JP2006174298A - DATA DISTRIBUTION METHOD, RELAY DEVICE, COMPUTER PROGRAM, AND RECORDING MEDIUM CONTAINING THE COMPUTER PROGRAM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce lost packets that cannot be repaired even when communication path conditions change quickly by increasing the responsiveness of redundancy update to changes in communication path conditions.
SOLUTION: Used in a communication network that performs multicast distribution in which the same data is distributed from a transmission device 10 to a plurality of reception devices 40 via one or more relay devices 20, and is generated in a communication channel by a redundant encoding method. In the data distribution method for repairing packet loss, the relay device 20 constantly monitors the packet loss state, calculates a redundancy suitable for the downstream receiving device 40 or the relay device 20, and uses the upstream transmitting device as the required redundancy. 10 or the relay device 20.
[Selection] Figure 1

Description

  The present invention relates to a data distribution method, a relay apparatus, a computer program, and a computer for repairing packet loss that occurs in a communication path and improving distribution quality in multicast in which the same data is distributed from a transmitting apparatus to a plurality of receiving apparatuses. The present invention relates to a recording medium on which a program is recorded.

  In recent years, there is an increasing demand for applications that require multicast, such as multi-point video streaming. As a protocol for realizing multicast in an IP (Internet Protocol) network based on packet communication, IP multicast, application layer multicast, and the like (for example, see Patent Document 1) have been proposed. In these methods, a packet distributed from a transmission device is delivered to a plurality of reception devices by duplicating it in a multicast router arranged in the network.

  However, in a best-effort network such as the Internet, packet loss frequently occurs, which may lead to deterioration in distribution quality. In order to improve this quality degradation in multicast distribution, several methods have already been proposed (see, for example, Non-Patent Document 1). Many of these methods are based on ARQ (Automatic Repeat reQuest) which is repaired by retransmitting a packet lost in a communication path.

  In ARQ, when a packet loss occurs, a retransmission request is transmitted from the reception device to the retransmission device, and the retransmission device that receives this retransmits the lost packet to the reception device. That is, at least a round-trip propagation delay between the receiving device and the retransmission device is required for retransmission, and the data reception delay becomes large in a large-scale network such as the Internet. Also, as the number of receiving devices increases, the frequency of retransmission requests also increases, increasing the processing load on the retransmission devices.

  On the other hand, there is a method called FEC (Forward Error Correction) that repairs lost packets by using a redundant encoding method. In FEC, data to be transmitted is encoded and transmitted, and even if packet loss occurs on the communication path, the original data is restored by decoding at the receiving device. In FEC, lost packets can be repaired only by processing in the receiving apparatus, so that reception delay can be reduced as compared with ARQ described above. Also, since retransmission is not required, the load is not concentrated on a specific device, and the scalability with respect to the number of receiving devices is excellent.

For example, an RS (Reed-Solomon) code or an LT (Lube Transform) code is used as the FEC encoding method. As an example, this RS code has the properties of a systematic code and an optimal code.
The systematic code is a property that the original data is included in the encoded data. That is, when k packets are encoded with the RS code, the original k packets and h redundant packets are obtained. Here, the ratio (h / k) between the number of redundant packets and the original number of packets is referred to as redundancy.

The greater the redundancy, the greater the number of redundant packets and the greater the distribution bandwidth. That is, if the redundancy is increased too much, useless distribution bandwidth is consumed. An RS code can be encoded by setting an arbitrary redundancy.
The optimum code is a property that the number of redundant packets necessary for repairing a certain amount of lost packets is minimum. Specifically, when h redundant packets are generated, up to h lost packets can be repaired. If more than h packets are lost, they cannot be decoded and the lost packets cannot be repaired.

  As described above, if the redundancy is too small, the lost packet cannot be repaired, and if the redundancy is too large, useless distribution bandwidth is consumed. For this reason, there is an optimum value for the degree of redundancy that varies depending on channel conditions such as the packet loss rate and channel capacity. In order to effectively use the FEC, this redundancy setting value is important.

  In unicast (one-to-one communication), a method called AFEC (see Non-Patent Document 2) that adaptively changes redundancy is proposed. In AFEC, the redundancy suitable for the channel condition is calculated based on the packet loss rate measured in the receiving device, and this redundancy is used when encoding the distribution data. Can be delivered. In addition, by repeating this redundancy calculation, it is possible to cope with changes in the communication path status over time.

On the other hand, when considering multicast that is one-to-many communication, in a heterogeneous network such as the Internet, the communication path status differs for each receiving device, and therefore there is redundancy suitable for each receiving device. Considering that the transmitting device adjusts the redundancy of the receiving device like AFEC, it is necessary for the transmitting device to distribute data with different redundancy by the number of receiving devices, and the scalability that is the advantage of multicast is lost. End up.
JP 2003-032300 A JC Lin and S. Paul (JC C. Lin, S. Paul), “RMTP: A reliable multicast transport protocol”, Proc. IEEE INFOCOM 1996 (IEEE Infocom 1996), p. 1414- 1424, March 1996 K. Park and W. Wang, “AFEC: An adaptive forward error correction protocol for end-to-end transport of real-time traffic” Possible Transmission Error Correction Protocol ”, in Proc. Int. Conf. Computer Communications and Networks, Lafayette, LA (Lafayette, Louisiana, USA), October 1997

  On the other hand, it is possible to improve the delivery quality for each receiving device even when the communication channel condition is inhomogeneous, with the aim of improving delivery quality in multicast with the low repair delay and high scalability that are the advantages of FEC The present inventor has already proposed a method of distributing at a redundancy suitable for each receiving device by adjusting the redundancy at the relay device (Japanese Patent Application No. 2003-295308).

In this method, first, each receiving apparatus calculates the redundancy suitable for the communication path condition in the same manner as AFEC and requests it upstream.
The relay apparatus receives different requested redundancy levels from a plurality of downstream receiving apparatuses, and transfers only the maximum value among them to the upstream. As a result, the transmitting device is notified of only the maximum value of the required redundancy from all receiving devices.
The transmission apparatus encodes the distribution data with the maximum required redundancy. Then, the relay device adjusts and transfers the redundancy of the distribution data from the upstream to that required by each downstream receiving device or relay device.

This makes it possible to distribute with redundancy suitable for each receiving apparatus. Here, the redundancy adjustment in the relay apparatus is performed by selectively discarding redundant packets in the distribution data and changing the number of redundant packets. Since this is possible only by packet transfer control, it is characterized by a low processing load.
However, in this method, there is a case where a round trip propagation delay between the transmitting and receiving apparatuses is required until the receiving apparatus changes the required redundancy and receives the data reflecting the request.
Considering a network with a large delay such as the Internet, this is because the update of the redundancy cannot follow the time change of the communication path condition, and the loss of packets that cannot be repaired increases.

  As described above, in the method of performing redundancy adjustment for each receiving device in accordance with the redundancy request from the receiving device in multicast using FEC, the update of the redundancy is performed in the time of the channel status when the change in the communication channel status is fast. There is a problem that the number of lost packets that cannot be corrected and cannot be repaired increases.

  The present invention has been made in view of such circumstances, and by reducing the responsiveness of redundancy update to changes in communication path conditions, it is possible to reduce lost packets that cannot be repaired even when the communication path conditions change quickly. It is an object to provide a data distribution method, a relay device, a computer program, and a recording medium on which the computer program is recorded.

In order to achieve the above object, the invention according to claim 1 is used in a communication network that performs multicast distribution in which the same data is distributed from a transmitting device to a plurality of receiving devices via one or more relay devices, and is redundant. In a data distribution method for repairing packet loss that occurs in a communication path by an encoding method, the relay device constantly monitors the packet loss state, calculates redundancy suitable for a downstream receiving device or relay device, and requests The redundancy is notified to the upstream transmission apparatus or relay apparatus.
According to the first aspect of the present invention, when the communication path condition fluctuates and the redundancy needs to be updated, the relay device immediately sets the required redundancy without waiting for the request device to update the requested redundancy. By updating, it is possible to improve the responsiveness to fluctuations in communication path conditions.

Further, the invention according to claim 2 is the data distribution method according to claim 1, wherein the relay device is configured such that the redundancy of distribution data received from an upstream transmission device or relay device is a downstream reception device or relay. Only when it is less than the maximum value of a plurality of requested redundancy from the device, it notifies the upstream transmitting device or relay device of the redundancy greater than the maximum value of the requested redundancy from the downstream as the requested redundancy. Features.
According to the second aspect of the present invention, when the relay device cannot satisfy the redundancy required by the downstream receiving device or the relay device, the relay device sets the redundancy higher than the request redundancy from the downstream as the request redundancy. By notifying the transmission device or the relay device, it is possible to request the upstream transmission device or the relay device for redundancy that satisfies the downstream request.

Further, the invention according to claim 3 is the data distribution method according to claim 2, wherein the relay device includes a maximum value of a plurality of request redundancy levels from a downstream receiving device or relay device, and an upstream transmitting device. Alternatively, the requested redundancy to be notified to the upstream transmission device or relay device is determined based on the difference from the redundancy of the distribution data received from the relay device.
According to the third aspect of the present invention, the relay device has a difference between the maximum value of a plurality of requested redundancy from the downstream receiving device or the relay device and the redundancy of the distribution data from the upstream, that is, the communication path status. Since the required redundancy is determined based on the redundancy that is insufficient due to the fluctuation, it is possible to request the upstream transmission apparatus or relay apparatus for the redundancy suitable for the current communication path condition.

The invention according to claim 4 is the data data distribution method according to any one of claims 1 to 3, wherein the relay device has a redundancy of distribution data received from an upstream transmission device or relay device. Only when the request redundancy from the downstream receiving device or relay device is greater than or equal to the maximum value, requesting the upstream transmission device or relay device to request the maximum request redundancy from the downstream as the request redundancy. Features.
According to the invention described in claim 4, when the relay device can satisfy the redundancy required by the downstream receiving device or relay device by the distribution data received from the upstream transmitting device or relay device, Only the maximum value of the required redundancy can be transferred to the upstream transmission device or relay device, and excessive redundancy cannot be requested from the upstream transmission device or relay device.

The invention according to claim 5 is used in a communication network for performing multicast distribution in which the same data is distributed from a transmitting apparatus to a plurality of receiving apparatuses via one or more relay apparatuses, and is communicated by a redundant encoding method. A relay device used to implement a data distribution method for repairing packet loss that occurs on a route, based on the loss status of data distributed from an upstream transmitting device or relay device using a redundant encoding method It has a request redundancy processing unit that calculates a suitable redundancy and notifies the upstream transmission device or relay device of the redundancy as the required redundancy.
The relay apparatus according to the present invention having the above configuration is used in a communication network for performing multicast distribution in which the same data is distributed from a transmitting apparatus to a plurality of receiving apparatuses via one or more relay apparatuses. When used to implement a data distribution method that repairs packet loss that occurs on the communication path, the required redundancy is updated by the receiving device when the communication path conditions change and the redundancy needs to be updated. Without waiting, the relay apparatus can immediately update the required redundancy, and the responsiveness to fluctuations in the communication path condition can be improved.

The invention according to claim 6 is used in a communication network for performing multicast distribution in which the same data is distributed from a transmitting apparatus to a plurality of receiving apparatuses via one or more relay apparatuses, and is communicated by a redundant encoding method. A computer program executed on a relay device used to implement a data distribution method for repairing packet loss occurring on a route, based on the loss status of distribution data received from an upstream transmission device or relay device The computer is caused to execute a step of calculating a suitable redundancy, and a step of notifying the calculated redundancy to the upstream transmission device or relay device as a required redundancy.
By causing the computer constituting the relay device to execute the computer program described above, when the communication path state fluctuates and the redundancy needs to be updated, the relay device does not wait for the required redundancy to be updated by the receiving device. However, it is possible to immediately update the required redundancy, and to improve the responsiveness to fluctuations in communication path conditions.

The invention according to claim 7 is used in a communication network for performing multicast for distributing the same data from a transmitting device to a plurality of receiving devices via one or more relay devices. A computer-readable recording medium recording a computer program executed on a relay device used to implement a data distribution method for repairing packet loss that occurs in the network, and received from an upstream transmission device or relay device Recording a computer program for causing a computer to execute a step of calculating a suitable redundancy based on a loss situation of distribution data and a step of notifying the calculated redundancy to a upstream transmission device or relay device as a required redundancy It is characterized by doing.
Receiving device when communication path condition fluctuates and redundancy needs to be updated by reading and executing the computer program from a recording medium on which the computer program is recorded by a computer constituting the relay device Thus, the relay device can immediately update the requested redundancy without waiting for the requested redundancy to be updated, and the responsiveness to fluctuations in the communication path status can be improved.

  As described above, according to the present invention, when performing multicast distribution using FEC, the relay device immediately updates the requested redundancy without waiting for the requested device to update the requested redundancy. It is possible to increase the responsiveness to changes in road conditions and reduce the number of lost packets that cannot be repaired.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A data distribution method according to an embodiment of the present invention is used in a communication network that performs multicast distribution in which the same data is distributed from a transmitting device to a plurality of receiving devices via one or more relay devices, and is based on a redundant encoding scheme. In the data distribution method for repairing packet loss that occurs in a communication path, the relay device constantly monitors the packet loss state, calculates a redundancy suitable for a downstream receiving device or relay device, The transmission device or the relay device is notified.

  FIG. 1 shows a distribution form of a communication system to which the present invention is applied. Here, packet communication in the IP network is assumed. Then, data distributed from the transmission device 10 is received by the plurality of reception devices 40 via the plurality of relay devices 20 and the multicast router 30 using the multicast protocol.

The multicast protocol is the aforementioned IP multicast or application layer multicast. The multicast router 30 is a router corresponding to the multicast protocol to be used.
The relay device 20 is a router corresponding to a multicast protocol used for distribution, and a device having an additional function described later.
In FIG. 1, one or two relay apparatuses 20, multicast routers 30, or receivers 40 are connected downstream of the relay apparatus 20 and the multicast router 30, but this is for simplification of description. In reality, more units can be connected. This is limited by the multicast protocol or the performance of the relay device 20 or the multicast router 30.

  FIG. 2 is a block diagram showing functional expansion of the inside of the relay device 20 constituting the communication system according to the embodiment shown in FIG. In FIG. 2, the transmission device 10 is connected upstream of the relay device 20, but this may be the relay device 20 or the multicast router 30 as in FIG. In FIG. 2, two receiving devices are connected downstream of the relay device 20, but this may be a plurality of relay devices 20, multicast routers 30, or receiving devices 40, as in FIG. 1.

  The relay device 20 receives a packet distributed from an upstream device, and also transmits a redundancy request packet upstream, and a packet replication that replicates the received packet by the number of downstream devices to be transferred. Unit 22, a redundancy adjusting unit 23 for adjusting the redundancy of the duplicated packet, and a communication I for transmitting the redundancy adjusted packet to the downstream device and receiving the redundancy request packet from the downstream device / F24, a packet loss detection unit 25 that detects packet loss from a distribution packet received from the upstream, and a request redundancy process that determines a request redundancy to notify the upstream based on a downstream redundancy request and the number of lost packets Part 26.

  FIG. 3 shows an example of a distribution form in a communication system to which the present invention is applied when the communication channel condition varies. As shown in the figure, a case is considered where data is distributed from the transmission device 10 to three reception devices 40 (these are referred to as reception devices 40a, 40b, and 40c). Packets for data distribution are multicast from the transmission device 10 to the reception device 40a via the relay device 20, and to the reception devices 40b and 40c via the relay device 20 and the multicast router 30 downstream thereof. .

The propagation delay from the transmission device 10 to the relay device 20 is 10 msec, and the propagation delay from the relay device to the reception devices 40a, 40b, and 40c is 20 msec.
First, multicast of distribution data from the transmission device 10 to the relay device 20 is started. Here, since the transmitter 10 has not yet been notified of the requested redundancy from the downstream side, for example, 1% is used to perform encoding with a predetermined appropriate redundancy and distribute the data.

In the relay device 20, the packet distributed from the upstream transmission device 10 is copied and transferred to the reception device 40 a and the multicast router 30. Here, in the redundancy adjustment processing in the redundancy adjustment unit 23, since the required redundancy is not yet notified from the downstream, the redundancy is adjusted to a predetermined appropriate redundancy, for example, 1%, or redundancy. Do not adjust the degree.
The multicast router 30 duplicates the distribution data transferred from the relay device 20 and transfers it to the receiving devices 40b and 40c.

  The receiving devices 40a, 40b, and 40c receive the packet transferred from each upstream device, decode it, and obtain the original distribution data. Further, packet loss is detected from the received packet. Packet loss is detected, for example, by monitoring the sequence number in the received packet by the receiving device 40 by including a sequence number when generating a packet in the transmitting device 10, and detecting whether the number is interrupted. This can be achieved.

  Then, for example, every second, the packet loss rate is obtained from the average value of the number of lost packets periodically every predetermined time, and further, the requested redundancy is obtained based on this packet loss rate and notified upstream. . As a method for determining the required redundancy from the packet loss rate, for example, the same method as the AFEC described above is used.

  Here, it is assumed that packet loss occurs due to congestion or the like in each communication path, and the receiving devices 40a, 40b, and 40c detect different amounts of packet loss. Each of the receiving devices 40a, 40b, and 40c calculates a redundancy that can repair this packet loss, and notifies the upstream relay device 20 as the required redundancy. Here, for example, it is assumed that the receiving device 40a notifies the requested redundancy of 7%, the receiving device 40b of 5%, and the receiving device 40c of 2%.

The relay device 20 stores the required redundancy from the receiving devices 40a, 40b, and 40c, respectively. Then, the required redundancy of 7%, which is the maximum value, is transferred to the upstream transmitting device 10.
The transmission apparatus 10 distributes data by changing the redundancy of encoding by FEC to 7% in accordance with the redundancy request.

  In the relay device 20, the redundancy of the distribution data from the upstream is adjusted and transferred to the requested redundancy from the stored receiving devices 40a, 40b, and 40c. That is, the redundancy is adjusted to 7% for the reception device 40a, 5% for the reception device 40b, and 2% for the reception device 40c. The redundancy is adjusted by adjusting the number of redundant packets transferred. For example, in order to adjust the required redundancy of the receiving device 40b to 5%, only the number of redundant packets satisfying the redundancy of 5% are transferred.

In addition, the receiving devices 40b and 40c may distribute distribution data individually adjusted to 5% and 2% redundancy, respectively, or distribute only the data with 5% redundancy, which is the larger one, The multicast router 40 may be duplicated. The former can be distributed to the receiving devices 40b and 40c with the required redundancy. The latter is distributed to the receiving device 40c with a redundancy greater than the required redundancy, but since only a single data is distributed from the relay device, the distribution band is smaller than the former. Depending on the multicast protocol used, only one of these methods may be used.

With these operations, distribution with redundancy suitable for each of the receiving devices 40a, 40b, and 40c is possible.
Here, let us consider a case where the state of the communication path in the vicinity of the transmission apparatus 10 has changed and the number of lost packets has increased. In the method (Japanese Patent Application No. 2003-295308) already proposed by the present inventor before the filing of the present application, the number of lost packets increases in the vicinity of the transmission device 10, the data reaches the reception devices 40a, 40b, and 40c, and the reception device 40a. , 40b, and 40c recalculate the requested redundancy, notify the new requested redundancy upstream, and notify the transmitting device 10 of the requested redundancy and update the delivery data redundancy. 10 and a round-trip propagation delay between the receivers 40a, 40b and 40c, 60 msec is required.

In the case where the fluctuation of the communication path is large or the situation where a new communication path fluctuation occurs within this 60 msec, the update of the redundancy cannot follow the fluctuation of the communication path, and the number of lost packets that cannot be repaired increases.
On the other hand, in the present invention, when the number of lost packets increases near the transmitting device 10 and the data reaches the relay device 20, it is determined that the relay device 20 cannot satisfy the required redundancy from each receiving device, A larger required redundancy is immediately notified to the transmission apparatus 10, and the transmission apparatus 10 updates the redundancy of the distribution data.

For this reason, the time required from the change of the communication path to the update of the redundancy is 20 msec, which is a significant reduction compared with the method (Japanese Patent Application No. 2003-295308) already proposed by the present inventor before the filing of the present application. It is possible to reduce the number of lost packets that cannot be performed.
Here, the redundancy that the relay device 20 notifies the transmitting device 10 is the difference between the maximum value of the requested redundancy from the downstream receiving devices 40a, 40b, and 40c and the redundancy of the distribution data received from the upstream, that is, It can be determined based on the redundancy that has become insufficient due to fluctuations in communication path conditions. For example, the request redundancy degree notified before is added with this difference and notified as a new request redundancy degree.

As a result, the relay apparatus can request an upstream transmission apparatus or relay apparatus for redundancy suitable for the current communication path condition.
The same operation is performed even in a configuration in which a plurality of relay devices 20 exist between the transmission device 10 and each reception device 40. In this case, when the state of the communication path changes, the relay device 20 located downstream of the changed communication path immediately notifies the upstream of the redundancy update.

In addition, the relay device can only receive from the downstream if the redundancy of the distribution data received from the upstream transmission device or relay device is equal to or greater than the maximum value of the plurality of required redundancy from the downstream reception device or relay device. The maximum value of the requested redundancy may be requested to the upstream transmitting device or relay device as the requested redundancy.
With this configuration, when the relay device can satisfy the redundancy requested by the downstream receiving device or the relay device by the distribution data received from the upstream transmitting device or the relay device, the requested redundancy from the downstream is obtained. Can only be transferred to the upstream transmission device or relay device, so that excessive redundancy is not required from the upstream transmission device or relay device.

  As described above, according to the embodiment of the present invention, when the communication channel state fluctuates and the redundancy needs to be updated, the relay device does not wait for the required redundancy to be updated by the receiving device. By immediately updating the required redundancy, it is possible to improve the responsiveness to changes in the communication path status.

  Note that the transmission device 10, the relay device 20, the multicast router 30, and the reception device 40 described above have a computer system therein. The above-described operation process is stored in a computer-readable recording medium in the form of a program, and the computer system reads and executes this program to perform the above processing. The computer system here includes an OS and hardware such as peripheral devices.

In addition to ROM, “computer-readable recording medium” refers to a portable medium such as a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a storage device such as a hard disk built in a computer system. That means.
Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system serving as a system or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding a program for a certain period of time are also included.

The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

The block diagram which shows the delivery form of the communication system with which the data delivery method which concerns on this invention is applied. The block diagram which shows the specific structure of the relay apparatus in the communication system shown in FIG. The figure which shows an example of the delivery form when communication path conditions fluctuate in the communication system to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Transmitting device 20 ... Relay device 21, 24 ... Communication I / F
DESCRIPTION OF SYMBOLS 22 ... Packet duplication part 23 ... Redundancy adjustment part 25 ... Packet loss | disappearance detection part 26 ... Request redundancy processing part 30 ... Multicast router 40, 40a, 40b, 40c ... Receiver

Claims (7)

Data distribution that is used in a communication network that performs multicast distribution in which the same data is distributed from a transmitting device to a plurality of receiving devices via one or more relay devices, and that repairs packet loss that occurs in the communication path using a redundant coding scheme In the method
The relay device constantly monitors the packet loss state, calculates a redundancy suitable for a downstream receiving device or relay device, and notifies the upstream transmitting device or relay device as a requested redundancy. Delivery method.   The relay device is connected from the downstream only when the redundancy of the distribution data received from the upstream transmission device or relay device is less than the maximum value of the plurality of required redundancy from the downstream reception device or relay device. The data distribution method according to claim 1, wherein a redundancy greater than a maximum value of the requested redundancy is notified to the upstream transmitting device or relay device as the requested redundancy.   The relay device is based on a difference between a maximum value of a plurality of requested redundancy levels from a downstream reception device or relay device and a redundancy level of distribution data received from the upstream transmission device or relay device. The data distribution method according to claim 2, wherein the request redundancy to be notified to the relay apparatus is determined.   The relay device requests the request from the downstream only when the redundancy of the distribution data received from the upstream transmission device or the relay device is equal to or greater than the maximum value of the plurality of request redundancy from the downstream reception device or the relay device. 4. The data data distribution method according to claim 1, wherein a maximum value of redundancy is requested as a requested redundancy to an upstream transmission device or relay device. Data distribution that is used in a communication network that performs multicast distribution in which the same data is distributed from a transmitting device to a plurality of receiving devices via one or more relay devices, and that repairs packet loss that occurs in the communication path using a redundant coding scheme A relay device used to carry out the method,
Calculate the appropriate redundancy based on the loss of data distributed from the upstream transmission device or relay device using the redundancy coding method, and notify the upstream transmission device or relay device of the redundancy as the required redundancy A relay apparatus comprising: a required redundancy processing unit. Data distribution that is used in a communication network that performs multicast distribution in which the same data is distributed from a transmitting device to a plurality of receiving devices via one or more relay devices, and that repairs packet loss that occurs in the communication path using a redundant coding scheme A computer program executed on a relay device used to carry out the method,
Calculating a suitable redundancy based on the loss of distribution data received from an upstream transmitting device or relay device; and
Notifying the calculated redundancy as a required redundancy to an upstream transmitting device or relay device;
A computer program for causing a computer to execute. Data distribution that is used in a communication network that performs multicast distribution in which the same data is distributed from a transmitting device to a plurality of receiving devices via one or more relay devices, and that repairs packet loss that occurs in the communication path using a redundant coding scheme A computer-readable recording medium recording a computer program executed on a relay device used for carrying out the method,
Calculating a suitable redundancy based on the loss of distribution data received from an upstream transmitting device or relay device; and
Notifying the calculated redundancy as a required redundancy to an upstream transmitting device or relay device;
A recording medium for recording a computer program for causing a computer to execute.

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