JP6506192B2 - Communication control system and communication control method - Google Patents

Description

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

  Conventionally, 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 three-way handshake is usually performed. In the three-way handshake, first, one information processing apparatus transmits to the other information processing apparatus a SYN (Synchronization) packet requesting establishment of a communication connection (connection). The other information processing apparatus transmits a SYN-ACK (Acknowledgement) packet in order to permit connection according to 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. In addition, in such TCP communication, a method has been proposed in which only SYN packets are selectively buffered to apply rate limit.

Akihiro Kimura, Atsushi Nishiyama, Takeshi Osaka, Ichiro Kudo, "Proposal of NW function to reduce the number of servers for IoT service provision", [online], [search on February 5, 2016], Internet <http: / /ci.nii.ac.jp/naid/40020429786>

  However, in the prior art, in order to increase the utilization efficiency of the APL server, the transmission rate of the packet buffer function unit is set to an appropriate value in consideration of the speed at which the connection is released (connection release rate) in the APL server. The problem is that it takes time and effort to measure the connection release rate.

  In addition, the usage rate of the APL server may decrease, and it may take time until the connection probability. For example, when the connection continuation time varies and the connection release rate fluctuates, setting the transmission rate to a fixed value leads to a decrease in the utilization efficiency of the server and an increase in the time required to establish the connection.

  That is, when the connection duration time is short, if the connection release rate exceeds the transmission rate, the APL server can establish a connection, but the SYN packet does not arrive, and the utilization efficiency of the APL server decreases. Also, if the connection duration time is long, when the connection release rate falls below the transmission rate, the APL server discards the SYN packet, and the user terminal has an opportunity to establish the connection after the next packet retransmission, until the connection is established. Time required for

  In order to solve the problems described above and to achieve the object, a communication control system according to the present invention is a receiving unit that receives packets transmitted and received between a user terminal and a server establishing a connection using TCP on a network. And a packet identification unit that distributes a SYN packet transmitted from the user terminal to the server among the packets received by the reception unit to the buffer, and a SYN packet stored in the buffer to the server at predetermined time intervals. The transmission control unit may include: a transmission unit that repeatedly transmits; and a buffer management unit that discards the SYN packet stored in the buffer when the packet received by the reception unit satisfies a predetermined condition.

  Further, according to the communication control system of the present invention, a receiving unit for receiving a packet transmitted / received between a user terminal and a server establishing a connection using TCP on a network, and a packet received by the receiving unit, A packet identification unit that distributes a SYN packet transmitted from the user terminal to the server to a buffer, a monitoring unit that monitors the state of a connection established by the server, and a connection state monitored by the monitoring unit are predetermined And a notification unit for notifying information indicating whether or not the SYN packet can be accepted, and a SYN packet stored in the buffer based on the information notified by the notification unit. And a transmitter configured to control transmission to the server, and a packet received by the receiver satisfying a predetermined condition. And discarding the SYN packet buffer manager stored in the serial buffer, characterized in that it comprises a.

  Further, a communication control method according to the present invention is a communication control method for controlling communication between a user terminal and a server establishing a connection using TCP on a network, which is performed between the user terminal and the server A receiving step of receiving a packet to be transmitted / received, a packet identifying step of distributing a SYN packet transmitted from the user terminal to the server among the packets received by the receiving step to a buffer, an SYN packet stored in the buffer And the buffer management step of discarding the SYN packet stored in the buffer when the packet received by the reception step satisfies a predetermined condition. It is characterized by

  Further, a communication control method according to the present invention is a communication control method for controlling communication between a user terminal and a server establishing a connection using TCP on a network, which is performed between the user terminal and the server A receiving step of receiving a packet to be transmitted / received, a packet identifying step of distributing a SYN packet transmitted from the user terminal to the server among the packets received by the receiving step to a buffer, a connection established by the server A monitoring step of monitoring the state of the packet, and a notification of notifying the buffer of information indicating whether or not the acceptance of the SYN packet is possible when the state of the connection monitored by the monitoring step satisfies a predetermined condition Of the SYN packet stored in the buffer based on the process and the information notified by the notification process. A transmitting step of controlling transmission to the server, and a buffer managing step of discarding the SYN packet stored in the buffer when the packet received by the receiving step satisfies a predetermined condition. I assume.

  According to the present invention, it is possible to reduce the usage rate of the APL server and to take time to the connection probability without using the connection release rate.

FIG. 1 is a diagram showing an example of the configuration of the communication control system according to the first embodiment. FIG. 2 is a diagram showing an example of the configuration of the communication control apparatus according to the first embodiment. FIG. 3 is a sequence diagram showing an example of the flow of processing in the communication control system according to the first embodiment. FIG. 4 is a sequence diagram showing an example of the flow of processing in the communication control system according to the first embodiment. FIG. 5 is a diagram showing an example of the configuration of the communication control apparatus according to the second embodiment. FIG. 6 is a diagram showing an example of the configuration of the server according to the second embodiment. FIG. 7 is a sequence diagram showing an example of the flow of processing in the communication control system according to the second embodiment. FIG. 8 is a sequence diagram showing an example of the flow of processing in the communication control system according to the second embodiment. FIG. 9 is a diagram showing an example of the configuration of the communication control apparatus according to the third embodiment. FIG. 10 is a diagram showing an example of the configuration of a server according to the third embodiment. FIG. 11 is a sequence diagram showing an example of the flow of processing in the communication control system according to the third embodiment. FIG. 12 is a sequence diagram showing an example of the flow of processing in the communication control system according to the third embodiment. FIG. 13 is a diagram for describing an example in which the function of the communication control device according to each embodiment is mounted on a plurality of devices. FIG. 14 is a diagram for explaining an example of processing when a SYN packet is transmitted from the user terminal to the APL server. FIG. 15 is a diagram illustrating a computer that executes a communication control program.

  Hereinafter, embodiments of a communication control system and a communication control method according to the present application will be described in detail based on the drawings. Note that the communication control system and the communication control method according to the present application are not limited by the embodiment.

(An example of SYN packet transmission processing by the existing method)
First, connection establishment processing using conventional TCP will be described as a premise of the communication control system and communication control method according to the embodiment with reference to FIG. FIG. 14 is a diagram for explaining an example of processing when a SYN packet is transmitted from the user terminal to the APL server.

  In the example of FIG. 14, user terminals 1 to 4 are connected to the APL server 5 via the network A. Further, between the user terminals 1 to 4 and the APL server 5, a transfer device 6, a buffer 7 and a transmission rate control device 8 are connected.

  In starting communication with the APL server 5 via the network A, each of the user terminals 1 to 4 first transmits a SYN packet to establish a connection. The APL server 5 sends back an ACK packet as an acknowledgment for the SYN packet. When receiving the ACK packet, the user terminals 1 to 4 consider that a connection has been established, and transmit an ACK packet to the APL server 5 as a response to the received ACK packet. Also, the user terminals 1 to 4 transmit an APL layer packet to the APL server 5. In FIG. 14, the SYN packet transmitted by the user terminal n is displayed as SYN (n). Further, the ACK packet transmitted by the user terminal n is displayed as ACK (n). Also, the APL layer packet transmitted by the user terminal n is displayed as APL (n).

  Each transmitted SYN packet is assigned a sequence number. For example, a 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 response transmitted by the APL server 5 in response to the SYN packet of the sequence number "1" also becomes "1".

  The transfer device 6 receives the packets transmitted by the user terminals 1 to 4, extracts the SYN packet, and stores the extracted SYN packet in the buffer 7. The transfer device 6 transmits a packet other than the SYN packet, for example, an APL layer packet or an ACK packet to the APL server 5 without storing it 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 at a predetermined transmission rate by the transmission rate control unit 8.

  After transmitting the SYN packet, if the user terminals 1 to 4 do not receive an ACK packet responding to the SYN packet even after a predetermined time has elapsed, they resend the SYN packet. The initial value of the retransmission interval for retransmission of SYN packets in TCP is determined depending on the implementation of each user terminal. For example, it is 3 seconds for a Windows (registered trademark) -based operation system (OS) and 1 second for a Linux (registered trademark) -based OS. The second and subsequent retransmission intervals are set according to the TCP retransmission algorithm specified 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 to the buffer 7 without discriminating the first SYN packet and the retransmission packet.

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

First Embodiment
FIG. 1 is a diagram showing an example of the configuration of the communication control system according to the first embodiment. In the communication control system 1A according to the first embodiment, the communication control device 10 is connected to the user terminals 20A, 20B, 20C, 20D and AP (Access Point) 30 via the network 40. The user terminals 20B, 20C, 20D are connected to the communication control apparatus 10 via the AP 30 and the network 40. Further, the communication control device 10 is connected to the server 50 via the network 60. The configuration shown in FIG. 1 is only an example, and the communication control device 10 may be disposed on the network connecting the user terminals 20A, 20B, 20C, 20D and the server 50, and the specific configuration and each The number of devices is not particularly limited.

  The user terminals 20A, 20B, 20C, 20D exchange information with the server 50 via the networks 40, 60. The user terminals 20A, 20B, 20C, and 20D are, for example, IoT (Internet of Things) terminals or M2M (Machine to Machine) terminals.

  The AP 30 is a device that receives connection requests from the user terminals 20B, 20C, and 20D, and mediates communication to the network 40. The AP 30 may be a gateway such as an IoT gateway or an M2M gateway.

  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 the two.

  The server 50 establishes a connection with the user terminals 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 showing an example of the configuration of the communication control apparatus according to the first embodiment. The communication control device 10 is disposed on a communication path between the user terminals 20A, 20B, 20C, 20D and the server 50, as shown in FIG. The communication control device 10 controls communication between the user terminals 20A, 20B, 20C, 20D and the server 50. For example, the communication control apparatus 10 transfers to the server 50 SYN packets transmitted from the user terminals 20A, 20B, 20C, and 20D. Further, the communication control device 10 suppresses a reduction in the number of connections per unit time between the server 50 and the user terminals 20A, 20B, 20C, 20D due to the SYN packet retransmitted from the user terminals 20A, 20B, 20C, 20D. Let's control the communication.

  As shown in FIG. 2, the communication control device 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 apparatus 10. The control unit 120 can be configured by, for example, a central processing unit (CPU), a micro processing unit (MPU), an application specific integrated circuit (ASIC), or the like. The control unit 120 includes a reception unit 121, a packet identification unit 122, a transmission unit 123, and a buffer management unit 124.

  The receiving unit 121 receives, via the communication unit 110, a packet transmitted / received between the user terminal 20 establishing a connection using TCP on the network and the server 50.

  The packet identifying unit 122 distributes, to the buffer 131, an SYN packet transmitted from the user terminal 20 to the server 50 among the packets received by the receiving unit 121. Specifically, the packet identification unit 122 identifies a SYN packet transmitted from the user terminals 20A, 20B, 20C, and 20D to the server 50 among the packets received by the reception unit 121 via the communication unit 110.

  Then, the packet identification unit 122 stores the identified SYN packet in the buffer 131 described later. Also, the packet identification unit 122 transmits packets other than the SYN packet to the destination via the communication unit 110. The packet identification unit 122 identifies the user terminals 20A to 20D and the server 50 from the transmission source IP address, the transmission destination IP address, and the like. Also, the packet identification unit 122 identifies the SYN packet based on the SYN flag of the TCP header of the packet.

  The transmission unit 123 repeatedly transmits the SYN packet stored in the buffer 131 to the server 50 via the communication unit 110 at predetermined time intervals. Specifically, the transmitting unit 123 repeatedly transmits the head packet of the buffer to the server 50 at predetermined time intervals. In addition, the transmitting unit 123 may repeatedly transmit, to the server 50, SYN packets of a preset window size at predetermined time intervals.

  The buffer management unit 124 stores the SYN packets identified by the packet identification unit 122 in the buffer 131 in the order of reception. Also, the buffer management unit 124 discards the SYN packet stored in the buffer 131 when the packet received by the reception unit 121 satisfies a predetermined condition. For example, when the sequence number of the SYN / ACK (Acknowledgement) packet transmitted from the server 50 to the user terminal 20 is the same as the sequence number of the SYN packet stored in the buffer 131, the transmitting unit 123 stores it in the buffer 131. Discard the SYN packet.

  The storage unit 130 stores information used for processing of each unit in the communication control apparatus 10 and information generated as a result of the processing. The storage unit 130 may be, for example, a storage device such as a hard disk or an optical disk. The storage unit 130 may be a semiconductor memory such as a random access memory (RAM) 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 122. 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 122 in the order of reception. The stored SYN packet is transmitted to the server 50 via the communication unit 110 at a predetermined transmission rate in order from the packet stored earlier.

(An example of a flow of communication control processing according to the first embodiment)
FIG. 3 is a sequence diagram showing an example of the flow of processing in the communication control system according to the first embodiment. As shown in FIG. 3, the user terminal # 1 notifies the buffer management unit 124 of the SYN # 1 packet via the packet identification unit 122, and the user terminal # 2 buffers the SYN # 2 packet via the packet identification unit 122. It notifies the management unit 124 (steps S101 to S104). When the buffer management unit 124 receives the SYN # 1 packet and the SYN # 2 packet identified by the packet identification unit 122, the buffer management unit 124 stores the packets in the buffer 131.

  Then, the transmission unit 123 (not shown) repeatedly transmits the SYN # 1 packet stored in the buffer 131 to the server 50 via the communication unit 110 at predetermined time intervals (step S105). As shown in the example of FIG. 3, when the number of connections has reached the upper limit on the server 50 side and there is no vacancy in the connection, the SYN # 1 packet is discarded, but the connection is released and it is vacancy in the connection In the case where there is an IP address, the server 50 transmits the SYN / ACK packet # 1 to the packet identification unit 122 (step S106).

  Upon receiving the SYN / ACK packet # 1, the packet identification unit 122 copies the SYN / ACK packet # 1 and transfers the SYN / ACK packet # 1 to the user terminal # 1 (step S107). Thereafter, the user terminal # 1 transmits an ACK # 1 packet to the server 50 (step S108), and performs processing for establishing a connection (not shown).

  Also, the transmitting unit 123 continues to repeatedly transmit the SYN # 1 packet to the server 50 via the communication unit 110 at predetermined time intervals (step S109). When receiving the SYN # 1 packet, the server 50 discards the SYN # 1 packet because the sequence number is identical to the response SYN packet. Also, the packet identification unit 122 transmits the SYN / ACK packet # 1 to the buffer management unit 124 (step S110).

  The packet management unit 124 deletes from the buffer the SYN # 1 packet whose sequence number matches the SYN / ACK packet # 1. Thereafter, as the SYN # 1 packet is deleted from the buffer, the transmitting unit 123 repeatedly transmits the SYN # 2 packet, which is the head packet of the buffer, to the server 50 via the communication unit 110 at predetermined time intervals (see FIG. Step S111).

  In addition, as illustrated in FIG. 4, the communication control apparatus 10 may repeatedly transmit SYN packets of a preset window size to the server 50 at predetermined time intervals. As shown in FIG. 4, the user terminal # 1 notifies the buffer management unit 124 of the SYN # 1 packet via the packet identification unit 122, and the user terminal # 2 buffers the SYN # 2 packet via the packet identification unit 122. It notifies the management unit 124 (steps S201 to S204).

  Then, the transmitting unit 123 (not shown) transmits the SYN packet for the window size from the buffer 131 to the server 50. In the example of FIG. 4, the window size is “2”, and the SYN # 1 packet and the SYN # 2 packet stored in the buffer 131 are repeatedly transmitted to the server 50 via the communication unit 110 at predetermined time intervals ( Step S205). As shown in the example of FIG. 4, when the number of connections has reached on the server 50 side and there are no free connections, the SYN # 1 packet and the SYN # 2 packet are discarded, but the connection is released. If there is a vacancy in the connection, the server 50 receives the SYN # 1 packet and the SYN # 2 packet (steps S206 and S207), and then identifies the SYN / ACK packet # 1 and the SYN / ACK packet # 2 as a packet identification unit. It transmits to 122 (steps S208 and S209).

  When the packet identification unit 122 receives the SYN / ACK packet # 1 and the SYN / ACK packet # 2, the packet identification unit 122 copies the SYN / ACK packet # 1 and the SYN / ACK packet # 2 to the user terminal # 1. The packet # 1 is transferred (step S210), and the SYN / ACK packet # 2 is transferred to the user terminal # 2 (step S211).

  Thereafter, the user terminal # 1 transmits an ACK # 1 packet to the server 50 (step S212), and the user terminal # 2 transmits an ACK # 2 packet to the server 50 (step S213), and establishes a connection, respectively. Process (not shown). Also, the buffer management unit 124 continues to repeatedly transmit the SYN # 1 packet and the SYN # 2 packet to the server 50 via the communication unit 110 at predetermined time intervals (steps S214 and S215). When receiving the SYN # 1 packet and the SYN # 2 packet, the server 50 discards the SYN # 1 packet and the SYN # 2 packet because the sequence number is identical to the response SYN packet.

  When buffer management unit 124 receives SYN / ACK packet # 1 and SYN / ACK packet # 2 from packet identification unit 122 (steps S216 and S217), SYN / ACK packet # 1 and SYN / ACK packet # 2 are received. The SYN # 1 packet with the matching sequence number and the SYN # 2 packet are deleted from the buffer 131.

  In this way, by providing the window size and repeatedly sending the SYN packet for the window size, it is possible to send SYN packets from different user terminals without waiting for an ACK, so when there are multiple vacant connections, the server The utilization efficiency of 50 can be improved.

(Effects of the first embodiment)
The communication control apparatus 10 of the communication control system according to the first embodiment receives a packet transmitted / received between a user terminal and a server establishing a connection using TCP on a network, and among the received packets, The SYN packet transmitted from the user terminal 20 to the server is distributed to the buffer 131. Then, the communication control device 10 repeatedly transmits the SYN packet stored in the buffer 131 to the server 50 at predetermined time intervals. Also, when the received packet satisfies the predetermined condition, the communication control device 10 discards the SYN packet stored in the buffer 131. Therefore, in the communication control system, it is possible to reduce the usage rate of the APL server or to take time to the connection probability without using the connection release rate.

  That is, the communication control apparatus 10 of the communication control system according to the first embodiment repeatedly transmits the SYN packet of the buffer 131. As a result, after the connection is released, a new connection can be established quickly, and server utilization efficiency can be improved.

Second Embodiment
In the first embodiment, the communication control apparatus 10 repeatedly transmits the SYN packet stored in the buffer 131 to the server 50 via the communication unit 110 at predetermined time intervals. In the communication control system of the second embodiment, the server 50A monitors the availability of the connection, and the connection notifies the communication control apparatus 10A of the availability. The communication control system of the second embodiment will be described below, but the description of the same configuration and processing as those of the first embodiment will be omitted.

  FIG. 5 is a diagram showing an example of the configuration of the communication control apparatus according to the second embodiment. The transmitting unit 123A of the control unit 120 controls transmission of the SYN packet stored in the buffer 131 to the server 50A based on the information notified by the server 50A. Specifically, when the number of connections with vacancy notified from the server 50A is one or more, the transmitting unit 123A transmits the SYN packet stored in the buffer 131 to the server 50A.

  FIG. 6 is a diagram showing an example of the configuration of the server according to the second embodiment. As shown in FIG. 6, the server 50A includes a communication unit 510, a control unit 520, and a storage unit 530. Communication unit 510 transmits and receives information transmitted via network 60.

  The control unit 520 controls processing of each unit of the server 50A. The control unit 520 can be configured by, for example, a CPU, an MPU, an ASIC, or the like. Control unit 520 includes monitoring unit 521A and notification unit 522A.

  The monitoring unit 521A monitors the state of the connection established by the server 50A. Specifically, the monitoring unit 521A monitors the open status of the connection of the server 50A every time a predetermined time elapses or when the connection is released, and specifies the number of connections with the open. In the following, a case will be described as an example in which the availability of the connection of the server 50A is monitored and the number of connections with the availability is specified every time a predetermined time elapses.

  When the state of the connection monitored by the monitoring unit 521A satisfies a predetermined condition, the notification unit 522A notifies information indicating whether or not the SYN packet can be accepted. Specifically, the notification unit 522A notifies the number of connections having a free space identified by the monitoring unit 521A.

  The storage unit 530 stores information used for processing of each unit in the server 50A and information generated as a result of the processing. Storage unit 530 may be, for example, a storage device such as a hard disk or an optical disk. The storage unit 530 may be a semiconductor memory such as a RAM or a flash memory.

(An example of a flow of communication control processing according to the second embodiment)
FIG. 7 is a sequence diagram showing an example of the flow of processing in the communication control system according to the second embodiment. As shown in FIG. 7, since the number of connections has reached the upper limit, the server 50A notifies the buffer management unit 124 that the free space is 0 (step S301). Also, the user terminal # 1 notifies the buffer management unit 124 of the SYN # 1 packet via the packet identification unit 122, and the user terminal # 2 notifies the buffer management unit 124 via the packet identification unit 122 of the SYN # 2 packet Then, the user terminal # 3 notifies the buffer management unit 124 of the SYN # 3 packet via the packet identification unit 122 (steps S302 to S307). The buffer management unit 124 stores the SYN # 1 packet, the SYN # 2 and the SYN # 3 packet identified by the packet identification unit 122 in the buffer 131.

  Thereafter, the server 50A notifies the buffer management unit 124 of the communication control apparatus 10A that the connection is released and the free space is 1 (step S308). When the communication control apparatus 10A receives that the vacancy is 1, the transmission unit 123A (not shown) transmits the SYN # 1 packet to the server 50A via the communication unit 110 (step S309), and the buffer management unit 124 deletes the SYN # 1 packet from the buffer 131.

  Then, the server 50A transmits the SYN / ACK packet # 1 to the packet identification unit 122 (step S310). When the packet identification unit 122 receives the SYN / ACK packet # 1, the packet identification unit 122 transfers the SYN / ACK packet # 1 to the user terminal # 1 (step S311). Thereafter, the user terminal # 1 transmits an ACK # 1 packet to the server 50A (step S312), and performs processing for establishing a connection (not shown).

  Thereafter, when one connection is released, the server 50A notifies the buffer management unit 124 of the communication control apparatus 10A that the free space is 1 (step S313), and when one more connection is released, The buffer management unit 124 of the communication control device 10A is notified that the free space is 2 (step S314).

  When the communication control apparatus 10A receives that the vacancy is 2, the transmission unit 123A transmits the SYN # 2 packet to the server 50A via the communication unit 110 (step S315), and the buffer management unit 124 transmits the SYN # 2 packet. The two packets are deleted from the buffer 131, and then the SYN # 3 packet is transmitted to the server 50A (step S316), and the buffer management unit 124 deletes the SYN # 3 packet from the buffer 131.

  Thereafter, similarly, the server 50A transmits the SYN / ACK packet # 2 and the SYN / ACK packet # 3 to the packet identification unit 122 (steps S317 and S318), and performs processing of establishing a connection (not shown).

  In the example of FIG. 7, since the communication control apparatus 10A deletes the SYN packet from the buffer 131 immediately after transmitting it, it can not be retransmitted if a packet loss occurs despite transmitting the SYN packet to the APL to the server 50A. . For this reason, when a packet loss occurs, an opportunity for the user terminal to establish a connection may be after the next packet retransmission and the time required for establishing the connection of the user terminal may increase. Therefore, as shown in FIG. 8, the connection may be monitored based on the SYN / ACK packet, and if the connection can be established, the SYN packet may be deleted from the buffer.

  As illustrated in FIG. 8, since the number of connections has reached the upper limit, the server 50A notifies the buffer management unit 124 that the free space is 0 (step S401). Also, the user terminal # 1 notifies the buffer management unit 124 of the SYN # 1 packet via the packet identification unit 122, and the user terminal # 2 notifies the buffer management unit 124 via the packet identification unit 122 of the SYN # 2 packet (Steps S402 to S405). When the buffer management unit 124 receives the SYN # 1 packet and the SYN # 2 packet identified by the packet identification unit 122, the buffer management unit 124 stores the packets in the buffer 131.

  Thereafter, the server 50A notifies the buffer management unit 124 of the communication control apparatus 10A that the connection is released and the free space is 1 (step S406). When the communication control device 10A receives that the free space is 1, the transmission unit 123 transmits the SYN # 1 packet to the server 50A via the communication unit 110 (step S407). Here, in the example of FIG. 8, it is assumed that the SYN # 1 packet is lost.

  Therefore, the server 50A again notifies the buffer management unit 124 of the communication control apparatus 10A that the free space is 1 (step S408). When the communication control device 10A receives that the vacancy is 1, the transmission unit 123 transmits the SYN # 1 packet again to the server 50A via the communication unit 110 (step S409).

  Then, the server 50A transmits the SYN / ACK packet # 1 to the packet identification unit 122 (step S410). When receiving the SYN / ACK packet # 1, the packet identification unit 122 copies the SYN / ACK packet # 1 and transfers the SYN / ACK packet # 1 to the user terminal # 1 (step S411). Thereafter, the user terminal # 1 transmits an ACK # 1 packet to the server 50A (step S412), and performs a process of establishing a connection (not shown).

  Also, the packet identification unit 122 transmits the SYN / ACK packet # 1 to the buffer management unit 124 (step S413). The packet management unit 124 deletes from the buffer the SYN # 1 packet whose sequence number matches the SYN / ACK packet # 1.

(Effect of the second embodiment)
In the communication control system according to the second embodiment, the server 50A monitors the availability of connection of the server, identifies the number of connections with the availability, and specifies the number of connections with the identified availability to the communication control device 10A. When the number of connections with notification and the number of vacant connections notified is one or more, the SYN packet stored in the buffer 131 is transmitted to the server 50A. As a result, new connections can be established quickly while preventing SYN packet transmission while there are no connections available, and server utilization efficiency can be improved.

Third Embodiment
In the second embodiment, the server 50A monitors the availability of the connection, and the connection notifies the communication control apparatus 10A of the availability. In the communication control system of the third embodiment, the server 50B monitors the number of connections established by the server 50B, and if it is determined that the number of connections has reached the upper limit, it receives a SYN packet. Make a backoff notification indicating that there is no The communication control system of the third embodiment will be described below, but the description of the same configuration and processing as those of the first and second embodiments will be omitted.

  FIG. 9 is a diagram showing an example of the configuration of the communication control apparatus according to the third embodiment. When the transmission unit 123B of the control unit 120 receives the notification indicating that the SYN packet is not received from the notification unit, the transmission unit 123B transmits the buffer after the time of the timer value set in the backoff notification transmitted from the server 50B passes. The SYN packet stored in 131 is transmitted to the server 50B.

  FIG. 10 is a diagram showing an example of the configuration of a server according to the third embodiment. The monitoring unit 521B of the server 50B monitors the number of connections established by the server 50B, and determines whether the number of connections has reached the upper limit.

  The notification unit 522B is a notification indicating that the SYN packet is not accepted when the monitoring unit 521B determines that the number of connections has reached the upper limit, and a backoff notification in which the timer value is set To notify.

(An example of a flow of communication control processing according to the third embodiment)
FIG. 11 is a sequence diagram showing an example of the flow of processing in the communication control system according to the third embodiment. As shown in FIG. 11, the user terminal # 1 notifies the buffer management unit 124 of the SYN # 1 packet via the packet identification unit 122, and the user terminal # 2 buffers the SYN # 2 packet via the packet identification unit 122. The management unit 124 is notified, and the user terminal # 3 notifies the buffer management unit 124 of the SYN # 3 packet via the packet identification unit 122 (steps S501 to S506). The buffer management unit 124 stores the SYN # 1 packet, the SYN # 2 packet, and the SYN # 3 packet identified by the packet identification unit 122 in the buffer 131.

  Thereafter, the transmitting unit 123B (not shown) transmits the SYN # 1 packet to the server 50B via the communication unit 110 (step S507), and the buffer managing unit 124 deletes the SYN # 1 packet from the buffer 131. .

  After that, the server 50B notifies the communication control apparatus 10B of the back-off notification in which the connection reaches the upper limit and 1 millisecond is set as the timer value (step S508), and the SYN / ACK packet # 1 is identified by the packet identification unit It transmits to 122 (step S509). When the packet identification unit 122 receives the SYN / ACK packet # 1, the packet identification unit 122 transfers the SYN / ACK packet # 1 to the user terminal # 1 (step S510). Thereafter, the user terminal # 1 transmits an ACK # 1 packet to the server 50B (step 511), and performs processing for establishing a connection (not shown).

  After that, after the time of the timer value set in the backoff notification (1 millisecond in the example of FIG. 11) of the communication control device 10B has passed, the transmitting unit 123B transmits the SYN # 2 packet via the communication unit 110. The buffer management unit 124 deletes the SYN # 2 packet from the buffer 131, and then transmits the SYN # 3 packet to the server 50B (step S513). 124 deletes the SYN # 3 packet from the buffer 131.

  Thereafter, similarly, the server 50B transmits the SYN / ACK packet # 2 and the SYN / ACK packet # 3 to the packet identification unit 122 (steps S514 and S515), and performs processing of establishing a connection (not shown).

  In the example of FIG. 11, since the communication control device 10B deletes the SYN packet from the buffer 131 immediately after transmitting the SYN packet, the SYN packet transmitted after the connection of the server 50B reaches the upper limit and before the backoff notification is the server It is destroyed at 50B side. Therefore, the time required for establishing a connection of the user terminal may increase. Therefore, as shown in FIG. 12, the connection may be monitored based on the SYN / ACK packet, and if the connection can be established, the SYN packet may be deleted from the buffer. After receiving the backoff notification, the buffer management unit 124 resumes transmission from the head packet of the buffer when the backoff timer value time has elapsed.

  As illustrated in FIG. 12, the user terminal # 1 notifies the buffer management unit 124 of the SYN # 1 packet via the packet identification unit 122, and the user terminal # 2 via the packet identification unit 122 of the SYN # 2 packet. The buffer management unit 124 is notified, and the user terminal # 3 notifies the buffer management unit 124 of the SYN # 3 packet via the packet identification unit 122 (steps S601 to S606). The buffer management unit 124 stores the SYN # 1 packet, the SYN # 2 packet, and the SYN # 3 packet identified by the packet identification unit 122 in the buffer 131.

  Thereafter, the transmitting unit 123 transmits the SYN # 1 packet and the SYN # 2 packet to the server 50B via the communication unit 110 (steps S607 and S608), and the buffer managing unit 124 transmits the SYN # 1 packet from the buffer 131. delete.

  Thereafter, the server 50B notifies the communication control apparatus 10B of the back-off notification in which the connection reaches the upper limit and 1 millisecond is set as the timer value (step S609), and the SYN / ACK packet # 1 is identified by the packet identification unit It transmits to 122 (step S610). Upon receiving the SYN / ACK packet # 1, the packet identification unit 122 copies the SYN / ACK packet # 1 and transfers the SYN / ACK packet # 1 to the user terminal # 1 (step S611). Thereafter, the user terminal # 1 transmits an ACK # 1 packet to the server 50B (step 612), and performs processing for establishing a connection (not shown).

  Also, the packet identification unit 122 transmits the SYN / ACK packet # 1 to the buffer management unit 124 (step S613). The packet management unit 124 deletes from the buffer the SYN # 1 packet whose sequence number matches the SYN / ACK packet # 1.

  Thereafter, after the time of the timer value set in the backoff notification (1 millisecond in the example of FIG. 12) has elapsed, the transmission unit 123 transmits the SYN # 1 packet and the SYN # 2 packet, It transmits to the server 50B via the communication unit 110 (steps S614 and S615). Thereafter, similarly, the server 50B transmits the SYN / ACK packet # 2 and the SYN / ACK packet # 3 to the packet identification unit 122 (steps S616 and S617), and performs processing of establishing a connection (not shown).

(Effect of the third embodiment)
In the communication control system according to the third embodiment, the server 50B monitors the number of connections established by the server, determines whether the number of connections has reached the upper limit, and the number of connections has reached the upper limit. If it is determined that the notification is a notification indicating that the SYN packet can not be received, a back-off notification in which a timer value is set is notified. Then, when the communication control device 10B receives the backoff notification indicating that the SYN packet is not received, the communication control device 10B transmits the SYN packet stored in the buffer 131 to the server after passing the time of the timer value set in the notification. Send to 50B. Therefore, in the communication control system according to the third embodiment, the server 30B notifies the backoff when the number of connections reaches the upper limit, and the communication control device 10B includes the backoff timer included in the backoff notification. Wait for the value. As a result, the communication control device 10B can transmit a packet without waiting for a notification from the server 50B, so that the efficiency decrease can be suppressed.

(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 disposed on the network as independent devices. Also, the packet identification unit and the buffer management unit may be incorporated into the server. Similarly, the reception unit and the transmission unit may be independent devices, 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 provided in the communication control apparatus may be disposed on the communication path between the server and the information processing apparatus establishing a connection using TCP.

  For example, FIG. 13 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. Communication control system 1B shown in FIG. 13 is different from communication control system 1A shown in FIG. 1 in the arrangement of functional units included in the communication control apparatus. In the other points, the communication control system 1B shown in FIG. 13 is the same as the communication control system 1A shown in FIG.

  In the first to third embodiments, it has been described that the receiving unit, the packet identifying unit, the transmitting unit, and the buffer managing unit are disposed 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. 13, the packet identification device 11 is connected between the user terminals 20A to 20D and the server 50 via the networks 40 and 60. Then, the packet identification device 11 is connected to the packet buffer device 13 provided with the buffer 12.

  The packet identification device 11 is a device that can execute the functions of the reception unit 121, the packet identification unit 122, and the transmission units 123, 123A, and 123B according to the first to third embodiments. The packet identification device 11 can be configured, for example, by a router or the like. The packet identification unit 11 identifies the SYN packet and transmits it to the packet buffer unit 13. The packet identification unit 11 identifies and mirrors the ACK packet, and transmits the mirrored ACK packet to the packet buffer unit 13.

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

  The packet buffer device 13 is a device capable of executing the function of the buffer management unit 124 according to the first to third embodiments. The packet buffer device 13 may be incorporated into the server 50, for example, or may be an independent device from the server.

  Thus, each function of the communication control devices 10 to 10B can be implemented by being implemented on different devices. Also, part of the functions of the communication control apparatuses 10 to 10B may be implemented in an existing apparatus such as an APL server. Although the packet buffer device 13 includes the buffer 12 in the example of FIG. 13, the buffer 12 may be provided on a device different from the packet buffer device 13 and connected to the packet buffer device 13. it can.

(program)
In addition, 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 computer executable language. For example, it is also possible to create a communication control program in which the processing executed by the communication control device according to the embodiment is described in a language that can be executed by a computer. In this case, when the computer executes the communication control program, the same effect as that of the above embodiment can be obtained. Furthermore, even if the communication control program is recorded in a computer readable recording medium, and the communication control program recorded in the recording medium is read and executed by the computer, the same processing as the above embodiment can be realized. Good.

  FIG. 15 is a diagram showing a computer 1000 that executes a communication control program. As illustrated in FIG. 15, the computer 1000 has, 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, for example, a boot program such as a 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, for example, a mouse 1051 and a keyboard 1052 as illustrated in FIG. The video adapter 1060 is connected to, for example, the display 1061 as illustrated in FIG.

  Here, as illustrated in FIG. 15, 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 described above is stored in, for example, the hard disk drive 1031 as a program module in which an instruction to be executed by the computer 1000 is described.

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

  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 by the CPU 1020 via the disk drive or the like. It is also good. Alternatively, the program module 1093 and the program data 1094 related to the communication control program may be stored in another computer connected via a network (LAN, WAN, etc.) and read by the CPU 1020 via the network interface 1070. .

  Of the processes described in the present embodiment, all or part of the process described as being automatically performed may be manually performed, or the process described as being performed manually. All or part of them can be automatically performed by a known method. In addition to the above, the processing procedures, control procedures, specific names, and information including various data and parameters shown in the above documents and drawings can be arbitrarily changed unless otherwise specified.

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

10, 10A, 10B Communication control devices 20A, 20B, 20C, 20D User terminals 30 AP
40, 60 network 50, 50A, 50B server 110, 510 communication unit 120, 520 control unit 121 reception unit 122 packet identification unit 123, 123A, 123B transmission unit 124 buffer management unit 130, 530 storage unit 131 buffer 521, 521A, 521B Monitoring unit 522, 522A, 522B notification unit

Claims (7)

A receiver configured to receive a packet transmitted and received between a user terminal and a server establishing a connection using TCP on a network;
Among the packets received by the reception unit, a packet identification unit that distributes, to a buffer, an SYN packet transmitted from the user terminal to the server;
A monitoring unit that monitors the open status of the connection established by the server or the number of connections established by the server ;
A notification unit that notifies of information indicating whether or not a SYN packet can be accepted if the connection availability monitored by the monitoring unit or the number of connections satisfies a predetermined condition;
A transmitting unit configured to control transmission of a SYN packet stored in the buffer to the server based on the information notified by the notifying unit;
A buffer management unit that discards the SYN packet stored in the buffer when the packet received by the reception unit satisfies a predetermined condition;
A communication control system comprising: A receiver configured to receive a packet transmitted and received between a user terminal and a server establishing a connection using TCP on a network;
Among the packets received by the reception unit, a packet identification unit that distributes, to a buffer, an SYN packet transmitted from the user terminal to the server;
A monitoring unit that monitors the availability of connections on the server and identifies the number of connections that have the availability ;
A notification unit for notifying of the number of connections having a vacancy identified by the monitoring unit ;
A transmitter configured to transmit a SYN packet stored in the buffer to the server, when the number of connections with vacancy notified from the notification unit is one or more ;
A buffer management unit that discards the SYN packet stored in the buffer when the packet received by the reception unit satisfies a predetermined condition;
Communication control systems that comprising: a. A receiver configured to receive a packet transmitted and received between a user terminal and a server establishing a connection using TCP on a network;
Among the packets received by the reception unit, a packet identification unit that distributes, to a buffer, an SYN packet transmitted from the user terminal to the server;
Monitoring the number of connections the server is established, a monitoring unit for determining whether the number of connections has reached the upper limit,
A notification unit indicating that the SYN packet can not be received if the monitoring unit determines that the number of connections has reached the upper limit, and a notification unit notifies a notification in which a timer value is set ;
A transmitting unit that transmits a SYN packet stored in the buffer to the server after a lapse of time of a timer value set in the notification when a notification indicating that the SYN packet is not received from the notification unit is received. When,
A buffer management unit that discards the SYN packet stored in the buffer when the packet received by the reception unit satisfies a predetermined condition;
A communication control system comprising: The buffer management unit is configured such that among the packets received by the reception unit, the sequence number of the SYN / ACK packet transmitted from the server to the user terminal is the same as the sequence number of the SYN packet stored in the buffer The communication control system according to any one of claims 1 to 3 , wherein in the case, the SYN packet stored in the buffer is discarded. A communication control method for controlling communication between a user terminal and a server establishing a connection using TCP on a network, comprising:
A receiving step of receiving a packet transmitted and received between the user terminal and the server;
A packet identification step of allocating, to a buffer, an SYN packet transmitted from the user terminal to the server among the packets received by the reception step;
Monitoring the availability of connections established by the server or the number of connections established by the server ;
A notification step of notifying the buffer of information indicating whether or not it is possible to accept a SYN packet when the connection idle status monitored by the monitoring step or the number of connections satisfies a predetermined condition; ,
A transmitting step of controlling transmission of a SYN packet stored in the buffer to the server based on the information notified by the notifying step;
A buffer management step of discarding a SYN packet stored in the buffer when the packet received by the reception step satisfies a predetermined condition;
A communication control method characterized by including:   A communication control method for controlling communication between a user terminal and a server establishing a connection using TCP on a network, comprising:
  A receiving step of receiving a packet transmitted and received between the user terminal and the server;
  A packet identification step of allocating, to a buffer, an SYN packet transmitted from the user terminal to the server among the packets received by the reception step;
  Monitoring the availability of connections on the server, and monitoring the number of connections with the availability;
  A notification step of notifying the number of connections having a free space identified by the monitoring step;
  A transmitting step of transmitting a SYN packet stored in the buffer to the server, when the number of connections with vacancy notified from the notifying step is one or more;
  A buffer management step of discarding a SYN packet stored in the buffer when the packet received by the reception step satisfies a predetermined condition;
  A communication control method characterized by including:   A communication control method for controlling communication between a user terminal and a server establishing a connection using TCP on a network, comprising:
  A receiving step of receiving a packet transmitted and received between the user terminal and the server;
  A packet identification step of allocating, to a buffer, an SYN packet transmitted from the user terminal to the server among the packets received by the reception step;
  Monitoring the number of connections established by the server to determine whether the number of connections has reached an upper limit;
  A notification process indicating that the SYN packet can not be received when it is determined by the monitoring process that the number of connections has reached the upper limit, and a notification process for notifying a notification in which a timer value is set;
  A transmitting step of transmitting the SYN packet stored in the buffer to the server after a lapse of time of a timer value set in the notification when receiving a notification indicating that the SYN packet is not accepted from the notification step; When,
  A buffer management step of discarding a SYN packet stored in the buffer when the packet received by the reception step satisfies a predetermined condition;
  A communication control method characterized by including:

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