JP2016103698A - Device and method for packet transmission - Google Patents

Abstract

A packet transmission device and a packet transmission method capable of promptly retransmitting a packet are provided. A packet transmission apparatus according to an embodiment includes a transmission queue, a retransmission queue, a transmission unit, and a transmission switching unit. The transmission queue holds only initial transmission packets waiting to be transmitted among initial transmission packets that are packets transmitted for the first time to the destination packet receiving device. The retransmission queue holds only the retransmission packets waiting to be transmitted among the retransmission packets that are retransmitted to the destination packet receiving device. The transmission unit transmits the input initial transmission packet and the input retransmission packet. The transmission switching unit switches whether to input the initial transmission packet of the transmission queue or the retransmission packet of the retransmission queue to the transmission unit. When there is a retransmission packet held in the retransmission queue, the transmission switching unit inputs the retransmission packet in the retransmission queue to the transmission unit. [Selection] Figure 1

Description

  Embodiments described herein relate generally to a packet transmission device and a packet transmission method.

  In packet communication using TCP (Transmission Control Protocol) and IP (Internet Protocol), packets are retransmitted according to a TCP procedure. The packet transmission device inputs a packet to be retransmitted to a queue of packets to be transmitted, and transmits the packets in the order of input to the queue. Therefore, the retransmitted packet is transmitted after all the packets already accumulated in the queue are transmitted. For this reason, packet retransmission may not be executed promptly.

International Publication No. 2002/051101 JP 2005-051299 A JP 2004-048408 A

  The problem to be solved by the present invention is to provide a packet transmission apparatus and a packet transmission method capable of quickly retransmitting a packet.

  The packet transmission apparatus according to the embodiment includes a transmission queue, a retransmission queue, a transmission unit, and a transmission switching unit. The transmission queue holds only the initial transmission packets waiting to be transmitted among the initial transmission packets that are packets transmitted for the first time to the destination packet receiving device. The retransmission queue holds only the retransmission packets waiting to be transmitted among the retransmission packets that are retransmitted to the destination packet receiving apparatus. The transmission unit transmits the input initial transmission packet and the input retransmission packet. The transmission switching unit switches whether to input the initial transmission packet held in the transmission queue or the retransmission packet held in the retransmission queue to the transmission unit. When there is a retransmission packet held in the retransmission queue, the transmission switching unit inputs the retransmission packet held in the retransmission queue to the transmission unit.

The lineblock diagram showing the packet communications system of a 1st embodiment. 1 is a configuration diagram illustrating a packet transmission device 1 according to a first embodiment. FIG. The flowchart which shows the switching procedure of 1st Embodiment. The block diagram which shows the packet transmitter 1 of 2nd Embodiment. The block diagram which shows the packet communication system of 3rd Embodiment. The block diagram which shows the delivery server apparatus 201 of 3rd Embodiment. The sequence chart which shows the example of transmission of the retransmission packet of 3rd Embodiment.

  Hereinafter, a packet transmission device and a packet transmission method of an embodiment will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram illustrating a packet communication system according to the first embodiment. In FIG. 1, a packet transmission device 1 is connected to a packet switching network 3 through a communication line 4. The communication line 4 may be a wireless communication line or a wired communication line. The packet receiving device 2 is connected to the packet switching network 3 through a communication line 5. The communication line 5 may be a wireless communication line or a wired communication line. The packet transmitter 1 outputs a transmission packet whose destination is the packet receiver 2 to the communication line 4. The transmission packet output to the communication line 4 is input to the packet switching network 3. The packet switching network 3 outputs the transmission packet input from the communication line 4 to the communication line 5 to which the destination packet receiving device 2 is connected. The packet receiving device 2 receives a packet addressed to itself input from the communication line 5. As a result, a transmission packet addressed to the packet reception device 2 from the packet transmission device 1 is received by the packet reception device 2.

  FIG. 2 is a configuration diagram illustrating the packet transmission device 1 according to the first embodiment. In FIG. 2, the packet transmission device 1 includes a transmission queue 11, a retransmission queue 12, a transmission switching unit 13, and a transmission unit 14.

  An initial transmission packet is input to the transmission queue 11. The initial transmission packet is a packet transmitted to the destination packet receiving apparatus 2 for the first time. The transmission queue 11 holds only initial transmission packets waiting for transmission. The transmission queue 11 forms a first-in first-out queue with only the first transmission packets held by itself. The transmission queue 11 holds the input initial transmission packet and adds the initial transmission packet to the end of the queue.

  A retransmission packet is input to the retransmission queue 12. The retransmission packet is a packet that is retransmitted to the destination packet reception device 2. The retransmission queue 12 holds only retransmission packets waiting for transmission. The retransmission queue 12 creates a first-in first-out queue only with the retransmission packets held by itself. The retransmission queue 12 holds the input retransmission packet and adds the retransmission packet to the end of the queue.

  The transmission switching unit 13 takes out the initial transmission packet held in the transmission queue 11 from the transmission queue 11 and inputs it to the transmission unit 14. The transmission switching unit 13 takes out the retransmission packet held in the retransmission queue 12 from the retransmission queue 12 and inputs it to the transmission unit 14. The transmission unit 14 outputs the initial transmission packet and the retransmission packet input from the transmission switching unit 13 to the communication line 4. The initial transmission packet and the retransmission packet output to the communication line 4 are transmission packets addressed from the packet transmission device 1 to the packet reception device 2.

  The transmission switching unit 13 switches whether the initial transmission packet held in the transmission queue 11 or the retransmission packet held in the retransmission queue 12 is input to the transmission unit 14. When there is a retransmission packet held in the retransmission queue 12, the transmission switching unit 13 inputs the retransmission packet held in the retransmission queue 12 to the transmission unit 14. FIG. 3 shows the switching procedure. Hereinafter, the switching operation of the transmission switching unit 13 will be described with reference to FIG. When the packet transmission operation of the packet transmission device 1 is started, the switching procedure of FIG. 3 is started.

(Step S <b> 1) The transmission switching unit 13 confirms the packet holding state of the retransmission queue 12.

(Step S <b> 2) When there is a retransmission packet held in the retransmission queue 12, the transmission switching unit 13 proceeds to step S <b> 3. On the other hand, if there is no retransmission packet held in the retransmission queue 12, the transmission switching unit 13 proceeds to step S4.

(Step S <b> 3) The transmission switching unit 13 takes out the retransmission packet held in the retransmission queue 12 from the retransmission queue 12 and inputs it to the transmission unit 14. Thereafter, the transmission switching unit 13 returns the process to step S1.

(Step S <b> 4) The transmission switching unit 13 takes out the initial transmission packet held in the transmission queue 11 from the transmission queue 11 and inputs it to the transmission unit 14.

(Step S5) When the packet transmission operation of the packet transmission device 1 is completed, the transmission switching unit 13 ends the switching procedure of FIG. On the other hand, when the packet transmission operation of the packet transmission device 1 continues, the transmission switching unit 13 returns the process to step S1.

  According to the first embodiment, among the initial transmission packets that are packets transmitted for the first time to the destination packet receiving device 2, the transmission queue 11 that holds only the initial transmission packets waiting to be transmitted, and the destination packet receiving device 2 Among the retransmission packets that are retransmitted at the same time, the retransmission queue 12 that holds only the retransmission packets waiting to be transmitted, the transmission unit 14 that transmits the input initial transmission packet and the input retransmission packet, and the transmission unit 14 A transmission switching unit 13 for switching whether to input an initial transmission packet held in the transmission queue 11 or to input a retransmission packet held in the retransmission queue 12, and the transmission switching unit 13 When there is a retransmission packet held in 12, the retransmission packet held in the retransmission queue 12 is input to the transmission unit. Thereby, even if the initial transmission packet is held in the transmission queue 11, the retransmission packet held in the retransmission queue 12 can be transmitted faster than the initial transmission packet held in the transmission queue 11.

  According to the first embodiment, a queue is created by the retransmission queue 12 only with retransmission packets waiting for transmission. As a result, the transmission order can be determined only by the retransmission packets waiting for transmission.

(Second Embodiment)
The packet communication system of the second embodiment is the same as that of the first embodiment shown in FIG. FIG. 4 is a configuration diagram illustrating the packet transmission device 1 according to the second embodiment. In FIG. 4, parts corresponding to those in FIG. The packet transmission device 1 illustrated in FIG. 4 further includes a transmission buffer 21 and a queue input switching unit 22 in addition to the packet transmission device 1 of the first embodiment illustrated in FIG.

  The transmission buffer 21 holds a packet transmitted from the transmission unit 14. An initial transmission packet and a retransmission packet are input to the transmission buffer 21.

  The queue input switching unit 22 inputs an initial transmission packet from the packets held in the transmission buffer 21 to the transmission queue 11. The queue input switching unit 22 inputs an initial transmission packet held in the transmission buffer 21 to the transmission queue 11 when the transmission queue 11 is empty. The transmission queue 11 holds the initial transmission packet input from the queue input switching unit 22 and adds the initial transmission packet to the end of the queue.

  The queue input switching unit 22 inputs retransmission packets from the packets held in the transmission buffer 21 to the retransmission queue 12. The queue input switching unit 22 inputs a retransmission packet held in the transmission buffer 21 to the retransmission queue 12 when the retransmission queue 12 is free. The retransmission queue 12 holds the retransmission packet input from the queue input switching unit 22 and adds the retransmission packet to the end of the queue.

  Each operation of the transmission switching unit 13 and the transmission unit 14 is the same as that of the first embodiment.

  According to the second embodiment, in addition to the first embodiment, a transmission buffer 21 that holds packets transmitted from the transmission unit 14 and an initial transmission packet from among the packets held in the transmission buffer 21 Is input to the transmission queue 11, and the queue input switching unit 22 is configured to input a retransmission packet from the packets held in the transmission buffer 21 to the retransmission queue 12. Thereby, the initial transmission packet and the retransmission packet transmitted from the transmission unit 14 can be held in the same transmission buffer 21. The initial transmission packet held in the transmission buffer 21 can be held in the transmission queue 11 by being input to the transmission queue 11 by the queue input switching unit 22. The retransmission packet held in the transmission buffer 21 can be held in the retransmission queue 12 by being input to the retransmission queue 12 by the queue input switching unit 22.

(Third embodiment)
FIG. 5 is a configuration diagram illustrating a packet communication system according to the third embodiment. In FIG. 5, the distribution server device 201 is connected to the IP network 203 via the communication line 4. The communication line 4 may be a wireless communication line or a wired communication line. , N are connected to the IP network 203 by communication lines 5-1, 2,. An example of the IP network 203 is the Internet. The communication lines 5-1, 2,..., N may be wireless communication lines or may be wired communication lines. The distribution server device 201 is an example of a packet transmission device. The IP network 203 is an example of a packet switching network. The client devices 202-1, 2,..., N are examples of packet receiving devices.

  In the third embodiment, the packet refers to a TCP / IP packet. Here, with reference to FIG. 5, the client device 202-1 will be described as an example among the client devices 202-1, 2,..., N shown in FIG. The same applies to..., N. The distribution server device 201 outputs a transmission packet whose destination address is the IP address of the client device 202-1 to the communication line 4. The transmission packet output to the communication line 4 is input to the IP network 203. The IP network 203 outputs the transmission packet input from the communication line 4 to the communication line 5-1 to which the client device 202-1 having the destination address is connected. The client device 202-1 receives a packet having its own IP address as a destination address input from the communication line 5-1. Thereby, the transmission packet addressed to the client device 202-1 from the distribution server device 201 is received by the client device 202-1.

  The client device 202-1 outputs an acknowledgment packet whose destination address is the distribution server device 201 to the communication line 5-1, according to the TCP procedure. The confirmation response packet is an example of information for identifying a transmission packet received by the packet receiving device from transmission packets addressed to the packet receiving device from the packet transmitting device. The confirmation response packet output to the communication line 5-1 is input to the IP network 203. The IP network 203 outputs the acknowledgment packet input from the communication line 5-1 to the communication line 4 to which the destination address distribution server apparatus 201 is connected. The distribution server device 201 receives a packet having its own IP address input from the communication line 4 as a destination address. As a result, the acknowledgment packet addressed to the distribution server device 201 from the client device 202-1 is received by the distribution server device 201.

  FIG. 6 is a configuration diagram illustrating a distribution server device 201 according to the third embodiment. In FIG. 6, parts corresponding to those in FIGS. 2 and 4 are denoted by the same reference numerals. The distribution server device 201 illustrated in FIG. 6 further includes a content storage unit 211, an application unit 212, a reception unit 221, and a reception buffer 222 in addition to the packet transmission device 1 according to the second embodiment illustrated in FIG. Prepare. The application unit 212 is an example of a retransmission packet determination unit.

  The content storage unit 211 stores content data distributed from the distribution server device 201 to the client devices 202-1, 2, ..., n. The application unit 212 packetizes content data stored in the content storage unit 211 and outputs the packetized data to the transmission buffer 21. The transmission buffer 21 holds a packet input from the application unit 212. When the application unit 212 establishes a plurality of sessions, the transmission buffer 21 holds a packet for each session. The transmission buffer 21 deletes the packet held by itself in accordance with the instruction from the application unit 212.

  The operations of the transmission queue 11, the retransmission queue 12, and the queue input switching unit 22 are the same as those in the second embodiment. However, the retransmission packet held in the retransmission queue 12 among the packets held in the transmission buffer 21 is a packet notified from the application unit 212 to the queue input switching unit 22.

  Each operation of the transmission switching unit 13 and the transmission unit 14 is the same as that of the first embodiment.

  The receiving unit 221 receives from the communication line 4 a packet having the IP address of the own distribution server device 201 as a destination address. The reception unit 221 outputs the reception packet received from the communication line 4 to the reception buffer 222. The reception buffer 222 holds the reception packet input from the reception unit 221. When the application unit 212 establishes a plurality of sessions, the reception buffer 222 holds a received packet for each session.

  The application unit 212 extracts the received packet from the reception buffer 222. Based on the acknowledgment packet in the received packet taken out from the reception buffer 222, the application unit 212 determines a retransmission packet from the packets held in the transmission buffer 21 according to the TCP procedure. In TCP, as a procedure for retransmitting a packet, there are retransmission control by retransmission timeout and high-speed retransmission. The application unit 212 notifies the determined retransmission packet to the queue input switching unit 22. The queue input switching unit 22 inputs the retransmission packet notified from the application unit 212 among the packets held in the transmission buffer 21 to the retransmission queue 12.

  The application unit 212 determines a packet to be deleted from the transmission buffer 21 from the packets held in the transmission buffer 21 based on the confirmation response packet in the reception packet extracted from the reception buffer 222. The application unit 212 notifies the transmission buffer 21 of the determined packet to be deleted. The transmission buffer 21 deletes the packet to be deleted notified from the application unit 212 from the packets held by itself.

  FIG. 7 is a sequence chart illustrating an example of retransmission packet transmission according to the third embodiment. The transmission example in FIG. 7 is an example in which a packet is retransmitted by high-speed retransmission. In high-speed retransmission, when the packet transmission side receives the same acknowledgment (ACK) packet three times, the packet is retransmitted. Here, with reference to FIG. 7, the client device 202-1 will be described as an example among the client devices 202-1, 2,..., N shown in FIG.

  In FIG. 7, the distribution server device 201 packetizes data by 1000 octets and transmits the packet to the client device 202-1. First transmission packet having data from 1st octet to 1000th octet, then first transmission packet having data from 1001st octet to 2000th octet, then first transmission packet having data from 1st octet to 3000th octet Are sequentially transmitted from the distribution server device 201 to the client device 202-1.

  When the client device 202-1 receives an initial transmission packet having data from the 1st octet to the 1000th octet, the client device 202-1 transmits an ACK packet with an acknowledgment number of 1001 to the distribution server device 201. The distribution server apparatus 201 recognizes that the client apparatus 202-1 has received the data from the 1st octet to the 1000th octet by receiving the ACK packet whose confirmation response number is 1001.

  The distribution server apparatus 201 further transmits an initial transmission packet having data from the 3001st octet to the 4000th octet, then an initial transmission packet having data from the 4001st octet to the 5000th octet, and then from the 5001st octet to the 6000th octet The initial transmission packet having the following data, and then the initial transmission packet having the data from the 6001st octet to the 7000th octet are sequentially transmitted to the client apparatus 202-1.

  On the other hand, the initial transmission packet having data from the 1001st octet to the 2000th octet is not received by the client apparatus 202-1 because it is lost while being transmitted from the distribution server apparatus 201 to the client apparatus 202-1. For this reason, every time a new initial transmission packet is received, the client apparatus 202-1 repeatedly transmits the same ACK packet having an acknowledgment number of 1001.

  The distribution server device 201 transmits the same initial ACK packet with the confirmation response number 1001 from the client device 202-1 when the initial transmission packet having data from the 6001st octet to the 7000th octet is transmitted to the client device 202-1. Was received three times. Thereby, the distribution server apparatus 201 recognizes that the client apparatus 202-1 has not received data from the 1001st octet to the 2000th octet.

  Next, the distribution server device 201 executes a high-speed retransmission procedure for transmitting a retransmission packet having data from the 1001st octet to the 2000th octet to the client device 202-1. Through this high-speed retransmission procedure, the application unit 212 notifies the queue input switching unit 22 that packets having data from the 1001st octet to the 2000th octet are retransmission packets. The queue input switching unit 22 inputs the notified retransmission packet to the retransmission queue 12. As a result, the retransmission packet is transmitted with priority over the initial transmission packet already held in the transmission queue 11. After the retransmission packet is transmitted, the distribution server device 201 stores the initial transmission packet having the data from the 7001st octet to the 8000th octet and the data from the 8001st octet to the 9000th octet already held in the transmission queue 11. The initial transmission packets are sequentially transmitted to the client device 202-1.

  The client device 202-1 receives a retransmission packet having data from the 1001st octet to the 2000th octet. The client device 202-1 received each initial transmission packet having data from the 2001th octet to the 7000th octet before receiving the retransmission packet. As a result, the client apparatus 202-1 transmits an ACK packet with an acknowledgment number 7001 to the distribution server apparatus 201.

  The distribution server apparatus 201 recognizes that the client apparatus 202-1 has received the data up to the 7000th octet by receiving a new ACK packet with the confirmation response number 7001. The distribution server device 201 resumes the process of holding the initial transmission packet having new data in the transmission queue 11 when receiving the new ACK packet. Thus, each initial transmission packet having data after the 9001st octet is sequentially transmitted from the distribution server device 201 to the client device 202-1.

  According to the third embodiment, when a packet is retransmitted according to the TCP procedure, the retransmission packet can be transmitted promptly.

According to the third embodiment, the following effects can be obtained. Here, the client device 202-1 of the client devices 202-1, 2,..., N shown in FIG. 5 will be described as an example, but the other client devices 202-2,. The same applies to.
TCP includes procedures for window control, flow control, and congestion window control in order to improve communication efficiency. In order to utilize these procedures, the buffer capacity of the transmission buffer 21 of the distribution server device 201 for each session is set to an amount sufficient for the amount of data that can be received by the client device 202-1. In this way, packets corresponding to the amount of data that can be received by the client device 202-1 can be held in the transmission buffer 21 in advance. Then, the packet held in the transmission buffer 21 is held in the transmission queue 11 when transmission to the client device 202-1 becomes possible according to the procedure of window control, flow control, and congestion window control. Thus, by transmitting packets sequentially from the transmission queue 11, smooth data distribution from the distribution server device 201 to the client device 202-1 can be realized.

  On the other hand, the packet held in the transmission buffer 21 is held for retransmission after being transmitted to the client device 202-1. Therefore, in order to create a vacant space in the transmission buffer 21 and prepare a packet having new distribution data in the transmission buffer 21, it is important to promptly confirm delivery of the transmitted packet. Further, it is possible to smoothly advance the window and increase the window size by promptly confirming the delivery of the transmitted packet.

  According to the third embodiment, since a retransmission packet can be transmitted promptly, an effect of realizing prompt delivery confirmation of a transmitted packet can be obtained. Accordingly, it is possible to contribute to improving communication efficiency by utilizing the procedures of window control, flow control, and congestion window control provided in TCP.

  According to the third embodiment, since retransmission packets can be transmitted promptly, content data that is insufficient in the client device 202-1 due to unarrival of packets can be quickly delivered to the client device 202-1. . As a result, when the distribution server device 201 provides, for example, a VOD (Video On Demand) service, an effect of preventing the client device 202-1 from running out of video content reproduction data can be obtained.

  According to at least one embodiment described above, a transmission queue that holds only initial transmission packets that are waiting to be transmitted among initial transmission packets that are packets transmitted for the first time to a destination packet reception apparatus, and a destination packet reception apparatus A retransmission queue that holds only retransmission packets waiting to be transmitted among the retransmission packets that are retransmitted to the transmitter, a transmission unit that transmits the input initial transmission packet and the input retransmission packet, and the transmission unit, A transmission switching unit that switches between input of an initial transmission packet held in the transmission queue and input of a retransmission packet held in the retransmission queue, and the transmission switching unit holds in the retransmission queue If there is a retransmission packet to be transmitted, the retransmission packet held in the retransmission queue is input to the transmission unit to retransmit the packet. It can be quickly executed.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Packet transmitter, 2 ... Packet receiver, 3 ... Packet switching network, 4 ... Communication line, 5 ... Communication line, 5-1, 2, ..., n ... Communication line, 11 ... Transmission queue, 12 ... Retransmission queue, 13 ... transmission switching unit, 14 ... transmission unit, 21 ... transmission buffer, 22 ... queue input switching unit, 201 ... distribution server device, 202-1, 2, ..., n ... client device, 203 ... IP Network 211 ... Content storage unit 212 ... Application unit 221 ... Receiving unit 222 ... Reception buffer

Claims (6)

Among the initial transmission packets that are packets transmitted for the first time to the destination packet receiver, a transmission queue that holds only the initial transmission packets waiting to be transmitted,
Among retransmission packets that are retransmitted to the destination packet receiving device, a retransmission queue that holds only retransmission packets waiting to be transmitted,
A transmitter for transmitting the input initial transmission packet and the input retransmission packet;
A transmission switching unit that switches between the initial transmission packet held in the transmission queue or the retransmission packet held in the retransmission queue to the transmission unit;
With
When there is a retransmission packet held in the retransmission queue, the transmission switching unit inputs the retransmission packet held in the retransmission queue to the transmission unit.
Packet transmitter. A transmission buffer for holding packets transmitted from the transmission unit;
A queue input switching unit that inputs an initial transmission packet from the packets held in the transmission buffer to the transmission queue, and inputs a retransmission packet from the packets held in the transmission buffer to the retransmission queue;
The packet transmission device according to claim 1. A retransmission packet is determined from the packets held in the transmission buffer based on the information received from the packet reception device that is the destination of the packet transmitted from the transmission unit and specifying the packet received by the packet reception device. A retransmission packet determination unit for notifying the queue input switching unit of the determined retransmission packet,
The packet transmission device according to claim 2. A step in which the transmission queue holds only initial transmission packets waiting to be transmitted among initial transmission packets that are packets transmitted for the first time to a destination packet reception device;
The retransmission queue holds only retransmission packets waiting to be transmitted among retransmission packets that are retransmitted to the destination packet receiving device;
A step of transmitting the input initial transmission packet and the input retransmission packet;
A step of switching whether the transmission switching unit inputs an initial transmission packet held in the transmission queue or a retransmission packet held in the retransmission queue to the transmission unit;
Have
When there is a retransmission packet held in the retransmission queue, the transmission switching unit inputs the retransmission packet held in the retransmission queue to the transmission unit.
Packet transmission method. A transmission buffer holding a packet transmitted from the transmission unit;
A queue input switching unit inputting an initial transmission packet from the packets held in the transmission buffer to the transmission queue, and inputting a retransmission packet from the packets held in the transmission buffer to the retransmission queue; ,
The packet transmission method according to claim 4, comprising: The retransmission packet determining unit receives the packet held in the transmission buffer based on the information received from the packet receiving device that is the destination of the packet transmitted from the transmitting unit and identifying the packet received by the packet receiving device. Determining a retransmission packet from the inside, and notifying the determined retransmission packet to the queue input switching unit;
The packet transmission method according to claim 5.

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