JP2008109698A - Packet communication apparatus, packet communication method, and packet communications program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of enabling real time communication in a communication protocol for applying retransmission control and congestion control to a packet loss. <P>SOLUTION: A data receiving section 202 receives the packets from both of a communication protocol stack 203 for receiving packets from a network interface 201 and giving the packet to the data receiving section and a snoop packet output section 204 for snooping the packets received by the network interface 201 and gives the resultant packets to the data receiving section 202, and provides received data to an application so as to avoid the duplication of the packets, that is, in a way of avoiding the duplication of the packets with the same sequence number. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention provides a communication protocol (for example, TCP (Transmissi
on Communication Protocol)), and more particularly, to a communication apparatus, a communication method, and a communication program for realizing data communication that requires real-time performance such as video and audio.

In recent years, there has been an increase in communication applications in which data is divided into packets and transmitted from the transmission side to the reception side, and reproduced and reproduced as data on the reception side. For example, IP on the Internet
Talk (VoIP), video conferencing, movie and live video distribution. In such an application, if the data is transmitted from the transmission side as a packet and is reproduced on the reception side within a certain time, the quality as a communication application is kept high, that is, the sound is reproduced without interruption or the image is reproduced. This is important for retransmitting without interruption. That is, in such a communication application, it is required to minimize the delay time from when a packet is transmitted until data is reproduced. In the following, it is necessary to minimize the delay time from when such a packet is transmitted until the data is reproduced.
It is expressed by the expression that real-time property is required.

As a communication protocol in such an application that requires real-time properties, a protocol that does not involve retransmission control is often used. One specific communication protocol is UDP (User Datagram Packet). UDP is a communication protocol that aims to be lighter and faster than reliability for transferring packets without loss. Even if the transmitted packet is lost before it arrives at the receiving terminal or the like (when a packet loss occurs), the lost packet (lost packet) is not retransmitted. For this reason, if it is allowed that some data that cannot be reproduced on the receiving side is present, a delay due to retransmission does not occur.

However, depending on the environment of the user using the communication application, a protocol that does not involve retransmission control may not be used. For example, there may be mentioned a case where a firewall or a proxy is installed in a company, university, or home network for security reasons such as blocking or filtering of external packets.

In such an environment, HTTP (Hyper Text Tran) that passes through the firewall or proxy can be used as a method of communicating the data of the aforementioned application across the firewall or proxy.
Patent Document 1 discloses a method for realizing communication by exchanging data packets using sfer Protocol. Here, HTTP is a communication protocol defined on TCP with retransmission control.

Japanese Patent Laid-Open No. 2001-86163 (pages 4-8, FIG. 1) Sumitha Bhandarkar, "A Study of the Growth and Development of Video Streaming over the Internet", [Search August 26, 2004], Internet <http://students.cs.tamu.edu/sumitha/courses/cpsc689- 606 / hw5.doc>

A problem that occurs when a protocol that involves retransmission control is used in an application that requires real-time processing will be described with reference to FIG. 31 using TCP as an example.

FIG. 31 is an example of a processing sequence of TCP retransmission control. The transmission side assigns a sequence number and transmits a data packet. When the receiving side receives the data packet, it sends a packet (hereinafter abbreviated as ACK) including the “ACK” information with a sequence number to notify the sending side of the data packet (response). Pass the received data to.

For example, when a data packet with sequence number 1 (shown as # 1 in FIG. 31) is received (3101), the receiving side sends an ACK with sequence number 1 to the transmitting side (3102), and at the same time, the data packet data is sent. Pass to the application (3103).

Here, it is assumed that the packet with the sequence number 2 is lost (3104). The receiver does not return any response because the packet has not arrived. In TCP, as described later, A contains the same sequence number.
Until the CK is continuously received for a predetermined number of times, the occurrence of packet loss is not recognized, so that the transmitting side transmits a packet of sequence number 3 (3105). On the receiving side, when the packet with sequence number 3 is received, it is detected that the packet with sequence number 2 has not arrived, and the contents are transmitted to the transmitting side. Specifically, the receiving side has sequence number 1
An ACK is transmitted to notify that the packets up to are received (3106). Since the ACK that indicates that the packets up to sequence number 1 have been received is already in 3102 and is the second transmission, the ACK transmitted in 3106 is called “Duplicated ACK” (in FIG. 31, Duplicated ACK). ACK) In general, there is no substantive difference between ACK and Duplicated ACK, but in the following, ACK and Duplicated ACK are used separately as much as possible in order to express that it is the second and subsequent ACK transmissions. .

The data of sequence number 3 received in 3105 is temporarily stored in the TCP protocol stack without passing to the application. Subsequently, the transmitting side transmits a data packet with sequence number 4 and sequence number 5 (3107, 3109), and the receiving side does not receive the packet with sequence number 2, and similarly transmits a duplicated ACK with sequence number 1. (3108, 3110), data packets of sequence number 4 and sequence number 5 are temporarily stored in the TCP protocol stack. In TCP, when a duplicated ACK is received as a parameter for the number of times set as a parameter, or three times in a typical implementation, it is detected that a packet loss has occurred, and a duplicate is received.
Control is performed to retransmit the next packet of the sequence number specified by ated ACK. Here, the packet with sequence number 2 is retransmitted (3111). On the receiving side, when a packet with sequence number 2 is received at 3111, data up to sequence number 5 has been received, so an ACK with sequence number 5 is transmitted (3112). At the same time, the packet data of sequence numbers 2, 3, 4, and 5 are passed to the application (3113 to 3116).

As shown in this example, when packet loss occurs, received data is not passed to the application on the receiving side until the lost packet is retransmitted, so that there is a problem that a delay due to retransmission occurs. In this example, with the packet loss of sequence number 2 at 3104, 3117
The delay time shown in The tolerance of delay time in the application is
If it is less than the time indicated by 3117, the execution of the application will be disturbed.
For example, in the case of an application that reproduces video / audio, there is a possibility that the reproduction data will not be in time for the reproduction time, and the reproduction may be interrupted.

In response to these issues, the video / audio playback time is set as a threshold, a dummy ACK is sent to a data packet that does not reach the threshold, and a data packet that has not been received is received. A method has also been proposed in which TCP retransmission control is prevented from being performed by returning an ACK response to the transmitting side as if it has been performed, and waste of retransmission processing is eliminated (for example, Non-Patent Document 1). In this case, the data packet that has not been subjected to retransmission control is not received at the receiving side terminal, but the subsequent packet is received. Therefore, the data of the data packet subsequent to the data packet that has not been subjected to retransmission control is not received by the application. It becomes possible to pass. Thereby, the delay accompanying retransmission of a packet can be suppressed.

However, in protocols involving retransmission control, congestion control is often performed in cooperation with retransmission control. For example, in TCP, congestion control is performed by adjusting the congestion window size in addition to retransmission control. Congestion control is a mechanism that attempts to eliminate network congestion as much as possible by keeping the transmission rate low when the data transmission side performs retransmission. For example, in TCP, when Duplicated ACK is received three times in succession, processing is performed to avoid network congestion by keeping the number of packets transmitted at the same time as retransmission processing low.

The purpose of this control is to reduce network congestion as soon as possible by assuming a network congestion as a cause of packet loss and keeping the transmission rate low, that is, by reducing the congestion window size.

Although the method proposed in Non-Patent Document 1 has the effect of suppressing retransmission control, the sender side no longer performs congestion control, so if the network is congested, the congestion level will be further accelerated. The problem is inherent.

An object of the present invention is to provide a packet communication device, a packet communication method, and a packet communication program capable of realizing both a reduction in delay until data reception associated with retransmission control and congestion control. This means that applications that require real-time capability can be executed without being affected by delays associated with retransmission control, using a protocol with retransmission control and congestion control functions, and at the same time the entire network. It is possible to perform appropriate congestion control.

In order to achieve such an object, a first communication device of the present invention includes a network interface that receives a packet, a communication protocol stack that receives a packet from the network interface and passes the packet to a data receiving unit, and snoops the packet received by the network interface The packet data is received from the snoop packet output unit passed to the data receiving unit, the communication protocol stack and the snoop packet output unit, and there is no duplication of the packet data, that is, the packet data with the same sequence number is duplicated. It is characterized by comprising a data receiving unit that provides the received data to the application.

The second communication device according to the present invention includes a network interface that receives a packet, a communication protocol stack that receives the packet from the network interface and provides it to an application, monitors the packet received by the network interface, and the congestion control is performed on the transmission side. The packet monitoring unit that monitors the timing at which Duplicated ACK is transmitted for the number of times executed in the network interface unit on the receiving side and notifies the dummy packet generation unit of the timing, and the dummy packet triggered by the notification And a dummy packet generation unit that generates and transmits the packet to the network interface.

A third communication device according to the present invention monitors a network interface that receives a packet, a communication protocol stack that receives the packet from the network interface and provides it to an application, and a packet received by the network interface, and a duplicated ACK is transmitted. Dummy Dupl at that timing
It is characterized by comprising an ACK generation unit that generates one or more icate ACKs and sends them to the network interface unit.

The fourth communication device according to the present invention includes a network interface that transmits and receives packets, a communication protocol stack that receives packets from the network interface and provides them to an application, monitors packets received by the network interface, and receives received packets as duplicates. If it is ACK, dummy packet generator and A
A packet monitoring unit for notifying the CK generation unit, and one or more D in response to the notification from the packet monitoring unit
Generates an uplicated ACK and sends it to the network interface unit, and receives a notification from the packet monitoring unit, generates a dummy packet of the lost packet, and generates a dummy packet to send to the communication protocol through the network interface unit It is comprised from a part.

A fifth communication apparatus according to the present invention monitors a network interface that receives a packet, a communication protocol stack that receives a packet from the network interface and provides it to an application, and a packet that is transmitted and received by the network interface, and the sequence number sequence. When the packet is broken, the dummy packet generator is notified, and if the broken packet is included in a plurality of packets that arrive in succession next, the packet is broken. If the received packet does not arrive, the packet monitoring unit that notifies the ACK generation unit and the notification from the packet monitoring unit receives the notification from the packet monitoring unit, generates the dummy packet, and sends it to the network interface and the notification from the packet monitoring unit Receive multiple duplicated ACKs AC that, and transmits to the network interface
And a K generator.

The sixth communication device according to the present invention monitors a network interface that receives a packet, a communication protocol stack that receives a packet from the network interface and provides it to an application, and a packet that is transmitted and received by the network interface, and the sequence number sequence. The packet monitoring unit for notifying the resendability judgment unit and the resendability judgment flag that is valid for a certain period of time are confirmed, and if the resendability judgment flag is not set, the resendability judgment flag is set. Simultaneously, the dummy packet generation unit and the ACK generation unit are notified, and when the retransmission permission determination flag is set, the retransmission permission determination unit that notifies the dummy packet generation unit and the notification from the retransmission permission determination unit Generate dummy packets, network in A dummy packet generator to be transmitted to over the face, receiving the notification from the retransmission judging unit generates a plurality of Duplicated ACK, characterized the ACK generating unit to be transmitted to the network interface, in that they are composed of.

The seventh communication device according to the present invention receives a packet from the network interface, receives a packet from the network interface, provides a communication protocol stack to the application, monitors a packet transmitted / received by the network interface, and receives a duplicated ACK. A packet monitoring unit that notifies the ACK generation unit when it detects a packet, and an ACK generation unit that receives a notification from the packet monitoring unit, generates a plurality of Duplicated ACKs, and transmits them to the communication protocol stack. It is characterized by.

The eighth communication device according to the present invention receives a packet from the network interface, receives a packet from the network interface, provides a communication protocol stack to the application, monitors a packet transmitted / received by the network interface, and receives a duplicated ACK. Is detected, and the packet monitoring unit that notifies the retransmission permission determination unit checks whether the retransmission permission determination flag that is valid for a certain period is set. If the retransmission permission determination flag is not set, the retransmission permission determination flag is set. A plurality of Duplicat when receiving a notification from the retransmission determination unit and the retransmission determination unit for notifying the ACK generation unit
an ACK generation unit that generates an ed ACK and transmits the ed ACK to the communication protocol stack.

The first effect of the present invention is that it is possible to reduce data reproduction delay in an application generated by retransmission control when packet loss occurs when data is transmitted / received by a communication protocol with retransmission control in an application that requires real-time performance. is there.

The reason is that, even when a packet loss occurs during data transmission / reception, control is performed to suppress delay due to retransmission control of the lost packet.

The second effect of the present invention is that, when data is transmitted / received in a communication protocol that involves retransmission control and congestion control in an application that requires real-time characteristics, data that accompanies retransmission control is reproduced without impairing congestion control. The delay can be reduced.

The reason for this is that even when control is performed to suppress delay due to retransmission control, congestion control is not suppressed by appropriately transmitting packets necessary for congestion control.

The third effect of the present invention is that the first or second effect can be realized without modifying the communication protocol. The first or second effect can be obtained without affecting other applications using the same communication protocol on the same terminal.

The reason for this is that although it is linked to the communication protocol stack by controlling the delay by retransmission control and sending out the packets necessary for congestion control to the communication protocol stack via the network interface, it is independent. This is because it can be realized as a functional unit.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Figure
1 is a configuration diagram showing an overall connection relationship of an embodiment of a communication apparatus of the present invention. Sender terminal 1
10 and the receiving terminal 120 are connected via a network 130. The transmission-side terminal 110 includes a transmission-side communication device 111 that transmits a packet to the network 130 and a transmission-side application 112 that transmits packet data to the network 130 through the transmission-side communication device 111. The reception-side terminal 120 includes a reception-side communication device 121 that receives a packet from the network 130, and a reception-side application 122 that captures packet data from the reception-side communication device 121. Note that the roles of the transmitting side and the receiving side of the transmitting side terminal 110 and the receiving side terminal 120 are fixed for convenience of explanation, and there is actually no problem if the voluntary role is exchanged and data is transmitted and received mutually. .

(First embodiment)
FIG. 2 is a configuration diagram of the first embodiment of the receiving communication device according to the present invention. Referring to FIG. 2, a receiving-side communication device (hereinafter, communication device 200) according to the present invention includes a network interface 201, a data receiving unit 202, a communication protocol stack 203, and a snoop packet output unit 204. These means operate as follows.

A network interface 201 is connected to the network 130 in FIG. 1 and transmits and receives packets. Data receiving unit 202 includes communication protocol stack 203 and snoop packet output unit
Packet data is received from 204, and duplicated packets are discarded so that there is no duplication of packet data. The receiving-side application 122 in FIG. 1 receives packet data from the data receiving unit 202. The communication protocol stack 203 manages packet transmission / reception through the network interface 201. The snoop packet output unit 204 snoops the received packet from the network interface. The snoop process performed here refers to a process of copying a specific packet received by the network interface. Thereafter, this flow is repeated.

As shown in FIG. 29, the communication protocol stack 203 can be realized in multiple layers as a protocol stack 2031 on the network interface side and a socket interface 2032 serving as an interface on the data receiving unit side. Further, as shown in FIG. 30, the snoop packet output unit 204 can also be hierarchically implemented as a packet snoop unit 2041 on the network interface side and a snoop interface 2042 serving as an interface on the data receiving unit side. . This also applies to the communication protocol stack and the packet monitoring unit in the second to eighth embodiments described later.

Next, the overall operation of the present embodiment will be described in detail with reference to the configuration diagram of FIG. 2 and the flowchart of FIG.

The snoop packet output unit 204 of the communication device 200 snoops the arrival packet from the network interface 201 (step S101). The data receiving unit 202 receives packet data from the snoop packet output unit 204 (step S102). The data receiving unit 202 receives packet data from the communication protocol stack 203 in parallel with step S102 (step S111). The data receiving unit 202 discards one of the packet data if there is a duplicate received so that there is no duplication with the packet data received in S102 of FIG. 2 (step S103). An application (not shown) receives packet data from the data reception unit 202 and reproduces the data (step S104).

Next, the operation of the embodiment of the present invention will be specifically described based on an example in which TCP / IP is adopted as a communication protocol shown in the sequence diagram of FIG. In the following, the number of times a duplicated ACK is received for determining whether to perform congestion control and retransmission control is set to three times that is generally adopted in TCP / IP. In the following description and drawings, “#L” represents a packet with sequence number L, “ACK M” represents an ACK with sequence number M, and “Dup ACK N
"Represents a Duplicated ACK with a sequence number N.

The network interface 201 of the communication apparatus receives a data packet of sequence number 1 from the transmission-side terminal 110 through the network 130 in FIG. 1 (401). The communication protocol stack 203 acquires the data packet from the network interface 201 (402).
[ACK 1] of sequence number 1 is sent to the network interface 201 (403). The network interface 201 transmits [ACK 1] to the terminal 110 on the transmission side (408). The communication protocol stack 203 transmits the packet data to the data receiving unit (405). Prior to or in parallel with the communication protocol stack 203 acquiring the packet, the snoop packet output unit 204 snoops the data packet from the network interface 201 (404),
The data is transmitted to the data receiving unit 202 (406). Since the data reception unit 202 has acquired the data packet with the sequence number 1 in duplicate, discards one of them and transmits only one of the packet data received at 405 or 406 to an application (not shown) (407) ).

Next, it is assumed that the packet with the sequence number 2 is lost (409), and the packet with the sequence number 3 arrives at the network interface 201 from the transmission side terminal 110 (410). The communication protocol stack 203 acquires the data packet from the network interface 201 (4
11) Since the data packet of sequence number 2 has not been received yet, Duplicated AC
[Dup ACK 1] called K is sent to the network interface 201 (412). The network interface 201 transmits [Dup ACK 1] to the transmission side terminal 110 (416). The communication protocol stack 203 does not transmit the packet data to the data receiving unit 202 because it has not received the data packet with the sequence number 2. Prior to or in parallel with the communication protocol stack 203 acquiring the packet, the snoop packet output unit 204 snoops the data packet from the network interface 201 (413) and transmits it to the data receiving unit 202 (414). The data receiving unit 202 transmits the packet data received from the snoop packet output unit 204 at 414 to an application (not shown) (415).

When the packets of sequence number 4 and sequence number 5 arrive, the same operation as when the packet of sequence number 3 arrives is repeated, and the transmitting terminal 110 receives two duplicated ACs.
K arrives (418,420). Further, the packet data of sequence number 4 and the packet data of sequence number 5 are sent from the data receiving unit 202 to the application (417, 419).

In the transmission side terminal 110, the congestion control is performed when the third duplicated ACK that reaches the congestion control trigger arrives continuously (420). At the same time, it is detected that the packet with sequence number 2 has been lost, and the packet with sequence number 2 is retransmitted (421). When the network interface receives the packet with the sequence number 2, the communication protocol stack 203 acquires the packet (422), generates [ACK 5], and sends it to the network interface 201 (423). Here, since the communication protocol stack has received packets up to sequence number 5, sequence number 5 is attached to ACK. Communication protocol stack 20
3 sends data packets with sequence numbers 2 to 5 to the data receiver 202 (425 to 428)
. Prior to or in parallel with the communication protocol stack obtaining the packet of sequence number 2, the snoop packet output unit 204 receives the data packet from the network interface 201 (424) and transmits it to the data receiving unit 202 ( 429). Since the data receiving unit 202 has already acquired data packets up to sequence number 5, it discards the packets of sequence numbers 2 through 5 received from 425 to 428.

In the above example, since the data of the packet with the sequence number 2 is not passed to the application, it is necessary for the application to cope with such packet loss. For example, applications such as video and audio often have technology to predict lost packet data from data received before and after the lost packet,
It is possible to respond by utilizing such technology.

Next, the effect of this embodiment will be described. In this embodiment, data received by the communication protocol stack is directly received from the network interface even if data cannot be provided to the application until the packet lost due to the reproduction control of the communication protocol stack is retransmitted. Snoop packet output unit snoops, data receiving unit 20
By receiving through 2, it is possible to receive subsequent packets before the lost packet is retransmitted. In the example of FIG. 4, the time delay indicated by 440 can be reduced.

Thereby, it is possible to continuously receive packets after the lost packet without being affected by retransmission control due to packet loss. For example, when the application reproduces video and audio, the video and audio can be reproduced without interruption.

Furthermore, in this embodiment, the snoop of the snoop packet output unit does not affect the retransmission control of the communication protocol, so the congestion control is executed. When data is transmitted / received by a communication protocol that involves retransmission control and congestion control in an application that requires real-time performance, it is possible to reduce a delay until data associated with retransmission control is reproduced without impairing congestion control.

In the present embodiment, the snoop packet output unit snoops directly from the network interface without going through the communication protocol stack. In other words, there is no need to modify the communication protocol. The communication protocol is often implemented as part of the computer's operation system (kernel), and in many cases it is difficult to make corrections. There is no need to put it in.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a configuration diagram of the second embodiment of the receiving communication device according to the present invention. Referring to FIG. 5, a receiving side communication apparatus (hereinafter, communication apparatus 500) according to the present invention includes a network interface 501, a communication protocol stack 502, a packet monitoring unit 503, and a dummy packet generation unit 504.
including. These means operate as follows. The network interface 501 is shown in FIG.
To transmit and receive packets. A communication protocol stack 502 manages transmission / reception of packets through the network interface 501. The received packet is sent to the receiving-side application 122 shown in FIG. 1 according to the control of the communication protocol. In this embodiment, since the configuration is such that duplicate data reception is not performed, the data reception section that deletes duplicate data in the first embodiment is not required as a configuration.

The packet monitoring unit 503 monitors packets transmitted / received via the network interface 501, and detects the transmission of Duplicated ACK. When the duplicated ACK is a trigger for congestion control in the communication protocol, that is, when the duplicated ACK is received on the transmission side, the packet monitoring unit 503 is a dummy packet generating unit.
Requests generation of dummy packets to 504. The dummy packet generation unit 504 generates a dummy packet and transmits it to the communication protocol stack 502 through the network interface 501. The dummy packet generated here is a packet having the same header information such as a sequence number included in the lost packet. There is no problem even if the data portion of the packet may be empty, or it may be duplicated data of the previously received data.

Next, the overall operation of the present embodiment will be described in detail with reference to FIG. 5 and FIG.
FIG. 6 is a flowchart showing the operation of the communication apparatus according to the second embodiment of the present invention.
The packet monitoring unit 503 of the communication device 500 monitors packets transmitted / received via the network interface 501 (S201 in FIG. 6).

The packet monitoring unit 503 detects the transmission of the Duplicated ACK from the transmitted / received packet, and the Duplicated ACK triggers congestion control in the communication protocol, that is,
When Duplicated ACK is received by the transmitting terminal, it is determined whether the ACK causes congestion control (S202 in FIG. 6). S201 and S202 are repeated until a predetermined number of times of Duplicated ACK serving as a trigger for congestion control is detected.

If it is determined that the duplicated ACK causes congestion control, the dummy packet generator 504
The dummy packet generation unit 504 generates a dummy packet and transmits it to the communication protocol stack 502 through the network interface 501 (S203 in FIG. 6). Here, the detected Duplicated ACK causing congestion control corresponds to the case where the third transmission of Duplicated ACK to which the same sequence number is added is detected when the communication protocol is TCP / IP. Thereafter, S201 to S203 are repeated.

Next, the operation of the embodiment of the present invention will be specifically described based on an example in which TCP / IP is used as the communication protocol shown in the sequence diagram of FIG. In the following, the number of times a duplicated ACK is received for determining whether to perform congestion control and retransmission control is set to three times that is generally adopted in TCP / IP.

The network interface 501 of the communication apparatus receives the data packet of sequence number 1 transmitted from the transmission side terminal 110 through the network 130 shown in FIG. 1 (701). The communication protocol stack 502 acquires data packets from the network interface 501.
(702), [ACK 1] with sequence number 1 is sent to the network interface 501 (703)
. The network interface 501 transmits [ACK 1] to the transmission side terminal 110 (705). The communication protocol stack 502 transmits the packet data of the sequence number 1 to the reception side application 122 shown in FIG. 1 (704).

Next, it is assumed that the packet of sequence number 2 is lost (706), and the packet of sequence number 3 arrives at the network interface 501 from the transmitting terminal 110 (707). The communication protocol stack 502 acquires the data packet from the network interface 501 (7
08) Since the data packet of sequence number 2 has not been received yet, [Dup ACK 1] called Duplicated ACK, which means that only the sequence number 1 has been received, is sent to the network interface 501 (709) ). The network interface 501 transmits [Dup ACK 1] to the transmission side terminal 110 (710). Since the communication protocol stack 502 has not received the data packet with the sequence number 2, the communication protocol stack 502 does not transmit the packet data with the sequence number 3 to the receiving-side application 122.

When the packets of sequence number 4 and sequence number 5 arrive, the same operation as when the packet of sequence number 3 arrives is repeated, and the transmitting terminal 110 receives Duplicated ACK [ACK
1] arrives (711 to 718).

When the packet monitoring unit 503 detects a third consecutive duplicated ACK that triggers congestion control (718, 719), it requests the dummy packet generation unit 504 to generate a dummy packet (720).
. The dummy packet generation unit 504 generates a dummy packet with the sequence number 2 and transmits it to the communication protocol stack 502 through the network interface 501 (721,722). The communication protocol stack 502 transmits the dummy packet with the sequence number 2 to the reception-side application 122 (723), and simultaneously transmits the already received packets with the sequence numbers 3 to 5 to the reception-side application 122 (724 to 726). .

In addition, since the communication protocol stack 502 has received the packets up to sequence number 5, it transmits ACK of sequence number 5 (728, 729).

In the transmitting terminal 110, the third duplicated ACK that triggers the congestion control is continuously set to 718.
Congestion control works when it arrives at. At the same time, it is detected that the packet of sequence number 2 has been lost, and the packet of sequence number 2 is retransmitted (727). The network interface 501 receives this retransmission packet (sequence number 2) (727), and the communication protocol stack 502 acquires the packet (730). However, the packet up to sequence number 5 has been received so far. Upon reception of this retransmission packet (sequence number 2), an ACK with sequence number 5 is generated and sent to the network interface 501 (731).
The communication protocol stack 502 discards the packet received in duplicate, that is, the data packet with the sequence number 2 in this example (733).

  Next, the effect of this embodiment will be described.

In this embodiment, even when data cannot be provided to the application until the lost packet due to the reproduction control of the communication protocol stack is retransmitted, the dummy packet generation unit generates a dummy packet and sets the communication protocol. By providing, it is possible to receive a packet before the lost packet is retransmitted. In the example of FIG. 7, from the time (723) when the data of the dummy packet with sequence number 2 arrives at the receiving side application to the time (741) when the data of the packet with sequence number 2 arrives at the receiving side application by the conventional method. It is possible to reduce the delay of the time. That is, it is possible to reduce the time from when a duplicated ACK is sent as a trigger for retransmission control until the lost packet is retransmitted, and to reduce the influence of retransmission control due to packet loss.
Taking the case where an application reproduces video and audio as an example, video and audio can be reproduced without interruption.

Furthermore, in this embodiment, Duplicat that triggers congestion control to generate dummy packets
Since it waits for ed ACK to be transmitted, it does not affect the congestion control of the communication protocol. Therefore, when data is transmitted / received by a communication protocol that involves retransmission control and congestion control in an application that requires real-time performance, it is possible to reduce a delay until data associated with retransmission control is reproduced without impairing congestion control.

In this embodiment, the packet monitoring unit directly monitors the network interface without going through the communication protocol stack. In other words, there is no need to modify the communication protocol. The communication protocol is often implemented as part of the computer's operation system (kernel), and in many cases it is difficult to make corrections. There is no need to put it in.

(Third embodiment)
Next, an embodiment of the third invention of the present invention will be described with reference to the drawings.

FIG. 8 is a configuration diagram of the third embodiment of the receiving communication device according to the present invention. Referring to FIG. 8, a receiving side communication apparatus (hereinafter, communication apparatus 800) according to the present invention includes a network interface 801, a communication protocol stack 802, a packet monitoring unit 803, and an ACK generation unit 804.

These means operate as follows. A network interface 801 is connected to the network 130 shown in FIG. 1 and transmits and receives packets. The communication protocol stack 802 manages packet transmission / reception, and sends packet data to the receiving-side application 122 shown in FIG. 1 according to the operation of the communication protocol. The packet monitoring unit 803 monitors packets transmitted / received via the network interface 801 and detects the transmission of Duplicated ACK. D
Upon detecting the transmission of the uplicated ACK, the packet monitoring unit 803 sends a dummy Duplicate to the ACK generation unit 804.
Request generation of atd ACK. The ACK generator 804 has the number of Dups necessary to generate congestion control.
A licated ACK is generated and transmitted to the transmitting terminal 110 shown in FIG.

Next, the overall operation of the present exemplary embodiment will be described in detail with reference to the configuration diagram of FIG. 8 and the flowchart of FIG. The packet monitoring unit 803 of the communication device 800 monitors packets transmitted and received via the network interface 801 (S301 in FIG. 9). Packet monitoring unit 803
Detects the transmission of Duplicated ACK from the transmitted / received packet (S302 in FIG. 9). Duplicate
d S301 and S302 are repeated until ACK is detected. When a Duplicated ACK is detected, a notification is sent from the packet monitoring unit 803 to the dummy ACK generating unit 804, and the dummy ACK generating unit 804 generates a number of Duplicated ACKs necessary to generate congestion control and retransmission control. Is transmitted to the network interface 801 (S303 in FIG. 9). Thereafter, step S301 to step S3
Repeat 03.

Next, the operation of the embodiment of the present invention will be specifically described based on an example in which TCP / IP is used as the communication protocol shown in the sequence diagram of FIG. It is assumed that retransmission control and congestion control are set to occur when three duplicated ACKs with the same sequence number are received.

The network interface 801 of the communication apparatus receives the data packet of sequence number 1 sent from the transmission side terminal 110 through the network 130 shown in FIG. 1 (1001).
The communication protocol stack 802 acquires a data packet from the network interface 801 (1002), and sends [ACK 1], which is an acknowledgment of sequence number 1, to the network interface 801 (1003). The network interface 801 sends [ACK 1] to the transmitting terminal 110.
Is transmitted (1005). The communication protocol stack transmits the packet data with the sequence number 1 to the reception-side application 122 (1004).

Next, it is assumed that the packet with the sequence number 2 is lost (1006), and then the packet with the sequence number 3 arrives at the network interface 801 from the transmission side terminal 110 (1007). Communication protocol stack 802 is a network interface for data packet with sequence number 3
Since it is obtained from 801 (1008) and the data packet of sequence number 2 has not been received yet, [Dup ACK 1] called Duplicated ACK of sequence number 1 is sent to the network interface 801 (1009). The network interface 801 sends [Du
p ACK 1] is transmitted (1010). Since the communication protocol stack 802 has not received the data packet with the sequence number 2, the communication protocol stack 802 does not transmit the data of the packet with the sequence number 3 to the reception-side application 122.

Here, the packet monitoring unit 803 receives a duplicated ACK from the network interface 801.
Is detected (processing of 1009 and 1010) (1011), the ACK generation unit 804 receives a duplicated message.
Request generation of ACK (1012). The ACK generation unit 804 calculates how many Duplicated ACKs in addition to the detected Duplicated ACK reaches the transmitting side terminal, so that retransmission control and congestion control occur.
As many dummy duplicated ACKs as the calculated number are generated. In this example, three
When Duplicated ACK arrives, retransmission control and congestion control occur, so two dummy Dups
A licated ACK is generated and transmitted (1013 to 1016).

When the sending terminal 110 receives a duplicated ACK that triggers retransmission control (1016)
Then, it is detected that the packet with sequence number 2 has been lost, and the packet with sequence number 2 is retransmitted (1017). Congestion control also works simultaneously with retransmission control. When the network interface 801 receives the packet with the sequence number 2, the communication protocol stack 802 obtains the packet (1018), and has received the packet with the sequence number 3 so far. Generated ACK and network interface
Through 801, the data is transmitted to the transmitting side terminal 110 (1021, 1022). The communication protocol stack 802 transmits the data of packets up to sequence number 3 that have already been received to the receiving-side application 122 (1019, 1020).

Next, the effect of this embodiment will be described. In this embodiment, when the packet monitoring unit detects a duplicated ACK at the network interface unit when the packet loss unit detects that the packet has been lost, the ACK generation unit includes a plurality of Duplicate so that retransmission control is performed immediately.
By additionally generating a ted ACK and transmitting it to the transmitting terminal, retransmission of the lost packet is executed earlier than before. For this reason, the time until the lost packet is retransmitted can be reduced as compared with the prior art. Taking the case of an application that reproduces video and audio as an example, video and audio can be reproduced without interruption.

Furthermore, in this embodiment, since the transmission of Duplicated ACK is promoted, congestion control of the communication protocol is not suppressed. Therefore, when data is transmitted / received by a communication protocol that involves retransmission control and congestion control in an application that requires real-time performance, it is possible to reduce a delay until data associated with retransmission control is reproduced without impairing congestion control.

In the present embodiment, the packet monitoring unit directly monitors the network interface without going through the communication protocol stack, and a newly generated Duplicated ACK is also transmitted directly to the network interface. In other words, there is no need to modify the communication protocol. The communication protocol is often implemented as part of the computer's operation system (kernel), and in many cases it is difficult to make corrections. There is no need to put it in.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 11 is a configuration diagram of the fourth embodiment of the receiving communication device according to the present invention. A receiving side communication apparatus (hereinafter, communication apparatus 1100) according to the present invention includes a network interface 1101, a communication protocol stack 1102, a packet monitoring unit 1103, a dummy packet generation unit 1104, and an ACK generation unit 1105.

These means operate as follows. The network interface 1101 is connected to the network 130 shown in FIG. 1, and transmits and receives packets. Communication protocol stack 110
2 manages packet transmission / reception, and transmits packet data to the reception-side application 122 shown in FIG. 1 according to the operation of the communication protocol. The packet monitoring unit 1103 monitors packets transmitted / received via the network interface 1101 and detects the transmission of Duplicated ACK. When detecting the transmission of Duplicated ACK, the packet monitoring unit 1103 notifies the dummy packet generating unit 1104 and the ACK generating unit 1105. Upon receiving the notification from the packet monitoring unit 1103, the dummy packet generation unit 1104 generates a dummy packet of a lost packet and transmits it to the communication protocol stack 1102 through the network interface 1101. ACK generator 110
5 receives the notification from the packet monitoring unit 1103, the number of Ds required to generate congestion control.
An uplicated ACK is generated and transmitted to the network interface 1101.

Next, the overall operation of the present embodiment will be described in detail with reference to the configuration diagram of FIG. 11 and the flowchart of FIG. The packet monitoring unit 1103 of the communication device 1100 monitors packets transmitted / received via the network interface 1101 (S401 in FIG. 12). The packet monitoring unit 1103 detects the transmission of the Duplicated ACK from the transmitted / received packet, and the Duplicated ACK
Is detected from the packet monitoring unit 1103 to the dummy generation unit 1104 and the ACK generation unit 1105. (S402 in FIG. 12). The dummy packet generation unit 1104 generates a dummy packet of the lost packet and transmits it to the communication protocol stack through the network interface 1101 (S403 in FIG. 12). At the same time, the ACK generation unit 1105 generates a plurality of Duplicated ACKs and transmits them to the transmitting side terminal 110 through the network interface 1101 (S404 in FIG. 12). At this time, the ACK generation unit 1105 generates and adds at least duplicated ACKs necessary for the transmission side terminal 110 to execute retransmission control and congestion control.

Next, the operation of the embodiment of the present invention will be specifically described based on an example in which TCP / IP is used as the communication protocol shown in the sequence diagram of FIG. It is assumed that retransmission control and congestion control are set to occur when three or more duplicated ACKs having the same sequence number are received.

The network interface 1101 of the communication apparatus receives the data packet with the sequence number 1 from the transmission side terminal 110 shown in FIG. 1 (1301). The communication protocol stack 1102 acquires a data packet from the network interface 1101 (1302), and sends an acknowledgment [ACK 1] of sequence number 1 to the network interface 1101 (1303). The network interface 1101 transmits [ACK 1] to the transmission side terminal 110 (1305). The communication protocol stack 1102 transmits the packet data of the sequence number 1 to the reception side application 112 shown in FIG. 1 (1304).

Next, the packet with sequence number 2 is lost, and then the sequence number from the sending terminal 110
It is assumed that the third packet reaches the network interface 1101 (1306, 1307). The communication protocol stack 1102 obtains the data packet with the sequence number 3 from the network interface 1101 (1308), and has not yet received the data packet with the sequence number 2, so it is a Duplicated ACK with the sequence number 1 [Dup ACK 1]. Is sent to the network interface 1101 (1309). The network interface 1101 is the transmission side terminal 110
[Dup ACK 1] is transmitted to (1310). Since the communication protocol stack 1102 has not received the data packet with the sequence number 2, it does not transmit the packet data with the sequence number 3 to the application.

Here, the packet monitoring unit 1103 receives the duplicated A from the network interface 1101.
When it is detected that CK has been sent (processes 1309 and 1310) (1311), dummy packet generator 1104
Request generation of a dummy packet, and request the ACK generation unit 1105 to generate a plurality of duplicated ACKs (1
312,1313). The dummy packet generation unit 1104 generates a dummy packet of the lost packet with the sequence number 2 and transmits the communication protocol stack through the network interface 1101.
It is transmitted to 1102 (1318).

Communication protocol stack 1102 determines that the packet with sequence number 2 has been received (13
19) Receives data from packets with sequence number 2 and sequence number 3
Sent to 22 (1320, 1321). Immediately before or immediately before the generation of the dummy packet, the ACK generation unit 1105 calculates how many Duplicated ACKs are sent to the transmitting terminal in addition to the detected Duplicated ACK, and calculates the retransmission control and congestion control. Duplicated ACKs corresponding to the number are generated (1314, 1316). In this example, when three duplicated ACKs arrive, retransmission control occurs, so two additional duplicated ACKs are generated and the network interface 1101 is generated.
(1314 to 1317).

On the other hand, when the communication protocol stack 1102 obtains a dummy packet (1319), it means that the packet up to the sequence number 3 has been received so far, so [ACK 3] with this sequence number 3 is generated to generate the network. It is sent to the interface 1101 (1323).

The transmitting terminal 110 detects that the packet with the sequence number 2 has been lost when a predetermined number of Duplicated ACKs that trigger retransmission control, in this example, when three Duplicated ACKs arrive (1317). The packet with sequence number 2 is retransmitted (1322). On the sending side,
Congestion control is executed simultaneously with retransmission control. However, at this point, [ACK of sequence number 3
[3] explains that it did not reach the sender.

When the network interface 1101 receives the retransmitted packet with the sequence number 2 (1322), the communication protocol stack 1102 acquires the packet with the sequence number 2 (13).
25) Since it is supposed that the packet up to sequence number 3 has been received so far,
[ACK 3] indicating that the packet up to sequence number 3 has been received is generated and sent to the network interface 1101 (1326). At this time, the communication protocol stack 1102
The packet of sequence number 2 received in 1325, which has been determined to have already been received, is discarded.

Next, the effect of this embodiment will be described. In this embodiment, when the packet monitoring unit detects a duplicated ACK at the network interface unit when the packet loss unit detects that the packet has been lost, the ACK generation unit includes a plurality of Duplicate so that retransmission control is performed immediately.
A dummy packet generator generates a dummy packet of a lost packet at the same time as generating ted ACK and transmitting it to the transmitting terminal. Therefore, the receiving application can receive the data of the subsequent received packet without waiting for the retransmission of the lost packet.
The delay until data reproduction can be reduced as compared with the third embodiment. More specifically, in the method described in the third embodiment, the receiving side application can receive the packet data only at the timings 1019 and 1020 in FIG. 10, but the data at the timings 1320 and 1321. Can be received, and the delay can be reduced as compared with the third embodiment.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to the drawings.

The configuration of the fifth embodiment of the receiving communication apparatus according to the present invention is the same as the configuration of the fourth embodiment shown in FIG. A receiving side communication device (hereinafter referred to as a communication device 1100) according to the present invention includes a network interface 1101, a communication protocol stack 1102, a packet monitoring unit 1103,
A dummy packet generation unit 1104 and an ACK generation unit 1105 are included.

These means operate as follows. The network interface 1101 is connected to the network 130 shown in FIG. 1, and transmits and receives packets. The communication protocol stack 1102 manages packet transmission / reception. The packet monitoring unit 1103 is connected to the network interface 11
Monitor packets sent and received via 01 and monitor packet sequence numbers. Observe when the sequence number of the packet is broken, that is, the sequence number of the packet is not increasing one by one, the sequence number is not continuous, or the packet with the larger sequence number arrives first If the packet is received, the packet monitoring unit 1103 requests the dummy packet generation unit 1104 to generate a dummy packet having a sequence number that should be received. The dummy packet generator 1104 generates a dummy packet, and the network interface 1101
To the communication protocol stack 1102.

In addition, the packet monitoring unit 1103 loses the order, that is, the packet that has not arrived in the correct order is the packet that continuously arrives next, for example, if the communication protocol is TCP, the judgment of congestion control and retransmission control Since the number of duplicated ACKs required for the network is generally 3 or more, in addition to the packets that have already arrived, the next two packets that arrive will contain packets that have not yet arrived. Monitor whether or not. If the corresponding packet is not included, the packet monitoring unit 1103 determines that packet loss has occurred, and the ACK generation unit 1
Request 105 to generate multiple duplicated ACKs.

The ACK generation unit 1105 is a duplicated AC required for causing the transmission side terminal to generate congestion control.
In the standard TCP implementation, multiple Ks are generated, and three or more Duplicated ACKs are generated and transmitted to the transmitting terminal. The transmitting terminal performs retransmission control and congestion control in order to receive three or more duplicated ACKs.

Next, the overall operation of the present embodiment will be described in detail with reference to the configuration diagram of FIG. 11 and the flowchart of FIG.

The packet monitoring unit 1103 monitors the sequence numbers of packets transmitted / received via the network interface 1101 (S501 in FIG. 14). When the order of the packet sequence numbers is broken, for example, when it is observed that the packet sequence numbers arrive without increasing one by one or the packet with the larger sequence number arrives first, the packet monitoring unit 1103 requests the dummy packet generation unit 1104 to generate a dummy packet (S502 in FIG. 14), and the dummy packet generation unit 1104 receives an unarrived packet in S502, that is, a packet that should be received in the original sequence order. An incomplete packet and a dummy packet with the observed sequence number are transmitted to the communication protocol stack 1102 through the network interface 1101 (S503 in FIG. 14).

The packet monitoring unit 1103 may receive a packet that arrives in succession next to an unarrived packet, for example, a TC
If it is P, there is a possibility that packets will not arrive according to the sequence number, so in TCP, it is expected that packets in sequence will arrive while receiving multiple packets, generally three times. In order to perform retransmission control and congestion control only when the packet does not arrive at the packet, whether it is included in the two packets that arrive next, that is, the three packets that are received consecutively, in addition to the packet that has already arrived Is monitored (S504 in FIG. 14).

If the corresponding packet is not included, the packet monitoring unit 1103 sends a Duplicate to the ACK generation unit 1105.
ted ACK generation is requested, and the ACK generation unit 1105 assumes that the last received packet is lost at that time, and in the case of multiple duplicated ACKs indicating that, for example, in the case of TCP, retransmission control and congestion control are performed. Generate 3 or more Duplicated ACKs to be executed, and transmit to the sender terminal 110 (
(S505 in FIG. 14). Thereafter, steps S501 to S505 in FIG. 14 are repeated. Also, step S50 in FIG.
If the order of the packet sequence numbers is maintained in step 2, steps S501 to S505 are repeated.

Next, the operation of the embodiment of the present invention is shown in the sequence diagram of FIG.
A specific description will be given based on an example in the case of P / IP. It is assumed that congestion control and retransmission control are set to occur when three duplicated ACKs with the same sequence number are received.

The network interface 1101 is a sequence number 1 transmitted from the transmission side terminal 110.
Is received (1501). The data received by the network interface 1101 is transferred to the communication protocol stack 602 (1502), and the packet monitoring unit 1103 snoops the packet received by 1501 and confirms the sequence number (1503). Communication protocol stack 1102
The data received in 1502 is passed to the receiving application 122 (1504).

The communication protocol stack 1102 notifies the transmitting side terminal of an ACK packet [ACK 1] indicating that data has been received via the network interface 1101 (1505, 1506). In the example shown in this sequence, it is assumed that the packet with sequence number 2 transmitted from the transmitting terminal 110 is lost for some reason during transmission (1507). The transmitting terminal 110 continues to transmit a packet with sequence number 3 (1508). The network interface 1101 receives the packet with the sequence number 3 and transmits it to the communication protocol stack 1102 (1509).
Communication protocol stack 1102 has not received the packet with sequence number 2.
A packet of [Dup ACK 1] is notified to the transmitting side terminal 110 in order to notify that the data of the sequence number 2 has not arrived at the same time (1511, 1512).

The packet monitoring unit 1103 receives the sequence number received by the network interface 1101.
Snoop 3 packet and check the sequence number (1510). Packet monitoring unit 110
3 detects the missing sequence number and stores the missing sequence number 2 at the same time.
The dummy packet generation unit 1104 is requested to generate a dummy packet (1513). The dummy packet generation unit 1104 generates a dummy packet corresponding to the packet with the sequence number 2 and transmits it to the communication protocol stack 1102 through the network interface 1101 (1514, 1515).
.

Since the communication protocol stack 1102 determines that the packet with the sequence number 2 has been received, the data with the sequence numbers 2 and 3 are transferred to the receiving-side application 122 (1516, 1517).
The communication protocol stack 1102 transmits [ACK 3] indicating that the data has been received to the transmitting side terminal (1518, 1519). Subsequently, the transmitting terminal transmits a packet with sequence number 4 (1520).
.

The communication protocol stack 1102 receives the data of sequence number 4 from the network interface 1101 and passes it to the receiving application 122 (1521, 1523).
[ACK 4], which is an acknowledgment response to the packet No. 4, is transmitted to the transmitting terminal 110 (1524, 1525). The packet monitoring unit 1103 snoops the packet of the network interface 1101 and confirms that the packet of the sequence number 2 has not arrived since the sequence number of the packet obtained through the network interface 1101 is 4 (1522).

The transmitting terminal transmits a packet with sequence number 5. The communication protocol stack 1102 behaves as usual (1527, 1529, 1531). The packet monitoring unit 1103 snoops the packet of the network interface 1101, confirms that the packet of the sequence number 2 has not arrived since the sequence number of the packet obtained through the network interface 1101 is 5, and continuously receives the packet 3 Since the packet of sequence number 2 is not included in the number of packets, it is determined that a packet loss has occurred (1528). The packet monitoring unit 1103
The ACK generation unit 1105 is requested to generate an ACK (1530). The ACK generation unit 1105 assumes that the packet having the sequence number 5 has been lost, and [ACK 5] indicating that is the number necessary for the congestion control to occur,
In this sequence, three that are often used in TCP implementation are generated and sent to the sending terminal.
(1533,1534,1535,1536,1537,1538). Since the transmitting terminal receives three or more Duplicated ACKs, it determines that a packet loss has occurred, performs congestion control, and continues data transmission.

Next, the further effect by this Embodiment is demonstrated. In the present embodiment, even if the sequence number of the packet sequence number is broken, the sequence number of the next consecutively received packet is confirmed and operated, so that even if the packet arrival order is out of order, congestion control and Implementation of retransmission control can be suppressed.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to the drawings.

FIG. 16 is a configuration diagram of a sixth embodiment of a receiving communication device according to the present invention. A receiving-side communication device (hereinafter referred to as communication device 1600) according to the present invention includes a network interface 1601, a communication protocol stack 1602, a packet monitoring unit 1603, a retransmission enable / disable determination unit 1604, a dummy packet generation unit 1605, and an ACK generation unit 1606. . These means operate as follows.

A network interface 1601 is connected to the network 130 shown in FIG. 1, and transmits and receives packets. The communication protocol stack 1602 manages packet transmission / reception. The packet monitoring unit 1603 monitors packets transmitted and received via the network interface 1601, and monitors the packet sequence number. When the sequence number of the packet sequence is broken, that is, the sequence number of the packets does not increase one by one, the sequence numbers are not consecutive, or packets with a larger sequence number arrive first In this case, the packet monitoring unit 1603 notifies the retransmission permission determination unit 1604. The resendability judgment unit 1604 has a flag for judging the necessity of resendability and a resendability judgment flag therein, and when a notification from the packet monitoring unit 1603 is received, the resendability judgment flag is set. If
The dummy packet generation unit 1605 is notified, and when the retransmission possibility determination flag is not set, the ACK generation unit 1606 is notified. The dummy packet generation unit 1605 receives the notification from the retransmission permission determination unit 1604, generates a dummy packet, and passes through the network interface 1601.
Transmit to the communication protocol stack 1102. The ACK generation unit 1606 receives a notification from the retransmission permission determination unit 1604, generates a plurality of Duplicated ACKs, and transmits them to the transmission side terminal via the network interface 1601.

Next, the overall operation of the present embodiment will be described in detail with reference to the configuration diagram of FIG. 16 and the flowchart of FIG.

The packet monitoring unit 1603 monitors the sequence numbers of packets transmitted and received via the network interface 1601 (S601 in FIG. 17).

When the order of the packet sequence numbers is broken, for example, when it is observed that the packet sequence numbers arrive without increasing one by one or the packet with the larger sequence number arrives first, the packet monitoring unit 1603 notifies the retransmission permission determination unit 1604 (FIG. 17).
S602). If the packets arrive in order, they are prepared for the arrival of the next packet.

Upon receiving the notification from the packet monitoring unit 1603, the retransmission permission determination unit 1604 checks its own retransmission permission determination flag, and if the retransmission permission determination flag is not set, the dummy packet generation unit
1605 and the ACK generation unit 1606 are notified, and when the retransmission possibility determination flag is set, only the dummy packet generation unit 1605 is notified (S603 in FIG. 17).

The ACK generation unit 1606, which has received the notification from the retransmission permission determination unit 1604, determines the number of duplicated ACKs necessary for determination of congestion control and retransmission control, and three or more duplicated ACKs for a general TCP.
A packet is generated, notified to the transmission side terminal 110 through the network interface 1601, and a retransmission permission determination flag is set (S604 in FIG. 17).

The dummy packet generation unit 1605 that has received the notification from the retransmission permission determination unit 1605 generates a dummy packet having a sequence number that should be originally received, and transmits the dummy packet to the communication protocol stack 1602 through the network interface 1601. Thereafter, S601 to S605 are repeated.

The validity period is set by the retransmission permission determination unit 1604 in the retransmission permission determination flag. The valid period is a numerical value calculated from parameters such as RTT (Round Trip Time: time required for packet transmission from the transmitting terminal to the receiving terminal) measured at the time of TCP / IP connection formation or in advance, for example, It is possible to employ a time that is three times the measured RTT. Further, the retransmission permission determination flag is determined by the retransmission permission determination unit 1604 by the dummy packet generation unit 1605 and the ACK generation unit 1606.
It is set at the time of notification, and when the valid period elapses, it is assumed that the retransmission permission determination flag is reset (in a state where it is not set).

Next, the operation of the embodiment of the present invention is shown in the sequence diagram of FIG.
A specific description will be given based on an example in the case of P / IP. It is assumed that congestion control and retransmission control are set to occur when three duplicated ACKs with the same sequence number are received.

The network interface 1601 receives the packet with the sequence number 1 transmitted from the transmission side terminal 110 shown in FIG. 1 (1801). The data received by the network interface 1601 is transferred to the communication protocol stack 1602 (1802), and the packet monitoring unit 1603 snoops the packet received by 1801 and confirms the sequence number (1803).

The communication protocol stack 1602 passes the data received in 1802 to the receiving application 122 shown in FIG. 1 (1804). The communication protocol stack 1602 indicates that an ACK packet indicating that data has been received, in this case, a packet having sequence number 1 [ACK 1
] To the transmitting side terminal 110 through the network interface 1601 (1805, 1806
).

In this sequence, it is assumed that the packet of sequence number 2 transmitted next from the transmission side terminal 110 is lost for some reason during transmission (1807). The transmitting terminal 110 continues to transmit a packet with sequence number 3 (1808). The communication protocol stack 1602 receives the data of sequence number 3 from the network interface 1601, but has not received the data of sequence number 2, so the packet that notifies that, that is, the data of sequence number 1 called Duplicated ACK [Dup ACK 1] indicating that it has only been received is transmitted to the transmitting terminal 110 (1809, 1811 and 1812).

The packet monitoring unit 1603 monitors the network interface 1601 and determines the sequence number
It detects that the second packet is lost (1810). The packet monitoring unit 1603 notifies the retransmission permission determination unit 1604 (1813). In this sequence, the retransmission possibility determination unit 1604 assumes that the retransmission possibility determination flag is not initially set. Since the retransmission possibility determination flag is not set, the ACK generation unit 1606 and the dummy packet generation unit 1605 Notify (1814,181
Five).

The ACK generation unit 1606 generates a plurality of duplicated ACKs, which are used in a general TCP implementation in this sequence, and transmits them to the transmitting terminal 110 (1816, 1817, 1818, 1819, 1820). , 1
821). Also, the dummy packet generation unit 1605 generates a dummy packet that replaces the packet of sequence number 2 that has not arrived, and notifies the communication protocol stack 1602 through the network interface 1601 (1822, 1823). Since the communication protocol stack 1602 has received the data of sequence number 2, it sends the data of sequence numbers 2 and 3 to the receiving-side application 122 (1824, 1825) and notifies that the data up to sequence number 3 has been received. Therefore, a packet of [Dup ACK 3] is generated and notified to the transmitting side terminal 110 (1826, 1827). Since the transmitting side terminal 110 has received three or more duplicated ACKs continuously, it performs congestion control and retransmission control, and continues data transmission (1828, 1829, 1830, 1831, 1832).

.

Here, it is assumed that the packet of sequence number 4 transmitted by the transmitting terminal is lost (1833).
The transmitting terminal 110 transmits the packet with the sequence number 5 (1834). The packet monitoring unit 1603 detects that the packet with the sequence number 4 is lost (1836), and notifies the retransmission possibility determination unit 1604 (1837). The retransmission permission determination unit 1604 confirms the retransmission permission determination flag, and since the retransmission permission determination flag is set, only the dummy packet generation unit 1605 is requested to generate a dummy packet (1838). The dummy packet generation unit 1605 generates a dummy packet in place of the unarrived sequence number 4 packet and notifies the communication protocol stack 1602 via the network interface 1601 (1839, 1840). The communication protocol stack 1602 receives the data of sequence numbers 4 and 5 (1841, 1842), generates a packet of [ACK 5] to notify that the data up to sequence number 5 has been received, Notify 110 (1843, 1844)
.

The further effect by this Embodiment is demonstrated. When packet loss occurs intermittently, if duplicated ACK is generated every time a packet is lost, congestion control will occur continuously, so the performance as TCP will be greatly degraded. In addition,
Originally, the time required for duplicated ACK to be sent multiple times, that is, RTT in general TCP
For packet loss that occurs intermittently in three times the time, by suppressing the transmission of Duplicated ACK, it is possible to keep the number of times of congestion control low and to prevent the deterioration of TCP performance. .

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described with reference to the drawings.

FIG. 19 is a configuration diagram of a seventh embodiment of a communication apparatus according to the present invention. A transmission side communication device 1900 related to the present invention includes a network interface 1901, a communication protocol stack 1902.
A packet monitoring unit 1903 and an ACK generating unit 1904. Unlike the first to sixth embodiments, these means function as a transmission side communication device on the data transmission side. The operation is as follows.

A network interface 1901 is connected to the network 130 shown in FIG. 1, and transmits and receives packets. The communication protocol stack 1902 is the transmission side application 11 shown in FIG.
2 manages the transmission of packets to the receiving side terminal 120 shown in FIG. The packet monitoring unit 1903 is connected to the network interface 19
Monitors packets sent and received via 01 and detects reception of Duplicated ACK. Duplic
Upon detecting the reception of the ated ACK, the packet monitoring unit 1903 sends the duplicated ACK to the ACK generating unit 1904.
Request generation of. The ACK generation unit 1904 has as many duplicated numbers as necessary for congestion control to occur.
ACK is generated and the communication protocol stack 190 is transmitted through the network interface 1901.
Send to 2.

Next, the overall operation of the present embodiment will be described in detail with reference to the flowchart of FIG.

The packet monitoring unit 1903 monitors the sequence numbers of packets transmitted and received via the network interface 1901 (S701). When the packet monitoring unit 1903 detects reception of the Duplicated ACK, the packet monitoring unit 1903 notifies the ACK generation unit 1904 (S702). The ACK generation unit 1904 performs congestion control and retransmission control by receiving a plurality of, for example, three or more Duplicated ACKs in general TCP / IP, and therefore subtracts the already received Duplicated ACKs. Duplicate of 2 or more
d Generate ACK, and through the network interface 1901, the communication protocol stack 1
It transmits to 902 (S703). Thereafter, S701 to S703 are repeated. In S702, Duplicated ACK
Is not detected, the packet monitoring unit 1903 prepares for the arrival of the next packet.

Next, the operation of the embodiment of the present invention is shown in the sequence diagram of FIG.
A specific description will be given based on an example in the case of P / IP. It is assumed that congestion control and retransmission control are set to occur when three or more duplicated ACKs with the same sequence number are received.

The communication protocol stack 1902 on the sending side is sent through the network interface 1901.
Data of sequence number 1 is transmitted to the receiving side terminal 120 (2101, 2102). The receiving terminal transmits an acknowledgment [ACK 1] indicating that the packet has been received (2103). Communication protocol stack 190
2 receives the confirmation notification of the receiving terminal 120 through the network interface 1901 (2
104). The packet monitoring unit 1903 monitors the received packet through the network interface 1901 and confirms reception of the confirmation response [ACK 1] indicating that the sequence number 1 has been received.
(2105).

Assume that the packet of sequence number 2 transmitted by the communication protocol stack 1902 is lost during network transmission (2106, 2107). The communication protocol stack 1902 subsequently transmits the packet with the sequence number 3 (2108, 2109). Since receiving-side terminal 120 has not received the packet with sequence number 2, duplicated ACK with sequence number 1 ([Dup ACK 1]) is sent as a confirmation notification.
) Is transmitted (2110). The communication protocol stack 1902 is the network interface 19
A confirmation notification [Dup ACK 1] is received through 01 (2111). The packet monitoring unit 1903 confirms reception of the confirmation notification [Dup ACK 1] through the network interface 1901. Since it is the same as the confirmation notification received in 2105, the packet monitoring unit 1903 suspects packet loss and notifies the ACK generation unit 1904. (2112, 2113) to instruct generation of ACK of sequence number 1.

Upon receiving the notification, the ACK generation unit 1904 receives a plurality of duplicated ACKs, two or more in this sequence (in general TCP / IP, congestion control and retransmission control can be performed by receiving three or more duplicated ACKs. Generated Duplicated ACK [ACK 1] indicating that only sequence number 1 has been received (2 or more subtracted already received Duplicated ACK), and sent to communication protocol stack 1902 through network interface 1901 (2114,2115
, 2116, 2117).

Since the communication protocol stack 1902 receives three or more Duplicated ACKs of sequence number 1, it performs congestion control and retransmits the packet of sequence number 2 at the same time. Receiving side terminal 120 transmits confirmation notification [ACK 3] indicating that data up to sequence number 3 has been received (2120, 2121).

The effect by this Embodiment is demonstrated. When receiving a duplicated ACK on the transmitting side, a plurality of duplicated ACKs necessary for implementing congestion control and retransmission control are generated, and congestion control and retransmission control are performed, so that loss can be achieved earlier than before. Since packets are retransmitted, for example, in the case of an application that reproduces video and audio, it is possible to reproduce video and audio without interruption.

Furthermore, in this embodiment, since the transmission of Duplicated ACK is promoted, congestion control of the communication protocol is not suppressed. Therefore, when data is sent and received with a communication protocol that involves retransmission control and congestion control in an application that requires real-time performance,
It is possible to reduce a delay until data associated with retransmission control is reproduced without impairing congestion control.

In the present embodiment, the packet monitoring unit directly monitors the network interface without going through the communication protocol stack, and a newly generated Duplicated ACK is also transmitted directly to the network interface. In other words, there is no need to modify the communication protocol. The communication protocol is often implemented as part of the computer's operation system (kernel), and in many cases it is difficult to make corrections. There is no need to put it in.

(Eighth embodiment)
Next, the best mode for carrying out the eighth invention of the present invention will be described with reference to the drawings.

FIG. 22 is a configuration diagram of an eighth embodiment of a communication apparatus according to the present invention. A communication device 2200 according to the present invention includes a network interface 2201, a communication protocol stack 2202, a packet monitoring unit 2203, a retransmission permission determination unit 2204, and an ACK generation unit 2205. Similar to the seventh embodiment,
These means function as a communication device on the data transmission side and operate as follows.

The network interface 2201 is connected to the network 130 and transmits and receives packets. The communication protocol stack 2202 is transmitted from the transmission side application 112 shown in FIG.
It manages transmission of packets to the receiving side terminal 120 shown in FIG. The packet monitoring unit 2203 monitors packets transmitted / received via the network interface 2201, and notifies the retransmission permission determination unit 2204 when detecting transmission of a Duplicated ACK.

The retransmission permission determination unit 2204 has a retransmission permission determination flag that is valid for a certain period of time, and checks whether the retransmission permission determination flag is set. If the retransmission permission determination flag is not set, the ACK generation unit 2205 is notified of a Duplicated ACK generation request. When the retransmission permission determination flag is not set, the retransmission permission determination unit 2204 does not perform any special processing for the packet,
Prepare for the arrival of the next packet. The number of ACK generators 2205 is as many as necessary for congestion control to occur.
Duplicated ACK is generated and transmitted to the notification protocol stack 2202 through the network interface 2201.

Regarding the validity period of the resendability determination flag, a numerical value calculated from parameters such as RTT measured in advance when a TCP / IP connection is formed, for example, a time three times the measured RTT,
The retransmission permission determination flag is set when the retransmission permission determination unit 2204 receives a notification from the packet monitoring unit 2203 and the retransmission permission determination flag is not set. As with the generation, it is assumed that the retransmission permission determination unit 2204 resets the retransmission permission determination flag (to a state where it is not set).

  Next, the overall operation of the present embodiment will be described in detail with reference to FIG. 22 and FIG.

The packet monitoring unit 2203 monitors the sequence number of packets transmitted / received via the network interface 2201 (S801). The packet monitoring unit 2203 determines whether the received packet is a Duplicated ACK (S802).
If it is notified to 2204 (S803) and not Duplicated ACK, it prepares for the arrival of the next packet (S804).
The resendability judgment unit 2204 checks whether the resendability judgment flag is set, and when the resendability judgment flag is not set, notifies the ACK generation unit 2205, and the resendability judgment flag is set Prepares for the arrival of the next packet (S805). The ACK generation unit 2205 performs congestion control and retransmission control by receiving a plurality of, for example, three or more Duplicated ACKs in general TCP / IP, and therefore subtracts the already received Duplicated ACKs. Two or more duplicated ACKs are generated and transmitted to the communication protocol stack 2202 through the network interface 2201 (S806). Thereafter, S801 to S806 are repeated.

Next, the operation of the present embodiment will be described based on the sequence diagram of FIG. The communication protocol stack 2202 on the transmission side transmits data of sequence number 1 to the reception side terminal through the network interface 2201 (2401, 2402). The receiving terminal 120 transmits an acknowledgment [ACK 1] indicating that the packet has been received (2403). The communication protocol stack 2202 receives the confirmation notification of the receiving terminal 120 through the network interface 2201 (2404).

The packet monitoring unit 2203 monitors the received packet through the network interface 2201, and confirms reception of the confirmation notification [ACK 1] (2405). Assume that the packet with sequence number 2 sent by the communication protocol stack 2202 is lost during network transmission (2406, 2407
). Communication protocol stack 2202 subsequently transmits a packet with sequence number 3 (2408, 2
409). Since receiving side terminal 120 has not received the packet of sequence number 2, [Dup ACK 1] is transmitted as a confirmation notification indicating that (2410).

The communication protocol stack 2202 receives the confirmation notification [Dup ACK 1] through the network interface 2201 (2411). The packet monitoring unit 2203 confirms the reception of the confirmation notification [ACK 1] through the network interface 2201, and since it is the same as the previously received confirmation notification (2405), the packet monitoring unit 2203 suspects the loss of the packet and determines whether or not to permit retransmission. Is notified (2413).

The retransmission permission / non-permission determination unit 2204 checks whether or not the retransmission permission / non-permission determination flag is set.
In this sequence, it is assumed that the retransmission permission determination flag is not set, and at this time, the retransmission permission determination section 2204 notifies the ACK generation section 2205 and sets the retransmission permission determination flag (2414).

Upon receiving the notification, the ACK generating unit 2205 receives a plurality of duplicated ACKs, two or more in this sequence (in general TCP / IP, congestion control and retransmission control are performed by receiving three or more duplicated ACKs. Generated Duplicated ACK [ACK 1] indicating that it has received only sequence number 1 of two or more (subtracted already received Duplicated ACK), and sends it to communication protocol stack 2202 through network interface 2201 (2415, 2416
, 2417,2418). Communication protocol stack 2202 received 3 or more duplicated ACKs,
Congestion control is performed, and at the same time, the packet of sequence number 2 is retransmitted (2419.2420).

Receiving terminal 120 confirms that it has received data of sequence numbers 2 and 3 [ACK 3]
Is notified (2421, 2422, 2423). Next, it is assumed that the packet of sequence number 4 transmitted by the communication protocol stack 2202 is lost during network transmission (2424, 2425).

Communication protocol stack 2202 continues to transmit the packet with sequence number 5 (2426
, 2427). Since the receiving terminal 120 has not received the packet with the sequence number 4, the confirmation notification [A
CK 3] is transmitted (2428). Communication protocol stack 2202 is network interface 2
Confirmation notification [ACK 3] is received through 201 (2429). The packet monitoring unit 2203 confirms that the confirmation notification [ACK 3] is duplicated from the received packet monitored through the network interface 2201 (2430), and notifies the retransmission possibility determination unit 2204 (2431).

Since retransmission permission / non-permission determination unit 2204 has a retransmission permission / non-permission determination flag set, ACK generation unit 2205
No instructions are issued for. During the period when the resendability flag is set,
The communication device 2200 repeats the same processing including the packet monitoring unit 2203 and the retransmission permission / non-permission determination unit 2204 (2432 to 2446).

As an effect of the present embodiment, in addition to the effect of the seventh embodiment, when packet loss occurs intermittently, if a plurality of duplicated ACKs are generated each time a packet loss occurs, congestion control is continued. As a result, the performance of TCP is greatly degraded.However, by suppressing the transmission of Duplicated ACK for packet loss that occurs intermittently within a certain time, as in this embodiment, It is possible to keep the number of times of congestion control low and prevent a large performance degradation of TCP.

Next, the operation of the best mode for carrying out the present invention will be described using specific examples.
First, an example using the communication apparatus according to the first embodiment will be described. FIG. 25 shows the first
The VoD (Video On Demand) client 2550 including the communication device according to the embodiment and the VoD server 2540 that provides the VoD service distributes video / audio data in real time.
It is an example of a system.

FIG. 26 shows a packet sequence of the VoD client 2550 and the VoD server 2540 shown in FIG. 25. In the VoD client 2550, the reception order of the playback data in the video playback application 2552 received by the communication device 2551 is shown. Has been.

Embodiment In the VoD system shown in FIG. 25, a VoD server 2540, a VoD client 2550 including a communication device 2551 and a video playback application 2552 according to the present invention, a VoD client 2550 and a VoD
A firewall 2560 exists on the network connecting the servers 2540.

It is assumed that the VoD client 2550 uses HTTP (Hyper Text Transfer Protocol) to reproduce video by the received packet in order to receive video / audio from the VoD server 2540 through the firewall 2560.

Embodiment Referring to FIG. 26, when the VoD client 2550 makes a data request for video / audio to the VoD server 2540, the VoD server 2540 transmits data of sequence number 1 (2601).

When the communication device 2551 receives the data of sequence number 1, it returns ACK (2602) and at the same time, passes the data of sequence number 1 to the video playback application 2552 (2603). Next, it is assumed that the data of sequence number 2 sent by the VoD server 2540 is lost due to network congestion.
(2604). At this time, since the VoD client 2550 does not receive data, no response is made. Subsequently, the VoD server 2540 transmits data of sequence number 3 (2605). The communication device 2551 receives the data of sequence number 3, and returns [Dup ACK 1] as a Duplicated ACK (2606).
At the same time, the snooped data is passed to the video playback application 2552 (2607). The received data of sequence number 3 is used as reproduction data.

Similar processing occurs for sequence number 4 and sequence number 5 (2608 to 2613).
Thereafter, the VoD server 2540 retransmits the packet with the sequence number 2 in order to receive the Duplicated ACK three times (2614). When the communication device 2551 receives the retransmitted packet, it returns 5 which is the maximum sequence number received at that time as an ACK (2615), and at the same time, discards the received data stored in the protocol stack. Subsequently, the VoD server 2540 transmits data of the next sequence number 6 (2616) and continues the VoD service. Since the operation in the communication device 2551 is the same as that of the first embodiment, the description is omitted. In addition, regarding the second to sixth embodiments, the VoD client 500 performs the same operation as that of the present embodiment, and thus description thereof is omitted.

Next, an example using the communication apparatus shown in the first embodiment and the communication apparatus of the seventh embodiment will be described. FIG. 27 shows a relay device 2730 having the function of the communication device of the first embodiment as a function at the time of packet reception, and also having the function of the communication device of the seventh embodiment as a function at the time of packet transmission, Video chat client for HTTP video chat
Consists of 2710 and 2720. Relay device 2730 is used for video chat clients 2710 and 2720
It is assumed that the relay device 2730 has a function of receiving data transmitted from the video chat clients 2710 and 2720 and transferring the data to other video chat clients.

FIG. 28 shows a video chat client 2710 as a transmission side and 2720 as a reception side.
The sequence in the case of exchanging data packets via the relay device 2730 having 30 is shown. In an actual video chat application, the roles of the transmission side and the reception side of the video chat clients 2710 and 2720 are arbitrarily switched, and data is exchanged between them.

The relay device 2730 terminates the data transmitted from the video chat client 2710 on the transmission side, and transmits the data to the video chat client 2720 on the reception side. In order to clarify this, a packet of sequence number m transmitted from the transmission side and terminated at relay apparatus 2730 is denoted by #m, and a packet of sequence number n transmitted from relay apparatus 2730 is denoted by $ n.

First, with reference to the upper half of FIG. 28, a packet relay (transfer) operation performed by the relay device 2730 using the function shown in the seventh embodiment will be described. The video chat client 2710 sends data to the video chat client 2720 through the relay device 2730. Relay device 27
30 receives the packet of sequence number # 1 transmitted from the video chat client 2710 (2801), but the TCP connection is terminated here, and the relay device 2730 is an acknowledgment to the video chat client 2710 [ ACK # 1] is transmitted (2802). At the same time, the relay device 2730 transmits the packet with the sequence number $ 1 received at 2801 to the video chat client 2720 (2803). The video chat client 2720 transmits an acknowledgment [ACK $ 1] indicating that the packet has been received (2804). Subsequently, the relay device 2730 receives the packet with the sequence number # 2 transmitted from the video chat client 2710 (2805), and receives an acknowledgment [ACK
# 2] is transmitted (2806). Assume that a packet is lost when the packet with the sequence number $ 2 is transferred to the video chat client 2720 (2807).

Further, the relay apparatus 2730 continuously transmits data of sequence number 3 from the video chat client 2710 (2808, 2809). The relay apparatus 2730 transfers the received packet to the video chat client 2720 (2810), and receives [Dup ACK $ 1] as an acknowledgment from the video chat client 2720 (2811). At this time, since relay apparatus 2730 overlaps with the acknowledgment [ACK $ 1] received in 2804, it is determined that a packet loss has occurred, and the embodiment
Duplicated ACK that only generates retransmission control and congestion control as described in 7.
Is generated and received (2812, 2813) and the data of sequence number $ 2 is retransmitted (2814, 2815)
).

At this time, congestion control is also performed simultaneously with retransmission control. Subsequently, the communication device 2731 receives the data of the sequence number # 4 from the video chat client 2710 (2816), and transfers the data to the video chat client 2720 (2818), thereby continuing the video chat service.

Next, with reference to the lower half of FIG. 28, a packet relay (transfer) operation performed by the relay device 2730 using the function described in the first embodiment will be described. The video chat client 2710 transmits data of sequence number # 5 to the communication device 2731 (2820). Since relay device 2730 has received the data of sequence number # 5, it sends acknowledgment [ACK # 5] to video chat client 27.
10 is transmitted (2821). The relay apparatus 2730 transmits the packet received at 2820 to the video chat client 2720 as a packet with the sequence number $ 1 (2822), and the video chat client 2720 transmits an acknowledgment [ACK $ 5] indicating reception of the packet (2823). ).

Next, it is assumed that the data of sequence number # 6 transmitted by the video chat client 2710 is lost due to a network failure or the like (2824). Subsequently, the video chat client 2720 transmits data of sequence number # 7 (2825). Since relay device 2730 has not received the data of sequence number # 6, confirmation response [Dup ACK #
5] (2826) and at the same time, the snooped data of sequence number # 3 is received by the method described in the first embodiment, and the data is transmitted as sequence number $ 6 to video chat client 2720 (2827). ).

[ACK $ 6], which is an acknowledgment, is transmitted from the video chat client 2720 (2828).
After that, the video chat client 2710 transmits the data of sequence numbers # 8 and # 9 (282
9,2833) and [Dup ACK # 5] is received from the relay device 2730 (2830, 2834). Relay device 2730
Data snooped by the method described in the first embodiment is transmitted to the video chat client 2720 as data of sequence numbers $ 7 and $ 8 (2831, 2835). Since the video chat client 2710 receives the confirmation response [Dup ACK # 5] three times (2826, 2830, 2834), it performs congestion control and retransmission control (2837, 2838).

In the present embodiment, even when the embodiment of the present invention is not included in the data transmission side or the reception side, by introducing the embodiment of the present invention to the device that relays data, the data reception up to the data reception accompanying the retransmission control can be performed. It becomes possible to reduce delay and implement congestion control.

The present invention can be applied to a service that performs video / audio communication in real time, such as a conference service, even in an environment where only HTTP can be used because of a firewall or a proxy.

It is a connection block diagram of the terminal in the 1st to 8th embodiment. It is a block diagram of 1st Embodiment. It is a flowchart of a 1st embodiment. It is a sequence diagram of a 1st embodiment. It is a block diagram of 2nd Embodiment. It is a flowchart of a 2nd embodiment. It is a sequence diagram of a 2nd embodiment. It is a block diagram of 3rd Embodiment. It is a flowchart of a 3rd embodiment. It is a sequence diagram of a third embodiment. It is a block diagram of 4th, 5th embodiment. It is a flowchart of a 4th embodiment. It is a sequence diagram of a fourth embodiment. It is a flowchart of a 5th embodiment. It is a sequence diagram of a 5th embodiment. It is a block diagram of 6th Embodiment. It is a flowchart of a 6th embodiment. It is a sequence diagram of a sixth embodiment. It is a block diagram of 7th Embodiment. It is a flowchart of a 7th embodiment. It is a sequence diagram of a seventh embodiment. It is a block diagram of 8th Embodiment. It is a flowchart of 8th Embodiment. It is a sequence diagram of an eighth embodiment. It is a whole connection block diagram of a 1st Example. It is a sequence diagram of a 1st Example. It is a whole connection block diagram of a 2nd Example. It is a sequence diagram of the 2nd example. It is a block diagram which shows the implementation example of the communication protocol in 1st-8th embodiment. It is a block diagram which shows the example of mounting of the snoop packet output part in 1st Embodiment, and the packet monitoring part in 2nd-8th Embodiment. It is a sequence diagram in a conventional example.

Explanation of symbols

110: Sending terminal
111, 1900, 2200: Transmission side communication device
112: Sender application
120: Receiver terminal
121, 500, 800, 1100, 1600: Receiving side communication device
122: Receiver application
130: Network
201, 501, 801, 1101, 1601, 1901, 2201: Network interface
202: Data receiver
203, 502, 802, 1102, 1602, 1902, 2202: Communication protocol stack
204: Snoop packet output part
503, 803, 1103, 1603, 1903, 2203: Packet monitoring unit
504, 1104, 1605: Dummy packet generator
804, 1105, 1606, 1904, 2205: ACK generator
1604, 2204: Playability judgment unit

Claims (18)

A communication device connected to the receiving application and the network,
Controls packet transmission / reception through the network interface, and transmits the received packet data to the application, and monitors the packet transmitted / received through the network interface, thereby causing congestion control in the communication protocol. A packet monitoring unit that detects the timing to detect, and notifies the dummy packet generation unit of the detection of the timing;
Receiving a notification of the detection, generating a dummy packet, and transmitting the dummy packet generation unit to the communication protocol stack through the network interface;
A packet communication device having at least A communication device connected to the receiving application and the network,
A communication protocol stack that manages transmission and reception of packets through a network interface and transmits received packet data to an application;
A packet monitoring unit that monitors the packet transmitted and received via the network interface to detect transmission of Duplicated ACK, and notifies the detection to the ACK generation unit and the dummy packet generation unit;
Receiving the notification of detection, generating the one or more Duplicated ACKs necessary for performing retransmission control and congestion control, and transmitting to the network interface, the ACK generation unit,
Receiving the notification of detection, generating a dummy packet, and transmitting the dummy packet generation unit to the communication protocol stack through the network interface;
A packet communication device having at least A communication device connected to the receiving application and the network,
A communication protocol stack that manages transmission and reception of packets through a network interface and transmits received packet data to an application;
Monitors whether the order of the sequence numbers of the packets transmitted / received via the network interface is maintained, and detects that the order is not maintained, notifies the detection to the dummy packet generation unit, Further, a packet monitoring unit that monitors whether or not a non-arrival packet is included in the plurality of packets that arrive continuously in succession, and when it is detected that the packet is not included, a packet monitoring unit that notifies the ACK generation unit of the detection,
Receiving the notification of detection that the unarrived packet is not included, generating one or more duplicated ACKs necessary for performing congestion control, and transmitting the generated ACK to the network interface;
Receiving the notification that the order is not maintained, generating a dummy packet and transmitting the dummy packet generation unit to the communication protocol stack;
A packet communication device having at least A communication device connected to the receiving application and the network,
A communication protocol stack for managing packet transmission and reception through a network interface and transmitting received data to an application;
The communication protocol stack for transmitting the network interface to the application and the sequence number of the packet transmitted / received via the network interface are monitored to detect if the sequence number is not maintained. A packet monitoring unit for notifying the retransmission permission determination unit,
A resendability judgment flag that is valid for a certain period, and when the resendability judgment flag is not set, the resendability judgment flag is set, and a dummy packet generation unit and an ACK generation unit are notified, and the resendability judgment is performed. When the flag is set, a retransmission permission determination unit that notifies the dummy packet generation unit,
When receiving a notification from the retransmission permission determination unit, generates a dummy packet, and transmits the dummy packet generation unit to a network interface;
Upon receipt of the notification from the retransmission permission determination unit, the ACK generation unit generates one or more duplicated ACKs necessary for executing congestion control, and transmits to the network interface;
A packet communication device having at least The packet communication apparatus according to claim 1, wherein the communication protocol is TCP / IP. The packet communication device according to claim 1, wherein the communication protocol is TCP / IP, and the timing at which congestion control in the communication protocol occurs is detected by detecting Duplicated ACK in the TCP / IP. A packet relay device that relays packet transmission and reception between a packet transmission terminal and a reception terminal,
A first packet communication device for receiving a packet from a transmission side terminal;
A second packet communication device for transmitting the received packet to a receiving terminal,
5. The packet relay device according to claim 1, wherein the first packet communication device is the packet communication device according to claim 1. When there is a lost packet transmitted from the transmitting terminal and received by the relay device, a packet sequence number is assigned to the subsequent packet of the lost packet from the second packet communication device to the receiving terminal. The packet relay apparatus according to claim 7, wherein the packet is transmitted with the sequence number changed so as to maintain the order. A communication method for managing transmission / reception of packets through a network interface and connecting a receiving-side application and a network using a communication protocol for transmitting received packet data to the application, wherein the communication device passes through the network interface And monitoring the packet transmitted and received, detecting the timing at which congestion control occurs in a communication protocol, and notifying the dummy packet generator of the detection of the timing;
Generating a dummy packet in response to the notification of detection, and a dummy packet generating procedure for transmitting to the communication protocol stack through the network interface;
A packet communication method including at least. A communication method for managing transmission / reception of packets through a network interface and connecting a receiving-side application and a network using a communication protocol for transmitting received packet data to the application, wherein the communication device passes through the network interface A packet monitoring procedure for detecting the transmission of Duplicated ACK by monitoring the packet transmitted and received, and notifying the detection to the ACK generation unit and the dummy packet generation unit;
Receiving the notification of detection, generating the one or more duplicated ACKs necessary for performing retransmission control and congestion control, and transmitting the ACK generation procedure to the network interface;
Receiving the notification of the detection, generating a dummy packet, and transmitting the dummy packet through the network interface to the communication protocol stack;
A packet communication method including at least. A communication method for managing transmission / reception of packets through a network interface and connecting a receiving-side application and a network using a communication protocol for transmitting received packet data to the application, wherein the communication device passes through the network interface The sequence number of the packets transmitted and received is monitored whether or not the order is maintained, and if the order is not maintained, the detection is notified to the dummy packet generator, and the next consecutive A packet monitoring procedure for monitoring whether or not a non-arrival packet is included in the plurality of packets arriving in a packet, and notifying that detection is not included,
The ACK generation procedure of generating one or more Duplicated ACKs necessary for performing congestion control upon receiving notification of detection that the unarrived packet is not included, and transmitting to the network interface;
Receiving the notification that the order is not maintained, generating a dummy packet and transmitting the dummy packet to the communication protocol stack;
A packet communication method including at least. A communication method for managing transmission / reception of a packet through a network interface and connecting a receiving-side application and a network using a communication protocol for transmitting received packet data to the application, wherein the communication device connects the network interface to the application Monitoring whether the order of the sequence number of the packet transmitted and received by the network interface is maintained, and detecting that the order is not maintained, the detection is allowed to be retransmitted. Packet monitoring procedure to notify
A resendability judgment flag that is valid for a certain period, and when the resendability judgment flag is not set, the resendability judgment flag is set, and a dummy packet generation unit and an ACK generation unit are notified, and the resendability judgment is performed. When the flag is set, a retransmission permission determination procedure for notifying the dummy packet generator,
When receiving a notification from the retransmission permission determination unit, generates a dummy packet, and transmits the dummy packet to the network interface.
Upon receiving a notification from the retransmission permission determination unit, the ACK generation procedure for generating one or more duplicated ACKs necessary for executing congestion control and transmitting to the network interface;
A packet communication method including at least. The packet communication method according to claim 9, wherein the communication protocol is TCP / IP. The packet communication method according to claim 9, wherein the communication protocol is TCP / IP, and the timing at which congestion control in the communication protocol occurs is detected by detecting Duplicated ACK in the TCP / IP. A relay device that relays packet transmission / reception between a packet transmission terminal and a reception terminal receives a packet from the transmission terminal by the first packet communication method and receives the received packet by the second packet communication method. A packet relay method for transmitting to a terminal,
The packet relay method according to claim 9, wherein the first packet communication method is the packet communication method according to claim 9. When there is a lost packet while being transmitted from the transmitting terminal and received by the relay device, a packet sequence is transmitted from the second packet communication method to the receiving terminal following the lost packet. The packet relay apparatus according to claim 15, wherein the packet is transmitted with a sequence number added so that the order of the numbers is maintained. A program for causing a computer constituting a packet communication apparatus to execute the packet communication method according to any one of claims 9 to 12. A program for causing a computer constituting a packet relay apparatus to execute the packet relay method according to claim 15 or 16.

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