JP2011211376A - Multicast distribution system, server device, and terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively perform multicast distribution in a multicast distribution system.SOLUTION: A server device is provided with a control data addition unit which adds control data including ratio information to distribution data which are subjected to multicast distribution and a ratio setting means which changes the ratio information so that the number of reception result notifications transmitted from terminal devices in a unit time falls in a predetermined range. The terminal device is provided with a discrimination means which compares a peculiar value of an own device or a value generated by the own device with the ratio information of the received control data and discriminates whether to perform reception result notification, and a reception result notification transmission means which transmits the reception result notification including information that reception of distribution data is possible or not to the server device when the discrimination means discriminates that the reception result notification is performed.

Description

  The present invention relates to a multicast distribution system, a server apparatus, and a terminal apparatus that perform multicast distribution of data.

  In multicast distribution, data can be efficiently distributed by transmitting the same data to a plurality of terminal devices by broadcast. However, since basic multicast distribution involves one-way communication from the server to the terminal device, even if an error occurs in the network or the like, the data cannot be retransmitted. For this reason, in order to realize reliable communication by multicast distribution, the following methods have been conventionally used.

  The first method is a method using FEC (Forward Error Correction). FEC enables transmission data to have redundancy in advance, thereby enabling a receiver to detect and correct an error, and to restore the corresponding data when a part of the data is lost.

  The second method is a data carousel system in which the same data is multicast-delivered a plurality of times at regular intervals from the server.

  As a third method, data that could not be received for each terminal device is requested from the server to be retransmitted, and the data is transmitted by unicast to the terminal device requested from the server.

  By the way, in a multicast distribution system that transmits the same data from the center device, a technology that notifies the terminal device of a ratio that limits the number of terminal devices that the center station acknowledges and the terminal device uses random numbers to determine whether or not the acknowledgment can be accepted. Is known (see, for example, Patent Document 1).

  In addition, when the server transmits data with representative identification information added to each packet from the server, the client determines whether or not it is a representative client based on the representative identification information received from the server, and receives data normally from the server. In addition, a technique in which only a representative client transmits an acknowledgment to a server is known (see, for example, Patent Document 2).

JP 2005-217743 A JP 2007-318802 A

  In the first or second method, it is necessary to set the redundancy parameter in accordance with the quality of the network. That is, in the first method, for example, the number of parity bits with respect to the number of data bits is increased as the quality of the network is worse. Further, in the second method, for example, the number of times of repeated transmission at a constant period is increased as the quality of the network is worse.

  However, when the quality of the network fluctuates, the redundancy parameter is set according to the worst case, and there is a problem that the network resources are used more than necessary and efficient multicast distribution cannot be performed. there were.

  In the third method, when an error occurs upstream (on the server side) of the network, all terminal devices connected downstream from the error become errors, and a large number of retransmission requests are transmitted to the server. In order to cope with this, both the server and the network require large resources, and there is a problem that efficient multicast distribution cannot be performed.

  The disclosed multicast distribution system aims to perform efficient multicast distribution.

A multicast distribution system according to an embodiment of the disclosure is a multicast distribution system that performs multicast distribution from a server device to a plurality of terminal devices.
The server device
Control data adding means for adding control data including ratio information to distribution data for multicast distribution;
Ratio setting means for changing the ratio information so that the number of receptions received in a unit time of the reception result notification transmitted from the terminal device is within a predetermined range;
The terminal device
A determination means for determining whether to notify a reception result by comparing a value unique to the own device or a value generated in the own device with the ratio information of the received control data;
Reception result notification transmission means for transmitting to the server device a reception result notification including information indicating whether or not the distribution data can be received when the determination means determines to perform reception result notification.

  According to this embodiment, efficient multicast distribution can be performed.

1 is a configuration diagram of an embodiment of a network system that performs multicast distribution. FIG. It is a block diagram of one Embodiment of the part which performs a multicast process with a server apparatus. It is a figure which shows the list of the setting items of a server apparatus. It is a block diagram of one Embodiment of the part which performs the multicast process of a terminal device. It is a figure for demonstrating a reception result notification flag and a reception result suppression flag. It is a figure which shows the structure of control data. It is a figure which shows the structure of a notification of a reception result. It is a figure which shows the structure of a reception result notification response. It is a flowchart of one Embodiment of the multicast process which a terminal device performs. It is a flowchart of one Embodiment of the reception result notification ratio control process which a server apparatus performs. It is a flowchart of one Embodiment of the multicast control process which a server apparatus performs.

  Embodiments will be described below with reference to the drawings.

<Configuration of base station device>
FIG. 1 shows a configuration diagram of an embodiment of a network system that performs multicast distribution. In FIG. 1, a server 1 transmits distribution data for multicast distribution to a router 2a constituting a network. For example, in a service that distributes news and movie content, video and audio data is the distribution data. Distribution data for multicast distribution is distributed from the router 2a to the terminals 3a, 3b, 3c and 3d, 3e, 3f via the routers 2b and 2c in the network.

<Configuration of server device>
FIG. 2 is a configuration diagram of an embodiment of a part that executes multicast processing in the server device. In FIG. 2, the server device 10 corresponding to the server 1 includes a multicast transmission processing unit 11, a reception state management processing unit 12, a transmission unit 13, and a reception unit 14.

  The multicast transmission processing unit 11 includes a multicast transmission control unit 21, a retransmission control unit 22, an FEC processing unit 23, and a control information management processing unit 24. The multicast transmission control unit 21 adds control data to the distribution data to be distributed by multicast, and transmits the data to the network from the transmission unit 13.

  The retransmission control unit 22 sends distribution data to be retransmitted from the transmission unit 13 to the network under the control of the reception state management processing unit 12. The FEC processing unit 23 adds FEC parity to distribution data to be distributed by multicast under the control of the reception state management processing unit 12. The control information management processing unit 24 manages information related to control data to be transmitted by being included in distribution data to be distributed by multicast, and generates a reception result notification response and transmits it from the transmission unit 13.

  The reception state management processing unit 12 includes a reception result notification reception processing unit 31, a reception result notification ratio control processing unit 32, and a state management unit 33. The reception result notification reception processing unit 31 receives a reception result notification from the data received by the reception unit 14 from the network. The reception result notification ratio control processing unit 32 variably controls the reception ratio of the reception result notification. The state management unit 33 holds and manages state information such as a reception result notification ratio in multicast.

  FIG. 3 shows a list of setting items of the server device. Regarding the reception result notification ratio, the current value (for example, 17%), the initial value (for example, 10%), the maximum value (for example, 20%), the minimum value (for example, 5%), and the increase / decrease value (for example, 1%). Is set. Among these, the current value is a variable value, and the initial value, maximum value, minimum value, and increase / decrease value are fixed values. As for the number of reception result notifications per unit time, a current reception number (for example, 925), an upper limit value (for example, 1500), and a lower limit value (for example, 500) are set. Among these, the current number of receptions is a variable value, and the upper limit value and the lower limit value are fixed values.

  An error rate threshold (for example, 10%) and a required number of samplings (for example, 300) are set for the error rate of a specific packet that is a multicast packet that is a target of reception result notification. The error rate threshold and the required number of samplings are fixed values. The error rate of this specific packet is used for multicast retransmission control.

  For the error rate for a specific period, an error rate upper limit (for example, 0.1%), an error rate lower limit (for example, 0.001%), and a required sampling number (for example, 300) are set. The error rate upper limit, the error rate lower limit, and the required number of samplings are fixed values.

  A parity number (for example, 2 packets) is set for the redundancy parameter. Here, the number of FEC parity packets added to a predetermined number (for example, 10 packets) of data packets is varied. When the data carousel method is used, the number of transmissions (for example, twice) for repeatedly transmitting the same data is set as the redundancy parameter, and the number of transmissions is varied. Furthermore, the transmission speed of distribution data for multicast distribution may be variably set as a redundancy parameter.

  By the way, the above-mentioned reception result notification ratio and the number of reception result notifications per unit time are held and managed in the state management unit 33, and the error rate of a specific packet, the error rate of a specific period, and the redundancy parameter are controlled information management processing unit 24. Is maintained. Note that all the setting items in FIG. 3 may be held and managed by the state management unit 33, for example.

<Configuration of terminal device>
FIG. 4 shows a block diagram of an embodiment of a part that executes multicast processing of a terminal device. In FIG. 4, the terminal device 40 corresponding to each of the devices 3 a to 3 f includes a reception result notification processing unit 41, a reception unit 42, and a transmission unit 43. The reception result notification processing unit 41 includes a reception result notification transmission processing unit 51 and a state management unit 52. The reception result notification transmission processing unit 51 is supplied with the multicast distribution data received by the reception unit 42 and refers to the state management unit 52 to determine whether or not to perform reception result notification. When the reception result notification is performed, the reception result notification is generated and transmitted from the transmission unit 43 to the network.

  The state management unit 52 holds a reception result notification flag, a reception result suppression flag, and the like shown in FIG. The reception result notification flag is “valid” to instruct execution of the reception result notification, and “invalid” is to instruct non-execution of the reception result notification. The reception result suppression flag indicates that reception result notification is to be suppressed with “valid”, and indicates that reception result notification is not to be suppressed with “invalid”.

<Control data>
The server device 10 adds control data to, for example, a header portion of the data and distributes it to a plurality of terminal devices by multicast. FIG. 6 shows the structure of the control data. The control data includes items of a reception result notification ratio and a reception result suppression initialization instruction. The reception result notification ratio specifies the ratio (for example, two digits) of the terminal devices that transmit the reception result notification. The reception result suppression initialization indicates whether or not the reception result suppression flag of the terminal device is initialized.

<Reception result notification>
When the terminal device 40 determines that the reception result notification is necessary, the terminal device 40 transmits a reception result notification to the server device 10. FIG. 7 shows the configuration of the reception result notification. The reception result notification includes data identification ID and reception result items. The data identification ID is an identifier for identifying data that is a target of the reception result, and for example, a packet number represented by a serial number or the like is used. The reception result sets reception success or reception failure.

<Reception result notification response>
When receiving the reception result notification from the terminal device 40, the server device 10 transmits a reception result notification response to the terminal device 40 that has transmitted the reception result notification. FIG. 8 shows the configuration of the reception result notification response. The reception result notification response includes an item of reception result suppression. Reception result suppression indicates the presence / absence of an instruction to enable the reception result suppression flag of the terminal device.

<Multicast processing of terminal device>
FIG. 9 shows a flowchart of an embodiment of multicast processing executed by the terminal device. In FIG. 9, in step S11, the reception result notification processing unit 41 initializes the reception result notification flag and the reception result suppression flag to “invalid”. Next, in step S12, the receiving unit 42 receives multicast distribution data.

  In step S13, the receiving unit 42 determines whether or not data has been received within a predetermined time. If the data cannot be received within the predetermined time, the process proceeds to step S18 because it is an error. If the data can be received within a certain time, the reception result notification transmission processing unit 51 acquires the reception result notification ratio from the control data added to the distribution data for multicast distribution in step S14. If the reception result suppression flag is invalid when data cannot be received within a predetermined time, a reception result notification indicating reception failure is transmitted to the server device in step S19.

  Next, in step S15, the reception result notification transmission processing unit 51 determines whether or not the last two digits of the terminal device ID of the own device is equal to or less than the value of the acquired reception result notification ratio, and satisfies this condition. If so, the process proceeds to step S16. If this condition is not satisfied, the process proceeds to step S17.

  In step S15, instead of the terminal device ID, the last two digits of the hash value of the terminal device ID, user ID, telephone number, and mail address of the own device may be compared with the reception result notification ratio. Further, a two-digit random number generated in the own apparatus may be compared with the reception result notification ratio. In this case, random numbers are generated when the multicast session is initialized and when the reception result suppression flag is designated by the control data transmitted by multicast. This is because the reception result suppression flag does not operate effectively if a random number is generated every time data is received.

  In step S16, the reception result notification transmission processing unit 51 sets the reception result notification flag of the state management unit 52 to “valid”, and proceeds to step S18. In step S16, the reception result notification transmission processing unit 51 sets the reception result notification flag of the state management unit 52 to “invalid” and returns to step S12.

  If the reception result notification flag is set to “valid” in step S16, the reception result notification transmission processing unit 51 determines in step S18 whether or not the reception result suppression flag of the state management unit 52 is “invalid”. If the condition is satisfied, the process proceeds to step S19. If the condition is not satisfied, the process returns to step S12. Since the reception result suppression flag is set to “invalid” in step S11 for the first time, the process proceeds to step S19.

  In step S19, the reception result notification transmission processing unit 51 generates a reception result notification and transmits it from the transmission unit 43 to the network. Next, in step S <b> 20, the receiving unit 42 receives a reception result notification response from the server device 10. In step S21, the reception result notification transmission processing unit 51 determines whether there is an instruction to validate the reception result suppression flag in the reception result notification response.

  If there is an instruction to enable the reception result suppression flag, that is, if the response does not require reception result notification, the reception result notification transmission processing unit 51 sets the reception result suppression flag of the state management unit 52 to “invalid” in step S22. Then, the process proceeds to step S12. On the other hand, if there is no instruction to enable reception result suppression, the process proceeds to step S12.

  The reception result notification is configured to be transmitted when one packet of multicast distribution data is received. However, the present invention is not limited to this, and may be configured to transmit multicast distribution data when a plurality of packets are received. Conceivable.

<Reception result notification ratio control processing of server device>
FIG. 10 shows a flowchart of an embodiment of the reception result notification ratio control process executed by the server device. In FIG. 10, in step S31, the reception state management processing unit 12 sets the initial value of the reception result notification ratio to the current value of the reception result notification ratio. In step S <b> 32, the multicast transmission control unit 21 sets the current value of the reception result notification ratio in the control data to be transmitted by being included in the multicast distribution data, and transmits from the transmission unit 13.

  In step S33, the reception result notification reception processing unit 31 receives a reception result notification from the data received by the reception unit 14 from the network. Next, in step S34, the reception result notification ratio control processing unit 32 determines whether or not the current number of reception result notifications per unit time is equal to or less than the upper limit value.

  Here, if the current reception number is equal to or less than the upper limit value, the reception result notification ratio control processing unit 32 determines whether or not the current reception number of reception result notifications per unit time is equal to or greater than the lower limit value in step S35. If the current reception number is equal to or greater than the lower limit value, the control information management processing unit 24 generates a reception result notification response without a reception result suppression instruction and transmits it from the transmission unit 13 in step S37. On the other hand, if the current reception number is less than the lower limit value, the reception result notification ratio control processing unit 32 increases the current value of the reception result notification ratio by an increase / decrease value in step S36. In step S37, the control information management processing unit 24 generates a reception result notification response without a reception result suppression instruction with the reception result suppression flag turned off, and transmits the reception result notification response from the transmission unit 13. Thereafter, the process proceeds to step S32.

  If the current reception number exceeds the upper limit value in step S34, the reception result notification ratio control processing unit 32 decreases the current value of the reception result notification ratio by an increase / decrease value in step S38. In step S39, the control information management processing unit 24 generates a reception result notification response with a reception result suppression instruction with the reception result suppression flag turned on, and transmits it from the transmission unit 13. Thereafter, the process proceeds to step S32.

  By the way, when the reception result notification ratio is significantly changed, an instruction to initialize the reception result suppression flag may be given together. In the above flowchart, the initial value of the reception result notification ratio at the start of the session is set as an initial value that is lower than the assumed ratio. On the other hand, a different initial value may be prepared in advance for each date and time of multicast distribution, or for each service performing multicast distribution, and an initial value corresponding to the date and time and service may be set.

<Multicast control processing of server device>
FIG. 11 shows a flowchart of an embodiment of multicast control processing executed by the server device. In FIG. 11, the reception result notification reception processing unit 31 receives a reception result notification from the data received by the receiving unit 14 from the network in step S51. Next, in step S52, the multicast transmission control unit 21 determines that the number of reception result notifications for the corresponding packet, that is, the multicast distribution packet, is equal to or greater than the required sampling number of the error rate of the specific packet set in the control information management processing unit 24. It is determined whether or not. If the number of reception result notifications is equal to or greater than the required sampling number, the process proceeds to step S53, and if it is less than the necessary sampling number, the process proceeds to step S55.

  In step S53, the multicast transmission control unit 21 determines the error rate [= reception failure / (reception failure + reception success) of the corresponding packet from the reception result of the reception result notification for the corresponding packet, that is, the multicast distribution packet, that is, the number of reception successes and reception failures. ] Is determined, and it is determined whether or not the error rate of the packet is equal to or higher than the error rate threshold of the error rate of the specific packet set in the control information management processing unit 24. If the error rate of the packet is equal to or higher than the error rate threshold, the process proceeds to step S54. If the error rate of the packet is less than the error rate threshold, the process proceeds to step S55.

  In step S54, the multicast transmission control unit 21 retransmits the corresponding packet by multicast, assuming that the error rate of the corresponding packet is too high. After execution of step S54, the process proceeds to step S55.

  In step S55, the multicast transmission control unit 21 determines whether or not the number of reception result notifications for multicast distribution packets in a certain period is equal to or greater than the required number of samplings for the error rate for a specific period set in the control information management processing unit 24. Determine. If the number of reception result notifications is greater than or equal to the required sampling number, the process proceeds to step S56, and if it is less than the necessary sampling number, the process proceeds to step S51.

  In step S56, the multicast transmission control unit 21 obtains an error rate for a certain period from the reception results for the multicast distribution packets in a certain period, that is, the number of reception successes and reception failures, and the error rate for the certain period is sent to the control information management processing unit 24. It is determined whether the error rate is below the upper limit of the specified specific period. If the error rate for a certain period is less than or equal to the error rate upper limit for the specific period, the process proceeds to step S57, and if the error rate for the regular period exceeds the error rate upper limit for the specific period, the process proceeds to step S58. In step S58, the multicast transmission control unit 21 increases the redundancy by increasing the number of parity of the redundancy parameter, that is, the number of FEC parity packets added to the predetermined number of data packets, for example by one, and proceeds to step S51.

  In step S57, the multicast transmission control unit 21 determines whether or not the error rate for a certain period is equal to or greater than the lower limit of the error rate for a specific period set in the control information management processing unit 24. If the error rate for a certain period is greater than or equal to the lower limit of the error rate for the specific period, the process proceeds to step S51. If the error rate for the regular period is less than the lower limit for the error rate for the specific period, the process proceeds to step S59. In step S59, the multicast transmission control unit 21 decreases the redundancy by reducing the number of parity of the redundancy parameter, that is, the number of FEC parity packets added to the predetermined number of data packets, for example by 1, and proceeds to step S51.

  In the above embodiment, the ratio of FEC data and parity is changed. However, the number of times of repeated transmission in the data carousel may be changed, and the transmission speed of distribution data to be distributed by multicast may be changed. Further, the redundancy can be changed by combining them.

  In the above embodiment, the server apparatus transmits a reception result notification ratio to the terminal apparatus as control data at the time of multicast distribution. The terminal apparatus determines whether transmission is necessary based on the reception result notification ratio, and only some terminal apparatuses Send a reception result notification to the server. The server that has received the reception result notification controls multicast distribution by changing the redundancy parameter based on the reception result notification, and controls the number of reception result notifications by changing the reception result notification ratio.

  In this way, only some of the terminal devices transmit the reception result notification to the server, so that the number of reception result notifications processed by the server device can be reduced, and a service can be provided without requiring a high-performance server. Further, by dynamically changing the reception result notification ratio, a necessary and sufficient number of samples can be collected even when the number of receiving terminal devices cannot be accurately grasped or when the number of terminal devices increases or decreases.

  Also, by dynamically changing the multicast delivery redundancy parameter based on the reception status of the terminal device, network resources can be used effectively and efficient multicast delivery can be performed.

  In addition, when the number of terminal devices that receive multicast is unknown, the initial value of the reception result notification ratio is set to a smaller value than expected, and by gradually increasing the ratio while looking at the actual number of reception result notifications, When the number of terminal devices cannot be grasped, it is possible to avoid the server that processes the reception result notification from being overloaded when the number of terminal devices is larger than expected.

  Incidentally, in step S31 of FIG. 10, the initial value of the reception result notification ratio is set to the current value of the reception result notification ratio. However, the initial value of the reception result notification ratio is set according to the type of service, the time zone, and the like. It may be changed.

  For example, news content in the morning hours of weekdays has a large number of distribution destination users, so the initial value of the reception result notification ratio is set to a small value (several percent), and received in the afternoon hours because the number of distribution destination users is small. The initial value of the result notification ratio is set to a medium value (10%). In addition, since the content of movies in the night time zone has a large number of distribution destination users, the initial value of the reception result notification ratio is set to a small value (several percent). As a result, the reception result notification ratio can be converged to the optimum number of reception result notifications in a short time.

In the above embodiment, the multicast transmission control unit 21 is used as an example of a control data adding unit, a redundancy varying unit, and a retransmission unit, and the reception result notification ratio control processing unit 32 is used as an example of a ratio setting unit. The reception result notification transmission processing unit 51 is used as an example of a determination unit and a reception result notification transmission unit, and the control information management processing unit 24 is used as an example of a response unit.
(Appendix 1)
In a multicast distribution system that performs multicast distribution from a server device to a plurality of terminal devices,
The server device
Control data adding means for adding control data including ratio information to distribution data for multicast distribution;
Ratio setting means for setting and changing the ratio information so that the number of receptions received in unit time of the reception result notification transmitted from the terminal device is within a predetermined range;
The terminal device
A determination means for determining whether to notify a reception result by comparing a value unique to the own device or a value generated in the own device with the ratio information of the received control data;
A multicast distribution system comprising: a reception result notification transmission unit configured to transmit a reception result notification including information about whether or not the distribution data can be received to the server device when the determination unit determines to perform the reception result notification. .
(Appendix 2)
In the multicast distribution system according to appendix 1,
The server device
When the error rate of the distribution data obtained from the reception availability information of the received reception result notification exceeds a predetermined upper limit, the redundancy of the distribution data is increased, and the error rate of the distribution data is a predetermined lower limit A multicast distribution system comprising redundancy varying means for reducing the redundancy of the distribution data when the value is less than the value.
(Appendix 3)
In the multicast distribution system described in appendix 2,
The ratio setting means reduces the ratio information when the reception number exceeds the upper limit of the predetermined range, and increases the ratio information when the reception number is less than the lower limit of the predetermined range. Multicast distribution system.
(Appendix 4)
In the multicast distribution system according to appendix 3,
The server device
A multicast distribution system comprising: response means for performing a reception result notification response instructing suppression of transmission of the reception result notification when the number of receptions exceeds an upper limit of the predetermined range.
(Appendix 5)
In the multicast distribution system according to appendix 4,
The server device
A multicast distribution system comprising: a retransmission unit configured to retransmit the distribution data when an error rate of the distribution data is equal to or greater than a predetermined threshold.
(Appendix 6)
In a server device of a multicast distribution system that performs multicast distribution to a plurality of terminal devices,
Control data adding means for adding control data including ratio information to distribution data for multicast distribution;
Ratio setting means for setting and changing the ratio information so that the number of receptions received in unit time of the reception result notification transmitted from the terminal device is within a predetermined range;
The server apparatus characterized by having.
(Appendix 7)
In a terminal device of a multicast distribution system for receiving distribution data to which control data including ratio information distributed by multicast from a server device is added,
A determination means for determining whether to notify a reception result by comparing a value unique to the own device or a value generated in the own device with the ratio information of the received control data;
A reception result notification transmitting means for transmitting a reception result notification including information on whether or not the distribution data can be received to the server device when it is determined that the determination means performs the reception result notification;
The terminal device characterized by having.
(Appendix 8)
In the server device according to attachment 6,
When the error rate of the distribution data obtained from the reception availability information of the received reception result notification exceeds a predetermined upper limit, the redundancy of the distribution data is increased, and the error rate of the distribution data is a predetermined lower limit A server apparatus comprising a redundancy variable means for reducing the redundancy of the distribution data when the value is less than the value.
(Appendix 9)
In the server device according to attachment 8,
The ratio setting means reduces the ratio information when the reception number exceeds the upper limit of the predetermined range, and increases the ratio information when the reception number is less than the lower limit of the predetermined range. Server device.
(Appendix 10)
In the server device according to attachment 9,
A server apparatus comprising: a response unit configured to perform a reception result notification response instructing suppression of transmission of a reception result notification when the number of receptions exceeds an upper limit of the predetermined range.
(Appendix 11)
In the server device according to attachment 10,
A server apparatus comprising: a retransmission unit configured to retransmit the distribution data when an error rate of the distribution data is equal to or greater than a predetermined threshold.
(Appendix 12)
In the multicast distribution system according to any one of appendices 1 to 5,
The said ratio setting means sets the initial value of ratio information according to a time slot | zone or service, The multicast delivery system characterized by the above-mentioned.
(Appendix 13)
The server device according to any one of appendix 6 or 8 to 11,
The said ratio setting means sets the initial value of ratio information according to a time slot | zone or service, The server apparatus characterized by the above-mentioned.

DESCRIPTION OF SYMBOLS 1 Server 2a, 2b, 2c Router 3a-3f Terminal 10 Server apparatus 11 Multicast transmission process part 12 Reception state management process part 13 Transmission part 14 Receiving part 21 Multicast transmission control part 22 Retransmission control part 23 FEC process part 24 Control information management process Unit 31 reception result notification reception processing unit 32 reception result notification ratio control processing unit 33 state management unit 40 terminal device 41 reception result notification processing unit 42 reception unit 43 transmission unit 51 reception result notification transmission processing unit 52 state management unit

Claims (7)

In a multicast distribution system that performs multicast distribution from a server device to a plurality of terminal devices,
The server device
Control data adding means for adding control data including ratio information to distribution data for multicast distribution;
Ratio setting means for changing the ratio information so that the number of receptions received in a unit time of the reception result notification transmitted from the terminal device is within a predetermined range;
The terminal device
A determination means for determining whether to notify a reception result by comparing a value unique to the own device or a value generated in the own device with the ratio information of the received control data;
A multicast distribution system comprising: a reception result notification transmission unit configured to transmit a reception result notification including information about whether or not the distribution data can be received to the server device when the determination unit determines to perform the reception result notification. . The multicast distribution system according to claim 1,
The server device
When the error rate of the distribution data obtained from the reception availability information of the received reception result notification exceeds a predetermined upper limit, the redundancy of the distribution data is increased, and the error rate of the distribution data is a predetermined lower limit A multicast distribution system comprising redundancy varying means for reducing the redundancy of the distribution data when the value is less than the value. The multicast distribution system according to claim 2, wherein
The ratio setting means reduces the ratio information when the reception number exceeds the upper limit of the predetermined range, and increases the ratio information when the reception number is less than the lower limit of the predetermined range. Multicast distribution system. The multicast distribution system according to claim 3, wherein
The server device
A multicast distribution system comprising: response means for performing a reception result notification response instructing suppression of transmission of the reception result notification when the number of receptions exceeds an upper limit of the predetermined range. The multicast distribution system according to claim 4, wherein
The server device
A multicast distribution system comprising: a retransmission unit configured to retransmit the distribution data when an error rate of the distribution data is equal to or greater than a predetermined threshold. In a server device of a multicast distribution system that performs multicast distribution to a plurality of terminal devices,
Control data adding means for adding control data including ratio information to distribution data for multicast distribution;
Ratio setting means for changing the ratio information so that the number of receptions received in unit time of the reception result notification transmitted from the terminal device falls within a predetermined range;
The server apparatus characterized by having. In a terminal device of a multicast distribution system for receiving distribution data to which control data including ratio information distributed by multicast from a server device is added,
A determination means for determining whether to notify a reception result by comparing a value unique to the own device or a value generated in the own device with the ratio information of the received control data;
A reception result notification transmitting means for transmitting a reception result notification including information on whether or not the distribution data can be received to the server device when it is determined that the determination means performs the reception result notification;
The terminal device characterized by having.

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