threshold, it will set the CE bit in the IP header of the packet to 1 before forwarding the packet.

Fig. 2 is a block diagram showing an example of the configuration of a communication terminal device according to this embodiment. In Fig. 2, the communication terminal device 2 includes a communication unit 21, a file transmission/reception unit 22, and a control unit 23.

The communication unit 21 connects to the communication network NW and communicates with the server 3 via the communication network NW.

The file transmission/reception unit 22 executes at least one of file download and upload processing between the server 3 and the file transmission/reception unit 22 via the communication network NW. In other words, the file transmission/reception processing may be processing that realizes only a file download function, may be processing that realizes only a file upload function, or may be processing that realizes both a file download function and a file upload function.

The file transmission/reception unit 22 transmits a file transmission request or a file reception request to the server 3 via the communication unit 21, and then transmits or receives files to or from the server 3. The file transmission/reception unit 22 is controlled by the control unit 23 to execute the file transmission/reception process. For example, the file transmission/reception unit 22 is controlled by the control unit 23 to pause or continue file transmission/reception.

The control unit 23 controls the execution of the file transmission/reception process for the file transmission/reception unit 22. The control unit 23 transmits a probe packet at the time the file transmission/reception process is started to check the congestion status of the communication network NW, and controls the execution of the file transmission/reception process based on the result of checking the congestion status of the communication network NW. The probe packet is a packet for checking the congestion status of the communication network NW using the ECN technology described in FIG. 10.

The functions of the communication terminal device 2 are realized by the communication terminal device 2 having computer hardware such as a CPU (Central Processing Unit) and memory, and the CPU executing a computer program stored in the memory. For example, the communication terminal device 2 may be a mobile terminal device such as a smartphone or a tablet computer (tablet PC), or an in-vehicle communication terminal device mounted on a vehicle such as an automobile. For example, the communication terminal device 2 may be a stationary terminal device such as a personal computer.

[File Download]
Next, a communication method in which the communication terminal device 2 downloads a file from the server 3 will be described with reference to Fig. 3. Fig. 3 is a flow chart showing an example of the procedure of the communication method in downloading a file according to this embodiment.

When a file download request is received, the communication terminal device 2 starts the process shown in Figure 3.

(Step S11) The control unit 23 transmits a probe packet to the server 3. The control unit 23 includes in the message portion of the probe packet the file name of the file that the communication terminal device 2 wishes to download (file to be downloaded) and a message requesting the server 3 to transmit a packet in which the ECT bit in the IP header is set to 1 and the CE bit is set to 0.

The server 3 that receives the probe packet sends a packet addressed to the communication terminal device 2 that sent the probe packet, with the ECT bit in the IP header set to 1 and the CE bit set to 0, including the size and expiration date of the file to be downloaded. The control unit 23 of the communication terminal device 2 acquires the size and expiration date of the file to be downloaded from the packet received from the server 3. Examples of files that have an expiration date include files that are updated periodically and files for software updates. The communication terminal device 2 may send the probe packet to the server 3 multiple times.

(Step S12) The control unit 23 checks the CE bit in the IP header of the packet received from the server 3. If this check shows that a packet with a CE bit of 1 has been received, the process proceeds to step S13. On the other hand, if a packet with a CE bit of 1 has not been received, the process proceeds to step S15. If the communication terminal device 2 receives a packet with a CE bit of 1 from the server 3, the communication load on the download communication path from the server 3 to the communication terminal device 2 is high.

(Step S13) The control unit 23 calculates the planned download pause time and the congestion judgment level. A minimum value and a maximum value of the planned download pause time are set in advance in the communication terminal device 2. The control unit 23 randomly determines the planned download pause time for this time within the range from the minimum value to the maximum value of the planned download pause time.

The control unit 23 has a congestion judgment table as shown in FIG. 4. In FIG. 4, the congestion judgment table shows the correspondence between the remaining data amount per time (bytes/time) and the congestion judgment level. The numerical value of the remaining data amount per time in FIG. 4 is an example. Congestion judgment level "1" indicates that the remaining data amount of the file to be downloaded is large compared to the remaining time until the expiration date of the file to be downloaded. Congestion judgment level "2" indicates that the remaining data amount of the file to be downloaded is medium compared to the remaining time until the expiration date of the file to be downloaded. Congestion judgment level "3" indicates that the remaining data amount of the file to be downloaded is small compared to the remaining time until the expiration date of the file to be downloaded.

The control unit 23 calculates the remaining amount of data per hour by dividing the remaining amount of data (bytes) of the file to be downloaded by the remaining time from the time obtained by adding the current download scheduled pause time to the current time (the time when the download starts or resumes) until the expiration date of the file to be downloaded. The control unit 23 obtains the congestion judgment level corresponding to the remaining amount of data per hour resulting from this calculation from the congestion judgment table.

(Step S14) If the congestion determination level calculated in step S13 is 1, proceed to step S15; otherwise, proceed to step S19.

(Step S15) The control unit 23 instructs the file transmission/reception unit 22 to download the file to be downloaded. In response to the download instruction from the control unit 23, the file transmission/reception unit 22 transmits a download request for the file to be downloaded to the server 3, and starts or resumes downloading the file to be downloaded.

Here, as an example of a download method, the file transmission/reception unit 22 performs a split download. In a split download, a file to be downloaded is split into a plurality of split files and transmitted from the server 3 to the communication terminal device 2. A split download is realized, for example, by using the "Range Request" function of HTTP (Hyper Text Transfer Protocol). According to the "Range Request" function of HTTP, it is possible to download only a part of a specified file (between XX bytes and YY bytes) by specifying the start byte (XX) and end byte (YY) of the specified file. The size of the split download (split file) is specified arbitrarily. As a method of determining the split download size, for example, an initial value of the split download size is set in advance, and if the download continues without pause, the split download size is increased by a predetermined amount for each step of the split download.

(Step S16) When the divided download of the file to be downloaded is completed and all data of the file to be downloaded has been acquired, the process of FIG. 3 ends. On the other hand, if all data of the file to be downloaded has not yet been acquired, the process proceeds to step S17.

(Step S17) The control unit 23 executes a pause determination process.

Here, the pause determination process (step S17 in FIG. 3) will be described with reference to FIG. 5. FIG. 5 is a flowchart showing an example of the procedure for the pause determination process according to this embodiment.

(Step S21) The control unit 23 calculates the planned download pause time in the same manner as in step S13.

(Step S22) The control unit 23 uses the planned download pause time calculated in step S21 to calculate the congestion determination level in the same manner as in step S13.

(Step S23) If the congestion determination level calculated in step S22 is 1, the pause determination process in FIG. 5 is terminated. In this case, the pause determination result is "no pause." On the other hand, if the congestion determination level calculated in step S22 is not 1, the process proceeds to step S24.

(Step S24) The control unit 23 acquires pause determination data. The pause determination data is data including the following information (1), (2), and (3).
(1) Whether or not a packet retransmission occurred during divided download.
(2) Distribution of received IP packets with the CE bit set to 1 during divided download.
(3) Reception throughput during divided download.

(Step S25) The control unit 23 determines whether or not the pause determination condition is satisfied based on the pause determination data acquired in step S24 and the congestion determination level ("2" or "3") calculated in step S22. The method for determining the pause determination condition is described below.

The control unit 23 holds a retransmission judgment table (Figure 6), a CE distribution judgment table (Figure 7), and a throughput judgment table (Figure 8).

(First Pause Judgment Condition: Pause Judgment Condition Related to Retransmission)
The control unit 23 recognizes whether or not retransmission of IP packets has occurred during divided downloading based on the pause determination data. If no retransmission of IP packets has occurred during divided downloading, the control unit 23 determines "no pause: 0" from the retransmission determination table (FIG. 6). On the other hand, if retransmission of IP packets has occurred during divided downloading, the control unit 23 determines "pause: 1" from the retransmission determination table (FIG. 6).

(Second Pause Determination Condition: Pause Determination Condition Related to CE Bit)
The control unit 23 recognizes the reception distribution of IP packets whose CE bit is 1 during divided download using the pause determination data. The control unit 23 determines whether to enter "no pause: 0" or "pause: 1" from the CE distribution determination table ( FIG. 7 ) based on the recognition result of the reception distribution and the congestion determination level ("2" or "3").

In the CE distribution determination table in FIG. 7, there are three types of patterns (first pattern, second pattern, and third pattern) as examples of the reception distribution pattern of IP packets with a CE bit of 1. An IP packet with a CE bit of 1 is called an IP packet (CE=1). The first pattern is pattern No. 1 in FIG. 7, in which no IP packet (CE=1) is received. The second pattern is pattern No. 2 and No. 3 in FIG. 7, in which IP packets (CE=1) are received in the first 3/4 of the divided download period, but no IP packets (CE=1) are received in the last 1/4 of the period. The third pattern is pattern No. 4 in FIG. 7, in which IP packets (CE=1) are not received or are received in the first 3/4 of the divided download period, but IP packets (CE=1) are received in the last 1/4 of the period.

When the reception distribution of the IP packet (CE=1) recognized by the pause judgment data is the first pattern, the control unit 23 judges "no pause: 0" from the CE distribution judgment table (No. 1 in FIG. 7). When the reception distribution of the IP packet (CE=1) recognized by the pause judgment data is the second pattern, the control unit 23 judges "no pause: 0" from the CE distribution judgment table (No. 2 in FIG. 7) when the congestion judgment level is "2", and judges "pause: 1" from the CE distribution judgment table (No. 3 in FIG. 7) when the congestion judgment level is "3". When the reception distribution of the IP packet (CE=1) recognized by the pause judgment data is the third pattern, the control unit 23 judges "pause: 1" from the CE distribution judgment table (No. 4 in FIG. 7).

(Third Pause Judgment Condition: Pause Judgment Condition Related to Reception Throughput)
The control unit 23 recognizes the reception throughput during divided downloading from the pause judgment data. Based on the recognition result of the reception throughput and the congestion judgment level ("2" or "3"), the control unit 23 judges whether to set "no pause: 0" or "pause: 1" from the throughput judgment table (FIG. 8).

In the throughput determination table in FIG. 8, there are three ranges (first range, second range, and third range) as examples of the range of reception throughput. The first range is range No. 1 in FIG. 8, which is less than 128 kilobits per second. The second range is range No. 2 and No. 3 in FIG. 8, which is 128 kilobits per second or more and less than 1 megabit per second. The third range is range No. 4 in FIG. 8, which is 1 megabit per second or more. The throughput values in FIG. 8 are examples.

When the reception throughput recognized by the pause judgment data is within the first range, the control unit 23 judges "pause: 1" from the throughput judgment table (No. 1 in FIG. 8). When the reception throughput recognized by the pause judgment data is within the second range, the control unit 23 judges "no pause: 0" from the throughput judgment table (No. 2 in FIG. 8) if the congestion judgment level is "2", and judges "pause: 1" from the throughput judgment table (No. 3 in FIG. 8) if the congestion judgment level is "3". When the reception throughput recognized by the pause judgment data is within the third range, the control unit 23 judges "no pause: 0" from the throughput judgment table (No. 4 in FIG. 8).

The control unit 23 determines that the pause determination condition is satisfied when any one of the first pause determination condition, the second pause determination condition, and the third pause determination condition is determined to be "pause: 1." In this case, the process proceeds to step S26.

On the other hand, if the control unit 23 judges that the first pause judgment condition, the second pause judgment condition, and the third pause judgment condition are all "no pause: 0", it determines that the pause judgment conditions are not satisfied. After this, it ends the pause judgment process of FIG. 5.

(Step S26) When the control unit 23 judges that "pause is present: 1" in any one of the above-mentioned first pause judgment condition, the second pause judgment condition, and the third pause judgment condition (Step S25, YES), the pause judgment result is "pause is present." On the other hand, when the control unit 23 judges that "pause is not present: 0" in all of the above-mentioned first pause judgment condition, the second pause judgment condition, and the third pause judgment condition (Step S25, NO), the pause judgment result is "no pause."

This concludes the explanation of the pause determination process (step S17 in Figure 3). Let's return to the explanation in Figure 3.

(Step S18) If the result of the pause determination in step S17 is "pause present," proceed to step S19. On the other hand, if the result of the pause determination in step S17 is "pause not present," return to step S15 and continue the divided download.

(Step S19) The control unit 23 causes the file transmission/reception unit 22 to pause downloading of the files to be downloaded for the most recently calculated download schedule pause time. Specifically, if the process proceeds to step S19 due to "NO" in step S14, the control unit 23 causes the file transmission/reception unit 22 to pause downloading of the files to be downloaded for the most recently calculated download schedule pause time. If the process proceeds to step S19 due to "YES" in step S18, the control unit 23 causes the file transmission/reception unit 22 to pause downloading of the files to be downloaded for the most recently calculated download schedule pause time in the pause determination process (step S21) in step S17. After the downloading of the files to be downloaded has been paused for the most recently calculated download schedule pause time, the process returns to step S11.

The above explains the communication method when the communication terminal device 2 downloads a file from the server 3.

[File Upload]
Next, a communication method when the communication terminal device 2 uploads a file to the server 3 will be described with reference to Fig. 9. Fig. 9 is a flowchart showing an example of the procedure of the communication method for uploading a file according to this embodiment.

When a file upload request is received, the communication terminal device 2 starts the process shown in FIG. 9.

(Step S31) The control unit 23 transmits a probe packet to the server 3. The control unit 23 sets the ECT bit in the IP header of the probe packet to 1 and the CE bit to 0. The control unit 23 also includes in the message portion of the probe packet a message requesting the server 3 to return a packet equivalent to "ECN-Echo."

The server 3 that receives the probe packet replies with a packet equivalent to "ECN-Echo" addressed to the communication terminal device 2 that sent the probe packet, according to the CE bit of the probe packet. For example, when the server 3 receives a probe packet with the CE bit in the IP header set to 1, it replies to the communication terminal device 2 with a "TCP ACK" packet in which the ECE (ECN-Echo) flag in the TCP header is set to 1. Note that the communication terminal device 2 may transmit the probe packet to the server 3 multiple times.

(Step S32) The control unit 23 recognizes whether the server 3 has received a probe packet with a CE bit of 1 from a packet equivalent to "ECN-Echo" received from the server 3. For example, when a "TCP ACK" packet with an ECE flag of 1 (corresponding to a notification packet with CE=1) is received from the server 3, the control unit 23 recognizes that the server 3 has received a probe packet with a CE bit of 1. In this case, the control unit 23 proceeds to step S33. On the other hand, when a "TCP ACK" packet with an ECE flag of 1 (corresponding to a notification packet with CE=1) is not received from the server 3, the control unit 23 recognizes that the server 3 has not received a probe packet with a CE bit of 1. In this case, the control unit 23 proceeds to step S35. When the server 3 has received a probe packet with a CE bit of 1, the communication load on the upload communication path from the communication terminal device 2 to the server 3 is high.

(Step S33) The control unit 23 calculates the planned upload pause time and the congestion judgment level. A minimum value and a maximum value of the planned upload pause time are set in advance in the communication terminal device 2. The control unit 23 randomly determines the current planned upload pause time from within the range from the minimum value to the maximum value of the planned upload pause time.

The method for calculating the congestion judgment level is the same as the calculation method for the file download in step S13 of FIG. 3 described above. However, "download" is replaced with "upload." In addition, the expiration date of the file to be uploaded, which is used to calculate the congestion judgment level, is determined by the communication terminal device 2.

(Step S34) If the congestion determination level calculated in step S33 is 1, proceed to step S35; otherwise, proceed to step S39.

(Step S35) The control unit 23 instructs the file transmission/reception unit 22 to upload the file to be uploaded. In response to the upload instruction from the control unit 23, the file transmission/reception unit 22 transmits an upload request for the file to be uploaded to the server 3, and starts or resumes uploading the file to be uploaded.

Here, as an example of an upload method, the file transmission/reception unit 22 performs a split upload. In the split upload, a file to be uploaded is split into a plurality of split files and transmitted from the communication terminal device 2 to the server 3. The split upload is realized, for example, by using the HTTP "Range Request" function. According to the HTTP "Range Request" function, it is possible to upload only a part of a specified file (between XX bytes and YY bytes) by specifying the start byte (XX) and end byte (YY) of the specified file. The size of the split upload (split file) is specified arbitrarily. As a method of determining the split upload size, for example, an initial value of the split upload size is set in advance, and if the upload continues without pause, the split upload size is increased by a predetermined amount for each split upload step.

(Step S36) When the divided upload of the file to be uploaded is completed and all data of the file to be uploaded has been transmitted, the process of FIG. 9 ends. On the other hand, if all data of the file to be uploaded has not yet been transmitted, proceed to step S37.

(Step S37) The control unit 23 executes a pause determination process. The pause determination process is the same as the pause determination process for file download in FIG. 5 described above. However, "download" is replaced with "upload." Below, only the differences from the description of steps S21 to S26 in FIG. 5 described above will be described.

In step S22, the expiration date of the file to be uploaded, which is used to calculate the congestion determination level, is determined by the communication terminal device 2.

The pause determination data acquired in step S24 includes the following information (1), (2), and (3).
(1) Whether or not a packet retransmission occurred during a divided upload.
(2) Distribution of received notification packets with CE=1 during divided upload.
(3) Transmission throughput during divided upload.

In step S25, in determining whether the "second pause determination condition: pause determination condition related to the CE bit" is satisfied, the "reception distribution of IP packets with a CE bit of 1" is read as the "reception distribution of notification packets with CE=1." In addition, in determining whether the (third pause determination condition: pause determination condition related to the reception throughput) is satisfied, the "reception throughput" is read as the "transmission throughput."

Returning to FIG.
(Step S38) If the pause determination result in step S37 is "pause present", proceed to step S39. On the other hand, if the pause determination result in step S37 is "no pause", return to step S35 and continue the divided upload.

(Step S39) The control unit 23 causes the file transmission/reception unit 22 to suspend uploading of files to be uploaded for the most recently calculated planned upload pause time. Specifically, if the process proceeds to step S39 due to "NO" in step S34, the control unit 23 causes the file transmission/reception unit 22 to suspend uploading of files to be uploaded for the most recently calculated planned upload pause time. If the process proceeds to step S39 due to "YES" in step S38, the control unit 23 causes the file transmission/reception unit 22 to suspend uploading of files to be uploaded for the most recently calculated planned upload pause time in the pause determination process (step S21) in step S37. After uploading of files to be uploaded has been suspended for the planned upload pause time, the process returns to step S31.

The above explains the communication method when the communication terminal device 2 uploads a file to the server 3.

According to this embodiment, the communication terminal device 2 transmits a probe packet to the server 3 at the time when a file download or upload is started to check the congestion status of the communication network NW, and controls the execution of the file download or upload based on the result of checking the congestion status of the communication network NW, thereby making it possible to smoothly perform file downloads and uploads between the communication terminal device 2 and the server 3 via the communication network NW.

According to this embodiment, by taking into consideration the expiration date of the file to be downloaded or uploaded, and information on the congestion status of the communication network NW provided by the relay device 4 of the communication network NW during the period of sending and receiving the file, it is possible to send and receive the file within the expiration date of the file while avoiding a situation in which the communication network NW is congested.

According to this embodiment, in divided downloads and divided uploads, the transmission intervals between divided files (scheduled download pause times and planned upload pause times) are randomly determined, making it possible to avoid situations in which multiple communication terminal devices simultaneously start or pause sending and receiving files.

A variation of the above embodiment is described below.

(Variation 1)
In the above embodiment, split downloads and split uploads (split file transmissions) are always performed, but in the first modification, bulk downloads and bulk uploads (bulk file transmissions) are performed in the case of an emergency. Specifically, in step S14 of FIG. 3, if the congestion determination level calculated in step S13 is 1, the control unit 23 instructs the file transmission/reception unit 22 to perform a bulk download of the files to be downloaded. As a result, the file transmission/reception unit 22 performs a bulk download of the files to be downloaded. Also, in step S34 of FIG. 9, if the congestion determination level calculated in step S33 is 1, the control unit 23 instructs the file transmission/reception unit 22 to perform a bulk upload of the files to be uploaded. As a result, the file transmission/reception unit 22 performs a bulk upload of the files to be uploaded.
3, if a packet with CE=0 is received, a congestion determination level may be calculated, and if the congestion determination level is 1, a bulk download may be performed. Similarly, if a notification packet with CE=0 is received, a congestion determination level may be calculated, and if the congestion determination level is 1, a bulk upload may be performed.

(Variation 2)
In the above embodiment, the ECN technique using TCP shown in Fig. 10 is applied, but is not limited to this. As a communication protocol higher than IP, an ECN technique based on, for example, QUIC other than TCP may be applied. The QUIC-based ECN technique is described in "13.4. Explicit Congestion Notification" of "IETF, RFC9000, "QUIC: A UDP-Based Multiplexed and Secure Transport".

Furthermore, this will enable improvements in the overall service quality of mobile communication services, such as for connected cars, and will contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation."

The above describes an embodiment of the present invention in detail with reference to the drawings, but the specific configuration is not limited to this embodiment and includes design modifications within the scope of the present invention.

In addition, a computer program for implementing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the term "computer system" may include hardware such as an OS and peripheral devices.
In addition, the term "computer-readable recording medium" refers to a storage device such as a flexible disk, a magneto-optical disk, a ROM, a writable non-volatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disc), or a hard disk built into a computer system.

Furthermore, the term "computer-readable recording medium" includes devices that retain a program for a certain period of time, such as volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that serves as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line.
The program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by a transmission wave in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be a program for implementing some of the above-mentioned functions, or may be a so-called differential file (differential program) that can implement the above-mentioned functions in combination with a program already recorded in the computer system.

1...communication system, 2...communication terminal device, 3...server, 4...relay device, 21...communication unit, 22...file transmission/reception unit, 23...control unit, NW...communication network

Claims (10)

A communication unit that communicates with a server via a communication network;
a file transmission/reception unit that executes at least one of file downloading and uploading between the server and the file transmission/reception unit via the communication network;
a control unit that transmits a probe packet to the server at the time when the file transmission/reception process is started to check the congestion state of the communication network, and controls the execution of the file transmission/reception process based on a result of the check of the congestion state of the communication network;
Equipped with
The control unit randomly determines a transmission interval for the divided files when the target file is divided into a plurality of divided files.
Communications terminal equipment. A communication unit that communicates with a server via a communication network;
a file transmission/reception unit that executes at least one of file downloading and uploading between the server and the file transmission/reception unit via the communication network;
a control unit that transmits a probe packet to the server at the time when the file transmission/reception process is started to check the congestion state of the communication network, and controls the execution of the file transmission/reception process based on a result of the check of the congestion state of the communication network;
Equipped with
the control unit controls execution of a file transmission/reception process for a file to be downloaded or uploaded based on an expiration date of the file.
Communications terminal equipment. the control unit transmits the probe packet to the server and acquires the expiration date of the file to be downloaded.
The communication terminal device according to claim 2 . the control unit determines whether to transmit the file in a batch or in parts based on the expiration date of the file and the remaining data amount of the file;
The communication terminal device according to claim 2 . A communication unit that communicates with a server via a communication network;
a file transmission/reception unit that executes at least one of file downloading and uploading between the server and the file transmission/reception unit via the communication network;
a control unit that transmits a probe packet to the server at the time when the file transmission/reception process is started to check the congestion state of the communication network, and controls the execution of the file transmission/reception process based on a result of the check of the congestion state of the communication network;
Equipped with
the control unit confirms a congestion state of the communication network based on IP header information and header information of a protocol higher than IP in a packet received from the server;
Communications terminal equipment. the control unit, during a period in which the file transmission/reception process is being executed, checks a congestion status of the communication network based on IP header information and header information of a protocol higher than IP in a packet received from the server, and controls execution of the file transmission/reception process based on a result of checking the congestion status of the communication network.
6. The communication terminal device according to claim 5 . A communication method for a communication terminal device having a communication unit that communicates with a server via a communication network, comprising:
a probe packet transmission step in which the communication terminal device transmits a probe packet to the server at a time when at least one of a file transmission/reception process of downloading and uploading a file to be performed between the communication terminal device and the server via the communication network is started, thereby checking a congestion state of the communication network;
a file transmission/reception step in which the communication terminal device executes the file transmission/reception process;
a control step of the communication terminal device controlling execution of the file transmission/reception process based on a result of checking a congestion state of the communication network;
Including,
In the control step, when the target file is divided into a plurality of divided files, a transmission interval of the divided files is randomly determined.
Communication methods. A communication method for a communication terminal device having a communication unit that communicates with a server via a communication network, comprising:
a probe packet transmission step in which the communication terminal device transmits a probe packet to the server at a time when at least one of a file transmission/reception process of downloading and uploading a file to be performed between the communication terminal device and the server via the communication network is started, thereby checking a congestion state of the communication network;
a file transmission/reception step in which the communication terminal device executes the file transmission/reception process;
a control step of the communication terminal device controlling execution of the file transmission/reception process based on a result of checking a congestion state of the communication network;
Including,
The control step controls execution of a file transmission/reception process of a file to be downloaded or uploaded based on an expiration date of the file.
Communication methods. A communication method for a communication terminal device having a communication unit that communicates with a server via a communication network, comprising:
a probe packet transmission step in which the communication terminal device transmits a probe packet to the server at a time when at least one of a file transmission/reception process of downloading and uploading a file to be performed between the communication terminal device and the server via the communication network is started, thereby checking a congestion state of the communication network;
a file transmission/reception step in which the communication terminal device executes the file transmission/reception process;
a control step of the communication terminal device controlling execution of the file transmission/reception process based on a result of checking a congestion state of the communication network;
Including,
the communication terminal device checks a congestion state of the communication network based on IP header information and header information of a protocol higher than IP in a packet received from the server;
Communication methods. A computer program product for causing a computer to execute the communication method according to any one of claims 7 to 9 .

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