JPH10164176A - Communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively transmit and receive the data even in a fast communication mode set for transfer of animations, etc., by securing the logical connection between the transmitting and receiving terminals, securing the correspondence between the receiving and transmitting requests by means of the identifiers added to both requests, and transferring the data to the receiving terminal from the transmitting terminal. SOLUTION: The computers 400 and 460 are connected to each other via a network 430, and the lower order protocol modules 406 and 466 control the data transmission function between both computers. Then an application or higher order protocol modules 402 and 462 designate an identifier of a receiving computer and an identifier that identifies the receiving opposite party of the receiving computer or a connection identifier to the middle order protocol modules 404 and 464 to perform the logical connection, to designate the designation of data, etc. Furthermore, a transmitting/receiving buffer, its length, etc., are designated for designation of the storing places of data to be transmitted and received.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a communication method in computer communication, and more particularly to a communication method suitable for a transport layer and a network layer in a protocol layer defined by an OSI reference model.

[0002]

2. Description of the Related Art Various types of data from character information to image information are exchanged between computers via a network. In these inter-computer communications, a relatively low-speed network of 10 Mbps or less has conventionally been used as a physical transmission path.
(Asynchronous Transfer Mo
As in de), high-speed networks ranging from 100 Mbps to 1 Gbps have been used.
With the increase in the speed of such a physical transmission path, overhead such as data copying and interrupt processing at the time of protocol processing on each computer has become a bottleneck for using up the bandwidth of the transmission path.

As a typical protocol of the transport layer, TCP (Transmission Control) is used.
l Protocol). This protocol is
“INTERNETWORKING WITH TCP
/ IP "(D. Comer, Prentice-Ha
ll International, Inc. , 19
88) pp. 129-151. TCP is a reliable connection-oriented stream-type protocol. By sequentially giving a sequence number to each byte unit flowing on a logical connection between two computers, all transmission data are in order, It guarantees that it is received without errors.
In TCP, data passed at the time of a transmission request from an upper layer is temporarily copied to a buffer in the TCP in preparation for retransmission when a packet is lost. The transmission request from the upper layer succeeds when this copy is completed.

When the data length passed at the time of this transmission request is larger than the maximum transfer length (MTU), the data is divided into a plurality of packets for each MTU, and a timer is set for each packet. When the packet is correctly received, an acknowledgment (ACK) including a position indicating how many bytes have been correctly received in the byte stream is returned from the receiving side to the transmitting side, and the transmitting side transmits the packet in the TCP according to the information in the ACK. Free the corresponding part of the buffer. Also,
The receiving side holds the received data in a buffer in the TCP until a reception request from the upper layer is received. Figure 2 shows the TCP
1 shows the exchange of packets when transmitting and receiving a packet. In FIG. 2, the transmitting side corresponds to the middle-level protocol module 404 when the computer 400 is a transmitting computer and the computer 460 is a receiving computer in FIG.
The receiving side in FIG. 2 also corresponds to the middle-level protocol module 464 in the receiving side computer 460. FIG.
In FIG. 4, SEQ = 9 indicates that the middle protocol module 404 on the transmitting side is different from the middle protocol module 404 on the receiving side in FIG.
In the transmission / reception byte stream space to H.64, data from the ninth byte is passed from the transmission side to the reception side. ACK = 21 corresponds to an acknowledgment indicating that data up to the 20th byte has been received in the transmission / reception byte stream space. In FIG. 2, first, the sequence numbers 9 to 2
12-byte data packet (SEQ =
9) is transmitted from the transmitting side to the receiving side, and at the same time, the transmitting side sets a timer in preparation for packet loss. Upon receiving this data packet, the receiving side sends back an acknowledgment (ACK = 21) including information that the packet before the sequence number 21 has been received to the transmitting side. Similarly, data corresponding to the sequence numbers 21 to 34 and 35 to 38 is transmitted, and a reception confirmation is returned. Here, if the data corresponding to the sequence numbers 39 to 48 is lost during transmission, the data after the sequence number 39 is retransmitted when the timer set at the time of the transmission times out.

[0005]

However, such a conventional method has the following problems.

That is, in TCP, it is necessary to copy data passed from an upper layer at the time of a transmission request without fail, which causes a considerable overhead when performing high-speed communication such as moving image transfer. Therefore, in order to avoid the copying at the time of transmission and perform reliable communication, it is necessary to hold the data buffer passed from the upper layer as it is in preparation for retransmission when a packet is lost. This data buffer needs to be held in the transport layer until ACK confirms that all data has been received correctly. In this case, the transmission buffer in the transport layer cannot be released even if ACK is returned for each packet as in TCP, and it is confirmed that all the data passed at the time of the transmission request has been correctly received. Therefore, the transmission buffer becomes unnecessary. That is, ACK for each packet such as TCP is wasted.

[0007] When asynchronous transmission is performed without copying at the time of transmission, a stream-based method such as TCP uses a transmission performed prior to a position indicating how many bytes have been correctly received in a byte stream. The request succeeds and terminates, but the transmission request made after that location cannot terminate the transmission request even though the data passed at the time of the request was correctly received. Similarly, at the time of asynchronous reception, it is possible that a certain reception request cannot be terminated although all the data has been correctly received. FIG.
Shows the relationship between the send / receive request and the send / receive byte stream during asynchronous send / receive. In FIG. 3, the transmission request corresponds to each transmission request received by the middle-level protocol module 404 from the application or the upper-level protocol module 402 when the computer 400 is a transmitting computer and the computer 460 is a receiving computer in FIG. Receiver middle protocol module 464
Is the application or higher-level protocol module 46
2 respectively. The transmission byte stream indicates the byte position occupied by the transmission data in the transmission byte space when the middle protocol module 404 transmits data to the lower protocol module 406. When receiving data from the protocol module 466, it indicates the byte position occupied by the received data in the received byte space. In FIG. 3, it is assumed that transmission / reception has been completed for the portions corresponding to 320 and 324 on the byte stream, and transmission / reception requests # 6 and # 7 can be terminated. Here, assuming that a portion corresponding to 326 is not received on the byte stream, in the case of TCP, even if a portion corresponding to 328 later is received, the transmission / reception request corresponding to the portion is terminated. Can not.

Further, in TCP, it is necessary to hold received data in a buffer in the TCP until a reception request is received. However, when performing high-speed communication such as moving image transfer, the received data is considerably large in order to hold the received data. Requires a buffer.

In a stream-type protocol such as TCP, the position of transmission / reception data is adjusted in byte units. Therefore, the transmission / reception position is not allowed to shift even by one byte. When the length of the transmission request is different from the length of the reception request, such as receiving the transmission request or receiving the transmission request with a 30-byte reception request for a transmission request whose value is unknown from 10 bytes to 30 bytes Can not respond.

[0010] Further, when synchronous transmission is performed without copying on the transmission side, the next data cannot be transmitted from when transmission of all data in the transmission request is completed until ACK is returned.

As described above, according to the conventional method, when performing high-speed communication such as moving image transfer, efficient communication with high speed and low CPU utilization cannot be performed, and it is necessary to exactly match byte positions between transmission and reception. There was a problem.

An object of the present invention is to provide a communication method which enables high-speed and efficient data transmission / reception with a low CPU usage rate even in high-speed communication such as moving image transfer.

Another object of the present invention is to provide a communication method between a pair of a transmission request and a reception request having different request data lengths.

[0014]

According to the present invention, a logical connection is established between a transmitting terminal and a receiving terminal, the transmitting terminal issues a transmission request for the logical connection, and the receiving terminal issues a logical connection to the logical connection. The present invention relates to a communication method in a communication system for performing data transfer via a network by issuing a reception request.

In this communication method, an identifier is added to the reception request and the transmission request in order to associate the reception request with the transmission request.

Here, in the present communication method, the same identifier as the transmission request corresponding to the reception request is added to the reception request. That is, the same identifier as the reception request corresponding to the transmission request is added to the transmission request.

By doing so, a transmission request and a reception request having the same identifier are paired on the transmitting terminal side and the receiving terminal side of the logical connection, and data is exchanged between the pair.

For example, this identifier is initialized to the same value at both ends of a connection when a logical connection is established, and is incremented for each transmission request and each reception request. If the value exceeds the “upper limit value that takes the same value”, an integer value returned to 0 can be assumed. Hereinafter, this integer value is called a request number, and a case where such an integer value is used as an identifier will be described.

These request numbers are given to each transmission request and reception request either at the time of each transmission request, before being updated at the time of reception request, or at any time after being updated. Transmission and reception are performed between requests having the same transmission request number and reception request number at both ends of the connection. On the transmission side, the data passed by the transmission request is divided for each maximum transfer length (MTU) and transmitted. The receiving side has a data structure indicating which part has been received for each reception request, determines the end of data reception between pairs having the same request number using this data structure, and sends back an ACK at the end of reception. . If copying is not performed on the transmission side, the buffer on the transmission side cannot be released even if ACK is sent back for each division unit, which is wasteful. Such useless ACK can be avoided. In the case of asynchronous transmission / reception, a request for which transmission / reception has been completed can be immediately terminated regardless of the order in which the requests were made. Due to such features, the present communication method has high speed and C
Efficient data transfer with low PU usage rate is possible.

If data corresponding to the transmission request arrives before the reception buffer is passed by the reception request, the data is discarded, but a data structure indicating the number of transmission requests of the receiving side has been reached. This transmission request number is set. Later, when the reception request is actually made, it is known from the data structure that the corresponding transmission request has already been made. Therefore, by returning a retransmission request (NACK) to the transmission side, the data is immediately transmitted. Retransmit. In this way, when the corresponding transmission request data arrives before the reception request is made, without holding the data,
By requiring retransmission when a reception request is actually made later, it is possible to eliminate the need to have a large buffer inside the transport layer even in high-speed communication such as moving image transfer.

Further, a field indicating the last packet in the request is provided in the transmission packet. If the request data length of the transmission request is smaller than the request data length of the corresponding reception request, this field is used. The receiving side is notified of the end of the transmission request data, and reliable communication is performed for data corresponding to the requested data length of the transmission request. If the request data length of the transmission request is larger than the request data length of the corresponding reception request, reliable communication is performed for the data corresponding to the reception request data length. In this case, A
A field for storing the actually received data length is provided in the CK, and the transmission side can also know the actually transmitted data length from the field. As described above, even when the transmission request length and the reception request length are different between the corresponding transmission request and reception request, reliable communication is performed for the data corresponding to the smaller request length. Receiving only the first five bytes for a transmission request,
For example, it is possible to perform reception using a 30-byte reception request for a transmission request that does not know which value from 10 bytes to 30 bytes takes.

In the case of synchronous transmission / reception, the latter half of the data in the transmission buffer during the transmission request is copied and held in a buffer on the transmission terminal. Temporary ACK in transmitted packet
A field indicating that a request is made is provided, and this field is set when the last packet of the portion not to be copied is transmitted. On the receiving side, when a packet in which a field indicating that a temporary ACK request is to be made is received, if all packets before that packet have already been received, a temporary ACK is returned. The transmitting side can make the next transmission request for the logical connection at the time of receiving the temporary ACK. Further, upon receiving the ACK, the copy data holding buffer on the transmitting terminal is released.

As described above, in the case of synchronous transmission / reception, the transmission request is issued one after another without waiting for ACK by copying and holding the latter half of the data in the transmission buffer in the transmission request in the buffer on the transmission terminal. it can. Even if the size of the copy portion is larger than the size corresponding to the round trip time of the packet, there is no effect on the reduction of the ACK waiting time. Therefore, if the size corresponding to the round trip time is the size of the copy portion, this size is a value that does not depend on the size of the transmission buffer during the transmission request. The ratio can be kept low. Therefore, this communication method enables efficient data transfer at high speed and with a low CPU usage rate.

Also in this case, by inserting the data length specified in the reception request into the provisional ACK, the smaller the transmission request length and the reception request length between the corresponding transmission request and reception request, the smaller is. With respect to the required length, reliable communication can be performed.

[0025]

Embodiments of the present invention will be described below in detail.

First, a first embodiment will be described. An object of the first embodiment is to enable high-speed and efficient data transmission / reception with a low CPU usage rate when copying is not performed on the transmission side, and to perform transmission and reception requests of different request data lengths. An object of the present invention is to provide a communication method between a pair.

FIG. 1 is a flowchart showing a processing procedure of the first embodiment, and FIG. 4 is a block diagram showing a system configuration and a protocol module hierarchy according to the present invention. FIG. 8 is a block diagram of the middle-level protocol module of FIG. 4. FIGS. 5, 6, and 7 show a data structure for storing transmission / reception requests in the middle-level protocol module, a data packet format, and a reception confirmation packet format, respectively.

In FIG. 4, computers 400, 46
0 is connected via the network 430. Here, the network 430 also includes connection devices such as ATM switches and routers.

The computers 400 and 460 have displays 418 and 478, keyboards 416 and 476, and a CPU.
414, 474, magnetic disks 412, 472, network cards 408, 468, main memories 410, 470
Consists of Displays 418, 478, keyboards 416, 476, magnetic disks 412, 472, network cards 408, 468, main memories 410, 4
Reference numeral 70 is accessed by the CPUs 414 and 474 via the bus. The main memories 410 and 470 have lower-order protocol modules 406 and 466 and a middle-order protocol module 4
04, 464, the application or the upper protocol module 402, 462 is loaded, and the work area 4
07 and 467 are secured.

Network interface card 40
Reference numerals 8 and 468 correspond to hardware for a network interface such as an ATM card. However, some or all of the functions corresponding to the network interface cards 408 and 468 are provided by the computers 400 and 460.
Instead, it is also possible to adopt a configuration in which the device is attached to the computers 400 and 460 in the network 430. Also, the lower-level protocol modules 406 and 466 and the middle-level protocol module 4 in the network interface cards 408 and 468
In some cases, some of the functions corresponding to the functions 04 and 464 are realized as hardware.

Lower protocol modules 406, 466
Is a protocol module mainly corresponding to a physical layer, a data link layer, and a network layer in a protocol layer defined by the OSI reference model, and provides a function for performing data transmission between two computers. The middle-level protocol modules 404 and 464 provide the lower-level protocol modules 406 and 466 with the identifier (IP address, MAC address, etc.) of the receiving computer or AT
When a connection is established as in M, data transmitted / received by specifying its identifier (VPI / VCI number, etc.) to specify the destination of the data, and further specifying the transmission / reception buffer, buffer length, etc. Specify the storage location of.

The middle level protocol modules 404, 464
Is a protocol module mainly corresponding to a transport layer and a network layer in a protocol layer defined by the OSI reference model, and uses functions of lower-order protocol modules 406 and 466 to communicate between software modules such as applications on two computers. Provides a function for performing communication of The application or the upper protocol modules 402 and 462 provide the middle protocol modules 404 and 464 with the identifier of the receiving computer and the identifier for identifying the receiving party on the receiving computer (such as the port number of TCP or UDP). Or, by specifying a connection identifier obtained when establishing a connection from these identifiers, the connection of the logical connection, the specification of the data destination, etc., and the transmission / reception by specifying the transmission / reception buffer, buffer length, etc. Specify the storage location of the data to be copied.

The application or higher-level protocol module 402, 462 includes the middle-level protocol module 40
4 and 464.

The work areas 407 and 467 are memory areas used when exchanging data between modules.

In FIG. 5, connection data structure 5
00 resides in the middle protocol modules 404,464. The connection data structure 500 is a data structure assigned to each connection when establishing a logical connection. The transmission queue 502 stores a data structure used when a transmission request is issued from an application or the upper protocol modules 402 and 462. And a reception queue 504 are queues for storing a data structure used at the time of a reception request from the application or the upper protocol modules 402 and 462. The transmission request data structure includes a transmission request number, a transmission request data length, a transmission request buffer, and the like, and the reception request data structure includes a reception request number, a reception request data length, a reception request buffer, and an actual reception request buffer. And a list indicating the received data portion. Send queue 5
Among the transmission requests in 02, the transmission request waiting for Ack has already been transmitted and is a transmission request in an acknowledgment response state, and the transmission request being transmitted indicates the transmission request currently being transmitted. A transmission request waiting for transmission indicates a transmission request that has not been transmitted yet and is in a transmission waiting state. All the reception requests in the reception queue 504 indicate reception requests that have been received but have not yet been received.

FIG. 6 shows the middle-level protocol module 4 in FIG.
4 shows a format of a data packet passed between the data packets 04 and 464. The connection identifier 600 is an identifier assigned to identify each connection when establishing a connection in the middle-level protocol modules 404 and 464, and the request number 602 indicates which transmission request data structure this data packet belongs to. The offset 604 indicates from which position in the transmission request to which the data packet belongs data is included. The offset 604 may be specified in byte units, but if the maximum transfer length (MTU) is agreed in advance at both ends of the connection, the transmission request is divided into MTU units, so UNIT indicating whether it is a division unit (UNIT)
A unit number may be specified. The packet length 606 indicates the length of this packet in bytes. Last Pa
The ticket Flag is a flag that is set when this data packet is a packet including the last data of the transmission request. The receiving side knows the length of the transmission request when receiving the packet with this flag set. Can be
If the transmission request length is shorter than the request length, ACK is returned when the data for the transmission request length is received, and the reception request ends.

A specific example of the data packet format shown in FIG. 6 is shown below. The connection identifier 600 is TCP or U
Similarly to the port number in the DP, a number such as 60 is assigned. The request number 602 is a unique number assigned to each request when a transmission request is issued, and is 16
If it is a bit, an appropriate value between 0 and 65535 is taken.
For example, a value such as 8 is assigned. When the offset 604 is indicated by a number in UNIT units, 3UNI
UNIT numbers are assigned to each division unit in order from 0, such as at the T-th. The packet length 606 is specified by a value such as 512 bytes. Last
Packet Flag usually takes a value of either 0 or 1.

FIG. 7 shows the middle-level protocol module 4 in FIG.
4 shows the format of the acknowledgment packet passed between 04 and 464. The connection identifier 700 is a data structure assigned to each connection when establishing a connection in the middle-level protocol modules 404 and 464, and the request number 702 indicates which transmission request this reception confirmation packet is an acknowledgment (ACK) for this transmission request. Show. The reception length 704 indicates the data length actually received by the reception request. The reception side 704 allows the transmission side to notify the application or the upper protocol modules 402 and 462 of the actually transmitted data length at the end of the transmission request even when the reception request length is shorter than the transmission request length.

A specific example of the format of the acknowledgment packet shown in FIG. 7 is shown below. The connection identifier 700 is assigned a number such as No. 60 in the same manner as a port number in TCP or UDP. The request number 702 is a request number of a pair of a transmission request and a reception request whose reception is confirmed by the reception confirmation packet, and is assigned a value such as 8 or the like. The reception length 704 is the data length actually received by the reception request, and is specified by a value such as 3584 bytes.

Next, the operation of each unit in FIGS. 4, 5, 6, and 7 will be described with reference to the flowchart of FIG.

First, when the application or the upper protocol modules 402 and 462 make a transmission request or a reception request to the middle protocol modules 404 and 464 (step 100), in the case of a transmission request, a transmission request data structure is created (step 100). 104) and then send queue 502
Is inserted (step 106).
In the case of a reception request, a reception request data structure is created (step 130), and the reception request data structure is inserted into the reception queue 504 (step 132).

At this time, a transmission request number and a reception request number are added to each transmission request and reception request. However, the transmission request number and reception request number are initialized to the same value for each direction at both ends of the connection when the connection is established, and each request number is incremented for each transmission request and reception request and given to each request. Can be That is, the reception request number of the first transmission request issued on one computer on the connection has the same value as the transmission request number of the first transmission request issued on the other computer, and the second and third transmission requests have the same value. The same applies to the transmission request and reception request issued by the computers at both ends of the connection the same time, so the pair of the corresponding transmission request and reception request is determined on the connection, and data is exchanged between them. Become. Here, the request number is incremented for each transmission request and reception request, but may be incremented when each transmission request is completed or when a reception request is completed. In addition, since the request number cannot be increased without limit, an upper limit is set, and when the request number exceeds the upper limit, 0 is set.
Will be returned to Of course, this upper limit must be the same for transmission requests and reception requests.

In the case of a transmission request, the process waits until all transmission requests previously inserted in the transmission queue have completed transmission (step 108). When all transmission requests previously inserted in the transmission queue have completed transmission, transmission processing is performed. Is performed, and a timer is set (step 110). If the data passed at the time of the transmission request in the transmission processing is larger than the maximum transfer length (MTU), the data is divided into a plurality of packets and transmitted. After transmitting the transmission request data, if a NACK packet corresponding to the transmission request is received (step 112), a part of the transmission request data requested to be retransmitted by the NACK packet is retransmitted as a process for receiving the NACK (step 118). (Step 114). If a timeout has occurred (step 116), an ACK request packet is transmitted as a process at the time of timeout, and the timer is reset (step 118). AC for this transmission request
If a K packet has been received (step 120), the transmission request is extracted from the transmission queue (step 122).
Application or upper protocol module 40
2, 460 is notified of the completion of the transmission request. At this time, the reception length actually received by the receiving computer is also notified.

In the case of a reception request, it is checked whether or not transmission data has already arrived in response to the reception request (step 134). If it has been received, a NACK packet is transmitted to prompt retransmission (step 136). .
The received data packet receives the data at an appropriate position in the received data buffer according to the offset and the packet length of the packet header. A as network 430
If a packet that does not overtake the packet on the network, such as TM, is used, the next expected packet can be predicted. If a packet with data earlier than the prediction arrives, the packet is lost. (Step 138), so in such a case NA
By transmitting the CK packet, it is possible to request retransmission of the data that is considered to be lost (step 140). When a data packet or an ACK request is received, the corresponding reception request indicates that the reception request length and the last
It is checked whether or not all the data corresponding to the smaller of the transmission request length notified by setting the "ket Flag" has been received (steps 142 and 146). If the check confirms the completion of the reception request, A
The CK packet is transmitted to the transmitting side (step 15).
0), fetch the reception request from the reception queue (step 152), and notify the application or the upper protocol modules 402 and 462 of the completion of the reception request.
At this time, the reception length actually received by the receiving computer is also notified. If the reception request is not completed when the ACK request is received, a NACK is transmitted to the transmitting side to notify the unarrived data portion.

By sending an ACK only when it is confirmed that the reception request has been completed, useless ACK is omitted.

When the transmission request or the reception request is taken out of the transmission queue or the reception queue, the data structure is released (step 154).

The flow of the above-described processing will be described using a more specific example. In this example, a flow of processing for data transmission and reception between a pair of a transmission request and a reception request having a request number 8 is shown.

First, it is assumed that the transmission side transmits 3584 bytes of data. Assuming that the maximum transfer length (MTU) is 1024 bytes, the data passed at the time of the transmission request is larger than the maximum transfer length, so that the data is divided into four packets and transmitted one after another. The data packet in FIG. 5 shows the fourth data packet transmitted at this time. Here, the first, second, and third data packets have a packet length of 1024 bytes and a Last Packet Fla.
g becomes 0. Since the fourth data packet is the last packet, the remaining packet length of 512 bytes is the packet length, and the Last Packet Flag
Becomes 1. Fields such as a connection identifier and a request number take the same value in all four data packets.
Since the offset is the fourth packet, 3 UNIT
A minute offset is required.

Next, it is assumed that the receiving side also issues a receiving request with a receiving request length of 3584 bytes. The data packet transmitted from the transmission side identifies the reception request by the connection identifier 60 in the data packet header and the request number 8 on the connection, and furthermore, the appropriate position of the reception data buffer during the reception request by the offset and the packet length. The data is copied to For example, since the fourth data packet shown in FIG. 5 has an offset of 3, it is copied to the 512-byte position from the 3072th byte on the received data buffer. When all the data has been received, a reception confirmation packet is sent to the transmission side. The reception acknowledgment packet in FIG. 7 indicates a reception acknowledgment packet transmitted toward the transmitting side at this time. The processing can be completed when the receiving side receives all the data, and when the transmitting side receives the acknowledgment packet.

As an effect of the first embodiment, by performing transmission / reception control between a pair of a transmission request and a reception request, useless ACK when copying is performed on the transmission side can be omitted.
Further, at the time of asynchronous transmission / reception, transmission / reception requests can be completed irrespective of the request order, so that high-speed and efficient data transmission / reception with a low CPU usage rate can be achieved.

In order to guarantee reliable transmission and reception for the smaller request data length between a pair of transmission request and reception request having different request data lengths, for example, if the transmission request data length is not known in advance. Can be handled by making a reception request with a larger data length.

Next, a second embodiment will be described. An object of the second embodiment is, in addition to the object of the first embodiment, to enable high-speed and efficient data transmission / reception with a low CPU usage rate even in synchronous transmission / reception.

FIG. 9 is a flow chart showing the second embodiment, and FIG. 10 is a flow chart of the transmission / reception processing in which the processing flow relating to the temporary ACK in FIG. 9 is extracted. Also, FIG.
FIGS. 11 and 12 show a data structure, a data packet format, and a reception confirmation packet format for storing a transmission / reception request in the middle-level protocol module.

FIG. 5 shows the connection data structure as in the case of the first embodiment. However, in the case of synchronous transmission and reception,
In each transmission / reception queue, only one or less transmission requests during transmission and reception requests waiting for data can exist at the same time.

FIG. 11 shows a format in which a temporary ACK request Flag 1150 is added to the format of the data packet shown in FIG. The temporary ACK request Flag is a flag that is set when this data packet makes a temporary ACK request to the receiving side. As a specific value, it usually takes either 0 or 1.

FIG. 12 shows the format of a temporary ACK packet passed between the middle-level protocol modules 404 and 464 in FIG. The connection identifier 1200 is a data structure assigned to each connection when establishing a connection in the middle-level protocol modules 404 and 464, and the request number 1202 indicates which transmission request this temporary ACK packet is a temporary ACK for.
The reception request length 1204 indicates the reception data length specified in the reception request. The reception request length 1204 allows the transmission side to notify the application or the upper protocol modules 402 and 462 of the actually transmitted data length at the end of the transmission request even when the reception request length is shorter than the transmission request length.

A specific example of the temporary ACK packet format shown in FIG. 12 is shown below. Connection identifier 1200 is TC
Like the port numbers in P and UDP, numbers such as 60 are assigned. The request number 1202 is the temporary AC
It is a request number of a pair of a transmission request and a reception request for confirming reception of a portion of the transmission buffer that is not copied by the K packet, and a value such as 8 is assigned. The reception request length 1204 is the reception data length specified in the reception request, and is specified by a value such as 3584 bytes.

Next, the flowchart of FIG. 9 and the flowchart of FIG.
The operation of additional items in the case of synchronous transmission / reception will be described with reference to the diagram showing the flow of processing 0.

First, in step 1020, the application or the upper-layer protocol module 402
The transmission request 1 is transmitted from the medium-level protocol module 40
4, 464. The first half (the part that is not copied) of the transmission buffer in the transmission request 1 is divided by the maximum transfer length and sent out one after another. In step 1022, the temporary ACK request Flag 1150 in FIG. 11 is set to transmit the last packet of the part that is not copied. At the same time, in step 1024, the latter half of the transmission buffer is copied to a buffer in the middle-level protocol module, and subsequent transmission is performed from the buffer in the middle-level protocol module. When the receiving side receives a packet in which the temporary ACK request flag is set, it checks whether or not all the packets before that packet have already been received. Returns the packet to the sender. At this time, the reception length specified in the reception request is inserted into the reception request length 1204 of the temporary ACK packet. This processing corresponds to steps 980 and 982 in the flowchart of FIG. When the transmitting side receives this provisional ACK packet, it can be seen that all the portions not copied have been received, so that the buffer passed from the upper level protocol module becomes unnecessary. Therefore, in step 1028, the transmission end is notified to the application or the upper protocol modules 404 and 464. At this time, if the reception request length 1204 specified in the temporary ACK packet is smaller than the transmission request length, the reception request length 1204 is notified simultaneously as the data length to be actually transmitted and received. This processing corresponds to steps 970 and 972 in the flowchart of FIG. In step 1030, at this point, the application or higher-level protocol module 404, 464 sends the next transmission request 2 to the middle-level protocol module 404, 46.
4 In step 1052, the buffer in the middle-level protocol module on the transmitting side is released when the ACK packet for the corresponding transmission request is received.

As described above, in the case of synchronous transmission / reception, by copying only the latter half of the transmission buffer, the next transmission request can be made without waiting for ACK. Transmission and reception are possible.

The flow of the above-described processing will be described using a more specific example. In this example, a flow of processing for data transmission and reception between a pair of a transmission request and a reception request having a request number 8 is shown.

First, it is assumed that the transmission side transmits 3584 bytes of data. Assuming that the maximum transfer length (MTU) is 1024 bytes, the data passed at the time of the transmission request is larger than the maximum transfer length, so that the data is divided into four packets and transmitted one after another. The data packet in FIG. 11 shows the fourth data packet transmitted at this time. Where 1
For the second, third, and second data packets, the packet length is 1024 bytes, and the last packet Fl
ag becomes 0. Since the fourth data packet is the last packet, the remaining packet length of 512 bytes is the packet length, and the last packet flat
g becomes 1. Fields such as a connection identifier and a request number take the same value in all four data packets. The offset is the fourth packet, so 3UN
An offset for IT is required. Also, if the first and second data packets are not copied, but the third and fourth data packets are sent to the buffer in the middle-level protocol module, the temporary Ack in the second data packet is assumed. The request Flag becomes 1.

Next, it is assumed that a receiving request is also made on the receiving side with a receiving request length of 3584 bytes. The data packet transmitted from the transmission side identifies the reception request by the connection identifier 60 in the data packet header and the request number 8 on the connection, and furthermore, the appropriate position of the reception data buffer during the reception request by the offset and the packet length. The data is copied to For example, since the fourth data packet shown in FIG. 5 has an offset of 3, it is copied to the 512-byte position from the 3072th byte on the received data buffer. When the second data packet is received, the provisional Ack request Flag is 1, so that the reception of the 0th data packet is confirmed and the provisional Ack packet is transmitted to the transmitting side. The tentative Ack packet in FIG. 12 indicates a tentative Ack packet transmitted to the transmitting side at this time.

When the transmitting side receives the temporary Ack packet from the receiving side, it notifies the application or the upper protocol module of the end of transmission. At this point, the application or the upper protocol module can issue the next transmission request.

When all data is received on the receiving side, a reception confirmation packet is sent to the transmitting side. On the receiving side, the processing can be completed when all the data is received. In addition, the transmission side can release the buffer in the middle-level protocol module upon receiving the reception confirmation packet.

The effect of the second embodiment is that, in the case of synchronous transmission / reception, only the latter half of the transmission buffer is copied, so that AC which cannot be avoided in the case of copyless synchronous transmission.
The waiting time associated with K waiting can be reduced, and efficient data transmission / reception with high speed and low CPU utilization can be achieved.

Also, in the second embodiment, the first
As in the first embodiment, reliable transmission / reception is guaranteed for a smaller request data length between a pair of a transmission request and a reception request having different request data lengths.

[0068]

As described above, according to the present invention, by performing transmission / reception control between a pair of a transmission request and a reception request, it is possible to eliminate useless ACK when copying is performed on the transmission side. In asynchronous transmission / reception, transmission / reception requests can be completed irrespective of the order of requests.
Efficient data transmission / reception with a low usage rate becomes possible.

In addition, it is possible to guarantee reliable transmission and reception for a smaller request data length between a pair of a transmission request and a reception request having different request data lengths. Therefore, for example, even when the transmission request data length is not known in advance, it is possible to cope with the reception request with the assumed maximum transmission request data length.

Also, a format of a transmission / reception request in which data having higher importance is arranged closer to the head is determined in advance, and the reception side determines which priority data is to be acquired by adjusting the reception request length. By adjusting the transmission request length on the transmission side, it is also possible to determine up to which priority the data is to be transmitted, so that the data length according to the priority can be determined without previously determining the data length transmitted and received between the transmission and reception. Transmission and reception are possible. This makes it possible, for example, to change the sending length on the transmitting side according to the load of the CPU or network, and change the receiving length on the receiving side as needed by the receiver. Applicable.

Furthermore, in the case of synchronous transmission / reception, by copying only the latter half of the transmission buffer, it is possible to reduce the waiting time associated with ACK waiting which cannot be avoided when performing copyless synchronous transmission. Efficient data transmission / reception with a low CPU usage rate becomes possible.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a processing procedure according to a first embodiment of the present invention.

FIG. 2 is a diagram showing exchange of packets at the time of transmission and reception in a conventional example (TCP).

FIG. 3 is a diagram showing a relationship between a transmission / reception request and a byte stream at the time of asynchronous transmission / reception in a conventional example.

FIG. 4 is a system block diagram according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a data structure for storing a transmission / reception request according to the embodiment of this invention.

FIG. 6 is a diagram showing a data packet format according to the first embodiment of the present invention.

FIG. 7 is a diagram showing an acknowledgment packet format according to the embodiment of the present invention.

FIG. 8 is a diagram illustrating a middle-level protocol module according to the embodiment of this invention.

FIG. 9 is a flowchart illustrating a processing procedure according to the second embodiment of this invention.

FIG. 10 is a diagram illustrating a flow of processing related to temporary ACK according to the second embodiment of this invention.

FIG. 11 illustrates a data packet format according to the second embodiment of this invention.

FIG. 12 illustrates a temporary ACK packet format according to the second embodiment of this invention.

[Explanation of symbols]

600: connection identifier, 602: transmission request number, 604: offset position in the transmission request, 606: packet length, 608: flag indicating that the last data of the transmission request is included, 610: data, 700: Connection identifier, 702: Request number of request for confirmation of reception, 704: Length of actually received packet, 1100: Connection identifier, 1102: Number of transmission request, 1104: Offset position in transmission request, 1106: Packet 1108, a flag indicating that the last data of the transmission request is included, 1150, a flag indicating that a temporary ACK request is to be performed, 1200, a connection identifier, 1202, a request number of a request to be subjected to the temporary ACK, 1204 … The packet length specified in the reception request.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshihiro Takiyasu 890 Kashimada, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Information and Communication Development Division, Hitachi, Ltd.

Claims (15)

[Claims] The present invention comprises a transmitting terminal and a receiving terminal, a network for connecting the transmitting terminal and the receiving terminal, and a logical connection is established between the transmitting terminal and the receiving terminal. A communication method in a communication system for transferring data from the transmitting terminal to the receiving terminal through the network by issuing a reception request to the logical connection at the receiving terminal, An identifier for associating a reception request with the transmission request is added to the reception request and the transmission request, the reception request is associated with the transmission request, and the data is transferred from the transmission terminal to the reception terminal. A communication method, comprising: 2. The communication method according to claim 1, wherein the same identifier as the transmission request corresponding to the reception request is added to the reception request. 3. The communication method according to claim 1, wherein the same identifier as the reception request corresponding to the transmission request is added to the transmission request. 4. The data processing system according to claim 1, wherein the receiving side has a data structure indicating which part is received for each reception request,
A communication method characterized by using this data structure to determine the end of data reception between pairs having the same request number, and sending back an acknowledgment (ACK) at the end of the reception. 5. The method according to claim 1, wherein when data corresponding to the transmission request arrives before the reception request, the data is discarded, and the fact that the data has arrived is stored. A retransmission request (NACK) is returned to the transmission side when the transmission is performed, thereby immediately retransmitting the data. 6. A transmission packet according to claim 1, wherein a field indicating the last packet in the request is provided in the transmission packet, and the request data length of the transmission request is smaller than the request data length of the corresponding reception request. A communication method in which the end of transmission request data is notified to a receiving side using this field, and reliable communication is performed for data corresponding to the requested data length of the transmission request. 7. The communication method according to claim 6, wherein a transmission request data length is notified to a transmission request source and a reception request source at the end of transmission / reception. 8. A communication system according to claim 1, wherein when the requested data length of the transmission request is larger than the requested data length of the corresponding reception request, reliable communication is performed for the data of the reception request data length. Communication method. 9. The reception request data length at the end of transmission / reception by providing a field for entering the actually received data length in the ACK and notifying the transmission side of the data length actually transmitted by the field. Is notified to a transmission request source and a reception request source. 10. In the case of synchronous transmission and reception, in the case of synchronous transmission and reception, data of the latter half of the transmission buffer in the transmission request is copied and held in a buffer on the transmission terminal, and a temporary ACK request is made in the transmission packet. Field to indicate that
This field is set when sending the last packet of the part that is not copied, and when the receiving side receives a packet with the field indicating that a temporary ACK request is made, it has already received all packets before that packet If so, a temporary ACK is returned.
A communication method, wherein a next transmission request for a logical connection can be made at the time of reception, and a copy data holding buffer on the transmission terminal is released at the time of ACK reception. 11. A reception request data length according to claim 10, wherein a field for entering a data length specified in the reception request is provided in the temporary ACK, and the field informs the transmission side of the data length actually transmitted / received. Is notified to a transmission request source and a reception request source. 12. A transmitting terminal, comprising: a receiving terminal; and a network connecting the transmitting terminal and the receiving terminal.
Establish a logical connection between the sending terminal and the receiving terminal,
The transmission terminal issues a transmission request for the logical connection, and the reception terminal issues a reception request for the logical connection, thereby transferring data from the transmission terminal to the reception terminal via the network. In the communication method of the transmission terminal in the system, an identifier for associating the reception request with the transmission request is added to the transmission request, the reception request is associated with the transmission request, and the data is output to the reception terminal. A communication method comprising: 13. A transmitting terminal, comprising: a receiving terminal; and a network connecting the transmitting terminal and the receiving terminal.
Establish a logical connection between the sending terminal and the receiving terminal,
The transmission terminal issues a transmission request for the logical connection, and the reception terminal issues a reception request for the logical connection, thereby transferring data from the transmission terminal to the reception terminal via the network. In the communication method of the receiving terminal in the system, an identifier for associating the reception request with the transmission request is added to the reception request, the reception request is associated with the transmission request, and the data sent from the transmission terminal is A communication method characterized by receiving. 14. A network comprising: a transmitting terminal; a receiving terminal; and a network connecting the transmitting terminal and the receiving terminal.
Establish a logical connection between the sending terminal and the receiving terminal,
The transmission terminal issues a transmission request for the logical connection, and the reception terminal issues a reception request for the logical connection, thereby transferring data from the transmission terminal to the reception terminal via the network. In a storage medium storing a communication program of the transmission terminal in a system, the communication program adds an identifier for associating the reception request with the transmission request to the transmission request, and associates the reception request with the transmission request. A storage medium storing a communication program for outputting the data to a receiving terminal. 15. A transmission terminal, comprising: a receiving terminal; and a network connecting the transmitting terminal and the receiving terminal.
Establish a logical connection between the sending terminal and the receiving terminal,
The transmission terminal issues a transmission request for the logical connection, and the reception terminal issues a reception request for the logical connection, thereby transferring data from the transmission terminal to the reception terminal via the network. In a storage medium storing a communication program of the receiving terminal in a system, the communication program adds an identifier for associating the reception request with the transmission request to the reception request, and associates the reception request with the transmission request. And a storage medium storing a communication program for receiving the data transmitted from the transmission terminal.