JP2006285842A - Information processor and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a transmitted data volume. <P>SOLUTION: This information processor performing communication by a communication protocol accompanied by a confirmation response has: a data reception part receiving data transmitted from another information processor; a reception decision part deciding whether the data have been able to be received or not; and a confirmation response transmission part transmitting the confirmation response to the other information processor when having been able to receive the data. The confirmation response transmission part transmits the confirmation response to the other information processor even when having not been able to receive the data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information processing apparatus and a program.

Communication protocols with confirmation responses are used in various fields, and a method for efficiently performing communication using such communication protocols with confirmation responses has been proposed.
JP-A-5-336194 JP-A-5-103017

  However, since the amount of data to be communicated is expected to increase more and more, it is required to further reduce the amount of data to be transmitted.

  The present invention has been made in view of such a background, and an object thereof is to provide an information processing apparatus and program capable of reducing the amount of data to be transmitted.

  A main invention of the present invention for solving the above-described problem is an information processing apparatus that performs communication using a communication protocol with a confirmation response, and includes a data receiving unit that receives data transmitted from another information processing apparatus, A reception determination unit that determines whether or not data has been received; and a confirmation response transmission unit that transmits a confirmation response to the other information processing apparatus when the data has been received. Even when data cannot be received, the confirmation response is transmitted to the other information processing apparatus.

  According to the present invention, the amount of data to be transmitted can be reduced.

  Various data formats have been proposed that are resistant to data errors that occur during transmission due to advances in channel coding technology. In particular, for video data, many data specifications that have been subjected to error resilience coding such as MPEG-4 are established. Data that has been error-resistant encoded is lost due to noise or the like in the transmission line and does not reach the data (also referred to as data loss), and the lost data (hereinafter referred to as missing data) is recovered. (Error correction) can be performed (hereinafter also referred to as error tolerance).

  The background to the development of data specifications coded for error resilience is that (1) in real-time communication represented by streaming, there is a restriction on the delay time for transmission, and it is difficult to satisfy the restriction when resending missing data (2) In general, video data has a large data size and requires a long time to transfer the data, so that there is a possibility that a part of the data may be lost due to congestion of the transmission path. In addition, video data is being distributed by carrier companies such as CATV operators, and in the future, most of the amount of data transmitted and received in various transmission paths such as the Internet, CATV network, CDN, and mobile phone network will be used. It is thought to occupy.

  FEC (Forward Error Correction) is known as a technique for recovering such a loss of error-resistant encoded data. According to FEC, even if data is lost, the lost data can be recovered using data in the vicinity of the location where the data is lost. However, in the case where a so-called burst loss occurs in which a continuous area of data is lost, recovery of the lost data is difficult even by FEC. However, in general, when transmission lines with different bands, such as a wired network and a wireless network, are connected, burst loss occurs when data is transferred from a wide transmission line to a narrow transmission line. It can happen. For such a situation, in order to enable recovery of missing data by FEC even if a burst loss occurs, data is interleaved (alternately arranged) in advance and in the vicinity of the missing position necessary for recovery of missing data by FEC. It is also effective to make the data of the data discontinuous. An example of interleaving data will be described later.

  In recent years, although the reliability of transmission lines has become very high, data loss still occurs between transmission lines with different bands. In order to cope with this, in some communication protocols, an acknowledgment (ACK; ACKnowledge) is notified in order to confirm that data has arrived without loss. For example, TCP (Transmission Control Protocol) is well known as a protocol with such confirmation response. In a communication protocol with a confirmation response, the data reception device notifies the data transmission device of a confirmation response indicating that the data has been received, so that the transmission device confirms that the data transfer has been completed. ing. When the confirmation response is not notified, the transmitting apparatus repeats data retransmission until receiving the confirmation response notification. In this way, in the communication protocol with confirmation response, even when data loss occurs, the lost data can be recovered by retransmitting the lost data.

  There are technologies that improve the communication protocol with the confirmation response as described above. However, all of these technologies (1) repeat the retransmission from the transmission device until the data reception device receives all the data. There is a problem that the burden increases, (2) there is no compatibility with the existing communication protocol, and both the transmission device and the reception device must be modified.

  On the other hand, a communication protocol for recovering missing data without using an acknowledgment is also known. For example, in RTP (Real-time Transport Protocol) and RTCP (Real-time Control Protocol) specialized for video data transfer, statistical information indicating the data reception status (amount of missing data) from the receiving device to the transmitting device. Are notified at regular intervals. The transmission apparatus adjusts the amount of transmission data by thinning out video data based on this statistical information at the application level. In such control at the application level, (1) since it specializes in real-time video communication (application), it cannot be used for data transfer other than video. (2) Both the transmission device and the reception device are the same application. (3) In a best-effort type transmission path in which the change in available network bandwidth is drastic, there is a restriction that a delay in reporting statistical information occurs and stable data transfer is difficult.

  Hereinafter, a data communication system corresponding to the above situation will be described in detail with reference to the drawings.

=== System configuration ===
FIG. 1 is a diagram showing an overall configuration of a data communication system according to the present embodiment. As shown in the figure, the data communication system of the present embodiment corresponds to a data transmitting apparatus 101 (corresponding to another information processing apparatus of the present invention) and a data receiving apparatus 102 (corresponding to the information processing apparatus of the present invention). ). The data transmission apparatus 101 and the data reception apparatus 102 are connected via the transmission path 103, and data is transmitted from the data transmission apparatus 101 to the data reception apparatus 102. Examples of the transmission path 103 include Ethernet (registered trademark), public telephone line, wireless communication line, frame relay, ATM (Asynchronous Transfer Mode), LAN (Local Area Network), and WAN (Wide Area Network).

  The data transmission device 101 is a computer such as a personal computer or a workstation that transmits data to the data reception device 102 in accordance with a communication protocol with a confirmation response. There are various communication protocols involving confirmation responses, such as XMODEM and TCP. The data transmission apparatus 101 includes a memory 10, a CPU 11, and a communication interface 12, and a transmission program 104 is stored in the memory 10. The transmission program 104 is, for example, a program for streaming image content. The CPU 11 realizes a function of transmitting data to the data receiving apparatus 102 by executing the transmission program 104 stored in the memory 10.

  The data receiving apparatus 102 is a computer such as a personal computer or a workstation that receives data transmitted from the data transmitting apparatus 101. The data receiving device 102 includes a memory 15, a control device 16, and a communication interface 17. The memory 15 stores a loss determination program 105, a reception program 106, a retransmission determination program 107, and an intensity 108.

The deficiency determination program 105 is a program for detecting that data transmitted from the data transmission device 101 in the transmission path 103 is lost. The defect detection is performed, for example, when the data scheduled to be received cannot be received for a predetermined time. For the defect detection process, for example, a process performed by a general communication protocol such as a data defect detection process by TCP described later can be used.
As will be described later, the retransmission determination program 107 is a program for determining whether or not it is necessary to retransmit missing data.
The reception program 106 is a program for receiving data, transmitting an acknowledgment for the received data, and transmitting a retransmission request for the missing data to the data transmission apparatus 101.
The intensity 108 is a threshold value for determining whether or not recovery of missing data by FEC is possible, as will be described later.
The data receiving apparatus 102 receives the data from the data transmitting apparatus 101 by executing the loss detection program 105, the receiving program 106, and the retransmission determination program 107.

=== Data reception processing ===
In general, when data communication is performed according to a communication protocol with an acknowledgment response, if data is lost, the lost data (hereinafter referred to as “data loss”) is transmitted to the data transmission device 101 that transmits data from the data reception device 102 that receives the data. A message (hereinafter referred to as a retransmission request) instructing retransmission of the missing data is transmitted, and the missing data is retransmitted. FIG. 2 shows an example of a general retransmission process of missing data.

  Data 1 (DATA1) is sent from the data transmitting apparatus 101 to the data receiving apparatus 102 (S201), and when the data receiving apparatus 102 receives data 1, an acknowledgment 1 (ACK1) is returned (S202).

  On the other hand, when the data transmitting apparatus 101 sends out data 2 (DATA2) (S203) and data 2 is lost on the transmission path 103 (S204), the data receiving apparatus 102 detects the loss of data (S205), A retransmission request for the missing data (data 2) is sent to the data transmitting apparatus 101 (S206). When receiving the retransmission request for data 2, the data transmission apparatus 101 retransmits data 2 (S207).

  On the other hand, in the data receiving apparatus 102 of the present embodiment, even if data is lost, an acknowledgment is sent so that the data is not retransmitted. FIG. 3 shows an example of processing when data is not retransmitted. Similar to the processing shown in FIG. 3, when the data 2 (DATA2) transmitted from the data transmission device 101 is lost on the transmission path 103 (S204), the data reception device 102 detects the loss (S205). Even if a retransmission request is not sent, an acknowledgment 2 (ACK2) is transmitted to the data transmitting apparatus 101 (S301). As a result, the data transmitting apparatus 101 does not recognize that the data 2 is lost, and transmits the subsequent data 3 (DATA3) (S302).

  As described above, even if the data receiving apparatus 102 detects the loss of the data 2, the data communication can be performed without retransmitting the data 2 by transmitting an acknowledgment (ACK2) for the lost data 2 to the data transmitting apparatus 101. Can continue. Therefore, it is possible to reduce the transmission load of the transmission path 103 related to the retransmission of the data 2 and also reduce the processing load related to the retransmission of the data transmission apparatus 101. Such processing that does not retransmit the missing data is performed when the transmitted data does not matter even if there is some data loss, such as moving image data, or the data is recovered by FEC (error correction). This is particularly effective when it is possible to

  Further, when the data receiving apparatus 102 of the present embodiment is used, it is not necessary to modify the transmission program 104 of the data transmitting apparatus 101. Therefore, for example, the present invention can be easily applied to the case of receiving data from an existing data transmission apparatus 101 that performs streaming distribution of moving image data and audio data.

=== Reception Processing by TCP ===
Next, an example in which TCP widely used in the Internet or the like is employed as a communication protocol involving retransmission will be described. In TCP, the data transmission speed can be adjusted by so-called self-clocking, in which data arrival confirmation is sequentially performed and the next data transfer is started upon arrival of a confirmation response. Such a system is known to be an effective communication speed control system in a best-effort communication network represented by the Internet. On the other hand, since it is necessary for the data transmitting apparatus 101 to wait for the arrival of the confirmation response, the transfer rate may be inferior compared with the case where communication is performed according to a communication protocol that does not confirm the arrival of data. In addition, the amount of data sent to the transmission path 103 due to the retransmission of data increases, so the burden on the transmission path 103 increases.

  FIG. 4 shows an example of data communication processing by general TCP with retransmission. In TCP, data is transmitted in units of packets, and the data receiving apparatus 102 sends the number assigned to the last packet that could be continuously received to the data transmitting apparatus 101 as an acknowledgment (ACK).

  When receiving data according to general TCP, when the data receiving apparatus 102 receives three consecutive packets (DATA 1 to 3) (S401), it confirms the last packet number “3” (“3”). ACK3) is returned to the data transmitting apparatus 101 (S402). Here, after the fourth packet (DATA4) is transmitted (S403) and lost on the transmission path 103 (S404), the data receiving apparatus 102 receives the fourth and fifth packets without receiving the fourth packet. The second packet (DATA5-6) is received (S405). The data receiving apparatus 102 detects that the fourth packet (DATA4) is missing due to failure to receive consecutive numbered packets (S406). The data receiving apparatus 102 returns “3”, which is the number of the last packet that could be continuously received before the fourth packet, as an acknowledgment (ACK3) (S407).

  The data transmitting apparatus 101 detects that retransmission of the fourth packet is requested by the confirmation response of the same number “3” being repeatedly returned from the data receiving apparatus 102 (S408), and the fourth packet Is retransmitted (S409). When the data receiving apparatus 102 receives the fourth packet (DATA4), it means that it has received the first to sixth consecutive packets, and therefore transmits the data with the last packet number “6” as an acknowledgment (ACK6). It returns to the apparatus 101 (S410).

  FIG. 5 shows a flow of data reception processing according to TCP according to the present embodiment. In this embodiment, even when data is received according to TCP, as described above, even if data loss is detected, a confirmation response is sent, so that retransmission is omitted, and the communication load and data transmission of the transmission path 103 are omitted. The processing load on the apparatus 101 is reduced.

  In the case of the reception process according to the present embodiment, the data reception apparatus 102 detects the loss of the fourth packet (DATA4) in the same manner as the reception process with retransmission shown in FIG. 4 described above (S1006), An acknowledgment (ACK6) indicating that up to the sixth packet has been received is transmitted to the data transmitting apparatus 101 (S501). As a result, the data transmitting apparatus 101 continues to transmit the seventh and subsequent packets (DATA 7 to 9) to the data receiving apparatus 102 without retransmitting the packet (S502).

  As described above, the data transmitting apparatus 101 can continue to transmit the packet without performing retransmission even when the packet is lost, and thus can perform efficient data transmission.

=== Congestion avoidance processing ===
On the other hand, in the processing by TCP, when a packet is lost, the number of packets to be transmitted continuously is reduced to half, for example, avoiding congestion in a situation where a data amount exceeding the bandwidth of the transmission path 103 is transferred. However, in the reception process shown in FIG. 3 described above, the data transmission apparatus 101 continues to transmit data regardless of packet loss, and control to avoid congestion of the transmission path 103 due to TCP does not function. .

  Therefore, when detecting a packet loss, the data receiving apparatus 102 may return a confirmation response after waiting for a predetermined time. Thereby, the same effect as the avoidance of congestion by TCP is expected. FIG. 6 shows an example of reception processing when waiting for a predetermined time when packet loss is detected. As shown in the figure, when the data receiving apparatus 102 detects the loss of the fourth packet in the step (S406) as in the process of FIG. 4 above, it waits for a predetermined time (S601) and then sends an acknowledgment (ACK6). The data is sent out (S602). In the present embodiment, the predetermined time is set as a time (RTT) in which a packet reciprocates between the data transmitting apparatus 101 and the data receiving apparatus 102.

  In this way, in the reception process by TCP with the original retransmission, the number of packets to be sent forward is reduced by the congestion control as described above, but the retransmission is omitted as in this embodiment. Even so, the number of packets transmitted and received per unit time can be reduced. That is, congestion control is performed.

=== Error Resistant Coded Data ===
Next, error-resistant encoded data that is assumed to be transmitted in the data communication system of this embodiment will be described. When data is received in such a manner that retransmission is omitted as in the present embodiment, it is possible to recover missing data if the data is error-resistant encoded. FIG. 7 shows an example of the structure of error-resistant encoded data 701.

  The error-resistant encoded data 701 is formed from a plurality of data blocks 702. The size of each data block 702 is a data block length 703. The data block 702 is formed from a plurality of interleaved unit data 705. Interleaving means that a data block 702 is divided into a predetermined number (hereinafter referred to as interleaving number) of regions 704, and the divided region 704 is further divided into unit data 705 so that consecutive unit data 705 are not adjacent to each other. It is to rearrange. The size of the area 704 is the interleave length 704. For example, as shown in FIG. 7, the unit data 2 (705) included in the area 2 (704) is arranged next to the unit data 1 (705) included in the area 1 (704) (S711). The unit data 3 (705) included in the area 3 (704) is arranged in (S712), so that only one unit data 705 belonging to the same area 704 appears in the section of the interleave length 704. To do. By interleaving unit data 705 in this way, even if a burst loss with a length equal to or shorter than interleave length 704 occurs, all unit data 705 included in one area 704 is not lost. Therefore, it is possible to increase the possibility of repairing missing data by FEC when a burst loss occurs.

  Here, with respect to the data 701, a value indicating how many regions 704 out of the regions 704 included in one data block 702 cannot be recovered by the FEC is an intensity 108 (hereinafter referred to as “z”). Is also written.).

  In the present embodiment, it is assumed that the intensity 108 (z) is set in the range of (0 ≦ z ≦ 1). If the number of missing regions is s and the number of interleaves is m, it is determined that the missing data can be recovered by FEC when z> s ÷ m.

  In the present embodiment, data is received in units of unit data 705. The size of the unit data 705 is arbitrary, and can be, for example, 1 bit, 1 byte, 2 bytes or more.

=== Retransmission determination processing ===
In the data reception processing by the data receiving apparatus 102, it is determined whether the missing data can be recovered by FEC, and only when the missing data can be recovered, a confirmation response is returned so as not to retransmit. Is also suitable. FIG. 8 is a diagram showing a flow of processing for determining whether or not retransmission of missing data is necessary depending on whether or not missing data can be recovered.

  The data receiving apparatus 102 specifies the position of the missing data in the data 401 (hereinafter referred to as the missing position), and sets the missing position to “r” (S801). Next, the data receiving apparatus 102 calculates the remainder between the data length “r” from the beginning of the data 401 to the missing position and the data block length 405, and updates “r” (S802). Thus, “r” is the data length from the beginning of the data block 402 to which the missing data belongs (hereinafter referred to as the missing data block) to the missing position. The data receiving apparatus 102 identifies data missing in the past (hereinafter referred to as past missing data) among the unit data 405 included in the missing data block (S803), and the missing data or the area to which the past missing data belongs. The number of 406 (hereinafter referred to as a missing region) is calculated and set to “s” (S804). When the quotient between the number s of missing regions and the number of interleaves m is smaller than the intensity z (S805: YES), the data receiving apparatus 102 determines that retransmission is unnecessary (S806), and when the intensity is equal to or greater than z (S805: NO), it is determined that retransmission is necessary (S807).

  The data receiving apparatus 102 determines whether or not retransmission is necessary as described above when data to be received is lost, returns a retransmission request when retransmission is necessary, and confirms when retransmission is unnecessary. Send a response back. Thus, it is possible to reduce the communication load on the transmission path 103 and reduce the processing load on the data transmission apparatus 101 related to retransmission while ensuring that the missing data can be recovered. Such an effect can be realized without modifying the data transmission apparatus 101 that transmits data in accordance with a communication protocol with an existing general confirmation response. That is, the data receiving apparatus 102 can reduce the communication load on the transmission path 103 and the processing load on the data transfer apparatus 101 while maintaining compatibility with existing communication protocols.

  The data receiving apparatus 102 may determine the data format from the file name or URL of the data received from the data transmitting apparatus 101 and determine whether the data is error-resistant encoded data. . In this case, when the data to be received is not error-resistant coded, a general reception process is always performed in which a retransmission request for missing data is requested.

=== Progressive data reception processing ===
In the above description, it is assumed that the entire data 401 is error-resistant encoded data. Retransmission can be reduced.

  Here, a description will be given of data reception processing in which data without error resilience is arranged at the beginning of the data and data after error resilience coding is arranged (hereinafter referred to as progressive format).

  The structure of progressive format data (hereinafter abbreviated as progressive data) 901 is shown in FIG. As shown in the figure, a storage area 902 of a data length (hereinafter referred to as non-error resistant data length) of data having no error resistance (hereinafter referred to as non-error resistant encoded data) is provided at the beginning of the progressive data 901. The non-error-resistant encoded data 903 is arranged after the storage area 902 for the non-error-resistant data length. Further, following the non-error-resistant encoded data 903, the above-described error-resistant encoded data 701 is arranged. The non-error resistant data length 109 stored in the non-error resistant data length storage area 902 is obtained by adding the data length of the non-error resistant encoded data 903 to the data length of the storage area 902.

  In the case of receiving progressive data, the data receiving apparatus 102 has a configuration as shown in FIG. As shown in the figure, when receiving progressive data, in addition to the programs 105 to 107 and the strength 108 described above, the memory 15 of the data receiving apparatus 102 stores the non-error resistant data length 109 and the data in the progressive format. A data analysis program 110 for reading the non-error resistant data length 702 arranged at the head and storing it as the non-error resistant data length 109 of the memory 15 is stored.

  FIG. 11 shows a flow of processing for determining whether or not retransmission is necessary when progressive data 901 is received. In the retransmission determination process shown in the figure, in addition to the retransmission determination process of FIG. 8 described above, first, it is determined whether data in the storage area 902 of the non-error resistant data length is received (S1101), and the non-error resistant If the data in the data length storage area 902 has not been received (S1101: NO), it is determined that retransmission is necessary (S1107). When the data receiving apparatus 102 stores the non-error system data length 109 stored in the storage area 902 of the received non-error resistant data length in the memory 15 and identifies the position “r” of the missing data in (S801) In addition, it is determined whether or not “r” is smaller than the non-error resistant data length 109 stored in the memory 15 (S1102), and if “r” is smaller than the non-error resistant data length 109 (S1102: NO). That is, when data having no error tolerance is received, it is determined that retransmission is necessary (S807).

  In this way, the data receiving apparatus 102 performs a data reception process with general retransmission for a portion having no error resistance from the beginning of the progressive data 901 to the error resistant encoded data 903, and the error resistance is reduced. As described above, when a missing data can be recovered as described above, the missing data is not retransmitted. That is, according to the data receiving apparatus 102 of the present embodiment, even for progressive format data, the amount of transmission data on the transmission path 103 for retransmission of missing data is reduced, and the processing load related to retransmission of the data transmission apparatus 101 is reduced. Can be reduced.

=== Reception processing of data by HTTP ===
Data used in HTTP (hereinafter referred to as HTTP data), which is widely used in video distribution by TCP, is an example of the progressive format data described above.

  FIG. 12 shows the structure of HTTP data 1201. As shown in the figure, the HTTP data 1201 includes an HTTP header part 1202 and an HTTP body part 1203. The HTTP header portion 1202 is text format data having a length of the HTTP header length 1204, and the format is defined in HTTP. Arbitrary data can be stored in the HTTP body portion 1203.

  Even when receiving the HTTP data 1201, the data receiving apparatus 102 performs the same processing as the reception processing shown in FIG. The difference from the reception process shown in FIG. 11 is that since the HTTP header length 1204 is a fixed value defined in HTTP, the determination of whether or not the storage area 902 for the non-error resistant data length has been received (S1101) is omitted. Be able to.

  The data receiving apparatus 102 executes the data analysis program 110, analyzes the HTTP header part 1202, determines whether the data stored in the HTTP body part 1203 is error-resistant encoded data, When data having no error tolerance is stored, it is possible to perform reception processing with retransmission.

=== Application example ===
The data communication system according to the above-described embodiment can be applied to a monitoring information storage system, for example. FIG. 13 shows a configuration example of the data transmitting apparatus 101 and the data receiving apparatus 102 in the system for accumulating monitoring information. In this case, as illustrated in FIG. 13, the data transmission device 101 includes a monitoring information input device 1301 such as a camera or a sensor, and transmits the monitoring information to the data reception device 102. The data transmitting apparatus 101 may include a storage device 1302 such as a hard disk that stores the input monitoring information. The data receiving apparatus 102 includes a storage device 1303 that records monitoring information transmitted from the data transmitting apparatus 101.

  In the reception processing of the monitoring information input from the input devices 1301 such as a plurality of cameras / sensors as described above, the communication load on the transmission path 103 is suppressed without modifying a large number of cameras / sensors as described above. Thus, monitoring information from more input devices 1301 can be transferred via the same transmission path 103.

=== Gateway device ===
Next, an embodiment will be described in which the above-described data reception processing by the data reception device 102 is applied to data transfer processing in a data transfer (gateway) device 1402 that transfers data between transmission paths.

  FIG. 14 is a diagram illustrating a configuration example of a data transfer system including the data transfer apparatus 1402 according to the present embodiment. As shown in the figure, the data transfer system includes a data transmission apparatus 101, a data reception apparatus 1401, and a data transfer apparatus 1402. The data transmission device 101 and the data transfer device 1402 are communicably connected via the transmission path 103, and the data transfer device 1402 and the data reception device 1401 are communicably connected via the transmission path 1403. A transmission path 1403 that connects the data transfer device 1402 and the data reception device 1401 is, for example, the Internet or a mobile phone network.

  The data transmission device 101 is the same as the data communication system described above, and is, for example, a video distribution server.

  The data receiving device 1401 is a computer such as a personal computer or a mobile phone that receives data transmitted from the data transmitting device 101. The data receiving device 1401 includes a CPU 19, a memory 18, and a communication interface 20, and the memory 18 stores a receiving program 1405 for receiving data. The reception program 1405 is a program for receiving data in accordance with a communication protocol involving general retransmission. The data reception device 1401 implements a data reception function by executing a reception program 1405.

  The data transfer apparatus 1402 is a computer that transfers data sent from the data transmission apparatus 101 to the transmission path 103 to the data reception apparatus 1401 via the transmission path 1403, and is, for example, a router, a repeater, or a gateway. In this embodiment, the data reception device 1401 is a mobile phone, and the data transfer device 1402 is a base station that performs wireless packet communication with the data reception device 1401 via a wireless transmission path 1403. Assumed.

  The data transfer device 1402 has the same configuration as the data reception device 102 in FIG. 1 described above, but includes a plurality of communication interfaces 17 for connection to both the transmission paths 103 and 1403. The memory 15 of the data transfer device 1402 stores a transfer program 1404 instead of the reception program 106, and the strength 108 is omitted. The transfer program 1404 is a program for receiving data transmitted from the data transmitting apparatus 101 and transferring the received data to the data receiving apparatus 1401.

  In the data transfer device 1402 of the present embodiment, even if data loss is detected, the data transfer device 1402 transmits a confirmation response to the data transmission device 101 in the same manner as the data reception processing shown in FIG. Data is not resent. Furthermore, the data transfer apparatus 1402 of the present embodiment has data having the same data length as that of the missing data, for example, “0 (zero)”, instead of the missing data (hereinafter referred to as dummy data). The created dummy data is transmitted to the data receiving device 1401.

  FIG. 15 is a diagram illustrating an example of data transfer processing in the data transfer system according to the present embodiment. As shown in the figure, when the data transfer apparatus 1402 receives data 1 (DATA1) sent from the data transmission apparatus 101 (S1501), the data transfer apparatus 1402 transmits the received data 1 to the data reception apparatus 1401 ( S1502). The data reception device 1401 returns an acknowledgment 1 (ACK1) to the received data 1 (S1503), and the data transfer device 1402 transmits the acknowledgment 1 returned from the data reception device 1401 to the data transfer device 101. (S1504).

  When data 2 (DATA2) is sent from the data transmission apparatus 101 (S1505) and lost on the transmission path 103 (S1506), the data transfer apparatus 1402 detects the loss of data 2 (S1507), and dummy Data 2 (dummy 2) is created and transmitted to the data receiving device 1401 (S1508). The data receiving device 1401 returns an acknowledgment 2 (ACK2) for the dummy data 2 (S1509), and the data transfer device 1402 transfers the acknowledgment 2 to the data transmitting device 101 (S1510).

  When data 3 (DATA3) is transmitted from the data transmitting apparatus 101 (S1511) and the data transfer apparatus 1402 transfers the data 3 to the data receiving apparatus 1401 (S1512), when the data 3 is lost on the transmission line 1503 (S1513), data transmission processing involving general retransmission is performed. That is, when the data receiving device 1401 detects the loss of data (S1514) and transmits a retransmission request for the lost data 3 to the data transfer device 1402 (S1515), the data transfer device 1402 receives the data 3 in response to the retransmission request. The data is transmitted to the data receiving device 1401 (S1516).

  As described above, when data is lost on the transmission path 103 between the data transmission apparatus 101 and the data transfer apparatus 1402, retransmission of the missing data is not performed. Thereby, the communication load of the transmission path 103 can be reduced, and the processing load related to the retransmission of the data transmission apparatus 101 can be reduced. Further, since dummy data is transmitted to the data receiving device 1401 as an alternative to the missing data, the data receiving device 1401 can continue the data receiving process without detecting the missing data. Further, these effects can be realized without modifying any of the data transmission apparatus 101 or the data reception apparatus 1401 that performs communication according to a communication protocol that involves a general retransmission. Therefore, for example, in a video distribution service on the Internet, the present invention can be easily applied to a transmission device that distributes a large number of existing videos on the Internet and a receiving device such as an existing mobile phone.

  In the above processing, the data transfer device 1402 may recover the error of the missing data by FEC or the like and transmit the recovered data to the data reception device 1401 instead of sending the dummy data. In this case, the data transfer device 1402 stores the strength 108 in the memory 15 and performs the retransmission determination process of FIG. 8 described above, and returns a retransmission request to the data transmission device 101 when the missing data cannot be recovered. It may be.

=== Receiving processing of MPEG format data ===
Next, an MPEG data communication system for transmitting MPEG format data (hereinafter referred to as MPEG data) will be described as a third embodiment. The configuration of the MPEG data communication system according to this embodiment is shown in FIG. As shown in the figure, the MPEG data communication system according to the present embodiment includes a data configuration information management apparatus 1601 in addition to the data transmission apparatus 101 and the data reception apparatus 102 in the data communication system of FIG. ing.

  The data configuration information management device 1601 is a computer that manages data configuration information described later. The data configuration information management device 1601 includes a memory 21, a CPU 22, and a communication interface 23. The data configuration information transmission program for transmitting data configuration information 1602, which will be described later, and the data configuration information 1602 to the data receiving device 102. 1603 is stored.

  The data transmission apparatus 101 has the same configuration as the data transmission apparatus 101 in FIG. 1 described above, but the data to be transmitted is in the MPEG format. In the data receiving apparatus 102, a data configuration information acquisition program 1604 is stored in the memory 15 in addition to the configuration of the data receiving apparatus 102 described above. Note that the intensity 108 stored in the memory 15 is omitted. The data configuration information acquisition program 1604 is a program for acquiring the data configuration information 1602 managed by the data configuration information management device 1601.

  FIG. 17 shows an example of the structure of MPEG data standardized as MPEG2. MPEG data 1701 is data composed of a plurality of still images in which error-resistant portions are dispersed. As shown in FIG. 17, the MPEG data 1701 is composed of any type of block of an I picture 1702, a B picture 1703, and a P picture 1704. The I picture 1702 is obtained by encoding an entire still image. A B picture 1703 and a P picture 1704 are obtained by encoding only difference information between two I pictures 1702, and most of the MPEG data 1701 is a B picture 1703 or a P picture 1704. If the I picture 1702 is lost, the B picture 1703 and the P picture 1704 that are differential images cannot be decoded correctly, so that there is a large amount of data that cannot be decoded as a whole, and the video obtained by decoding the MPEG data 1701 is greatly disturbed. On the other hand, even if the B picture 1703 or the P picture 1704 is lost, as long as the I picture 1702 can be received, the video is not greatly disturbed. Therefore, when receiving the MPEG data 1701, the data receiving apparatus 102 according to the present embodiment needs to retransmit the missing data for the I picture 1702, and does not need to retransmit the B picture 1703 and the P picture 1704. Try to judge that there is.

  Whether the missing data is included in the I picture 1702 is determined with reference to the data configuration information 1602. FIG. 18 shows the structure of the data configuration information 1602. As shown in FIG. 18, the data configuration information 1602 includes information for specifying the range of the I picture 1702 in the MPEG data 1701.

  The data reception apparatus 102 acquires the data configuration information 1602 from the data configuration information management apparatus 1601 in advance before performing the reception process of the MPEG data 1701. Note that when the data receiving apparatus 102 receives the data configuration information 1602 from the data configuration information management apparatus 1601, the data receiving apparatus 102 performs a reception process involving retransmission.

  FIG. 19 is a diagram showing a flow of processing for determining whether or not retransmission of missing data is necessary when MPEG data 1701 is received. As shown in the figure, in the retransmission determination processing by the data receiving apparatus 102 according to the present embodiment, the position of the missing data in the MPEG data 1701 is “r” (S1901), and “r” is included in the range of the I picture 1702. It is determined whether or not (S1902). If the position “r” of the missing data is included in the range of the I picture 1702 (S1902: YES), the data receiving apparatus 102 determines that retransmission is necessary (S1903). On the other hand, if the position “r” of the missing data is included in the range of the I picture 1702 in the MPEG data 1701 (S1902: NO), it is determined that retransmission is necessary (S1904).

  As described above, according to the data receiving apparatus 102 of the present embodiment, when MPEG format data is received, the B picture 1703 and the P picture 1704 that have little influence on the video decoded from the MPEG data 1701 are lost. By not performing retransmission, the communication load on the transmission path 103 and the processing load on the data transmission apparatus 101 can be reduced.

  FIG. 20 shows an example of the flow of MPEG data reception processing in this embodiment. The data receiving apparatus 102 acquires the data configuration information 1704 from the data configuration information transmitting apparatus 1708 (S2001). For obtaining the data configuration information 1704, for example, a command for acquiring the data configuration information 1704 is transmitted from the data receiving device 102, and the data configuration information management device 1708 responds with the data configuration information 1704 in response to the command. To.

  When receiving the data 1 (DATA1) sent from the data transmitting apparatus 101 (S2002), the data receiving apparatus 102 returns an acknowledgment 1 (ACK1) (S2003). Subsequently, when the data transmitting apparatus 101 sends out data 2 (DATA2) (S2004) and the data 2 is lost on the transmission path 103 (S2005), the data receiving apparatus 102 detects the loss (S2006), Whether or not data retransmission is necessary is determined by the above-described processing of FIG. If it is determined that retransmission of the missing data is unnecessary, the data receiving apparatus 102 responds with an acknowledgment 2 (ACK2) for the missing data 2 (S2007). The data transmitting apparatus 101 sends the subsequent data 3 (DATA3) without retransmitting the data 2 (S2008). In this way, the data transmission apparatus 101 can continue the MPEG data transmission process without retransmitting the data 2, so that efficient communication can be performed.

  The data configuration information 1602 may be managed by the data transmitting apparatus 101 and transmitted to the data receiving apparatus 102 prior to transmission of the MPEG data 1701.

  In addition to the MPEG data, the processing of the present embodiment can be easily applied to various types of data in which the degree of influence due to data loss differs depending on the data portion.

  Although the present embodiment has been described above, the above embodiment is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

It is a figure which shows the whole structure of the data communication system which concerns on this embodiment. It is a figure which shows the example of the resending process of a general missing data. It is a figure which shows the example of a process when not resending data. It is a figure which shows an example of the data communication process by the general TCP which accompanies resending. It is a figure which shows an example of the data reception process when resending is abbreviate | omitted. It is a figure which shows the example of a reception process in the case of waiting for predetermined time, when the loss | missing of a packet is detected. It is a figure which shows an example of the structure of the data 701 by which error tolerance coding was carried out. It is a figure which shows the flow of the process which determines whether resending of missing data is required. It is a figure which shows the structure of progressive data. It is a figure which shows the structure of the data receiver 102 in the case of receiving progressive data. It is a figure which shows the flow of the process which determines whether resending is required when receiving the progressive data 901. FIG. It is a figure which shows the structure of the HTTP data 1201. FIG. It is a figure which shows the structural example of the data transmitter 101 and the data receiver 102 in the system which accumulate | stores monitoring information. It is a figure which shows the structural example of the data transfer system containing the data transfer apparatus 1402 which concerns on 2nd Embodiment. It is a figure which shows an example of the data transfer process in the data transfer system which concerns on 2nd Embodiment. FIG. 16 shows the configuration of an MPEG data communication system according to the third embodiment. It is a figure which shows the structural example of the MPEG data currently standardized as MPEG2. It is a figure which shows the structure of the data structure information. It is a figure which shows the flow of a process which judges whether retransmission of missing data is required in the case of receiving MPEG data. It is a figure which shows an example of the flow of the reception process of MPEG data in 3rd Embodiment.

Explanation of symbols

10 memory 11 CPU
DESCRIPTION OF SYMBOLS 12 Communication interface 15 Memory 16 CPU 17 Communication interface 101 Data transmission apparatus 102 Data reception apparatus 103 Transmission path 104 Transmission program 105 Missing determination program 106 Reception program 107 Retransmission determination program 108 Strength 109 Non-error tolerance data length 110 Data analysis program 701 Data 702 Data block 703 Data block length 704 Area 705 Unit data 901 Progressive data 902 Non-error resistant data length storage area 903 Non-error resistant data 1201 HTTP data 1202 HTTP header 1203 HTTP body 1204 HTTP header length 1301 Input device 1302 Storage device 1401 Data reception Device 1402 Data transfer device 1403 Transmission path 1404 Transfer program Arm 1405 receiving program 1601 data configuration information management unit 1602 data structure information 1603 data structure information transmission program 1604 data structure information acquisition program 1701 MPEG data 1702 I picture 1703 B-picture 1704 P picture

Claims (12)

An information processing apparatus that performs communication using a communication protocol with a confirmation response,
A data receiving unit that receives data transmitted from another information processing apparatus;
A reception determination unit that determines whether the data has been received;
An acknowledgment transmission unit that transmits an acknowledgment to the other information processing apparatus when the data can be received;
The confirmation response transmission unit transmits the confirmation response to the other information processing apparatus even when the data cannot be received;
An information processing apparatus characterized by the above. The information processing apparatus according to claim 1,
The communication protocol is TCP;
An information processing apparatus characterized by the above. The information processing apparatus according to claim 1,
An error correction availability determination unit that determines whether error correction is possible for the data when the data cannot be received;
The confirmation response transmission unit transmits the confirmation response to the other information processing apparatus when error correction for the data is possible;
An information processing apparatus characterized by the above. The information processing apparatus according to claim 3,
An unreceivable number storage unit that stores an unreceivable number that is the number of the data that could not be received by the data receiving unit when receiving a predetermined number of the data;
The correction propriety determining unit determines whether or not error correction for the non-received data is possible according to the unreceivable number;
An information processing apparatus characterized by the above. The information processing apparatus according to claim 4,
A strength information storage unit that stores strength information that is information for determining the number of data that can be received but cannot be corrected among the data belonging to the series of data transmitted from the other information processing apparatus; Prepared,
The correction propriety determination unit determines whether the error correction is possible by determining whether the unreceivable number is smaller than a number determined by the strength information;
An information processing apparatus characterized by the above. The information processing apparatus according to claim 3,
A non-tolerant data number receiving unit that receives from the other information processing apparatus a non-resistant data number that is the number of data groups that cannot be corrected among the series of data transmitted from the other information processing apparatus;
A non-resistant data number storage unit for storing the non-resistant data number;
A reception data number storage unit that stores a reception number that is the number of data received by the data reception unit among the data belonging to the series of data groups;
The correction possibility determination unit determines whether the error correction is possible based on whether the reception number stored in the reception data number storage unit is greater than or equal to the non-resistant data number;
An information processing apparatus characterized by the above. The information processing apparatus according to claim 3,
A data configuration information storage unit for storing data configuration information for specifying the error correctable portion in the entire data configured by a series of the data group transmitted from the other information processing apparatus;
The correction possibility determination unit specifies a position in the entire data corresponding to the received data, and whether the error correction is possible depending on whether the specified position is included in the portion specified by the data configuration information To judge whether
An information processing apparatus characterized by the above. The information processing apparatus according to claim 1,
The confirmation response transmission unit waits for a predetermined time when the data cannot be received, and transmits the confirmation response to the other information processing apparatus;
An information processing apparatus characterized by the above. An information processing apparatus for transferring data transmitted from a first information processing apparatus to a second information processing apparatus,
A data receiving unit for receiving data transmitted from the first information processing apparatus;
A reception determination unit that determines whether the data has been received;
An acknowledgment transmission unit for transmitting an acknowledgment to the first information processing apparatus when the data is received;
Data that transmits the received data to the second information processing apparatus when the data can be received, and transmits the substitute data to the second information processing apparatus when the data cannot be received A transmission unit;
An alternative data creation unit that creates alternative data that is data having the same data length as the data length of the data to be received when the data cannot be received;
The confirmation response transmission unit transmits the confirmation response to the first information processing apparatus even when the data cannot be received;
An information processing apparatus characterized by the above. An information processing apparatus that performs communication using a communication protocol with a confirmation response,
A data receiving unit that receives data transmitted from another information processing apparatus;
A reception determination unit that determines whether the data has been received;
An error correction availability determination unit that determines whether error correction for the data is possible when the data cannot be received;
A confirmation response transmission unit that transmits the confirmation response to the other information processing apparatus when the data can be received and when the error correction is possible;
An information processing apparatus comprising: A method for controlling an information processing apparatus that performs communication using a communication protocol with a confirmation response,
The information processing apparatus is
Receives data transmitted from other information processing devices,
Determine whether the data has been received,
When the data can be received, an acknowledgment is sent to the other information processing apparatus,
Transmitting the confirmation response to the other information processing apparatus even when the data cannot be received;
An information processing apparatus characterized by the above. A program for performing communication using a communication protocol with a confirmation response,
In the information processing device,
Receiving data transmitted from another information processing apparatus;
Determining whether the data could be received;
Transmitting an acknowledgment to the other information processing apparatus when the data can be received;
Transmitting the confirmation response to the other information processing apparatus even when the data cannot be received;
A program for running

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