JP7286513B2 - COMMUNICATION DEVICE, COMMUNICATION DEVICE CONTROL METHOD, AND PROGRAM - Google Patents

Description

The present invention relates to a communication device and the like that perform communication using an acknowledgment.

TCP (Transport Control Protocol) defines a mechanism in which a receiving device that receives a data packet from a transmitting device transmits an acknowledgment (ACK) packet (Patent Document 1). Further, TCP defines a delayed acknowledgment (delayed ACK) in which, when a predetermined number of data packets are received, one ACK packet is transmitted for the predetermined number of data packets. TCP also stipulates that even if the number of received data packets is less than a predetermined number, a delayed ACK packet is transmitted when a predetermined delay time elapses from the reception of the first data packet. ing.

JP 2014-183533 A

As described above, in TCP communication using delayed ACK, the transmission frequency of delayed ACK packets (hereinafter referred to as ACK transmission frequency) and the delay time from the reception of the first data packet for transmitting delayed ACK (hereinafter referred to as , simply called delay time) must be set. The ACK transmission frequency corresponds to the number of received data packets used as a reference for transmitting delayed ACK packets (hereinafter the reference number of packets for delayed ACK transmission). Here, when the ACK transmission frequency is set to be fixed (that is, when the reference number of packets for delayed ACK transmission is set to be fixed), the following problem arises.

The window size indicating the free space of the receiving buffer of the receiving device is notified to the transmitting device using the window size field of the ACK packet. The transmitting device determines the amount of data to be transmitted based on the window size obtained from the received ACK packet. When the transmitting device finishes transmitting data packets of a determined amount of data (for example, data for the window size), it stops transmitting data packets until it receives an ACK packet from the receiving device. If the number of data packets sent before the transmitting device stops transmitting data packets is less than the reference number of packets for delayed ACK transmission, the receiving device transmits delayed ACK packets after the delay time has elapsed. However, communication performance deteriorates as the number of times the receiving device transmits the delayed ACK packet after the delay time has elapsed increases. As the reference number of packets for delayed ACK transmission is set larger (that is, the lower the frequency of ACK transmission), the number of packets that must wait for ACK transmission increases. sexuality increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique for controlling the transmission frequency of delayed ACK packets.

As one means for achieving the above object, the communication device of the present invention has the following configuration. That is, the communication device comprises receiving means for receiving a packet from the communication device, storage means for storing data of the packet received by the receiving means in a receiving buffer, and confirmation of the packet received by the receiving means. a control means for controlling a reference number of packets used as a reference for transmitting a response (ACK) packet; and transmitting means for transmitting the reference packet so that the transmission frequency of the ACK packet is increased when the window size representing the free space of the reception buffer is less than a predetermined threshold. control the numbers.

In accordance with the present invention, techniques are provided for controlling the frequency of transmission of delayed ACK packets.

FIG. 2 is a diagram showing a connection form between a communication device and another communication device 20; FIG. 2 is a block diagram showing a hardware configuration example of the communication device 10; FIG. 2 is a block diagram showing a functional configuration example of the communication device 10; 4 is a flowchart of processing executed by the communication device 10 according to the first embodiment; 6 is a flowchart of processing executed by the communication device 10 according to the second embodiment; 9 is a flowchart of processing executed by the communication device 10 according to the third embodiment;

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In addition, the following embodiments do not limit the invention according to the scope of claims. Although multiple features are described in the embodiments, not all of these multiple features are essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
[Configuration of communication system]
FIG. 1 is a diagram showing a connection configuration in a communication system composed of a communication device 10 and another communication device 20. As shown in FIG. The communication device 10 and another communication device 20 are interconnected via a network 30 . For example, the other communication device 20 transmits a data packet, and the communication device 10 receiving the data packet transmits a (delayed) ACK packet. Examples of the communication device 10 include sensor devices, tablets, smartphones, PCs, notebook PCs, mobile phones, cameras, video cameras, head-mounted displays, etc., as long as they satisfy the hardware configuration and functional configuration described later. , but not limited to. On the other hand, the other communication device 20 is, for example, a sensor device, tablet, smart phone, PC, notebook PC, mobile phone, camera, video camera, head-mounted display, etc., but is not limited to these.

The network 30 is, for example, a wireless LAN (Local Area Network) in which the communication device 10 and another communication device 20 participate, and is a wireless network compatible with the IEEE802.11 series standards, for example. Note that the network 30 is not limited to a wireless LAN, and uses TCP/IP (Transmission Control Protocol/Internet Protocol) communication or ACK (acknowledgement) packet communication, such as a wired LAN such as Ethernet, or a combination of a wireless LAN and a wired LAN. Any network that allows other protocols to be used is acceptable.

[Equipment configuration]
FIG. 2 is a block diagram showing a hardware configuration example of the communication device 10 according to this embodiment. The communication device 10 includes a RAM (Random Access Memory) 201, a ROM (Read Only Memory) 202, a CPU (Central Processing Unit) 203, a timer section 204, a media access control module (MAC) 205, a physical layer module (PHY) 206, An antenna 207 is provided. Note that it is not essential that the communication device 10 include all of the above modules.

A RAM 201 temporarily stores programs and data. ROM 202 stores programs and parameters that do not require modification. The CPU 203 controls the communication device 10 as a whole. The CPU 203 uses the RAM 201 as a main memory as a work memory and executes various programs stored in a storage medium of a program storage unit such as a ROM 202 and an unillustrated HDD (Hard Disc Drive). A timer unit 204 performs timekeeping processing and manages the elapse of time such as program processing. MAC 205 and PHY 206 are communication units that perform communication via network 30 via antenna 207 . The CPU 203 executes a network driver and controls the MAC 205 to transmit and receive various data.

FIG. 3 is a block diagram showing a functional configuration example of the communication device 10 according to this embodiment. The communication device 10 includes a control unit 301, a LAN control unit 302, and a TCP/IP control unit 303. The TCP/IP control unit 303 includes a reception processing unit 304, a transmission processing unit 305, a buffer management unit 306, and a packet counting unit 307. , and an ACK control unit 308 . Each functional module is processed by the CPU 203 . Note that it is not essential that the communication device 10 include all of the above functional modules.

The control unit 301 controls individual functional modules included in the communication device 10 . The LAN control unit 302 controls the MAC 205 and controls communication with other communication devices 20 . When the communication device 10 establishes a wireless LAN connection with another communication device 20 via an external wireless access point (not shown), the LAN control unit 302 controls the MAC 205 to establish wireless LAN communication with the wireless access point. control. Note that the LAN control unit 302 is not limited to this, and can control other communication methods such as control of wired LAN communication, TCP/IP communication, and communication using ACK (acknowledgement) packets.

The TCP/IP control unit 303 uses the LAN control unit 302 to perform TCP/IP communication protocol processing and communication control with the other communication device 20 . Note that the TCP/IP control unit 303 is not limited to TCP/IP, and may use other protocols that use ACK (acknowledgement) packet communication. Functional modules in the TCP/IP control unit 303 will be described below.

The reception processing unit 304 performs processing for receiving packets/information such as data packets from other communication devices 20 via the LAN control unit 302 . Packet data can have a size larger than MSS (Maximum Segment Size) in TCP. The transmission processing unit 305 performs processing for transmitting ACK packets and/or delayed ACK packets via the LAN control unit 302 . For example, the transmission processing unit 305 uses the timer unit 204 to combine ACK packets for data packets received before a predetermined delay time elapses from the reception of the first data packet by the reception processing unit 304. In summary, it is transmitted as a delayed ACK packet. However, even before the delay time has passed, the reception processing unit 304 has received the reference number of packets for delayed ACK transmission (the number of reception data packets required to transmit the delayed ACK packet). In this case, the transmission processing unit 305 transmits a delayed ACK packet. Note that the initial value of the delay time and the initial value of the reference number of packets for delayed ACK transmission may be set in advance in the communication device 10, or may be set in the ACK control unit 308 to be described later via the user's operation or the like. may be set by

A buffer management unit 306 manages a buffer provided in the RAM 201 or the like, and performs control for storing or deleting various data in the buffer. In the present embodiment, the buffer management unit 306 manages a buffer, hereinafter referred to as a reception buffer, and controls storage of a window size representing the free space of the reception buffer. The stored window size may be the window size notified to the other communication device 20 or the window size not notified to the other communication device 20 . In this embodiment, an example of using the RAM 201 as a storage medium to be controlled by the buffer management unit 306 is shown, but the present invention is not limited to this, and other storage units such as an auxiliary storage device (not shown) may be used. A packet count unit 307 counts the data packets received by the reception processing unit 304 . ACK control section 308 controls transmission of delayed ACK packets. For example, the ACK control unit 308 controls the communication frequency of delayed ACK packets, that is, the number of reference packets for delayed ACK transmission.

[Flow of processing in the first embodiment]
FIG. 4 is a flowchart of processing executed by the communication device 10 according to this embodiment. Specifically, FIG. 4 is a flowchart showing a procedure for transmitting delayed ACK packets by changing the ACK transmission frequency according to conditions after the communication apparatus 10 receives data packets. The flowchart shown in FIG. 4 can be realized by the CPU 203 of the communication device 10 executing a control program stored in the ROM 202 to perform calculation and processing of information and control of each hardware.

In S<b>401 , the reception processing unit 304 receives a data packet from another communication device 20 via the LAN control unit 302 .

Processing after S402 is processing in the TCP/IP control unit 303 . In S402, the buffer management unit 306 stores the data packet received by the reception processing unit 304 in the reception buffer. A data packet received from another communication device 20 may be temporarily stored in a buffer managed by the LAN control unit 302 . Stores the data packet stored in the receive buffer. Also, the buffer management unit 306 updates the free space (window size) of the reception buffer after storing the data packet in the reception buffer. In S402, the transmission processing unit 305 measures the time clocked by the timer unit 204. FIG. In S<b>402 , if the timer unit 204 has not started timekeeping (not activated), the transmission processing unit 305 causes the timer unit 204 to start timekeeping. That is, timer section 204 counts the time from the reception of the first data packet for which no ACK packet has been transmitted.

In S403, the ACK control unit 308 compares the window size managed by the buffer management unit 306 with a predetermined threshold. If the window size is smaller than the predetermined threshold (YES in S403), the process proceeds to S404, and if the window size is equal to or greater than the predetermined threshold (NO in S403), the process proceeds to S405. The predetermined threshold is set in advance in the communication device 10, for example, and may be set to a minimum value obtained by multiplying the reference number of packets for delayed ACK transmission by the MSS, and may be set to a value greater than or equal to the minimum value.

In S404, ACK control section 308 sets the ACK transmission frequency to be high. That is, ACK control section 308 changes the reference number of packets for delayed ACK transmission to a value smaller than the current value. The post-change value may be, for example, an integer value less than the currently set value and with 1 as the minimum value.

In S405, the packet counting unit 307 compares the number of data packets received by the reception processing unit 304 (the number of received data packets) with the reference number of packets for delayed ACK transmission. If the number of received data packets is greater than or equal to the reference number of packets for delayed ACK transmission (YES in S405), the process proceeds to S406, and if the number of received data packets is less than the reference number of packets for delayed ACK transmission (S405 NO), and the process proceeds to S409.

In S406, the buffer management unit 306 updates the window size to increase the window size in response to the fact that the packet data stored in the reception buffer is reduced (deleted), and the packet count unit 307 Initialize (set to 0) the number of received data packets that has been counted. Note that the packet data stored in the reception buffer can be reduced by extraction by a user application or the like (processing in an upper layer). The reception processing unit 304 also initializes the timer unit 204 (sets it to 0). In S<b>407 , the transmission processing unit 305 transmits the delayed ACK packet via the LAN control unit 302 . The delayed ACK packet can include window size information in the reception buffer managed by the buffer management unit 306 . That is, an updated (widened) window size can be notified.

In S408, the ACK control unit 308 restores the ACK transmission frequency. That is, ACK control section 308 changes the reference number of packets for delayed ACK transmission to the initial value (value before change in S404).

In S409, which proceeds when the number of received data packets is less than the reference number of packets for delayed ACK transmission, ACK control section 308 delays the time measured by timer section 204 (elapsed time of timer section 204) by a predetermined delay. Compare with time. If the elapsed time of timer section 204 is less than the delay time (YES at S409), the process proceeds to S410, and if the elapsed time of timer section 204 is greater than or equal to the delay time (NO at S409), the process proceeds to S406. In S410, the packet counting unit 307 increments the count number of data packets received by the reception processing unit 304 by 1, and the process proceeds to S408.

As described above, the communication device 10 changes the ACK transmission frequency according to the window size in the current receive buffer managed. That is, when the window size is less than the predetermined threshold, communication device 10 sets the reference number of packets for delayed ACK transmission to a smaller value in order to increase the frequency of ACK transmission. As a result, it is possible to reduce the number of delayed ACKs that would have been transmitted after the delay time had elapsed with the ACK transmission frequency before the change, and prevent deterioration in communication performance.

(Second embodiment)
Communication processing according to the second embodiment will be described below. In this embodiment, the communication device 10 sets a simulated window size when it is assumed that the other communication device 20 could not normally receive a (delayed) ACK notifying that the reception buffer has expanded. . Then, the communication device 10 controls the ACK transmission frequency based on the simulated window size. In the present embodiment, descriptions of the same drawings as those of the first embodiment and the same elements as those in the drawings will be omitted. The configuration of the communication system and the configuration of the communication device 10 in this embodiment are the same as in the first embodiment.

[Flow of processing in the second embodiment]
FIG. 5 is a flowchart of processing executed by the communication device 10 according to this embodiment. Specifically, FIG. 5 is a flowchart showing a procedure for transmitting delayed ACK packets by changing the ACK transmission frequency according to conditions after the communication apparatus 10 receives data packets. The flowchart shown in FIG. 5 can be realized by the CPU 203 of the communication device 10 executing a control program stored in the ROM 202 to perform calculation and processing of information and control of each hardware.

The processing of S501-S502 is the same as the processing of S401-S402 in FIG. In S503, the ACK control unit 308 checks whether the last ACK packet transmitted by the transmission processing unit 305 has notified other communication devices 20 that the window size has been increased. For example, the ACK control unit 308 checks whether the last ACK packet transmitted by the transmission processing unit 305 includes information on the extended window size. If it has been notified that the window size has increased (YES in S503), the process proceeds to S504, and if it has not been notified that the window size has increased (NO in S503), the process proceeds to S512.

In S504, the ACK control unit 308 does not recognize that the window size of the other communication device 20 has increased due to a packet loss or the like (the other communication device has failed to receive an ACK packet due to the communication situation or the like). Assuming that, set a simulated window size. Note that the simulated window size is the window size notified by the ACK immediately before the latest ACK. Then, ACK control section 308 compares the set simulated window size with a predetermined threshold. If the simulated window size is smaller than the predetermined threshold (YES in S504), the process proceeds to S505, and if the simulated window size is equal to or greater than the predetermined threshold (NO in S504), the process proceeds to S508. Note that the predetermined threshold is, for example, set in advance in the communication apparatus 10 in the same manner as the threshold used in the process of S403 in FIG. value and can be higher.

The processing of S505 is the same as the processing of S404 in FIG. In S<b>506 , the ACK control unit 308 compares the simulated window size set in the process of S<b>504 with the total data size of data packets received from other communication devices 20 (received data size). The data packet is a data packet received from another communication device 20 after the transmission processing unit 305 has transmitted an ACK packet notifying that the window size has been increased. If the simulated window size is smaller than the total received data size (YES at S506), the process proceeds to S507, and if the simulated window size is greater than or equal to the total received data size (NO at S506), the process proceeds to S508. move on.

In S507, the ACK control unit 308 restores the ACK transmission frequency. That is, ACK control section 308 changes the reference number of packets for delayed ACK transmission to the initial value (value before change in S505). It should be noted that when the process proceeds to S507 as a result of the determination in S506, the possibility that the other communication device 20, which was the reason for setting the simulated window size, did not recognize that the window size has increased has disappeared. means that Therefore, since the set simulated window size becomes unnecessary in S507, the ACK control unit 308 may discard it. The processing of S508-S511 is the same as the processing of S405-S408 in FIG. The processing of S512-S513 is the same as the processing of S403-S404. The processing of S514-S515 is the same as the processing of S409-S410.

As described above, the communication device 10 adjusts the ACK transmission frequency according to the simulated window size, and changes the reference number of packets for delayed ACK transmission to a smaller value. As a result, even if the other communication device 20 does not recognize that the window size of the communication device 10 has increased due to packet loss or the like, the ACK transmission frequency before the change should be transmitted after waiting for the delay time. can reduce the number of delayed ACK packets that were As a result, it is possible to prevent deterioration of communication performance.

(Third embodiment)
Communication processing according to the third embodiment will be described below. In this embodiment, the communication device 10 adjusts the window size notified by the ACK packet according to conditions. In the present embodiment, descriptions of the same drawings as those of the first embodiment and the same elements as those in the drawings will be omitted. The configuration of the communication system and the configuration of the communication device 10 in this embodiment are the same as in the first embodiment.

[Flow of processing in the third embodiment]
FIG. 6 is a flowchart of processing executed by the communication device 10 according to this embodiment. Specifically, FIG. 6 is a flowchart showing a procedure for transmitting delayed ACK packets by changing the ACK transmission frequency according to conditions after the communication apparatus 10 receives data packets. The flowchart shown in FIG. 5 can be realized by the CPU 203 of the communication device 10 executing a control program stored in the ROM 202 to perform calculation and processing of information and control of each hardware.

The processing of S601-S604 is the same as the processing of S401-S404 in FIG. Note that the process of S604 may not be included in this flowchart. That is, in the case of NO in S604, ACK control section 308 does not need to temporarily change the reference number of packets for delayed ACK transmission to a smaller value.

In S605, the ACK control unit 308 determines that the window size is the data size that can be received at the ACK transmission frequency (a value obtained by multiplying the reference number of packets for delayed ACK transmission by the data size of one packet (eg, MSS)). Check whether it is an integer multiple. If the window size is not an integer multiple of the data size that can be received with the ACK transmission frequency (YES in S605), the process proceeds to S506, where the window size is an integer multiple of the data size that can be received with the ACK transmission frequency. If so (NO in S605), the process proceeds to S507.

In S606, the ACK control unit 308 adjusts the window size notified in the ACK packet transmitted by the transmission processing unit 305 to an integral multiple of the data size that can be received at the ACK transmission frequency. For example, if the data size of one data packet is MSS, the current window size is 7 MSS (for 7 data packets), and the reference number of packets for delayed ACK transmission is 2, the ACK control unit 308 uses an integer of 2. A window size of 6MSS (for 6 data packets), which is double, is determined to be notified by an ACK packet. The processing of S607-S612 is the same as the processing of S405-S410 in FIG. Note that the window size is not updated in S608.

As described above, the communication device 10 changes the ACK transmission frequency to a value smaller than the current setting according to the window size. At that time, the communication device 10 adjusts the window size notified by the ACK to be transmitted to an integral multiple of the data size that can be received at the ACK transmission frequency. Even if there is a possibility of receiving fractional packets less than the ACK transmission frequency, by adjusting the window size, the delayed ACK that should have been transmitted after waiting for the delay time with the ACK transmission frequency before the change is reduced. The number can be reduced, and deterioration of communication performance can be prevented.

(Other embodiments)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing to It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the claims are appended to make public the scope of the invention.

10 communication device, 20 other communication device

Claims (11)

A communication device,
receiving means for receiving packets from other communication devices;
storage means for storing data of the packet received by the receiving means in a reception buffer;
control means for controlling a reference number of packets used as a basis for sending acknowledgment (ACK) packets for packets received by said receiving means;
transmitting means for transmitting the ACK packet when the number of packets received by the receiving means exceeds the reference number of packets;
The communication device, wherein the control means controls the reference number of packets so that the frequency of transmission of the ACK packets increases when a window size indicating the free space of the reception buffer is less than a predetermined threshold. . An initial value is set for the reference number of packets, and the control means changes the reference number of packets to a number lower than the initial value when the window size indicating the free space of the reception buffer is less than a predetermined threshold. The communication device according to claim 1, characterized in that: 3. The communication apparatus according to claim 2, wherein when the number of packets received by said receiving means exceeds said reference number of packets, said control means updates said reference number of packets to said initial value. . 4. The communication apparatus according to claim 2, wherein said transmitting means includes information on a window size according to the data stored in said reception buffer in said ACK packet and transmits it. Even when the ACK packet is transmitted by the transmission means, the control means, if the window size included in the ACK packet transmitted before the ACK packet is less than the predetermined threshold, the reference 5. The communication device according to claim 4, wherein the number of packets is changed to a number lower than the initial value. A window in which the total data size of the packets received by the receiving means is included in the ACK packet transmitted before the ACK packet after the reference packet number is changed to a number lower than the initial value by the control means. 6. The communication apparatus according to claim 5, wherein when the number of packets exceeds the size, the control means updates the reference number of packets to the initial value. determining means for determining whether the window size is an integral multiple of the data size of the reference number of packets when the window size is less than the predetermined threshold;
When the determining means determines that the window size is not an integer multiple of the packet data size of the reference number of packets, the window size is updated so as to be an integer multiple of the data size of the reference number of packets. an update means to
7. A communication device according to any one of claims 1 to 6, further comprising: 8. The communication apparatus according to any one of claims 1 to 7, wherein the predetermined threshold is a value equal to or greater than the value obtained by multiplying the reference number of packets by the data size of the packets. 9. The apparatus according to any one of claims 1 to 8, wherein the communication device is a communication device that performs TCP/IP communication, and the data size of the packet is MSS (Maximum Segment Size) in TCP (Transmission Control Protocol). A communication device according to any one of the preceding claims. A control method for a communication device,
a receiving step of receiving packets from another communication device;
a storing step of storing the data of the packet received in the receiving step in a reception buffer;
a control step of controlling a reference number of packets used as a reference for sending acknowledgment (ACK) packets for packets received in the receiving step;
a transmission step of transmitting the ACK packet when the number of packets received in the reception step is equal to or greater than the reference number of packets;
In the control step, the reference number of packets is controlled so as to increase the frequency of transmission of the ACK packets when a window size indicating the free space of the reception buffer is less than a predetermined threshold. . A program for causing a computer to function as the communication device according to any one of claims 1 to 9.

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