JP2017034627A - System and method for communication control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a decreased number of connections per unit time caused by the retransmission of a SYN packet.SOLUTION: A communication control system includes a receiver unit, a packet identification unit, a transmitter unit and a buffer management unit. The communication control system controls communication between an information processing device and a server to establish a connection in a network using TCP (Transmission Control Protocol). The receiver unit receives a packet exchanged between the information processing device and the server. The packet identification unit distributes, to each buffer, SYN (Synchronization) packets, transmitted from the information processing device to the server, among received packets. The transmitter unit transmits the SYN packet stored in the buffer to the server at a predetermined transmission rate. When the received packet satisfies a predetermined condition, the buffer management unit discards the SYN packet which is stored in the buffer or a received packet.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication control system and a communication control method.

  Information communication using TCP (Transmission Control Protocol) is widely used. When communication is performed between a user terminal and an application (APL) server using TCP, a process called a three-way handshake is usually executed. In the three-way handshake, first, one information processing apparatus transmits a SYN (Synchronization) packet requesting establishment of a communication connection (connection) to the other information processing apparatus. The other information processing apparatus transmits a SYN-ACK (Acknowledgement) packet to permit connection in accordance with the SYN packet. One information processing apparatus that has received the SYN-ACK packet transmits an ACK packet indicating the start of connection. This starts communication using TCP.

Akihiro Kimura, Atsushi Nishiyama, Ken Osaka, Ichiro Kudo, “Proposal of NW function to reduce the number of servers for IoT service provision”, IEICE Technical Report, pp. 379-384 V. Paxson, M. Allman, J. Chu & M. Sargent, “Computing TCP ’s Retransmission Timer”, Internet Engineering Task Force (IETF), 2011

  By the way, when the transmission source of the SYN packet requesting establishment of the connection does not receive the SYN-ACK packet responding to the SYN packet for a predetermined period, the SYN packet is retransmitted. The transmission source retransmits the SYN packet repeatedly at a predetermined interval until it receives a SYN-ACK packet or retransmits it a predetermined number of times.

  When a SYN packet is repeatedly retransmitted from a plurality of user terminals to an APL server that performs communication with a plurality of user terminals, the ratio of the retransmitted packets in the transmitted packets increases. In such a case, the number of connections per unit time that the APL server can establish with the user terminal may decrease.

  An embodiment of the disclosure has been made in view of the above, and an object thereof is to provide a communication control system and a communication control method capable of suppressing a decrease in the number of connections per unit time due to retransmission of a SYN packet. To do.

  The disclosed communication control system and communication control method control communication between an information processing apparatus and a server that establish a connection using TCP on a network. The receiving unit receives a packet transmitted / received between the information processing apparatus and the server. The packet identification unit distributes SYN packets transmitted from the information processing apparatus to the server among the received packets. The transmission unit transmits the SYN packet stored in the buffer to the server at a predetermined transmission rate. The buffer management unit discards the SYN packet or the received packet stored in the buffer when the received packet satisfies a predetermined condition.

  The communication control system and the communication control method disclosed have an effect of suppressing a decrease in the number of connections per unit time due to retransmission of SYN packets.

FIG. 1 is a diagram illustrating an example of a configuration of a communication control system according to the first embodiment. FIG. 2 is a diagram illustrating an example of the configuration of the communication control apparatus according to the first embodiment. FIG. 3 is a flowchart illustrating an example of a process flow in the communication control system according to the first embodiment. FIG. 4 is a diagram illustrating an example of the configuration of the communication control apparatus according to the second embodiment. FIG. 5 is a flowchart illustrating an example of a process flow in the communication control system according to the second embodiment. FIG. 6 is a diagram illustrating an example of the configuration of the communication control apparatus according to the third embodiment. FIG. 7 is a flowchart illustrating an example of a process flow in the communication control system according to the third embodiment. FIG. 8 is a diagram illustrating an example of the configuration of the communication control apparatus according to the fourth embodiment. FIG. 9 is a flowchart illustrating an example of a processing flow in the communication control system according to the fourth embodiment. FIG. 10 is a diagram for explaining a retransmission interval of a SYN packet, which is a premise of the communication control process according to the fifth embodiment. FIG. 11 is a diagram illustrating an example of a configuration of a communication control apparatus according to the fifth embodiment. FIG. 12 is a flowchart illustrating an example of a process flow in the communication control system according to the fifth embodiment. FIG. 13 is a diagram illustrating an example of the configuration of the communication control apparatus according to the sixth embodiment. FIG. 14 is a flowchart illustrating an example of a processing flow in the communication control system according to the sixth embodiment. FIG. 15 is a diagram for explaining a technique for predicting the timing at which the reception rate exceeds the threshold in the communication control process according to the sixth embodiment. FIG. 16 is a diagram for explaining a method for setting a threshold in the communication control process according to the sixth embodiment. FIG. 17 is a diagram for explaining an example in which the function of the communication control device according to each embodiment is mounted on a plurality of devices. FIG. 18 is a diagram for explaining an example of processing when a SYN packet is transmitted from the user terminal to the APL server. FIG. 19 is a diagram for explaining an example of processing when a SYN packet is retransmitted from the user terminal to the APL server. FIG. 20 is a diagram illustrating a computer that executes a communication control program.

  In the following, embodiments of the disclosed system and method will be described in detail based on the drawings. In addition, this invention is not limited by this embodiment. Moreover, each embodiment can be combined suitably.

(An example of SYN packet retransmission processing by an existing method)
First, with reference to FIG. 18 and FIG. 19, a connection establishment process using the conventional TCP will be described as a premise of the communication control system and the communication control method according to the embodiment. FIG. 18 is a diagram for explaining an example of processing when a SYN packet is transmitted from the user terminal to the APL server. FIG. 19 is a diagram for explaining an example of processing when a SYN packet is retransmitted from the user terminal to the APL server.

  In the example of FIG. 18, user terminals 1 to 4 are connected to the APL server 5 via the network A. Further, a transfer device 6, a buffer 7 and a transmission rate control device 8 are connected between the user terminals 1 to 4 and the APL server 5.

  When each of the user terminals 1 to 4 starts communication with the APL server 5 via the network A, it first transmits a SYN packet to establish a connection. The APL server 5 sends back an ACK packet as a response confirmation for the SYN packet. When receiving the ACK packet, the user terminals 1 to 4 consider that the connection has been established, and transmit the ACK packet to the APL server 5 as a response to the received ACK packet. In addition, the user terminals 1 to 4 transmit APL layer packets to the APL server 5. In FIG. 18, the SYN packet transmitted from the user terminal n is displayed as SYN (n). An ACK packet transmitted by user terminal n is displayed as ACK (n). The APL layer packet transmitted by the user terminal n is displayed as APL (n).

  A sequence number is assigned to each transmitted SYN packet. For example, the sequence number “1” is assigned to the SYN packet transmitted by the user terminal 1. The sequence number of the ACK packet, which is an acknowledgment transmitted by the APL server 5 in response to the SYN packet with the sequence number “1”, is also “1”.

  The transfer device 6 receives packets transmitted from the user terminals 1 to 4, extracts SYN packets, and stores them in the buffer 7. The transfer device 6 transmits packets other than the SYN packet, for example, APL layer packets and ACK packets to the APL server 5 without storing them in the buffer 7.

  The buffer 7 is a FIFO (First In First Out) memory. The SYN packet stored in the buffer 7 is transmitted from the buffer 7 to the APL server 5 by the transmission rate control device 8 at a predetermined transmission rate.

  If the user terminals 1 to 4 do not receive an ACK packet in response to the SYN packet even after a predetermined time has elapsed after transmitting the SYN packet, the user terminals 1 to 4 retransmit the SYN packet. The initial value of the retransmission interval for retransmitting a SYN packet in TCP is determined depending on the implementation of each user terminal. For example, it is 3 seconds for a Windows (registered trademark) operating system (OS) and 1 second for a Linux (registered trademark) OS. The second and subsequent retransmission intervals are set according to a TCP retransmission algorithm defined in RFC (Request for Comments). The second and subsequent retransmission intervals are set to, for example, twice the previous retransmission interval. The transfer device 6 distributes all of the initial SYN packets and retransmission packets to the buffer 7 without distinguishing them.

  When the APL server 5 receives the SYN packet, if the number of established connections has not reached the predetermined upper limit, the APL server 5 secures resources for APL layer packet processing and transmits an ACK packet. When the number of established connections reaches a predetermined upper limit, the APL server 5 discards the SYN packet and does not transmit an ACK packet.

  In the example of FIG. 19, the user terminal 2 transmits a SYN packet (SYN (2)), but does not reach the APL server 5. Since the user terminal 2 has not received the ACK packet in response to the SYN packet (SYN (2)), the user terminal 2 retransmits the SYN packet when a predetermined time has elapsed. The retransmitted SYN packet is distributed to the buffer 7 by the transfer device 6. The SYN packet distributed to the buffer 7 is transmitted to the APL server 5 at a predetermined transmission rate under the control of the transmission rate control device 8. For this reason, when a SYN packet is transmitted from each of the user terminals 1 to 4 at the same timing, a user terminal that does not receive an ACK packet responding from the APL server 5 appears within a predetermined time. Since the transmission rate from the buffer 7 is constant, the ratio of the SYN packet retransmitted from the user terminal that has not received the ACK packet to the SYN packet in the buffer 7 increases. As a result, the number of SYN packets for the first transmission received by the APL server 5 per unit time decreases.

  The APL server 5 checks the sequence number of the received SYN packet. If the ACK packet having the same sequence number has already been transmitted, the APL server 5 discards the received SYN packet. When the ratio of retransmission packets in the SYN packets received by the APL server 5 increases, the number of connections established between the user terminals 1 to 4 and the APL server 5 established per unit time decreases.

(First embodiment)
FIG. 1 is a diagram illustrating an example of a configuration of a communication control system according to the first embodiment. In the communication control system 1A according to the first embodiment, the communication control apparatus 10 is connected to the information processing apparatuses 20A, 20B, 20C, and 20D and the gateway 30 via the network 40. The information processing devices 20B, 20C, and 20D are connected to the communication control device 10 via the gateway 30 and the network 40. The communication control apparatus 10 is connected to the server 50 via the network 60. The configuration illustrated in FIG. 1 is merely an example, and the communication control device 10 may be disposed on a network that connects the information processing devices 20A, 20B, 20C, and 20D and the server 50. The number of each device is not particularly limited.

  The information processing apparatuses 20A, 20B, 20C, and 20D transmit and receive information to and from the server 50 via the networks 40 and 60. The information processing apparatuses 20A, 20B, 20C, and 20D are, for example, IoT (Internet of Things) terminals or M2M (Machine to Machine) terminals.

  The gateway 30 connects the network 40 to another network. The gateway 30 is, for example, an IoT gateway, an M2M gateway, or the like.

  The networks 40 and 60 are, for example, the Internet, an intranet, a local area network (LAN), a wide area network (WAN), and the like. The networks 40 and 60 may be wireless networks, wired networks, or a combination of both.

  The server 50 establishes a connection with the information processing apparatuses 20A, 20B, 20C, and 20D, and transmits and receives information. Server 50 is, for example, an APL server.

(Example of configuration of communication control device)
FIG. 2 is a diagram illustrating an example of the configuration of the communication control apparatus according to the first embodiment. As illustrated in FIG. 1, the communication control device 10 is disposed on a communication path between the information processing devices 20A, 20B, 20C, and 20D and the server 50. The communication control device 10 controls communication between the information processing devices 20A, 20B, 20C, and 20D and the server 50. For example, the communication control device 10 transfers a SYN packet transmitted from the information processing devices 20A, 20B, 20C, and 20D to the server 50. Further, the communication control device 10 reduces the number of connections per unit time between the server 50 and the information processing devices 20A, 20B, 20C, and 20D by the SYN packet retransmitted from the information processing devices 20A, 20B, 20C, and 20D. Control communications to suppress.

  As illustrated in FIG. 2, the communication control apparatus 10 includes a communication unit 110, a control unit 120, and a storage unit 130.

  The communication unit 110 transmits and receives information transmitted via the networks 40 and 60.

  The control unit 120 controls processing of each unit of the communication control device 10. The control unit 120 can be configured by, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), an ASIC (Application Specific Integrated Circuit), or the like. The control unit 120 includes a packet identification unit 121 and a buffer management unit 122.

  The packet identification unit 121 identifies the type of packet received via the communication unit 110. The packet identification unit 121 identifies a SYN packet transmitted from the information processing apparatuses 20A, 20B, 20C, and 20D to the server 50. Then, the packet identification unit 121 stores the identified SYN packet in a buffer 131 described later. Further, the packet identification unit 121 transmits a packet other than the SYN packet to the destination via the communication unit 110. The packet identification unit 121 identifies the information processing apparatuses 20A to 20D and the server 50 from the transmission source IP address, the transmission destination IP address, and the like. The packet identification unit 121 identifies a SYN packet based on the SYN flag in the TCP header of the packet.

  When a packet received via the communication unit 110 satisfies a predetermined condition, the buffer management unit 122 discards a part or all of the SYN packet stored in the buffer 131 or the received packet.

  The buffer management unit 122 also transmits the SYN packet stored in the buffer 131 to the server 50 via the communication unit 110 at a predetermined transmission rate.

  The storage unit 130 stores information used for processing of each unit in the communication control device 10 and information generated as a result of the processing. The storage unit 130 may be a storage device such as a hard disk or an optical disk. The storage unit 130 may be a semiconductor memory such as a RAM (Random Access Memory) or a flash memory. The storage unit 130 has a buffer 131.

  The buffer 131 stores the SYN packet identified by the packet identification unit 121. For example, the buffer 131 is a FIFO (First In First Out) memory. The buffer 131 stores the SYN packets identified by the packet identification unit 121 in the order received. The stored SYN packet is transmitted to the server 50 via the communication unit 110 at a predetermined transmission rate in order from the previously stored packet.

(Example of flow of communication control process of first embodiment)
FIG. 3 is a flowchart illustrating an example of a process flow in the communication control system according to the first embodiment. As shown in FIG. 3, the communication unit 110 of the communication control apparatus 10 receives a packet (step S31). The packet identification unit 121 identifies a SYN packet addressed to the server 50 from the information processing apparatuses 20A, 20B, 20C, and 20D from the received packets. Then, the packet identification unit 121 distributes the identified SYN packet to the buffer 131 (step S32). The buffer management unit 122 determines whether or not the packet received by the communication unit 110 satisfies a predetermined condition (step S33). When it is determined that the received packet satisfies the predetermined condition (Yes at Step S33), the buffer management unit 122 discards a part or all of the SYN packet in the buffer 131 or the received packet (Step S34). On the other hand, when it is determined that the received packet does not satisfy the predetermined condition (No in step S33), the buffer management unit 122 proceeds to the next process. Then, the buffer management unit 122 transmits the SYN packet in the buffer 131 to the server 50 at a predetermined transmission rate (step S35). This completes the communication control process according to the first embodiment.

(Effects of the first embodiment)
The communication control system according to the first embodiment controls communication between an information processing apparatus and a server that establish a connection using TCP on a network. The receiving unit (communication unit) receives a packet transmitted and received between the information processing apparatus and the server. The packet identification unit distributes the SYN packet transmitted from the information processing apparatus to the server among the packets received by the reception unit. The transmission unit (communication unit) transmits the SYN packet stored in the buffer to the server at a predetermined transmission rate. The buffer management unit discards the SYN packet stored in the buffer or the received packet when the packet received by the receiving unit satisfies a predetermined condition. For this reason, when receiving a packet that satisfies a predetermined condition, the communication control system does not transmit all SYN packets transmitted from the information processing apparatus to the server, but reduces the SYN packets to be transmitted. Therefore, all of the retransmission packets are not transmitted to the server, and a decrease in the number of connections that can be established per unit time can be suppressed.

(Second Embodiment)
In the first embodiment, the communication control apparatus 10 discards the SYN packet stored in the buffer or the received packet when the received packet satisfies a predetermined condition. The communication control system according to the second embodiment discards the received SYN packet when the SYN packet having the same sequence number as the sequence number of the received SYN packet is already stored in the buffer.

  FIG. 4 is a diagram illustrating an example of the configuration of the communication control apparatus according to the second embodiment. The communication control apparatus 10A according to the second embodiment includes a communication unit 110A, a control unit 120A, and a storage unit 130A. The function and configuration of the communication unit 110A are the same as those in the first embodiment.

  The control unit 120A includes a packet identification unit 121A and a buffer management unit 122A.

  The storage unit 130A includes a buffer 131A. The configurations and functions of the storage unit 130A and the buffer 131A are the same as those in the first embodiment. However, the SYN packet stored in the buffer 131A is managed by the buffer management unit 122A.

  The packet identification unit 121A identifies the SYN packet addressed to the server 50 from the information processing devices 20A, 20B, 20C, and 20D from the packets received by the communication unit 110A. Then, the packet identification unit 121A passes the identified SYN packet to the buffer management unit 122A.

  The buffer management unit 122A extracts the sequence number of the SYN packet before storing the SYN packet identified by the packet identification unit 121A in the buffer 131A. Then, the buffer management unit 122A determines whether the SYN packet having the same sequence number is stored in the buffer 131A. If it is determined that a SYN packet with the same sequence number is stored in the buffer 131A, the buffer management unit 122A discards the received SYN packet without storing it in the buffer 131A. On the other hand, when it is determined that the SYN packet having the same sequence number is not stored in the buffer 131A, the buffer management unit 122A stores the SYN packet in the buffer 131A. Then, the buffer management unit 122A sequentially transmits the SYN packets stored in the buffer 131A to the server 50 at a predetermined transmission rate.

(Example of flow of communication control processing according to second embodiment)
FIG. 5 is a flowchart illustrating an example of a process flow in the communication control system according to the second embodiment. First, the communication unit 110A receives a packet (step S51). Then, the packet identification unit 121A determines whether or not the received packet is a SYN packet (step S52). If it is determined that the received packet is a SYN packet (step S52, Yes), the packet identification unit 121A passes the SYN packet to the buffer management unit 122A. The buffer management unit 122A extracts the sequence number of the SYN packet, and determines whether the SYN packet having the same sequence number is stored in the buffer 131A (step S53). If it is determined that the SYN packet with the same sequence number is stored in the buffer 131A (Yes in step S53), the buffer management unit 122A discards the received SYN packet without storing it in the buffer 131A (step S54). On the other hand, when it is determined that the SYN packet with the same sequence number is not stored in the buffer 131A (No in step S53), the buffer management unit 122A stores the received SYN packet in the buffer 131A (step S55). If it is determined that the received packet is not a SYN packet (step S52, No), the packet identification unit 121A transmits the received packet to the destination via the communication unit 110A without storing the received packet in the buffer 131A (step S52). S56). Then, the buffer management unit 122A sequentially transmits the SYN packets stored in the buffer 131A to the server 50 at a predetermined transmission rate (step S57). This completes the communication control process in the second embodiment.

(Effect of 2nd Embodiment)
As described above, in the communication control system according to the second embodiment, the buffer management unit has the sequence number of the SYN packet transmitted from the information processing apparatus to the server among the packets received by the reception unit (communication unit). If the sequence number of the SYN packet stored in the buffer is the same, the SYN packet received by the receiving unit is discarded. For this reason, the retransmission packet is not stored redundantly in the buffer, and the server is prevented from repeatedly processing the same SYN packet. For this reason, a decrease in the number of connections established per unit time between the server and the information processing apparatus is suppressed.

(Third embodiment)
In the second embodiment, the communication control device 10A checks the duplication with the packet in the buffer at the time of receiving the packet, and discards the received packet if there is a duplication. In the third embodiment, when a packet is transmitted from a buffer, the communication control system checks whether there is a packet that overlaps the packet in the buffer, and discards the duplicate packet in the buffer.

  FIG. 6 is a diagram illustrating an example of the configuration of the communication control apparatus according to the third embodiment. The communication control apparatus 10B according to the third embodiment includes a communication unit 110B, a control unit 120B, and a storage unit 130B. The function and configuration of the communication unit 110B are the same as those in the first and second embodiments.

  The control unit 120B includes a packet identification unit 121B and a buffer management unit 122B.

  The storage unit 130B includes a buffer 131B. The configurations and functions of the storage unit 130B and the buffer 131B are the same as those in the first and second embodiments. However, the SYN packet stored in the buffer 131B is managed by the buffer management unit 122B.

  The packet identification unit 121B identifies the SYN packet addressed to the server 50 from the information processing devices 20A, 20B, 20C, and 20D among the packets received by the communication unit 110B. Then, the packet identification unit 121B stores the identified SYN packet in the buffer 131B. The packet identification unit 121B transfers packets other than the identified SYN packet to the destination via the communication unit 110B.

  The buffer management unit 122B extracts the sequence number of the SYN packet to be transmitted at the timing of transmitting the SYN packet from the buffer 131B based on a predetermined transmission rate. Then, the buffer management unit 122B determines whether SYN packets having the same sequence number are stored in the buffer 131B. When the SYN packet with the same sequence number is stored in the buffer 131B, the buffer management unit 122B discards the SYN packet with the same sequence number stored in the buffer 131B. Then, the buffer management unit 122B transmits the SYN packet at the transmission timing to the server 50 via the communication unit 110B.

(Example of flow of communication control processing according to third embodiment)
FIG. 7 is a flowchart illustrating an example of a process flow in the communication control system according to the third embodiment. First, the communication unit 110B receives a packet (step S71). The packet identification unit 121B identifies the SYN packet addressed to the server 50 from the information processing devices 20A, 20B, 20C, and 20D from the received packet. Then, the packet identification unit 121B distributes the identified SYN packet to the buffer 131B (step S72). The buffer management unit 122B determines whether or not the predetermined timing for transmitting the SYN packet from the buffer 131B has come (step S73). When it is determined that it is not the predetermined timing (No at Step S73), the buffer management unit 122B repeats the determination at Step S73 again. If it is determined that the predetermined timing has been reached (step S73, Yes), the buffer management unit 122B determines whether a SYN packet having the same sequence number as the SYN packet to be transmitted is stored in the buffer 131B (step S74). ). When it is determined that the SYN packet with the same sequence number is stored (Yes at Step S74), the buffer management unit 122B discards the SYN packet with the same sequence number stored in the buffer 131B (Step S75). . Then, the buffer management unit 122B transmits the SYN packet at the transmission timing to the server 50 via the communication unit 110B (step S76). On the other hand, if it is determined that the SYN packet having the same sequence number is not stored (No in step S74), the buffer management unit 122B transmits the SYN packet that has reached the transmission timing as it is to the server 50 via the communication unit 110B. (Step S76). This ends the process.

(Effect of the third embodiment)
As described above, in the communication control system according to the third embodiment, the buffer management unit, among the packets received by the reception unit (communication unit), is stored in the buffer and then transmitted from the buffer to the server. Is the same as the sequence number of another SYN packet stored in the buffer, the other SYN packet stored in the buffer is discarded. For this reason, duplicate SYN packets are temporarily stored in the buffer, but do not reach the server, so the number of connections established per unit time is reduced by the server repeatedly processing the same SYN packet. Is suppressed.

(Fourth embodiment)
In the second and third embodiments, the communication control system checks the received SYN packet and determines whether to discard the received SYN packet or the packet in the buffer. The communication control system according to the fourth embodiment checks the ACK packet transmitted from the server in response to the SYN packet, and determines whether to discard the packet in the buffer.

  FIG. 8 is a diagram illustrating an example of the configuration of the communication control apparatus according to the fourth embodiment. A communication control apparatus 10C according to the fourth embodiment includes a communication unit 110C, a control unit 120C, and a storage unit 130C. The function and configuration of the communication unit 110C are the same as those in the first to third embodiments.

  The control unit 120C includes a packet identification unit 121C and a buffer management unit 122C.

  The storage unit 130C includes a buffer 131C. The configurations and functions of the storage unit 130C and the buffer 131C are the same as those in the first to third embodiments. However, the SYN packet stored in the buffer 131C is managed by the buffer management unit 122C.

  In the fourth embodiment, the packet identification unit 121C identifies the ACK packet transmitted in response to the SYN packet from the server 50 in addition to the SYN packet transmitted from the information processing apparatuses 20A to 20D to the server 50. To do. Then, the packet identification unit 121C stores the identified SYN packet in the buffer 131C, mirrors the identified ACK packet, and passes it to the buffer management unit 122C.

  The buffer management unit 122C extracts the sequence number of the ACK packet mirrored by the packet identification unit 121C. The buffer management unit 122C determines whether the SYN packet having the same sequence number as the ACK packet is stored in the buffer 131C. When SYN packets with the same sequence number are stored in the buffer 131C, the buffer management unit 122C discards the SYN packet with the same sequence number in the buffer 131C.

  As described above, in the fourth embodiment, the SYN packet is not monitored, but the ACK packet transmitted corresponding to the SYN packet is monitored. Since communication is considered to be established based on the ACK packet when the ACK packet is transmitted from the server 50, it is not necessary to transmit a SYN packet having the same sequence number to the server 50 thereafter. Therefore, the communication control apparatus 10C according to the fourth embodiment discards the SYN packet having the same sequence number from the buffer 131C when confirming that the ACK packet has been transmitted.

(Example of flow of communication control processing according to fourth embodiment)
FIG. 9 is a flowchart illustrating an example of a processing flow in the communication control system according to the fourth embodiment. First, the communication unit 110C receives a packet (step S91). The packet identification unit 121C determines whether or not the received packet is a SYN packet addressed to the server 50 from the information processing devices 20A to 20D (step S92). If it is determined that the packet is a SYN packet (step S92, Yes), the packet identification unit 121C distributes the SYN packet to the buffer 131C (step S93). On the other hand, if it is determined that the packet is not a SYN packet (No in step S92), the packet identification unit 121C determines whether or not the received packet is an ACK packet (step S94). If it is determined that the received packet is not an ACK packet (step S94, No), the packet identification unit 121C transmits the packet as it is to the destination via the communication unit 110C (step S95). If it is determined that the received packet is an ACK packet (step S94, Yes), the packet identification unit 121C mirrors the packet and passes it to the buffer management unit 122C. Then, the buffer management unit 122C extracts the sequence number of the mirrored ACK packet. The buffer management unit 122C determines whether a SYN packet having the same sequence number as the ACK packet is stored in the buffer 131C (step S96). If it is determined that the SYN packet with the same sequence number is stored in the buffer 131C (step S96, Yes), the buffer management unit 122C discards the SYN packet with the same sequence number from the buffer 131C (step S97). Then, the buffer management unit 122C transmits the SYN packet stored in the buffer 131C to the server 50 at a predetermined transmission rate (step S98). On the other hand, when it is determined that the SYN packet having the same sequence number is not stored in the buffer 131C (No in step S96), the buffer management unit 122C discards the mirrored ACK packet (step S99). Then, the buffer management unit 122C transmits the SYN packet stored in the buffer 131C to the server 50 at a predetermined transmission rate (step S98). This ends the process.

(Effect of the fourth embodiment)
As described above, in the communication control system according to the fourth embodiment, the buffer management unit has the sequence number of the ACK packet transmitted from the server to the information processing apparatus among the packets received by the reception unit (communication unit). If the sequence number of the SYN packet stored in the buffer is the same, the SYN packet stored in the buffer is discarded. For this reason, after confirming the transmission of the ACK packet, the SYN packet transmitted for the purpose of establishing the same connection can be discarded. For this reason, according to the communication control system according to the fourth embodiment, connections can be established more reliably, unnecessary retransmissions of SYN packets are reduced, and a reduction in the number of connections established per unit time is suppressed. be able to.

(Fifth embodiment)
In the second to fourth embodiments, it is determined whether to discard the received SYN packet or the SYN packet stored in the buffer based on the sequence number of the SYN packet or the ACK packet received by the communication control device. It was. In the fifth embodiment, the SYN packet stored in the buffer is discarded in consideration of the retransmission interval of the SYN packet.

  FIG. 10 is a diagram for explaining a retransmission interval of a SYN packet, which is a premise of the communication control process according to the fifth embodiment. In the example of FIG. 10, it is assumed that a large number of SYN packets are transmitted from a plurality of information processing apparatuses to the server at substantially the same timing. For example, assume that 1000 SYN packets are transmitted to the server at time 0 seconds. In this case, it is assumed that the number of SYN packets that can be processed simultaneously by the server is 80. Then, the server cannot process 920 of the SYN packets received at time 0 seconds and discards them. Since the information processing apparatus that has transmitted the discarded SYN packet retransmits the SYN packet in accordance with the algorithm defined in RFC, the server receives 920 SYN packets again almost simultaneously. For example, in the example of FIG. 10, the server receives 920 retransmission packets at time 1 second. Since the retransmission interval of the SYN packet is set to double for each retransmission, the server receives 840 retransmission packets at time 3 seconds, which is the next retransmission timing. Similar processing is repeated at each retransmission timing.

  In the communication control system according to the fifth embodiment, the packet reception rate is monitored based on such a premise. When the reception rate exceeds a predetermined threshold, the communication control system discards all SYN packets in the buffer after a predetermined time has elapsed since the reception rate exceeded the predetermined threshold. The predetermined time is set to a time shorter than the initial value of the retransmission interval of the SYN packet.

(Example of configuration of communication control apparatus according to fifth embodiment)
FIG. 11 is a diagram illustrating an example of a configuration of a communication control apparatus according to the fifth embodiment. A communication control device 10D according to the fifth embodiment includes a communication unit 110D, a control unit 120D, and a storage unit 130D. The configuration and function of the communication unit 110D are the same as those in the first to fourth embodiments.

  The control unit 120D includes a packet identification unit 121D, a buffer management unit 122D, and a reception rate detection unit 123D.

  The storage unit 130D includes a buffer 131D. The configurations and functions of the storage unit 130D and the buffer 131D are the same as those in the first to fourth embodiments. However, the SYN packet stored in the buffer 131D is managed by the buffer management unit 122D.

  The packet identification unit 121D identifies the SYN packet addressed to the server 50 from the information processing devices 20A to 20D from the packet received by the communication unit 110D, and stores it in the buffer 131D.

  The buffer management unit 122D receives a notification from the reception rate detection unit 123D when the SYN packet reception rate exceeds a predetermined threshold. Then, the buffer management unit 122D discards all SYN packets stored in the buffer 131D when a predetermined time elapses after the SYN packet reception rate exceeds a predetermined threshold.

  The reception rate detection unit 123D detects the reception rate of the SYN packet received by the communication control device 10D. The reception rate detection unit 123D may detect the reception rate by monitoring the identification of the SYN packet by the packet identification unit 121D, for example. In addition, the reception rate detection unit 123D may detect the reception rate by monitoring storage of the SYN packet in the buffer 131D, for example. The reception rate detection unit 123D detects the reception rate as needed, and compares the reception rate with a predetermined threshold value. The reception rate detection unit 123D notifies the buffer management unit 122D when the detected reception rate exceeds a predetermined threshold.

  Here, the reception rate refers to the number of SYN packets per unit time received from the information processing apparatuses 20A to 20D and received by the communication control apparatus 10D at a predetermined time. The predetermined threshold value to be compared with the reception rate is, for example, the number of SYN packets transmitted from the buffer 131D during the initial value of the SYN packet retransmission interval by the communication control apparatus 10D.

(Example of flow of communication control processing according to fifth embodiment)
FIG. 12 is a flowchart illustrating an example of a process flow in the communication control system according to the fifth embodiment. First, the reception rate detection unit 123D detects the reception rate of the SYN packet (step S101). Then, the reception rate detection unit 123D compares the detected reception rate with a predetermined threshold value, and determines whether or not the detected reception rate exceeds the predetermined threshold value (step S102). When it is determined that the detected reception rate does not exceed the predetermined threshold (No in step S102), the reception rate detection unit 123D ends the process. On the other hand, if the reception rate detection unit 123D determines that the detected reception rate exceeds a predetermined threshold (Yes in step S102), the reception rate detection unit 123D notifies the buffer management unit 122D to that effect. The buffer management unit 122D that has received the notification determines whether or not a predetermined time has elapsed since it was detected that the reception rate exceeded a predetermined threshold (step S103). If it is determined that the predetermined time has not elapsed (No at Step S103), the buffer management unit 122D returns to Step S103 and repeats the determination. When it is determined that the predetermined time has elapsed (step S103, Yes), the buffer management unit 122D discards all SYN packets in the buffer 131D (step S104). This ends the process.

(Effect of 5th Embodiment)
Thus, in the fifth embodiment, the communication control system further includes a detection unit (reception rate detection unit) that detects the reception rate of the SYN packet received by the reception unit (communication unit). Then, when the reception rate detected by the detection unit exceeds the first threshold value (predetermined threshold value), the buffer management unit exceeds the first threshold value for the first time (predetermined time shorter than the retransmission interval). ) Later, discard the packet stored in the buffer. Therefore, when a large number of SYN packets are transmitted to the server almost simultaneously, it is possible to prevent a large number of retransmission packets from being received and stored in the buffer again at the same timing. For this reason, it is possible to prevent the server from repeatedly processing the SYN packet and the retransmission packet for the same connection, and it is possible to suppress a decrease in the number of connections established per unit time.

  In addition, the communication control system according to the fifth embodiment does not perform a match determination between the sequence number of the SYN packet in the buffer and the sequence number of the received packet, and the SYN packet in the buffer is based on the reception rate of the SYN packet. Determine whether or not to discard. For this reason, it is possible to ensure higher scalability as compared with a method involving sequence number coincidence determination.

(Sixth embodiment)
In the fifth embodiment, when packets exceeding the processable number are transmitted to the server at the same time, it is stored in the buffer on the assumption that retransmission packets corresponding to the packets exceeding the processable number are transmitted. It is assumed that the SYN packet to be discarded is discarded at a predetermined timing. On the other hand, when a reception rate that exceeds the first threshold is detected, the communication control system according to the sixth embodiment predicts the next timing when the reception rate exceeds the second threshold. Then, when a reception rate exceeding the second threshold is detected at the predicted timing, the SYN packet stored in the buffer is discarded.

  FIG. 13 is a diagram illustrating an example of the configuration of the communication control apparatus according to the sixth embodiment. A communication control apparatus 10E according to the sixth embodiment includes a communication unit 110E, a control unit 120E, and a storage unit 130E. The configuration and function of the communication unit 110E are the same as those in the first to fifth embodiments.

  The control unit 120E includes a packet identification unit 121E, a buffer management unit 122E, and a reception rate detection unit 123E.

  The storage unit 130E includes a buffer 131E. The configurations and functions of the storage unit 130E and the buffer 131E are the same as those in the first to fifth embodiments. However, the SYN packet stored in the buffer 131E is managed by the buffer management unit 122E.

  The packet identification unit 121E identifies the SYN packet addressed to the server 50 from the information processing devices 20A to 20D among the packets received by the communication unit 110E, and stores the SYN packet in the buffer 131E.

  The buffer management unit 122E receives a notification when the reception rate of the SYN packet exceeds the first threshold value from the reception rate detection unit 123E. When the buffer management unit 122E receives the notification, the buffer management unit 122E predicts the next timing when the reception rate exceeds the second threshold. When the notification that the reception rate has exceeded the second threshold is received from the reception rate detection unit 123E at the predicted timing, the buffer management unit 122E discards the SYN packet stored in the buffer 131E. If the notification is not received at the predicted timing, the buffer management unit 122E ends the process. When the notification is received at the predicted timing, the buffer management unit 122E further predicts the next timing when the reception rate exceeds the third threshold. If the notification indicating that the reception rate exceeds the third threshold is received at the predicted timing, the buffer management unit 122E discards the SYN packet stored in the buffer 131E. The buffer management unit 122E repeats the process until no notification is received at the predicted timing.

  The reception rate detection unit 123E detects the reception rate of the SYN packet received by the communication control device 10E. Similar to the reception rate detection unit 123D of the fifth embodiment, the reception rate detection unit 123E may monitor the identification of the SYN packet by the packet identification unit 121E and detect the reception rate. Further, the reception rate detection unit 123E may detect the reception rate by monitoring the storage of the SYN packet in the buffer 131E. The reception rate detection unit 123E detects the reception rate as needed, and compares the reception rate with the first threshold value. Then, when the detected reception rate exceeds the first threshold, the reception rate detection unit 123E notifies the buffer management unit 122E.

(An example of a method for predicting the timing at which the reception rate exceeds the threshold)
FIG. 15 is a diagram for explaining a technique for predicting the timing at which the reception rate exceeds the threshold in the communication control process according to the sixth embodiment. As described above, the retransmission interval is defined by RFC for the transmission of SYN packets using TCP. Therefore, the communication control apparatus 10E according to the sixth embodiment predicts the timing at which the reception rate exceeds the threshold based on RFC regulations. For example, when the server 50 is communicating with the information processing apparatuses 20A to 20D using the Linux (registered trademark) OS, the initial value of the retransmission interval is 1 second. Therefore, the buffer management unit 122E predicts that the initial value of the retransmission interval is 1 second and doubles every time retransmission is performed. That is, in the example of FIG. 15, when the buffer management unit 122E receives a notification from the reception rate detection unit 123E at the timing of time 0 seconds, the buffer management unit 122E predicts the next timing when the reception rate exceeds the threshold as time 1 seconds. When the notification is received from the reception rate detection unit 123E at the timing of 1 second, the buffer management unit 122E predicts that the next timing when the reception rate exceeds the threshold is 3 seconds when 2 times 1 second has elapsed. To do. Similarly, when the notification is received from the reception rate detection unit 123E at the timing of 3 seconds, the buffer management unit 122E has passed 4 seconds, which is twice the second when the reception rate exceeds the threshold next time. The time is predicted to be 7 seconds.

  If the buffer management unit 122E receives a notification from the reception rate detection unit 123E at a timing that was not predicted, the buffer management unit 122E assumes that the time of the notification is the transmission time of the initial SYN packet, and then receives it. Predict when the rate exceeds the threshold.

  Note that it is expected that there will be a slight deviation in the time for the SYN packet to reach the communication control device 10E due to the transmission / reception processing of the SYN packet and communication delay on the network. Therefore, an error of about 100 milliseconds (ms) before and after the predicted timing is expected. Then, if there is a notification from the reception rate detection unit 123E during a period of about 100 milliseconds before and after the predicted timing, the buffer management unit 122E compares the detected reception rate with a threshold corresponding to the number of predictions. Then, the buffer management unit 122E discards the SYN packet stored in the buffer 131E if the reception rate exceeds the threshold value.

(Example of threshold setting method for comparison with reception rate)
FIG. 16 is a diagram for explaining a method for setting a threshold in the communication control process according to the sixth embodiment. For example, in FIG. 16, it is assumed that the initial value of the SYN packet retransmission interval is 1 second. Assume that the retransmission interval is doubled for each retransmission. Here, it is assumed that the number of SYN packets received by the communication control apparatus 10E at time 0 seconds shown in FIG. 16 exceeds the number of packets that can be transmitted from the buffer 131E in one second. Then, an untransmitted SYN packet remains in the buffer 131E at time 1 second. Since an untransmitted SYN packet has not reached the server 50 and an ACK packet has not been transmitted, a retransmission packet of an untransmitted SYN packet is transmitted.

  If the number of SYN packets received by the communication control device 10E at time 0 second is equal to or less than the number of SYN packets transmitted from the buffer 131E to the server 50 during 1 second, the buffer 131E is stored at time 1 second. There are no SYN packets remaining. Therefore, in the sixth embodiment, the first threshold value is the number of SYN packets transmitted from the buffer 131E to the server 50 during the initial value of the retransmission interval. Further, the second threshold value is the number of SYN packets transmitted from the buffer 131E to the server 50 during a period twice the initial value of the retransmission interval. Further, the third threshold value is the number of SYN packets transmitted from the buffer 131E to the server 50 during a period four times the initial value of the retransmission interval. Subsequent threshold values are similarly set.

  For example, in the example of FIG. 16, the initial value of the retransmission interval is t (seconds), and the transmission rate of the buffer 131E is R (number / second). Then, S is the number of SYN packets transmitted from the buffer 131E in t seconds. At this time, the first threshold value to be compared with the reception rate detected by the reception rate detection unit 123E is R × t = S. Next, the second threshold value to be compared with the reception rate detected by the reception rate detection unit 123E is R × t × 2 = 2S. Further, the third threshold value that is next compared with the reception rate by the reception rate detection unit 123E is R × t × 2 × 2 = 4S.

  In the sixth embodiment, it is assumed that the reception rate detection unit 123E compares the detected reception rate with a preset first threshold and notifies the buffer management unit 122E. Then, if the notified buffer management unit 122E is a timing at which the notified timing predicts that the reception rate exceeds the threshold in advance, the buffer management unit 122E sets the threshold set according to the number of predictions and the notified reception rate. Compare. For example, when the notified time is the first predicted time after the reception rate first exceeds the first threshold, the buffer management unit 122E sets the reception rate to the second threshold (t × 2 × 1 ×). R) is determined. Further, when the notified time point is the second predicted time point after the reception rate first exceeds the first threshold value, the buffer management unit 122E sets the reception rate to the third threshold value (t × 2 × 2 ×). R) is determined. In addition, when the notified time point is the third prediction time point after the reception rate first exceeds the first threshold value, the buffer management unit 122E sets the reception rate to the fourth threshold value (t × 2 × 4 ×). R) is determined. Further, when the notified time point is not the predicted time point, the buffer management unit 122E sets the time point as the initial transmission time point of the SYN packet and predicts the next time point when the reception rate exceeds the second threshold.

  Note that the prediction time point and the threshold value corresponding to the prediction time point may be calculated in advance based on the initial value of the retransmission interval defined in the RFC and stored in the storage unit 130E.

(Example of flow of communication control processing in sixth embodiment)
FIG. 14 is a flowchart illustrating an example of a processing flow in the communication control system according to the sixth embodiment. The reception rate detection unit 123E detects the reception rate of the SYN packet (step S1401). Then, the reception rate detection unit 123E determines whether or not the detected reception rate exceeds the first threshold (step S1402). If the reception rate detection unit 123E determines that the detected reception rate does not exceed the first threshold (No in step S1402), the reception rate detection unit 123E returns to step S1401 and continues detection. On the other hand, when it is determined that the detected reception rate exceeds the first threshold (Yes in step S1402), the reception rate detection unit 123E notifies the buffer management unit 122E to that effect. Upon receiving the notification, the buffer management unit 122E predicts the next time that the reception rate exceeds the threshold (step S1403). The buffer management unit 122E determines whether or not the reception rate exceeds a corresponding threshold value at the predicted time (step S1404). If it is determined that the reception rate does not exceed the corresponding threshold value at the predicted time (step S1404, No), the buffer management unit 122E ends the process. On the other hand, if it is determined that the reception rate has exceeded the threshold at the predicted time (step S1404, Yes), the buffer management unit 122E discards the SYN packet stored in the buffer 131E (step S1405). Then, the buffer management unit 122E again predicts the next time when the reception rate exceeds the threshold and repeats the process (step S1403). If the buffer management unit 122E determines that the reception rate has not exceeded the threshold at the predicted time (step S1404, No), the process ends.

(Effect of 6th Embodiment)
As described above, the communication control system according to the sixth embodiment further includes a detection unit (reception rate detection unit) that detects the reception rate of the SYN packet received by the reception unit (communication unit). When the reception rate detected by the detection unit exceeds the first threshold, the buffer management unit calculates a second time when the reception rate is predicted to exceed the second threshold, and the detection unit When the reception rate detected at time 2 exceeds the second threshold, the packet stored in the buffer is discarded. For this reason, according to the communication control system of the sixth embodiment, the SYN packet in the buffer is continuously transmitted to the server at a predetermined transmission rate until it is predicted that a large number of retransmission packets are transmitted. Can do. For this reason, according to the sixth embodiment, it is possible to shorten the period during which no SYN packet is transmitted from the buffer, compared to the process of clearing the buffer immediately when the reception rate exceeds the threshold. In addition, since the SYN packet predicted to be retransmitted is discarded from the buffer, it is possible to prevent the same retransmission packet from being accumulated in the buffer. For this reason, it is possible to prevent the server from repeatedly processing the same retransmission packet, and to suppress a decrease in the number of connections established per unit time.

  In the communication control system according to the sixth embodiment, the buffer management unit discards the packet stored in the buffer when the reception rate detected by the detection unit at the second time exceeds the second threshold. Next, a third time when the reception rate is predicted to exceed the third threshold value is calculated, and when the reception rate detected by the detection unit at the third time exceeds the third threshold value, it is stored in the buffer. Abandoned packets again. As described above, the communication control system of the sixth embodiment manages the SYN packet in the buffer by continuously monitoring the reception rate until the retransmission of the SYN packet converges. Therefore, the communication control system of the sixth embodiment can control the SYN packet stored in the buffer in accordance with the retransmission interval of the SYN packet. For this reason, it is possible to prevent the server from repeatedly processing the same retransmission packet, and to suppress a decrease in the number of connections established per unit time.

  In addition, the communication control system according to the sixth embodiment does not perform a match determination between the sequence number of the SYN packet in the buffer and the sequence number of the received packet, and the SYN packet in the buffer is based on the reception rate of the SYN packet. Determine whether or not to discard. For this reason, it is possible to ensure higher scalability as compared with a method involving sequence number coincidence determination.

  The communication control method of the above embodiment can be used when a network administrator applies shaping to communication using TCP.

(Modification)
In the above embodiment, the packet identification unit and the buffer management unit are provided in the communication control device provided in the communication control system. However, the present invention is not limited to this, and the packet identification unit and the buffer management unit may be arranged on the network as independent devices. Further, the packet identification unit and the buffer management unit may be incorporated in the server. Similarly, the reception rate detection unit may be an independent device, or may be incorporated in the server together with the packet identification unit and the buffer management unit. That is, in the communication control system, each functional unit included in the communication control device may be arranged on the communication path between the information processing device that establishes a connection using TCP and the server.

  For example, FIG. 17 is a diagram for explaining an example in which the function of the communication control device according to each embodiment is mounted on a plurality of devices. The communication control system 1B illustrated in FIG. 17 is different from the communication control system 1A illustrated in FIG. 1 in the arrangement of functional units included in the communication control device. In other points, the communication control system 1B shown in FIG. 17 is the same as the communication control system 1A shown in FIG.

  In the first to sixth embodiments, it has been described that the packet identification unit, the buffer management unit, and the reception rate detection unit are arranged in one communication control device. However, the present invention is not limited to this, and each functional unit can be arranged on another device as shown in FIG.

  In the example of FIG. 17, the packet identification device 11 is connected between the information processing devices 20 </ b> A to 20 </ b> D and the server 50 via the networks 40 and 60. The packet identification device 11 is connected to a buffer management device 13 including a buffer 12. The reception rate monitoring device 14 is connected to the packet identification device 11 and the buffer management device 13.

  The packet identification device 11 is a device that can execute the functions of the packet identification units 121 to 121E according to the first to sixth embodiments. The packet identification device 11 can be composed of a router, for example. The packet identification device 11 identifies the SYN packet and transmits it to the buffer management device 13. The packet identification device 11 identifies and mirrors the ACK packet, and transmits the mirrored ACK packet to the buffer management device 13.

  The buffer 12 stores SYN packets transferred from the packet identification device 11 in the order received. Then, the buffer 12 sequentially transmits from the previously received SYN packet first at a predetermined transmission rate.

  The buffer management device 13 is a device that can execute the functions of the buffer management units 122 to 122E according to the first to sixth embodiments. For example, the buffer management device 13 may be incorporated in the server 50 or may be a device independent of the server.

  The reception rate monitoring device 14 is a device that can execute the functions of the reception rate detection units 123D and 123E according to the fifth and sixth embodiments. In the example of FIG. 17, the reception rate monitoring device 14 is connected to both the packet identification device 11 and the buffer management device 13, but may be configured to be connected to only one of them.

  As described above, the functions of the communication control devices 10 to 10E can be implemented by being mounted on different devices. Moreover, you may mount a part of function of the communication control apparatuses 10-10E in existing apparatuses, such as an APL server. In the example of FIG. 17, the buffer management device 13 includes the buffer 12. However, the buffer 12 may be provided on a device different from the buffer management device 13 and connected to the buffer management device 13. it can.

(program)
It is also possible to create a program in which the processing executed by the communication control system described in the above embodiment is described in a language that can be executed by a computer. For example, a communication control program in which processing executed by the communication control apparatus according to the embodiment is described in a language that can be executed by a computer can be created. In this case, when the computer executes the communication control program, it is possible to obtain the same effect as in the above embodiment. Further, the same processing as in the above embodiment may be realized by recording the communication control program on a computer-readable recording medium, and reading and executing the communication control program recorded on the recording medium. Good.

  FIG. 20 is a diagram illustrating a computer 1000 that executes a communication control program. As illustrated in FIG. 20, the computer 1000 includes, for example, a memory 1010, a CPU 1020, a hard disk drive interface 1030, a disk drive interface 1040, a serial port interface 1050, a video adapter 1060, and a network interface 1070. These units are connected by a bus 1080.

  The memory 1010 includes a ROM (Read Only Memory) 1011 and a RAM 1012 as illustrated in FIG. The ROM 1011 stores a boot program such as BIOS (Basic Input Output System). The hard disk drive interface 1030 is connected to the hard disk drive 1031 as illustrated in FIG. The disk drive interface 1040 is connected to the disk drive 1041 as illustrated in FIG. For example, a removable storage medium such as a magnetic disk or an optical disk is inserted into the disk drive 1041. The serial port interface 1050 is connected to a mouse 1051 and a keyboard 1052, for example, as illustrated in FIG. The video adapter 1060 is connected to a display 1061, for example, as illustrated in FIG.

  Here, as illustrated in FIG. 20, the hard disk drive 1031 stores, for example, an OS 1091, an application program 1092, a program module 1093, and program data 1094. That is, the communication control program is stored in, for example, the hard disk drive 1031 as a program module in which a command executed by the computer 1000 is described.

  The various data described in the above embodiment is stored as program data, for example, in the memory 1010 or the hard disk drive 1031. Then, the CPU 1020 reads the program module 1093 and the program data 1094 stored in the memory 1010 and the hard disk drive 1031 to the RAM 1012 as necessary, and executes various processing procedures.

  Note that the program module 1093 and the program data 1094 related to the communication control program are not limited to being stored in the hard disk drive 1031, but are stored in, for example, a removable storage medium and read out by the CPU 1020 via the disk drive or the like. Also good. Alternatively, the program module 1093 and the program data 1094 related to the communication control program are stored in another computer connected via a network (LAN (Local Area Network), WAN (Wide Area Network), etc.), and the network interface 1070 is stored. Via the CPU 1020.

  Of the processes described in this embodiment, all or part of the processes described as being performed automatically can be performed manually, or the processes described as being performed manually can be performed. All or a part can be automatically performed by a known method. In addition, the processing procedure, control procedure, specific name, and information including various data and parameters shown in the above-described document and drawings can be arbitrarily changed unless otherwise specified.

  The above embodiments and modifications thereof are included in the invention disclosed in the claims and equivalents thereof as well as included in the technology disclosed in the present application.

1A, 1B Communication control system 10, 10A, 10B, 10C, 10D, 10E Communication control device 20A, 20B, 20C, 20D Information processing device 30 Gateway 40 Network 50 Server 60 Network 110, 110A, 110B, 110C, 110D, 110E Communication Unit 120, 120A, 120B, 120C, 120D, 120E Control unit 121, 121A, 121B, 121C, 121D, 121E Packet identification unit 122, 122A, 122B, 122C, 122D, 122E Buffer management unit 123D, 123E Reception rate detection unit 130 , 130A, 130B, 130C, 130D, 130E Storage unit 131, 131A, 131B, 131C, 131D, 131E Buffer

Claims (8)

A receiving unit that receives packets transmitted and received between the server and the information processing apparatus that establishes a connection using TCP (Transmission Control Protocol) on the network;
A packet identifying unit that distributes a SYN (Synchronization) packet transmitted from the information processing apparatus to the server among the packets received by the receiving unit;
A transmission unit for transmitting the SYN packet stored in the buffer to the server at a predetermined transmission rate;
A buffer management unit for discarding a SYN packet stored in a buffer or a received packet when a packet received by the receiving unit satisfies a predetermined condition;
A communication control system comprising:   The buffer management unit, when the sequence number of the SYN packet transmitted from the information processing apparatus to the server among the packets received by the reception unit is the same as the sequence number of the SYN packet stored in the buffer The communication control system according to claim 1, wherein the SYN packet received by the receiving unit is discarded.   The buffer management unit stores the sequence number of a SYN packet stored in the buffer and then transmitted from the buffer to the server among the packets received by the reception unit. 2. The communication control system according to claim 1, wherein when the sequence number is the same as the sequence number, the other SYN packet stored in the buffer is discarded.   The buffer management unit is configured such that a sequence number of an ACK (Acknowledgement) packet transmitted from the server to the information processing device is the same as a sequence number of a SYN packet stored in the buffer among the packets received by the reception unit. The communication control system according to claim 1, wherein the SYN packet stored in the buffer is discarded. A detector that detects a reception rate of the SYN packet received by the receiver;
When the reception rate detected by the detection unit exceeds a first threshold, the buffer management unit discards a packet stored in the buffer after a first time after exceeding the first threshold. The communication control system according to claim 1, wherein: A detector that detects a reception rate of the SYN packet received by the receiver;
When the reception rate detected by the detection unit exceeds a first threshold, the buffer management unit calculates a second time when the reception rate is predicted to exceed the second threshold next, and the detection unit 2. The communication control system according to claim 1, wherein if the reception rate detected at the second time exceeds the second threshold, the packet stored in the buffer is discarded.   The buffer management unit discards the packet stored in the buffer when the reception rate detected by the detection unit at the second time exceeds the second threshold, and then the reception rate is the third A third time predicted to exceed the threshold is calculated, and when the reception rate detected by the detection unit at the third time exceeds the third threshold, the packet stored in the buffer is discarded again. The communication control system according to claim 6. A communication control method for controlling communication between an information processing apparatus and a server that establishes a connection using TCP on a network,
A receiving step of receiving a packet transmitted and received between the information processing apparatus and the server;
A packet identification step of distributing SYN packets transmitted from the information processing apparatus to the server among the packets received in the reception step;
A transmission step of transmitting a SYN packet stored in the buffer to the server at a predetermined transmission rate;
A buffer management step of discarding a SYN packet stored in a buffer or a received packet when a packet received in the reception step satisfies a predetermined condition;
A communication control method characterized in that a computer executes.

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