JP5427707B2 - Data transmission system and method - Google Patents

Description

  The present invention relates to a data transmission system and method, and is used when data is transmitted in a network having a band limitation or a limitation on burstiness. In particular, the characteristics of the network are unknown in a transmission / reception apparatus, and they are estimated. The present invention relates to a data transmission system and method used when it is necessary to efficiently transmit a network band without causing data loss.

  In the data distribution network, a plurality of users share a network band and perform transmission. For this reason, it is necessary to control the transmission rate according to the surplus bandwidth of the distribution network.

  A typical protocol having a rate control function is TCP (Transmission Control Protocol). In TCP, it is estimated whether there is a surplus network bandwidth due to packet discard, and if discard occurs, the transmission rate is reduced by window control. TCP is widely used in data transfer, but has the following problems.

  First, TCP rate control is controlled using packet discard as an index. If there is traffic that does not allow packet discard in the network, for example, stream transmission of multimedia data, packet discard caused by TCP may adversely affect the quality of other traffic.

  Second, TCP operates to use up all of the surplus bandwidth and greatly reduces the window size at the time of rate control, so the transmission rate decreases at a stretch. For this reason, TCP is not suitable for multimedia data stream transmission that is premised on transmission at a constant rate.

  Third, because TCP does not perform control focusing on output burstiness, packet loss occurs when it is applied to a distribution network with QOS restrictions, and transmission using the network effectively cannot be performed. is there. Furthermore, TCP is a unicast protocol and cannot be used for multicast distribution.

  In consideration of the above problems, various rate control methods are used in multimedia streaming. One method is to control the data transmission rate by estimating the excess bandwidth of the network.

  Many methods have been devised to estimate the surplus bandwidth of data, but the bandwidth is measured by sending a packet (probe packet) having a fixed pattern to the network and measuring the reception interval and delay of the probe packet on the receiving side. The method of performing is general (for example, refer nonpatent literature 1).

  For example, in a bandwidth estimation method called Pathload, a packet sequence composed of a plurality of packets with a constant interval is input to the network, and the available bandwidth is estimated based on whether or not the interval between received packets is open (for example, non-loading). Patent Document 2). Although this method is robust, it is necessary to transmit a packet sequence with a constant interval, and to estimate the rate by binary search, it is necessary to transmit a large amount of probe packets for measurement, and There is a problem that a large load is applied. On the other hand, the method of transmitting a packet pair composed of two consecutive packets and measuring the change in the interval has a small overhead, but requires a precise measurement of the packet reception interval, and the data transmission bandwidth is small. When it becomes higher, it is not always possible to obtain a highly accurate band estimation.

  Further, there is a technique for comparing surplus bandwidth estimation methods from the viewpoint of determining a streaming communication rate (see, for example, Non-Patent Document 3). This surplus bandwidth estimation method is a method of performing measurement using a probe packet, and does not necessarily take into account controlling the rate during data transmission. As a method for performing rate control while estimating the surplus bandwidth, a method has been proposed in which a transfer bandwidth is estimated on the receiving side based on an interval between two packets, and a transmission rate is controlled based on this (for example, non-patent literature). 4). In this method, since the rate is estimated based on the packet interval, it is necessary to accurately measure the packet interval. Even in the non-patent document 4, evaluation is performed only at a low rate of several hundred kbps. As described above, the evaluation based on the packet interval may be inaccurate when the bit rate is increased.

  In RTP (Real-time Transport Protocol) used in multimedia delivery, means such as RTCP (Real-time Transport Control Protocol), which is a control protocol, feeds back information such as delay, discard rate, and jitter of received packets to the transmission source. Is prepared (for example, see Non-Patent Document 5), and a rate control means compatible with TCP is standardized (for example, see Non-Patent Document 6). However, the standardized rate control method controls the rate by discarding packets, and does not control the rate without generating packet discards like the above-described surplus bandwidth estimation technique.

  Another way to eliminate packet discard in the network is to guarantee QOS so that packet discard and excessive delays do not occur in the network. In QOS, it is necessary to make a bandwidth reservation. For example, RSVP (Resource reSerVation Protocol) (see, for example, Non-Patent Document 7) or the like is a protocol that dynamically reserves a bandwidth, but is not generally used. In a network that guarantees QOS, the maximum transmission rate and the amount of data that can be continuously input, that is, burstiness is used as an index for the input traffic. By blocking the flow into the network, the influence on other traffic is prevented. Therefore, when communication is performed without considering bandwidth limitation due to policing in a distribution network in which QOS is set, when such policing is performed in the distribution network, the average rate is less than the maximum rate allowed by the network. Even so, there is a possibility that data may be discarded. However, there are many cases where the limiting condition of burstiness in the distribution network is not known to the transmission device, and in a system that performs data transmission by software control, the packet interval is adjusted to keep the burstiness below a certain level. Can put a heavy load on the system.

  All of the above rate control techniques are rate control methods that focus on the surplus bandwidth, and are not controls that focus on such things as allowable burstiness in the distribution network, and processing overhead for controlling the packet interval is reduced. The control is not considered.

  In this system that controls the rate, there is a problem that the overhead for processing increases if the packet transmission interval is precisely controlled for each packet. For this reason, it is necessary to manage packet transmission with as large a granularity as possible within the range of burstiness allowed by the network.

  As described above, in particular, assuming applications such as multimedia stream transmission, a means for performing stable and efficient data transmission has not been established in a distribution network with restrictions on data transmission bandwidth and burstiness. Furthermore, in multicast distribution often used in multimedia distribution, network restriction conditions are different for each distribution destination, so it is also necessary to set data transmission parameters in consideration of bottlenecks.

R. S. Prasad, "Bandwidth estimation: metrics, measurement techniques, and tools" IEEE Network 2003. Alok Shriram1, Margaret Murray2, Young Hyun1, Nevil Brownlee1, Andre Broido1, Marina Fomenkov1, "Comparison of Public End-to-End BandwidthEstimation Tools on High-Speed Links" In Proceedings of PAM 2005. "Performance evaluation of end-to-end available bandwidth estimation method and its application to stream mink communication" Kato Kaoru, Kenichi Yukimatsu, Hitoshi Hashimoto, FY 2005 IPSJ Tohoku Branch Lecture No. 8 Nadeem Aboobaker, David Chanady, Mario Gerla, M. Y. Sanadidi, "Streaming Media Congestion Control using Bandwidth Estimation1" Proceedings of the 5th IFIP / IEEE International Conference on Management of Multimedia Networks and Services: Management of Multimedia on the Internet 2002. "RTP: A Transport Protocol for Real-Time Applications" RFC1889 "TCP Friendly Rate Control (TFRC): Potocol Specification" RFC3448 "Resource ReSerVation Protocol (RSVP)" RFC2205

  As described above, as a method of controlling and distributing the transmission rate according to the surplus bandwidth of the distribution network, the TCP protocol performs flow control that sharply decreases the transmission rate during congestion, and controls focusing on the burst property of the transmitted packet Is not suitable for multimedia data.

  The technique of Non-Patent Document 4, which is a method of performing rate control while estimating the surplus bandwidth, measures the interval between two packets and estimates the transfer bandwidth, and then controls the transmission rate. There is a need to be measured, and there is doubt whether it can be effective at high bit rates.

  The technique of Non-Patent Document 6 is a control method using RTCP. However, the control is performed by packet discard, and the rate is not controlled without causing packet discard.

  On the other hand, even in a QOS-guaranteed network, there is a problem in that, for input traffic exceeding the allowable burstiness of the network, packet discarding occurs even if the average traffic is within the guaranteed rate.

  The present invention has been made in view of the above points, and realizes high-quality data transmission without packet discard by considering the surplus bandwidth of the distribution network, as well as the allowable burst property of the distribution network and the time of the outgoing packet. An object of the present invention is to provide a data transmission system and method capable of realizing optimal burst control by considering accuracy.

  In order to solve the above problems, according to the invention according to claim 1 (claim 5), in the data transmission system of the present invention, the data transmission means, the rate monitoring means, and the rate control means are included in the transmission device. The device is provided with data receiving means and rate excess detecting means, and in order to limit the amount of data transmitted at one time and the maximum transmission rate, the data transmitting means buffers input packets, and at a certain transmission interval. In addition, there is provided data transmission means for performing control so as to take out a plurality of packets having an allowable data amount or less from the buffered packets and continuously transmit them as data bursts. Further, the data transmission means is provided with a function of notifying the receiving device of the start position and transmission interval of the data burst. By using the data transmission means, the present data transmission system can be controlled to transmit data within the limits of the distribution network bandwidth and burstiness. Furthermore, since the data transmission means can send out multiple packets at a time, it can be applied even when the packet transmission time cannot be controlled below a certain granularity, such as when the transmission device is implemented in software. It is.

  In addition, in order to evaluate the available bandwidth of the packet discard and distribution network, the data receiving means of the receiving device includes a function for detecting the start position of the data burst from the input packet, the packet discard in the data burst, and the data burst. A function for observing the interval between them is provided. The rate excess detection means is provided with a function to notify the packet discard when the packet discard is detected, and further detects that the ratio between the data burst interval and the data burst transmission period is below a certain level, A function is provided for notifying that the rate has been exceeded when the number of times continues for a certain number of times. The data burst transmitted from the transmission side is received with the packet interval widened due to the bandwidth limitation received in the distribution network. In the receiving apparatus of the present invention, from the last packet of the data burst to the beginning of the next data burst. , That is, the ratio between the data burst interval and the data burst transmission period is estimated to estimate how much the transmission network has a transmission band.

  In addition, the rate monitoring unit of the transmitting apparatus evaluates the cumulative distribution of the packet discard positions in the data burst in response to the packet discard notification, and the packet discard occurs at a high probability at the end of the data burst. Is controlled so as to reduce the allowable data amount. With this function, the data transmission system of the present invention can detect a limit value related to the burstiness of the network. Further, when the data burst transmission cycle is a certain value or more, the transmission cycle is reduced in proportion to the reduction rate of the allowable data amount. This function makes it possible to keep the burstiness below a certain level while keeping the maximum transmission rate constant. Furthermore, the rate monitoring means can cope with a case where the time accuracy required for the data transmission process is limited by performing control so that the data burst transmission cycle is a certain value or more.

  Further, according to the invention of claim 2 (claim 6), the transmission apparatus of the present invention transmits data by the rate control means when it does not receive an over-rate notification when transmitting a certain number of data bursts. Control can be performed to increase the transfer rate at a constant rate.

  According to the invention of claim 3 (claim 7), when the data transmission system of the present invention transmits data to a plurality of receiving devices, it exceeds the rate from any of the delivery destinations (receiving devices). The rate monitoring means and the rate control means are executed by receiving the notification and the packet discard notification.

  According to the invention of claim 4 (invention 8), when transferring a data burst within a distribution network, in general, due to the load of the data burst itself, the data burst is discarded toward the end of the data burst. The probability of occurrence increases. In the transmission apparatus of the present invention, it is possible to reduce the influence of packet discarding by placing highly important data at the beginning of the data burst by the packet rearranging means. The packet order can be restored by adding a sequence number to the packet.

  As described above, according to the first and fifth aspects of the present invention, when the amount of packets in the input packet buffer of the transmission means increases, the data input rate is reduced by the rate control means. For this reason, the rate of data input to the apparatus can be limited to a maximum rate or less. Further, when a rate excess notification is received from the receiving device, the transmitting device reduces the data input rate to the transmitting device by the rate control means. With this function, when the transmission data band approaches the allowable data band of the distribution network, control can be performed to reduce the rate.

  According to the inventions according to claims 2 and 6, when the congestion of the distribution network is recovered and the surplus bandwidth is increased, the data transmission rate can be restored. In the data transmission system according to the present invention, the rate is adjusted so as to ensure a certain excess bandwidth because control is performed so that the ratio of the data burst interval and the transmission period in the receiving device is not more than a certain value.

  Further, according to the third and seventh aspects of the invention, it is possible to control the burst property and the transmission rate in accordance with the delivery destination that is a bottleneck with respect to the transmission band and the allowable burst property. Further, by determining the transmission source of the rate excess notification and the packet discard notification, it is possible to identify the receiving device that is the bottleneck in the distribution network.

  Further, according to the inventions according to claims 4 and 8, by arranging the packet rearranging means in the data transmitting means, the packets are rearranged and outputted so that highly important data comes to the head part of the data burst. Can do.

It is a block diagram of the data transmission system in the 1st Embodiment of this invention. It is a structural example of the data transmission part in the 1st Embodiment of this invention. It is a conceptual diagram of the structure of the data burst in the 1st Embodiment of this invention. It is a conceptual diagram of the data burst in the delivery network in the 1st Embodiment of this invention. It is a figure which shows the data burst received with the receiver in the 1st Embodiment of this invention. It is an example of the packet discard by the restriction | limiting of the burst property in the 1st Embodiment of this invention. It is a flowchart of the process with respect to the packet discard in the 1st Embodiment of this invention. It is an example of control of the data input rate in the 1st Embodiment of this invention. It is a system block diagram in case there exists a some receiver in the 3rd Embodiment of this invention. It is a block diagram of the transmission part which has a packet rearrangement part in the 4th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration of a data transmission system according to an embodiment of the present invention.

  The data transmission system shown in FIG. 1 includes a transmission device 100, a reception device 200, and a distribution network 300. The transmission device 100 includes a data transmission unit 110, a rate monitoring unit 120, and a rate control unit 130, and the reception device 200 includes a data reception unit 210 and an excess rate detection unit 220.

  FIG. 2 shows the configuration of the data transmission unit in one embodiment of the present invention.

  The data transmission unit 110 of the transmission device 100 includes an input buffer 111 and a packet output unit 112.

  The data transmission unit 110 first buffers the input packet in the input buffer 111, and the packet output unit 112 extracts a plurality of packets from the packet at regular intervals and continuously as data bursts as shown in FIG. Send to distribution network.

  FIG. 3 is a conceptual diagram of a data burst in one embodiment of the present invention. The number of packets in the data burst is controlled such that the data amount of the data burst is less than the allowable data amount, and the interval between the data bursts is controlled to be constant according to the data burst transmission period. The maximum rate of data output by the data transmission unit 110 is the allowable data amount of data burst / sending period. In this way, the data transmission unit 110 performs control so that the maximum rate and burstiness of transmission data are below a certain level. When a packet is received at the maximum output rate or higher, the packet is accumulated in the input buffer 111. When a certain amount of packets is accumulated, control is performed to reduce the input data rate via the rate control unit 120. Is done.

  In addition to this, the data transmission unit 110 is provided with a function of notifying the reception device 200 of the start position of the data burst and the transmission cycle. The start position of the data burst is determined by a method of providing a marker flag in the packet header, a method of transmitting the marker packet before or after the data burst, or a sequence number attached to the packet, and the sequence number of the start packet of the data burst being sent to the receiving device. This can be realized by a notification method.

  FIG. 4 is a conceptual diagram of data bursts in the distribution network according to an embodiment of the present invention, and shows the behavior when data bursts are transferred in the distribution network. When the transmission bandwidth of the output link is lower than the transmission rate of the data burst in the node in the distribution network 300, a longer time than the input is required to output the packet, so the packet is buffered, as shown in (b) Data bursts are output at a packet interval wider than the input interval. On the other hand, when the transmission rate of the data burst is lower than the output bandwidth, the packet transfer time is shortened. However, since the packet interval once widened is not restored, the data burst is widened as shown in (c). The packet interval is saved and transmitted. When there is interference with other traffic, the packet interval is randomized as shown in (d) by inserting other traffic packets before and after the target packet. However, the property that the packet interval increases according to the surplus bandwidth of the network remains.

FIG. 5 shows a data burst received by the receiving apparatus according to the embodiment of the present invention.
Here, when the data burst arrives at the receiving apparatus 200, if the data burst is continuous with the next data burst, the state in which the packets in the data burst cannot be sent within the burst period, that is, the data It can be considered that the transmission rate exceeds the transmission rate in the distribution network. In the data transmission system of the present invention, paying attention to this point, the ratio between the data burst interval and the data burst transmission period is calculated. To notify the transmitting device 100 that the rate has been exceeded. When the rate monitoring unit 120 of the transmission device 100 receives a rate excess notification from the reception device 200, the rate monitoring unit 120 controls the rate control unit 130 to reduce the input data rate to the transmission device 100. As described above, the data transmission system of the present invention detects that the data transmission rate is approaching the allowable transmission rate of the distribution network before the packet discard occurs, and performs feedback.

  FIG. 6 shows an example of packet discard due to the restriction of burstiness in an embodiment of the present invention. When the allowable data amount of the data burst exceeds the burst property allowed by the policing or buffer amount of the distribution network 300, packet discarding occurs in the distribution network 300 as shown in FIG. The packet discard that occurs in this manner is steadily generated at the end of the data burst when the data size of the data burst exceeds a certain value. In the receiving apparatus 200, however, the packet discard for the data position in the data burst is performed. By observing the cumulative distribution of discards, a packet discard notification is transmitted to the transmitting apparatus 100 when packet discards occur at the end of the data burst continuously and with high probability. The rate monitoring unit 120 of the transmission apparatus 100 that has received the packet discard notification performs control so as to reduce the allowable data amount of the data burst.

  Here, since the transmission band of the network is independent of the restriction on the burst property, in the transmission device 100 of the present invention, when the allowable data amount of the data burst is reduced, the output period of the data burst is the same. Control is performed such that the maximum output rate is maintained by reducing the rate. Further, when there is a time granularity restriction regarding the control of the packet output interval, the transmission time interval is controlled so as not to be less than the minimum period. In a data transmission system implemented by software implementation, the minimum period is limited by interrupts and process schedule time accuracy. When the output cycle reaches the limit value, the maximum output rate is reduced in proportion to the allowable data amount. This reflects the performance limit of the transmission device 100.

  FIG. 7 is a flowchart of processing for packet discard according to an embodiment of the present invention, and shows processing for a packet discard notification received from the receiving device 200 in the transmitting device 100.

  When the rate monitoring unit 120 receives the packet discard notification from the receiving apparatus 200 (step 101), the rate monitoring unit 120 measures the frequency of occurrence of the packet discard with respect to the position in the data burst, and discard occurs with high probability at the end of the data burst. If yes (step 102, Yes), the rate controller 130 is controlled so as to reduce the allowable data amount of the data burst (step 103). Further, when the allowable data amount is reduced, if the data burst transmission period is equal to or greater than a certain value (step 104, Yes), the data burst transmission period is reduced in proportion to the reduction ratio of the allowable data amount (step 104). 105). As a result, the amount of data output at a time can be reduced by shortening the output cycle and outputting data in small increments. If it is less than the burst output cycle limit (step 104, No), the maximum output rate is reduced in proportion to the allowable data amount (step 106).

  Next, the rate control unit 120 of the transmission device 100 will be described.

  FIG. 8 is an example of data input rate control according to an embodiment of the present invention, and shows an example of input rate control by the rate control unit 130 of the transmission apparatus 100. First, when the amount of data in the input buffer 111 exceeds a certain value in the data transmission unit 110, control is performed to reduce the rate. With this function, control can be performed so that the data input rate to the transmission device 100 does not exceed the maximum transmission rate allowed by the distribution network 300. Furthermore, when the rate monitoring unit 120 receives a notification of excess rate from the receiving device 200, the rate monitoring unit 120 controls the rate control unit 130 to limit the input rate to the transmitting device 100 so as to reduce the rate. With this function, when the data transmission rate approaches the allowable data band of the distribution network 300, control can be performed to reduce the data transmission rate.

[Second Embodiment]
In the present embodiment, a case will be described in which transmitting apparatus 100 does not receive an over-rate notification from receiving apparatus 200.

  When the rate control unit 130 of the transmission device 100 of the present invention does not receive a rate excess notification from the reception device 200, the rate control unit 130 performs control to slightly increase the data rate. Thereby, when the surplus bandwidth of the distribution network 300 increases, the transmission rate is increased at a constant rate. With this function, it is possible to restore the data transmission rate when the congestion of the distribution network 300 recovers and the surplus bandwidth increases. Furthermore, it is possible to perform transmission using the available bandwidth of the distribution network 300 effectively. In this data transmission system, control is performed in the receiving apparatus 200 so that the ratio between the data burst interval and the data burst transmission cycle does not become a certain value or less, so the transmission rate is set so as to secure a certain amount of surplus bandwidth of the distribution network 300. Adjust. Even in a transmission protocol such as TCP, a technique of searching for an allowable transmission band by increasing the data transmission rate is used. However, in the data transmission system of the present invention, the control is not based on packet discard, and the rate is reduced. However, it is different that extreme control such as halving the window size is not performed.

[Third Embodiment]
In this embodiment, a case where there are a plurality of receiving apparatuses for one transmitting apparatus will be described.

FIG. 9 shows the configuration of a data transmission system in the case where there are a plurality of receiving apparatuses in the third embodiment of the present invention. When there are a plurality of receiving apparatuses 200 ₁ to 200 _n , data can be efficiently transmitted by multicast. on the other hand. Since the packet discard notification and the rate excess notification notified from the receiving devices 200 ₁ to 200 _n are individually notified for each receiving device, the transmitting device 100 has the smallest allowable burst property and the usable data. It is possible to control the parameters according to the receiving apparatus having the smallest transmission band. Furthermore, since the transmission device 100 can know from which reception device the notification is received from the transmission source address and the transmission source identifier included in the notification from the reception device, it is a bottleneck in the distribution network. The receiving device can be specified.

[Fourth Embodiment]
In the present embodiment, an example of rearranging the data order of packets will be described.

  FIG. 10 shows a configuration of a data transmission unit having a packet rearrangement function in the fourth embodiment of the present invention. The data transmission unit 110 of the transmission apparatus 100 shown in the figure has a configuration in which a packet rearrangement unit 113 is added to the function of the data transmission unit 110 of FIG.

  As shown in FIG. 6 described above, when a data burst is transmitted, a load is applied to the network as the end of the data burst is reached. Therefore, the probability of packet discard occurring at the end of the data burst increases. In consideration of this point, the packet rearrangement unit 113 can reduce the influence of data discard by arranging highly important data in a portion close to the head of the data burst. By attaching a sequence number to a packet, the packet order rearranged in the data transmission unit 110 can be restored to the original in the data reception unit 210.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims.

DESCRIPTION OF SYMBOLS 100 Transmission apparatus 110 Data transmission part 111 Input buffer 112 Packet output part 113 Packet rearrangement part 120 Rate monitoring part 130 Rate control part 200 Reception apparatus 210 Data reception part 220 Excess rate detection part 300 Distribution network

Claims (8)

A data transmission system comprising a transmitting device, one or more receiving devices, and a distribution network,
The transmitter is
Buffering the input packet, for each transmission interval, taking out a plurality of packets configured with an allowable data amount or less from the buffered packets, continuously sending them as data bursts to the distribution network, A data transmission means for notifying the receiving apparatus of a data burst transmission period and a leading packet position;
When a rate excess notification is received from the receiving device, or when the amount of data in the buffer of the data transmitting means reaches a certain level, control is performed to reduce the data input rate to the transmitting device. Rate control means ;
When receiving the packet discard notification before Symbol receiving device measures the frequency of occurrence relative to the position of the data within a burst of packet discard, when the waste occurs in high probability in a data burst end portion, said data burst The rate control means is controlled to control so as to reduce the allowable data amount, and when the allowable data amount is reduced, if the data burst transmission cycle is more than a certain value, the data burst transmission cycle is set. Rate monitoring means for reducing the proportion of allowable data in proportion to the reduction rate;
Have
The receiving device detects the start position of a data burst from an input packet, discards a packet in the data burst, and sets a data burst interval that is an interval from the last packet of the data burst to the start of the next data burst. Data receiving means to detect;
If the packet discard is detected, the ability to detect a function of transmitting a packet discard notification to the rate monitoring unit of the transmission device, that the ratio of the data burst transmission cycle and the data burst interval becomes constant less And an over-rate detection means including a function of transmitting an over-rate notification to the rate monitoring means when it continues for a certain number of times,
A data transmission system comprising: The rate control means of the transmitter is
The rate adjustment means for controlling to increase the input data rate to the transmission apparatus at a constant rate when a rate excess notification is not received when a predetermined number of data bursts are transmitted. Data transmission system. The transmitter is
When transmitting data to a plurality of receiving devices, if the rate excess notification and the packet discard notification are notified from any of the receiving devices, the rate monitoring unit and the rate control unit are executed. The data transmission system according to claim 1, further comprising means for determining a receiving device in which an excess of rate and packet discard have occurred by determining a notification source. Data transmission means
A packet rearranging means for rearranging a packet sending order so that a packet having high importance in the data burst becomes the head of the data burst;
The data receiving means includes
The data transmission system according to claim 1, further comprising means for restoring the order of packets received from the data transmission means. A data transmission method for controlling and distributing a transmission rate according to an excess bandwidth of a distribution network,
In a data transmission system constituted by a transmission device, one or a plurality of reception devices, and the distribution network,
The transmission device includes data transmission means, rate monitoring means, rate control means,
The receiving apparatus has data receiving means, rate excess detecting means,
The data transmission means of the transmission apparatus buffers the input packet, and extracts a plurality of packets configured with an amount less than or equal to the allowable data amount from the buffered packets at each transmission interval, and continuously uses them as a data burst. To transmit to the distribution network, and notify the receiving apparatus of the data burst transmission interval and the head packet position,
The data receiving means of the receiving device detects the start position of the data burst from the input packet, discards the packet in the data burst, and the interval from the last packet of the data burst to the start of the next data burst A data transmission step of detecting a data burst interval which is
When the rate excess detection means detects packet discard, it sends a packet discard notification to the rate monitoring means, and detects that the ratio between the data burst interval and the data burst transmission period is below a certain level. And an over-rate detection step of transmitting an over-rate notification to the transmitting device when it continues for a certain number of times, and
When the rate monitoring means of the transmitting apparatus receives the packet discard notification from the receiving apparatus, it measures the frequency of occurrence of packet discard with respect to the position in the data burst, and discard occurs with high probability at the end of the data burst. The rate control means is controlled to reduce the allowable data amount of the data burst. A rate monitoring step for reducing the burst transmission period in proportion to the reduction rate of the allowable data amount;
When the rate control means of the transmitting device receives a rate excess notification from the receiving device, or when the amount of data in the buffer of the data transmitting device reaches a certain level or more, data input to the transmitting device A rate control step for controlling to reduce the rate;
The data transmission method characterized by performing. In the transmitter,
6. The rate control means controls so as to increase an input data rate to the transmission device at a constant rate when the rate control means transmits a predetermined number of data bursts and does not receive the rate excess notification. The data transmission method described. In the transmitter,
When transmitting data to a plurality of receiving devices, if the rate excess notification and the packet discard notification are notified from any of the receiving devices, the rate monitoring step and the rate control step are executed. 6. The data transmission method according to claim 5, wherein a receiving device in which an excess of a rate and a packet discard have occurred is identified simultaneously by determining a notification source. In previous Kioku communication apparatus,
The data transmission means rearranges the packet transmission order so that the packet having high importance in the data burst becomes the head of the data burst,
In previous Ki受 communication apparatus,
6. The data transmission method according to claim 5, wherein the order of packets received from the data transmission means is restored.

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