JP2000253054A - Data delivery system and data delivery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data delivery system where calculation of a check sum in the case of generating a packet is conducted at a high speed and a packet is generated at a high speed even when a packet transfer unit differs for each occasion of data delivery. SOLUTION: A data delivery method is employed for a data delivery system where a check code is written in each packet when data are assembled into the packet and delivered. In the case of receiving a data delivery request from a client, it is examined whether or not a check code calculated for each packet transfer unit depending on the client is stored in a temporary storage section 22 with respect to the data, and when not stored, the check code for the data for each unit of transferred packets is calculated and stored in the temporary storage section 22, the data are divided to generate packets and the check code to be written to each packet is calculated by utilizing the check code for each packet transfer unit with respect to the data that have already been calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data delivery system and a data delivery method for delivering electronic information.

[0002]

2. Description of the Related Art In recent years, with the explosive expansion and spread of the Internet, an open environment and a group of tools built thereon have attracted attention in building an information system in a company. In recent years, applying the technique cultivated on the Internet to information systems in a company has been called an intranet. In the intranet, W
Attempts have been made to build an information sharing system centered on eb, and to integrate it into a database system or existing backbone system.

[0003] Further, as a trend that is currently attracting attention, as a reflection of the complexity of management and the high management cost of systems centered on PCs, the management is concentrated and the role sharing with the user terminal is reviewed. Network computing has been proposed.

In such a situation, the role of a server in an intranet has become more and more important. At present, the performance of the server as a server is inferior to the high-speed CPU power, and it seems that it cannot meet future demands. Therefore, a high-speed WWW server capable of transmitting and receiving a large amount of data at high speed and quickly responding to various requests is expected.

A conventional data delivery system including a WWW server will be described below with reference to the drawings.

In the data delivery in the data delivery system, upon receiving a data delivery request from a client, a connection is established with the client, and the requested data is delivered as a packet to the network. A packet delivered to the network is composed of a “packet header” and “packet data”. The packet data is requested data (content), and the content does not depend on the connection. On the other hand, the content of the packet header differs for each connection. If the size of the requested data is larger than the maximum segment size that can be sent to the network (hereinafter abbreviated as MSS), the data is divided by the MSS and delivered to the network as a plurality of packets. I do.

FIG. 12 shows a packet delivered to the Ethernet as an example of the packet. (A) is data to be delivered, and (b) is a packet obtained by dividing the data of (a) by the MSS. Each packet is an Ethernet (Ethernet) header, an IP header, a TCP header, and one of the blocks obtained by dividing the data by the MSS (when the last block is less than the MSS due to the relationship between the original data length and the MSS value). ), And a CRC. FIG. 12 illustrates a case where the data link layer is Ethernet as an example. However, when the data link layer is other than Ethernet, only the corresponding part is changed.

Here, some protocols for packet communication are designed to write a check code for the packet in the packet header. For example, when the TCP protocol is used, the TCP header includes a check code for the TCP packet. FIG.
In the case of 2 (b), in the packet including the portion of the first data (1) in the data of FIG. 12A, the TCP header (the portion excluding the area where the check code itself is described) and the portion of the data (1) are included. Is calculated, and its value is described in the check code area of the TCP header.

[0009] Such a check code is called a checksum. The checksum is, for example, a "1's complement sum" of the TCP header and its data portion for every 16 bits (in this case, the checksum is 16 bits).

To describe the above in more detail, in the calculation of the checksum, the calculation is performed by filling "0" in the area (checksum area) describing the check code itself. Strictly speaking, to calculate the checksum,
Add a pseudo-header. TCP adds a pseudo-header before the TCP packet and if the total length is 1
If it is not a multiple of 6 bits, a byte consisting of only zeros is appended to its end to pad the packet so that the overall length is a multiple of 16 bits, and the entire checksum is calculated. However, the bytes used for padding and the pseudo header are not transmitted together with the TCP packet. These are used only to calculate the checksum. In order to calculate the checksum, first, "0" is filled in the checksum field (the area describing the check code itself), and a 16-bit 1 bit including a pseudo header, a TCP header, and data is filled.
Compute the complement of.

FIG. 13 shows a configuration example of a conventional data delivery system.

The data to be transmitted is stored in the data storage device 10.
1 is stored. The data transmitting device 102 converts the data read from the data storage device 101 into a packet and transmits the packet over the packet switching network 103.

That is, the data stored in the data storage device 101 is equal to the capacity of the transmission buffer 125.
Once copied to the transmission buffer 125. The protocol processing unit 123 establishes a connection with the client and cuts out data of a length that can be transmitted at a time from the transmission buffer 125. Furthermore, create a TCP header,
This TCP header is added to the head of the data cut out earlier to form a TCP packet. Also, a checksum for the entire TCP packet is calculated and written in the checksum area of the TCP header. Further, an IP header is created to configure an IP packet. Packet transmission unit 12
4 sends the packet constructed as described above to the packet switching network 103.

However, in such a conventional data delivery system, after receiving a request from the client and extracting the corresponding data from the data storage device, the checksum is calculated to form a packet. There was a problem.

In this regard, Japanese Patent Application Laid-Open No. Hei 6-69957 uses the following method to speed up packet generation processing, particularly, checksum calculation. First, data to be transmitted is divided into a plurality of packets by the MSS, a checksum for each divided data is calculated, and the divided data and a checksum for the data are stored in a data storage device in the form of a packet to be sent to the network. Keep it. At that time, the data is written to the data area,
The checksum is written to the checksum area of the header as a temporary checksum. FIG. 14 shows a state of a packet stored in the data storage device (201). In FIG. 14, P1 to P3 are packets, H1 to H3 are packet header areas, and D1 to D3 are packet data areas. As described above, the checksum area of the header (for example, H1) contains data for data (for example, D1). Checksum is written temporarily. When a data delivery request is received from a client, a packet corresponding to the requested data is retrieved from the data storage device, a packet header is created, a checksum for the entire packet is obtained using a temporary checksum, and the packet is checked. Overwrite the sum area and deliver the packet to the network.

[0016]

However, Japanese Patent Laid-Open No. 6-6 / 1994
In a conventional data delivery system as disclosed in Japanese Patent Application Laid-Open No. 9957/1993, since data is divided in advance by the MSS to form a packet to be delivered to the network and stored in the data storage device, there are the following problems.

(1) Since the value of the MSS is fixed in advance, it is not possible to cope with a case where a packet is delivered by a different MSS. For example, it is not possible to cope with the case where the data delivery system has a plurality of network interfaces and the MSS of each network is different (in addition, it is necessary to generate and prepare all packets simply corresponding to all MSS for all contents) Is simply wasteful of memory and is not practical.) Also, for example, when a network having an MSS ′ smaller than the MSS of the network to which the data delivery system is directly connected via a network interface exists on a path between the data delivery system and the client, the data delivery system is fixed in advance. M
If the packet is transferred in units of packets divided by SS, the data will be divided in the middle of the route and the data will be finally reconstructed on the host, resulting in poor data transfer efficiency. Can not.

(2) Delivery of packets with different packet header sizes because the packet header area is fixed in advance, for example, when delivering both IPv4 compliant packets and IPv6 compliant packets I can't handle it.

(3) Since it is assumed that data whose contents are invariable is delivered, for example, an HTTP header and an HTTP
It is not possible to handle a case where data including a portion (for example, an HTTP header) whose content changes each time is handled, such as a case where HTTP data including a body is carried in a TCP packet.

The present invention has been made in view of the above circumstances, and in each case of data delivery, even when the MSS may be different, the calculation of a check code at the time of packet generation and the speed of packet generation are accelerated. It is an object of the present invention to provide a data delivery system and a data delivery method that enable the above.

Also, the present invention provides a data delivery system capable of speeding up the calculation of a check code and generating a packet at the time of packet generation even when the packet header format may be different each time data is delivered. And a data delivery method.

Further, the present invention enables a high-speed calculation of a check code and a high-speed packet generation at the time of packet generation even when data including a portion whose contents change every time data is transmitted. It is an object to provide a data delivery system and a data delivery method.

[0023]

Means for Solving the Problems The present invention (claim 1) provides:
A data delivery system for writing a check code for each packet when packetizing and delivering data, comprising a plurality of data and a check code calculated for each packet transfer unit for certain data. A storage unit for storing, and a packet generated by dividing the data to be delivered stored in the storage unit, and a check code in a packet transfer unit corresponding to the data is stored in the storage unit. If it is stored, processing means for calculating a check code to be written in each packet using the stored check code is provided.

In the present invention, data is not stored in the form of a packet to be delivered to the network, but a packet is generated when the data is delivered. That is, the data is not divided in advance, and the data is divided when the data is delivered. On the other hand, when the check code calculated for each packet transfer unit for a certain data is obtained (the case where the check code is calculated as needed and the case where the check code is calculated in preparation for a request from a client) This is at least temporarily memorized. When generating a packet, if a check code for the data in the corresponding packet transfer unit is stored, a check code to be written in each packet is calculated using the stored calculated check code. I do.

According to the present invention, when the packet transfer unit can be different every time data is delivered, for example, the MSS
Has a plurality of network interfaces different from each other, and the MSS of the corresponding network is used as a packet transfer unit, it is possible to calculate and store a check code for each packet transfer unit (MSS) of data to be delivered in advance. , Calculation of a check code at the time of packet generation, and the speed of the packet generation can be increased. Further, when the MSS on the path with the client to which the connection is established is smaller than the MSS of the connected network, even if the minimum MSS is used as the packet transfer unit, once the MSS on the bus is used. By calculating and storing the check code, the calculation of the check code at the time of packet generation and the speed of the packet generation can be increased. In addition, since data is handled independently of the header, even when a packet having a different header size is delivered, calculation of a check code at the time of packet generation and generation of the packet can be speeded up.

Preferably, when the storage unit does not store a check code for the data to be delivered in a corresponding packet transfer unit, a check code for the corresponding packet transfer unit for the data is calculated. Means may be further provided. By storing the check code obtained in this way, it can be reused at the time of subsequent data distribution.

Preferably, the processing means generates a packet by adding a packet header to each block obtained by dividing the data in the packet transfer unit, and calculates a packet for each block included in the packet. A check code for the packet may be calculated from the check code and the packet header, and the calculated check code may be written in a predetermined area of the packet header. For example, the packet is a TCP packet, and the check code is calculated for a corresponding block that is a TCP packet header and TCP packet data, and is described in a predetermined area of the TCP packet header. At this time, if the check code for the corresponding block portion which is the TCP packet data has been calculated, the check code may be calculated from the check code and the TCP packet header portion, and the calculation of the check code for the packet is accelerated. it can.

Preferably, the storage means includes a first storage means which can be accessed at a higher speed and a second storage means having a larger capacity, and the first storage means has at least:
This is for temporarily storing the delivered data and a check code for each packet transfer unit at the time of the delivery of the data, with a fixed storage capacity as an upper limit, and the second storage means includes at least It may be configured to store data to be delivered. Preferably, the first and second storage means do not store a check code based on a corresponding packet transfer unit with respect to the data to be delivered, and When the check code is calculated, the calculated check code may be stored in the first storage unit. Preferably, when overwriting a predetermined storage area of the first storage means, a check code for data to be deleted from the first storage means due to the overwriting is written in the second storage means. You may make it write back to a means. As described above, by caching data and check codes for data in a faster memory, check codes for packets can be calculated more quickly. Also, by storing the check code for the data in a larger capacity memory, the calculation of the check code for the data can be omitted.

[0029] Preferably, the check code is for checking the integrity of the contents of the packet to which it is written. Preferably, the check code may be one that can be calculated sequentially. For example, the check code is a checksum described in a TCP packet in the TCP protocol.

Preferably, the packet transfer unit is set to a value equal to a maximum segment size that can be sent to a network connected to a client that has requested data delivery among networks directly connected to the own system. Good. Preferably, the packet transfer unit may have a value equal to the smallest one of the maximum segment sizes that can be transmitted to each network existing between the own system and the client.

Preferably, when data consisting of a first data portion whose contents can change and a second data portion whose contents do not change is to be delivered, the first data portion and the second data portion
The packet may be generated so that the data portion of the second data portion is mounted on a different packet, and the process related to the check code for the data may be performed only on the second data portion. Preferably, the data to be delivered is
In the case where a check code is composed of a first data portion where a check code is not calculated and a second data portion where a check code is stored in the storage means, the first data portion and the second data portion And a check code for the packet including the second data portion may be calculated by using the stored check code. Preferably, the first data portion may be an HTTP header and the second data portion may be an HTTP body. According to the above, the data (for example, the HTTP header) for which the check code has not been calculated or whose contents can be changed and the data (for example, the HTTP body) for which the check codes have been calculated or whose contents are invariable in advance (for example, HTTP body) are Are handled independently so that they are included in different packets, so that when data that has not been subjected to check code calculation in advance and data that has been previously subjected to check code calculation for data are continuously delivered,
A check code for data calculated in advance can be used, and calculation of a check code and generation of a packet can be speeded up. This has great promise for speeding up a Web server that transmits HTTP data.

The present invention (claim 14) is a data delivery method of a data delivery system in which a check code for a packet is written in each packet when the data is packetized and delivered, wherein a client is requested to deliver data. At that time, it is checked whether the check code calculated for each packet transfer unit determined according to the client for the data is stored in the own system. The check code for each packet transfer unit is calculated, and the calculated check code is at least temporarily stored in the own system, and the data to be delivered is divided to generate a packet, and stored. A check code to be written in each packet using a check code for each packet transfer unit for the data. And calculating.

It should be noted that the present invention relating to the apparatus is also realized as an invention relating to a method, and the present invention relating to a method is also realized as an invention relating to an apparatus.

The present invention relating to an apparatus or a method is provided for causing a computer to execute a procedure corresponding to the present invention (or for causing a computer to function as means corresponding to the present invention, or for causing a computer to correspond to the present invention). The present invention is also realized as a computer-readable recording medium in which a program for realizing the function of performing the above is recorded.

[0035]

Embodiments of the present invention will be described below with reference to the drawings.

As described above, the maximum segment size that can be transmitted to a certain network is abbreviated as MSS.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
1 shows a configuration example of a data delivery system according to an embodiment.

This data delivery system comprises a data transmission device 2 for transmitting requested data to a client and a data storage device 1 for storing data to be delivered.
Its basic function is that the data transmission device 2 that has received a request for delivery of specified data (content) from the client stores the corresponding data (a copy of the data is temporarily stored in the data storage device 1) stored in the data storage device 1. If it is stored, the temporary storage is packetized and transmitted over the packet switching network 3.

The data storage device 1 is configured using, for example, a hard disk device or the like.

The data transmission device 2 is configured using, for example, a computer and a necessary network interface.

In this data delivery system, (1)
The data delivery system is directly connected to multiple networks (has multiple network interfaces),
When the MSS of each network is MSS1 to MSSN, a different one of the MSS1 to MSSN exists (however, the MSS of the network interface from which the data delivery request is sent is used.
MSS of a network other than the directly connected network is not considered or is not considered),
(2) In the data delivery system, one network or MSS is directly connected to a plurality of same networks (MSS1 =... = MSSN = MSSc). There may be another network (a network to which the data delivery system is indirectly connected), and there may be a network having an MSS ′ smaller than the MSSc among the other networks (the MSS ′).
In the case where a plurality of networks exist between the data delivery system and the client, packet generation is performed in consideration of the minimum MSS among the MSSs of the plurality of networks. (3) A case where the above (1) and (2) are combined, that is, as in the above (1), the data delivery system is directly connected to a plurality of networks, and Network MSS to M
When SS1 to MSSN are present, different ones exist among MSS1 to MSSN, and as described in (2) above, when a plurality of networks exist between the data delivery system and the client. Is not the only MSS to be used for processing, such as a case where packet generation is performed in consideration of the smallest MSS among the MSSs of the plurality of networks, and the MSS to be used for processing differs depending on the client. Can do so.

In the following, the “MSS on the path” refers to the MSS of one network when only one network exists between the client with which the connection has been established and the relevant data delivery system. When there are a plurality of networks and their MSSs are all the same, they are the same MSS. When there are a plurality of networks and there are different MSSs among them, a plurality of these MSSs are used. It is assumed that the MSS having the minimum value among the MSSs of the above.

As shown in FIG. 1, the data transmitting apparatus 2 includes a checksum calculating section 21 and a temporary storing section 2.
2, a protocol processing unit 23 and a packet transmission unit 24 are provided.

The checksum calculator 21 regards the requested data as a block for each MSS on the path and calculates a checksum for each block. If the size of the data is not divisible by the MSS, the final checksum calculated on the data will be for blocks of a size less than the MSS. The checksum calculated by the checksum calculation unit 21 is stored in the temporary storage unit 22 in association with the corresponding data.

The temporary storage unit 22 checks (a copy of) the data requested by the client among the data stored in the data storage device 1 and one or more types of MSS calculated for the data. This is for temporarily storing the sum. Since the temporary storage unit 22 usually has a limited storage capacity, if there is no new writing area, the temporary storage unit 22 is overwritten according to a predetermined rule. The predetermined rule includes, for example, a method of overwriting the oldest stored data and its checksum, a method of overwriting the data and its checksum that have been used for the longest time since the last use, There are various methods.

The protocol processing unit 23 establishes a connection with the client and generates a packet. The packet is generated in the order of a TCP packet and an IP packet. When generating a TCP packet, the data is packetized for each block divided by the MSS on the path, and the checksum for the TCP packet calculated by the checksum calculation unit 21 is used for each TCP packet. The checksum for the block and its TCP header (excluding the checksum area) is calculated.

To explain the above in more detail, in the calculation of the checksum, the calculation is performed by filling "0" in the area (checksum area) describing the check code itself. Strictly speaking, to calculate the checksum,
Add a pseudo-header. TCP adds a pseudo-header before the TCP packet and if the total length is 1
If it is not a multiple of 6 bits, a byte consisting of only zeros is appended to its end to pad the packet so that the overall length is a multiple of 16 bits, and the entire checksum is calculated. However, the bytes used for padding and the pseudo header are not transmitted together with the TCP packet. These are used only to calculate the checksum. In order to calculate the checksum, first, "0" is filled in the checksum field (the area describing the check code itself), and a 16-bit 1 bit including a pseudo header, a TCP header, and data is filled.
Compute the complement of.

The packet transmitting section 24 sends the packet constructed as described above to the packet switching network 3.

The MSS on the path to a certain client can be known in the procedure for establishing a connection with the client in the protocol processing unit 23, for example.

The calculation of the checksum for the data portion, its temporary storage, and the calculation of the checksum for the entire packet (header portion and data portion) will now be described with reference to FIG.

In FIG. 2, the length of the data requested from one client is 10,000 bytes, the MSS on the path for that client is 1,460 bytes, and the length of the data for another client requesting the same data is another byte. An example is shown in which the MSS on the path is 4,960 bytes.

MSS on the path to a client
Is 1,460 bytes, the checksum is sequentially calculated by the checksum calculator 21 in the data of 1,46 bytes.
It is calculated every 0 bytes and the last checksum is calculated for the remaining 1,240 bytes. The checksum for the block is calculated, for example, by dividing the block into 16 bits and sequentially taking "one's complement sum" for each 16 bit portion.

In this case, (the copy of) the data, the used MSS value 1,460, and the obtained seven checksum values are associated with each other and temporarily stored in the temporary storage unit 22.

In this case, the data is loaded on the packet for each block (1,460 bytes other than the last block / 1,240 bytes only for the last block), and the checksum corresponding to each block is Since the calculation has already been performed, the protocol processing unit 23 can calculate the checksum for the entire packet at high speed from the calculated checksum corresponding to the block to be loaded in the packet and the contents of the TCP header. The checksum for the entire packet is calculated by, for example, sequentially calculating the "1's complement sum" of the 16-bit calculated checksum and the 16 bits of the TCP header.

On the other hand, if the MSS on the path to another client is 4,960 bytes,
The checksum is calculated sequentially for every 4,960 bytes of data, and the last checksum is calculated for the remaining 80 bytes. In this case, (the copy of) the data, the used MSS value of 4,960, and the obtained three checksum values are temporarily stored in the temporary storage unit 22 in association with each other.

When the checksum for MSS = 1,460 bytes and the checksum for MSS = 4,960 bytes are calculated for data having a length of 10,000 bytes, the temporary storage unit 22 In this state, the data, the MSS value of 1,460 and the seven checksums at that time, and the MSS value of 4,960 and the three checksums at that time are stored. After that (while they exist in the temporary storage unit 22), the MS
If there is a request for the data from a client with S = 1,460 or MSS = 4,960,
The temporary storage unit 22 becomes available, and the calculation of the checksum for the data becomes unnecessary. Of course, it is not necessary to retrieve the data from the data storage device 1.

FIG. 3 shows an example of the format of the data and the checksum stored in the temporary storage unit 22. This example
Each data and its checksum are held in a link format. In FIG. 3, MS11 to MS13, MSn
1 to MSn2 are subsequent checksums 11 to 13, n
1 to n2 is the block size (ie, MS
S) indicates whether the checksum is for each. Here, an example in which a checksum area for data is dynamically secured has been described. However, an example in which an appropriate number / amount of MSS / checksum fields are allocated in advance and the checksum area is statically secured. Is also conceivable.

Next, the operation of the data delivery system of this embodiment will be described.

FIG. 4 shows an example of an operation procedure of the data delivery system of the present embodiment.

First, a data delivery request from the client to the data transmitting apparatus 2 through the packet switching network 3 (including information capable of specifying data specified by the client).
Is sent. First, the data transmission device 2 searches whether the requested data exists in the temporary storage unit 22 (step S11).

If the requested data does not exist in the temporary storage unit 22, a data request is sent to the data storage device 1 (step S12a). The checksum calculation unit 21 regards the data extracted from the data storage device 1 as a block sequence in MSS units on the path of the network to which the data delivery request has been made, and calculates a checksum for each block (step S13). ). The requested data and the calculated checksum are stored in the temporary storage unit 22 (step S14).

On the other hand, the requested data is stored in the temporary storage
And the checksum of the MSS on the corresponding path of the requested data exists in the temporary storage unit 22 (step S12b), the temporary storage unit 22 stores the checksum corresponding to the requested data and the MSS. The checksum to be taken out is taken out (step S15a).

The requested data is stored in the temporary storage unit 22.
However, if the checksum of the MSS on the corresponding path of the requested data does not exist in the temporary storage unit 22 (step S12b), the requested data is extracted from the temporary storage unit 22, and the checksum calculation unit 21 and calculates the checksum of the MSS on the corresponding path, and stores the calculated checksum in the temporary storage unit 22 (step S15b).

The protocol processing unit 23 transmits the data to the MS
Divide by S. Further, a TCP packet is generated. Then, a TCP packet header is created, a checksum for the entire packet is calculated using the TCP packet header and the calculated checksum, and a TCP packet is generated (step S16). Further, an IP header is created, and an IP packet is created (step S1).
7).

The packet transmitting unit 24 transmits the created IP packet to the packet switching network 3 (step S1).
8).

In the above description, the checksum by the MSS required when a data delivery request is made is calculated, and the data and the calculated checksum are stored in the temporary storage unit 22. In advance, the checksum for each MSS (and even the MSS on the expected path) of all or some of the network interfaces directly connected to the data delivery system is calculated for all or some of the data. , Data and the calculated checksum are stored in the data storage device 1,
When a data delivery request is made, if a checksum by the corresponding MSS is stored in the data storage device 1, a checksum for the entire packet is calculated using this checksum, and a packet is generated. The data and its checksum may be stored in the temporary storage unit 22. In this case, the formats of the data and the checksum stored in the data storage device 1 are the same as those in FIG. 3, for example. Alternatively, the checksum area may be statically reserved. Further, the data / checksum storage format of the data storage device 1 and the data / checksum storage format of the temporary storage unit 22 may be the same format or different formats.

In addition to the above, various variations of the present embodiment are conceivable.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
1 shows a configuration example of a data delivery system according to an embodiment.

This embodiment is different from the first embodiment in that when data is requested to be delivered to the data storage device 1 from a client in the past in addition to the data to be delivered. The point is that the calculated checksum for the MSS (on the path) is also stored.

The format of the data and the checksum stored in the data storage device 1 are the same as those in FIG. 3, for example. Alternatively, the checksum area may be statically reserved.

The data / checksum storage format of the data storage device 1 and the data / checksum storage format of the temporary storage unit 22 may be the same format or different formats.

Checksum calculation section 21 and temporary storage section 22
Are basically the same as those of the first embodiment.

The checksum calculated by the checksum calculation unit 21 is stored in the temporary storage unit 22 as in the first embodiment, but in the present embodiment, the data storage unit 1 is further stored at a predetermined timing. Is stored in The predetermined timing may be a point in time when the file is deleted from the temporary storage unit 22 (by being overwritten, for example), a point in time calculated by the checksum calculation unit 21, or the like. In the present embodiment, a description will be given as a point in time when the temporary storage unit 22 has been deleted by being overwritten.

In this embodiment, the data storage device 1
Is stored, the checksum calculation unit 21 does not perform the calculation, the checksum stored in the data storage device 1 is used for packet generation, and the checksum is stored in the temporary storage unit 22. Is stored.

The protocol processing unit 23 and the packet transmitting unit 2
The basic functions of the fourth embodiment are the same as those of the first embodiment. As described above, the checksum stored in the data storage device 1 may be used in the TCP packet generation processing of the protocol processing unit 23 in some cases.

Next, the operation of the data delivery system of the present embodiment will be described.

FIG. 6 shows an example of an operation procedure of the data delivery system of the present embodiment.

The main difference between this operation procedure and the procedure described in the first embodiment is that when the data in the temporary storage unit 22 is overwritten, the checksum for the overwritten data is written to the data storage device. (Therefore, the necessary checksum does not exist in the temporary storage unit 22,
The difference is that the data storage unit 1 sometimes exists.)

First, a data delivery request from the client to the data transmitting apparatus 2 through the packet switching network 3 (including information capable of specifying data specified by the client).
Is sent. The data transmission device 2 first searches whether the requested data exists in the temporary storage unit 22 (step S21).

If the requested data does not exist in the temporary storage unit 22, the requested data and its checksum request (data / checksum request) are sent to the data storage device 1. Then, it is checked whether there is an area for writing the requested data and its checksum in the temporary storage unit 22 (step S22).

If there is no area in the temporary storage unit 22 for writing the requested data and its checksum, the existing data and its checksum in the temporary storage unit 22 will be overwritten. Are written back to the data storage device 1 (step S23). At the time of this write-back, only the checksum for the MSS not stored in the data storage device 1 may be written back, or the entire checksum of the data stored in the data storage device 1 is discarded ( In some cases, no checksum of the data is stored in the data storage device 1), or the entire checksum of the data stored in the temporary storage unit 22 may be written back.

Subsequently, the requested data and all checksums for the requested data are stored in the temporary storage unit 22.
And overwrite (step S24).

On the other hand, if there is an area for writing the requested data and the checksum for the requested data in the temporary storage unit 22, the above write-back is unnecessary,
The requested data and all checksums for the requested data are brought to the temporary storage unit 22 (step S24).

In some cases, the data storage device 1 has not yet stored any checksum for the requested data. In this case, the requested data is brought to the temporary storage unit 22.

Although some checksums for the requested data are stored in the data storage device 1, the checksums corresponding to the MSS required in the current processing may not be stored. In this embodiment, in this case as well, the requested data and all checksums for the requested data are brought to the temporary storage unit 22.

If the requested data exists in the temporary storage unit 22 in step S21, the above processing is unnecessary.

Now, a state where at least the requested data exists in the temporary storage unit 22 is established.

Next, it is searched whether the checksum of the MSS on the corresponding path of the requested data exists in the temporary storage unit 22 (step S25).

The M of the requested data on the corresponding path
If the SS checksum exists in the temporary storage unit 22,
The requested data and its checksum are extracted from the temporary storage unit 22 (step S26a).

On the other hand, when the checksum of the MSS on the corresponding path of the requested data does not exist in the temporary storage unit 22, the requested data is extracted from the temporary storage unit 22, and the MSS on the corresponding path is checked. Calculate the sum,
The calculated checksum is stored in the temporary storage unit 22 (step S26b).

Subsequently, the protocol processing unit 23 divides the data by the MSS. Further, the protocol processing unit 23
Creates a TCP packet header, calculates a checksum for the entire packet using the TCP packet header and the calculated checksum, and generates a TCP packet (step S27). Further, an IP header is created, and an IP packet is created (step S28).

The packet transmitting unit 24 transmits the packet to the packet switching network 3 (Step S29).

In the above description, the checksum is stored in the data storage device 1 because, for example, the checksum calculated at least once for the data requested by the client and stored in the temporary storage unit 21 is stored in the data storage device 1. 1
In addition to this, when storing certain data in the data storage device 1, for example, when the data delivery system is directly connected, the MSS of all or some of the network interfaces directly connected to the data delivery system (further, A checksum for each expected MSS on the path may be calculated for the data, and the data and the calculated checksum may be stored in the data storage device 1 (partial data). It is also possible to calculate and store the checksum only for ().

Further, a configuration without the temporary storage unit 21 is also possible. In this case, the data may be written back to the data storage device 1 when the checksum is calculated.

In addition to the above, various variations of the present embodiment are conceivable.

(Third Embodiment) In this embodiment, when data composed of a data portion whose contents can change and a data portion whose contents do not change is to be delivered, a data portion whose contents can change, The data portion whose contents are not changed is mounted in a different packet. As a result, a checksum can be calculated in advance for a data portion whose content is unchanged.

That is, when a packet is generated from data including a data portion for which the checksum has not been calculated and a data portion for which the checksum has been calculated, the data portion for which the checksum has not been calculated and the data for which the checksum has been calculated are generated. The checksum calculation / packet generation can be accelerated by mounting the part in a different packet and calculating the checksum for the entire packet using the calculated checksum for the latter.

This configuration can be implemented independently, and therefore can be implemented in combination with the previous embodiments and the conventional configuration.

In the following, a case where this configuration is combined with the first embodiment will be described as an example.

FIG. 7 shows a configuration example of a data delivery system according to the present embodiment.

The main difference between the data delivery system of FIG. 7 and the data delivery system according to the first embodiment is that
The data transmission device 2 further includes an HTTP processing unit 25 that creates TP data (an HTTP header and an HTTP body) and transfers the created TP data to the protocol processing unit 23, and the checksum calculation unit 21 determines that the HTTP header and the HTTP body The checksum calculation is performed separately, and the protocol processing unit 23 mounts the HTTP header and the HTTP body in separate TCP packets.

Now, this data delivery system uses the Web
It functions as a server. Web server is W
web client and HTTP (Hypertext T)
and communicate with each other using a transfer protocol. The HTTP data communicated between the Web server and the client includes an HTTP header and an HTTP header.
Consists of a body. The HTTP header includes the type of data (content), the date and time of the request, the status of change of the requested data (content), and the like, and is determined at the time of data delivery.

The HTTP header has a T
Although it is carried not as the CP header but as a part of the TCP data, the content of the HTTP header is determined at the time of data delivery as described above, so that the checksum cannot be calculated in advance for the HTTP header (or other The checksum calculated at the time of transfer cannot be used.) On the other hand, since the HTTP body is composed of the requested data (contents), the checksum for the data constituting the HTTP body is unchanged and can be calculated in advance (if the MSS is the same,
The calculated checksum can be used for other transfers.) Therefore, in the present embodiment, the HTTP header and the HTTP body are placed in separate TCP packets, so that the calculated checksum can be used on the HTTP body side.

Hereinafter, the operation of the data delivery system illustrated in FIG. 7 will be described.

FIG. 8 shows an example of an operation procedure of the data delivery system.

First, a data delivery request from the client to the data transmitting apparatus 2 through the packet switching network 3 (including information capable of specifying data specified by the client).
Is sent. First, the data transmission device 2 searches whether the requested data exists in the temporary storage unit 22 (step S31).

If the requested data does not exist in the temporary storage unit 22, a data request is sent to the data storage device 1 (step S32a). The checksum calculation unit 21 regards the data retrieved from the data storage device 1 as a block sequence in MSS units on the path of the network to which the data delivery request has been made, and calculates a checksum for each block (step S33). The requested data and the calculated checksum are stored in the temporary storage unit 22 (step S34).

On the other hand, the requested data is stored in the temporary storage
And the checksum of the MSS on the corresponding path of the requested data exists in the temporary storage unit 22 (step S32b), the requested data and its checksum are extracted from the temporary storage unit 22. (Step S35a).

Further, the requested data is stored in the temporary storage unit 22.
However, if the checksum of the MSS on the corresponding path of the requested data does not exist in the temporary storage unit 22 (step S32b), the requested data is extracted from the temporary storage unit 22, and the checksum calculation unit 21 and calculates the checksum of the MSS on the corresponding path, and stores the calculated checksum in the temporary storage unit 22 (step S35b).

Subsequently, the HTTP processing unit 25 executes the HTTP
Create a header, make the data an HTTP body,
The P header and the HTTP body to the protocol processing unit 23
(Step S36).

First, the protocol processing unit 23 generates a TCP packet (step S37). What is important here is that the HTTP header and the HTTP body have different T
Generating a TCP packet so as to be included in the CP packet. That is, the HTTP header and the HTTP
Instead of concatenating the bodies and dividing them by the MSS from the beginning, the HTTP header is treated separately and the HTTP bodies are divided by the MSS.

Then, regarding the HTTP header,
A TCP header is created using only the TP header as TCP packet data, and a TCP packet is created. in this case,
The checksum is calculated from the TCP packet data and the TCP packet header.

On the other hand, regarding the HTTP body,
A TCP packet is generated by using each block obtained by dividing the P body by the MSS as TCP packet data.
In this case, since the checksum for each block of the data serving as the HTTP body is calculated in advance, a TCP packet header is created for each block, and T
The checksum for the entire packet is calculated using the CP packet header and the pre-calculated checksum, and T
Generate a CP packet.

FIG. 9 shows a process of calculating a checksum for a packet including an HTTP header and calculating a checksum for a packet including an HTTP body. As shown in (a), each block of the HTTP body (each HTTP
The checksum for data is calculated in advance. Then, as shown in (b), the checksum calculation for the packet including the HTTP header is calculated from the TCP header and the TCP data (that is, the HTTP header). However, the checksum calculation for the packet including the HTTP body is based on the HTTP data. Can be calculated from the calculated checksum for and the TCP header. In FIG. 9B, reference numeral 200 denotes a computing unit for calculating a checksum (for example, a computing unit of a 1's complement sum for every 16 bits), and 201 denotes a computing unit 2
00 indicates the operation result (for example, 16 bits).

FIG. 10 shows, by way of example, the structure of each TCP packet when the HTTP header is 200 bytes, the HTTP body is 10,000 bytes, and the MSS is 1,460 bytes. In FIG. 10, TCP packet 1
Is composed of an HTTP header. The TCP packet data of the TCP packets 2 to 6 is composed of 1,460 bytes of HTTP data. The TCP packet data of the TCP packet 7 is 1,
It consists of 240 bytes of HTTP data.

Now, the protocol processing unit 23
An IP header is created, and an IP packet is created (step S38).

The packet transmitting section 24 transmits the IP packet to the packet switching network 3 (Step S39).

As described above, when data consisting of a data part whose contents can change and a data part whose contents do not change is to be delivered, the former data part and the latter data part are mounted in different packets. Such a configuration can also be implemented in combination with the second embodiment, other modified examples, conventional examples, and the like.

FIG. 11 shows an example of an operation procedure of the data delivery system when such a configuration is combined with the second embodiment. The operation and the flow of processing in each section in this case are self-evident from the description so far, and the detailed description is omitted here.

In the above description, the data is stored in the temporary storage unit 22 in an undivided state. Instead, the data is divided by the MSS, and the checksum of each divided block is calculated. An example in which the packet is sent to the network and stored in the temporary storage unit 22 is also conceivable. Further, as in the first and second embodiments, an example in which a checksum and data are stored in the data storage device 1 in advance is also conceivable. In any case, when a TCP packet is generated by the protocol processing unit 23, a TCP packet in which data (for example, an HTTP header) for which a checksum has not been calculated in advance is different from data (for example, an HTTP body) in which a checksum has been calculated in advance. To be configured. In the present embodiment, HTT
Although the P data has been described as an example, the present invention is not limited to the HTTP data, but may be any example in which data in which a checksum is calculated in advance is transmitted after data in which a checksum is not calculated in advance.

Incidentally, in each of the above embodiments,
When a plurality of networks exist between the data distribution system and the client, the smallest MSS of the MSSs of the plurality of networks (ie, the MSS on the path)
S) was used to generate packets, but MSS
Regardless of the size of the network, it is also possible to use the MSS of the network to which the data delivery system is directly connected among the plurality of networks.

In the above description, the MSS on the path or the MSS of the network to which the data delivery system is directly connected is used as the “packet transfer unit” for dividing the requested data into blocks.
It is also possible to use a value smaller than the MSS as a packet transfer unit.

The above functions can also be realized as software.

Further, the present embodiment is a computer in which a program for causing a computer to execute a predetermined means (or for causing the computer to function as the predetermined means or for causing the computer to realize the predetermined function) is recorded. It can also be implemented as a readable recording medium.

The present invention is not limited to the above-described embodiments, but can be implemented with various modifications within the technical scope.

[0126]

According to the present invention, it is possible to speed up the calculation of the check code and the speed of packet generation at the time of packet generation even when the packet transfer unit may be different each time data is delivered. .

Further, according to the present invention, it is possible to speed up the calculation of the check code at the time of packet generation and the speed of packet generation even when the packet header format may be different each time data is delivered. .

Further, according to the present invention, even when data including a portion whose contents change every time data is delivered, the calculation of the check code at the time of packet generation and the speed of packet generation are achieved. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a data delivery system according to a first embodiment of the present invention;

FIG. 2 is a diagram for explaining a process from calculation / storage of a checksum for data to calculation of a checksum / packet generation for an entire packet;

FIG. 3 is a diagram showing an example of a storage format of data and a checksum;

FIG. 4 is an exemplary flowchart illustrating an example of an operation procedure of the data delivery system according to the embodiment.

FIG. 5 is a diagram showing a configuration example of a data delivery system according to a second embodiment of the present invention.

FIG. 6 is an exemplary flowchart illustrating an example of an operation procedure of the data delivery system according to the embodiment.

FIG. 7 is a diagram showing a configuration example of a data delivery system according to a third embodiment of the present invention;

FIG. 8 is an exemplary flowchart illustrating an example of an operation procedure of the data delivery system according to the embodiment.

FIG. 9 is an exemplary view for explaining a checksum calculation process in the embodiment.

FIG. 10 is a diagram showing a configuration example of a TCP packet according to the embodiment;

FIG. 11 is an exemplary flowchart showing another example of the operation procedure of the data delivery system according to the embodiment;

FIG. 12 is a diagram for explaining generation of a packet;

FIG. 13 is a diagram showing a configuration of a conventional data delivery system.

FIG. 14 is a diagram showing a data structure stored in a data storage device of a conventional data delivery system.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 data storage device 2 data transmission device 3 packet switching network 21 checksum calculation unit 22 temporary storage unit 23 protocol processing unit 24 packet transmission unit 25 HTTP processing unit

Claims (14)

[Claims] A data delivery system for writing a check code for each packet into each packet when the data is packetized and delivered, wherein a plurality of data and a certain data are calculated for each packet transfer unit. Storage means for storing the check code, and generating a packet by dividing the data to be delivered stored in the storage means, and transferring a packet corresponding to the data to the storage means. A data delivery system, comprising: when check codes are stored in units, processing means for calculating check codes to be written in each packet using the stored check codes. 2. A check code for each of the corresponding packet transfer units is calculated for the data to be delivered, if the check code for the corresponding data transfer unit is not stored in the storage means. 2. The data delivery system according to claim 1, further comprising means. 3. The processing means generates a packet by adding a packet header to each block obtained by dividing the data in the unit of the packet transfer, and calculates each packet with respect to a block included in the packet. 3. The data delivery system according to claim 1, wherein a check code for the packet is calculated from the check code and the packet header, and the calculated check code is written in a predetermined area of the packet header. 4. The storage means includes a first storage means which can be accessed at a higher speed, and a second storage means having a larger capacity, wherein the first storage means has at least data which has been delivered. And a check code for each packet transfer unit at the time of the delivery of the data, for temporarily storing the storage code as an upper limit, and the second storage means is at least a delivery target. 4. The data delivery system according to claim 1, wherein the data delivery system is for storing data. 5. A check code in a packet transfer unit corresponding to the data to be delivered, is not stored in the first and second storage means, and a packet transfer unit corresponding to the data is not stored. 5. The data delivery system according to claim 4, wherein when the check code for each is calculated, the calculated check code is stored in the first storage unit. 6. 6. When overwriting a predetermined storage area of the first storage means, a check code for data to be deleted from the first storage means due to the overwriting is replaced with a check code for the second storage means. 5. The data is written back to the storage means.
Or the data delivery system according to 5. 7. The data delivery system according to claim 1, wherein said check code is for checking the integrity of the contents of a packet to be written. 8. The data delivery system according to claim 1, wherein said check code can be calculated sequentially. 9. The packet transfer unit is set to a value equal to the maximum segment size that can be transmitted to a network connected to a client that has requested data delivery among networks directly connected to the own system. The data delivery system according to claim 1. 10. The apparatus according to claim 1, wherein said packet transfer unit has a value equal to the smallest one of the maximum segment sizes that can be transmitted to each network existing between the own system and the client. 10. The data delivery system according to any one of items 9. 11. When the data to be delivered includes a first data portion whose contents can change and a second data portion whose contents do not change, the first data portion and the second data portion are not transmitted. The data according to any one of claims 1 to 10, wherein a packet is generated such that the packet is mounted on a different packet, and a process related to a check code for the data is performed only on the second data portion. Delivery system. 12. When the data to be delivered is composed of a first data portion for which a check code is not calculated and a second data portion for which a check code is stored in said storage means. A packet is generated such that the first data portion and the second data portion are mounted on different packets, and a check code for a packet including the second data portion uses the stored check code. 12. The method according to claim 1, wherein the calculation is performed by:
Data delivery system described in the section. 13. The data delivery system according to claim 11, wherein said first data part is an HTTP header, and said second data part is an HTTP body. 14. A data delivery method for a data delivery system in which a check code for each packet is written in each packet when the data is packetized and delivered. It checks whether the check code calculated for each packet transfer unit determined according to the client is stored in the own system, and if not, checks the data for each packet transfer unit. Calculating a code, storing the calculated check code at least temporarily in the own system, generating a packet by dividing the data to be delivered, and transferring the packet to the stored data. Calculates the check code to be written in each packet using the check code for each unit Data delivery method to be.