JPH06132981A - Packet transmission system - Google Patents

Abstract

PURPOSE:To transmit the latest confirmation response packet and to decrease the number of the confirmation response packets to be transmitted by updating the information of the confirmation response packet when the confirmation response packet is not transmitted. CONSTITUTION:Whether or not the update of an AK packet previously transmitted on a transport connection is valid is checked by a transport processing part 40. That is, whether or not the pointer of a transmission buffer 50 is registered in the connection corresponding part of an AK packet managing part 10 is checked, and whether or not the already set AK packet is transmitted to a network transmission path is checked by flags 54 and 55 provided at a buffer management area 51. Then, whether or not a transmission end flag 54 is turned off is checked before and after an update flat 55 is set, and when the AK packet is not transmitted, and the update is valid, the change of the sequence number, credit value and header length of the AK packet, and the addition to an option part are operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet transmission system in communication protocol processing, and more particularly to a transmission system of an acknowledgment packet containing a sequence number and window information to be transmitted after receiving a data packet.

[0002]

2. Description of the Related Art In communication protocol processing, in order to guarantee highly reliable communication, when a data packet is received as a part of error control, an acknowledgment packet is sent to report to the sender that data has been correctly received. Send it back. This confirmation response packet includes a sequence number and window information for preventing overflow of the reception buffer. By receiving the confirmation response packet, the transmission side can recognize the sequence number of the data packet to be transmitted next and the number of data packets that can be transmitted continuously. At the same time, it is necessary to stop the retransmission timer activated in preparation for the loss of the transmitted data packet and to discard the data packet held for retransmission.

For example, in the transport layer class 4 of the layered communication protocol of OSI, which is being internationally standardized by ISO, an AK packet is used as an acknowledgment packet. The AK packet includes the sequence number of the data packet desired to be received next and the credit value (the number of data packets that can be continuously transmitted on the transmitting side regardless of whether or not the AK packet is received) on the window side. Unless the data packet is lost or the window size is not changed, only the sequence number of the information set in the AK packet needs to be updated. If the window size changes, the credit value must change. To decrease the credit value, the subsequence number is added to the option part in addition to the change of the credit value. The sub-sequence number is provided so that the receiving side of the AK packet can receive the AK packet in the order sent by the transmitting side.

The timing at which the AK packet is transmitted is not specified by the protocol and is left to the implementation. Basically, it can be divided into the following two types. (1) Each time one data packet is received, an AK packet is returned to confirm reception (1DT1AK) (2) Reception confirmation of a plurality of data packets is performed by one AK packet (nDT1AK) Normally, an AK packet to be returned It is said that the smaller the number, the better the performance. As a method of realizing nDT1AK, there is a method of returning an AK packet when a data packet with a window upper limit is received, or a method of returning an AK packet in message units (at the time when all divided data packets are received).

On the other hand, the AK packet transmission process has the same procedure as the data packet transmission. In the layered communication protocol, a processing unit is generally provided for each layer. When the data packet is received and the AK packet is returned by the transport processing unit, a transmission buffer is acquired, and information such as a sequence number and a credit value is set in the acquired transmission buffer to create an AK header. After creating, send the transmission buffer to the network processing unit and request transmission. Hereinafter, in each processing unit, a network header, LLC header, MA
The C header is sequentially created, and the AK packet is sent to the transmission path.

A method of transmitting such an acknowledgment packet and its performance are described in, for example, B-590: IEICE Spring National Convention (1991).

[0007]

However, according to the conventional acknowledgment packet transmission method, when an acknowledgment packet is transmitted for each data packet, data packets are transmitted from the same source by file transfer or the like. When the data packets are continuously transmitted, a request for transmitting a plurality of confirmation response packets is continuously generated on the data packet receiving side. The processing overhead increases due to the acknowledgment packet creation on the receiving side and the acknowledgment packet analysis on the transmitting side.

In the layered communication protocol, since a processing unit is provided for each layer, when a packet is requested from the transport layer to the network layer, the packet is not immediately sent to the network transmission line. . Therefore, in the transport layer, when the confirmation response packets are continuously returned to the same data transmission source, there is a possibility that a plurality of confirmation response packets may exist in the processing unit lower than the transport layer.

On the other hand, in the method of transmitting one acknowledgment packet for a plurality of data packets, it is realized by transmitting the acknowledgment packet at the time when the data packet with the window upper limit is received or in message units. In this case, if the time until the acknowledgment packet is transmitted is long, the data packet is retransmitted due to the timeout of the retransmission timer on the transmission side. In order to prevent this retransmission, a timer is required to monitor the retransmission timer interval on the transmission side and the transmission interval of the acknowledgment packet. Generally, in communication protocol processing, the overhead due to the timer processing is large, and the performance of the communication protocol processing deteriorates.

An object of the present invention is to reduce the number of confirmation response packets to be transmitted in response to consecutive transmission requests for confirmation response packets without using a timer in the method of transmitting confirmation response packets. Create acknowledgment packet /
It is to reduce the processing overhead of analysis and realize highly efficient communication protocol processing.

[0011]

In order to achieve the above object, according to the acknowledgment packet transmitting method of the present invention, in the protocol processing unit for transmitting the acknowledgment packet, the pointer of the transmission buffer in which the acknowledgment packet is created is set to the destination. Stored for each of the above, the means for indicating whether or not the confirmation response packet has already been transmitted to the network transmission line, the means for indicating that the sequence number and window information in the confirmation response packet are being updated, and For example, when a data packet is received and an acknowledgment packet is sent by having a means for waiting for the above packet to be sent to the network transmission line, the acknowledgment packet requested to be sent to the lower layer protocol processing unit Check whether it has been sent to the transmission path, and if it has not been sent yet, send it to the lower layer. By updating the information of the acknowledgment packet is set to file, it sends the latest acknowledgment packet, is characterized in reducing the number of acknowledgment packets to be transmitted.

The storage of the transmission buffer in which the confirmation response packet is created can be realized by, for example, a management table that manages the pointer of the transmission buffer for each destination.

As a structure of the transmission buffer for creating the acknowledgment packet, for example, a flag is provided in the transmission buffer,
Whether the confirmation response packet set in the transmission buffer is being updated by setting / resetting the above flags when updating the contents of the transmission buffer and when transmitting the confirmation response packet to the network transmission line, It is possible to know whether it has been sent.

Further, in the acknowledgment packet transmitting method of the present invention, when the acknowledgment packet is transmitted, if the acknowledgment packet requested to be transmitted to the lower layer before the acknowledgment packet can be updated, it is set in the transmission buffer. The information of the acknowledgment packet in the send buffer is not provided for updating the information of the acknowledged packet that has been stored, but an area for storing the latest information of the acknowledged packet is provided separately and the information is sent to the network transmission line. May be carried out by providing a means for determining whether to update the information and a means for changing the information of the confirmation response packet in the transmission buffer to the information set in the area when the update is necessary.

[0015]

According to the present invention, the address of the transmission buffer in which the acknowledgment packet is created is managed for each destination, and when the acknowledgment packet is transmitted next, the acknowledgment packet has already been sent to the network transmission line. Determine if there is,
If it has not been sent, by having a means to update the information of the acknowledgment packet, even if the acknowledgment packets are continuously transmitted, the number of acknowledgment packet transmissions is reduced without adding timer processing. This makes it possible to reduce the overhead of transmission / reception processing by the confirmation response packet.

[0016]

(Embodiment 1) A first embodiment of the present invention will be described with reference to FIGS.

FIG. 2 shows an example of the configuration of a data communication system embodying the present invention. This system is composed of a plurality of computers 20 (20A to 20C), and each computer is connected to a network transmission line 22 via a communication control device 21 (21A to 21C).

FIG. 3 is a block diagram showing details of the computer 20 and the communication control device 21. The computer 20 is composed of a main processor 30 and a main memory 31, and is connected to a communication control device 21 via a computer system bus 32. The communication control device 21 includes two processors, an interface processor 34 that controls the interface processing with the computer 20 and the network transmission path 22, and a protocol processing processor 35 that executes communication protocol processing, a buffer memory 37, and a local processor. It comprises a memory 39, a direct memory access controller (DMAC) 36, a MAC-LSI 38 connected to the network transmission line 22, and a local bus 42 connecting these, and a computer system bus 32 and a local bus 42. A system bus interface 33 is provided between them. A bus arbiter 40 is provided on the local bus 42 and a 2-port control circuit 44 is provided to control access to the buffer memory in order to avoid contention of the local bus 42 by the plurality of processors 34, 35 or the DMAC 36. There is.

FIG. 4 is an explanatory diagram showing an example of the structure of the hierarchical communication protocol processed by the computer 20 and the communication control device 21 shown in FIG. From the bottom, physical layer, MA
The C layer, the LLC layer 42, the network layer 41, the transport layer 40, the session layer, the presentation layer, and the application layer, and the communication protocol processing executed by the communication control device 21 is the transport layer 40 or lower. In the following embodiment, the transport layer 40 has ISO
Assuming that 8073 is applied, a method of transmitting an AK packet which is an acknowledgment packet in transport class 4 will be described.

FIG. 5 is an explanatory diagram showing the structure of the transmission buffer 50 for creating an AK packet and the structure of the AK packet. The transmission buffer 50 is arranged in a plurality of planes on the buffer memory 37 and is composed of two areas, a buffer management area 51 and a packet area 52. The buffer management area 51 includes an AK flag 53 for distinguishing an AK packet from other packets, a transmitted flag 54 and an updating flag 55 provided for applying the present invention, and a size of a packet set in the packet area. Data length 56,
It is composed of a pointer 57 indicating the beginning of the packet. The AK header 61 of the transport class 4 is stored in the packet area 52 before being sent to the network transmission line 23.
Network header 60, LLC header 59, MAC
A header 58 is added to create an AK packet. The AK header 61 includes a packet length 62, an AK code 63, a destination reference 64, a sequence number 65, a credit value 66, and an option section 67.

FIG. 1 is a diagram showing a processing configuration in the communication control device 21 and a management method of the transmission buffer 50 in which an AK packet is created. The processing executed by the communication control device 21 includes a processing unit executed by the protocol processing processor 35 and a processing unit executed by the interface processor 34. The former is the transport processing unit 40, the network processing unit 41, and the LLC. It is divided into a processing unit 42. The latter is a computer interface processing unit 12 and a MAC.
-It consists of the LSI driver unit 13. In addition to these processing units, the AK packet management unit 10 accessed by the transport processing unit 40 is provided, and here, the pointer of the transmission buffer 50 that created the AK packet is managed for each transport connection. Further, in the MAC-LSI driver unit 13, when the MAC-LSI 38 has already started transmission, the transmission buffer 50 is registered in the transmission waiting pool 11 and the transmission buffer 50 is saved. The AK packet management unit 10 and the transmission waiting pool 11 are arranged on the local memory 39. In FIG. 1, the AK packet management unit 1
The transmission buffer 50 in which the AK packet managed to 0 is set is shown in the state of being registered in the transmission waiting pool 12.

Upon receiving the data packet, the MAC-LSI 38 writes the received data packet in the reception buffer area on the buffer memory 37, and the MAC-LSI 38
The driver processing unit 13 is notified of the reception. MAC-LSI
The data packet is delivered from the driver processing unit 13 to the LLC processing unit 42, and from the LLC processing unit 42 to the network processing unit 41 and the transport processing unit 40.

Hereinafter, the transport processing unit 40 and the MAC
-The AK packet transmission procedure in the LSI driver unit 13 will be described with reference to FIGS.
The packet transmission method will be described in detail.

FIG. 6 is a flowchart of the data packet receiving process in the transport processing section 40. When a data packet is passed from the lower network processing unit 41, header analysis is performed (100), and if there is no problem after analysis, the received data is passed to the computer interface unit (110) and then AK packet transmission processing is executed. Yes (120).

FIG. 7 is a flowchart of the AK packet transmission processing 120 in the transport processing section 40. In the AK packet transmission processing 120, it is first checked whether the AK packet transmitted last time on the transport connection can be updated. Specifically, the transmission buffer 50 is provided in the connection corresponding portion of the AK packet management unit 10.
It is checked whether the pointer of is registered (200), and the buffer management area 51 of the registered transmission buffer 50 is checked.
It is checked from the flags 54 and 55 provided in 1) whether the AK packet already set in the transmission buffer 50 has been sent to the network transmission line. Protocol processing processor 35 and interface processor 3
In order to perform exclusive control between the four, before and after the updating flag 55 is set, it is checked whether or not the transmitted flag 54 is in the off state (210, 220, 230). As a result of the above determination, if the AK packet has not yet been transmitted and can be updated, the sequence number 65 (240) of the AK packet, and if update is necessary, the credit value 66 is changed and the option section 67 is added. , The header length 62 is changed (280,
290, 300). After the change is completed, the updating flag 55 is turned off (260).

When the transmitted flag 54 is on, the AK packet transmitted last time has already been transmitted to the network transmission line 22, so the transmission buffer 50 is newly acquired and the AK packet is created (270, 310). ). When the transmission buffer 50 is not registered in the AK packet management unit 10 (when the AK packet is first transmitted after setting the connection), the AK packet is similarly created (310).

FIG. 8 shows a flowchart of the AK packet creation process 310. In the AK packet creation 310, the empty transmission buffer 50 is acquired (400), and the header length 62, the AK code 63, the destination reference 64, the sequence number 65, and the credit value 66 are set (41).
0, 420, 430, 440, 550). If the option section 67 needs to be set, the option section 6
7 is set (460). The data length 56 and the pointer 57 in the buffer management area 51 of the transmission buffer 50 are set (470), and the AK flag is turned on to indicate that the AK packet has been set (480). In order to update the information of the AK packet before the created AK packet is sent to the network transmission line 22,
The transmission buffer 50 is registered in the area corresponding to the transport connection of the AK packet management unit 10 (49
0). Hereinafter, the network processing unit 41 and the LLC processing unit 4
The transmission buffer is delivered in order of 2 and each header is added before the AK header (500, 510). Then, the transmission buffer 50 is sent to the MAC-LSI driver unit 13.
To request the transmission of the AK packet (520).

FIG. 9 is a flowchart showing the transmission processing of the MAC-LSI driver section 13. MAC-LSI
In the transmission process of the driver unit 13, it is determined whether the MAC-LSI 38 is in the transmission starting state (600). If not activated, a transmission request can be issued to the MAC-LSI 38. In this case, if the AK flag 53 in the buffer management area 51 of the transmission buffer 50 is off, the packet set in the transmission buffer 50 is not an AK packet, so a MAC header 58 is added (660) and MAC-
Preparation for starting up the LSI 38 (670), MAC-L
The SI 38 is activated (680). When the AK flag 53 is on, after confirming that the information of the AK packet is not being updated (640, 650), the MAC header 58 is created, the MAC-LSI 38 is ready to start, and the MAC-LSI 38 is.
Is activated (660, 670, 680). This confirmation is performed by turning on the sent flag 54, checking the updating flag 55, and if the updating flag 54 is on, waiting until it is turned off (640, 650).

When the transmission request cannot be issued to the MAC-LSI 38, the MAC header 5 is stored in the transmission buffer 50.
After creating 8 and updating the data length 56 and pointer 57 of the buffer management area 51, the transmission buffer 50 is registered in the transmission waiting pool 11 (610, 620). Regarding the transmission buffer 50 registered in the transmission waiting pool 11, M
The transmission is requested when the transmission in the AC-LSI 38 is completed.

FIG. 10 shows the MAC-LSI driver unit 13
5 is a flowchart of a transmission completion process in FIG. In the transmission completion processing, the transmission buffer 50 that has requested the transmission to the MAC-LSI 38 is released (700), and if there is the transmission buffer 50 registered in the transmission waiting pool 11 (71
0), issue a transmission request to the MAC-LSI 38. In this case, as in the transmission process, A in the transmission buffer 50
If the K flag 53 is on, after confirming that the information in the AK header 61 is not being updated, the MAC-LSI 38
Issue a transmission request to (720, 730, 64
0,650,670,680).

In this way, the transport processing unit 4
In the AK packet transmission process of 0, by storing the pointer of the transmission buffer 50 that created the AK packet and providing the updating flag 55 and the transmission completed flag 54 in the transmission buffer, the lower layer is transmitted to the lower layer when the AK packet is transmitted. If the AK packet requested to be transmitted previously is not transmitted to the network transmission path 22, the sequence number 65 and the credit value 66 set in the AK packet can be updated, so that the data packets can be continuously transmitted. The number of AK packet transmissions can be reduced when the packet is received.

(Embodiment 2) A second embodiment of the present invention is shown in FIG.
It will be described with reference to FIGS.

FIG. 11 is an explanatory diagram showing the structure of an area provided for each transport connection in the AK packet management unit 10 for realizing the second embodiment. A pointer 7 for storing a transmission flag 70, a request command 71, and a transmission buffer 50 necessary for applying the present invention
2 and AK information area 73. The AK information area 73 includes information set in the AK header 61, header length 62, AK code 63, destination reference 64, sequence number 65, credit value 66, and option section 6.
It consists of 7. When only the sequence number 65 is changed, it is not necessary to set all the items in the AK information area 73, and only the sequence number 65 may be set.

FIG. 12 is an explanatory diagram showing the structure of the transmission buffer 50. The transmission buffer 50 is composed of two areas, a buffer management area 51 and a packet area 52, as in the first embodiment. The buffer management area 51 includes an AK flag 53 indicating that the transmission buffer is used for an AK packet, a connection identifier 74 for identifying a connection for transmitting the AK packet, and a packet area 52.
It is composed of a data length 56 and a pointer 57 which indicate the size of the packet and the start address set in step 1.

AK packet management unit 10 and transmission buffer 5
13 and 1 show an AK packet transmission method realized by 0.
This will be described with reference to FIGS.

FIG. 13 is a flow chart of AK packet transmission processing. In the AK packet transmission process in the transport processing unit 40, it is determined whether the transmission buffer 50 is already registered in the area corresponding to the transport connection of the AK packet management unit 10 (800).
If it is registered, and the transmission flag 70 in the same area is in the on state (810), the registered transmission buffer 50 has already been requested to transmit to the lower layer, but is still sent to the network transmission path. Not in a state. Therefore,
Create the AK header 61 in the AK information area 73 (85
0), the update of the AK information area 73 is displayed in the request command 71 (860). When updating only the sequence number 65, only the sequence number 65 is set in the AK information area 73 (830), and the update of the sequence number 65 is displayed in the request command 71 (840).

When the transmission flag 70 is off, the AK header 61 portion of the transmission buffer 50 is updated, and the data length 56 and the pointer 57 of the buffer management area 51 are corrected if necessary (880, 890). After the transmission flag 70 is turned on (900), since the lower layer header has already been set in the transmission buffer 50, the direct MAC-LS is set.
The transmission is requested to the I driver unit 13 (910).

When the transmission buffer 50 is not registered in the AK packet management unit 10 (when the first AK packet is transmitted after setting the connection), the transmission buffer 50 must be acquired and an AK packet must be created (87).
0).

FIG. 14 is a flowchart of the AK packet creation processing 870. To create an AK packet,
The transmission buffer 50 is acquired (400), and the AK header 61 is acquired.
Are sequentially created (410, 420, 430, 440, 4
50,460). After the setting, the data length 56 of the buffer management area 51 of the transmission buffer 50, the pointer 57 are set (470), the AK flag 53 is turned on (480), and the connection identifier 74 is set (920). The transmission buffer 50 is registered in the AK packet management unit 10 (49
0), the transmitting flag 70 is turned on (930). After that, the processing is handed over to the lower layer, and the network header 60,
The LLC header 59 is created and the transmission is requested to the MAC-LSI driver unit 13 (500, 510, 520).

FIG. 15 shows the MAC-LSI driver unit 13
5 is a flowchart of the transmission process of FIG. In the transmission process of the MAC-LSI driver unit 13, it is determined whether the MAC-LSI 38 can be activated for transmission (600). If not, the transmission buffer 50 is registered in the transmission waiting pool 11 (970). If the AK flag 53 of the buffer management area 51 of the transmission buffer 50 is on (940), AK
Since it is a packet transmission request, the buffer management area 5
1 connection identifier 74 to AK packet management unit 1
0 is searched and it is determined by the request command 71 whether update is necessary (945). If the update is not necessary, the AK packet set in the transmission buffer 50 is sent to the network transmission line, but if necessary, writing to the AK information area 73 is prohibited (950) and the request command 7 is issued.
As shown in 1, the value set in the AK information area 73 is set to the entire AK header 61 in the transmission buffer or only the sequence number 65 (95).
5). After updating, cancel the write disable interrupt (96
0), clear the request command 71 (965), MAC
The header 58 is created (660), the MAC-LSI 38 is prepared for activation (670), the MAC-LSI 38 is activated, and the AK packet is sent to the network transmission line 22 (680).

As described above, the AK packet management unit 10 supports the transmission buffer 5 for the transport connection.
A transmission flag 70 that holds 0 and indicates that a transmission request has been requested to the lower layer, a request command 71 that indicates an AK packet transmission request that has occurred thereafter, and a new AK
By providing the AK information area 73 for storing the header information on the local memory 39 separately from the buffer memory 37, the information of the AK packet is updated by one access to the buffer memory and the number of AK packets to be transmitted is reduced. You can

[0042]

According to the present invention, the information such as the sequence number set in the acknowledgment packet can be updated until the acknowledgment packet is finally sent out on the network transmission line. Acknowledgment packets can be transmitted, and the number of acknowledgment packets to be transmitted can be reduced when data packets are continuously received.

[Brief description of drawings]

FIG. 1 is a block diagram showing a processing configuration in a communication control device according to the present invention and a management method of a transmission buffer storing an AK packet.

FIG. 2 is a block diagram of a data communication system to which the present invention is applied.

FIG. 3 is a block diagram of a communication control device to which the present invention is applied.

FIG. 4 is an explanatory diagram showing a configuration example of a layered communication protocol.

FIG. 5 is an explanatory diagram showing a configuration of a transmission buffer according to the first embodiment of the present invention.

FIG. 6 is a flowchart showing a data packet receiving process in the transport processing unit of FIG. 1 in the first embodiment of the present invention.

7 is a flowchart showing details of AK packet transmission processing in FIG.

8 is a flowchart showing details of AK packet creation processing in FIG.

FIG. 9 shows the MAC- of FIG. 1 in the first embodiment of the present invention.
6 is a flowchart showing a transmission process in the LSI driver unit.

FIG. 10 is the MAC of FIG. 1 in the first embodiment of the present invention.
-A flowchart showing a transmission completion process in the LSI driver unit.

FIG. 11 is an explanatory diagram showing a detailed structure of an area for each transport connection of the AK packet management unit in the second embodiment of the present invention.

FIG. 12 is an explanatory diagram showing the configuration of a transmission buffer according to the second embodiment of the present invention.

FIG. 13 is a flowchart of AK packet transmission processing in the transport processing unit of FIG. 1 according to the second embodiment of the present invention.

14 is a flowchart showing details of AK header creation processing in FIG.

FIG. 15 shows the MAC of FIG. 1 in the second embodiment of the present invention.
-Flow chart of transmission processing in the LSI driver unit.

[Explanation of symbols]

10 ... AK packet management unit, 11 ... Transmission waiting pool, 1
3 ... MAC-LSI driver unit, 20A, 20B, 20
C ... Computer, 38 ... MAC-LSI, 40 ... Transport processing unit, 50 ... Transmission buffer, 51 ... Buffer management area, 53 ... AK flag, 54 ... Sent flag, 55
… Update flag.

Claims (3)

[Claims] 1. In a method of returning an acknowledgment packet for received data, a means for storing a transmission buffer in which the acknowledgment packet is created for each destination, and whether the acknowledgment packet is transmitted to a network transmission line. A means to determine if and if not sent,
By having means for updating the information of the acknowledgment packet and means for waiting for transmission to the network transmission line during updating, when the acknowledgment packet is transmitted, it is already transmitted to the lower layer protocol processing unit. Request, but if there is the above-mentioned acknowledgment packet that has not yet been sent to the above-mentioned network transmission line, the information set in the above-mentioned acknowledgment packet is updated to the latest value to reduce the number of acknowledgment packet to be transmitted. A packet transmission method characterized by: 2. The method according to claim 1, wherein the protocol processing unit that returns the confirmation response packet manages the pointer of the transmission buffer of the confirmation response packet for each destination, and the information of the confirmation response packet is being updated. A flag indicating that there is a packet and a flag indicating that the confirmation response packet has been transmitted to the network transmission path are provided for each of the transmission buffers, and the two flags are set / set.
By performing a reset, it is determined whether the confirmation response packet set in the transmission buffer is being updated or has been transmitted to the network transmission line, and the confirmation response packet that always has the latest information. A packet transmission method for transmitting. 3. A means for determining whether or not the confirmation response packet requested to be transmitted to the lower layer protocol processing unit is transmitted to the network transmission line, and not transmitting the confirmation response packet. A means for storing the latest information of the acknowledgment packet, a means for updating the stored information, and a judgment as to whether or not the information needs to be changed when the acknowledgment packet is sent to the network transmission line. And a means for sending to the network transmission line after changing the information of the confirmation response packet to the latest stored information when there is a need to change the confirmation response. A packet transmission method that reduces the number of packets.