JP4828555B2 - Node device and bandwidth control method - Google Patents

Description

  The present invention relates to flow control in a system that transmits and receives data between terminals via a network.

  Generally, communication via a computer network such as the Internet is performed between terminals such as personal computers. Data such as a file is transferred by this communication. In this type of data transfer system, TCP (Transmission Control Protocol), which is a standard transport protocol, is often used as a transport layer protocol.

In data transfer, it may be required to transfer a large amount of data at high speed. In response to this, studies have been made to improve throughput by controlling the TCP window size to be constant (see, for example, Non-Patent Document 1).
“Examination of TCP flow rate control method in edge router”, IEICE General Conference, March 2007

  In TCP, bandwidth control that autonomously changes the window size according to packet discard is performed. However, in data transfer in a bandwidth guarantee network that restricts the inflow at the entrance of the network to prevent traffic exceeding the guaranteed bandwidth from entering the network, the throughput becomes sawtooth and the guaranteed bandwidth is reduced. There was a problem that it could not be fully utilized.

  Here, by modifying the TCP protocol described above, techniques for transmitting data at a constant throughput according to the guaranteed bandwidth and techniques for controlling the advertisement window size constant have measures against the above-described problems. .

  However, in TCP, there is a Nagle algorithm in which data smaller than the maximum segment size (hereinafter referred to as MSS) is not transmitted at the time of data transmission, and a delayed ACK in which a single ACK is returned for a plurality of data at the time of data reception. The algorithm is installed.

  For this reason, a delay due to the Nagle algorithm or the delayed ACK algorithm occurs, and the major premise of the above technology that “the data for the window size rewritten every measured round-trip propagation delay time (hereinafter referred to as RTT) is completed” is broken. Depending on the size of the window to be rewritten, there is a problem that the throughput is extremely lowered.

  Further, in the technique for controlling the advertisement window size to a constant value, when the scaling option is enabled in the TCP option, the bit shift is performed according to the scaling factor (hereinafter referred to as SF) in the scaling option, so that the rewriting is performed. Depending on the size of the window, there is a problem that the throughput is extremely reduced due to the influence of a rounding error due to bit shift.

  Accordingly, an object of the present invention is to provide a node device and a bandwidth that can efficiently use the guaranteed bandwidth and maintain a high throughput without depending on the RTT or the size of the guaranteed bandwidth in data transfer in the bandwidth guaranteed network. It is to provide a control method.

In order to achieve the above object, the node device of the present invention provides:
A node device arranged between the data transmitting terminal and the data receiving terminal in a bandwidth guaranteed network in which a band capable of transmitting data from the data transmitting terminal to the data receiving terminal is guaranteed;
A propagation delay time calculating unit for calculating a propagation delay time between the data transmitting terminal and the data receiving terminal;
Based on the guaranteed bandwidth allocated to the service target flow from the data transmitting terminal to the data receiving terminal in the bandwidth guaranteed network and the propagation delay time calculated by the propagation delay time calculating unit, the service target flow A window size calculation unit for calculating a window size in which the data is a bandwidth within the guaranteed bandwidth;
A window size writing unit for notifying the data transmission terminal to use the window size calculated by the window size calculation unit for bandwidth control of the data transmission terminal;
And an option control unit that rewrites an option in the SYN packet of the service target flow according to the window size calculated by the window size calculation unit.

  In the present invention configured as described above, MSS and SF, which are options in the SYN packet (a generic name of SYN and SYN / ACK packet), are controlled. These options are controlled according to a window size (hereinafter referred to as BGWND) calculated based on the RTT and guaranteed bandwidth between the data transmitting terminal and the data receiving terminal.

  The processing procedure is shown below.

Step 1: Calculation of BGWND The node device calculates BGWND based on the measured RTT and guaranteed bandwidth.

Step 2: Rewriting options in SYN and SYN / ACK packets The node device calculates MSS and SF based on the calculated BGWND, and rewrites MSS and SF existing in the SYN and SYN / ACK packets with the calculated values. Do.

  In the present invention, since the node device only controls the options in the SYN and SYN / ACK packets, the data transmitting terminal only performs an existing operation based on the option, and functions unique to the present invention in the protocol of the data transmitting terminal Throughput can be improved without adding.

  As described above, according to the present invention, there is no need to change the TCP protocol stack of the data transmission terminal when operating the bandwidth guarantee service using TCP, and the influence of the delay caused by the Nagle algorithm or delay ACK and the scaling option As a result, it is possible to improve throughput reduction due to the influence of rounding error of the advertising window and to stably control the throughput within the guaranteed bandwidth, so that the guaranteed bandwidth can be used efficiently.

  The best mode for carrying out the present invention will be described below.

  In general TCP, two windows, an advertisement window and a congestion window, are defined. The size of the advertisement window is determined on the receiving side depending on the state of the reception buffer. Also, the size of the congestion window is determined on the data transmission side according to the state of packet discard. As the window size used for flow control, the smaller one of the advertisement window size and the congestion window size is selected. This window size is updated when an ACK arrives.

  In the present embodiment, a band is guaranteed by a band guarantee network between a data transmission terminal serving as a data transmission side and a data reception terminal serving as a data reception side. Therefore, it is assumed that no packet is discarded as long as data is transmitted within the guaranteed bandwidth. Therefore, discarding packets can be prevented by adjusting the advertisement window size so that data is transmitted below the guaranteed bandwidth. If the packet discard does not occur, the congestion window size is not reduced. Therefore, the advertisement window size is always adopted as the TCP window size. As a result, the throughput does not fluctuate in a sawtooth shape, and the guaranteed bandwidth can be used efficiently.

  Therefore, in the present embodiment, between the data transmitting terminal and the data receiving terminal, the edge node as the node device is based on the propagation delay time between the data transmitting side and the data receiving side and the guaranteed bandwidth by the bandwidth guaranteed network. Then, the window size is calculated such that the data is transmitted within the guaranteed bandwidth, and the advertisement window size described in the ACK packet from the data receiving terminal to the data transmitting terminal is rewritten to the calculated window size value.

  As a result, the rate of data transmitted from the data transmitting terminal to the data receiving terminal can be stably controlled within the guaranteed bandwidth, so that the guaranteed bandwidth can be efficiently used.

  In addition, by rewriting MSS and SF existing in SYN and SYN / ACK according to BGWND, the effect of delay caused by Nagle algorithm and delayed ACK and the effect of rounding error of advertising window due to scaling option are improved. In addition, since the throughput can be stably controlled within the guaranteed bandwidth, the guaranteed bandwidth can be used efficiently.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a data transmission system using a node device according to an embodiment of the present invention.

  Referring to FIG. 1, the data transmission system according to the present embodiment includes a data transmission terminal 14, a data reception terminal 15, edge nodes 11 and 12 that are node devices, and a bandwidth management server (RACS) 13. ing.

  The data transmission terminal 14 is connected to the edge node 11, and the data reception terminal 15 is connected to the edge node 12. The edge node 11 and the edge node 12 can transmit and receive data on the bandwidth guarantee network 16. Thereby, the data from the data transmission terminal 14 is transferred to the data reception terminal 15 via the edge node 11 and the edge node 12.

  The bandwidth management server 13 is a device that centrally manages bandwidth information of all links of the bandwidth guarantee network 16. The bandwidth information includes information on the guaranteed bandwidth allocated to the link. The bandwidth management server 13 notifies the edge nodes 11 and 12 of bandwidth information of each link being managed. With bandwidth management by the bandwidth management server 13, a guaranteed bandwidth in the bandwidth guaranteed network 16 is secured for the link from the data transmission terminal 14 to the data reception terminal 15. As a result, as long as the data transmission terminal 14 transmits data below the guaranteed bandwidth, packet discard does not occur in the bandwidth guaranteed network 16. Further, the edge node 11 measures a round trip propagation delay time 17 between the data transmission terminal 14 and the data reception terminal 15.

  FIG. 2 is a block diagram showing a configuration of the edge node 11 shown in FIG.

  Referring to FIG. 2, the edge node 11 includes a data reception unit 21, a flow identification / distribution unit 22, a propagation delay time calculation unit 23, a data transmission unit 24, a band information holding unit 25, and a flow information holding unit. 26, a window size calculation unit 27, an advertisement window size writing unit 28, and an option control unit 29.

  The data reception unit 21 receives a packet such as a data packet or an ACK packet and sends the packet to the flow identification / distribution unit 22.

  The flow identification / distribution unit 22 guarantees the flow (service target flow) that is the target of the data transfer service that guarantees the bandwidth and the bandwidth based on the user information held together with the bandwidth information in the bandwidth information holding unit 25. The flow that is not the target of the data transfer service (service non-target flow) is identified. Further, the flow identification / distribution unit 22 distributes the ACK packet of the service target flow to the advertisement window size writing unit 28 through the route 22a, and transmits data of the packet of the non-service target flow and the data packet of the service target flow through the route 22c. And the SYN and SYN / ACK packets of the service target flow are distributed to the option control unit 29 through the route 22b.

  The propagation delay time calculation unit 23 measures the round-trip propagation delay time between the data transmission terminal 14 and the edge node 11 and between the edge node 11 and the data reception terminal 15.

  The bandwidth information holding unit 25 holds the bandwidth information of the service target user notified from the bandwidth management server 13 and user information (destination / source IP address, destination / source port number) in association with each other. The bandwidth information includes information on the guaranteed bandwidth allocated to the link. The link can be identified by user information.

  The flow information holding unit 26 holds the connection information of the service target flow identified by the flow identification / distribution unit 22 and the round trip propagation delay time calculated by the propagation delay time calculation unit 23 in association with each other.

  The window size calculation unit 27 includes a round-trip propagation delay time 17 between the data transmission terminal 14 and the data reception terminal 15 held in the flow information holding unit 26, and the band information held in the band information holding unit 25. A window size (BGWND) is calculated using the guaranteed bandwidth so that the data transmission bandwidth is within the guaranteed bandwidth.

  The advertisement window size writing unit 28 writes the window size value calculated by the window size calculating unit 27 in the window field of the ACK packet from the data receiving terminal 15 to the data transmitting terminal 14, and the ACK packet is sent to the data transmitting unit 24. Send to. The ACK packet is finally transferred to the data transmission terminal 14, and the window size value written in the window field of the ACK packet is used for bandwidth control at the data transmission terminal 14.

  The data transmission unit 24 transmits the packet from the flow identification / distribution unit 22 and the packet from the advertisement window size writing unit 28 to the edge node 12 or the data transmission terminal 14 via the bandwidth guarantee network 16.

  The option control unit 29 controls the MSS and the scaling option according to BGWND notified from the window size calculation unit 27 for the SYN and SYN / ACK packets transferred from the flow identification / distribution unit 22.

  Here, packet distribution by the flow identification / distribution unit 22 will be described in detail.

  FIG. 3 is a diagram for explaining packet distribution by the flow identification / distribution unit 22 shown in FIG.

  When a connection is established between the data transmission terminal 14 and the data reception terminal 15, data transfer is started. When receiving the ACK packet from the data receiving terminal 15, the flow identification / distribution unit 22 determines whether it is an ACK packet of the service target flow. If it is an ACK packet for the service target flow, the flow identification / distribution unit 22 sends the ACK packet to the advertisement window size writing unit 28 through the route 22a. Further, when receiving a SYN packet from the data transmission terminal 14 or a SYN / ACK packet from the data reception terminal 15, the flow identification / distribution unit 22 sends the SYN packet or SYN / ACK packet to the option control unit 29 through the route 22b. Send to. When receiving the service non-subscriber user packet or data packet, the flow identification / distribution unit 22 sends the service non-subscriber user packet or data packet to the data transmission unit 24 through the route 22c.

  FIG. 4 is a sequence diagram showing signal exchange between blocks when measuring the round-trip propagation delay time in the edge node 11 shown in FIG. In the following, it is assumed that the propagation delay time between the data transmission terminal 14 and the edge node 11 is small, and the round-trip propagation delay time between the edge node 11 and the data reception terminal 15 is the round-trip propagation delay time 17.

  Referring to FIG. 4, in the edge node 11 on the data transmission terminal 14 side, when the flow identification / distribution unit 22 observes the SYN packet from the data transmission terminal 14 (step 101), the flow identification / distribution unit 22 reciprocates along with the user information of the service target flow. A request to start measuring the propagation delay time 17 is sent to the propagation delay time calculation unit 23 (step 102). As a result, the propagation delay time calculation unit 23 starts measuring the round-trip propagation delay time 17.

  When the flow identification / distribution unit 22 observes the SYN / ACK packet from the data receiving terminal 15 for the SYN packet (step 103), the flow identification / distribution unit 22 sends a measurement end request for the round-trip propagation delay time 17 together with the user information to the propagation delay time. The data is sent to the calculation unit 23 (step 104). Thereby, the propagation delay time calculation unit 23 ends the measurement of the round-trip propagation delay time 17.

  After that, the propagation delay time calculation unit 23 that has finished measuring the round-trip propagation delay time 17 notifies the flow information holding unit 26 of the measured round-trip propagation delay time 17 together with the user information as a report of the round-trip propagation delay time 17 ( Step 105).

  FIG. 5 is a sequence diagram showing the exchange of signals between blocks when the window size is calculated in the edge node 11 shown in FIG.

  Referring to FIG. 5, when the flow information holding unit 26 receives the report of the round-trip propagation delay time 17 from the propagation delay time calculation unit 23 (step 201), the flow information holding unit 26 communicates with the data transmission terminal 14 and the window size calculation unit 27. A bandwidth guarantee window calculation request is notified together with the round-trip propagation delay time 17 with the data receiving terminal 15 and user information (step 202).

  Upon receiving the bandwidth guarantee window calculation request, the window size calculation unit 27 requests the guaranteed bandwidth corresponding to the user information from the bandwidth information holding unit 25 based on the user information (step 203).

  The bandwidth information holding unit 25 returns the guaranteed bandwidth in response to the guaranteed bandwidth value request from the window size calculating unit 27 (step 204).

  The window size calculation unit 27 that has received the round-trip propagation delay time 17 and the guaranteed bandwidth between the data transmitting terminal 14 and the data receiving terminal 15 sends the data within the guaranteed bandwidth based on these values. The window size to be calculated is calculated (step 205). At this time, a window size such that data is transmitted at a rate that matches the guaranteed bandwidth is preferable.

  The window size can be obtained by, for example, equation (1).

  FIG. 6 is a sequence diagram showing exchange of signals between blocks at the time of advertising window writing and MSS / SF writing in the edge node 11 shown in FIG.

  Referring to FIG. 6, first, the window size calculation unit 27 calculates the window size of the service target flow (step 301). Subsequently, the window size calculation unit 27 notifies the calculated window size and the user information of the service target flow to the advertisement window size writing unit 28 (step 302). The advertisement window size writing unit 28 writes the window size value notified from the window size calculation unit 27 in the window field of the ACK packet from the flow identification / distribution unit 22 (step 303). The ACK packet in which the advertisement window size is written by the advertisement window size writing unit 28 is sent to the data transmission unit 24.

  Subsequently, the window size calculation unit 27 notifies the option control unit 29 of the calculated window size and the user information (step 304). The option control unit 29 specifies the SYN / ACK packet from the data receiving terminal 15 to be controlled based on the user information, and rewrites the MSS and SF in the option in the SYN / ACK packet (step 305).

  The MSS calculated based on the window size can be obtained, for example, as an integer when n is minimum in Equation (2). Moreover, SF can be calculated | required as a minimum integer which satisfy | fills Formula (3), for example.

  In FIG. 6, the SYN / ACK packet from the data receiving terminal 15 is the control target, but the MSS and SF rewriting method when the SYN packet from the data transmitting terminal 14 is the control target is the same as described above. is there.

It is a block diagram which shows the structure of the data transmission system using the node apparatus of one Embodiment of this invention. It is a block diagram which shows the structure of the edge node shown in FIG. It is a figure for demonstrating packet distribution by the flow identification and distribution part shown in FIG. FIG. 3 is a sequence diagram showing exchange of signals between blocks when measuring round-trip propagation delay time in the edge node shown in FIG. 2. FIG. 3 is a sequence diagram showing exchange of signals between blocks when calculating a window size in the edge node shown in FIG. 2. FIG. 3 is a sequence diagram showing exchange of signals between blocks at the time of advertisement window rewriting and option control in the edge node shown in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 12 Edge node 13 Band management server 14 Data transmission terminal 15 Data reception terminal 16 Band guarantee network 17 Round-trip propagation delay time 21 Data reception part 22 Flow identification and distribution part 23 Propagation delay time calculation part 24 Data transmission part 25 Band information holding | maintenance 26 Flow information holding unit 27 Window size calculating unit 28 Advertising window size writing unit 29 Option control unit

Claims (6)

A node device arranged between the data transmitting terminal and the data receiving terminal in a bandwidth guaranteed network in which a band capable of transmitting data from the data transmitting terminal to the data receiving terminal is guaranteed;
A propagation delay time calculating unit for calculating a propagation delay time between the data transmitting terminal and the data receiving terminal;
Based on the guaranteed bandwidth allocated to the service target flow from the data transmitting terminal to the data receiving terminal in the bandwidth guaranteed network and the propagation delay time calculated by the propagation delay time calculating unit, the service target flow A window size calculation unit for calculating a window size in which the data is a bandwidth within the guaranteed bandwidth;
A window size writing unit for notifying the data transmission terminal to use the window size calculated by the window size calculation unit for bandwidth control of the data transmission terminal;
A node device comprising: an option control unit that rewrites an option in the SYN packet of the service target flow according to the window size calculated by the window size calculation unit.   The node device according to claim 1, wherein the option control unit rewrites the maximum segment size in the SYN packet of the service target flow according to the window size calculated by the window size calculation unit. .   The node device according to claim 1, wherein the option control unit rewrites the scaling option in the SYN packet of the service target flow according to the window size calculated by the window size calculation unit. A bandwidth control method for controlling a bandwidth of data transmission from the data transmission terminal to the data reception terminal in a bandwidth guarantee network in which a bandwidth capable of transmitting data from the data transmission terminal to the data reception terminal is guaranteed,
Calculating a propagation delay time between the data transmitting terminal and the data receiving terminal;
Based on the guaranteed bandwidth allocated to the service target flow from the data transmitting terminal to the data receiving terminal in the bandwidth guaranteed network and the calculated propagation delay time, the data of the service target flow is within the guaranteed bandwidth. Calculating a window size to be a bandwidth of
Notifying the data transmission terminal of the calculated window size for use in bandwidth control of the data transmission terminal;
Rewriting an option in the SYN packet of the service target flow according to the calculated window size. In the step of rewriting the option,
The bandwidth control method according to claim 4, wherein the maximum segment size in the SYN packet of the service target flow is rewritten according to the calculated window size. In the step of rewriting the option,
5. The bandwidth control method according to claim 4, wherein the scaling option in the SYN packet of the service target flow is rewritten according to the calculated window size.

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