JP2010068278A - Band decision device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for determining a band of a communication system for conducting a burst transmission without oppressing a user traffic. <P>SOLUTION: In this method, a transmitter generates a plurality of test packets including a number indicating a transmitting order, and transmits the plurality of generated test packets to the communication system in this order. Meantime, a receiver receives the test packets from the communication system, and detects a maximum value of a difference in receiving times of the test packets transmitted consecutively. Thereafter, an empty band is determined according to the detected maximum value and one or more thresholds. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a network bandwidth monitoring technique, and more particularly to a technique for determining the degree of bandwidth congestion in a communication system that performs burst transmission, such as communication in the upstream direction of a PON (Passive Optical Network).

  For example, Non-Patent Document 1 discloses a technique for monitoring an available network bandwidth. Of these, the SLoPS (Self-loading Periodic Stream) method, for example, confirms that there is a 50 Mbps free bandwidth depending on whether or not the test packet transmitted to the network at 50 Mbps can be received without any problem on the receiving side. There is a problem that the test packet significantly squeezes the user traffic.

  On the other hand, the TOPP (Trains of Packet Pairs) method transmits a set of two test packets having the same size, and estimates the free bandwidth by measuring the interval between the two test packets on the receiving side. Therefore, there is an advantage that the influence on the user traffic is small. 5 and 6 are diagrams for explaining the TOPP method. As shown in FIG. 5, it is assumed that a set of test packets is transmitted to the network at a time interval of t seconds. Note that the lengths of two test packets included in one set of test packets are both L bits. Ideally, this time interval t seconds is preserved if there is enough free bandwidth on the network, but on the receiving side, the time interval increases to t + Δt seconds as the network becomes congested.

  In the TOPP system, L / t is a transmission bit rate Ro on the transmission side, L / (t + Δt) is a reception bit rate Rm on the reception side, and the transmission side apparatus transmits a plurality of sets of test packets while changing Ro. As shown in FIG. 6, the transmitting and receiving device measures the change in Ro / Rm with respect to Ro. Ideally, Ro / Rm is 1 when there is sufficient network bandwidth, but Δt increases when there is not enough network bandwidth, so Ro / Rm increases with increasing Ro. Will do. Therefore, Ro when the value of Ro / Rm starts to increase from 1 can be estimated as a free band.

Ravi Prasad, er al. "Bandwidth Estimation: Metrics, Measurement Techniques, and Tools", IEEE Network, November, December 2003.

  2. Description of the Related Art Recently, in a PON system such as GE (Gigabit Ethernet (registered trademark))-PON which is mainly used, an optical terminal unit (ONU: Optical Network Unit) installed in a subscriber's house is used in the upstream direction. The direction toward an optical line terminal (OLT) installed in the network is so-called burst transmission in which transmission is performed intermittently because time division multiplexing is performed. Specifically, the ONU stores a packet received from the subscriber terminal in a packet called a token, and transmits this token to the OLT at a transmission timing designated by the OLT. Note that the OLT determines the transmission timing based on the number of ONUs performing communication and traffic. That is, when there are few ONUs performing communication, the transmission timing given to each ONU can be made dense as shown in FIG. 7A, but the more ONUs performing communication, the more The transmission timing that can be given to the ONU is sparse as shown in FIG.

  The data transmitted by the ONU in the upstream direction is temporarily stored in the ONU buffer, and at the ONU token transmission timing, an amount of data that can be stored in the token is read from the buffer and transmitted. When the ONU receives a set of test packets in accordance with the TOPP method before the next token can be transmitted, the set of test packets are both stored in one token and transmitted. Will end up. This probability increases as the ONU token transmission timing becomes sparse. In this case, the packet interval observed on the receiving side is usually shorter than the transmission interval, and the ONU token transmission timing is sparse. Nevertheless, it is determined that there is sufficient free bandwidth. That is, the TOPP method cannot be applied to a system that performs burst transmission.

  Therefore, an object of the present invention is to provide a bandwidth determination apparatus and method for determining the bandwidth of a communication system that performs burst transmission, such as in the upstream direction of a PON system, without squeezing user traffic.

According to the method of the present invention,
A method for determining an available bandwidth of a communication system that performs burst transmission, in which a transmitter generates a plurality of test packets including a number indicating an order of transmission, and a transmitter generates a plurality of test packets, Transmitting to the communication system in the order, a receiver receiving a test packet from the communication system, detecting a maximum value of a difference in reception time of test packets transmitted continuously, and receiving And a step of determining a vacant bandwidth based on the maximum value and one or more threshold values.

According to another embodiment of the method of the present invention,
It is also preferable that the transmitter transmits the plurality of test packets so that not all the test packets are transmitted in one burst transmission of the communication system.

Also, according to another embodiment of the method of the present invention,
If the smallest threshold among the one or more thresholds is T1 seconds, and the communication system can transmit a maximum of S test packets in one burst transmission, the transmitter must be within T1 seconds. It is also preferable to transmit at least S + 1 test packets.

Furthermore, according to another embodiment of the method of the present invention,
When the minimum value of the burst transmission interval of the communication system is T2 seconds and the communication system can transmit a maximum of S test packets in one burst transmission, the transmitter can transmit at least S + 1 packets within T2 seconds. It is also preferable to send a test packet.

According to the apparatus of the present invention,
An apparatus for determining an available bandwidth of a communication system that performs burst transmission, the receiving means for receiving a plurality of test packets transmitted to the communication system from the communication system, and the reception time of each of the received plurality of test packets A receiving time measuring means for measuring, a maximum time difference detecting means for obtaining a difference between receiving times of test packets transmitted continuously, and detecting a maximum value of the obtained difference; and the maximum value and one or more threshold values And determining means for determining the free band.

According to another embodiment of the device of the invention,
An apparatus for transmitting a test packet for determining an available bandwidth of a communication system that performs burst transmission, a test packet generating means for generating a plurality of test packets including a number indicating a transmission order, and the generated plurality of test packets Is transmitted to the communication system according to the order.

Also, according to another embodiment of the apparatus of the present invention,
It is also preferable that the test packet generation unit and the transmission unit transmit the plurality of test packets so that all the test packets are not transmitted in one burst transmission of the communication system.

Furthermore, according to another embodiment of the apparatus of the present invention,
Holding means for indicating the number of generated test packets and the time interval is provided, the test packet generating means generates at least the generated number of test packets, and the transmitting means is generated by the test packet generating means within the time interval. It is also preferable to send all test packets.

  Also provided is a program that causes a computer to function as the device.

  The transmitter generates and transmits a plurality of test packets, and the receiver determines the availability of the band based on the maximum value and threshold value of the interval at which the test packets are received. With this configuration, it is possible to evaluate the free bandwidth of a system that performs burst transmission with little influence on other user traffic.

  The best mode for carrying out the present invention will be described in detail below with reference to the drawings. FIG. 3 is a configuration diagram in the case of determining the band of the GE-PON system by the band determination apparatus according to the present invention. According to FIG. 3, the GE-PON system includes an optical termination device (OLT) 40 installed in a communication station, and one or more optical termination devices (ONU) 30 installed in a subscriber's house. ing. Note that one optical fiber connected to the OLT 40 is branched into a plurality of optical fibers by a branching device such as a coupler and connected to each ONU 30. The transmitter 10 of the bandwidth determination device according to the present invention is connected to the ONU 30 and transmits a test packet to the ONU 30, and the receiver 20 of the bandwidth determination device according to the present invention is connected to the OLT 40 and receives the test packet from the OLT 40. To determine the bandwidth.

  FIG. 1 is a block diagram of the transmitter 10. According to FIG. 1, the transmitter 10 includes a test packet generator 1 and a transmitter 2. In the present invention, the test packet generator 1 generates a plurality of test packets in which numbers indicating the order of transmission are set, and the transmitter 2 transmits the generated plurality of test packets according to the set order. To do. Details of test packet generation by the test packet generator 1 and transmission by the transmitter 2 will be described later.

  FIG. 2 is a block diagram of the receiver 20. According to FIG. 2, the receiver 20 includes a reception unit 3, a reception time determination unit 4, a maximum time difference detection unit 5, and a determination unit 6. The reception unit 3 outputs a test packet received from the outside to the reception time determination unit 4, and the reception time determination unit 4 measures the reception time of each test packet.

  The maximum time difference detection unit 5 calculates the difference between the reception times of two packets whose transmission order is continuous based on the reception time of each test packet measured by the reception time determination unit 4, and the maximum value The determination unit 6 evaluates the vacant bandwidth in n + 1 stages based on the maximum value obtained by the maximum time difference detection unit 5 and n threshold values (n is an integer). It is determined that the free band is smaller as the maximum value is larger.

  FIG. 4 is a diagram for explaining a bandwidth determination method according to the present invention. Here, it is assumed that the ONU 30 can store a maximum of two test packets in one token, and the transmitter 10 generates and transmits four test packets. The four test packets are the first tokens generated by the ONU 30. Are all reached before the transmission timing. In this case, as shown in FIGS. 4A and 4B, the first and second test packets are stored in the first token, and the third and fourth test packets are stored in the second token. become. The token transmission timing of the ONU 30 in FIG. 4B is sparser than the token transmission timing of the ONU 30 in FIG. 4A, that is, the bandwidth is small, and the maximum value of the test packet reception interval in the receiver 20 is As is clear from FIG. 4, the token transmission timing of the ONU 30 becomes larger as it becomes sparse. Therefore, it is possible to determine the availability of the band based on the maximum value.

  Subsequently, a test packet transmitted by the transmitter 10 will be described. As shown in FIG. 4, in the present invention, the transmitter 10 needs to transmit a test packet so that the ONU 30 does not store all of the transmitted test packets in one token. Here, it is assumed that the interval T at which the ONU 30 transmits a token is a fixed value, and a maximum of S test packets can be stored in each token. That is, if the size of the test packet is L bits, the token can store L × S bit data, but cannot store L × (S + 1) bit data.

In this case, the test packet generator 1 generates at least S + 1 test packets, and the transmitter 2 transmits all the generated test packets within T seconds, so that at least all of these test packets are 1 It is possible to prevent transmission with one token. However, the interval T at which the ONU 30 transmits a token is a variable value specified by the OLT 40. Therefore, in order to prevent all the test packets from being transmitted by one token, the minimum interval T _min seconds of the token transmission timing that can be specified by the OLT 40 for one ONU 30 is used, and the interval is within T _min seconds. At least S + 1 test packets need to be transmitted. However, for this purpose, the physical speed of the link connecting the transmitter 10 and the ONU 30 needs to be equal to or higher than L × (S + 1) / T _min bps. Therefore, if the physical speed of the link connecting the transmitter 10 and the ONU 30 is high and it is possible to transmit S + 1 test packets within the interval T _min seconds, this can be used.

On the other hand, the present invention does not estimate a specific value of a free bandwidth such as a free bandwidth of 50 Mbps, but performs evaluation in n + 1 stages with n threshold values. Further, as apparent from FIG. 4, the interval between test packets observed by the receiver 20 depends on the token transmission interval of the ONU 30. Therefore, if the smallest threshold among the n thresholds is T _th1 seconds, it is sufficient that the receiver 20 can detect that the token transmission interval is equal to or greater than T _th1 seconds. That is, since it is possible to evaluate at n + 1 stages by generating and transmitting at least S + 1 test packets within the interval T _th1 second, S + 1 test packets are transmitted during the interval T _min seconds. Use this when it is impossible. Note that T _th1 is a value determined _{depending on the} degree of detection.

  As described above, in the present invention, the transmitter 10 generates and transmits a plurality of test packets, and the receiver 20 obtains the maximum value of the interval at which the test packets are received. Determine the condition. The number of test packets transmitted by the transmitter 10 and the time interval for transmitting the test packets of this number of transmissions are as described above, and these values are set in a holding unit (not shown in FIG. 1), It is changed according to the communication system to be tested. Although the present invention enables evaluation of free bandwidth even in a system that performs burst transmission, it does not transmit test packets to fill all the free bandwidth, and therefore, to other user traffic. The effect is slight. In addition, although demonstrated in the form which evaluates the upstream band of a GE-PON system, this invention is applicable to all the communication systems which perform burst transmission. At that time, the token in the above embodiment is replaced with a token indicating a unit of burst in a system that performs individual burst transmission.

  The transmitter 10 and the receiver 20 of the bandwidth determination apparatus according to the present invention can be realized by a program that causes a computer to function as each unit of FIGS. These computer programs can be stored in a computer-readable storage medium or distributed via a network. Furthermore, the present invention can be realized by a combination of hardware and software.

It is a block diagram of the transmitter of the band determination apparatus according to the present invention. It is a block diagram of the receiver of the band determination apparatus according to the present invention. It is a block diagram in the case of determining a band by the band determination apparatus according to the present invention. It is a figure explaining the zone | band determination method by this invention. It is a figure explaining transmission / reception of the test packet in a TOPP system. It is a figure explaining the estimation of the band in a TOPP system. It is a figure explaining the signal transmission to the up direction by ONU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test packet production | generation part 2 Transmission part 3 Reception part 4 Reception time determination part 5 Maximum time difference detection part 6 Determination part 10 Transmitter 20 Receiver 30, 40 Optical termination device

Claims (9)

A method of determining an available bandwidth of a communication system that performs burst transmission,
A transmitter generating a plurality of test packets including a number indicating a transmission order;
Transmitting a plurality of generated test packets to the communication system in the order as described above;
A receiver receiving a test packet from the communication system and detecting a maximum value of a difference between reception times of continuously transmitted test packets;
A receiver determining an available bandwidth according to the maximum value and one or more threshold values;
A method comprising: The transmitter transmits the plurality of test packets so that all the test packets are not transmitted in one burst transmission of the communication system.
The method of claim 1. Among the one or more thresholds, when the smallest threshold is T1 seconds and the communication system can transmit a maximum of S test packets in one burst transmission,
The transmitter transmits at least S + 1 test packets within T1 seconds.
The method of claim 1. When the minimum value of the burst transmission interval of the communication system is T2 seconds and the communication system can transmit a maximum of S test packets in one burst transmission,
The transmitter transmits at least S + 1 test packets within T2 seconds.
The method of claim 1. An apparatus for determining an available bandwidth of a communication system that performs burst transmission,
Receiving means for receiving a plurality of test packets transmitted to the communication system from the communication system;
A reception time measuring means for measuring the reception time of each of the plurality of received test packets;
A maximum time difference detection means for obtaining a difference in reception time of test packets transmitted continuously and detecting a maximum value of the obtained difference;
A determination means for determining a free bandwidth based on the maximum value and one or more threshold values;
A device equipped with. An apparatus for transmitting a test packet for determining an available bandwidth of a communication system that performs burst transmission,
Test packet generation means for generating a plurality of test packets including a number indicating the order of transmission;
Transmitting means for transmitting the generated plurality of test packets to the communication system in the order;
A device equipped with. The test packet generation unit and the transmission unit transmit the plurality of test packets so that all the test packets are not transmitted in one burst transmission of the communication system.
The apparatus according to claim 6. It has a holding means for indicating the number of test packets generated and the time interval,
The test packet generation means generates at least the generated number of test packets,
The transmission means transmits all the test packets generated by the test packet generation means within the time interval.
Apparatus according to claim 6 or 7.   A program for causing a computer to function as the apparatus according to claim 5.

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