JP6539218B2 - Data transfer system - Google Patents

Description

  The present invention relates to a data transfer system, a relay node apparatus, and a data transfer method for distributing a stream such as video from a distribution server to one or more receiving apparatuses.

  Recently, large-capacity content such as 4K video and 8K video has been sent to the back of the earth in real time using an IP network such as the Internet, and it is considered that worldwide video stream distribution will become more popular in the future. . However, in IP networks such as the Internet, packet loss occurs due to occasional congestion. Although it is affected by the conditions of the network used, generally, the larger the content and the longer the distance, the more the number of packet losses tends to be.

  Conventionally, several methods have been used as a countermeasure against such a situation. One of them is a method using End-to-end FEC (Forward Error Correction) (see Non-Patent Document 1). However, this method often assumes the worst loss rate measured in advance, and as described above, the larger the content to be transmitted and the longer the distance, the higher the number of packet losses tends to be. Therefore, the number of packets carrying parity bits of FEC (hereinafter referred to as parity packets) increases, and a large amount of parity packets also flow in unnecessary time zones and places in the network. This not only degrades the utilization efficiency of the network, but also causes additional packet loss caused by a large number of parity packets.

  Another method is retransmission using End-to-end TCP (Transmission Control Protocol), which is conventionally used and which retransmits a lost packet from a sending server to a receiving device. However, in this method, the lost packet is retransmitted after the retransmission request reaches the transmission server from the receiving device. As described above, when world wide video stream distribution is performed, it becomes long distance transmission such as tens of thousands of kilometers. Therefore, the propagation delay time is increased, and retransmission may be performed many times, which makes real-time content reproduction difficult.

  Therefore, instead of retransmission by the end-to-end TCP protocol, one or more relay nodes are provided in the network, and between the transmission server and the relay node, between the relay node and the relay node, and between the relay node and the receiver. There is a conceivable method of performing retransmission by the TCP protocol.

  In this method, generally, as the number of relay nodes increases, the number of lost packets in the relay section tends to decrease, and retransmission is not performed in a section where there is no loss, so the delay time due to retransmission can be reduced. There is also. However, this method has a problem that a large amount of content must be held for a fixed time in all relay nodes in order to perform retransmission by the TCP protocol. That is, there is a problem that the total amount of memory for holding content increases as the number of relay nodes increases.

JP, 2011-199647, A

Hideki Imai, Electronics Essentials Series "Points of error correction coding technology", Japan Industrial Technology Center, Chapter 3 Application to Communication, 1.1 FEC and ARQ ~ 1.2 Application to Communication System, pp. 49-51 (1986).

  Therefore, it is considered that content is managed in units of FEC blocks and stream transfer is performed, and each relay node holds only a parity packet (parity datagram GP) that can be restored up to a preset loss for a necessary time. In this case, the transmission side relay node is transmitted to request transmission of the parity packet corresponding to the retransmission of the lost packet. When the relay node on the receiving side receives the parity packet sent from the relay node on the transmitting side, it uses the parity packet to recover a lost packet.

  Hereinafter, in the transmission path from the distribution server to the receiving apparatus, a section between the distribution server and the relay node, a section between the relay node and the relay node, and a section between the relay node and the receiving apparatus will be referred to as a relay node section. Also, datagrams referred to below include packets of various communication protocols including IP packets, Ethernet (registered trademark) frames, ATM (Asynchronous Transfer Mode) cells, X.S. It refers to a group of bit strings for transferring some information such as 25 packets.

  FIG. 2 shows an outline of a data delivery method related to the present invention. In the data delivery method related to the present invention, when the content datagram GC is lost in a relay node section on the transmission path, the relay node on the reception side of the relay node section detects the loss and sends it to the relay node on the transmission side. If a "data datagram for parity datagram (GP) transmission request" is transmitted but the required parity datagram GP is not held in the receiving relay node, the necessary parity data from the relay node further upstream thereof It is necessary to have Grams GP sent as soon as possible. In the following, “parity datagram transmission request” is referred to as “GP transmission request”.

  Therefore, when "GP transmission request" datagrams are transferred toward the upstream relay node one after another, the content datagram GC of the FEC block in which the loss has occurred is transmitted upstream from the relay node through which the content datagram GC has passed. A Request to Send "datagram will be transferred. Then, the distribution server 2 receives the “GP transmission request” many times. That is, a large number of "GP transmission request" datagrams will be forwarded upstream even with a single loss.

  An object of the present invention is to deliver a stream without flowing unnecessary parity datagrams and unnecessary "parity datagram transmission requests" into the network.

  In the present invention, the downstream node is notified that the transmission request for the parity datagram has already been sent to the upstream node. Then, when the notification is not received, the “parity datagram transmission request” is transmitted to the upstream node.

The data transfer system according to the present invention is
A data transfer system for transferring content datagrams using a plurality of relay nodes, comprising:
The relay node on the receiving side of the relay section in which the content datagram loss has occurred sends the datagram of “parity datagram transmission request” including the identification number of the FEC block of the content datagram having the loss to the upstream relay node Before transmitting toward the destination, the "parity datagram transmission request transmitted" datagram indicating that the "parity datagram transmission request" datagram is transmitted toward the upstream relay node is immediately directed to the downstream relay node. Send
Relay node receiving the datagram from an upstream relay node "parity datagram transmission request Sent", together with the immediately transfers the datagram to the downstream relay node, toward upstream of the relay node "parity datagram transmission Suppress the transmission of "request" datagrams,
It is characterized by

In the data transfer system according to the present invention,
If the receiving relay node detects a loss of content datagrams:
Immediately transmit a “parity datagram transmission request transmitted” datagram to the downstream relay node,
The "parity datagram transmission request has been sent" datagram from the upstream relay node within the first waiting time set in advance after receiving the first datagram in the FEC block of the content datagram in which the loss occurred If not received, the first waiting time is T, and a predetermined second waiting time for fluctuations in the arrival time of the content datagram alpha, "parity datagram after the elapse of the waiting time (T + alpha) The "request for transmission" datagram may be transmitted toward the upstream relay node.

The data transfer method according to the present invention is
A data transfer method in which a plurality of relay nodes transfer content datagrams, wherein
The relay node on the receiving side of the relay section in which the content datagram loss has occurred sends the datagram of “parity datagram transmission request” including the identification number of the FEC block of the content datagram having the loss to the upstream relay node Before transmitting toward the destination, the "parity datagram transmission request transmitted" datagram indicating that the "parity datagram transmission request" datagram is transmitted toward the upstream relay node is immediately directed to the downstream relay node. Send
Relay node receiving the datagram from an upstream relay node "parity datagram transmission request Sent", together with the immediately transfers the datagram to the downstream relay node, toward upstream of the relay node "parity datagram transmission Suppress the transmission of "request" datagrams,
It is characterized by

In the data transfer method according to the present invention,
If the receiving relay node detects a loss of content datagrams:
Immediately transmit a “parity datagram transmission request transmitted” datagram to the downstream relay node,
The "parity datagram transmission request has been sent" datagram from the upstream relay node within the first waiting time set in advance after receiving the first datagram in the FEC block of the content datagram in which the loss occurred If not received, the first waiting time is T, and a predetermined second waiting time for fluctuations in the arrival time of the content datagram alpha, "parity datagram after the elapse of the waiting time (T + alpha) The "request for transmission" datagram may be transmitted toward the upstream relay node.

Relay nodes according to the present invention,
A the relay nodes included in the data transfer system for transferring content datagrams using a plurality of relay nodes,
A first function of detecting loss of content datagrams;
The datagram of the “parity datagram transmission request” is sent before the “parity datagram transmission request” datagram including the identification number of the FEC block of the content datagram in which the loss occurred is transmitted to the upstream relay node. A second function of immediately transmitting to the downstream relay node a “parity datagram transmission request transmitted” datagram of transmitting to the upstream relay node;
When a “parity datagram transmission request transmitted” datagram is received from the upstream relay node , the datagram is immediately transferred to the downstream relay node and the “parity datagram transmission request” directed to the upstream relay node A third function to suppress the transmission of datagrams;
And the like.

The relay node according to the present invention,
If the first feature detects a loss of content datagrams:
The second function is immediately transmitted toward datagrams "parity datagram transmission request Sent" downstream relay node,
The third function is data of “parity datagram transmission request transmitted” within a first waiting time set in advance after reception of the leading datagram of the FEC block of the content datagram in which the loss has occurred. If not receiving the grams upstream relay node, wherein the first waiting time is T, the predetermined second waiting time for fluctuations in the arrival time of the content datagrams with alpha, waiting time (T + alpha) The “parity datagram transmission request” datagram may be transmitted to the upstream relay node after the elapse of.

The apparatus of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network. Program according to the present invention is a program for realizing the functions relay node according to the present invention is provided to the computer.

  According to the present invention, stream distribution can be performed without flowing unnecessary parity datagrams and unnecessary "parity datagram transmission requests" into the network. Therefore, in the data delivery method related to the present invention, although a large number of “GP transmission request” datagrams are transmitted from the downstream relay node toward the upstream relay node, they can be suppressed by the present invention .

FIG. 1 is a schematic explanatory view of a network implementing the present invention. It is a schematic explanatory drawing of the data delivery method relevant to this invention. 5 is an example of content data according to an embodiment of the present invention. It is an example of the content datagram which concerns on embodiment of this invention. It is an example of the parity datagram which concerns on embodiment of this invention. It is an outline explanatory view of the data distribution method concerning the embodiment of the present invention. It is an example of a functional block configuration of a relay node according to an embodiment of the present invention. It is an example of operation | movement of the relay node which concerns on embodiment of this invention. It is an example of operation | movement of the receiver which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below. These implementation examples are merely illustrative, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, components having the same reference numerals denote the same components.

First Embodiment
FIG. 1 is an example of a network 0 in which a relay node 1 incorporating the functions of the present invention is used. The distribution server 2, the receiving device 3, and the operation device 4 are connected to the network 0. In the network 0, one or more relay nodes 1 are disposed as devices having a datagram transfer function. Hereinafter, exchange of various datagrams performed between the distribution server 2, the relay node 1 and the receiving device 3 in FIG. 1 will be described.

  FIG. 2 is a schematic explanatory view of a data delivery method related to the present embodiment. First, the distribution server 2 constructs a payload portion and adds a header such as a destination to create a datagram. To that end, the distribution server 2 divides the content data CD to be distributed, as shown in FIG. Do. If it is insufficient at the end, perform padding etc. The distribution server 2 further divides the content bit string CF according to the bit length in the payload of the datagram to create a divided bit string CB.

  Then, as shown in FIG. 4, the distribution server 2 indicates, in each divided bit string CB, at least “FEC block number” indicating which FEC block belongs to, and which position within the FEC block “ The FEC block internal number is assigned. The destination of the datagram is the unicast distribution, that is, the address of the receiving apparatus 3 when the distribution server 2 performs one-to-one distribution to one receiving apparatus 3, and the multicast distribution, ie, the distribution server 2 In the case where one-to-many distribution is performed to a plurality of receiving apparatuses 3, the multicast address or the like is used. Hereinafter, the datagram will be referred to as "content datagram GC".

  The distribution server 2 further creates, as an upstream node function, a preset number of FEC parity bit strings PB for the content bit strings CF for each FEC block. Then, as shown in FIG. 5, a datagram is similarly created. That is, each parity bit string PB is assigned at least an "FEC block number" indicating which FEC block is the parity bit string, and a "parity bit string number" indicating which parity bit string is generated. The destination of the datagram is the unicast distribution, that is, the address of the receiving apparatus 3 when the distribution server 2 performs one-to-one distribution to one receiving apparatus 3, and the multicast distribution, ie, the distribution server 2 In the case where one-to-many distribution is performed to a plurality of receiving apparatuses 3, the multicast address or the like is used. Hereinafter, the datagram will be referred to as "parity datagram GP". Up to this point is the same as the operation of the conventional FEC type distribution server.

  In FIG. 2, when a loss of a datagram occurs in the section between the distribution server 2 and the relay node 1a and there is a content datagram that can not be received by the relay node 1a, each relay node 1 determines that the content data at the head of the FEC block After the waiting time (T + α) from the reception of the gram GC, it is detected as the loss of the content datagram GC of the FEC block. α is a time set in advance in consideration of fluctuation of arrival time such as order inversion in a router on the transmission path or L3 switch. Incidentally, T will be described later.

  If there is a content datagram that can not be received, the relay node 1 immediately transmits the “GP transmission request” datagram including at least the identification number of the FEC block, and if there is an upstream relay node 1, the relay node 1 is upstream. Toward the relay node 1, if there is no upstream relay node 1, it transmits toward the upstream distribution server 2. In FIG. 2, since there is no relay node 1 upstream of the relay node 1a, the relay node 1a transmits a “GP transmission request” datagram to the distribution server 2.

  The upstream relay node 1 that has received the “GP transmission request” datagram can restore the content at the receiving device 3 as much as possible if it does not hold the parity datagram GP corresponding to the lost content datagram GC. In order to be able to do it quickly, "GP transmission request" is immediately transferred to the relay node 1 or distribution server 2 further upstream.

  Also, the content datagram GC received by the relay node 1a is immediately transferred to the downstream relay node 1 or the receiving device 3 in order to enable the content restoration in the receiving device 3 to be performed as soon as possible. Ru.

  Since it operates as described above, “GP transmission request” is output upstream from the reception side relay node 1 of the relay node section where the loss of datagram has occurred and the subsequent relay nodes 1 and receivers 3, Even with the loss of only one datagram, many "GP transmission requests" will flow through the network.

  If the upstream relay node 1 or the distribution server 2 holds the parity datagram GP corresponding to the lost content datagram GC, it immediately outputs it to the downstream relay node 1. The relay node 1 receiving this transfers it further downstream to the relay node 1.

  FIG. 6 is a schematic explanatory view of the delivery method according to the embodiment of the present invention. In FIG. 6, when a loss of a datagram occurs in the section between the delivery server 2 and the relay node 1a, each relay node 1 receives a content datagram GC at the head of the FEC block after the waiting time T has elapsed. Detect as a loss of content datagram GC of FEC block. This waiting time T is an assumed time from the reception of the content datagram GC at the head of the FEC block to the reception of the last content datagram GC on the transmission path, and is set in advance.

  The relay node 1 that has detected the loss of the content datagram GC immediately transmits the “GP transmission request transmitted” datagram toward the downstream relay node. The name is such that it is transmitted after the “GP transmission request” datagram, but in the interest of clarity, such a name is used here.

  Furthermore, the relay node 1 transmits a “GP transmission request” datagram to the upstream relay node or distribution server after waiting time (T + α) seconds after receiving the content datagram GC at the head of the FEC block. Here, α is a predetermined time which is a predetermined time, and is a margin for fluctuation of arrival time such as order inversion in a router or L3 switch on the transmission path. In FIG. 6, since there is no relay node upstream of the relay node 1a, transmission is performed toward the distribution server 2.

  However, when the relay node 1 receives the “GP transmission request transmitted” datagram before waiting time (T + α) seconds after receiving the content datagram GC at the head of the FEC block, the data of “GP transmission request” Do not send the gram upstream.

  Since it operates as described above, even if the receiving side relay node 1 of the relay node section where the loss of datagram has occurred and the relay node 1 and the receiver 3 after that detect the loss of datagram, those relay nodes The 'GP transmission request' is no longer output upstream from 1 and it is possible to prevent many 'GP transmission requests' from flowing in the network.

  If the upstream relay node 1 or the distribution server 2 holds the parity datagram GP corresponding to the lost content datagram GC, it immediately outputs it to the downstream relay node 1. The relay node 1 receiving this transfers it further downstream to the relay node 1.

The above method can be implemented in software on a computer.
In addition, an electronic circuit that performs the above-described operation can be mounted on hardware. The hardware is an electronic circuit in which logic elements are combined, and may be realized by mounting a logic IC or the like on a substrate, or may be realized by FPGA, PAL, etc. or realized in a custom LSI You may

Second Embodiment
In this embodiment, the functional block configuration and operation of the relay node will be described.
FIG. 7 is an example of a functional block configuration of the relay node according to the present embodiment. The relay node 1 includes input interface units 10a to 10n, a processing unit 30, a control unit 40, a switch unit 20, output interface units 11a to 11n, and a control unit input / output interface unit 50. The processing unit 30 includes, for example, a programmable processing circuit such as a central processing unit (CPU) or a field programmable gate array (FPGA) or a programmable logic device (PLD) and a memory. The control unit 40 is configured of, for example, a CPU (Central Processing Unit) and the like and a memory.

  In FIG. 7, between the relay node 1A and the relay node 1B, the relay node 1A functions as an upstream node and the relay node 1B functions as a downstream node, but the relay node 1 functions as both a downstream node and an upstream node. Since both the upstream node function and the downstream node function are provided. The processing unit 30 also includes a part of the upstream node function and a part of the downstream node function.

  FIG. 8 shows a flowchart of the operation of the relay node 1. Hereinafter, along with FIG. 6, an example of the operation of the relay node 1 will be shown. When the relay node 1 receives the content datagram GC sent from the relay node 1 or the distribution server 2 further upstream as the upstream node function, the relay node 1 copies and holds the content datagram GC, and also the distribution delay time. In order to make it as small as possible, the destination in the header of the content datagram GC is immediately read, and it is immediately forwarded to one or more destinations (S101).

  In FIG. 6, when the relay node 1a closest to the distribution server 2 receives the content datagram GC transmitted from the distribution server 2, the relay node 1a copies and holds the content datagram GC, and makes the distribution delay time as short as possible. Then, the destination in the header of the content datagram GC is immediately read, and it is immediately transferred to the relay node 1b further downstream (S101). At this time, the copied content datagram GC is held for a preset time.

  The relay node 1a further determines, as the downstream node function, the network path between the distribution server 2 and the relay node 1a in each FEC block from the FEC block number written in the content datagram GC and the in-FEC block number. It is checked whether there is a content datagram GC that could not be received due to a loss or the like (S102).

  In FIG. 6, the relay node 1a which has received all the content datagrams GC of the corresponding FEC block by the time set in advance extracts the divided bit string CB from the respective content datagrams GC (S103) and uses the original FEC The content bit string CF of the block is reconstructed (S104), and a predetermined number of parity bit strings PB are created from the content bit strings CF, and a parity datagram GP is created from them (S105). The content bit string CF and the content datagram GC are immediately erased (S106). Also, the parity datagram GP is held for a predetermined time, and when the holding time has elapsed (Yes in S109), the corresponding parity datagram GP is erased (S110). The operation of the relay node 1 in the case where all content datagrams GC of the corresponding FEC block can not be received by the time set in advance will be described in the following description of the relay node 1b.

  When the relay node 1b closest to the relay node 1a receives the content datagram GC transmitted from the relay node 1a, the relay node 1b copies and holds the received content datagram GC, and makes the delivery delay time as short as possible. The destination in the header of the content datagram GC is immediately read, and it is immediately transferred to the next transfer destination receiver 3 in FIG. 6 (S101).

  The relay node 1b further performs the following operation as a downstream node function. That is, content datagrams that could not be received due to a loss or the like on the network path between the relay node 1a and the relay node 1b in each FEC block from the FEC block number and the in-FEC block number written in the datagram It is checked whether there is a GC (S102).

  In FIG. 6, the relay node 1b which can not receive part or all of the content datagram GC of the corresponding FEC block by the time set in advance (Yes in S102) executes the procedure of receiving the parity datagram. Do. That is, the relay node 1b immediately transmits the "GP transmission request transmitted" datagram to the downstream relay node (S211), waits for the elapse of the waiting time (S212), and transmits the "GP transmission during the waiting time" If the datagram of "request transmitted" is not received (S213), the datagram of "parity datagram transmission request" is transmitted to the relay node 1a (S201). In this datagram, at least the FEC block number and the number of datagrams that could not be received are entered.

  For example, when there is a loss in the content datagram GC # 2 received by the relay node 1b (Yes in S102), the relay node 1b requests transmission of a parity datagram GP for restoring the content datagram GC # 2. It sends a "parity datagram transmission request" to the effect to the relay node 1a (S201).

  The relay node 1a that has received the datagram of "parity datagram transmission request" (S107) immediately transmits the required number of parity datagrams GP of the corresponding FEC block as an upstream node function (S108).

  The "required number" said here is the following. In the method using FEC, if there is a number of parity datagrams GP corresponding to the number of content datagrams lost in one FEC block, they are used to restore the lost content bit string CF in the FEC block, The content bit string CF of the FEC block can be configured. The number of parity datagrams GP corresponding to the number of lost content datagrams GC is, for example, the same as the number of lost content datagrams GC in the case of a Reed-Solomon code, and the low density generator matrix (LDGM). In the case of codes, for example, it is approximately 10% to the loss of 7% of content datagram GC, and the number according to the codes used for FEC is set in advance in distribution server 2 and each relay node 1 .

  Furthermore, the relay node 1b transmits the datagram of “parity datagram transmission request” for the same FEC block is not limited to one transmission, and parity on the network path between the relay node 1a and the relay node 1b. Due to the loss of datagrams, it is possible to transmit datagrams of "parity datagram transmission request" again. In such a case, even if the same relay packet as the parity datagram GP that relay node 1b can receive is transmitted from relay node 1a, it does not help recovering the lost bit string in the FEC block. In the "transmission request" datagram, the number of the parity datagram GP already received is also described. The relay node 1a transmits the missing number of parity datagrams GP to the relay node 1b while avoiding the already received parity datagram GP.

  It should be noted that, on the network route between the relay node 1a and the relay node 1b, instead of describing the number of the parity datagram GP already received by the relay node 1b in the datagram of “parity datagram transmission request”. There is a possibility that the parity datagram GP may be lost at the end, but the relay node 1a on the transmitting side records the number of the transmitted parity datagram GP of the corresponding FEC block, and selects not to overlap. There is also a way to send.

  The relay node 1 receiving the parity datagram GP copies and holds the received parity datagram GP as an upstream node function, and immediately reduces the distribution datagram time to reduce the distribution datagram time, The content datagram GC is transferred to one or more destinations to which it has been sent earlier (S202).

  In FIG. 6, the relay node 1b receiving the parity datagram GP copies and holds the received parity datagram GP as an upstream node function, and immediately reduces the parity data to reduce the delivery delay time. The program GP is transferred to the receiver 3 which has transmitted the content datagram GC earlier (S202).

  The relay node 1b further has, as a downstream node function, a network type between the relay node 1a and the relay node 1b from the datagram type and the FEC block number that are the parity datagram GP written in the datagram. It is checked whether there is a parity datagram GP that could not be received due to a loss or the like (S203).

  The relay node 1b which has received the required number of parity datagrams GP for calculating the parity of the corresponding FEC block by the preset time (Yes in S203) relays the parity bit string PB from the received parity datagram GP. Fetch (S204), fetch the divided bit string CB from the plurality of content datagrams GC already held in the corresponding FEC block (S205), restore the lost divided bit string CB from the divided bit string CB and the parity bit string PB ( S206) The content bit string CF of the FEC block is reconstructed (S104).

  Further, a parity bit string PB of a preset number is created from the content bit string CF of the reconstructed FEC block, and a parity datagram GP as shown in FIG. 5 is created (S105).

  The parity bit string PB of the payload having the same FEC block number and parity bit string number is the same, with the method of creating the parity bit string PB from the content bit string CF of the FEC block the same for the distribution server 2 and all relay nodes 1 Make the values identical. Thus, when the relay node 1 creates a predetermined number of parity bit strings PB from the content bit strings CF of the reconstructed FEC block, the relay node 1 transmits the parity bit strings PB in the parity datagram GP already received. , The parity bit string PB can be diverted without making it. For this reason, if the number of received parity datagrams GP is equal to or greater than a preset number of parity bit strings PB created from the content bit strings CF of the reconstructed FEC block, the parity bit strings You can do without creating a PB at all.

  After creating or diverting the parity datagram GP of the corresponding FEC block, the unnecessary content bit string CF and the content datagram GC are erased (S106). When the parity datagram GP created or diverted receives the “parity datagram transmission request” sent from the downstream relay node 1 or the receiving device 3 (Yes in S107), the required number of downstream relay nodes 1 or It is transmitted toward the receiver 3 (S108).

  Also, the parity datagram GP created or diverted is erased (Yes in S109) when a predetermined retention time has elapsed (S110). All relay nodes 1 have the upstream node function and the downstream node function described above, and perform the same operation as described above. Also, the distribution server 2 has an upstream node function.

  FIG. 9 shows an operation algorithm of the receiving device 3. The receiving device 3 has the downstream node function described above. In FIG. 6, when the content datagram GC is received from the network 0 (S301), the receiving device 3 performs the same operation as the downstream node function of the relay node 1, that is, whether there is any content datagram GC which could not be received. Is checked (S302), and if there is no content datagram GC that can not be received (No in S302), the divided bit string CB is extracted from each content datagram GC and held (S303).

  If there is a content datagram GC that can not be received (Yes in S302), the receiving device 3 waits for the elapse of the waiting time (S412), and during the waiting time, the "GP transmission request has been sent" datagram Is not received (S413), a "parity datagram transmission request" is transmitted to the upstream nearest relay node 1b (S401). As a result, the parity datagram GP is sent from the nearest upstream relay node 1b. The receiving device 3 having received the parity datagram GP checks whether the number of parity datagrams GP necessary for recovering the lost content datagram GC has been received (S402). When the required number of parity datagrams GP can not be received (No in S402), a “parity datagram transmission request” is transmitted again to the upstream nearest relay node 1b (S401). This operation is repeated until the number of parity datagrams GP required for recovering the lost content datagram GC or the number requested by the receiver has been received.

  When the required number of parity datagrams GP are received (Yes in S402), the receiving device 3 takes out the parity bit string PB from the parity datagrams GP (S403), takes out the divided bit strings CB from the content datagrams GC (S404) Parity calculation is performed using the one or more parity bit strings PB and divided bit strings CB thus taken out, and the lost divided bit strings CB are restored (S 405).

  Next, the content bit string CF of the FEC block is reconstructed from the restored one or more divided bit strings CB and the one or more divided bit strings CB already held in the receiving device 3 (S304), Further, the content data CD is reconstructed from the content bit string CF of all the FEC blocks (S305), and the content is reproduced (S306).

  The present invention can be applied to the information communication industry.

0: Network 1: Relay node 2: Distribution server 3: Reception device 4: Operation device 10: Input interface unit 11: Output interface unit 20: Switch unit 30: Processing unit 40: Control unit 50: Control unit input / output interface unit 100 :Detector

Claims (7)

A data transfer system for transferring content datagrams using a plurality of relay nodes, comprising:
The relay node on the receiving side of the relay section in which the content datagram loss has occurred sends the datagram of “parity datagram transmission request” including the identification number of the FEC block of the content datagram having the loss to the upstream relay node Before transmitting toward the destination, the "parity datagram transmission request transmitted" datagram indicating that the "parity datagram transmission request" datagram is transmitted toward the upstream relay node is immediately directed to the downstream relay node. Send
Relay node receiving the datagram from an upstream relay node "parity datagram transmission request Sent", together with the immediately transfers the datagram to the downstream relay node, toward upstream of the relay node "parity datagram transmission Suppress the transmission of "request" datagrams,
A data transfer system characterized by If the receiving relay node detects a loss of content datagrams:
Immediately transmit a “parity datagram transmission request transmitted” datagram to the downstream relay node,
The "parity datagram transmission request has been sent" datagram from the upstream relay node within the first waiting time set in advance after receiving the first datagram in the FEC block of the content datagram in which the loss occurred If not received, the first waiting time is T, and a predetermined second waiting time for fluctuations in the arrival time of the content datagram alpha, "parity datagram after the elapse of the waiting time (T + alpha) Send the "request for transmission" datagram towards the upstream relay node,
The data transfer system according to claim 1, characterized in that: A data transfer method in which a plurality of relay nodes transfer content datagrams, wherein
The relay node on the receiving side of the relay section in which the content datagram loss has occurred sends the datagram of “parity datagram transmission request” including the identification number of the FEC block of the content datagram having the loss to the upstream relay node Before transmitting toward the destination, the "parity datagram transmission request transmitted" datagram indicating that the "parity datagram transmission request" datagram is transmitted toward the upstream relay node is immediately directed to the downstream relay node. Send
Relay node receiving the datagram from an upstream relay node "parity datagram transmission request Sent", together with the immediately transfers the datagram to the downstream relay node, toward upstream of the relay node "parity datagram transmission Suppress the transmission of "request" datagrams,
A data transfer method characterized by If the receiving relay node detects a loss of content datagrams:
Immediately transmit a “parity datagram transmission request transmitted” datagram to the downstream relay node,
The "parity datagram transmission request has been sent" datagram from the upstream relay node within the first waiting time set in advance after receiving the first datagram in the FEC block of the content datagram in which the loss occurred If not received, the first waiting time is T, and a predetermined second waiting time for fluctuations in the arrival time of the content datagram alpha, "parity datagram after the elapse of the waiting time (T + alpha) Send the "request for transmission" datagram towards the upstream relay node,
4. A data transfer method according to claim 3, wherein: A the relay nodes included in the data transfer system for transferring content datagrams using a plurality of relay nodes,
A first function of detecting loss of content datagrams;
The datagram of the “parity datagram transmission request” is sent before the “parity datagram transmission request” datagram including the identification number of the FEC block of the content datagram in which the loss occurred is transmitted to the upstream relay node. A second function of immediately transmitting to the downstream relay node a “parity datagram transmission request transmitted” datagram of transmitting to the upstream relay node;
When a “parity datagram transmission request transmitted” datagram is received from the upstream relay node , the datagram is immediately transferred to the downstream relay node and the “parity datagram transmission request” directed to the upstream relay node A third function to suppress the transmission of datagrams;
Relay nodes, characterized in that it comprises a. If the first feature detects a loss of content datagrams:
The second function is immediately transmitted toward datagrams "parity datagram transmission request Sent" downstream relay node,
The third function is data of “parity datagram transmission request transmitted” within a first waiting time set in advance after reception of the leading datagram of the FEC block of the content datagram in which the loss has occurred. If not receiving the grams upstream relay node, wherein the first waiting time is T, the predetermined second waiting time for fluctuations in the arrival time of the content datagrams with alpha, waiting time (T + alpha) It transmits the data grams of "parity datagram transmission request" to the upstream of the relay node after the course,
Relay nodes according to claim 5, wherein the this. The program for making a computer implement each function with which the relay node of Claim 5 or 6 is equipped .

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