JP2002330118A - Method for controlling data delivery, data delivery system, data delivery control program, and medium where data delivery program is stored - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible in data delivery to grasp the correct receiving state and optimize FEC redundancy according to the receiving state. SOLUTION: Original data and redundant data generated by performing FEC coding of the original data are delivered by the block from a sending computer 10 to a receiving computer 20. In this case, a response transmission means 23 is provided to the computer 20 to transmit a positive acknowledge to the computer 10 when the computer 20 is successful in restoring the original data even if it fails in receiving some blocks. This response includes information on blocks which are not received such as identifiers or the number of those blocks. An FEC coding parameter decision means 15 is provided to the computer 10 to decide redundancy of FEC coding in the data transmission from the following transmission on according to information returned from the computer 20 on blocks which are not received. In this way, FEC redundancy is optimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data distribution control for reliably transmitting file data such as text files, image files, video files, audio files, and program files from a transmitting computer to at least one receiving computer. The present invention relates to a method, a data distribution device, a data distribution control program, and a medium recording the data distribution control program.

[0002]

2. Description of the Related Art Reed is used as a forward error correction (FEC) code.
A conventional data distribution control method will be described below, taking as an example the case where a Solomon code is used.

FIG. 1 shows an example of a conventional data distribution apparatus (system) of this kind, in which a transmitting computer 1 and receiving computers 2-1, 2-2, 2-3 can use IP multicast. It is connected via a network 3.

The transmitting computer 1 divides the original data into a plurality of blocks (original blocks), encodes (NK) redundant blocks out of the K original blocks, and converts each of the receiving computers 2-1 to 2-1. In 2-3, these (NK) redundant blocks are also transmitted together with the K original blocks, that is, N blocks are transmitted.

When the receiving computers 2-1 to 2-3 can receive at least K arbitrary blocks out of the N blocks, the original blocks can be restored. Otherwise, the restoration of the original blocks fails. I do. The reception computers 2-1 to 2-3 transmit the reception results to the transmission computer 1
, The transmitting computer 1 retransmits the block according to the result.

Here, when only a negative acknowledgment indicating that the reception has failed as a reception result is used, a receiving computer that has successfully received, that is, a receiving computer that has successfully received all the original blocks and redundant blocks, or some blocks None of the receiving computers which failed to receive the original but could restore the original block by FEC did not transmit a negative acknowledgment, and the transmitting computer judged that the reception was successful based on the non-arrival.

When only an acknowledgment indicating successful reception is used as a reception result, or when both an acknowledgment and a negative acknowledgment are used, a receiving computer that has successfully received, that is, an original block and a redundant block The receiving computer that has successfully received all the blocks, or the receiving computer that failed to receive some blocks but was able to restore the original block by FEC, sends an acknowledgment indicating only that the receiving was successful, and the transmitting computer Determined that the reception was successful by its arrival.

FIG. 2 shows an example of a specific operation in a conventional data distribution control method. In this example, when the transmission computer 1 transmits data including five original blocks o1 to o5 to the reception computers 2-1 to 2-3, (1) two redundant blocks e1 and e2 are generated by FEC encoding. And (2) transmitting to the receiving computers 2-1 to 2-3.

The receiving computer 2-1 has failed to receive the original block o5, but has received six blocks in total, so that (3) the original blocks o1 to o5 can be restored. (4) An acknowledgment (ACK) is returned.

The receiving computer 2-2 comprises blocks o2, o
4, e1 has failed to be received, and the minimum number of 5 blocks required for restoration has not been received, so (3) restoration of the original block has failed. (4) Then, a negative acknowledgment (NACK) indicating that the reception of the blocks o2, o4, and e1 has failed is transmitted.

The receiving computer 2-3 has blocks o5 and e2.
Has failed, but since a total of five blocks have been received, (3) the original blocks o1 to o5 can be restored. (4) An acknowledgment (ACK) is returned.

[0012]

As described above, as the reception status of the receiving computer, whether the original block and the redundant block have all been received, or the reception of some blocks has failed, In the data distribution control method that returns an acknowledgment indicating only that the restoration was successful without discriminating whether or not the restoration was successful, the transmitting computer uses the data because it cannot accurately grasp the detailed reception status of the receiving computer. It has been difficult to determine whether the FEC redundancy, for example, the number of redundant blocks (NK), is appropriate for the current reception situation.

For example, ten original blocks (K =
10), a total of 13 redundant blocks (NK = 3) are transmitted, and a total of 13 blocks are received, as in the following (1) and (2), that is, (1) all receiving computers include redundant blocks. Situation where all blocks have been successfully received (2) Assuming that all receiving computers have failed to receive three packets, that is, only a minimum number of blocks have been successfully received, In the conventional method, the above (1), (2)
Cannot be distinguished, and it is considered that the optimization is excessive with respect to (1), so that optimization such as lowering the redundancy or increasing the redundancy with respect to (2) cannot be performed.

An object of the present invention is to provide a data distribution control method, a data distribution device, a data distribution control program, and a medium on which the data distribution control program is recorded, which enables accurate recognition of the reception status.

Another object of the present invention is to provide a data distribution control method, a data distribution apparatus, a data distribution control program, and a medium on which a data distribution control program capable of optimizing the FEC redundancy according to the reception situation. To provide.

[0016]

In order to achieve the above object, according to the present invention, a receiving computer fails to receive some blocks but fails to recover the original data when the original data is successfully restored. A response unit for transmitting an acknowledgment including reception failure block information such as a block identifier and the number of blocks for which reception failed to the transmission computer is provided, and the transmission computer receives an acknowledgment returned from the reception computer and a negative acknowledgment similar to the related art. And based on the reception failure block information,
An encoding parameter determining means for determining the encoding redundancy in the next and subsequent data transmissions is provided.

According to the above configuration, the receiving computer restores the original block if there is a block that failed to be received and the received block is necessary and sufficient for restoring the original block. An acknowledgment is returned to the transmitting computer together with the information on the block. The transmitting computer that has received the acknowledgment collects information on the blocks that failed to be received, which are included in the acknowledgment and the negative acknowledgment, and determines the coding redundancy in the next and subsequent block transmissions based on the information.

As described above, according to the present invention, it is possible to grasp the accurate reception state of a block including a receiving computer that has succeeded in restoration, and to perform encoding based on the state, so that redundancy can be minimized. As a result, efficient data distribution with little overhead is possible.

[0019]

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

FIG. 3 shows an embodiment of the data distribution apparatus according to the present invention.
0-1, 20-2, and 20-3 are connected via a network 3 that can use IP multicast,
The data transmitted from the transmitting computer 10 is transmitted to all the receiving computers 2
0-1 to 20-3 are broadcast simultaneously.
Each of the receiving computers 20-1 to 20-3 has the same configuration, and when not distinguished, it is represented by omitting "-" in the reference numeral and numerals below it.

FIG. 4 shows the details of the data distribution apparatus according to the present embodiment.
1, block transmitting means 12, response receiving means 13, block retransmitting means 14, and FEC coding parameter determining means 1
5 and the receiving computer 20 includes a block receiving unit 21 and F
An EC decoding unit 22 and a response transmission unit 23 are provided.
Here, Reed Solo is used as the FEC code.
An example in which a mon code is used will be described.

The FEC encoding means 11 performs the following based on the given transmission data and the FEC encoding parameters (N, K).
Generate K original blocks and NK redundant blocks. The block transmitting unit 12 transmits the block generated by the FEC encoding unit 11 to the receiving computers 20-1 to 20-3 using IP multicast or the like.

The response receiving means 13 comprises a receiving computer 20-1.
20-3, and notifies the block retransmitting means 14 and the FEC coding parameter determining means 15 of the reception status. The block retransmitting means 14 retransmits the reception failure block notified from the response receiving means 13 to the receiving computers 20-1 to 20-3.

The FEC coding parameter determining means 15
Based on the reception status notified from the response receiving unit 13, the next and subsequent FEC encoding parameters are determined and held.

The block receiving means 21 transmits the
Receives blocks sent from. FEC decoding means 2
2 restores the original block from the received block.

The response transmitting means 23 outputs a "lossless acknowledgment" when there is no block that has failed in reception and the FEC decoding is successful. If it succeeds, it receives a "lossy acknowledgment" including the information on the block that failed to receive, and if the block that failed to receive exceeds the minimum block required for restoring the original data and FEC decoding fails. A “negative acknowledgment” including the reception failure block information is transmitted to the transmission computer 10.

FIGS. 5 and 6 show an example of a specific operation according to the present embodiment. Hereinafter, an operation of changing the FEC redundancy according to the reception status of a block in the present embodiment will be described.

FEC encoding means 11 of transmission computer 10
From the five original blocks o1 to o5, (N,
K) = (9,5) to generate four redundant blocks e1 to e4, and these nine blocks are transmitted to the receiving computers 20-1 to 20-3 by the block transmitting unit 12.
It is transmitted to the destination by using multicast or the like.

The block receiving means 21 of the receiving computers 20-1 to 20-3 receives the block transmitted from the transmitting computer 10, and the FEC decoding means 22 restores the original block from the received block.

At this time, the receiving computers 20-1 and 20-3
Has successfully received all the blocks and has successfully restored the original block, the response transmitting means 23 returns a lossless acknowledgment. On the other hand, the receiving computer 20-
2 failed to receive block o4, but succeeded in receiving 5 or more blocks, and thus succeeded in restoration. The response transmission unit 23 returns an acknowledgment including the failure in receiving block o4. I do.

The response receiving means 13 of the transmitting computer 10 receives the responses from the receiving computers 20-1 to 20-3, and notifies the block retransmitting means 14 and the FEC coding parameter determining means 15 of the reception status. At this time, each receiving computer 20
Since no negative response is included in the response from -1 to 20-3, the block retransmitting means 14 does nothing.

The FEC coding parameter determining means 15
The number of failed reception blocks in the response from each of the receiving computers 20-1 to 20-3 is compared, and it is detected that the maximum value (the maximum number of failed reception blocks) is one. Current redundancy 4
Is larger than the maximum number of failed reception blocks, the redundancy is determined to be too high, and the next FEC redundancy is set to the maximum number of failed reception blocks, thereby reducing excessive redundant blocks.

Next, the transmission computer 10 generates one redundant block e1 in the same manner as described above by the FEC coding of the previously updated new redundancy (N, K) = (6, 5), and It is transmitted together with blocks o1 to o5.

At this time, the receiving computers 20-1 to 20-3 fail to receive the blocks o4, o2, and e1, respectively.
The acknowledgment including the success of the restoration and the failure of receiving the blocks o4, o2, and e1, respectively, is returned.

The transmission computer 10 detects from the responses that the maximum number of unsuccessfully received blocks is 1. Since the current redundancy 1 is equal to the maximum number of unsuccessfully received blocks, the redundancy is not appropriate. Thus, the FEC redundancy is not changed.

In the next distribution, the transmission computer 10
Generates one redundant block e1 as before, and transmits it together with the original blocks o1 to o5. At this time,
The receiving computer 20-1 fails to receive the blocks o3 and o4, and the receiving computer 20-3 outputs the blocks o1, o3 and o3.
Since the reception of e1 has failed and its number exceeds the redundancy, restoration of the original block has failed, and a negative acknowledgment including the respective reception failure block information is returned.

The receiving computer 20-2 is connected to the block o4
However, since five or more blocks have been successfully received, an acknowledgment including the failure of receiving the block o4 is returned.

At this time, the block retransmitting means 14 of the transmitting computer 10 retransmits the block corresponding to the reception failure block information included in the negative acknowledgment of the receiving computers 20-1 and 20-3. Further, the FEC coding parameter determination means 15 of the transmission computer 10 detects that the maximum number of failed reception blocks is 3 from each response, and the current redundancy 1 is smaller than the maximum number of failed reception blocks. Therefore, it is determined that the redundancy is low. By setting the next FEC redundancy to the maximum number of failed reception blocks of 3, the insufficient redundant blocks are supplemented.

FIG. 7 is a flowchart showing the processing procedure of the data distribution control in the present embodiment. Hereinafter, the processing of changing the FEC redundancy according to the block reception status in the present embodiment will be described.

First, the processing procedure of the transmission computer 10 will be described.

(Step S11) The transmission computer 10
The FEC encoding parameter is obtained from the EC encoding parameter storage area 16.

(Step S12) FE of the transmission computer 10
The C encoding means 11 is based on the FEC encoding parameters,
The original block is FEC encoded to generate a redundant block.

(Step S13) The block transmitting means 12 of the transmitting computer 10 transmits the original block and the redundant block to the receiving computer using multicast or the like.

(Step S14) The response receiving means 13 of the transmitting computer 10 receives the response from each receiving computer and obtains the number of reception failure blocks of each receiving computer. If there is a negative response, the block retransmitting means 14 retransmits the block.

(Step S15) FE of the transmission computer 10
The C coding parameter determination means 15 obtains the maximum value from the number of failed reception blocks of each receiving computer obtained in step S14, and stores the FEC coding parameter in order to use the value as the redundancy at the next data transmission. Update area 16.

Further, as another example of step S15, that is, as step S150, the FEC coding parameter determination means 15 of the transmission computer 10 compares the maximum number of failed reception blocks with the redundancy (S151). The redundancy is not changed (S152). If the redundancy is higher, the redundancy is reduced by one (S153). Conversely, if the redundancy is lower, the redundancy is changed to the maximum number of reception failure blocks. (S154).

There is also a method of making use of statistical prediction as described below. That is, the-time reception failure rate: L _n-previous to the reception failure rate of the mean value: AveL _n-1 · current reception failure rate of the mean value: Avel _n of-up to the previous Yasunobu failure rate deviation: devl _{n -1} · Deviation of the current reception failure rate: DevL _n · Constant: α, δ, γ, and assuming that the next reception failure rate prediction value: L _{n + 1} , AveL _n = α × AveL _n-1 + ( 1−α) × L _n DevL _n = (1−δ) × | L _n −AveL _n | + δ × D
evL _n−1 L _{n + 1} = AveL _n + γ × DevL _n

Next, the processing procedure of the receiving computer 20 will be described.

(Step S21) The block receiving means 21 of the receiving computer 20 receives a block from the transmitting computer 10.

(Step S22) FE of the receiving computer 20
The C decoding unit 22 attempts to restore the original block from the received block.

(Step S23) The response transmitting means 23 of the receiving computer 20 determines whether or not the restoration has succeeded.

(Step S24) If the restoration is successful,
The response transmission unit 23 of the reception computer 20 further determines whether there is a reception failure block.

(Step S25) If there is no reception failure,
The response transmitting means 23 of the receiving computer 20 returns a lossless acknowledgment indicating that there is no reception failure.

(Step S26) If there is a reception failure,
The response transmitting means 23 of the receiving computer 20 returns an acknowledgment with loss including information on the block whose reception has failed.

(Step S27) On the other hand, if the restoration has failed, the response transmitting means 23 of the receiving computer 20 returns a negative response including information on the block for which the reception has failed.

In the above embodiment, the FEC code is Re
Although the description has been made on the premise that the ed Solomon code is used, a parity code is used as the code, the original data is simply overlapped a plurality of times, and the Tor code is used.
The present invention is also applicable to a case where a more advanced encoding such as a nado code is performed, and the present invention does not limit the encoding.

Further, the present invention can be applied not only to the case where redundant data is stored as a block separate from the original block but also to the case where the redundant data is embedded in the original block as in the above embodiment. Is not limited.

Although the above embodiment is an example of data distribution to a plurality of receiving computers using multicast, the present invention can also be applied to unicast data distribution to a single receiving computer. In addition, even in the case where a packet is addressed to a plurality of receiving computers, the present invention can also be applied to a case where distribution is performed to each of the receiving computers using unicast without using multicast.

The trigger of the response from the receiving computer is FEC
Is also within the scope of the present invention.

For example, the number of original blocks M = 100
00, when the number of original blocks K used for one FEC encoding is K = 10, and two redundant blocks are generated for each K, that is, there are 1000 (= M / K) FEC units, The present invention is also applicable to a case where the receiving computer returns a response after transmission of all FEC units is completed, instead of collecting responses for each FEC unit in order to increase the aggregation efficiency. .

At this time, even if the reception computer succeeds in restoring the original data by FEC decoding, if there is a reception failure block, the information of all the reception failure blocks is finally returned together, and the transmission computer returns From the number of failed blocks in each FEC unit for each receiving computer, it can be used for updating the FEC encoding parameters in the next and subsequent times.

As a method of determining the update value, the maximum value of the number of reception failure blocks in each FEC unit of all reception computers is used for the next redundancy, or the average value thereof is used. For example, a standard value in consideration of the variance of numbers can be used.

Further, the above embodiment is an example in which the receiving computer responds to any one of the “acknowledgement without loss”, the “acknowledgement with loss”, and the “negative acknowledgement”. The transmitting computer may not return the "no acknowledgment" and may regard the transmission computer as a "lossless acknowledgment" when the response times out.

[0064]

As described above, according to the present invention,
Since the acknowledgment also includes the information of the block that failed to receive, the transmitting computer can more accurately grasp the receiving status of each receiving computer and reflect the result in the redundancy at the next transmission. Efficient data distribution with appropriate redundancy according to the situation becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a conventional data distribution device.

FIG. 2 is a diagram showing an example of an operation in a conventional data distribution control method.

FIG. 3 is a configuration diagram showing an example of an embodiment of a data distribution device of the present invention.

FIG. 4 is a configuration diagram illustrating details of a data distribution device according to the present embodiment;

FIG. 5 is a diagram showing an example of an operation in the present embodiment.

FIG. 6 is a diagram illustrating an example of an operation according to the present embodiment;

FIG. 7 is a flowchart showing a processing procedure of data distribution control in the present embodiment.

[Explanation of symbols]

3: network, 10: transmission computer, 11: FEC encoding unit, 12: block transmission unit, 13: response reception unit, 14: block retransmission unit, 15: FEC encoding parameter determination unit, 20, 20-1 to 20 -3: receiving computer, 21: block receiving means, 22: FEC decoding means,
23: Response transmitting means.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // G06F 13/00 520 H04L 13/00 313 (72) Inventor Teruji Joshita 2-Chome Otemachi, Chiyoda-ku, Tokyo No. 3-1 F-term in Nippon Telegraph and Telephone Corporation (reference) 5B001 AA11 AB03 5B085 BG00 5K014 AA03 BA05 DA02 FA14 5K030 LA01 5K035 AA02 BB03 DD01 FF01 JJ05

Claims (6)

[Claims] 1. A transmission computer generates redundant data from original data by encoding for the purpose of forward error correction, and transmits both the original data and the redundant data to at least one receiving computer in block units. In a data distribution control method for retransmitting blocks necessary for restoration to a receiving computer that could not receive the minimum blocks required for restoration of original data, the reception computer failed to receive some blocks Transmitting an acknowledgment including reception failure block information such as the identifier of the block that failed in reception and the number of blocks in which reception failed, to the transmission computer, when the original data was successfully restored. . 2. The data distribution control method according to claim 1, wherein the transmission computer determines the encoding redundancy in the next and subsequent data transmissions according to the reception failure block information returned from the reception computer. A data distribution control method comprising: 3. Redundant data is generated from original data by encoding for the purpose of forward error correction, and both the original data and the redundant data are transmitted to a receiving computer in block units, and are necessary for restoring the original data. When receiving a negative acknowledgment returned from the receiving computer that could not receive the minimum number of blocks, the transmitting computer that retransmits the blocks necessary for restoration and the original data from both the original data and redundant data received in block units In a data distribution device comprising at least one receiving computer for restoring data and returning a negative acknowledgment including an identifier of a block which has failed to be received to the transmitting computer when the data cannot be restored, and a network connecting these, The computer failed to receive some blocks but restored the original data In the case of success, there is provided a response transmitting means for transmitting an acknowledgment including reception failure block information such as the identifier of the block that failed in reception and the number of blocks in which reception failed to the transmission computer. A data distribution device provided with an encoding parameter determining means for determining an encoding redundancy in the next and subsequent data transmissions in accordance with the failed reception block information. 4. Redundant data is generated from original data by encoding for the purpose of forward error correction, and both the original data and the redundant data are transmitted to a receiving computer in block units, and necessary for restoring the original data. When receiving a negative acknowledgment returned from the receiving computer that could not receive the minimum number of blocks, the transmitting computer that retransmits the blocks necessary for restoration and the original data from both the original data and redundant data received in block units A data distribution apparatus comprising at least one receiving computer for restoring data and returning a negative acknowledgment including an identifier of a block that failed to be received to the transmitting computer when the data cannot be restored, and a network connecting these computers A data distribution control program for realizing a receiving computer on a computer, comprising: If the reception of some blocks failed but the original data was successfully restored, the RAM sends an acknowledgment containing the information on the blocks that failed to receive, such as the identifier of the block that failed to receive and the number of blocks that failed to receive. A data distribution control program characterized by including a step of transmitting to a data delivery server. 5. Redundant data is generated from original data by encoding for the purpose of forward error correction, and both the original data and the redundant data are transmitted to a receiving computer in block units, and are necessary for restoring the original data. When receiving a negative acknowledgment returned from the receiving computer that could not receive the minimum number of blocks, the transmitting computer that retransmits the blocks necessary for restoration and the original data from both the original data and redundant data received in block units A data distribution apparatus comprising at least one receiving computer for restoring data and returning a negative acknowledgment including an identifier of a block that failed to be received to the transmitting computer when the data cannot be restored, and a network connecting these computers A data distribution control program for realizing a transmission computer on a computer, comprising: The ram includes a step of determining the encoding redundancy in the next and subsequent data transmissions according to the failed reception block information such as the identifier of the failed reception block returned from the reception computer and the number of failed reception blocks. A data distribution control program characterized in that: 6. A computer-readable medium on which the data distribution control program according to claim 4 is recorded.