JP5169788B2 - Network equipment - Google Patents

Description

  The present invention relates to a network device such as a relay device or a receiving node used in a data transmission system.

  ARQ (Automatic Repeat reQuest), which is an error correction technique, is a technique for automatically requesting a retransmission of a packet (loss packet) that the receiving side could not normally receive to the transmitting side and recovering the lost packet. However, when there are a plurality of receiving sides by using multicast, broadcast, or the like, there are problems that a retransmission request from each receiving side becomes a network load and a delay time until data reproduction increases. Therefore, it is difficult to adopt ARQ in real-time data transmission.

  For this reason, conventionally, error information is sent to the server side to change the redundancy of FEC (Forward Error Correction). FEC is a technique for repairing errors by adding redundant bits for error correction in advance to data to be transmitted on the transmission side and performing arithmetic processing using the redundant bits on the reception side.

  FIG. 1 is a diagram showing an example of a conventional data transmission system, in which broadcast data D is transmitted from a server SV to a receiving node ND1 via a relay device RL0 and then to the receiving node ND1 and also to the relay device RL2. To the receiving node ND2. Here, when the failure of error correction of the received packet frequently occurs in the receiving node ND1, the receiving node ND1 transmits the redundancy change request R1 to the server SV via the relay devices RL1 and RL0. The server SV that has received the redundancy change request R1 increases the error correction capability for the subsequent broadcast data D by increasing the redundancy of the FEC. As a result, error correction failure at the receiving node ND1 is reduced.

  FIG. 2 is a diagram showing another example of a conventional data transmission system. By providing a backup server in each relay device so that data can be retransmitted from each relay device, an increase in network load or the like is not caused. In this way, ARQ can be adopted.

  In FIG. 2, after the broadcast data D is transmitted from the server SV via the relay device RL0, it is transmitted to the receiving node ND1 via the relay device RL1, and is transmitted to the receiving node ND2 via the relay device RL2. At this time, the backup servers BS0, BS1, and BS2 connected to the relay devices RL0, RL1, and RL2 store the data relayed by the relay devices RL0, RL1, and RL2. After that, when an error of the received packet occurs in the receiving node ND1, the receiving node ND1 transmits a data retransmission request R2 to the relay device RL1, and the relay device RL1 can retransmit with the data stored in the backup server BS1. Data is acquired from the backup server BS1 and retransmitted to the receiving node ND1. When the relay device RL1 and the backup server BS1 cannot perform retransmission, the relay device RL1 transfers a retransmission request to a higher-level device (relay device RL0 or server SV), and performs retransmission from a device capable of retransmission. Since retransmission requests generated due to local network failures do not rise to the highest server SV, even if ARQ is employed, an increase in network load due to retransmission requests and retransmission data can be suppressed.

On the other hand, Patent Documents 1 and 2 disclose techniques for determining a device for retransmitting data by a management node. FIG. 3 shows an example of such a system. Broadcast data D is transmitted from the server SV to the receiving node ND1 via the network NW, the management node AN, and the relay device RL0, and then via the relay device RL1. At the same time, the data is transmitted to the receiving node ND2 via the relay device RL2. Here, when an error of the received packet occurs in the receiving node ND2, the receiving node ND2 transmits a data retransmission request R2 to the management node AN via the relay device RL2 and the relay device RL0. In this case, the management node AN transmits the retransmission server determination information C to the relay device RL2 via the relay device RL0, and the relay device RL2 becomes a retransmission server. Thereafter, the relay device RL2 acquires the data stored in the backup server BS2 and retransmits it to the receiving node ND2.
JP 2002-199013 A JP 2000-324155 A

The conventional data transmission system has various methods as described above, and has the following problems.
(1) In the data transmission system shown in FIG. 1, it is not possible to employ a retransmission technique based on ARQ, it is necessary to rely on error correction based on FEC, and recovery of lost packets cannot be performed quickly and reliably.
(2) In the data transmission system shown in FIG. 2, the backup server is always in operation, and all data passing through the relay device is accumulated at each point, so that memory is wasted and power consumption is large.
(3) In the data transmission system shown in FIG. 3, it is necessary to exchange information with the management node in order to determine a backup server in charge of retransmission among a plurality of backup servers, and it takes time to determine the server. Load up to the upper network.

  In view of the above-described conventional problems, an object of the present invention is to provide a network apparatus that can employ a retransmission technique using ARQ, minimize network load, and suppress waste of resources such as memory. .

  In one embodiment of this network device, when a retransmission data server activation request is received from the receiving node side, processing as a retransmission data server is started and relayed on condition that the function as a retransmission data server can be satisfied. And means for resending stored data when receiving a data retransmission request from the receiving node side after starting processing as a retransmission data server, and a retransmission data server from the receiving node side Means for stopping processing as a retransmission data server when a stop request is received.

  In the disclosed network device, since the network device having a relay function starts processing as a retransmission data server only when it is necessary on the receiving node side, a retransmission technique using ARQ can be adopted. The load can be minimized and the waste of resources such as memory can be suppressed.

  Hereinafter, preferred embodiments will be described. Although a data transmission system for transmitting broadcast data will be described as an example, the present invention is not limited to transmission of broadcast data, and can be applied to a system that requires data retransmission.

<Configuration>
FIG. 4 is a diagram illustrating a configuration example of a data transmission system according to an embodiment.

  In FIG. 4, the relay device RL0 is connected to the server SV that transmits the broadcast data D, and the relay devices RL1 and RL2 are connected to the relay device RL0. Then, the receiving node ND1 is connected to the relay device RL1, and the receiving node ND2 is connected to the relay device RL2. Note that the number of relay devices and the number of receiving nodes are not limited to those shown in the figure, and may be arbitrary depending on the scale of the system.

  Each relay device RL0, RL1, RL2 has a function as a retransmission data server in addition to a function as a relay device. The function of the retransmission data server is in the sleep state as an initial state, and is activated in response to a retransmission data server activation request from the receiving nodes ND1 and ND2. Once started, the retransmission data server goes to sleep again in response to a retransmission data server stop request from the receiving nodes ND1 and ND2.

  The server SV has a function of transmitting broadcast data and retransmitting a corresponding packet when a data retransmission request specifying a packet is received.

  FIG. 5 is a diagram illustrating a configuration example of the receiving node ND (ND1, ND2,...).

  5, the receiving node ND includes a packet transmitting / receiving unit 11, a packet analyzing unit 12, a packet loss monitoring unit 13, a packet processing unit 14, a packet processing monitoring unit 15, a packet generation unit 16, and a retransmission packet management unit 17. Yes.

  The packet transmitting / receiving unit 11 has a function of transmitting / receiving a packet to / from the nearest relay device.

  The packet analysis unit 12 has a function of analyzing a packet type, a transmission source address, a transmission destination address, a protocol, and the like for the packet received by the packet transmission / reception unit 11.

  The packet loss monitoring unit 13 has a function of passing a packet passed through the packet analysis unit 12 to the packet processing unit 14 and monitoring a packet loss due to packet loss or FEC failure by the packet processing unit 14. The packet loss monitoring unit 13 has a function of requesting the packet generation unit 16 to generate a retransmission data server activation request when it is determined that the packet reception state deteriorates and retransmission by ARQ is necessary. Yes. The retransmission data server activation request is a message instructing the start of a retransmission function by ARQ to the nearest or higher-level relay apparatus. Further, the packet loss monitoring unit 13 has a function of requesting the packet generation unit 16 to generate a retransmission data server stop request when it is determined that the packet reception state is improved and retransmission by ARQ is unnecessary. Yes. The retransmission data server stop request is a message for instructing the stop of the retransmission function by ARQ to the nearest or higher-level relay apparatus.

  The packet processing unit 14 performs packet processing in accordance with the purpose of voice / video, etc., error correction by FEC, request to the packet generation unit 16 for a packet data retransmission request by ARQ, recovery of a lost packet by a retransmission packet, etc. It has a function to perform the process. Note that the packet processing unit 14 sends a retransmission data server activation request to the nearest relay device via the packet generation unit 16 and the packet transmission / reception unit 11 and then performs a retransmission data server stop request. A request for generating a data retransmission request to the generation unit 16 and recovery of a lost packet by a retransmission packet are performed.

  The packet processing monitoring unit 15 has a function of monitoring the status of packet processing by the packet processing unit 14. The packet processing monitoring unit 15 has a function of requesting the packet generation unit 16 to generate a retransmission data server activation request when it is determined that the packet processing state deteriorates and retransmission by ARQ is necessary. Yes. Further, the packet processing monitoring unit 15 has a function of requesting the packet generation unit 16 to generate a retransmission data server stop request when it is determined that the packet processing state is improved and retransmission by ARQ is unnecessary. Yes.

  The packet generator 16 sends a data retransmission request from the packet processor 14 or a normal packet transmission request, and starts / stops the retransmission data server from the packet loss monitoring unit 13, the packet processing monitoring unit 15, or the retransmission packet management unit 17. It has a function of receiving a request for generating a request, generating a packet of a predetermined format, and transmitting it to the nearest relay device via the packet transmitting / receiving unit 11.

  The retransmission packet management unit 17 has a function of recording the reception state of the retransmission packet when the retransmission packet wait state is not a retransmission packet or when a retransmission packet is received. The retransmission packet management unit 17 has a function of requesting the packet generation unit 16 to generate a retransmission data server stop request when it is determined that the retransmission packet has not been received for a predetermined time or the number of times equal to or greater than the threshold value. doing.

  FIG. 6 shows an example of the data structure of a retransmission data server start / stop request packet. The retransmission data server start / stop request includes “packet type”, “destination address of retransmission request data”, “source address of retransmission request data”, “protocol of retransmission request data”, “source port number of retransmission request data”, “data” Items such as “storage time” and “number of relay devices” are included.

  In “packet type”, “1” means a retransmission data server activation request, and “0” means a retransmission data server stop request. Data that needs to be retransmitted is identified by the source address, destination address, and protocol of the data. Depending on the system, the source port number of UDP (User Datagram Protocol) is also used for identifying data that needs to be retransmitted. This is because even when a plurality of media are transmitted at the same transmission destination / transmission source, the transmission source port number is usually assigned to each medium.

  The data storage time is a time for storing packet data by the function of the retransmission data server. When a retransmission data server stop request is made, the data storage time is not subject to processing. The number of relay devices indicates the number of relay devices that go back to the upper rank when the retransmission data server activation request is not accepted. The number of relay devices may be directly written in the packet as shown, but it is also possible to use TTL (Time To Live) of an IP (Internet Protocol) header.

  The retransmission packet can be identified by a sequence number of RTP (Real-time Transport Protocol), which is an IP protocol for transmitting real-time media such as moving images and voices, and is used as a retransmission request packet as a management protocol RTCP that is paired with RTP. There is a NACK that notifies a packet with a missing (RTP Control Protocol), but a unique sequence may be used.

  FIG. 7 is a diagram illustrating a configuration example of the relay device RL (RL0, RL1, RL2,...).

  7, the relay device RL includes a packet switch unit 201, a routing table 202, a packet transmission / reception unit 203, a packet analysis unit 204, a transfer packet management unit 205, a packet generation unit 206, and a routing table management unit 207. The relay device RL includes a packet loss monitoring unit 208, a relay device number management unit 209, a memory amount monitoring unit 210, a memory management unit 211, a retransmission data memory 212, and a retransmission request management unit 213.

  The packet switch unit 201 has a function of checking the routing table 202 when a packet is received, and performing processing according to the routing table 202 for packets that hit the routing table 202. In addition, the packet switch unit 201 passes all packets including the packet that did not hit the routing table 202 to the packet transmitting / receiving unit 203.

  As shown in FIG. 8, the routing table 202 has items of “data type” and “processing”, and the “data type” is “destination IP address” “source IP address” “protocol” “transmission”. "Original port number" item.

  Returning to FIG. 7, the packet transmission / reception unit 203 has a function of receiving all packets from the packet switch unit 201 and transmitting packets via the packet switch unit 201.

  The packet analysis unit 204 has a function of analyzing a packet type, a transmission source address, a transmission destination address, a protocol, and the like for the packet received by the packet transmission / reception unit 203. The packet analysis unit 204 also has a function of recognizing whether or not the own relay device supports the function of the retransmission data server.

  The transfer packet management unit 205 determines a packet to be routed based on an analysis result by the packet analysis unit 204 for a packet that does not hit the routing table 202, generates a packet by the packet generation unit 206, and transmits and receives the packet transmission / reception unit 203. And a function of transmitting via the packet switch unit 201. Further, the transfer packet management unit 205 has a function of recording the routing processing contents in the routing table 202 through the routing table management unit 207. As a result, the packet switch unit 201 processes the corresponding packet thereafter.

  The packet generation unit 206 generates a packet in a predetermined format in response to a request from the transfer packet management unit 205, the relay device number management unit 209, the memory management unit 211, the retransmission request management unit 213, and the like. It has a function of transmitting via the switch unit 201.

  The routing table management unit 207 has a function of managing the contents of the routing table 202. The routing table management unit 207 deletes the contents registered in the routing table 202 after a predetermined time has passed as an aging process.

  The packet loss monitoring unit 208 has a function of monitoring packet loss due to packet loss from the packets that have passed through the packet analysis unit 204.

  The relay device number management unit 209 has a function of managing the number of relay devices of received packets. If the packet type is a retransmission data server activation request, the number of relay devices does not reach the limit value, and if the retransmission data server activation request is not accepted, the packet generation unit 206 is requested to send a higher-level relay device. Has a function of transmitting (transferring) a retransmission data server activation request. The relay device number management unit 209 subtracts 1 every time the number of relay devices (FIG. 6) of the retransmission data server activation request packet is relayed, and determines that the limit value has been reached when 0 is reached. Further, when the number of relay devices reaches the limit value and the retransmission data server activation request is not accepted, the relay device number management unit 209 requests the packet generation unit 206 to send data to the requesting receiving node or relay device. It has a function to send a resend impossible notification.

  The memory amount monitoring unit 210 has a function of monitoring the used memory amount and the remaining memory amount of the retransmission data memory 212.

  When receiving the retransmission data server activation request, the memory management unit 211 stores the packet data in the retransmission data memory 212, reads the packet data in response to the data retransmission request, and the data storage time of the retransmission data server activation request packet (FIG. 6). ) Based on the packet data discarding function.

  The retransmission data memory 212 is a memory that stores packet data in response to a data retransmission request.

  The retransmission request management unit 213 records the type (transmission destination address, transmission source address, protocol, transmission source port number, etc.) of data managed (saved) by the own relay device, and receives a data retransmission request. If it is the type of data to be managed, it has a function of transmitting retransmission data to the request source. That is, the memory management unit 211 acquires packet data from the retransmission data memory 212, and requests the packet generation unit 206 to transmit the retransmission data to the request source. When the retransmission request management unit 213 determines that the relay device number management unit 209 has a record of transferring the retransmission data server activation request to the higher-level relay device, the retransmission request management unit 213 requests the packet generation unit 206 to send the higher-level relay device. It has a function of transmitting (transferring) a data retransmission request and setting transfer settings from the transfer packet management unit 205 to the routing table 202 via the routing table management unit 207. Furthermore, the retransmission request management unit 213 records the reception status of the data retransmission request, and when the data retransmission request is not made for a certain time by the non-reception timer, the data as a retransmission data server is sent to the memory management unit 211. It also has a function to stop saving.

<Operation>
FIG. 9 is a flowchart showing an example of processing in the receiving node ND (ND1, ND2,...).

  In FIG. 9, when processing is started (step S101), the packet loss monitoring unit 13 and the packet processing monitoring unit 15 cause the packet error rate (packet loss due to packet loss, FEC failure by the packet processing unit 14 and packet processing unit). 14 determines whether or not the ratio of the packet processing error due to 14 exceeds a threshold value (step S102). If the packet error rate is low (low in step S102), the packet error rate is continuously monitored (step S102).

  When the packet error rate increases and exceeds the threshold (high in step S102), the packet loss monitoring unit 13 or the packet processing monitoring unit 15 requests the packet generation unit 16 to generate a retransmission data server activation request, and the packet transmission / reception unit The retransmission data server activation request is transmitted to the nearest relay device via 11 (step S103).

  Thereafter, the packet processing unit 14 determines whether or not data retransmission is necessary based on the quality of the received packet (step S104). If the packet processing unit 14 determines that data retransmission is necessary (Yes in step S104), the packet generation unit 16 sends the data retransmission. A request for request generation is requested, and a data retransmission request is transmitted to the nearest relay device via the packet transmitting / receiving unit 11 (step S105).

  Thereafter, the packet processing unit 14 determines whether or not retransmission data has been received (step S106). When the retransmission data is received (Yes in step S106), data recovery is performed based on the retransmission data (step S107).

  Whether or not the packet error rate has fallen below the threshold by the packet loss monitoring unit 13 and the packet processing unit 14 when it is determined that data retransmission is not necessary (No in step S104) or after data recovery with retransmission data (step S107) If it is determined (step S108) and the packet error rate is still high (high in step S108), the process returns to determining whether data retransmission is necessary (step S104).

  On the other hand, when the retransmission data is not received within the allowable time (No in step S106), the packet processing unit 14 performs data recovery by a conventional method such as FEC (step S109).

  Next, it is determined whether or not the retransmission data waiting time or the number of times up has exceeded a predetermined threshold (step S110). If it is equal to or less than the threshold (less than the threshold of step S110), it is determined whether data retransmission is necessary (step S104). Return to.

  When the packet error rate falls below the threshold (low in step S108), or when the retransmission data waiting time or the number of times up exceeds a predetermined threshold (above the threshold in step S110), the packet loss monitoring unit 13, packet processing monitoring The packet generator 16 requests the packet generator 16 to generate a retransmission data server stop request from the unit 15 or the retransmission packet manager 17, and transmits the retransmission data server stop request to the nearest relay device via the packet transceiver 11 (step S111). ).

  As a result, a series of processing ends (step S112), and the above processing (steps S101 to S112) is repeated again.

  FIG. 10 is a flowchart showing a processing example when the retransmission data server is started / stopped in the relay device RL (RL0, RL1, RL2,...).

  In FIG. 10, when processing is started (step S201), the packet analysis unit 204 determines whether or not a retransmission data server activation request has been received (step S202), and if not received (No in step S202), retransmission data. Waiting for reception of a server activation request (step S202).

  When the retransmission data server activation request is received (Yes in step S202), the packet analysis unit 204 determines whether or not the own relay device supports the function of the retransmission data server (step S203).

  When the own relay device supports the function of the retransmission data server (Yes in step S203), the packet loss monitoring unit 208 determines the packet loss rate of the own relay device (step S204), and the packet loss rate is a predetermined threshold value. If it is lower (low in step S204), the memory amount monitoring unit 210 determines whether the remaining memory amount is insufficient (step S205).

  Then, the memory amount monitoring unit 210 acquires the data storage time of the retransmission data server activation request packet (step S206), causes the memory management unit 211 to start storing data in the retransmission data memory 212, and causes the retransmission request management unit 213 to The data type to be stored is recorded (step S207). The data storage that has started continues until it is stopped. When a plurality of retransmission data server activation requests are accepted for the same data type, the one with the maximum storage time is applied.

  Thereafter, the packet analysis unit 204 determines whether or not a retransmission data server stop request has been received (step S208). If it is determined that it has not been received (No in step S208), the data analysis unit 204 proceeds to processing such as data storage (step S207). Return.

  If it is determined that a retransmission data server stop request has been received (Yes in step S208), the retransmission request management unit 213 determines whether there is no data retransmission request for a certain period of time (step S209), and the data retransmission request is received within a certain period of time. If it has been performed (No in step S209), the process returns to the determination of reception of the retransmission data server stop request (step S208).

  If it is determined that there is no data retransmission request for a certain period of time (Yes in step S209), the memory management unit 211 stops saving data in the retransmission data memory 212, clears the saved contents (step S210), and performs processing. The process ends (step S215).

  When a retransmission data server stop request is received and there is a record in which the retransmission data server start request is transferred to the higher-level relay device, the retransmission data server stop request is transferred to the higher-level relay device.

  On the other hand, if it is determined that the relay device does not support the function of the retransmission data server (No in step S203), the packet loss rate is higher than a predetermined threshold (high in step S204), or the remaining memory amount is insufficient. If it is determined that the number of relay devices in the retransmission data server activation request packet has reached the limit value (step S211), the relay device number management unit 209 determines whether the number of relay devices has reached the limit value.

  If the limit value has not been reached (OK in step S211), the relay device number management unit 209 requests the packet generation unit 206 to transmit a retransmission data server activation request to the upper relay device (step S212). When a plurality of retransmission data server activation requests for the same data type are collectively transmitted to the upper relay device, the storage time and the number of relay devices are integrated to the maximum value.

  Next, the relay device number management unit 209 records an event indicating that a retransmission data server activation request has been made to the relay device (step S213), and ends the processing (step S215).

  When the number of relay devices of the retransmission data server activation request packet has reached the limit value (NG in step S211), the relay device number management unit 209 requests the packet generation unit 206 to request the receiving node or relay device. A data re-transmission impossible notification is transmitted to the terminal (step S214), and the process is terminated (step S215).

  After completion of these series of processes, the above processes (steps S201 to S215) are repeated again.

  FIG. 11 is a flowchart illustrating a processing example when a data retransmission request is received in the relay device RL (RL0, RL1, RL2,...).

  In FIG. 11, when processing is started (step S221), the packet analysis unit 204 determines whether or not a data retransmission request has been received (step S222). If not received (No in step S222), a data retransmission request is received. Waiting for reception (step S222).

  When a data retransmission request is received (Yes in step S222), the retransmission request management unit 213 determines whether the data retransmission target is the type of data managed (stored) by the local relay device (step S223). .

  If it is determined that the data type is managed by the own relay device (Yes in step S223), the memory management unit 211 determines whether the requested packet data exists in the retransmission data memory 212 (step S223). S224).

  When it is determined that the requested packet data exists (Yes in step S224), the memory management unit 211 acquires the packet data from the retransmission data memory 212, and requests the packet generation unit 206 to transmit the retransmission data to the request source. (Step S225), and the process ends (Step S232).

  If it is determined that the requested packet data does not exist (No in step S224), the data retransmission request is discarded (step S226), and the process ends (step S232).

  On the other hand, if it is determined that the data type is not managed by the own relay device (No in step S223), the retransmission request management unit 213 transfers the retransmission data server activation request to the upper relay device by the relay device number management unit 209. It is determined whether there is a recorded record (step S227).

  When it is determined that there is a record in which the retransmission data server activation request has been transferred to the higher-level relay device (Yes in step S227), the retransmission request management unit 213 requests the packet generation unit 206 to send a data retransmission request to the higher-level relay device. Transmit (step S228).

  Next, transfer setting is performed from the transfer packet management unit 205 to the routing table 202 via the routing table management unit 207 (step S229), and the process is terminated (step S232). Therefore, the subsequent data retransmission request is directly transferred by the packet switch unit 201.

  Further, when it is determined that there is no record in which the retransmission data server activation request is transferred to the higher-level relay device (No in step S227), the data retransmission request is discarded (step S230), and the data is discarded in the routing table 202. The setting is made (step S231), and the process is terminated (step S232).

  After completion of these series of processes, the above processes (steps S221 to S232) are repeated again.

  FIG. 12 is a flowchart showing a processing example of a data non-reception check while the retransmission data server is running in the relay device RL (RL0, RL1, RL2,...).

  In FIG. 12, when processing is started (step S241), the retransmission request management unit 213 determines whether or not a data retransmission request has been received within a predetermined time (step S242), and when it has been received within a predetermined time (step S242). In step S242, the process waits for reception of the next data retransmission request (step S242).

  If the data retransmission request has not been received within the predetermined time (No in step S242), the retransmission request management unit 213 determines whether a retransmission data server stop request has been received (step S243).

  When it is determined that a retransmission data server stop request has been received (Yes in step S243), the retransmission request management unit 213 determines whether or not there is a data retransmission request for a certain period of time (step S244), and requests for data retransmission within a certain period of time. If it is determined that there has been (No in step S244), the process returns to the determination of reception of the retransmission data server stop request (step S243).

  On the other hand, when it is determined that the retransmission data server stop request has not been received (No in step S243), the retransmission request management unit 213 determines whether or not the retransmission data server stop request has been received for a certain time (step S245). If it is determined that the data has been received (No in step S245), the process returns to determining whether the data retransmission request has been received (step S242).

  When it is determined that there is no data retransmission request within a certain time (Yes in step S244) or when it is determined that a retransmission data server stop request has not been received for a certain time (Yes in step S245), a retransmission request management unit In step S213, the memory management unit 211 stops saving data in the retransmission data memory 212, clears the saved contents (step S246), and ends the process (step S247).

  After completion of these series of processes, the above processes (steps S241 to S247) are repeated again.

  Hereinafter, the operation | movement according to a condition is demonstrated separately.

  FIG. 13 is a diagram illustrating an example of processing of retransmission data server activation and data retransmission.

  In FIG. 13, when the receiving node ND1 receiving the broadcast data D increases the packet error rate and determines that data recovery by retransmission is necessary, the receiving node ND1 sends the retransmission data server activation request R11 to the nearest relay. The data is transmitted to the relay device RL1 that is a device.

  The relay device RL1 that has received the retransmission data server activation request R11 checks its own packet loss rate or remaining memory amount, and if it passes the determination with the threshold value, starts data storage and has the function of the retransmission data server. It becomes a device. Data storage is performed according to the storage time described in the retransmission data server activation request R11, and data that has passed the storage time is discarded.

  After receiving the retransmission data server activation request R11, the reception node ND1 transmits a data retransmission request R12 to the relay device RL1 when data retransmission is necessary. The relay device RL1 transmits the retransmission data D11 to the receiving node ND1 based on the data stored by the function as the retransmission data server.

  The receiving node ND1 performs recovery using the retransmission data D11 if the data is retransmitted, and performs the best data recovery that is currently possible if the retransmission of the data is not in time within a delay that allows retransmission.

  FIG. 14 is a diagram illustrating a processing example of retransmission data server stop.

  In FIG. 14, the receiving node ND1 that has transmitted the retransmission data server activation request (R11) thereafter periodically measures the packet error rate, and when the packet error rate decreases and determines that data recovery by retransmission is unnecessary. A retransmission data server stop request R13 is transmitted to the relay device RL1. Thereafter, the receiving node ND1 does not perform data recovery based on the data retransmission request and the retransmission data. The delay caused during the recovery with the retransmitted data is eliminated by the buffer in the receiving node ND1, and only the broadcast data D is processed again.

  The relay device RL1 that has received the retransmission data server stop request R13 ends data storage and ends its role as a retransmission data server.

  FIG. 15 is a diagram illustrating another example of processing for starting a retransmission data server. When the relay device that first receives the retransmission data server start request does not have the capability as the retransmission data server, the other relay device may send the retransmission data server. This is an example of processing when the retransmission data server position is optimized by retransmitting the activation request.

  In FIG. 15, when it is determined that the packet error rate is high at the receiving node ND1 that is receiving the broadcast data D and data recovery by retransmission is necessary, the receiving node ND1 sends a retransmission data server activation request R11 to the relay device RL3. Send to.

  The relay device RL3 that has received the retransmission data server activation request R11 checks its own packet loss rate or remaining memory amount, and has no capability as a retransmission data server because the packet loss rate is equal to or greater than the threshold value or the remaining memory amount is equal to or less than the threshold value. If it is determined, the retransmission data server activation request R14 is transmitted to the relay device RL1, which is a higher-level relay device.

  The relay device RL1 that has received the retransmission data server activation request R14 checks its own packet loss rate or the remaining memory amount, and if it passes the determination with the threshold value, starts data storage and has the function of the retransmission data server. It becomes a device.

  FIG. 16 is a diagram illustrating another example of processing for starting a retransmission data server, in which a relay apparatus that is already operating as a retransmission data server receives a retransmission data server startup request from another receiving node, This is an example of processing when the retransmission data server load is distributed by resending the retransmission data server activation request to another relay apparatus when there is no load-accepting capability.

  In FIG. 16, when a retransmission data server activation request R15 is issued from the receiving node ND1 that is receiving the data type dataB, the relay device RL3 that is the nearest relay device already has a retransmission data server for the data type dataA of the receiving node ND2. Further, when the relay device RL3 has insufficient memory to start storing new data, the relay device RL3 transmits a retransmission data server activation request R16 to the relay device RL1 which is a higher-level relay device.

  The relay device RL1 that has received the retransmission data server activation request R16 checks its own packet loss rate or the remaining memory amount, and if it passes the determination with the threshold value, starts data storage for the data type dataB, It becomes a device with functions.

  FIG. 17 is a diagram showing a processing example when the retransmission data server cannot be activated.

  In FIG. 17, when the receiving node ND1 transmits a retransmission data server activation request R17 to the relay device RL3 and the relay device RL3 is not accepted, the relay device RL3 transmits a retransmission data server activation request R18 to the higher-level relay device RL1. To do.

  In the above-described retransmission data server location optimization and retransmission data server load distribution, each relay device checks the number of relay devices described in the retransmission data server activation request, and the number of relay devices reaches a limit value. If so, the retransmission data server activation request is not transmitted to the upper relay apparatus. Therefore, when the relay device RL1 does not accept the retransmission data server activation request R18, the relay device RL1 transmits a retransmission impossible notification N1 to the relay device RL3, and the relay device RL3 transmits a retransmission impossible notification N2 to the receiving node ND1. . As a result, the retransmission data server is not activated.

  FIG. 18 is a diagram showing a processing example of data retransmission request transfer, and is a processing example at the time of data retransmission request when load distribution of the retransmission data server as shown in FIG. 16 is performed.

  In FIG. 18, when the relay device RL3 serving as the retransmission data server of the data type dataA of the receiving node ND2 receives the data retransmission request R19 of the data type dataB from the receiving node ND1, the relay device RL3 activates the retransmission data server. If there is a record of the request transmitted to the higher-level relay device, a data retransmission request R20 of the data type dataB is transmitted to the higher-level relay device RL1, and a setting is made to transfer the data type dataB to the higher level in the routing table. However, if the relay device RL3 has no record of sending the retransmission data server activation request to the higher-level relay device, the data retransmission request R19 is discarded and the data discard setting is made in the routing table. At this time, when a unicast address is used as the transmission destination address, the routing table is provided with a function of transferring the transmission destination address after the change. The changed transmission destination address is set to the address of the upper relay device.

<Summary>
As described above, the present embodiment has the following advantages.
(1) Since the relay apparatus has a function as a retransmission data server, it is possible to employ a retransmission technique based on ARQ and to effectively perform data recovery.
(2) Since the relay apparatus starts processing as a retransmission data server only when it becomes necessary on the receiving node side, waste of memory and power consumption can be reduced.
(3) Since the retransmission data server is determined only by the exchange between the receiving node and the neighboring relay device, the load on the entire network due to the management message can be suppressed, and the retransmission responsible relay device can be determined quickly.
(4) Generally, there is a possibility that a backup server may be equipped with an amount of memory that may not be used so that the data storage memory does not become full, or the data may not be retransmitted due to the memory being full. However, since the retransmission data server itself distributes the load of data storage, there is no need to install excessive memory or disable data retransmission.
(5) In general, even for retransmission of data that is difficult to retransmit, such as broadcast data, the network load is minimized, and even for systems that require low delay such as image / audio transmission, Therefore, it is possible to quickly construct a route for this purpose and to apply it.

The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments, various modifications and changes may be made to the embodiments without departing from the broad spirit and scope of the invention as defined in the claims. Obviously you can. In other words, the present invention should not be construed as being limited by the details of the specific examples and the accompanying drawings.
(Appendix 1)
Means for starting processing as a retransmission data server and storing data to be relayed on condition that the function as a retransmission data server can be satisfied when a retransmission data server activation request is received from the receiving node side;
Means for resending stored data when a data retransmission request is received from the receiving node side after starting processing as a retransmission data server;
A network device, comprising: means for stopping processing as a retransmission data server when a retransmission data server stop request is received from the receiving node side.
(Appendix 2)
In the network device according to attachment 1,
The condition for satisfying the function as a retransmission data server is that it has the function as a retransmission data server, the packet loss rate is not more than a predetermined threshold, and the storable amount of data is not less than the predetermined threshold. Network device.
(Appendix 3)
In the network device according to any one of Appendix 1 or 2,
A network device comprising means for transferring a retransmission data server activation request to an upper network device when the function as a retransmission data server cannot be satisfied.
(Appendix 4)
In the network device according to attachment 3,
A retransmission data server activation request is transferred to a higher-level network device within the limit of the number of relay devices described in the retransmission data server activation request, and a data retransmission impossible notification is transmitted to the request source when transfer is not possible Network device.
(Appendix 5)
In the network device according to any one of attachments 3 and 4,
A network device comprising means for transferring a data retransmission request to an upper network device.
(Appendix 6)
In the network device according to any one of appendices 1 to 5,
A network device that stores data to be relayed according to a storage time described in a retransmission data server activation request.
(Appendix 7)
In the network device according to any one of appendices 1 to 6,
A network device characterized in that when a retransmission data server stop request is received from the receiving node side, processing as a retransmission data server is stopped on condition that a data retransmission request has not been received for a certain period of time.
(Appendix 8)
In the network device according to any one of appendices 1 to 7,
A network apparatus comprising: means for stopping processing as a retransmission data server when a retransmission data server stop request has not been received from the receiving node for a certain period of time.
(Appendix 9)
Means for transmitting a retransmission data server activation request to the nearest network device when the packet error rate exceeds a predetermined threshold;
Means for transmitting a data retransmission request to the nearest network device when data recovery by data retransmission is required after transmitting a retransmission data server activation request;
Means for receiving retransmission data and performing data recovery;
A network device comprising: means for transmitting a retransmission data server stop request to the nearest network device when the packet error rate falls below a predetermined threshold.
(Appendix 10)
In the network device according to attachment 9,
A network device characterized in that, when retransmission data is not received within a predetermined allowable time, data recovery is performed by the best method.
(Appendix 11)
When receiving a retransmission data server activation request from the receiving node side, starting a process as a retransmission data server on condition that the function as a retransmission data server can be satisfied, and storing data to be relayed;
A step of resending stored data when a data retransmission request is received from the receiving node side after starting processing as a retransmission data server;
A data relay control method comprising: a step of stopping processing as a retransmission data server when a retransmission data server stop request is received from the receiving node side.

It is FIG. (1) which shows the example of the conventional data transmission system. It is FIG. (2) which shows the example of the conventional data transmission system. It is FIG. (3) which shows the example of the conventional data transmission system. It is a figure which shows the structural example of the data transmission system concerning one Embodiment. It is a figure which shows the structural example of a receiving node. It is a figure which shows the example of a data structure of a resending data server start / stop request packet. It is a figure which shows the structural example of a relay apparatus. It is a figure which shows the data structure example of a routing table. It is a flowchart which shows the process example in a receiving node. It is a flowchart which shows the example of a process at the time of retransmission data server starting / stopping in a relay apparatus. 7 is a flowchart illustrating an example of processing when a relay apparatus receives a data retransmission request. It is a flowchart which shows the process example of the data non-reception check in the resending data server starting in a relay apparatus. It is a figure which shows the example of a process of resending data server starting, and data resending. It is a figure which shows the example of a process of a resending data server stop. FIG. 10 is a diagram (part 1) illustrating another processing example of starting a retransmission data server; It is FIG. (2) which shows the other process example of retransmission data server starting. It is a figure which shows the example of a process in case retransmission data server starting cannot be performed. It is a figure which shows the example of a process of transfer of a data resending request.

Explanation of symbols

SV server ND, ND1 to ND3 Receiving node 11 Packet transmission / reception unit 12 Packet analysis unit 13 Packet loss monitoring unit 14 Packet processing unit 15 Packet processing monitoring unit 16 Packet generation unit 17 Retransmission packet management unit RL, RL0 to RL6 Relay device 201 Packet switch Unit 202 routing table 203 packet transmission / reception unit 204 packet analysis unit 205 transfer packet management unit 206 packet generation unit 207 routing table management unit 208 packet loss monitoring unit 209 relay device number management unit 210 memory amount monitoring unit 211 memory management unit 212 for retransmission data Memory 213 Retransmission request management unit

Claims (7)

Means for starting processing as a retransmission data server and storing data to be relayed on condition that the function as a retransmission data server can be satisfied when a retransmission data server activation request is received from the receiving node side;
Means for resending stored data when a data retransmission request is received from the receiving node side after starting processing as a retransmission data server;
A network device, comprising: means for stopping processing as a retransmission data server when a retransmission data server stop request is received from the receiving node side. The network device according to claim 1,
A network device comprising means for transferring a retransmission data server activation request to an upper network device when the function as a retransmission data server cannot be satisfied. The network device according to claim 2, wherein
A retransmission data server activation request is transferred to a higher-level network device within the limit of the number of relay devices described in the retransmission data server activation request, and a data retransmission impossible notification is transmitted to the request source when transfer is not possible Network device. The network device according to any one of claims 1 to 3,
A network device characterized in that when a retransmission data server stop request is received from the receiving node side, processing as a retransmission data server is stopped on condition that a data retransmission request has not been received for a certain period of time. The network device according to any one of claims 1 to 4,
A network apparatus comprising: means for stopping processing as a retransmission data server when a retransmission data server stop request has not been received from the receiving node for a certain period of time. Means for transmitting a retransmission data server activation request to the nearest higher-level network device when the packet error rate exceeds a predetermined threshold;
Means for transmitting a data retransmission request to the nearest higher-level network device when data recovery by data retransmission is required after transmitting a retransmission data server activation request;
Means for receiving retransmission data and performing data recovery;
A network device comprising: means for transmitting a retransmission data server stop request to the nearest higher-level network device when the packet error rate falls below a predetermined threshold value. When receiving a retransmission data server activation request from the receiving node side, starting a process as a retransmission data server on condition that the function as a retransmission data server can be satisfied, and storing data to be relayed;
A step of resending stored data when a data retransmission request is received from the receiving node side after starting processing as a retransmission data server;
A data relay control method comprising: a step of stopping processing as a retransmission data server when a retransmission data server stop request is received from the receiving node side.

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