JP4627290B2 - Rate control method, server, and program using TCP - Google Patents

Description

  The present invention relates to a rate control method, server, and program using TCP (Transmission Control Protocol).

  The Internet is generalized as a communication line, and a user can connect to the Internet using a terminal such as a personal computer or a mobile phone. A server such as a WWW server is connected to the Internet, and the terminal can send and receive data to and from the server.

  When file data is transferred between a server and a terminal, a TCP / IP (Transmission Control Protocol / Internet Protocol) connection is usually set. TCP has a flow control function, a retransmission control function, a connection management function, a session multiplexing function, and the like.

  With regard to flow control, data transmission is controlled according to the reception buffer size of the counterpart apparatus using the reception window size rwnd included in the TCP header. This suppresses variations in throughput between connections and avoids unnecessary flow control. For example, there is a technique for adaptively changing the TCP window size (for example, see Patent Documents 1 and 2) and a technique for performing congestion control by a router (for example, see Patent Document 3).

JP 2005-244517 A JP 2006-14329 A Japanese Patent Laid-Open No. 2002-314592

  However, the technique described in the above-described patent document is only rate control for each connection, and is not intended for rate control between a plurality of terminals and one server.

  On the other hand, for rate control between a huge number of terminals and one server, it is difficult for the server to process a large amount of traffic unless rate control is operated effectively on the terminal side. In addition, it is necessary to avoid a processing load on a lot of traffic from a specific terminal on the server.

  Therefore, the present invention reduces the congestion load state due to the concentration of a large amount of traffic on a server that communicates with a large number of terminals as much as possible, and can ensure the fairness of resource usage between terminals. It is an object to provide a control method, a server, and a program.

According to the present invention, when a plurality of terminals has established a TCP connection for one server, the rate control method of a server for controlling a rate of data from the terminal,
When the server establishes a connection from each terminal, it sets the maximum receive buffer size max-buffsz per connection according to the amount of memory available for the server,
A first step in which the server measures the line bandwidth BandWidth and the number of connected connections NumConncetions;
The server calculates the rate Rate obtained by dividing the line bandwidth BandWidth by the number of connected connections NumConncetions, and calculates the calculation window size kwnd (= Rate × RTT, RTT: transfer delay time) based on the rate Rate 2nd And the steps
The server measures the free receive buffer size buffsz that is less than or equal to the maximum receive buffer size max-buffsz by receiving data from the terminal, and the calculated window size kwnd when the calculated window size kwnd is smaller than the free receive buffer size buffsz a third step of determining a receive window size rwnd the
Server, a receive window size rwnd TC P f header to include acknowledgment ACK to (Acknowledge), a fourth step of transmitting to the terminal
Have
The terminal is characterized by ensuring fair use of resources of the server in each terminal by controlling the data transmission rate according to the reception window size included in the acknowledgment ACK .

According to the present invention, when a plurality of terminals has established a TCP connection for one server, the server that controls the transmission rate of data from the terminal,
When establishing a connection from each terminal, set the maximum receive buffer size max-buffsz per connection according to the amount of memory available for the server,
Load state measuring means for measuring the line bandwidth BandWidth and the number of connected connections NumConncetions ;
A window size calculation means for calculating a rate Rate obtained by dividing the line bandwidth BandWidth by the number of connected connections NumConncetions, and calculating a calculation window size kwnd (= Rate × RTT, RTT: transfer delay time) based on the rate Rate ; ,
Measure the free receive buffer size buffsz that is less than the maximum receive buffer size max-buffsz by receiving data from the terminal, and if the calculated window size kwnd is smaller than the free receive buffer size buffsz, calculate the calculated window size kwnd A receiving window size determining means for determining the size as rwnd ;
The receive window size rwnd generates an acknowledge ACK, including the TC P f header, the acknowledgment generating means to be transmitted to the terminal
Have
The terminal is characterized by ensuring fair use of resources of the server in each terminal by controlling the data transmission rate according to the reception window size included in the acknowledgment ACK .

According to the present invention, when a plurality of terminals has established a TCP connection for a single server, in a program that causes a onboard computer to a server for controlling a rate of data from the terminal,
When establishing a connection from each terminal, set the maximum receive buffer size max-buffsz per connection according to the amount of memory available for the server,
Load state measuring means for measuring the line bandwidth BandWidth and the number of connected connections NumConncetions ;
A window size calculation means for calculating a rate Rate obtained by dividing the line bandwidth BandWidth by the number of connected connections NumConncetions, and calculating a calculation window size kwnd (= Rate × RTT, RTT: transfer delay time) based on the rate Rate ; ,
Measure the free receive buffer size buffsz that is less than the maximum receive buffer size max-buffsz by receiving data from the terminal, and if the calculated window size kwnd is smaller than the free receive buffer size buffsz, calculate the calculated window size kwnd A receiving window size determining means for determining the size as rwnd ;
The receive window size rwnd generates an acknowledge ACK, including the TC P f header, the acknowledgment generating means to be transmitted to the terminal
Make your computer work,
The terminal is characterized by ensuring fairness of resource usage of the server in each terminal by controlling the data transmission rate according to the reception window size included in the acknowledgment ACK .

  According to the rate control method, server, and program of the present invention, the congestion load state due to the concentration of a large amount of traffic is reduced as much as possible on a server that communicates with a large number of terminals, and the fairness of resource utilization between terminals Can be secured.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  First, TCP flow control using window control will be briefly described. According to the window control, data having a window size (number of bytes) can be continuously transmitted without receiving an acknowledgment ACK from the receiving device. By receiving the acknowledgment ACK from the receiving device, the transmitting device slides the window by the amount that the reception is confirmed (sliding window size).

  For data transmission in TCP, two windows of “reception window size rwnd (Receive Windows Size)” and “congestion window size cwnd (Congestion Windows Size)” are used.

  The “reception window size” rwnd is transmitted from the reception device to the transmission device by an acknowledgment ACK, and represents an empty reception buffer size buffsz of the reception device. When the free reception buffer size buffsz of the reception device decreases, the reception device decreases the reception window size rwnd transmitted to the transmission device. According to the present invention, the reception window size rwnd included in the confirmation response ACK further reflects the congestion load state with respect to the empty reception buffer size buffsz.

  The “congestion window size” cwnd is determined by the transmission device, and is not transmitted to the reception device. The congestion window size is controlled based on the reception status of the acknowledgment ACK, and is calculated by various calculation methods depending on the TCP version.

  The data size that can be actually transmitted without the confirmation response is the smaller data size by comparing the “reception window size” received by the confirmation response ACK with the calculated “congestion window size”.

  For data reception in TCP, a maximum reception buffer size max-buffsz per connection is set when a connection is established. The maximum reception buffer size max-buffsz is a fixed value set in advance according to the amount of memory available to the server. Further, the maximum reception buffer size max-buffsz is not changed after the connection is established. Therefore, the empty reception buffer size buffsz does not exceed the maximum reception buffer size max-buffsz. That is, the reception window size rwnd included in the header of the acknowledgment ACK does not exceed the maximum reception buffer size buffsz.

  FIG. 1 is a system configuration diagram according to the present invention.

  The server 1 transmits and receives data to and from a plurality of terminals 2 using a TCP connection established via the Internet 3.

  First, the functional configuration of the server 1 will be described. The server 1 includes a content storage unit 100, a rate controllable data transmission unit 111, a data reception unit 121, a congestion load state measurement unit 101, a window size calculation unit 102, a congestion window size derivation unit 112, 1 transmission window size determination unit 113, second transmission window size determination unit 114, confirmation response generation unit 122, and reception window size determination unit 123. These functional units can also be realized by executing a program that causes a computer mounted on the server to function.

  The content storage unit 100 stores content data. In response to the request notified from the data reception unit 121, the content data is notified to the data transmission unit 111.

  The data transmission unit 111 transmits data to the terminal 2 and receives an acknowledgment ACK in response thereto. In addition, when the data transmission unit 111 receives the confirmation response ACK, the data transmission unit 111 acquires the reception window size rwnd from the received response. The reception window size rwnd is notified to the second transmission window size determination unit 114.

  The data receiving unit 121 receives data from the terminal 2 and returns an acknowledgment ACK in response thereto. The data reception unit 121 notifies the received data to the content storage unit 100 and notifies the reception window size determination unit 123 of the current empty reception buffer size buffsz.

The congestion load state measurement unit 101 monitors the data transmission unit 111 and the data reception unit 121 and measures a congestion load state due to access from a plurality of terminals 2. Congestion load conditions, the times line bandwidth BandWidth [bit / s], a rate Rate divided by the number of connections NumConncetions in connection.

The window size calculation unit 102 calculates a calculated window size kwnd by the following formula based on the congestion load state. The calculated window size kwnd represents the window size that can be used per connection, and ensures the fairness of resource usage between terminals.
kwnd [byte] = Rate [bit / s] × RTT [s] / 8
Rate [bit / s] = BandWidth [bit / s] / NumConncetions
RTT: Transfer delay value [second] observed at connection establishment or after establishment
The calculated window size kwnd is notified to the first transmission window size determination unit 113 for data transmission and to the reception window size determination unit 123 for data reception.

  The reception window size determination unit 123 receives the calculated window size kwnd from the window size calculation unit 102 and the empty reception buffer size buffsz from the data reception unit 121. Then, the reception window size determination unit 123 compares the calculated window size kwnd and the empty reception buffer size buffsz, and determines the smaller size as the reception window size rwnd. The determined reception window size rwnd is notified to the confirmation response generation unit 122.

  The empty reception buffer size buffsz does not exceed the maximum reception buffer size max-buffsz set when the connection is established. Accordingly, the reception window size rwnd also does not exceed the maximum reception buffer size max-buffsz. Furthermore, according to the present invention, the reception window size rwnd does not exceed the empty reception buffer size buffsz. That is, the characteristic function of the present invention is effective only when the calculation window size kwnd is smaller than the empty reception buffer size buffsz. Only in this case, the reception window size rwnd in normal TCP is different from the reception window size rwnd (= calculation window size kwnd) in the present invention.

  The confirmation response generation unit 122 includes the reception window size rwnd in the TCP header of the confirmation response ACK. The generated confirmation response ACK is notified to the data reception unit 121 and transmitted to the terminal 2. Thereby, the terminal 2 controls the transmission rate of data to the server 1 according to the reception window size rwnd of the TCP header in the received acknowledgment ACK.

  FIG. 2 shows a TCP header format. The bits of the acknowledgment ACK and the reception window size rwnd are shown.

  The congestion window size deriving unit 112 calculates a TCP congestion window size cwnd. The congestion window size cwnd is calculated by various calculation methods depending on the TCP version.

  The first transmission window size determining unit 113 compares the calculated window size kwnd output from the window size calculating unit 102 with the congestion window size cwnd output from the congestion window size deriving unit 112. The smaller size is set as the first transmission window size wnd1. The determined first transmission window size wnd1 is notified to the second transmission window size determination unit 114.

  The second transmission window size determination unit 114 compares the reception window size rwnd notified from the data transmission unit 111 with the first transmission window size wnd1. The smaller size is set as the second transmission window size wnd2. The determined second transmission window size wnd2 is notified to the data transmission unit 111. The data transmission unit 111 controls the data transmission rate according to the second transmission window size wnd2.

  Next, the functional configuration of the terminal 2 will be described. The terminal 2 includes a data transmission unit 21 and a data reception unit 22 that are capable of rate control. These functional units can also be realized by executing a program that causes a computer installed in the terminal to function.

  The data transmission unit 21 transmits data to the server 1 and receives an acknowledgment ACK in response thereto. In addition, when the data transmission unit 21 receives the confirmation response ACK, the data transmission unit 21 acquires the reception window size rwnd from the received response. The data transmission rate is controlled according to the reception window size rwnd.

  The data receiving unit 22 receives data from the terminal 2 and sends back an acknowledgment ACK in response thereto. The data receiving unit 22 includes the reception window size rwnd calculated according to the congestion load state and the empty buffer size in the TCP header of the confirmation response ACK, and transmits the confirmation response ACK.

  FIG. 3 is a sequence diagram in the present invention.

  First, rate control of data transmitted from the terminal 2 to the server 1 will be described.

(S301) A connection is established between the terminal 2 and the server 1. When establishing a TCP connection, a three-way handshake is performed by exchanging SYNs. The server 1 measures the transfer delay value RTT at the time of establishing the connection and thereafter for data transmission / reception. Since the reception buffer at the time of establishing the connection is empty, the empty reception buffer size buffsz is inevitably determined as the maximum reception buffer size max-buffsz. According to FIG. 3, for example, the maximum reception window size max-buffsz of the server 1 is determined to be 500 bytes.

(S302) The terminal 2 transmits 400-byte data having a reception window size of 500 bytes or less to the server 1 using the sequence number 6001.
(S303) Since the server 1 has received 400 bytes of the reception window size of 500 bytes, the remaining reception buffer size is 100 bytes. The server 1 returns an acknowledgment ACK with the sequence number 6401 and the reception window size rwnd = 100 Bytes to the terminal 2.
(S304) The terminal 2 transmits 100 bytes of data out of the reception window size of 100 bytes to the server 1 using the sequence number 6401.
(S305) Since the server 1 has received 100 bytes of the reception window size of 100 bytes, the remaining reception buffer size is 0 bytes. The server 1 returns a confirmation response ACK with the confirmation sequence number 6501 and the reception window size rwnd = 0 Byte to the terminal 2.

  Here, it is assumed that the congestion load state of the server 1 is increased compared to when the connection is established. As an increase in the congestion load state, for example, the number of terminals connected to the server 1 may increase.

  The server 1 calculates the calculation window size kwnd for the terminal 2 from the congestion load state (line bandwidth BandWidth [bit / s], the number of connected connections NumConncetions). For example, it is assumed that the calculated window size kwnd = 300 bytes. In addition, it is assumed that the server 1 has completed the reception process for the previously received data. Then, the calculated window size kwnd = 300 Byte is compared with the maximum reception buffer size max-buffsz = 500 Byte, and the smaller 300 Byte is updated as the reception window size rwnd.

(S306) The server 1 transmits to the terminal 2 a confirmation response ACK having the confirmation sequence number 6501 and the reception window size rwnd = 300 bytes. Thereby, the terminal 2 transmits data to the server 1 again.

  Next, rate control of data transmitted from the server 1 to the terminal 2 will be described.

(S311) The server 1 transmits data to the terminal 2. At this time, the server 1 calculates the calculation window size kwnd for the terminal 2 from the congestion load state (line bandwidth BandWidth [bit / s], the number of connected connections NumConncetions). On the other hand, the server 1 derives a congestion window size cwnd.

  FIG. 4 is a graph of a general method for determining the congestion window size cwnd.

  The congestion window size is slow-started from the initial value 1 Byte, and when it is equal to or less than the threshold (congestion a), the congestion window size cwnd is increased exponentially. Here, the maximum congestion window size cwnd that can be transmitted without receiving the acknowledgment ACK is congestion a. When congestion a is reached and reception is confirmed by retransmission control thereafter and congestion is avoided, slow start is performed again, and the congestion window size cwnd is increased exponentially. When the congestion a / 2 is reached, the congestion window size cwnd increases linearly. The maximum congestion window size cwnd in the linear increase is congestion b (<congestion a). At this time, even if congestion is avoided, the congestion window size cwnd is reduced only to congestion b / 2. Then it increases again with a linear increase.

  Returning to S311 of FIG. 3, the calculated window size kwnd and the congestion window size cwnd are compared, and the smaller one is set as the first transmission window size wnd1.

(S312) The server 1 receives from the terminal 2 an acknowledgment ACK with a sequence number 6401 and a reception window size rwnd = 100. Here, the server 1 compares the reception window size rwnd with the first transmission window size wnd1, and sets the smaller size as the second transmission window size wnd2.

(S313) The server 1 controls the transmission rate according to the second transmission window size wnd2.

  As described above in detail, according to the rate control method, server, and program of the present invention, it is possible to reduce the congestion load state caused by a large amount of traffic concentrated on a server that communicates with a large number of terminals as much as possible. Therefore, it is possible to ensure the fairness of resource usage between terminals.

  The system of the present invention works particularly effectively on a communication / broadcasting cooperation system in which a viewer participation broadcast program is broadcast. Depending on the content of the broadcast program, there is a case where the terminal operated by the viewer is concentratedly accessed to a specific server in a certain time zone. In such a case, by applying the present invention, the rate control on the terminal side works effectively, and the congestion load state of the server is avoided.

  According to the various embodiments of the present invention described above, those skilled in the art can easily make various changes, modifications and omissions within the scope of the technical idea and the viewpoint of the present invention. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is a system configuration diagram in the present invention. It is a format of a TCP header. It is a sequence diagram in the present invention. It is a graph of the general determination method of congestion window size cwnd.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Server 100 Content storage part 101 Congestion load state measurement part 102 Window size calculation part 111 Data transmission part 112 Congestion window size derivation part 113 1st transmission window size determination part 114 2nd transmission window size determination part 121 Data reception part 122 Acknowledgment response Generation unit 123 Reception window size determination unit 2 Terminal 21 Data transmission unit 22 Data reception unit 3 Internet

Claims (3)

When a plurality of terminals has established a connection of TCP (Transmission Control Protocol) for the one server, the rate control method of a server for controlling a rate of data from the terminal,
When the server establishes a connection from each terminal, it sets the maximum receive buffer size max-buffsz per connection according to the amount of memory available for the server,
A first step in which the server measures a line bandwidth BandWidth and the number of connected connections NumConncetions;
The server calculates a rate Rate obtained by dividing the line bandwidth BandWidth by the number of connected connections NumConncetions, and calculates a calculation window size kwnd (= Rate × RTT, RTT: transfer delay time) based on the rate Rate. A second step of calculating;
When the server measures the free reception buffer size buffsz that is equal to or less than the maximum reception buffer size max-buffsz by receiving data from the terminal, and the calculation window size kwnd is smaller than the free reception buffer size buffsz A third step of determining the calculated window size kwnd as the reception window size rwnd ;
The server, a fourth step of transmitting the reception window size rwnd a TC P f header to include acknowledgment ACK (Acknowledge), to the terminal
Have
A rate control method characterized in that the terminal ensures fairness of resource use of the server in each terminal by controlling a data transmission rate according to a reception window size included in the acknowledgment ACK. . When a plurality of terminals has established a TCP connection for one server, the server that controls the transmission rate of the data from said terminal,
When establishing a connection from each terminal, set the maximum receive buffer size max-buffsz per connection according to the amount of memory available for the server,
Load state measuring means for measuring the line bandwidth BandWidth and the number of connected connections NumConncetions ;
The window size for calculating the rate Rate obtained by dividing the line bandwidth BandWidth by the number of connected connections NumConncetions and calculating the calculated window size kwnd (= Rate × RTT, RTT: transfer delay time) based on the rate Rate A calculation means;
By measuring the free reception buffer size buffsz that is equal to or less than the maximum reception buffer size max-buffsz by receiving data from the terminal, and the calculation window size kwnd is smaller than the free reception buffer size buffsz, the calculation window a receive window size determination means for determining a size kwnd as receive window size rwnd,
Generates an acknowledge ACK, including the reception window size rwnd the TC P f header, the acknowledgment generating means to be transmitted to the terminal
Have
The server, wherein the terminal ensures fair use of resources of the server in each terminal by controlling a data transmission rate according to a reception window size included in the confirmation response ACK . When a plurality of terminals has established a TCP connection for a single server, in a program that causes a computer mounted in a server for controlling a rate of data from the terminal,
When establishing a connection from each terminal, set the maximum receive buffer size max-buffsz per connection according to the amount of memory available for the server,
Load state measuring means for measuring the line bandwidth BandWidth and the number of connected connections NumConncetions ;
The window size for calculating the rate Rate obtained by dividing the line bandwidth BandWidth by the number of connected connections NumConncetions and calculating the calculated window size kwnd (= Rate × RTT, RTT: transfer delay time) based on the rate Rate A calculation means;
By measuring the free reception buffer size buffsz that is equal to or less than the maximum reception buffer size max-buffsz by receiving data from the terminal, and the calculation window size kwnd is smaller than the free reception buffer size buffsz, the calculation window a receive window size determination means for determining a size kwnd as receive window size rwnd,
Generates an acknowledge ACK, including the reception window size rwnd the TC P f header, the acknowledgment generating means to be transmitted to the terminal
Make your computer work,
For the server, the terminal ensures fairness of resource usage of the server in each terminal by controlling a data transmission rate according to a reception window size included in the acknowledgment ACK . program.

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