JPH0669957A - Data transmission method and data transmitter - Google Patents

Abstract

(57) [Summary] [Object] The present invention reduces the load of packet generation processing at the time of transmitting data stored in advance in a storage device, and at the same time, a transmission data storage method that does not require buffer holding for retransmission. And a data transmission device. [Configuration] Data to be transmitted is divided in advance, a packet is configured and stored in the storage device 1. The data transmission device 2 sends the data thus stored in the form of packets from the storage device as it is. For retransmission, the packet in the storage device 1 is used as it is. [Effect] The present invention exerts a great effect particularly when repeatedly transmitting immutable data stored in advance, such as a movie or music delivery service.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method and device for transmitting data to a packet switching network.

[0002]

2. Description of the Related Art At present, high-speed networks of 100 Mbps class such as FDDI have become common, and Gb in the near future.
Development of ultra-high-speed networks in the ps class is expected to progress. In addition, the integration density of ROM is rapidly improving,
It is quite predictable that M will be used as a storage medium such as a current CD or VTR. One of the applications under such circumstances is expected to be a service for delivering video, music, and large-scale files from a base station to a plurality of child stations. In this case, if transmission is performed by the conventional method, the load of data transmission processing at the base station is expected to become a bottleneck.

A conventional data transmission apparatus will be described below with reference to the drawings. In FIG. 8, reference numeral 1 denotes a storage device, which stores data to be transmitted. 2 is a data transmission device. 3 is a packet switching network, and the data transmitting device 2 transmits packets on this network. 27 is a transmission buffer,
The data stored in the storage device 1 is stored in the transmission buffer 2
The capacity of 7 is once copied to the transmission buffer 27. Reference numeral 28 denotes a header template table, which holds information that does not change for each connection, such as the address of the packet header. A protocol processing means 29 establishes a connection and searches the header template table 28 for a corresponding header template. Further, the protocol processing means 29 cuts out from the transmission buffer 27 data of a length that can be transmitted, and searches for the header
A header is constructed from the information of the template and information not found in the header template such as the separately calculated checksum value and sequence number, and this header is added to the beginning of the data cut out earlier to form a packet. Reference numeral 21 is a transmission means for transmitting the packet configured as described above to the packet switching network 3. When conforming to a protocol for confirming from the destination and retransmitting an unconfirmed packet after a lapse of a certain time, even after the transmitting means 21 sends out the packet, the transmission buffer remains until the confirmation from the destination is received. The data in 27 is retained.

[0004]

However, in the above-mentioned conventional data transmitting apparatus, a packet cannot be formed until after the data is read from the storage device, and the packet generation process becomes a bottleneck during data transmission. . Even if the access speed to the storage device becomes high, the data recorded continuously must be cut out once,
This problem is not resolved. If you need more resends,
The contents of the send buffer need to be retained for retransmission until confirmation is obtained.

The present invention particularly provides a data transmission method for realizing high-speed transmission that does not require processing time for packet generation processing, particularly when transmitting data such as movies and music stored in advance in a storage device. An object is to provide a data transmission device. It is another object of the present invention to provide a data transmission method and a data transmission device capable of flexibly coping with changes in packet management information such as a destination address for each communication. A further object of the present invention is to provide a data transmission method and a data transmission device that do not need to hold a packet for retransmission even when retransmission is required.

[0006]

In order to achieve the above object, a data transmitting method according to a first aspect of the present invention is to divide data to be transmitted into packet transfer units, and use a protocol used in a packet switching network for each divided data. It is characterized in that a compliant packet is constructed and stored in advance in the storage means, and at the time of transmission, the data transmission means refers to the storage means and transmits the corresponding packet to the connected packet switching network.

According to a second aspect of the present invention, in the first aspect, all or part of the management information field contained in the packet stored in the storage means is a fixed value determined in advance or a value used by the packet transmission means. It is characterized by being set to. According to the invention of claim 3, in claim 1, the management information field of the packet has a first field for writing information unique to the communication in progress and a second field for writing a checksum value, and the packet is When stored in the storage means, a predetermined fixed value is written in the first field, and a temporary checksum value calculated excluding the first field is written in the second field. Information unique to communication is written in a field, and a true checksum value including the temporary checksum value and information unique to communication written in the first field is written in a second field. .

According to a fourth aspect of the present invention, a storage means for adding a management information field to each data divided into packet transmission units and storing the data in the form of packets according to the protocol used in the packet switching network, A connection connecting means for establishing a connection with the packet switching network before transmitting the packet and releasing the connection after the transmission is completed, and a packet transmitting means for reading and transmitting the packet from the storing means to the packet switching network with the established connection are provided. It is characterized by being.

According to a fifth aspect of the present invention, in the fourth aspect, the data transmission device further includes a next transmission address holding unit that holds a storage address of a packet to be transmitted next in the storage unit. According to a sixth aspect of the present invention, in the fifth aspect, the data transmission device further includes unique information adding means and checksum calculating means, while the packet writes information unique to the communication being executed in its management information field. It has a field and a second field for writing a checksum value. When the field is stored in the storage means, a predetermined fixed value is stored in the first field, and a temporary field calculated by excluding the first field in the second field. Checksum values are stored respectively, during transmission, information unique to the communication being executed is written in the first field by the unique information adding means, and in the second field, a temporary checksum value is written in the first field. It is characterized in that a direct checksum value in consideration of information unique to communication is written by the checksum calculating means.

According to a seventh aspect of the present invention, in the sixth aspect, the data transmitting apparatus further includes a content restoring means for restoring the content of the management information field of the packet changed during the transmission when the packet transmission is completed. It is characterized by that. The invention of claim 8 is the switching network according to claim 7, wherein the packet switching network uses a protocol for confirming the transmitted packet and retransmitting the unconfirmed packet after a certain period of time. It is characterized by including transmission address holding means for holding the address of the confirmed packet in the storage means.

[0011]

According to the inventions of claims 1 and 4, a plurality of packets are constructed in advance from the data to be transmitted and stored in the storage means in the form of packets, and the packet transmission means keeps the packets in the storage means as they are. Send. This reduces the load of packet generation during data transmission.

According to the second and fifth aspects of the present invention, all or part of the management information field of the packet header is a predetermined fixed value (zero or the like), or
The value is set to a value that can be used later by the packet transmitting means (a value obtained by calculating the checksum value halfway) and stored, and the packet transmitting means adds some information to the packet in the storage means and transmits it. This makes it possible to flexibly deal with changes in the management information of packets while reducing the load of packet generation.

According to the third and sixth aspects of the invention, in the management information field of the packet header, information (address etc.) peculiar to communication is set to a predetermined fixed value (zero etc.) and checked. The sum value is stored as a temporary checksum value calculated by excluding the field set to a fixed value. Information specific to communication is added to the packet thus stored, and then the overall checksum value is calculated. Finally, send this packet. As a result, it is possible to flexibly deal with changes in packet management information, such as a transmission destination, which changes with each communication, while reducing the load of packet generation.

According to the invention of claim 7, when the transmission of the packet is completed, the contents of the management information field of the packet in the storage means are restored from the state changed at the time of transmission. This is convenient, for example, when transmitting the same data to a plurality of destinations. That is, if the destination is different,
Only the contents of the first field called the destination address and the contents of the second field accompanying it are changed, and the contents of the other management information fields are not changed. Therefore, the original contents are restored every time the packet transmission is completed. By returning the data and storing it in the storage means, it is only necessary to change the same field for each transmission in the same manner, and it becomes very easy to perform packet transmission processing to different transmission destinations.

According to the invention of claim 8, in a packet switching network using a protocol for confirming a transmitted packet and retransmitting an unconfirmed packet after a lapse of a fixed time, the transmission address holding means stores the transmitted packets in the storage means. The position and the position of the confirmed packet are retained and retransmitted using this. This eliminates the need to hold a buffer for retransmission.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a storage device, 2 is a data transmission device, and 3 is a packet switching network. In the storage device 1, data to be transmitted is divided into a plurality of packets and stored so that the length of each packet is the maximum transfer unit in the protocol adopted in the packet switching network 3. However, the length of the packet located at the end of the data may be less than or equal to the maximum transfer unit.

FIG. 2 shows a specific example of the packet stored in the storage device. P1 to P685 are stored packets, and the packet headers H1 to H1
It is composed of H685 and data parts D1 to D685. The packet headers H1 to H685 include all the management information necessary for constructing a packet such as a destination address, a source address and a checksum. The data is divided so that the length of each packet is the maximum transfer unit, and the remainder is the length of the final packet. FIG. 2 shows a division method when the data length is 1 megabyte, the maximum transfer unit is 1500 bytes, and the header length is 40 bytes. In this case, since the data length that can be included in one packet is 1460 bytes, as shown in FIG.
684 bytes long packets and 1 packet 1400 bytes long are stored in the storage device 1. At the front of the area in which each packet is stored, a flag indicating whether or not the packet is final is set. In the above example, 6
The flag corresponding to 84 1500-byte-long packets is set to 0, and the flag corresponding to the final 1400-byte-long packet is set to 1.

The data transmitting device 2 comprises a transmitting means 21, a connection connecting means 22 and a next transmission address holding means 23. The transmission means 21 transmits the packet from the storage device 1 to the packet switching network 3. Connection connection means 22
Establishes a connection with the destination before actually sending the data and releases the connection after the end of the transmission. The next transmission address holding unit 23 holds the address of the packet to be transmitted next among the packets in the storage device 1.

The operation of the data transmitting apparatus of this embodiment will be described below with reference to the flowchart of FIG. First, the data transmission device 2 that tries to transmit the data in the storage device 1
Establishes a connection with the destination using the connection connection means 22. After the connection is established, the connection connection means 22 compares the packet header of the packet corresponding to the address held by the next transmission address holding means 23 with the information on the established connection (step 2). If they do not match (step 3), the connection is released in step 31 and the user is notified of this (step 31). On the other hand, if the packet header and the connection information match, the next transmission address holding means 23 notifies the transmission means 21 of the start address of the packet to be transmitted (step 4), and then the transmission means 21 notifies. It is determined whether the corresponding flag of the transmitted packet to be transmitted is set (step 5). If the flag is not set, the transmission means 21 transmits the packet of the maximum transfer unit length to be transmitted from the storage device 1 to the packet switching network 3 (step 6), and the next transmission address holding means 23 holds it. The address is updated to the start address of the next packet (step 7). After that, steps 4 to 7 are repeatedly executed to successively send out the packets designated by the next transmission address holding means 23. Then, when a packet with a flag set is designated by the next transmission address holding means 23 (step 5), the transmission means 21 looks at the header of the final packet and transmits only the packet length to the packet switching network 3. (Step 51). After that, the end of transmission is notified to the connection connecting means 22 (step 8), and the connection connecting means 22 releases the connection and notifies the user that the transmission is completed (step 9).

According to this embodiment, since the data is recorded in the storage device in the form of a packet, the data transmission device does not need to generate a packet again, and the load of the data transmission process is reduced. However, in the case of this embodiment, the packet stored in the storage device must be stored in a complete form. Therefore, it is necessary to prepare a storage device for each destination and each user.

The second embodiment described below mainly improves this point. 4 and 5 show a second embodiment according to the present invention. The components having the same functions as those shown and described in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 4, reference numeral 24 is a unique information adding means, and 25 is a checksum calculating means. Here, the unique information means information unique to communication, and in this embodiment, the addresses and port numbers of the own station and the destination are used. The unique information assigning means 24 writes the unique information in the corresponding field of the packet header when transmitting the packet.
Initially, zero is written in the field for writing the unique information of the packet header. In the checksum field of the packet header, the checksum value calculated excluding these unique information fields is written as a temporary value.

The operation of the data transmitting apparatus of this embodiment will be described below with reference to the flowchart of FIG. First, the data transmission device 2 that tries to transmit the data in the storage device 1
In step 1, the connection connection means 22 is used to establish a connection with the destination. After the connection is established, the connection connecting means 22 notifies the unique information adding means 24 of the addresses and port numbers of the own station and the destination as the unique information (step 2). continue,
The next transmission address holding means 23 notifies the unique information addition means 24 of the start address of the packet to be transmitted next (step 3), and the unique information addition means 24 notifies the unique information of the packet to be transmitted in step 2. Write in the appropriate field (step 4). Next, the checksum calculating means 25 calculates the checksum value of the packet to be transmitted and writes it in the checksum field (step 5). At this time, the temporary checksum value written in advance is held.

Note that in many protocol checksum calculation methods, the order of calculation is arbitrary; in such cases, the checksum field is calculated in advance instead of calculating the checksum value from the entire packet. The correct checksum value is calculated from the provisional value written in and the newly written unique information. Next, in step 6, the next transmission address holding means 23 notifies the transmission means 21 of the start address of the packet to be transmitted, and in step 7
Then, the transmitting means 21 determines whether or not the flag corresponding to this packet is set. If the flag is not set, the process proceeds to step 8, the transmitting means 21 transmits the packet of the maximum transfer unit length to be transmitted from the storage device 1 to the packet switching network 3, and in step 9, the next transmission address holding means 23. Restores the changed part of the transmitted packet in the storage device 1 and updates the start address of the held packet to the start address of the next packet.
Return to. The processing of step 9 is performed in consideration of convenience when transmitting the same data to a plurality of users, as described in the section of the operation.

If the flag is set at step 7, the transmitting means 21 looks at the header of the final packet and transmits only the packet length to the packet switching network 3 at step 71. After that, in step 10, the end of transmission is notified to the connection connecting means 22, and in step 11, the connection connecting means 22 releases the connection and notifies the user that the transmission is completed.

In this embodiment, the processing of step 9 is performed by the next transmission address holding means 23, but it can be performed by other means, or a new means for restoring the changed portion can be provided. It may be provided separately. In this embodiment, the unique information adding means and the checksum calculating means write necessary information in the header of each packet in the storage device by utilizing the idle time of the CPU, parallel processing, etc., and complete the packets one after another. It is possible to go.

According to the present embodiment, the information unique to the communication can be determined for each communication, so that the load of packet generation processing can be reduced and the information can be a destination such as a home delivery service. It is possible to deal with an unspecified large number of potential stations. Next, a third embodiment of the present invention will be described with reference to FIGS. The components having the same functions as those shown in FIGS. 1 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 6, reference numeral 26 designates a transmission position holding means, up to which packet the transmission means 21 has finished transmitting,
Holds which packet was confirmed by the destination. For example, when the packets in the storage device 1 are physically aligned and stored, the head address of the most recently transmitted packet and the head address of the most recently confirmed packet are held. In addition, the transmitting means 2 of this embodiment
Different from the transmitting means of the above-mentioned embodiment, 1 holds the number of packets that can be transmitted in the future in order to realize flow control.

The operation of the data transmitting apparatus of this embodiment will be described with reference to the flowchart of FIG. In Figure 7,
Since the operations of steps 1 to 7 are almost the same as those of the second embodiment described with reference to FIG. 5, detailed description will be omitted. However, in step 5, in the present embodiment, the checksum calculation means 25 notifies the transmission position holding means 26 of the temporary checksum value held by the checksum calculation means 25 in the second embodiment together with the start address of the packet. The transmission position holding means 26 holds this.

If the flag is not set in step 7, it is determined in step 8 whether the previously transmitted packet has been confirmed by the destination. If it is confirmed, in step 81, the value of the head address of the confirmed packet of the transmission position holding means 26 is updated to
The changed portion of the header is returned to the original, the value of the number of transmittable packets held by the transmitting means 21 is updated, and the process proceeds to step 9. If there is no packet confirmed in step 8, the process directly goes to step 9. At step 9, it is determined whether or not retransmission is necessary. If the packet needs to be retransmitted, the transmitting means 21 is notified of the packet to be retransmitted in step 91, the packet is retransmitted in step 92, and the process returns to step 8. If retransmission is not necessary in step 9, step 10
Then, the transmitting means 21 determines whether or not the packet can be transmitted from the held value of the number of transmittable packets held. If the transmission is impossible, the process returns to step 8 and waits for confirmation from the transmission destination. If transmission is possible, step 11
In step 12, the transmission means 21 transmits the packet to be transmitted, and in step 12, the transmission position holding means 26 updates the value of the head address of the transmitted packet held therein to the head address of the packet to be transmitted, The processing from step 3 onward is repeated.

If the flag is set in step 7,
In step 71, it is determined whether the previously transmitted packet has been confirmed by the destination. If it is confirmed, in step 711, the value of the start address of the confirmed packet of the transmission position holding means 26 is updated to
The changed portion of the header is returned to the original, the value of the number of transmittable packets held by the transmitting means 21 is updated, and the process proceeds to step 72. If there is no packet confirmed in step 71, the process directly proceeds to step 72. At step 72, it is determined whether a resend is necessary. If the packet needs to be retransmitted, the packet to be retransmitted is notified to the transmitting means 21 in step 721, and the packet is retransmitted in step 722.
Return to. If the retransmission is not necessary in step 72, the transmitting means 21 determines whether or not the packet can be transmitted from the held value of the number of transmittable packets in step 73. If the transmission is impossible, the process returns to step 71 and waits for confirmation from the transmission destination. If it is possible to send, step 7
In step 4, the transmission unit 21 transmits the final packet, and in step 75, the address of the transmitted packet held by the transmission position holding unit 26 is updated. Next, in step 76, it is determined whether all transmitted packets have been acknowledged. If there are unconfirmed packets, step 761
Then, it is judged whether or not the retransmission is necessary, and if it is necessary, the retransmission is performed in step 762 and the process returns to step 76. If the retransmission is not necessary, the confirmation is waited for in step 7611 from the destination. After the confirmation from the transmission destination arrives, in step 7612, the changed portion of the storage device is restored, the address held by the transmission position holding means 26 is updated, and step 76
Return to. If all the transmitted packets are confirmed in step 76, in step 13, the connection connecting means 22 releases the connection and notifies the user that the transmission is completed.

As described above, according to the present embodiment, data transmission with reduced load for packet generation can be performed even in the case of conforming to the protocol for confirming from the destination and retransmitting the unconfirmed packet after a certain period of time. realizable. Furthermore,
According to the present embodiment, since the data transmission device directly refers to the storage device, it is not necessary to prepare a buffer for retransmission,
It is possible to eliminate the load associated with managing the retransmission buffer.

In the above three embodiments, the packet stored in the storage device may be a packet of any layer of the OSI reference model. For example, if the packet of the fourth layer is stored, the transmitting means in the data transmitting device executes the processing of the third layer and below. In this case, a field containing the packet header of the third layer and below is reserved in front of each packet stored in the storage device, and the data transmission device constructs the packet header of the third and below layers of the first packet. After that, at an appropriate timing, the common part of the packet header of the third layer and the layers other than the checksum may be copied to the corresponding field of the packet which has not been transmitted in the storage device. The same operation may be performed regardless of the layer of the OSI reference model in which the packet is stored.

[0033]

As described above, according to the present invention, by storing the data to be transmitted in the form of packets in the storage device, it is possible to reduce the load of packet generation in the data transmission device. Further, even when it is necessary to retransmit an unconfirmed packet after a lapse of a certain period of time, it is not necessary to hold a buffer for retransmission, and the load associated with buffer management can be reduced.

These are very effective when repeatedly transmitting prerecorded data such as a movie or music delivery service.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a data transmission device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a specific example of the transmission data storage structure.

FIG. 3 is a flowchart showing the operation of the data transmission device.

FIG. 4 is a block diagram showing a configuration of a main part of the data transmitting apparatus according to the second embodiment.

FIG. 5 is a flowchart showing the operation of the data transmitting apparatus of the second embodiment.

FIG. 6 is a block diagram showing a configuration of a main part of a data transmitting apparatus according to the third embodiment.

FIG. 7 is a flowchart showing the operation of the data transmitting apparatus of the third embodiment.

FIG. 8 is an explanatory diagram of a conventional data transmission device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 storage device (storage means) 2 data transmission device 21 transmission means 22 connection connection means 23 secondary transmission address holding means 24 unique information addition means 25 checksum calculation means 26 transmission position holding means 3 packet switching network

Claims (8)

[Claims] 1. Data to be transmitted is divided into packet transfer units, a packet according to a protocol used in a packet switching network is constructed for each divided data, and this is stored in a storage means in advance, and data is transmitted at the time of transmission. A data transmission method, wherein the transmission means refers to the storage means and transmits the corresponding packet to a connected packet switching network. 2. The management information field included in the packet stored in the storage means is wholly or partially set to a predetermined fixed value or a value used by the packet sending means. The data transmission method according to claim 1. 3. The management information field of the packet has a first field for writing information specific to the communication in progress and a second field for writing a checksum value, the packet being stored in a storage means. When the packet is transmitted, a predetermined fixed value is written in the first field, and a temporary checksum value calculated excluding the first field is written in the second field. 2. The data according to claim 1, wherein information is written, and a true checksum value including the temporary checksum value and the communication-specific information written in the first field is written in a second field. How to send. 4. Storage means for adding a management information field to each data divided into packet transmission units and storing the data in the form of packets according to a protocol used in a packet switching network, and a packet before packet transmission. A connection connection means for establishing a connection with the exchange network and releasing the connection after the transmission is completed; and a packet transmission means for reading out and transmitting a packet from the storage means to the packet exchange network with the established connection. And a data transmission device. 5. The data transmitting apparatus according to claim 4, further comprising a next transmission address holding unit that holds a storage address of a packet to be transmitted next in a storage unit. 6. The data transmitting device further includes a unique information adding unit and a checksum calculating unit, while the packet has a first field for writing information unique to the communication being executed in the management information field and a checksum value. Second to write
When it has a field and is stored in the storage means, a predetermined fixed value is stored in the first field, and a tentative checksum value calculated excluding the first field is stored in the second field. Sometimes, information unique to the communication being executed is written in the first field by the unique information adding means, and the second field is a true checksum value with the information unique to the communication written in the first field added. 6. The data transmitting apparatus according to claim 5, wherein the checksum value of is written by the checksum calculating means. 7. The data transmitting apparatus further comprises content restoring means for restoring the content of the management information field of the packet changed during transmission when the packet transmission is completed. Data transmitter. 8. The packet switching network is a switching network using a protocol for confirming a transmission packet and retransmitting an unconfirmed packet after a lapse of a certain time, and the data transmitting device stores a transmitted packet and a confirmed packet of a transmission destination. 8. The data transmitting apparatus according to claim 7, further comprising transmission address holding means for holding an address in the means.