JP7174248B2 - Communication device, communication control method and program - Google Patents

Description

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

In a system provided with a communication device that relays network communication between clients and servers, data loss (packet loss) occurs when the communication device fails. When data loss occurs, for example, application timeout, connection disconnection, and the like occur, causing problems in communication services.

Therefore, in order to prevent the communication service from being hindered even if the communication device fails, the network communication is restarted by configuring the communication device in a redundant configuration.
As a communication technology based on a conventional redundant configuration, for example, a technology has been proposed in which the standby server computer and the client terminal cooperate with each other, and the state of the standby server computer and the client terminal is coordinated by mutually holding messages in advance. It is

Also, when a failure occurs in the redundant system, a message is sent to the active and standby systems to enable the device with an address different from the active system device address and disable the device with the same address as the active system device address. Techniques for transmitting have been proposed.

Japanese Patent Application Laid-Open No. 2003-337717 JP 2015-22387 A

A communication device that relays network communication is made redundant by arranging an active system and a standby system. The active communication device transmits data from the client terminal to the counterpart device, and the counterpart device receives the transmitted data, terminates the protocol, and then transmits the data to the destination server.

At this time, if the active communication device stops operating due to a failure or the like, the active system is switched to the standby system, and communication is restarted between the communication device that has newly become the active system from the standby system and the opposite device.

However, in the conventional system, if there is unreceived data on the opposite device side before system switching, the communication device that has newly become the active system from the standby system will not know which data the opposite device has not received. difficult to recognize. If the unreceived data is not resent, the communication quality will be degraded even if the communication function is restarted, leading to a decrease in fault tolerance.

In one aspect, an object of the present invention is to provide a communication device, a communication control method, and a program for improving fault tolerance.

A communication device is provided to solve the above problems. A communication device has a storage unit and a control unit. The storage unit stores the received data. When functioning as the first active system, the control unit divides data to generate divided data, adds a header to each of the divided data, performs protocol conversion to generate a plurality of packets, and converts the generated packets to When it is sent to the opposite device and functions as a standby system, the operation of the first active system is monitored, and when the stop of the first active system is detected, the switch to the second active system is notified to the opposite device. and extracts the unreceived divided data contained in the unreceived packet from the data stored in the storage unit based on the unreceived detection information transmitted from the counterpart device, and transmits the extracted unreceived divided data to the counterpart device. do.

Also, in order to solve the above problems, there is provided a communication control method in which a computer controls the above communication device.
Furthermore, in order to solve the above problems, there is provided a program that causes a computer to control the communication device.

According to one aspect, it is possible to improve fault tolerance.

It is a figure for demonstrating a communication apparatus. It is a figure which shows an example of a structure of a communication system. It is a figure which shows an example of the hardware constitutions of a communication apparatus. It is a figure which shows an example of the functional block of a communication apparatus. FIG. 10 illustrates an example of operations when accepting a new connection; FIG. 10 is a diagram illustrating an example of operations when data transmitted from a client terminal is received; FIG. 10 is a diagram illustrating an example of header addition by protocol conversion; FIG. 4 is a diagram showing an example of protocol conversion in chronological order; FIG. 10 is a diagram illustrating an example of an operation when data is transmitted from a counterpart device to a destination; FIG. 4 is a diagram illustrating an example of an operation when a failure of an active communication device is detected; FIG. 10 is a diagram illustrating an example of an operation after a standby communication device is switched to an active communication device; FIG. 10 illustrates an example of an operation sequence when accepting a new connection; FIG. 4 is a diagram showing an example of an operation sequence for receiving transmission data from a client terminal and protocol conversion; FIG. 10 is a diagram showing an example of an operation sequence when data is transmitted from a counterpart device to a destination; FIG. 10 is a diagram showing an example of an operation sequence when a failure of an active communication device is detected;

Hereinafter, this embodiment will be described with reference to the drawings.
[First embodiment]
FIG. 1 is a diagram for explaining a communication device. The communication device 1 includes a control unit 1a and a storage unit 1b, and performs, for example, relay transmission of client/server network communication.

The storage unit 1b stores at least received data. When functioning as the first active system, the control unit 1a divides data to generate divided data, adds a header to each of the divided data, performs protocol conversion to generate a plurality of packets, and generates a plurality of packets. to the opposite device.

Further, when functioning as a counterpart device, the control unit 1a terminates the received packet, transmits the divided data to the destination, and detects an unreceived packet based on the header. The control unit 1a generates non-receipt detection information when detecting a non-received packet.

Furthermore, when the control unit 1a functions as a standby system, the control unit 1a monitors the operation of the first active system. It notifies the opposite device that it has been switched to the working system of No. 2.

When functioning as the second active system, the control unit 1a extracts the unreceived divided data contained in the unreceived packet from the data stored in the storage unit 1b based on the unreceived detection information transmitted from the opposite device. is extracted, and the extracted unreceived divided data is transmitted to the opposite device.

The operation will be described using the example shown in FIG. The communication system Cs1 comprises communication devices 1-1, 1-2, 1-3, a client terminal 2 and a server 3. FIG.
A client terminal 2 is connected to communication devices 1-1 and 1-2. Communication devices 1-1 and 1-2 are connected to each other, and communication device 1-3 is connected to communication devices 1-1 and 1-2. The server 3 is connected to the communication device 1-3.

Communication devices 1-1, 1-2, and 1-3 have the functions of communication device 1. FIG. In this example, the communication device 1-1 functions as a first active system, the communication device 1-2 functions as a standby system or a second active system, and the communication device 1-3 functions as a counterpart device.

[Step S 1 ] The client terminal 2 transmits data addressed to the server 3 . Note that switches (not shown) are arranged between the client terminal 2 and the communication devices 1-1 and 1-2. sent.

[Step S2a] In the communication device 1-1, the control section 1a1 receives the data transmitted from the client terminal 2 and stores it in the storage section 1b1.
[Step S2b] In the communication device 1-2, the control section 1a2 receives the data transmitted from the client terminal 2 and stores it in the storage section 1b2.

[Step S3] The control unit 1a1 divides the received data to generate divided data, adds a header to each of the divided data, performs protocol conversion, and generates a plurality of packets. The control unit 1a1 then transmits the generated packet to the communication device 1-3.

[Step S4] In the communication device 1-3, the control unit 1a3 stores the received packet in the storage unit 1b3. Further, the control unit 1 a 3 terminates the packet, removes the header from the packet, and transmits the divided data after removing the header to the server 3 .

[Step S5] The controller 1a3 detects an unreceived packet based on the header attached to the received packet, and generates unreceived detection information when an unreceived packet is detected.

[Step S6] The controller 1a2 monitors the operation of the communication device 1-1.
[Step S7] When the control unit 1a2 detects that the communication device 1-1 has stopped, it switches from the standby system to the active system and notifies the communication device 1-3 that the system has been switched.

[Step S8a] The controller 1a2 inquires of the communication device 1-3 whether or not there is an unreceived packet.
[Step S8b] Since the controller 1a3 has detected an unreceived packet, it transmits unreceived detection information to the communication device 1-2.

[Step S9] Based on the unreceived detection information transmitted from the communication device 1-3, the control unit 1a2 extracts unreceived divided data contained in the unreceived packet from the data stored in the storage unit 1b2.

[Step S10] The control unit 1a2 transmits the extracted unreceived divided data to the communication device 1-3. The unreceived divided data transmitted from the communication device 1-2 is transmitted to the server 3 by the communication device 1-3.

In this way, the communication device 1-3 facing the communication device 1-1 detects unreceived data based on the header added by the communication device 1-1 during protocol conversion. Further, when the communication device 1-1 stops and the communication device 1-2 becomes the active system during communication between the communication device 1-1 and the communication device 1-3, the communication device 1-2 - Receive non-receipt detection information for non-received data from 3. Then, the communication device 1-2 extracts the non-received data from the storage unit 1b2 based on the non-reception detection information, and transmits it to the communication device 1-3.

With this kind of communication control, even if the active communication device breaks down, unreceived data is transmitted from the standby system to the new active communication device to the opposite side, thereby suppressing deterioration in communication quality. It is possible to improve fault tolerance.

[Second embodiment]
Next, a second embodiment will be described. FIG. 2 is a diagram showing an example of the configuration of a communication system. The communication system Cs2 includes communication devices 10a, 10b, and 10c (collectively referred to as communication devices 10), a client terminal 21 (CL1), a client terminal 22 (CL2), a server 31 (SV1), a server 32 (SV2), A switch 4 and routers 51 and 52 are provided. The communication system Cs2 performs client/server relay communication via a WAN (Wide Area Network) 6, for example.

Client terminals 21 and 22 are connected to a switch 4 (for example, an L2 (layer 2) switch). The communication devices 10a and 10b are made redundant, and the communication device 10a is the active system and is connected to the switch 4 and the router 51. FIG. The communication device 10 b is a standby system and is connected to the switch 4 and the router 51 . Also, the communication devices 10a and 10b are connected to each other.

The WAN 6 is connected to routers 51 and 52, and the router 52 is connected to the communication device 10c (opposite). The servers 31, 32 are connected to the communication device 10c.
In FIG. 2, the two communication devices 10a and 10b are used as a redundant configuration for the communication device located on the client side, but a redundant configuration can also be formed for the communication device located on the server side.

<Hardware>
FIG. 3 is a diagram showing an example of the hardware configuration of the communication device. The communication device 10 is entirely controlled by a processor (computer) 100 .

A memory 101 and a plurality of peripheral devices are connected to the processor 100 via a bus 103 . Processor 100 may be a multiprocessor. The processor 100 is, for example, a CPU (Central Processing Unit), MPU (Micro Processing Unit), DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), or PLD (Programmable Logic Device). Processor 100 may also be a combination of two or more of CPU, MPU, DSP, ASIC, and PLD.

A memory 101 is used as a main storage device of the communication device 10 . The memory 101 temporarily stores at least part of an OS (Operating System) program and application programs to be executed by the processor 100 . Various data required for processing by the processor 100 are stored in the memory 101 .

The memory 101 is also used as an auxiliary storage device for the communication device 10, and stores OS programs, application programs, and various data. The memory 101 may include, as an auxiliary storage device, a semiconductor storage device such as a flash memory or an SSD (Solid State Drive), or a magnetic recording medium such as an HDD (Hard Disk Drive).

Peripheral devices connected to the bus 103 include an input/output interface 102 and a network interface 104 . The input/output interface 102 is connected to a monitor (e.g., LED (Light Emitting Diode), LCD (Liquid Crystal Display), etc.) that functions as a display device for displaying the state of the communication device 10 according to commands from the processor 100 . .

The input/output interface 102 can be connected to an information input device such as a keyboard and a mouse, and transmits signals sent from the information input device to the processor 100 .
Furthermore, the input/output interface 102 also functions as a communication interface for connecting peripheral devices. For example, the input/output interface 102 can be connected to an optical drive device that reads data recorded on an optical disc using a laser beam or the like. Optical discs include Blu-ray Disc (registered trademark), CD-ROM (Compact Disc Read Only Memory), CD-R (Recordable)/RW (Rewritable), and the like.

Also, the input/output interface 102 can connect a memory device and a memory reader/writer. The memory device is a recording medium equipped with a communication function with the input/output interface 102 . A memory reader/writer is a device that writes data to a memory card or reads data from a memory card. A memory card is a card-type recording medium.

The network interface 104 performs network communication interface control, and can use, for example, a NIC (Network Interface Card), a wireless LAN (Local Area Network) card, or the like. Data received by network interface 104 is output to memory 101 and processor 100 .

The processing functions of the communication device 10 can be realized by the hardware configuration as described above. For example, the communication device 10 can perform communication control according to the present invention by having the processors 100 execute respective predetermined programs.

The communication device 10 implements the processing functions of the present invention, for example, by executing a program recorded on a computer-readable recording medium. A program describing the processing content to be executed by the communication device 10 can be recorded in various recording media.

For example, a program to be executed by the communication device 10 can be stored in the auxiliary storage device. The processor 100 loads at least part of the program in the auxiliary storage device into the main storage device and executes the program.

It can also be recorded in a portable recording medium such as an optical disc, memory device, or memory card. A program stored in a portable recording medium can be executed after being installed in an auxiliary storage device under the control of the processor 100, for example. Alternatively, the processor 100 can read and execute the program directly from the portable recording medium.

<Functional block>
FIG. 4 is a diagram showing an example of functional blocks of a communication device. The communication device 10 includes a control section 11 , a storage section 12 and a transmission/reception interface section 13 . The control unit 11 includes a protocol conversion unit 11a, a monitoring unit 11b, and a non-reception detection unit 11c. The storage unit 12 includes a transmission buffer 12a, a reception buffer 12b and a data storage unit 12c.

The transmission/reception interface unit 13 performs interface control for transmission/reception of data or packets. The protocol conversion unit 11a divides the data transmitted from the client terminal to generate divided data, adds a predetermined header to the divided data, performs protocol conversion, and generates packets of a new protocol. The monitoring unit 11b monitors the operation of the redundantly paired communication devices. The unreceived detection unit 11c detects unreceived packets, and generates unreceived detection information when there is an unreceived packet.

The transmission buffer 12a is a buffer used when transmitting protocol-converted packets to the opposite communication device. The reception buffer 12b is a buffer used when receiving protocol-converted packets.

The data storage unit 12c stores data transmitted from the client terminal. The data storage unit 12c is also used to store control information related to operation (for example, connection information when establishing a connection).

Note that the control unit 11 is realized by the processor 100 in FIG. 3, and the storage unit 12 is realized by the memory 101 in FIG. The transmission/reception interface unit 13 is realized by the network interface 104 or the input/output interface 102 in FIG.

<Operation when accepting a new connection>
FIG. 5 is a diagram showing an example of the operation when accepting a new connection.
[Step S21] The client terminal 21 transmits a connection request to the server 31 to request establishment of a new connection.

[Step S22] The communication device 10a terminates the connection request and stores connection information (TCP (Transmission Control Protocol) connection information) cn1 in the data storage unit 12c.

The connection information cn1 includes a connection identifier a1, source information a2 and destination information a3. The connection identifier a1 is a unique identifier (Con1 in this example) within the network for identifying a connection.

The source information a2 is information in which the IP (Internet Protocol) address and port number of the client terminal 21 are paired. The destination information a3 is information in which the IP address and port number of the server 31 are paired.

[Step S23] The communication device 10a notifies the communication device 10c of the request to establish a new connection together with the connection information cn1.
[Step S24] The communication device 10c stores the connection information cn1 received from the communication device 10a in the data storage section 12c.

[Step S25] After establishing a connection (TCP connection) with the server 31 based on the connection information cn1, the communication device 10c notifies the communication device 10a that the connection with the server 31 has been established.

[Step S26] The communication device 10a transmits the connection information cn1 to the communication device 10b.
[Step S27] The communication device 10b stores the connection information cn1 received from the communication device 10a in the data storage section 12c.

The connection information cn1 is held while the connection Con1 is established in each communication device, and is discarded from the data storage unit 12c when the connection is disconnected.
<Operation when receiving data sent from the client terminal>
Next, the operation when the communication apparatus 10a receives data (or packets) transmitted from the client terminals 21 and 22 after connection establishment and performs protocol conversion will be described with reference to FIGS. 6 to 8. FIG.

FIG. 6 is a diagram showing an example of operation when data transmitted from a client terminal is received. Assume that a connection (connection Con1) between the client terminal 21 and the server 31 is established, and a connection (connection Con2) between the client terminal 22 and the server 31 is established.

[Step S31] The client terminal 21 transmits the data D0 addressed to the server 31 to the communication device 10a. If the data length of the data D0 is set to X bits (hereafter, "bit" is omitted), the data up to the data length of X2 (<X) is transmitted first, and then the data up to the data length of (X - X2) is transmitted. Suppose the rest of the data is sent.

[Step S32] The client terminal 22 transmits the data D10 addressed to the server 32 to the communication device 10a. If the data length of the data D10 is Y, data up to a data length of Y2 (<Y) is transmitted first, and then the rest of the data with a data length of (Y−Y2) is transmitted. .

[Step S33] The data D0 and D10 are also transmitted to the standby communication device 10b. For data transmission to the standby communication device 10b, for example, data D0 and D10 are sent from the switch 4 to the communication device 10b by mirroring the switch 4 arranged on the path between the client terminal and the communication device. can be sent.

Alternatively, after the active communication device 10a receives the data D0 and D10, the data D0 and D10 may be transmitted to the standby communication device 10b.
[Step S34] The communication device 10a stores the received streams of data D0 and D10 in its own data storage section (data storage section 12c1) for each connection.

[Step S35] When the data length of the received data is equal to or greater than the threshold value, the communication device 10a divides the received data into predetermined lengths to generate divided data. This example shows an example in which data with a data length of X2 is divided into two by determining that the data length=X2 is equal to or greater than the threshold.

That is, the communication device 10a generates data d1 from 0 to X1 (<X2) and data d2 from X1 to X2. The data length from X2 to X=(XX2) is determined to be within the threshold value and is not divided. In the figure, data of data length=(XX2) is data d3.

Similarly, the communication device 10a determines that the data length of Y2 is greater than or equal to the threshold and divides the data into two. That is, the communication device 10a generates data d11 from 0 to Y1 (<Y2) and data d12 from Y1 to Y2.

The data length from Y2 to Y=(Y−Y2) is determined to be within the threshold value and is not divided. In the figure, data of data length=(Y−Y2) is data d13. In the following description, data d3 and data d13 may also be referred to as divided data.

[Step S36] The communication device 10a adds headers to the divided data d1, d2, d3, d11, d12, and d13 and performs protocol conversion.
[Step S37] The communication device 10a stores the protocol-converted data in the transmission buffer 12a.

[Step S38] The communication device 10b stores the received streams of data D0 and D10 in its own data storage unit (data storage unit 12c2) for each connection. Note that protocol conversion processing is not performed in the standby communication device 10b.

FIG. 7 is a diagram showing an example of header addition by protocol conversion. The communication device 10a adds a communication protocol header to all of the divided data as header addition by protocol conversion, and further adds a control header to the leading divided data and single divided data (single divided data) in the divided data group. Add to generate a new protocol packet. Note that the divided data group is a plurality of consecutive divided data on the same connection.

In the example of FIG. 7, the divided data d1 and d2 are included in the divided data group, and the divided data d1 is the leading divided data. Also, the divided data d11 and d12 are included in the divided data group, and the divided data d11 is the leading divided data. The divided data d3 and the divided data d13 are discontinuous and single divided data.

In the communication protocol header and control header added by protocol conversion, the communication protocol header includes at least a sequence number, and the control header includes at least a connection identifier and data length (data length information).

[Step S41] The communication device 10a adds the communication protocol header Hp1 and the control header Hc1 to the divided data d1 to generate the packet P1, and stores the packet P1 in the transmission buffer (referred to as the transmission buffer 12a1).

The communication protocol header Hp1 contains a sequence number (seq=0), and the control header Hc1 contains a connection identifier (Con1) and a data length (Len=X2).
[Step S42] The communication device 10a adds the communication protocol header Hp2 to the divided data d2 to generate the packet P2, and stores the packet P2 in the transmission buffer 12a1. The communication protocol header Hp2 contains a sequence number (seq=X1+h). h is the data length of the control header.

[Step S43] The communication device 10a adds the communication protocol header Hp3 and the control header Hc2 to the divided data d11 to generate the packet P3, and stores the packet P3 in the transmission buffer 12a1.

The communication protocol header Hp3 contains a sequence number (seq=X2+h), and the control header Hc2 contains a connection identifier (Con2) and data length (Len=Y2).
[Step S44] The communication device 10a adds a communication protocol header Hp4 to the divided data d12 to generate a packet P4, and stores the packet P4 in the transmission buffer 12a1. The communication protocol header Hp4 contains a sequence number (seq=X2+Y1+2h).

[Step S45] The communication device 10a adds the communication protocol header Hp5 and the control header Hc3 to the divided data d3 to generate the packet P5, and stores the packet P5 in the transmission buffer 12a1.

The communication protocol header Hp5 contains a sequence number (seq=X2+Y2+2h), and the control header Hc3 contains a connection identifier (Con1) and data length (Len=XX2).

[Step S46] The communication device 10a adds the communication protocol header Hp6 and the control header Hc4 to the divided data d13 to generate the packet P6, and stores the packet P6 in the transmission buffer 12a1.

The communication protocol header Hp6 contains a sequence number (seq=X+Y2+3h), and the control header Hc4 contains a connection identifier (Con2) and data length (Len=Y−Y2).

As for the data length set in the control header, the length of continuous data is set in the control header of the top divided data for the divided data group. For example, packets P1 and P2 are divided data groups, and the data length of packet P1=X1 and the data length of packet P2=X2-X1. Therefore, X2 (=X1+(X2-X1)) is set as the data length in the control header Hc1 of the packet P1 having the leading split data.

Also, the data length of the single segmented data is set in the control header of the packet having the single segmented data. For example, since packet P5 includes single segmented data and has a data length of XX2, XX2 is set as the data length in the control header Hc3 of packet P5.

On the other hand, regarding the sequence numbers, when packets P1, P2, . It is the sum of the sum of the lengths and the sum of the lengths of the control headers included in the packets P1, . . . , Pk-1.

For example, packets P1 and P2 have already been received for the sequence number of packet P3. Therefore, from the data length of packet P1=X1 and the data length of packet P2=X2-X1, the sum of the data lengths is X2.

Also, since the packets P1 and P2 have one control header Hc1, the sum of the lengths of the control headers is h. Therefore, the sequence number of packet P3 is seq=X2+h. Sequence numbers of other packets are similarly set.

FIG. 8 is a diagram showing an example of protocol conversion in chronological order. 8 shows the flow of adding headers after the generation of divided data shown in FIG. 7;
[Time t0-t1] The communication device 10a receives the divided data group including the divided data d1 and d2. The data length of the divided data group is X2. The communication device 10a performs protocol conversion on the divided data d1 to generate packets P1.

Since the divided data d1 is the leading divided data in the divided data group in which two divided data are continuous, the control header (Hc1 ) is given.

Further, the communication device 10a converts the protocol of the divided data d2 to generate a packet P2. A communication protocol header (Hp2) is added to the divided data d2.
[Time t1-t2] The communication device 10a receives the divided data group including the divided data d11 and d12. The data length of the divided data group is Y2. The communication device 10a protocol-converts the divided data d11 to generate a packet P3.

Since the divided data d11 is the leading divided data in the divided data group in which two divided data are continuous, the control header (Hc2 ) is given.

The communication device 10a also converts the protocol of the divided data d12 to generate a packet P4. A communication protocol header (Hp4) is added to the divided data d12.
[Time t2-t3] The communication device 10a receives the divided data d3. The data length of the divided data d3 is XX2. The communication device 10a performs protocol conversion on the divided data d3 to generate a packet P5.

Since the divided data d3 is single divided data, in addition to the communication protocol header (Hp5), a control header (Hc3) including information on the data length of the divided data d3=XX2 is added.

[Time t3-t4] The communication device 10a receives the divided data d13. The data length of the divided data d13 is YY2. The communication device 10a protocol-converts the divided data d13 to generate a packet P6.

Since the divided data d13 is single divided data, in addition to the communication protocol header (Hp6), a control header (Hc4) containing information on the data length of the divided data d13=Y−Y2 is added.

<Operation when data is sent from the opposite device to the destination>
FIG. 9 is a diagram showing an example of operation when data is transmitted from the opposite device to the destination.
[Step S51] The communication device 10a transmits the packet stored in the transmission buffer 12a1 to the opposite communication device 10c. In this case, the communication device 10a detects a packet having continuous data based on the data length included in the control header, extracts the packet from the transmission buffer 12a1, and transmits it to the communication device 10c.

For example, from FIG. 7, packet P1 has a control header Hc1 with a data length of X2, and it is detected that packets P1 and P2 constitute continuous data. Therefore, if the packets P1 and P2 are in the transmission buffer 12a1, the packets P1 and P2 are transmitted to the communication device 10c as continuous data.

[Step S52] The communication device 10c stores the packet transmitted from the communication device 10a in the reception buffer (reception buffer 12b3).
[Step S53] The communication device 10c extracts the packets from the reception buffer 12b3 in the order in which they are received, deletes the header added during protocol conversion from the extracted packets, and transmits the divided data to the destination server. In this case, if there is continuous data (divided data group), the continuous data is extracted collectively and transmitted to the server.

In this example, since the packets P1 and P2 are continuous data, the packets P1 and P2 are extracted from the reception buffer 12b3, and the divided data d1 and d2 after removing the headers are transmitted to the server 31. FIG.

[Step S54] The communication device 10c deletes the packet that has been transmitted to the server from the reception buffer 12b3. In this example, packets P1 and P2 are deleted from the reception buffer 12b3.

[Step S55] The communication device 10c transmits continuously received packet information and packet loss information when a packet loss is detected to the active communication device 10a.
The continuously received packet information is information indicating the last packet among the packets continuously received by the communication device 10c from the communication device 10a. In this example, since packets P1, P2, and P3 have been consecutively received, the sequence number (seq=X2+h) corresponding to the last packet P3 is the consecutively received packet information.

Also, the packet loss information is information indicating lost packets. In this example, since packet P4 is lost, the sequence number (seq=X2+Y1+2h) corresponding to packet P4 is the packet loss information.

[Step S56] The communication device 10a deletes the packets stored in the transmission buffer 12a1 based on the continuously received packet information. In this example, packets P1, P2, and P3 are deleted from the transmission buffer 12a1. Further, the communication device 10a retransmits the lost packet (packet P4 in this example) based on the packet loss information.

[Step S57] The communication device 10c transmits response information indicating how much data has been transmitted to the server over the connection to the standby communication device 10b. In this example, continuous data packets P1 and P2 are transmitted over connection Con1. Therefore, the communication device 10c transmits the connection identifier Con1 and the continuous data length X2 as response information to the communication device 10b.

[Step S58] Based on the response information, the communication device 10b deletes the data transmitted to the server from the data storage section 12c2. In this example, it can be detected that data with a data length up to X2 has been transmitted to the server 31 via the connection Con1, so the communication device 10b deletes the data d1 and d2 from the data storage unit 12c2.

Here, packet loss detection control will be described. Which packet is lost can be detected from the sequence number and control header. A packet P3 having a control header Hc2 in which a data length (Len=Y2) is set is stored in the reception buffer 12b3 of the communication device 10c. Therefore, of the data transmitted through connection Con2, data up to data length=Y1 has already been received.

Also, since the sequence number of packet P3 is X2+h, the sequence number of the packet to be received next (packet P4) is X2+h, the data length of packet P3 is Y1, and the length of the control header Hc2 of packet P3 is h. should be received with a communication protocol header of X2+Y1+2h.

However, the communication device 10c has not received a packet with this sequence number, and has received a packet P5 to which a new control header Hc3 has been added after receiving the packet P3. Therefore, it is detected that a packet (packet P4) following packet P3 is lost.

Among the data transmitted through the connection Con1, the packet P5 having a data length of XX2 has already been received, and there is no other packet containing a control header related to the connection Con1. Therefore, it is determined that there is no packet in the connection Con1 that has been transmitted by the communication device 10a but has not been received by the communication device 10c.

Packet loss detection control will be further described. The sequence number included in the communication protocol header Hp3 attached to the divided data d11 in the packet P3 is X2+h. The communication device 10c adds the data length=Y1 of the divided data d11 and the length (h) of the control header Hc2 attached to the divided data d11 to this sequence number to calculate the sequence number (X2+Y1+2h). .

Further, the communication device 10c calculates the data length=Y2−Y1 by subtracting the data length=Y1 of the divided data d11 from the data length information (Y2) included in the control header Hc2.
Then, assume that the communication device 10c detects that there is no sequence number (X2+Y1+2h) among the sequence numbers assigned to the received packet. In this case, the communication device 10c detects the packet (packet P4) including the divided data (divided data d12) having the sequence number (X2+Y1+2h) and the data length=Y2−Y1 as an unreceived packet.

Thus, the communication device 10c can efficiently and accurately detect lost packets based on the communication protocol header including the sequence number and the control header including the connection identifier and data length information.

<Operation when failure of active communication device is detected>
FIG. 10 is a diagram showing an example of the operation when a failure of the active communication device is detected.
[Step S61] The communication device 10b detects a failure of the communication device 10a. Note that failure detection is performed by both the communication devices 10a and 10b. Further, as the failure detection means, for example, failure detection can be performed based on keep alive packets that are periodically transmitted.

[Step S62] When the communication device 10b detects a failure of the communication device 10a, it switches from the standby system to the active system. Further, the communication device 10b transmits to the communication device 10c system switching information indicating that the communication device 10b itself has switched to the active system instead of the communication device 10a. Note that the system switching information is transmitted to the communication device 10c via the router 51, the WAN 6, and the router 52 shown in FIG.

<Operation after the standby communication device is switched to the active system>
FIG. 11 is a diagram showing an example of the operation after the standby communication device is switched to the active communication device.
[Step S71] The communication device 10b, which has switched to the active system, transmits to the communication device 10c an inquiry request for unreceived divided data as to whether or not there is unreceived divided data.

[Step S72] When detecting an unreceived packet from the storage state of the reception buffer 12b3, the communication device 10c generates non-reception detection information 7 and transmits the non-reception detection information 7 to the communication device 10b.

Note that the communication device 10c has not yet received the packet P4. In this case, the communication device 10c generates non-reception detection information 7 including connection identifier=Con2, division start position=Y1, and data length=Y2-Y1, and transmits it to the communication device 10b.

[Step S73] Based on the non-reception detection information 7, the communication device 10b detects that the data d12 has not been received by the communication device 10c.
[Step S74] The communication device 10b extracts the data d12 from the data storage section 12b2 and transmits it to the communication device 10c.

Here, the non-receipt detection information 7 will be explained. Packet P3 has been received by communication device 10c. The control header Hc2 of the packet P3 includes the connection identifier Con2 and the data length=Y2, and the packet P3 includes the data d11 with the data length=Y1.

Since it is detected that the packet P4 is lost, the communication device 10c detects the data on the connection Con2, which starts from Y1 and has a data length of Y2-Y1. Data can be detected as not received.

Therefore, the communication device 10c can generate the non-receipt detection information 7 including connection identifier=Con2, division start position=Y1, and data length=Y2-Y1. When the communication device 10b receives such non-reception detection information 7, the communication device 10b can accurately detect non-reception data from the data stored in the data storage unit 12c2.

<Operation sequence>
Next, the operation described above will be further described with reference to the sequence diagrams of FIGS. 12 to 15. FIG.

FIG. 12 is a diagram showing an example of an operation sequence when accepting a new connection.
[Step S101] A three-way handshake is performed between the client terminal 21 and the communication device 10a. That is, the client terminal 21 transmits a SYN packet (connection request) to the communication device 10a. The communication device 10 a returns a SYN+ACK packet (connection permission) to the client terminal 21 . The client terminal 21 transmits an ACK packet (connection start) to the communication device 10a.

[Step S102] The communication device 10a stores the connection information in the data storage section 12c1.
[Step S103] The communication device 10a transmits a new connection establishment request together with the connection information to the communication device 10c.

[Step S104] The communication device 10c stores the received connection information in the data storage section 12c3.
[Step S105] A three-way handshake is performed between the communication device 10c and the server 31. FIG. That is, the communication device 10 c transmits the SYN packet to the server 31 . The server 31 returns a SYN+ACK packet to the communication device 10c. The communication device 10 c transmits the ACK packet to the server 31 .

[Step S106] The communication device 10c transmits a connection establishment notification to the communication device 10a indicating that a new connection has been established.
[Step S107] The communication device 10a transmits connection information to the communication device 10b.

[Step S108] The communication device 10b stores the received connection information in the data storage section 12c2.
FIG. 13 is a diagram showing an example of an operation sequence for receiving transmission data from a client terminal and protocol conversion.

[Step S110] Data of data length=X2 originating from the client terminal 21 is transmitted to the communication devices 10a and 10b.
[Step S111a] The communication device 10a stores the received data in the data storage section 12c1.

[Step S111b] The communication device 10b stores the received data in the data storage section 12c2.
[Step S112] The communication device 10a performs protocol conversion on the stored data (data length=X1, divides into X2-X1 and adds headers), and stores the protocol-converted packet in the transmission buffer 12a1.

[Step S113] The communication device 10a transmits the data (packets P1 and P2) to the communication device 10c.
[Step S114] The data of data length=Y2 originating from the client terminal 22 is transmitted to the communication devices 10a and 10b.

[Step S115a] The communication device 10a stores the received data in the data storage section 12c1.
[Step S115b] The communication device 10b stores the received data in the data storage section 12c2.

[Step S116] The communication device 10a performs protocol conversion on the stored data (data length=Y1, divides into Y2-Y1 and adds headers), and stores the packet after protocol conversion in the transmission buffer 12a1.

[Step S117] The communication device 10a transmits the data (packets P3 and P4) to the communication device 10c.
[Step S118] The data of data length=XX2 whose transmission source is the client terminal 21 is transmitted to the communication devices 10a and 10b.

[Step S119a] The communication device 10a stores the received data in the data storage section 12c1.
[Step S119b] The communication device 10b stores the received data in the data storage section 12c2.

[Step S120] The communication device 10a performs protocol conversion (adding a header) to the stored data, and stores the protocol-converted packet in the transmission buffer 12a1.
[Step S121] The communication device 10a transmits data (packet P5) to the communication device 10c.

FIG. 14 is a diagram showing an example of an operation sequence when data is transmitted from the counterpart device to the destination.
[Step S130] Data is transmitted from the communication device 10a to the communication device 10c.

[Step S131] The communication device 10c stores the received data in the reception buffer 12b3.
[Step S132a] When a plurality of pieces of data having the data length indicated by the control header are continuously stored in the reception buffer 12b3, the communication device 10c deletes the header added during protocol conversion and sends the data to the server. 31.

[Step S132b] The communication device 10c deletes the transmitted data from the reception buffer 12b3.
[Step S133a] As an acknowledgment, the communication device 10c transmits, to the communication device 10a, the continuously received packet information and the packet loss information when a packet loss is detected. It should be noted that the operation after step S133a is performed when a certain period of time has passed since the previous confirmation response.

[Step S133b] Based on the continuously received packet information, the communication device 10a deletes the packets that have been completely received by the communication device 10c from the transmission buffer 12a1.
[Step S133c] The communication device 10c transmits response information indicating the data transmitted to the server 31 to the communication device 10b.

[Step S133d] Based on the response information, the communication device 10b deletes the packet that has been transmitted from the communication device 10c from the data storage unit 12c2.
FIG. 15 is a diagram showing an example of an operation sequence when a failure of the active communication device is detected.

[Step S140] Keep alive packets are exchanged between the communication devices 10a and 10b.
[Step S141] The communication device 10a fails and stops operating.

[Step S142] The communication device 10b continues transmitting keep alive packets to the communication device 10a.
[Step S143] If the communication device 10b cannot receive a reply even after transmitting the keep alive packet to the communication device 10a a predetermined number of times, it detects a failure of the communication device 10a and switches to the active system.

[Step S144] The communication device 10b transmits to the communication device 10c system switching information indicating that the communication device 10b itself has been switched to the active system.
The processing functions of the communication device 1 and the communication device 10 of the present invention described above can be realized by a computer. In this case, a program describing the processing contents of the functions that the communication device 1 and the communication device 10 should have is provided. By executing the program on a computer, the above processing functions are realized on the computer.

A program describing the processing content can be recorded in a computer-readable recording medium. Computer-readable recording media include magnetic storage devices, optical disks, magneto-optical recording media, semiconductor memories, and the like. Magnetic storage devices include hard disk devices (HDD), flexible disks (FD), magnetic tapes, and the like. Optical discs include DVD, DVD-RAM, CD-ROM/RW, and the like. Magneto-optical recording media include MO (Magneto Optical disk) and the like.

When distributing a program, for example, portable recording media such as DVDs and CD-ROMs on which the program is recorded are sold. It is also possible to store the program in the storage device of the server computer and transfer the program from the server computer to another computer via the network.

A computer that executes a program stores, for example, a program recorded on a portable recording medium or a program transferred from a server computer in its own storage device. The computer then reads the program from its own storage device and executes processing according to the program. The computer can also read the program directly from the portable recording medium and execute processing according to the program.

In addition, the computer can also execute processing according to the received program every time the program is transferred from a server computer connected via a network. At least part of the processing functions described above can also be realized by electronic circuits such as DSPs, ASICs, and PLDs.

Although the embodiment has been exemplified above, the configuration of each part shown in the embodiment can be replaced with another one having the same function. Also, any other components or steps may be added. Furthermore, any two or more configurations (features) of the above-described embodiments may be combined.

1, 1-1, 1-2, 1-3 communication device 1a, 1a1, 1a2, 1a3 control unit 1b, 1b1, 1b2, 1b3 storage unit 2 client terminal 3 server Cs1 communication system

Claims (6)

a storage unit for storing received data;
When functioning as the first active system, the data is divided to generate divided data, a header is added to each of the divided data, protocol conversion is performed to generate a plurality of packets, and the generated packets are sent to each other. When it is transmitted to the device and functions as a standby system, the operation of the first active system is monitored, and when the stop of the first active system is detected, the switch to the second active system is detected. Notifying the opposite device, extracting the unreceived divided data contained in the unreceived packet from the data stored in the storage unit based on the non-receipt detection information transmitted from the opposite device, and extracting the unreceived packet a control unit that transmits divided data to the opposed device;
A communication device having a The control unit, as the header,
giving a first header including a sequence number to all of the divided data;
A second header including an identifier of a connection through which the divided data group is transmitted and data length information of the divided data group is added to the head divided data of the divided data group including the plurality of continuous divided data. death,
2. The communication apparatus according to claim 1, wherein the discontinuous single data segment is further provided with a third header including an identifier of a connection through which said single data segment is transmitted and data length information of said single data segment. The control unit
The first sequence number included in the first header attached to the first divided data in the received first packet includes the first data length of the first divided data and the first sequence number. calculating a second sequence number by adding the length of the second header or the third header attached to the divided data of
calculating a second data length by subtracting the first data length from the data length information included in the second header or the third header;
When the second sequence number among the sequence numbers assigned to the received packet is not detected, second divided data to which the second sequence number is assigned and which has the second data length. 3. The communication device according to claim 2, wherein a second packet containing is detected as the unreceived packet. When detecting the unreceived packet, the control unit includes at least an identifier of a connection through which the unreceived packet is transmitted, a division start position of the unreceived divided data, and a data length of the unreceived divided data. 2. The communication device according to claim 1, wherein said non-reception detection information is generated. the computer
When functioning as the first active system, the received data is divided to generate divided data, a header is added to each of the divided data, protocol conversion is performed to generate a plurality of packets, and the generated packets are generated. Send to the opposite device,
When functioning as a standby system, the operation of the first active system is monitored, and when the stop of the first active system is detected, the opposite device is notified of the switching to the second active system. extracting unreceived divided data included in the unreceived packet from the data stored in the storage unit based on the unreceived detection information transmitted from the counterpart device, and transmitting the extracted unreceived divided data to the counterpart device; send to
A communication control method that performs processing. to the computer,
When functioning as the first active system, the received data is divided to generate divided data, a header is added to each of the divided data, protocol conversion is performed to generate a plurality of packets, and the generated packets are generated. Send to the opposite device,
When functioning as a standby system, the operation of the first active system is monitored, and when the stop of the first active system is detected, the opposite device is notified of the switching to the second active system. extracting unreceived divided data included in the unreceived packet from the data stored in the storage unit based on the unreceived detection information transmitted from the counterpart device, and transmitting the extracted unreceived divided data to the counterpart device; send to
A program that causes an action to take place.

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