JP2013127719A - Web information acquisition method and prefetch proxy server - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase transmission efficiency by appropriately selecting a TCP protocol and a UDP protocol in the case of transferring prefetched WEB information between a prefetch proxy server and an information storage server.SOLUTION: A transmission delay time is periodically measured between a prefetch proxy server and an information storage server, and when the measured transmission delay time is equal to or less than a fixed time, a TCP protocol is used, and when the measured transmission delay time exceeds the fixed time, Web information prefetched by using a UDP protocol is transmitted to the information storage server. Also, the prefetch proxy server retransmits the packet of a sequence number whose retransmission is requested from the information storage server by using the TCP protocol.

Description

  In the present invention, a WEB browsing apparatus (for example, a personal computer or a portable terminal, hereinafter referred to as “PC”) on a network receives WEB content information (hereinafter referred to as “WEB information”) from a WEB providing apparatus (hereinafter referred to as “WEB server”). At the time of acquisition, a pre-read proxy server is installed between the PC and the WEB server, the WEB information requested by the PC to the WEB server is pre-read in the pre-read proxy server, and the PC is scheduled to request based on the pre-read WEB information. The present invention relates to a WEB information acquisition method and a prefetching proxy server that shortens WEB information acquisition time by acquiring WEB information in advance and transferring the WEB information to a PC in response to a request from the PC.

  When a PC browses WEB information from a WEB server on a network such as the Internet, the WEB server uses WEB information to the PC using HTML (HyperText Markup Language) according to the HTTP (Hypertext Transfer Protocol) communication protocol. Is transmitted. For example, when the file index.html provided by the WEB server byte.tokkyo.co.jp is acquired by HTTP, the WEB information is read out at the address http://byte.tokkyo.co.jp/index.html. it can. When reading the WEB information, the user generally reads the WEB information by designating an address using a program for browsing the WEB information (hereinafter referred to as “browser”). In the PC, when the user inputs an address, the browser issues a page request to the WEB server. The WEB server receives this page request transmitted via the network, and transmits the WEB information of the requested page to the PC via the network. In this way, each time a page request is received from the user, the browser of the PC acquires the corresponding page via the network.

  In recent years, there has been a demand for shortening the time from when a PC user requests acquisition of WEB information to when the WEB information is given to the PC. Further, for example, since a predetermined delay time occurs in a high-delay network such as a satellite line, a transmission method that assumes such a network is required. In order to meet these requirements, Patent Document 1 discloses a technique for prefetching WEB information.

FIG. 4 shows a configuration example of a communication network including a conventional WEB information acquisition apparatus (Patent Document 1).
In FIG. 4, the WEB server 11 is connected to the Internet 12. A PC 13, which is an example of a WEB browsing apparatus, is connected to the Internet 12 via a LAN 14 and a high delay network 15. A gateway GW is arranged at a connection point of each network. Here, the high-delay network 15 is a so-called WAN (Wide Area Network) that interconnects remote computers using, for example, a broadband wireless system or a satellite line, and has a predetermined delay time according to its scale and the like. Will occur.

  The prefetch proxy server 20 used in the present invention is connected to a predetermined position on the WEB server 11 side from the high delay network 15, for example, the Internet 12 or between the Internet 12 and the high delay network 15. On the other hand, the information storage server 30 is connected to the LAN 14 to which the PC 13 is connected. That is, the time for the PC 13 to access each server becomes shorter in the order of the WEB server 11, the prefetching proxy server 20, and the information storage server 30.

  FIG. 5 shows a conventional WEB information acquisition processing sequence. Here, the request data for the PC 13 to browse the WEB information data1 of the WEB server 11 is set to get1. The WEB server 11 outputs WEB information data1 according to get1. The data1 is an HTML file, which includes a URL and the like necessary for the PC to generate the next request data get2, and the prefetching proxy server 20 generates the get2 from the data1 and uses it as the prefetch get2. Transmit to the WEB server 11. The WEB information output by the WEB server 11 in response to get2 or prefetch get2 is assumed to be data2.

  In FIG. 5, the PC 13 transmits get 1 to the WEB server 11. The information accumulation server 30 and the prefetching proxy server 20 accumulate the get 1 and transfer the get 1 toward the WEB server 11. The WEB server 11 transmits data1 corresponding to get1 to the PC 13. Since the prefetch proxy server 20 and the information storage server 30 store get1 corresponding to data1, the data1 is transferred to the PC 13 as it is. Further, the prefetch proxy server 20 generates a prefetch get2 from the data1 and transmits it to the WEB server 11, and transmits a prefetch request notification signal for notifying the information storage server 30 of the prefetch get2. The information storage server 30 receives the prefetch request communication signal transmitted from the prefetch proxy server 20, and waits for reception of data2 corresponding thereto.

  The WEB server 11 transmits data2 corresponding to the prefetch get2 to the PC 13. The prefetching proxy server 20 transfers the prefetched data2 toward the PC 11. The information accumulation server 30 accumulates the prefetched get2, but does not input get2 from the PC 13, and therefore temporarily accumulates the prefetched data2.

  The WEB server 11 transmits data2 corresponding to the prefetch get2 to the PC 13. The prefetching proxy server 20 transfers the prefetched data2 toward the PC 11. The information accumulation server 30 accumulates the prefetched get2, but does not input get2 from the PC 13, and therefore temporarily accumulates the prefetched data2.

  On the other hand, the PC 13 receives data 1, generates get 2 from data 1, and transmits it to the WEB server 11. When the information storage server 30 receives this get2, it compares it with the stored request data and prefetch request data. Here, since the prefetch get2 is accumulated, the information accumulation server 30 determines that get2 = prefetch get2, and transmits the corresponding data2 to the PC 13. Note that when get 2 ≠ prefetch get 2, or when request data requesting the same WEB information as that of get 2 is not accumulated, the information accumulation server 30 transfers get 2 to the WEB server 11 in the same manner as get 1.

FIG. 6 shows a configuration example of a conventional prefetch proxy server 20.
In FIG. 6, the network interface unit 21 distributes the received signal to the request data receiving unit 22 or the WEB information analyzing unit 26 according to the transmission source and destination of the received signal. The request data receiving unit 22 receives a signal transferred from the PC 13 to the WEB server 11, extracts request data from the received signal, and outputs the request data to the request data comparing unit 23.

  The request data comparison unit 23 compares the request data extracted by the request data reception unit 22 with the request data stored in the request data storage unit 24, and the request data extracted by the request data reception unit 22 is the request data. If the data is not stored in the storage unit 24 (get1), the request data is output to the request data transmission unit 25 and stored in the request data storage unit 24. When the request data extracted by the request data receiving unit 22 is stored in the request data storage unit 24, the request data is discarded and the request data stored in the request data storage unit 24 is also deleted. To do.

  The request data transmission unit 25 transfers the request data input from the request data comparison unit 23 to the WEB server 11 via the network interface unit 21.

  The WEB information analysis unit 26 receives the WEB information sent from the WEB server 11 according to the request data, generates request data (prefetch get2) that is predicted to be requested by the PC 13 that receives the WEB information, and prefetch request data. Output to the comparison unit 27. On the other hand, the WEB information is transferred from the prefetch proxy server 20 to the information storage server 30 and further transferred to the PC 13.

  The prefetch request data comparison unit 27 compares the prefetch request data (prefetch get2) generated by the WEB information analysis unit 26 with the request data stored in the request data storage unit 24, and is extracted by the WEB information analysis unit 26. If the prefetch request data is not stored in the request data storage unit 24, the prefetch request data is output to the request data transmission unit 25 and stored in the request data storage unit 24. When the prefetch request data extracted by the WEB information analysis unit 26 is stored in the request data storage unit 24, the prefetch request data is discarded and the request data stored in the request data storage unit 24. Also delete.

  The request data sending unit 25 sends the prefetch request data (prefetch get 2) input from the prefetch request data comparison unit 27 to the WEB server 11 and the information storage server 30 via the network interface unit 21.

FIG. 7 shows a configuration example of a conventional information storage server 30.
In FIG. 7, the network interface unit 31 distributes the received signal to the request data receiving unit 32, the WEB information storage unit 36, or the prefetch request data receiving unit 37 according to the transmission source and destination of the received signal. The request data receiving unit 32 receives a signal transferred from the PC 13 to the WEB server 11, extracts the request data, and outputs the request data to the request data comparison unit 33.

  The request data comparison unit 33 compares the request data extracted by the request data reception unit 32 with the request data and the prefetch request data stored in the request data storage unit 34, and requests data or prefetch that requests the same WEB information. When the request data is not stored in the request data storage unit 34 (in the case of get 1), the request data is output to the request data transmission unit 35 and stored in the request data storage unit 34. Further, when request data or prefetch request data requesting the same WEB information as the request data extracted by the request data receiving unit 32 is stored in the request data storage unit 34 (in the case of get2), the request data is The request data or the prefetch request data stored in the request data storage unit 34 is deleted and discarded, and the WEB information storage unit 36 is instructed to output the WEB information (data2) to the PC 13. .

  The request data transmission unit 35 transfers the request data input from the request data comparison unit 33 to the WEB server 11 via the network interface unit 31.

  The prefetch request data receiving unit 37 receives prefetch request data (prefetch get 2) transmitted from the prefetch proxy server 20 to the information storage server 30 together with the WEB server 11, and accumulates it in the request data accumulation unit 34.

  The WEB information storage unit 36 receives the WEB information (data1) transmitted from the WEB server 11 to the PC 13 according to the request data (get1) from the PC 13 or according to the prefetch request data (prefetch get2) from the prefetch proxy server 20. , Data2) are received and stored. Further, it inquires whether or not the request data corresponding to the WEB information is stored in the request data storage unit 34, and outputs the WEB information (data 1) in which the request data is stored to the WEB information transmission unit 38. The WEB information storage unit 36 outputs WEB information (data2) corresponding to the prefetch request data (prefetch get2) to the WEB information transmission unit 38 in accordance with an instruction from the request data comparison unit 33.

  The WEB information transmission unit 38 transmits the WEB information input from the WEB information storage unit 36 to the PC 13 via the network interface unit 31.

JP 2011-039899 A

  In the transfer from the prefetching proxy server to the information storage server, the TCP protocol is generally used, and the slow start congestion control mechanism and the retransmission control mechanism perform highly reliable transmission without causing packet loss. . However, when the transmission delay time of the transmission path between the prefetching proxy server and the information storage server is large, when transferring by the TCP protocol, there is a problem that the transmission efficiency becomes low due to the slow start congestion control and the transmission takes time. is there.

  Here, a case will be described in which WEB content such as an image having a small size of about 10 kbytes, which is a feature of the WWW service, is transferred via a long delay network. That is, the throughput for the data size to be transferred is numerically quantified. HTTP is an application transferred by a TCP session corresponding to each WEB content. FIG. 8 shows a state where data is transmitted from the WEB server to the PC in one TCP session. As described above, in TCP, it may be considered that data can be transmitted in bursts in one RTT (round trip delay time).

The data size Ds (k) [Byte] that can be transmitted at once from the WEB server at the time of k-th data transmission is
Ds (k) = Min {cwnd (k), Rwin} (1)
It is. Here, cwnd (k) is the congestion window on the transmitting side, the unit is Byte, and Rwin is the window size on the receiving side, and the unit is Byte. cwnd (k) can be expressed as:
・ Slow start phase
cwnd (k) = 2 ^(k-1) xcwnd (1) (cwnd (k) <ssthresh)… (2)
cwnd (1) = Min {MSS × int (Rwin / MSS), Rwin}
・ Congestion avoidance phase
cwnd (k) = cwnd (k-1) × MSS (cwnd (k) ≧ ssthresh) (3)

  Here, the maximum value of Ds (k) is Rwin. MSS (maximum segment size) is the maximum length of data that can be transferred in one segment in TCP, and is 1460 bytes in Ethernet (registered trademark). Here, it is assumed that the data to be transferred is segmented for each MSS. ssthresh is a threshold value for shifting from the slow start to the congestion avoidance phase, and may be considered as a value of 1/2 of cwnd at the time of packet loss, that is, MSS × int (Rwin / MSS) when there is no packet loss. For example, when RTT = 0.25 seconds, the time variation of each Ds (k) at Rwin = 64 kByte, 32 kByte, and 17 kByte is shown in FIG.

The value of Ds (k) increases exponentially from the start of communication and reaches half of Rwin. After that, it increases by 1MSS every 1RTT, and reaches its peak when it reaches the value of Rwin. Therefore, since data of the size Ds (k) is sent in the 1st RTT time of the kth time, the maximum value Max [Sd] of the data size Sd that can be transferred in the time of RTT × n [seconds] from the start of transfer is

となる。したがって、転送するデータサイズに対するスループットＳは

と表すことができる。これをグラフ化したものを図１０に示す。 Further, the minimum value Min [Sd] of Sd is for transmitting data (1MSS) that could not be transmitted n-1 times at the nth time.

It becomes. Therefore, the throughput S for the data size to be transferred is

It can be expressed as. A graph of this is shown in FIG.

  When the data size is small like WEB content of about 10 kByte, the transfer is completed in the slow start phase, the throughput is low, and it can be seen that the throughput cannot be improved so much even if the value of Rwin is increased. Considering the feature that the data size of the WEB content is small in the WEB service, it can be seen that the HTTP throughput is not so much different even when Rwin is as large as 64 kbytes or when Rwin is as small as 17 kbytes, and is low speed. As described above, in order to transfer WEB contents using a TCP protocol via a network with a large delay, there is a problem that the throughput is low due to a through start that is a congestion control mechanism for improving reliability.

  The present invention establishes a TCP connection and a UDP connection between a prefetching proxy server and an information storage server as a set, and selects TCP protocol and UDP protocol as appropriate when transferring prefetched WEB information to increase transmission efficiency. It is an object of the present invention to provide a WEB information acquisition method and a prefetching proxy server that can be used.

  In the first invention, a WEB server, a prefetching proxy server, an information storage server, and a WEB browsing apparatus are installed via a plurality of network systems, and the WEB browsing apparatus transmits the first request data to the WEB server, The server transmits the WEB information corresponding to the first request data to the WEB browsing apparatus, and the prefetch proxy server transfers the WEB information corresponding to the first request data to the information storage server and also includes the WEB information. The request data included is extracted and transmitted to the WEB server as prefetch request data. Further, the prefetch request data is notified to the information storage server, and the WEB server sends the WEB information corresponding to the prefetch request data to the prefetch proxy server. The prefetch proxy server sends the WEB information corresponding to the received prefetch request data to the information storage server. Then, the WEB information is stored in the information storage server, and the WEB browsing apparatus generates second request data included in the WEB information corresponding to the first request data, and stores the second request data as information. When the prefetch request data and the second request data are the same, the information storage server transmits the web information corresponding to the stored prefetch request data to the web browsing device. The proxy server transmits WEB information corresponding to the prefetch request data to the information storage server using the TCP protocol when the transmission delay time between the proxy server and the information storage server is a predetermined time or less. When the transmission delay time with the server exceeds a certain time, the WEB information corresponding to the prefetch request data is stored using the UDP protocol. And transmits it to the server.

  In the WEB information acquisition method of the first invention, the prefetching proxy server adds a sequence number to the packet to be transmitted when transmitting the WEB information corresponding to the prefetching request data to the information storage server using the UDP protocol, The accumulation server transmits a retransmission request notifying the sequence number missing from the sequence number added to the received packet to the prefetch proxy server, and the prefetch proxy server transmits the packet of the sequence number requested to be retransmitted from the information accumulation server. Retransmit using TCP protocol.

  In the second invention, a WEB server, a prefetching proxy server, an information storage server, and a WEB browsing apparatus are installed via a plurality of network systems, and the WEB browsing apparatus transmits the first request data to the WEB server, The server transmits the WEB information corresponding to the first request data to the WEB browsing apparatus, and the prefetch proxy server transfers the WEB information corresponding to the first request data to the information storage server and also includes the WEB information. The request data included is extracted and transmitted to the WEB server as prefetch request data. Further, the prefetch request data is notified to the information storage server, and the WEB server sends the WEB information corresponding to the prefetch request data to the prefetch proxy server. The prefetch proxy server sends the WEB information corresponding to the received prefetch request data to the information storage server. Then, the WEB information is stored in the information storage server, and the WEB browsing apparatus generates second request data included in the WEB information corresponding to the first request data, and stores the second request data as information. The information storage server transmits the WEB information corresponding to the stored prefetch request data to the WEB browsing device when the prefetch request data and the second request data are the same. The server sends a delay time measurement packet to the information storage server, measures the transmission delay time with the information storage server, and supports prefetch request data when the transmission delay time is less than a certain time WEB information to be transmitted is transmitted to the information storage server using the TCP protocol, and when the transmission delay time exceeds a predetermined time, the prefetch request data is supported. The EB information using the UDP protocol and transmitting means for transmitting to the information storage server.

  In the prefetch proxy server of the second invention, the transmission means adds a sequence number to the packet to be transmitted when transmitting the WEB information corresponding to the prefetch request data to the information storage server using the UDP protocol, and the information storage server Includes a retransmission control means for receiving a retransmission request for notifying a sequence number missing from the sequence number added to the received packet and retransmitting the packet of the sequence number requested for retransmission using the TCP protocol.

  The prefetching proxy server of the present invention periodically measures the transmission delay time with the information storage server, and when the measured transmission delay time is equal to or less than a predetermined time, the prefetched proxy server uses WEB information prefetched using the TCP protocol. Send to the information storage server. When the measured transmission delay time exceeds a certain time, the prefetched WEB information is transmitted to the information storage server using the UDP protocol incorporating the retransmission control and reception order control functions. Therefore, when the transmission delay is small, reliable transmission by TCP is performed, and when the transmission delay is large, transmission time can be reduced by highly efficient transmission by UDP.

  When receiving the WEB information prefetched by the UDP protocol, the information storage server transmits a retransmission request notifying the sequence number missing from the sequence number included in the packet to the prefetch proxy server. The prefetch proxy server retransmits the packet with the sequence number requested to be retransmitted using the TCP protocol. As a result, it is possible to recover packet loss caused during transmission with high efficiency by UDP. Further, by transmitting only the retransmission packet by TCP, it is less susceptible to the slow start, and the retransmission packet can be transferred with high reliability. Further, when the order of the sequence numbers of the received UDP packets is reversed, the order of the packets is rearranged so that the order is not reversed.

  As described above, by combining the switching of the TCP protocol / UDP protocol and the retransmission control / packet order control, it is possible to improve the transmission efficiency of the entire network and perform highly reliable information transfer.

It is a figure which shows the structure of Example 1 of the prefetching proxy server of this invention. It is a figure which shows the structure of Example 2 of the prefetching proxy server of this invention. FIG. 10 is a diagram illustrating an example of a WEB information transfer processing sequence corresponding to the first embodiment and the second embodiment. It is a figure which shows the structural example of the communication network containing the conventional WEB information acquisition apparatus. It is a figure which shows the conventional WEB information acquisition process sequence. It is a figure which shows the structural example of the conventional prefetching proxy server. It is a figure which shows the structural example of the conventional information storage server 30. FIG. It is a figure which shows the data transfer sequence in TCP. It is a figure which shows the time change of the transmission data size of a prefetch proxy server. It is a figure which shows the transfer throughput with respect to data size.

  In the prefetch proxy server, the TCP protocol and the UDP protocol are appropriately selected according to the transmission delay time between the information storage server and the web information corresponding to the prefetch request data (hereinafter referred to as “prefetch web information”). And transferring to the information storage server.

  Here, since the UDP protocol is connectionless communication and does not have a slow start congestion control mechanism, it can be transferred at a higher speed than when the TCP protocol is used. As a result, it is possible to shorten the time for transferring the prefetched WEB information from the prefetching proxy server to the information storage server. Furthermore, the transfer time of the WEB information from the information storage server to the PC is shortened, and the effect of prefetching can be enhanced. However, since the UDP protocol is connectionless communication, reliability is low, packet loss may occur in the middle of the network, or the order of packet reception may be reversed in the information storage server, and the WEB information may not be received correctly. . Retransmission processing is required for missing received packets at the information storage server, and reception order control processing is required for reversal of the reception order. Therefore, in the present invention, as shown in the following first and second embodiments, the UDP protocol and the TCP protocol are selectively used.

  In the first embodiment of the present invention, when the prefetching proxy server transfers the prefetching WEB information to the information storage server, the protocol is switched based on the measured value of the transmission delay time between the prefetching proxy server and the information storage server.

  The prefetch proxy server and the information storage server establish a UDP connection and a TCP connection as a set prior to the transfer of the WEB information. The prefetch proxy server periodically sends a delay time measurement packet to the information storage server, measures the transmission delay time from the round trip time of the packet, and transfers the prefetch WEB information to the information storage server. The UDP protocol is used when the transmission delay time with the storage server exceeds the threshold value, and the TCP protocol is used when the transmission delay time is less than the threshold value.

FIG. 1 shows the configuration of Embodiment 1 of the prefetching proxy server of the present invention.
The correspondence relationship between the prefetching proxy server of the first embodiment shown in FIG. 1 and the conventional prefetching proxy server shown in FIG. 6 is as follows. The network interface unit 21 corresponds as it is. The reception signal type determination / transfer processing unit 1, the transfer signal protocol determination unit 2, and the delay time measurement unit 3 shown in FIG. 1 are functional units newly provided in the WEB information analysis unit 26 of FIG. The prefetch function unit 4 shown in FIG. 1 corresponds to the prefetch request data comparison unit 27 and the request data transmission unit 25 of FIG. The other functional units shown in FIG. 6 are omitted in the first embodiment shown in FIG.

  When the prefetch proxy server of the first embodiment receives the request data (get) transmitted from the PC to the WEB server and the WEB information (data) transmitted from the WEB server to the PC in response to the request data, a new connection is generated. The TCP connection and the UDP connection corresponding to the connection are established with the information storage server. Then, the delay time characteristic unit 3 of the prefetching proxy server transmits the delay time measurement packet to the information storage server periodically or with reception of the prefetching WEB information as a trigger for starting transfer, and the round trip time of the packet. Measure and hold the transmission delay time.

  The network interface unit 21 distributes the received signal to the request data receiving unit 22 or the WEB information analyzing unit 26 shown in FIG. 6 according to the transmission source and destination of the received signal, and the WEB information analyzing unit 26 responds to the request data. The WEB information sent from the WEB server 11 is received. Here, if the received WEB information is an HTML signal, the received signal type determination / transfer processing unit 1 of the WEB information analysis unit 26 outputs the WEB information to the prefetch function unit 4 and performs prefetch processing. Regarding the prefetching process, prefetching request data is generated based on the configuration described with reference to FIG. 6 and is sent to the WEB server, but detailed description thereof is omitted here.

  Further, the reception signal type determination / transfer processing unit 1 determines whether the received WEB information is WEB information (the same data1, in this example, an HTML signal) corresponding to the request data (get1 in FIG. 5) from the PC, or a prefetch proxy server It is determined whether the prefetching WEB information (same data2) corresponding to the prefetching request data (same prefetching get2). Then, the former HTML signal WEB information (same data 1) is transferred as it is to the information storage server, and in the latter prefetch WEB information (same data 2), the transfer signal protocol determination unit 2 is informed of the transfer signal protocol. An inquiry is made, the transfer signal protocol determined by the transfer signal protocol determination unit 2 is acquired, and the process of transferring to the information storage server is performed accordingly.

  Here, the transfer signal protocol determination unit 2 receives the inquiry about the transfer signal protocol from the reception signal type determination / transfer processing unit 1 and inquires the delay time measurement unit 3 about the delay time with the information storage server. In response to the inquiry, the delay time measurement unit 3 notifies the transfer signal protocol determination unit 2 of the measurement result of the transmission delay time with the information storage server. The transfer signal protocol determination unit 2 acquires the transmission delay time with the information storage server, and determines that the UDP protocol is used if the transmission delay time exceeds a predetermined threshold, and the TCP protocol is used if the transmission delay time is less than the threshold. The received signal type determination / transfer processing unit 1 is notified of the determined transfer signal protocol.

  The information storage server corresponding to the prefetching proxy server of the first embodiment includes a functional unit used for measuring the transmission delay time between the prefetching proxy server and the information storage server with the delay time measuring unit 3 of the prefetching proxy server. Other than that, the configuration of the information storage server shown in FIG. 7 is the same.

  That is, for the WEB information input to the information storage server, the WEB information (same data1) corresponding to the request data from the PC (get1 in FIG. 5), or the prefetching corresponding to the prefetching request data (same prefetching get2) of the prefetching proxy server. It is determined whether it is WEB information (same data2). The former WEB information (same data1) is transferred to the PC as it is, and in the case of the latter prefetched WEB information (same data2), it is accumulated until the same request data as the prefetch request data (same prefetch get2) is input from the PC. When the request data is input, the prefetched WEB information (same data2) is transferred to the PC.

  Embodiment 2 of the present invention is characterized in that retransmission processing of a packet transferred by the UDP protocol is performed using the TCP protocol.

  The transmission delay increases as the number of retransmission packets increases. In other words, in a network with a large delay, it takes a long time to wait for a retransmission packet. Therefore, when a plurality of retransmissions occur, the transmission delay becomes significant. Therefore, in the second embodiment, a retransmission packet of a packet transferred by the UDP protocol is retransmitted using the TCP protocol. That is, the prefetching proxy server performs retransmission processing using a TCP connection for packet loss that occurs on the UDP connection. If only the retransmission process uses the TCP protocol, the amount of traffic is small. Therefore, even if the TCP protocol is partially used, it is not easily affected by the slow start described above. Further, it is not necessary to provide a new retransmission function on the UDP protocol, and a conventional TCP protocol design can be used.

FIG. 2 shows a configuration of a second embodiment of the prefetching proxy server according to the present invention.
The prefetching proxy server in FIG. 2 has a configuration in which a retransmission control unit 5 is connected to the received signal type determination / transfer processing unit 1 of the prefetching proxy server in FIG.

  When the reception signal type determination / transfer processing unit 1 transfers prefetched WEB information (data 2 in FIG. 5) to the information storage server, the UDP protocol, if the transmission delay time with the information storage server exceeds a threshold, If it is below the threshold, the TCP protocol is used. Here, when the prefetched WEB information is transferred by the UDP protocol, a UDP sequence number is added to the UDP packet.

  The information storage server includes a retransmission control unit that extracts a missing UDP sequence number from the received UDP packet and notifies the prefetch proxy server of retransmission. At this time, the information storage server transmits a retransmission control signal including a missing UDP sequence number necessary for retransmission using a TCP connection (SACK option) instead of a UDP connection.

  When the reception signal type determination / transfer processing unit 1 of the prefetching proxy server receives a retransmission control signal from the information storage server, it notifies the retransmission control unit 5 without making an inquiry about the transfer signal protocol to the transfer signal protocol determination unit 2. To do. The retransmission control unit 5 determines the missing UDP sequence number necessary for retransmission included in the retransmission control signal, and notifies the received signal type determination / transfer processing unit 1 to retransmit the packet using the TCP protocol. The received signal type determination / transfer processing unit 1 retransmits the packet using the TCP protocol.

  The information storage server corresponding to the prefetching proxy server according to the second embodiment includes a functional unit used for measuring a transmission delay time between the prefetching proxy server and the information storage server with the delay time measuring unit 3 of the prefetching proxy server. The configuration of the information storage server shown in FIG. 7 is the same as that of FIG.

FIG. 3 shows an example of a WEB information transfer processing sequence corresponding to the first embodiment and the second embodiment.
In FIG. 3, the prefetching proxy server sends a delay time measurement packet to the information storage server, and measures the transmission delay time with the information storage server. Here, since the transmission delay time is equal to or less than the threshold value, transfer using the TCP protocol is selected.

  The PC transmits request data (get1) to the WEB server, and the WEB server returns WEB information (data1, HTML signal in this example) corresponding thereto.

  The prefetch proxy server transfers the WEB information (data1) to the information storage server and analyzes the WEB information (data1) to generate prefetch request data (prefetch get2, prefetch get3). First, the prefetch request data (prefetch get2). ) Is transmitted to the WEB server, and a prefetch notification including prefetch request data is transmitted to the information storage server. The information storage server receives the prefetch notification transmitted from the prefetch proxy server, and waits for reception of prefetch web information (data2, data3) corresponding thereto.

  The WEB server transmits the prefetch web information (data2) corresponding to the prefetch request data (prefetch get2) to the PC. When the prefetching proxy server receives the prefetching WEB information (data2), the prefetching proxy server transmits the prefetching WEB information (data2) to the information storage server using the TCP protocol already selected in the transfer signal protocol determination unit. When receiving the prefetched WEB information (data2), the information storage server temporarily stores the request data (get2) corresponding to the prefetched WEB information (data2) since it has not been input from the PC.

  On the other hand, the PC receives the WEB information (data 1) and transmits the request data (get 2) to the WEB server. When the information storage server receives this request data (get2), it collates with the prefetch request data (prefetch get2) of the prefetch notification, and transmits the prefetched WEB information (data2) accumulated by the coincidence of both to the PC.

  Here, the prefetching proxy server sends a delay time measurement packet to the information storage server, and measures the transmission delay time with the information storage server. Here, since the transmission delay time exceeds the threshold value, transfer by the UDP protocol is selected.

  The prefetch proxy server continues to transmit prefetch request data (prefetch get3) included in the WEB information (data1) to the WEB server. The WEB server transmits prefetch WEB information (data3) corresponding to the prefetch request data (prefetch get3) to the PC. When the prefetching proxy server receives the prefetching WEB information (data3), the prefetching proxy server transmits the prefetching WEB information (data3) to the information storage server using the UDP protocol already selected in the transfer signal protocol determination unit. When the information storage server receives the prefetched WEB information (data3), the information storage server temporarily accumulates the prefetched WEB information (data3), and performs retransmission processing and order matching processing.

  Here, the information storage server detects a missing packet in the prefetched WEB information (data 3) transferred using the UDP protocol, and requests the prefetch proxy server to retransmit the missing packet. The prefetching proxy server that has received this retransmission request transfers the packet to be retransmitted to the information storage server using the TCP protocol. The information storage server performs order matching processing of prefetched WEB information (data3) corresponding to the prefetch request data (prefetch get3) including the retransmitted packet.

  On the other hand, the PC transmits the next request data (get3) to the WEB server according to the WEB information (data1). When the information storage server receives the request data (get3), the information storage server collates with the prefetch request data (prefetch get3) of the prefetch notification, and transmits the prefetched WEB information (data3) accumulated due to the match between the two.

DESCRIPTION OF SYMBOLS 1 Reception signal type determination / transfer processing part 2 Transfer signal protocol determination part 3 Delay time measurement part 4 Prefetch function part 5 Retransmission control part 11 WEB server 12 Internet 13 PC
14 LAN
DESCRIPTION OF SYMBOLS 15 High delay network system 20 Prefetching proxy server 21 Network interface part 22 Request data receiving part 23 Request data comparison part 24 Request data storage part 25 Request data transmission part 26 WEB information analysis part 27 Prefetch request data comparison part 30 Information storage server 31 Network Interface unit 32 Request data reception unit 33 Request data comparison unit 34 Request data storage unit 35 Request data transmission unit 36 WEB information storage unit 37 Prefetch request data reception unit 38 WEB information transmission unit

Claims (4)

A WEB server, a prefetching proxy server, an information storage server, and a WEB browsing device are installed via a plurality of network systems,
The WEB browsing device transmits first request data to the WEB server, the WEB server transmits WEB information corresponding to the first request data to the WEB browsing device,
The prefetch proxy server transfers WEB information corresponding to the first request data to the information storage server, extracts request data included in the WEB information, and transmits the request data as prefetch request data to the WEB server. In addition, the information storage server is notified of the prefetch request data,
The WEB server transmits WEB information corresponding to the prefetch request data to the prefetch proxy server,
The prefetch proxy server transmits WEB information corresponding to the received prefetch request data to the information accumulation server, and accumulates the WEB information in the information accumulation server,
The WEB browsing device generates second request data included in WEB information corresponding to the first request data, transmits the second request data to the information storage server,
In the WEB information acquisition method of transmitting the WEB information corresponding to the stored prefetch request data to the WEB browsing device when the prefetch request data and the second request data are the same,
The prefetch proxy server, when a transmission delay time with the information storage server is a predetermined time or less, transmits WEB information corresponding to the prefetch request data to the information storage server using a TCP protocol,
The prefetch proxy server transmits WEB information corresponding to the prefetch request data to the information storage server using a UDP protocol when a transmission delay time with the information storage server exceeds a predetermined time. WEB information acquisition method. In the WEB information acquisition method according to claim 1,
The prefetch proxy server adds a sequence number to a packet to be transmitted when transmitting WEB information corresponding to the prefetch request data to the information storage server using a UDP protocol.
The information storage server sends a retransmission request notifying the sequence number missing from the sequence number added to the received packet to the prefetch proxy server,
The WEB information acquisition method, wherein the prefetch proxy server retransmits a packet having a sequence number requested to be retransmitted from the information storage server using a TCP protocol. A WEB server, a prefetching proxy server, an information storage server, and a WEB browsing device are installed via a plurality of network systems,
The WEB browsing device transmits first request data to the WEB server, the WEB server transmits WEB information corresponding to the first request data to the WEB browsing device,
The prefetch proxy server transfers WEB information corresponding to the first request data to the information storage server, extracts request data included in the WEB information, and transmits the request data as prefetch request data to the WEB server. In addition, the information storage server is notified of the prefetch request data,
The WEB server transmits WEB information corresponding to the prefetch request data to the prefetch proxy server,
The prefetch proxy server transmits WEB information corresponding to the received prefetch request data to the information accumulation server, and accumulates the WEB information in the information accumulation server,
The WEB browsing device generates second request data included in WEB information corresponding to the first request data, transmits the second request data to the information storage server,
The information storage server, when the prefetch request data and the second request data are the same, the prefetch proxy of the web information acquisition device that transmits the web information corresponding to the stored prefetch request data to the web browsing device On the server,
A measuring means for sending a delay time measurement packet to the information storage server and measuring a transmission delay time with the information storage server;
When the transmission delay time is a predetermined time or less, WEB information corresponding to the prefetch request data is transmitted to the information storage server using a TCP protocol, and when the transmission delay time exceeds a predetermined time, the prefetch request Transmitting means for transmitting WEB information corresponding to data to the information storage server using a UDP protocol. In the prefetch proxy server according to claim 3,
The transmission means adds a sequence number to a packet to be transmitted and adds it to a packet received by the information storage server when transmitting WEB information corresponding to the prefetch request data to the information storage server using a UDP protocol. A prefetching proxy server, comprising: a retransmission control means for receiving a retransmission request for notifying a sequence number missing from the received sequence number, and further retransmitting the packet of the sequence number requested for retransmission using the TCP protocol.

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