JP4774411B2 - Edge node 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.

  Communication between terminals such as personal computers is performed via a computer network such as the Internet. 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 TCP, bandwidth control that autonomously changes the window size according to packet discard is performed. The TCP window size is updated when an ACK arrives.

  In data transfer, it may be required to transfer a large amount of data at high speed. However, in the data transfer in the bandwidth guarantee network that restricts the inflow at the entrance of the network in order to prevent the traffic exceeding the guaranteed bandwidth from flowing into the network, the above-mentioned bandwidth control makes the throughput serrated and guaranteed. There was a problem that the bandwidth could not be fully utilized.

On the other hand, technologies for transmitting data at a constant throughput according to the guaranteed bandwidth by making changes to the TCP protocol and technologies for making the data throughput constant by controlling the advertisement window size have been studied. ing. In Non-Patent Document 1, studies have been made to prevent packet discard by controlling the TCP window size and maintain good throughput.
Yuta Hattori and five others, “Examination of TCP flow rate control method in edge router”, IEICE General Conference (B-6-54), March 2007, p. 54

  Non-Patent Document 1 discloses a technique for preventing the occurrence of packet discard by controlling the advertisement window size notified by ACK to an appropriate value calculated based on RTT (Round Trip Time). Yes. The technique is based on the premise that transmission / reception of data for the window size is completed and ACK is returned every time the advertisement window size is updated based on the measured RTT.

  However, the TCP is equipped with a delayed ACK algorithm that returns a single ACK for a plurality of data at the time of data reception. If this delayed ACK algorithm is used, an ACK is not always returned in synchronization with the transmission of data for the window size. If ACK is not returned, data transmission / reception is not completed. Therefore, the advertisement window size notified to the data transmission terminal by ACK may not be updated to an appropriate value. As a result, there is a possibility that the throughput temporarily increases and packet discard occurs, and the throughput is extremely reduced by the bandwidth control.

  An object of the present invention is to provide an apparatus that maintains a high throughput by efficiently using a guaranteed bandwidth in consideration of a delayed ACK algorithm in data transfer in a bandwidth guaranteed network.

In order to achieve the above object, the edge node of the present invention comprises:
An edge node disposed between the data transmitting terminal and the data receiving terminal in a bandwidth guaranteed network in which a bandwidth that can be transmitted from the data transmitting terminal to the data receiving terminal is guaranteed;
A bandwidth information holding unit for holding a guaranteed bandwidth allocated to a service target flow from the data transmitting terminal to the data receiving terminal in the bandwidth guaranteed network;
A propagation delay time calculating unit for measuring the propagation delay time of the service target flow;
Based on the guaranteed bandwidth of the service target flow held in the bandwidth information holding unit and the propagation delay time measured by the propagation delay time calculation unit, the data of the service target flow is within the guaranteed bandwidth. A window size calculator for calculating the window size;
An advertisement window size writing unit for notifying the data transmitting terminal of the window size calculated by the window size calculating unit by a response packet from the data receiving terminal to the data transmitting terminal;
Based on the window size calculated by the window size calculator and a delay mechanism of a response packet from the data receiving terminal to the data packet from the data transmitting terminal in the service target flow, the data packet for the window size A data division number calculating unit for calculating a data division number for dividing the data packet of the service target flow so that the response packet is returned when
A data dividing unit for dividing the data packet of the service target flow according to the data division number calculated by the data division number calculating unit;
have.

  Further, in the edge node of the present invention, the delay mechanism defines how many data packets from the data transmitting terminal are sent in response to one response packet from the data receiving terminal in the service target flow. It may be an algorithm to perform.

  In the edge node of the present invention, the data division number calculation unit may determine the number of data packets corresponding to the window size based on the window size calculated by the window size calculation unit and the delay mechanism. The data division number may be determined so as to be a multiple of the number of data packets corresponding to the response packet.

  Further, in the edge node of the present invention, the data division number calculation unit displays an ACK number indicating a data packet corresponding to the response packet described in the response packet between two response packets in the service target flow. It is also possible to recognize the number of the data packets corresponding to the one response packet by calculating the difference between the two.

  Further, in the edge node of the present invention, the data dividing unit compares the window size with the integrated value of the data size of the data packet of the service target flow that passes therethrough, thereby generating a data packet group corresponding to the window size. It may be recognized.

  In the edge node of the present invention, the data dividing unit adjusts the number of data packets for the window size by dividing only the last data packet in the data packet group for the window size. Also good.

  The edge node of the present invention recognizes the service target flow, further recognizes a data packet and a response packet of the service target flow, sends the data packet of the service target flow to the data dividing unit, and A flow identification / distribution unit that sends a response packet of a flow to the advertisement window size writing unit may be further included.

The edge node of the present invention further includes a flow information holding unit that holds the connection information of the service target flow and the propagation delay time of the service target flow calculated by the propagation delay time calculation unit in association with each other. And
The window size calculation unit may use the propagation delay time held in the flow information holding unit for calculation of the window size.

  According to the present invention, the influence of the delay of the response packet can be suppressed by adjusting the number of data packets within the window size according to the delay mechanism of the response packet with respect to the data packet. Throughput can be stably controlled and the guaranteed bandwidth can be used efficiently.

  Embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  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. The size of the congestion window is determined on the data transmission side according to the packet discard situation. 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 for each service target flow between a data transmitting terminal serving as a data transmitting side and a data receiving terminal serving as a data receiving side by a band guarantee network. 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, so 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 this embodiment, the edge node between the data transmitting terminal and the data receiving terminal is within the guaranteed bandwidth from the propagation delay time between the data transmitting side and the data receiving side and the guaranteed bandwidth by the bandwidth guaranteed network. The window size to be transmitted (hereinafter referred to as BGWND) is calculated, and the advertisement window size described in the ACK packet from the data receiving terminal to the data transmitting terminal is rewritten to the BGWND 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.

  Also, the edge node divides the data packet from the transmitting terminal based on the delayed ACK number indicating how many ACK packets are returned for the number of data packets by the delayed ACK algorithm. The number of data packets is adjusted to be a multiple of the delayed ACK number.

  At this time, the edge node monitors the ACK number in the ACK packet from the data receiving terminal, and measures the ACK number difference (hereinafter, DiffACK) between the ACK packets. The delayed ACK number is determined by this DiffACK.

Examples of the data packet dividing method include the following (1) and (2).
(1) Each of all data packets that pass through is divided into the same number as the delayed ACK number.
(2) The data packets in BGWND are divided in units of BGWND so that the number of data packets in BGWND is a multiple of the delayed ACK number. At that time, it is preferable to divide only one data packet in BGWND so that the number of data packets in BGWND is a multiple of the delayed ACK number.

  In this way, the influence of the delay of the ACK packet generated by the delayed ACK algorithm is suppressed by adjusting the number of data packets in the BGWND according to the delay mechanism (delayed ACK algorithm) of the ACK packet with respect to the data packet. Can do. As a result, the throughput can be stably controlled within the guaranteed bandwidth, so that the guaranteed bandwidth can be used efficiently.

  In the present embodiment, the influence of the ACK delay generated by the delayed ACK algorithm is suppressed by adjusting the number of data packets in BGWND to a multiple of the delayed ACK number. More specifically, the number of data packets is adjusted by dividing the data packets.

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

  FIG. 1 is a block diagram showing the configuration of the data transmission system according to the present embodiment. Referring to FIG. 1, the data transmission system of this embodiment includes edge nodes 11 and 12 and a bandwidth management server (RACS (Resource and Admission Control System)) 13.

  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. As a result, 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.

  As a result of 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 transmitting terminal 14 to the data receiving 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.

  The edge node 11 measures a round-trip propagation delay time (RTT) 17 between the data transmission terminal 14 and the data reception terminal 15. Then, the edge node 11 uses the round-trip propagation delay time 17 and the guaranteed bandwidth to calculate BGWND so that the data transmission bandwidth is within the guaranteed bandwidth, and the ACK packet from the data receiving terminal 15 to the data transmitting terminal 14 The value of BGWND is written in the window field.

  The edge node 11 monitors the ACK number (sequence number) in the ACK packet from the data receiving terminal 15 and measures DiffACK. The delayed ACK number representing how many data packets are returned by the TCP delayed ACK algorithm is determined by DiffACK.

  Further, the edge node 11 divides the data packet from the data transmission terminal 14 based on the delayed ACK number, thereby adjusting the number of data packets in BGWND to be a multiple of the delayed ACK number.

  FIG. 2 is a block diagram showing the configuration of the edge node of this embodiment. 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, a flow information holding unit 26, and a window size calculation. A section 27, an advertisement window size writing section 28, a data dividing section 29, and a data dividing number calculating section 30.

  The data reception unit 21 receives a packet such as a data packet or an ACK packet from the data transmission terminal 14 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 based on the user information that is 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 sends the ACK packet of the service target flow to the advertisement window size writing unit 28 through the output 22a, the data packet of the service target flow from the output 22b to the data transmission unit 24, and the packet of the non-service target flow. The output 22c is distributed to the data transmission unit 24.

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

  The data transmission unit 24 transmits the packet from the flow identification / distribution unit 22, the packet from the data division unit 29, and the packet from the advertisement window size writing unit 28 to the edge node 12 via the bandwidth guarantee network 16. To do.

  The bandwidth information holding unit 25 holds the bandwidth information of the service target flow 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 17 calculated by the propagation delay time calculation unit 26 in association with each other.

  The window size calculation unit 27 guarantees the 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. The window size is calculated using the 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 data division unit 29 measures the data size of the data packet transferred from the flow identification / distribution unit 22, accumulates the measured value in the data packet counter, and determines the value of the data packet counter and the data division number calculation unit 30. Based on the number of data divisions notified from, the data packet is divided. Details of the division processing will be described later.

  The data division number calculation unit 30 calculates an ACK number difference (hereinafter, DiffACK) in the ACK packet transferred from the flow identification / distribution unit 22, and calculates the window size and DiffACK notified from the window size calculation unit 27. Based on this, the number of data divisions is calculated. Details of the data division number calculation process will be described later.

  FIG. 3 is a diagram for explaining packet distribution by the flow identification / distribution unit 22. With reference to FIG. 3, packet distribution by the flow identification / distribution unit 22 will be described in detail.

  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 of the edge node 11 determines whether or not it is an ACK packet of the service target flow. If it is an ACK packet of the service target flow, the flow identification / distribution unit 22 sends the ACK packet to the advertisement window size writing unit 28 through the output 22a. When a data packet from the data transmission terminal 14 is received, it is determined whether or not the data packet is a service target flow. If it is a data packet of a service target flow, the flow identification / distribution unit 22 sends the data packet to the data division unit 29 through the output 22b. The flow identification / distribution unit 22 sends the packet of the service non-target flow to the data transmission unit 24 through the output 22c.

  FIG. 4 is a sequence diagram showing exchange of signals between blocks in the edge node when the round-trip propagation delay time is measured. Here, it is assumed that the propagation delay time between the data transmission terminal 14 and the edge node 11 is sufficiently small, and the round-trip propagation delay time between the edge node 11 and the data reception terminal 15 is the difference between the data transmission terminal 14 and the data reception terminal 15. It is assumed to be equal to the round-trip propagation delay time 17 between. 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 round-trip propagation delay together with the user information of the service target flow. A time measurement start request 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. Thereafter, when the flow identification / distribution unit 22 observes the SYN / ACK packet from the data receiving terminal 15 with respect to the SYN packet (step 103), the flow identification / distribution unit 22 sends a round-trip propagation delay time measurement end request to the propagation delay time calculation unit 23 together with the user information. Send (step 104). Thus, the propagation delay time calculation unit 23 ends the round trip propagation delay time measurement. The propagation delay time calculation unit 23 that has finished measuring the round-trip propagation delay time associates the measured round-trip propagation delay time 17 with the user information and notifies the flow information holding unit 26 as a round-trip propagation delay time report (step 105).

  FIG. 5 is a sequence diagram showing exchange of signals between blocks in the edge node when the window size is calculated. When the flow information holding unit 26 receives the round trip propagation delay time report from the propagation delay time calculating unit 23 (step 201), the flow size holding unit 26 calculates the bandwidth guarantee window calculation together with the round trip propagation delay time 17 and the user information to the window size calculating unit 27. Send a request (step 202). The window size calculation unit 27 that has received the bandwidth guarantee window calculation request 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 request from the window size calculation unit 27 (step 204). The window size calculation unit 27 that has received the round-trip propagation delay time 17 and the guaranteed bandwidth calculates a window size such that the data transmission terminal 14 transmits data within the guaranteed bandwidth based on these values (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 calculated by, for example, equation (1).

  FIG. 6 is a sequence diagram showing exchange of signals between blocks in the edge node when calculating the number of data divisions. Referring to FIG. 6, when the ACK packet of the service target flow arrives at the flow identification / distribution unit 22 (step 301), the flow identification / distribution unit 22 calculates the ACK number and user information of the ACK packet and calculates the number of data divisions. The unit 30 is notified (step 302). The data division number calculation unit 30 notified of the ACK number and user information stores the ACK number and user information (step 303).

  Thereafter, when the next ACK packet of the same service target flow arrives at the flow identification / distribution unit 22 (step 304), the flow identification / distribution unit 22 uses the ACK number and user information of the ACK packet as the data division number calculation unit 30. (Step 305). The data division number calculation unit 30 notified of the ACK number and the user information calculates a difference (DiffACK) between the current ACK number and the previous ACK number stored in Step 303 (Step 306). This DiffACK becomes the delayed ACK number.

  In addition, the window size calculation unit 27 notifies the data division number calculation unit 30 of the calculated window size (BGWND) (step 307). The data division number calculation unit 30 calculates the data division number so that the number of data packets within the window size is a multiple of the delayed ACK number.

  Here, as an example, the number of data packets within the window size is adjusted by dividing the last data packet of the data packet group within the window size into the number of data divisions. In that case, the number of data divisions can be calculated by equation (2).

  FIG. 7 is a sequence diagram showing signal exchange between blocks in the edge node at the time of data division. Referring to FIG. 7, first, the data division number is notified from the data division number calculation unit 30 to the data division unit 29 (step 401). Next, the data packet is transferred from the flow identification / distribution unit 22 to the data division unit 29 (step 402). When the data packet arrives at the data dividing unit 29, the data counter is incremented by the data size of the data packet (step 403). Next, the data dividing unit 29 confirms whether the count value of the data counter is equal to or greater than BGWND (step 404). When the count value of the data counter is equal to or greater than BGWND, the data packet to which the data size is added is the data in BGWND. It is recognized as the last data packet in the packet group. Therefore, the count value of the data counter is cleared, the last data packet is divided into the number of data divisions (step 406), each is given a sequence number and transmitted to the data transmission unit 24 (step 407).

  On the other hand, if the count value of the data counter is less than BGWND in step 404, the data packet is transmitted to the data transmission unit 24 as it is without being divided (step 408).

  FIG. 8 is a sequence diagram showing signal exchange between blocks in the edge node when the advertisement window size is written in the ACK packet. Referring to FIG. 8, first, the window size calculator 27 calculates the window size of the service target flow (step 501). 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 502). The advertisement window size writing unit 28 writes the window size value notified from the window size calculation unit 27 into the window field of the ACK packet from the flow identification / distribution unit 22 (step 503). 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.

It is a block diagram which shows the structure of the data transmission system by this embodiment. It is a block diagram which shows the structure of the edge node of this embodiment. 6 is a diagram for explaining packet distribution by a flow identification / distribution unit 22. FIG. It is a sequence diagram which shows the exchange of the signal between the blocks in an edge node when measuring a round-trip propagation delay time. It is a sequence diagram which shows the exchange of the signal between the blocks in an edge node when calculating a window size. It is a sequence diagram which shows the exchange of the signal between the blocks in the edge node at the time of data division number calculation. It is a sequence diagram which shows exchange of the signal between the blocks in the edge node at the time of data division. It is a sequence diagram which shows exchange of the signal between the blocks in an edge node when writing advertisement window size in an ACK packet.

Explanation of symbols

11, 12 Edge node 13 Bandwidth management server (RACS)
DESCRIPTION OF SYMBOLS 14 Data transmission terminal 15 Data reception terminal 16 Band guarantee network 21 Data reception part 22 Flow identification and distribution part 23 Propagation delay time calculation part 24 Data transmission part 25 Band information holding part 26 Flow information holding part 27 Window size calculation part 28 Advertising window Size writing unit 29 Data division unit 30 Data division number calculation unit

Claims (9)

An edge node disposed between the data transmitting terminal and the data receiving terminal in a bandwidth guaranteed network in which a bandwidth that can be transmitted from the data transmitting terminal to the data receiving terminal is guaranteed;
A bandwidth information holding unit for holding a guaranteed bandwidth allocated to a service target flow from the data transmitting terminal to the data receiving terminal in the bandwidth guaranteed network;
A propagation delay time calculating unit for measuring the propagation delay time of the service target flow;
Based on the guaranteed bandwidth of the service target flow held in the bandwidth information holding unit and the propagation delay time measured by the propagation delay time calculation unit, the data of the service target flow is within the guaranteed bandwidth. A window size calculator for calculating the window size;
An advertisement window size writing unit for notifying the data transmitting terminal of the window size calculated by the window size calculating unit by a response packet from the data receiving terminal to the data transmitting terminal;
Based on the window size calculated by the window size calculator and a delay mechanism of a response packet from the data receiving terminal to the data packet from the data transmitting terminal in the service target flow, the data packet for the window size A data division number calculating unit for calculating a data division number for dividing the data packet of the service target flow so that the response packet is returned when
A data dividing unit for dividing the data packet of the service target flow according to the data division number calculated by the data division number calculating unit;
An edge node having   The delay mechanism is an algorithm that defines how many data packets from the data transmitting terminal correspond to one response packet from the data receiving terminal in the service target flow. The listed edge node.   The data division number calculating unit, based on the window size calculated by the window size calculating unit and the delay mechanism, the number of data packets corresponding to the window size corresponds to the one response packet. The edge node according to claim 1 or 2, wherein the number of data divisions is determined so as to be a multiple of the number of.   The data division number calculation unit calculates a difference between ACK numbers indicating data packets corresponding to the response packet described in the response packet between the two response packets in the service target flow. The edge node according to claim 3, wherein the number of the data packets corresponding to one response packet is recognized.   The data division unit recognizes a data packet group corresponding to the window size by comparing the window size with an integrated value of the data size of the data packet of the service target flow that passes therethrough. The edge node according to any one of the above.   6. The edge node according to claim 5, wherein the data dividing unit adjusts the number of data packets for the window size by dividing only the last data packet in the data packet group for the window size.   Recognizing the service target flow, further recognizing a data packet and a response packet of the service target flow, sending the data packet of the service target flow to the data dividing unit, and sending the response packet of the service target flow to the advertisement window size The edge node according to claim 1, further comprising a flow identification / distribution unit to be sent to the writing unit. A flow information holding unit that holds the connection information of the service target flow in association with the propagation delay time of the service target flow calculated by the propagation delay time calculation unit;
The edge node according to claim 1, wherein the window size calculation unit uses the propagation delay time held in the flow information holding unit for calculation of the window size. 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 that can be transmitted from the data transmission terminal to the data reception terminal is guaranteed,
In advance, the guaranteed bandwidth allocated to the service target flow from the data transmitting terminal to the data receiving terminal in the bandwidth guaranteed network,
Measure the propagation delay time of the service target flow,
From the guaranteed bandwidth of the service target flow that is held and the measured propagation delay time, calculate the window size in which the data of the service target flow is a bandwidth within the guaranteed bandwidth,
Notifying the data transmitting terminal of the calculated window size by a response packet from the data receiving terminal to the data transmitting terminal;
Based on the calculated window size and the delay mechanism of the response packet from the data receiving terminal for the data packet in the service target flow, the response packet is returned when the data packet for the window size is sent As described above, a data division number for dividing the data packet of the service target flow is calculated,
A bandwidth control method for dividing a data packet of the service target flow according to the calculated data division number.

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