WO2012014397A1

WO2012014397A1 - Communication apparatus, communication system, packet retransmission control method and packet retransmission control program

Info

Publication number: WO2012014397A1
Application number: PCT/JP2011/004003
Authority: WO
Inventors: 淳一樋口; 飛鷹　洋一
Original assignee: 日本電気株式会社
Priority date: 2010-07-26
Filing date: 2011-07-13
Publication date: 2012-02-02
Also published as: JPWO2012014397A1; JP5761193B2

Abstract

A communication apparatus comprises: a plurality of order buffers that are disposed for the respective ones of nets and that accumulate packets until an order confirmation is performed; a dropout detecting unit that, if one or more packets are accumulated in each of the order buffers, determines that a dropout has occurred; a retransmission requesting unit that, if at least a packet dropout has been detected, transmits a retransmission request packet to request a retransmission of the dropping-out packet; an order buffer release moment information adding unit that adds, to the retransmission request packet transmitted by the retransmission requesting unit, order buffer release moment information that is information for reporting an order buffer release moment; and an order buffer release moment identifying unit that refers to the order buffer release moment information added to the retransmission request packet, thereby determining whether the retransmission is necessary.

Description

Communication apparatus, communication system, packet retransmission control method, and packet retransmission control program

The present invention relates to a communication apparatus, a communication system, a packet retransmission control method, and a packet retransmission control program that perform multipath communication in which data is distributed over a plurality of paths.

For example, as described in Patent Document 1, there is a multipath communication method in which data of one communication flow used in communication between a transmission terminal and a reception terminal is branched into a plurality of paths and the original flow is restored. .

Further, in Patent Document 2, in a communication system in which a transmitter and a receiver are connected by a plurality of networks in which packet order inversion does not occur in the network, an order buffer for storing packets until order confirmation is performed for each network. And a packet loss detection method for detecting packet loss by monitoring a packet retention state in an order buffer provided for each network. Note that in the packet loss detection method described in Patent Document 2 (hereinafter referred to as a high-speed packet loss detection method), when one or more packets are accumulated in all the order buffers, the packet loss (packet loss, packet loss) is detected. , Also referred to as packet loss). When this method is used, packet loss can be detected at a higher speed than when a retransmission request is made after waiting for a timeout.

JP 2008-71156 A JP 2009-55419 A

By the way, the high-speed packet loss detection method described in Patent Document 2 is a method for detecting packet loss by monitoring a packet retention state in each sequence buffer when a packet is extracted from the sequence buffer. However, inconsistencies such as rejuvenation of the order number of the arrival packet can be determined before storing in the order buffer. When such a mismatch is detected, the packet sequence can be recovered at a higher speed by making a retransmission request immediately.

However, in the high-speed packet loss detection method described in Patent Document 2, when a packet loss is detected due to a packet retention state, the order buffer is not discarded. When rejuvenation of the order number is detected in the retransmitted packet, the old packet (the packet transmitted on the route before the retransmission request) is discarded. As a result, a retransmission request occurs again. When such retransmission requests are duplicated under high load, the bandwidth of the route due to retransmission is consumed, and there is a problem that the throughput of the entire system is lowered.

Therefore, the present invention provides a communication apparatus, communication system, and packet that can suppress a decrease in throughput of the entire system even when the load is high, in a case where a combination of high-speed packet loss detection and a retransmission request that is determined upon arrival of a packet. An object of the present invention is to provide a retransmission control method and a packet retransmission control program.

A communication apparatus according to the present invention is a communication apparatus in a communication system in which a transmitter and a receiver are connected by a plurality of networks in which packet order inversion does not occur in the network, and stores packets until the order is confirmed. A plurality of sequence buffers installed for each network, a loss detection unit that determines that a loss has occurred when at least one packet is accumulated in all of the order buffers, and at least a packet loss is detected In addition, a retransmission request unit that transmits a retransmission request packet for requesting retransmission of a missing packet, and an order buffer release trigger that is information for notifying the retransmission request packet transmitted by the retransmission request unit of an order buffer release trigger Refer to the order buffer release trigger information mounting unit that loads the information and the order buffer release trigger information mounted in the retransmission request packet, and retransmission is required. Characterized in that it comprises a sequence buffer release trigger identifying section for determining Luke.

In the communication system according to the present invention, the transmitter and the receiver are connected by a plurality of networks in which packet order inversion does not occur in the network, and the receiver accumulates packets until the order is confirmed. A plurality of sequence buffers installed for each network, a missing detection unit that determines that a loss has occurred when one or more packets are accumulated in all of the order buffers, and at least a packet loss is detected, Retransmission request unit for transmitting retransmission request packet for requesting retransmission of missing packet, and order buffer release trigger information which is information for notifying the order buffer release trigger to retransmission request packet transmitted by retransmission request unit A sequence buffer release trigger information loading unit to be mounted, and the transmitter refers to the sequence buffer release trigger information mounted in the retransmission request packet and requires retransmission. Characterized in that it comprises the sequence buffer release trigger identifying section for determining whether.

The packet retransmission control method according to the present invention is a packet retransmission control method applied to a communication system in which a transmitter and a receiver are connected by a plurality of networks in which packet order inversion does not occur in the network, The receiver accumulates the packets in the order buffer for each network until the order is confirmed, and determines that a loss has occurred when one or more packets are accumulated in all of the order buffers, and at least the packet loss is detected. A retransmission request packet for requesting retransmission of a missing packet, and transmitting a retransmission request packet with order buffer release trigger information, which is information for notifying an order buffer release trigger, It is characterized in that the transmitter refers to the order buffer release trigger information mounted in the retransmission request packet and determines whether or not retransmission is necessary.

In addition, the packet retransmission control program according to the present invention provides an order to a computer installed in a communication apparatus in a communication system in which a transmitter and a receiver are connected by a plurality of networks in which packet order inversion does not occur in the network. Processing for accumulating packets in the sequence buffer for each network until confirmation, processing for determining that a loss has occurred when one or more packets are accumulated in all the order buffers, and packet loss by at least the loss detection unit When it is detected, a retransmission request packet for requesting retransmission of the missing packet is transmitted, and the retransmission request packet loaded with the order buffer release trigger information, which is information for notifying the order buffer release trigger, is transmitted. Whether resending is required by referring to the processing and release information of the sequence buffer mounted in the resending request packet Characterized in that for executing processing decision to.

According to the present invention, when a high-speed packet loss detection is performed in combination with a retransmission request that is determined upon arrival of a packet, it is possible to suppress a decrease in the throughput of the entire system even at a high load.

It is a block diagram which shows the example of whole structure of the communication apparatus of embodiment. Is a flow chart illustrating an example of the operation of the sequence buffer control. It is a flowchart which shows an example of the operation | movement of ACK transmission control. It is a flowchart which shows an example of the operation | movement at the time of ACK reception. It is a sequence diagram which shows the example of the packet exchanged between the communication apparatuses of embodiment. It is a block diagram which shows the operation example of the receiver 2 at the time of a packet loss. It is a block diagram which shows the operation example of the receiver 2 at the time of a packet loss. It is a block diagram which shows the operation example of the receiver 2 at the time of a packet loss. It is a block diagram which shows the operation example of the receiver 2 at the time of a packet loss. It is a block diagram which shows the operation example of the receiver 2 at the time of a packet loss. It is a block diagram which shows the outline | summary of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the following description, communication between a pair of transmitter and receiver is defined as one flow. Also, define the path that flows through the path with. For example, when communicating by distributing one flow to four networks (networks), it is preferable to communicate using four paths. When communicating by distributing two flows to four networks (networks), eight flows are used. Communicate using a path. However, in the following description, the description is given focusing on one flow, and as a result, the network and the path are synonymous.

FIG. 1 is a block diagram showing a configuration example of a communication apparatus according to an embodiment of the present invention. In the example illustrated in FIG. 1, the transmitter 1 includes a data transmission unit 11, a SEQ addition unit 12, a retransmission buffer 13, a distribution unit 14, a retransmission timer 15, and an order buffer release trigger identification unit 16. The receiver 2 also includes an order buffer 211 to 214, a loss detection unit 20, an extraction control unit 22, an ACK transmission unit 23, an output buffer 24, a SEQ deletion unit 25, a data reception unit 26, and a buffer release trigger information mounting portion 27.

In FIG. 1, two communication apparatuses having different configurations, ie, a transmitter 1 and a receiver 2, are shown as examples. However, a communication apparatus that satisfies both the transmission function and the reception function is provided on the transmission side and the reception side. Each may be provided. For example, in the example shown in FIG. 1, instead of the transmitter 1 and the receiver 2, two communication devices including both the components of the transmitter 1 and the components of the receiver 2 may be used. Is possible.

FIG. 1 shows an example in which one flow is distributed over four networks for communication. For this reason, the receiver 2 includes four order buffers (order buffers 211 to 214). However, the order buffer may be provided according to the number of networks that the receiver 2 uses for reception. For example, when three networks are used for communication, it is sufficient that three order buffers are provided.

First, the configuration of the transmitter 1 will be described. The data transmitter 11 generates data to be transmitted to the receiver 2 and passes it to the SEQ adder 12. In general, a server application or the like corresponds to a data transmission unit.

The SEQ adding unit 12 receives data to be transmitted from the data transmitting unit 12 to the receiver 2, divides the received data into sizes that can be transferred by the networks 31 to 34, and divides the individual data (hereinafter referred to as packets). A header and an order number (also referred to as a sequence number, hereinafter referred to as “SEQ”) necessary for transfer are set to the retransmission buffer 13.

The retransmission buffer 13 is a FIFO buffer and performs the following operations.

(1) Receive and store a packet with SEQ from the SEQ assigning unit 12.

(2) Send a copy of the received packet with SEQ to the distribution unit 14 according to a predetermined speed and number. At this time, the retransmission timer 15 is set.

(3) A delivery confirmation (ACK) is received from the ACK transmission unit 23, and the stored packet to which a SEQ value equal to or less than the received SEQ described in the ACK is deleted is deleted. In this case, re-set the retransmission timer 15.

(4) In (3), if the SEQ described in the ACK is the same as the SEQ described in the previously received ACK, it is regarded as a retransmission request (duplicate ACK). Then, for the packets after SEQ described in ACK, a copy of the packet is retransmitted to the distribution unit 14 according to a predetermined speed and number as in (2).

(5) When the retransmission timer 15 expires, for the packets after the SEQ described in the previously received ACK, a duplicate of the packet is retransmitted to the distribution unit 14 according to a predetermined speed and number as in (2). .

The distribution unit 14 sequentially distributes packets arriving from the retransmission buffer 13 to the networks 31 to 34 by a round robin method or the like.

When the retransmission request is received from the retransmission buffer 13, the retransmission timer 15 notifies the retransmission buffer 13 of expiration of the timer when a preset time has elapsed.

The order buffer release trigger identification unit 16 refers to the information in the order buffer release trigger notification field mounted on the ACK or the like from the opposite receiver 2 for identification. Here, the order buffer release timing notification field is information for registering information indicating the timing at which the receiver 2 releases the order buffer, which is a transmission factor of the message to which the field is assigned. In the present embodiment, the information indicates whether or not the sequence buffer is released by SEQ rejuvenation.

The sequence buffer release trigger identification unit 16 retransmits when the information in the sequence buffer release trigger notification field is a retransmission request notification by sequence buffer release by SEQ rejuvenation based on retransmission packet reception after high-speed packet loss detection. No retransmission request is made to the buffer 13. Since no retransmission request is made, no retransmission is performed. If the retransmission request is other than that, the retransmission request is made to the retransmission buffer 13.

Next, the configuration of the receiver 2. Each of the order buffers 211 to 214 is a FIFO buffer. The order buffers 211 to 214 receive a packet from the associated network (any of the networks 31 to 34), temporarily store the packet, and notify the extraction control unit 22 of the storage completion. Further, the stored packet is transferred to the output buffer 24 in accordance with an instruction from the extraction control unit 22.

Also, the order buffers 211 to 214 compare the SEQ of the packet that has arrived from the associated network with the SEQ of the packet that has arrived from the network last time. The order buffers 211 to 214 consider that retransmission has occurred when the SEQ of the packet that has arrived this time is smaller than or equal to the SEQ of the packet that has arrived last time. When the order buffers 211 to 214 consider that retransmission has occurred, all the stored packets are discarded (deleted), and the order buffer is released. Then, the order buffers 211 to 214 notify the loss detection unit 20 to that effect as an order buffer release trigger (buffer release notification by SEQ rejuvenation). If no packet is stored in the order buffer, it is not considered that the buffer has been released, and no notification is made.

Note that the order buffers 211 to 214 may sequentially store the packets received by retransmission after clearing the order buffer. In such a case, after notifying the drop detection unit 20 of the buffer release notification, the storage control unit 22 is notified of the storage completion. The same applies when an order buffer overflow occurs. In this case, the loss detection unit 20 is notified of buffer release due to buffer overflow.

Upon receipt of a packet extraction completion notification from the extraction control unit 22, the missing detection unit 20 confirms whether there is a packet loss. If a packet loss is found, a retransmission request is made to the ACK transmission unit 23. In addition, when the order buffer is released due to the packet loss detection, the order buffer release opportunity information loading unit 27 is notified of the order buffer release opportunity.

The fetch control unit 22 receives the storage completion notification from the order buffers 211 to 214 and activates the order confirmation operation 221. The take-out control unit 22 transfers the packet to the output buffer 24 according to the sequence of SEQ. At this time, the ACK transmission unit 23 is notified of the SEQ of the packet transferred to the output buffer 24.

The ACK transmission unit 23 and the order buffer release opportunity information mounting unit 27 perform the following operations. In the present embodiment, as an example, a 1ACK scheme is employed in which an ACK of one packet is transmitted every time one packet transfer to the output buffer 24 is completed. However, an N_ACK scheme may be used in which N (N is 1 or more) packet arrival reports are collected together with one ACK.

(1) When receiving the SEQ notification of the packet transferred from the take-out control unit 22 to the output buffer 24, the ACK transmission unit 23 generates an ACK including the SEQ. The order buffer release opportunity information mounting unit 27 notifies the transmitter 1 of ACK. At this time, the ACK is notified using any of the networks 31 to 34. In addition, the ACK transmission unit 23 stores the notified SEQ.

(2) Upon receiving a retransmission request from the loss detection unit 20, the ACK transmission unit 23 again generates an ACK including the SEQ stored in (1). The order buffer release trigger information mounting unit 27 mounts the order buffer release trigger information in the ACK and notifies the transmitter 1 of it. The ACK is notified using any of the networks 31 to 34. The ACK in (2) is handled as a duplicate ACK (retransmission request) in the transmitter 1.

The output buffer 24 is a FIFO buffer. The output buffer 24 stores the packets received from the order buffers 211 to 214. The output buffer 24 outputs the packets to the SEQ deletion unit 25 in the order in which they are stored when a request is received from the SEQ deletion unit 25.

The SEQ deleting unit 25 receives a packet from the output buffer 24. The SEQ deleting unit 25 deletes the SEQ and the header from the packet, and transfers the data after the SEQ deletion to the data receiving unit 26.

The data receiving unit 26 receives data from the SEQ deleting unit 26. The data receiving unit 26 is generally called a client application.

The networks 31 to 34 are networks that connect between the transmitter 1 and the receiver 2, respectively. Assume that the networks 31 to 34 are networks such as Ethernet that do not reverse the order of packets in the network. In FIG. 1, each network is represented by a single line. However, in practice, a switch or the like may exist in addition to the link as long as packet order inversion does not occur in the network. Each network is either physically blocked or logically blocked by a VLAN or the like. That is, it is assumed that the networks do not intersect each other.

In this embodiment, the data transmission unit 11 and the SEQ addition unit 12 are realized by a processor unit that operates according to a program such as a CPU. The distribution unit 14 and the order buffer release opportunity identification unit 16 are realized by a processor unit that operates according to a program such as a hardware and a CPU that realizes a communication function with each network. The retransmission timer 15 is realized by a processor unit that operates in accordance with a program such as hardware or a CPU that implements a time measuring function. The retransmission buffer 13 is realized by a storage device and a control unit that controls the storage device (may be a processor unit that operates according to a program such as a CPU).

Further, the data receiving unit 26, the SEQ deleting unit 25, the take-out control unit 22, and the missing detection unit 20 are realized by a processor unit that operates according to a program such as a CPU. The ACK transmission unit 23 and the order buffer release opportunity information mounting unit 27 are realized by a processor unit that operates according to a program such as hardware and a CPU that realizes a communication function with each network. The order buffers 211 to 214 are realized by hardware that realizes a communication function with each network, a storage device, and a control unit that controls the hardware (may be a processor unit that operates according to a program such as a CPU). The Further, the output buffer 24 is implemented by a storage device.

Next, the operation of this embodiment will be described. FIG. 2 is a flowchart illustrating an example of the order confirmation operation 221 performed by the take-out control unit 22 of the receiver 2.

In the example shown in FIG. 2, the take-out control unit 22 activates the order confirmation operation 221 when a storage completion notification is made after one packet is stored in any of the order buffers 211 to 214 (step 22101). ).

In the order confirmation operation 221, the extraction control unit 22 first confirms the SEQ of the packet stored at the head (on the output buffer 24 side) of the order buffer 211 (step 22102).

The fetch control unit 22 confirms the SEQ (head SEQ) of the first packet of the order buffer 211 confirmed in step 22102, and the SEQ (reception expected SEQ, which is to be transmitted to the output buffer 24 next by the order control unit 22). referred) and comparing (step 22103).

As a result of the comparison, if the leading SEQ and the expected SEQ match, the takeout control unit 22 takes out the packet from the order buffer 211 and sends it to the output buffer 24 (step 22104).

Next, the take-out control unit 22 requests the ACK transmission unit 23 to transmit an acknowledgment packet (ACK). This ACK stores the SEQ of the expected SEQ. Accordingly, the transmitter 1 is notified that the reception and ordering up to the expected SEQ have been completed (step 22105).

Then, the take-out control unit 22 increments the expected SEQ. That is, expected SEQ = expected SEQ + 1 (step 22106).

The take-out control unit 22 performs the same operation as the steps 22102 to 22106 with respect to the order buffer 212 in steps 22107 to 22111.

The extraction control unit 22 performs the same operation as the steps 22102 to 22106 with respect to the order buffer 213 in steps 22112 to 22116.

In step 22117 to 22121, the extraction control unit 22 performs the same operation as that of steps 22102 to 22106 with respect to the order buffer 214.

As described above, the fetch control unit 22 counts the number of packets taken out from the order buffer and sent to the output buffer in the SEQ confirmation operation for each order buffer. If the number of packets is 1 or more, the takeout control unit 22 executes the processing after step 22102 again.

On the other hand, when the number of packets taken out from the order buffer and sent to the output buffer is zero, that is, there are no packets that can be transferred to the output buffer 23 (that is, that can be ordered) in any of the order buffers 211 to 214. In this case, the take-out control unit 22 executes the process of step 22123 (step 22122).

In Step 22312, the extraction control unit 22 notifies the loss detection unit 20 of the completion of packet extraction and activates the loss detection operation.

Next, the operation of the missing detection unit 20 will be described with reference to FIG. FIG. 3 is a flowchart illustrating an operation example of the missing detection unit 20. For example, upon receiving a packet extraction completion notification from the order confirmation operation 221, the loss detection unit 20 activates the loss detection operation (step 2000). Note that the missing detection unit 20 may start the missing detection operation at a time other than when the packet extraction completion notification is received from the order confirmation operation 221. For example, when a buffer release notification is received from the order buffers 211 to 214, a missing detection operation is started.

In the missing detection operation, the missing detection unit 20 first checks whether the order buffer has been cleared (step 2001).

If the order buffer has not been cleared, the missing detection unit 20 checks the number of packets stored in the order buffer 211 (step 2002).

If the number of packets stored in the order buffer 211 is 0, the missing detection unit 20 ends the operation. When the number of stored packets is 1 or more, the process proceeds to step 2004 (step 2003).

In step 2004 and step 2005, the missing detection unit 20 performs the same operation as step 2002 and step 2003 with respect to the order buffer 212.

In step 2006 and step 2007, the missing detection unit 20 performs the same operation as step 2002 and step 2003 with respect to the order buffer 213.

In step 2008 and step 2009, the missing detection unit 20 performs the same operation as step 2002 and step 2003 with respect to the order buffer 214.

As described above, the loss detection unit 20 checks the number of packets stored in each order buffer. When the storage of one or more packets is confirmed in all of the order buffers 211 to 214, the loss detection unit 20 makes a transmission request to the ACK transmission unit 23. The ACK transmission unit 23 that has received the transmission request generates an ACK (duplicate ACK) including the same SEQ as the previously transmitted ACK, and makes a retransmission request to the transmitter 1 (step 2012).

If the order buffer is cleared in step 2001, the missing detection unit 20 confirms whether or not the SEQ has been rejuvenated (step 2010).

When there is no SEQ rejuvenation, the missing detection unit 20 makes an ACK transmission request to the ACK transmission unit.

If there is a rejuvenation of SEQ, the missing detection unit 20 sets an order buffer release trigger flag (step 2011), and makes a transmission request to the ACK transmission unit 23. At this time, the ACK transmission unit 23 generates an ACK (duplicate ACK) including the same SEQ as the ACK transmitted last time and makes a retransmission request to the transmitter 1. An ACK with a release trigger flag set is transmitted.

FIG. 4 is a flowchart showing an operation example of the order buffer release opportunity information identification unit 16. In the example illustrated in FIG. 4, when the ACK is transmitted from the receiver 2 and arrives at the transmitter 1 (step 3000), the order buffer release opportunity information identification unit 16 receives a duplicate ACK (that is, a retransmission request). (Step 3001).

If it is not a duplicate ACK, the order buffer release opportunity information identification unit 16 processes the received ACK as a normal ACK, and releases the retransmission buffer (step 3002).

On the other hand, if it is a duplicate ACK, the order buffer release opportunity information identifying unit 16 checks the order buffer release opportunity flag in the order buffer release opportunity notification field in the received ACK (step 3003).

When the sequence buffer release trigger flag indicates that the sequence buffer is released due to SEQ rejuvenation, the sequence buffer release trigger information identification unit 16 terminates the processing without receiving the ACK as a retransmission request, although it is a retransmission request.

On the other hand, when the order buffer release trigger flag does not indicate release of the order buffer due to SEQ rejuvenation, the order buffer release trigger information identification unit 16 issues a retransmission instruction to the retransmission buffer with the received ACK as a retransmission process target ( Step 3004).

Hereinafter, an operation example of this embodiment will be described with reference to the sequence diagram of FIG. Note that FIG. 5 shows an example in which one flow is distributed over two networks (networks 31 and 32) for communication for the sake of simplicity. Therefore, it is assumed that the receiver 2 includes two order buffers (order buffers 211 to 212). In FIG. 5, a packet transmitted using the network 31 is indicated by a solid line arrow, and a packet transmitted using the network 32 is indicated by a broken line arrow.

First, in the transmitter 1, the data transmission unit 11 generates data for the data reception unit 26 and sends the data to the SEQ addition unit 12.

The SEQ adding unit 12 divides the data from the data transmission unit 12 into sizes that can be transferred by the networks 31 to 32, and attaches a header to each data to generate a packet. Further, a sequence number (SEQ) is assigned to the packet for ordering so that the receiver 2 can restore the data, and the packet is transferred to the retransmission buffer 13.

The retransmission buffer 13 receives the packet from the SEQ adding unit 12 and temporarily stores it. Then, a copy of the stored packet is sent to the distribution unit 14 in accordance with a preset transmission rate, window size, and the like.

The distribution unit 14 distributes and transmits the packet received from the retransmission buffer 13 to each of the networks 31 to 32 by a round robin method or the like. For example, packets with a sequence of SEQ are distributed to the networks 31 to 32, such as the network 31 for the SEQ0 packet, the network 32 for the SEQ1 packet, the network 31 for the SEQ2 packet, and the network 32 for the SEQ3 packet.

The networks 31 to 32 send the packets sent from the transmitter 1 to the receiver 2.

In the receiver 2, each of the order buffers 211 and 212 stores a packet that has arrived from the associated network, and notifies the extraction control unit 22 of the completion of storage.

The fetch control unit 22 receives the storage completion notification from the order buffer and activates the order confirmation operation 221.

The order storage operation 221 checks the SEQ of the packet stored at the head of each order buffer. If the SEQ matches the next SEQ to be sent to the output buffer 24 (expected SEQ), the order storage operation 221 extracts this packet, sends it to the output buffer 24, and sends an ACK to the ACK transmitter 23. Request. For example, when transfer to the output buffer 24 has been completed up to SEQ = 5 before, if a packet with SEQ = 6 is stored at the head of any of the sequence buffers, the sequence storage operation 221 extracts this. To the output buffer and request ACK transmission of SEQ = 6.

In addition, when the packet to be transferred to the output buffer cannot be found in any of the order buffers, the order confirmation operation 221 notifies the missing detection unit 20 of the completion of extraction.

Upon receipt of the extraction completion notification from the extraction control unit 22, the missing detection unit 20 checks the number of packets stored in each order buffer. If the storage of the packet is confirmed in all the order buffers, the loss detection unit 20 determines that a packet loss has occurred and makes a retransmission request to the ACK transmission unit 23. When receiving a buffer release notification from each sequence buffer, the loss detection unit 20 makes a retransmission request according to the buffer release factor to the sequence buffer release trigger information mounting unit 27 and the ACK transmission unit 23.

The ACK transmission unit 23 transmits ACK to the opposite transmitter 1 in response to a request from the take-out control unit 22 or the loss detection unit 20. In the case of a retransmission request, a duplicate ACK with SEQ = expected SEQ−1 is transmitted.

Note that the output buffer 24 receives the packet from the order buffer, and extracts and transfers the packet by the FIFO method in response to a request from the SEQ deletion unit 25.

The SEQ deleting unit 25 takes out the packet from the output buffer 24, deletes the header (including SEQ), and transfers the data to the data receiving unit 26.

The data receiving unit 26 receives 0 and others from the SEQ deleting unit 25 and performs various processes.

The sequence buffer release opportunity identification unit 16 of the transmitter 1 receives the packet from the receiver 2 and, when a SEQ larger than the SEQ of the ACK received last time is included, the packet up to the SEQ is retransmitted from the retransmission buffer 13. to erase. If the same SEQ as the SEQ of the previously received ACK is included, the order buffer release opportunity identification unit 16 regards it as a duplicate ACK (retransmission request), and immediately converts the packet stored in the retransmission buffer into SEQ Resend in order from the youngest.

With reference to FIG. 5, a more detailed operation of the communication apparatus will be described by taking as an example a case where a packet loss due to an FCS error or the like occurs in a high load state where the transmitter 1 transmits packets at a full rate. FIG. 5 shows an example when a packet with SEQ = 10 is lost.

FIG. 6 is a block diagram illustrating an operation example of the receiver 2 when a packet is lost. In the example shown in FIG. 6, the packets 1 to 9 are transferred to the output buffer 24 by the order storage operation 221. In response to these packets, ACKs 1 to 9 are sent out by the ACK transmission unit 23 and the order buffer release opportunity information identification unit 16. If there is no particular description in the figure, it is assumed that the value of the order buffer release trigger flag is not set (a value indicating that the order buffer is not released by SEQ rejuvenation).

When the packet of SEQ = 11 is stored in the order buffer 212, the order confirmation operation 221 is activated. However, since there is no packet (SEQ = 10 packet) that can be sent to the output buffer 24, an extraction completion notification is transmitted to the loss detection unit 20. The missing detection unit 20 checks the number of packets stored in each order buffer. Here, since the packet with SEQ = 12 sent to the network 31 after the missing packet with SEQ = 10 has not been received, the number of packets in the order buffer 211 is zero. Therefore, the missing detection unit 20 ends the process.

Next, when a packet of SEQ = 12 is stored in the order buffer 211, the order confirmation operation 221 is activated again. However, since there is no packet (SEQ = 10 packet) that can be sent to the output buffer 24, an extraction completion notification is transmitted to the loss detection unit 20. The missing detection unit 20 checks the number of packets stored in each order buffer. This time, the loss detection unit 20 confirms that the packet is stored in all the order buffers including the order buffer 211 (that is, the packet is stagnated by skipping the SEQ), and the loss occurs. The ACK transmission unit 23 is requested to retransmit. Hereinafter, this retransmission request may be expressed as a retransmission request due to sequence skipping.

The ACK transmission unit 23 receives a retransmission request from the loss detection unit 20 and transmits an ACK including SEQ = 9 which is the same as the previously transmitted ACK (ACK = 9). The ACK transmission unit 23 does not set the order buffer release trigger flag (for example, 0).

ACKs with the same number arrive at the transmitter 1 continuously. Therefore, the transmitter 1 determines that there is a retransmission request, and retransmits the packet in the retransmission buffer.

Even if a packet loss is detected at high speed by such a high-speed packet drop method and a retransmission request is made, if the transmitter 1 is transmitting a packet at a high bit rate, the retransmission request arrives before The transmitted packet remains on the path (for example, see SEQ = 27 in FIG. 5). Therefore, as shown in FIG. 7, these packets remain in each order buffer without being discarded. FIG. 7 is a block diagram illustrating a state of the buffer of the receiver 1 after making a retransmission request due to sequence skipping.

Thereafter, the receiver 2 receives a packet from SEQ = 10 which is a retransmission packet. For example, when a packet from SEQ = 10 is retransmitted from the network 32, the order buffer 212 recognizes that SEQ rejuvenation has occurred as compared with SEQ = 27 of a packet that has already been received. Then, the order buffer 212 considers that retransmission has occurred, discards all stored packets, and notifies the loss detection unit 20 to that effect (buffer release notification by SEQ rejuvenation).

After the notification, the sequential buffer 212 stores the received SEQ = 10 packet in the discarded buffer, and notifies the extraction control unit 22 of the storage completion.

Upon receiving a buffer release notification from the order buffer 212, the missing detection unit 20 performs a missing detection operation. As a missing detection operation, the missing detection unit 20 first recognizes that the buffer has been released and that the cause is SEQ rejuvenation, and sends a retransmission request due to SEQ rejuvenation to the ACK transmission unit 23 and the order buffer release trigger information. To the unit 27. For example, the missing detection unit 20 may make a retransmission request to the ACK transmission unit 23 after setting the sequence buffer release trigger flag managed by the sequence buffer release trigger information mounting unit 27 to 1 (valid).

The ACK transmission unit 23 and the order buffer release opportunity information mounting unit 27 receive a retransmission request from the loss detection unit 20 and transmit an ACK including SEQ = 9 which is the same as the previously transmitted ACK (ACK = 9). In this case, the order buffer release trigger flag is set to a value (for example, 1) indicating buffer release by rejuvenation. FIG. 8 is a block diagram showing a buffer state of the receiver 1 when a retransmission request is made by receiving a SEQ young number from the network 32.

Also, as shown in FIG. 8, after a retransmission request is made due to the reception of SEQ young number, the sequence buffer 212 stores the received SEQ = 10 packet. When a packet with SEQ = 10 is stored in the order buffer 212, the take-out control unit 22 activates the order confirmation operation 221, takes out the packet having the same SEQ as the expected SEQ, and sends it to the output buffer 24. Then, an ACK (including SEQ = 10) for notifying that it has been normally received is transmitted to the transmitter 1 via the ACK transmitter 23.

On the transmitter 1 side, packets after SEQ = 11 are sequentially transmitted following the packets with SEQ = 10. For example, a packet with SEQ = 11 is transmitted using the network 31. FIG. 9 is a block diagram showing a buffer state of the receiver 1 when a retransmission request is made by receiving a sequence number of SEQ from the network 31. The sequence buffer 211 also detects SEQ rejuvenation and releases the sequence buffer. Here, as in the case where SEQ = 10 is received, the packet stored in the reception buffer 211 is discarded, and a retransmission request (SEQ = 10, including an order buffer release trigger flag = 1) is received by the SEQ young number reception. After being performed, the order buffer 211 stores the received SEQ = 11 packet. Then, the order confirmation operation 221 is activated, and the packet having the same SEQ as the expected SEQ is extracted and sent to the output buffer 24. Then, an ACK (including SEQ = 11) for notifying that it has been normally received is transmitted to the transmitter 1. When three or more networks are used, a retransmission request is received for each path by receiving a sequence number of SEQ.

ACK of the same number arrives at transmitter 1 continuously. If the sequence buffer release trigger information identification unit 16 confirms the sequence buffer release trigger flag and recognizes that the request is a retransmission request due to the SEQ sequence number reception, the retransmission processing is not performed. Therefore, the retransmission process that is currently being processed is continuously performed (see SEQ = 14 to 15 in FIG. 5).

In the above operation example, the retransmission packet is retransmitted by a different network. However, for example, as shown in FIG. 10, when the retransmission packet is transmitted using the network 31, the order buffer 211 is cleared and SEQ = 10. When a packet is stored, SEQ = 11 before retransmission may remain in the order buffer 212. In such a case, the takeout control unit 22 takes out enough data to be taken out, and when the retransmitted SEQ = 11 is stored in the sequence buffer 211 again, SEQ = 11 is the already taken out SEQ. You may make it discard, if there exists. For example, in the case where each of the processes in

steps

22103, 22108, 22113, and 22118 in FIG. 2 is No and the top SEQ is smaller than the expected SEQ, a process for discarding the packet is added. May be.

In the above-described embodiment, the order buffer release trigger information is a flag that takes a binary value of 0 or 1. However, the order buffer release trigger information is, for example, information that takes a binary value or more indicating a release type. There may be.

As described above, according to the present embodiment, a re-transmission request due to reception of a packet that has been transmitted on the route before being retransmitted without being discarded and received on the receiver side is appropriate. Can be processed. Therefore, even if a packet loss occurs when the input to the data transmission unit is heavy, it can be recovered more quickly and bandwidth consumption due to the retransmission can be suppressed.

It should be noted that the subject of the present invention is to suppress bandwidth consumption due to retransmission under high load on the assumption that a high-speed packet drop method is performed. The specific method of the high-speed packet loss method is not limited to the method described in the above embodiment. For example, in the present invention, a configuration in which each order buffer and output buffer are used together is applicable. In such a case, as described in Patent Document 2 cited as the prior art document, the number of waiting for extraction is managed, and the packet for which the order guarantee has been confirmed is not deleted in the order buffer clear when the retransmission packet arrives. This condition may be added. Note that the number of packets for which the order guarantee has been confirmed is equal to the number of waiting for extraction. Therefore, it is only necessary to exclude the packets corresponding to the number of waiting to be taken out of the packets stored in the order buffer, counting from the oldest stored order.

Also, the capacity of each sequence buffer may be determined based on the bandwidth and delay time for each network.

Next, the outline of the present invention will be described. FIG. 11 is a block diagram showing an outline of the present invention. The communication apparatus shown in FIG. 11 includes a sequence buffer 51 (51-1 to 51-n), a loss detection unit 52, a retransmission request unit 53, and an sequence buffer release trigger information mounting unit 54 as functions on the transmission side. Prepare. In addition, an order buffer release opportunity identifying unit 55 is provided as a function on the receiving side.

Order buffers 51-1 to 51-n (for example, order buffers 211 to 214) are installed for each network, and accumulate packets until the order is confirmed.

The missing detection unit 52 (for example, the missing detection unit 20) determines that a loss has occurred when one or more packets are accumulated in all of the order buffers 51-1 to 51-n.

The retransmission request unit 53 (for example, the ACK transmission unit 23) transmits a retransmission request packet for requesting retransmission of the lost packet at least when the packet loss is detected.

The sequence buffer release trigger information mounting unit 54 (for example, the sequence buffer release trigger information mounting unit 27) is a sequence buffer release trigger that is information for notifying the retransmission request packet transmitted by the retransmission request unit 53 of the sequence buffer release trigger. Load information.

In addition, the order buffer release opportunity identification unit 55 (for example, the order buffer release opportunity identification unit 16) refers to the order buffer release opportunity information included in the retransmission request packet and determines whether retransmission is necessary.

Each sequence buffer deletes all the packets already stored in the sequence buffer and releases the sequence buffer when the sequence number rejuvenates in the received packet. Request the retransmission of a packet after the packet whose sequence is currently confirmed when the sequence buffer that stores one or more packets is released The sequence buffer release trigger information loading unit mounts an identifier for identifying the sequence buffer release trigger by rejuvenation of the sequence number of the received packet as the sequence buffer release trigger information. The release opportunity identification unit includes the received packet that has received the sequence buffer release opportunity information included in the retransmission request packet. When the identification information indicates that a sequence buffer release trigger by rejuvenation preparative sequence numbers, may not retransmit.

In addition, each sequence buffer, when the sequence buffer overflows, deletes all the packets already stored in the sequence buffer and releases the sequence buffer. If the installed order buffer release trigger information indicates that the sequence buffer release trigger is not triggered by rejuvenation of the sequence number of the received packet, retransmission may be performed.

Also, the retransmission request unit may retransmit an arrival confirmation response packet to which the sequence number of the packet whose order has been confirmed is assigned as a retransmission request packet.

As mentioned above, although this invention was demonstrated with reference to embodiment and an Example, this invention is not limited to the said embodiment and Example. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application claims priority based on Japanese Patent Application 2010-166928 filed on July 26, 2010, the entire disclosure of which is incorporated herein.

The present invention can be applied to an Ethernet (registered trademark) switch, a router, or the like that transfers a large amount of data at high speed using a plurality of networks. The present invention can also be applied to a network interface card (NIC) that connects servers at high speed.

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Receiver 11 Data transmission part 12 SEQ provision part 13 Retransmission buffer 14 Distribution part 15 Retransmission timer 16 Order buffer release opportunity identification part 20 Missing detection part 211-214 Order buffer 22 Extraction control part 221 Order confirmation operation 23 ACK transmission Unit 24 output buffer 25 SEQ deletion unit 26 data reception unit 17 sequence buffer release trigger information mounting unit 51-1 to 51-n sequence buffer 52 missing detection unit 53 retransmission request unit 54 sequence buffer release trigger information mounting unit 55 sequence buffer release trigger 55 Identification part

Claims

A communication device in a communication system in which a transmitter and a receiver are connected by a plurality of networks in which packet order inversion does not occur in the network,
Multiple sequence buffers installed in each network for storing packets until order confirmation,
A loss detection unit that determines that a loss has occurred when one or more packets are accumulated in all of the sequence buffers;
A retransmission request unit that transmits a retransmission request packet for requesting retransmission of the lost packet, at least when a packet loss is detected;
An order buffer release trigger information mounting unit for mounting order buffer release trigger information that is information for notifying an order buffer release trigger to the retransmission request packet transmitted by the retransmission request unit;
A communication apparatus comprising: an order buffer release trigger identification unit that refers to order buffer release trigger information mounted on the retransmission request packet and determines whether retransmission is necessary.
Each sequence buffer, when sequence number rejuvenation occurs in a received packet, deletes all the packets already stored in the sequence buffer and releases the sequence buffer,
In addition to the case where the packet loss is detected by the loss detection unit, the retransmission request unit is configured to use the packet whose sequence is currently confirmed when the sequence buffer in which one or more packets are stored is released. Send a retransmission request packet requesting retransmission of a later packet,
The sequence buffer release trigger information loading unit has an identifier for identifying the sequence buffer release trigger by rejuvenation of the sequence number of the received packet as the sequence buffer release trigger information,
The sequence buffer release trigger identification unit does not perform retransmission when the sequence buffer release trigger information included in the retransmission request packet indicates that the sequence buffer release trigger is due to rejuvenation of the sequence number of the received packet. Item 4. The communication device according to Item 1.
Each sequence buffer, when the sequence buffer overflows, deletes all the packets already stored in the sequence buffer and releases the sequence buffer,
The sequence buffer release trigger identification unit performs retransmission when the sequence buffer release trigger information included in the retransmission request packet indicates that the sequence buffer release trigger is not triggered by rejuvenation of the sequence number of the received packet. The communication apparatus according to claim 1 or 2.
The communication apparatus according to any one of claims 1 to 3, wherein the retransmission request unit retransmits an arrival confirmation response packet to which the sequence number of the packet whose order has been confirmed is assigned as a retransmission request packet.
A transmitter and a receiver are connected by a plurality of networks that do not cause packet order reversal in the network.
The receiver is
Multiple sequence buffers installed in each network for storing packets until order confirmation,
A loss detection unit that determines that a loss has occurred when one or more packets are accumulated in all of the sequence buffers;
A retransmission request unit that transmits a retransmission request packet for requesting retransmission of the lost packet, at least when a packet loss is detected;
The retransmission request packet transmitted by the retransmission request unit includes an order buffer release trigger information mounting unit that loads order buffer release trigger information that is information for notifying an order buffer release trigger,
The transmitter is
A communication system, comprising: an order buffer release trigger identifying unit that refers to order buffer release trigger information mounted on the retransmission request packet and determines whether retransmission is necessary.
Each sequence buffer, when sequence number rejuvenation occurs in a received packet, deletes all the packets already stored in the sequence buffer and releases the sequence buffer,
In addition to the case where the packet loss is detected, the retransmission request unit, when the order buffer in which one or more packets are stored is released, the packet after the packet whose order is currently confirmed Send a resend request packet requesting resend,
The sequence buffer release trigger information loading unit has an identifier for identifying the sequence buffer release trigger by rejuvenation of the sequence number of the received packet as the sequence buffer release trigger information,
The sequence buffer release trigger identification unit does not perform retransmission when the sequence buffer release trigger information included in the retransmission request packet indicates that the sequence buffer release trigger is due to rejuvenation of the sequence number of the received packet. Item 6. The communication system according to Item 5.
A packet retransmission control method applied to a communication system in which a transmitter and a receiver are connected by a plurality of networks in which packet order reversal does not occur in the network,
The receiver is
Packets are stored in the order buffer for each network until the order is confirmed.
Determining that a loss has occurred when one or more packets are accumulated in all of the sequence buffers;
Retransmission request packet for requesting retransmission of a missing packet at least when a packet loss is detected, and having a sequence buffer release opportunity information that is information for notifying an order buffer release opportunity Send a request packet,
The packet retransmission control method, wherein the transmitter refers to order buffer release opportunity information mounted on a retransmission request packet and determines whether retransmission is necessary.
The receiver
When rejuvenation of sequence numbers occurs in packets received for each network, all the packets already stored in the order buffer are deleted and the order buffer is released.
When a sequence buffer in which one or more packets are stored is released, a request is made to resend a packet after the packet whose sequence is currently confirmed,
The transmitter is
The packet retransmission control according to claim 7, wherein retransmission is not performed when the order buffer release trigger information included in the retransmission request packet indicates that the sequence buffer release trigger is due to rejuvenation of the sequence number of the received packet. Method.
In a computer mounted on a communication device in a communication system in which a transmitter and a receiver are connected by a plurality of networks in which packet order inversion does not occur in the network,
Processing to store packets in the order buffer for each network until the order is confirmed
A process for determining that a loss has occurred when one or more packets are accumulated in all of the order buffers;
Retransmission request packet for requesting retransmission of a missing packet at least when a packet loss is detected, and having a sequence buffer release opportunity information that is information for notifying an order buffer release opportunity A packet retransmission control program for executing a process for transmitting a request packet and a process for determining whether a retransmission is necessary by referring to the order buffer release timing information mounted in the retransmission request packet.
On the computer,
When a sequence number rejuvenation occurs in a packet received for each network, a process of deleting all the packets already stored in the order buffer and releasing the order buffer;
When the sequence buffer that stores one or more packets is released, processing to request retransmission of a packet after the packet whose sequence is currently confirmed, and release of the sequence buffer installed in the retransmission request packet The packet retransmission control program according to claim 9, wherein when the trigger information indicates that an order buffer release trigger is generated due to rejuvenation of the sequence number of the received packet, processing for ignoring the retransmission request is executed.